1.

Key Term Definition / Description

1. 5' to 3' direction the only direction that DNA polymerase can
synthesize DNA; it does so by adding nucleotides to the 3' end of a
DNA strand.
2. 70S the size of prokaryotic ribosomes.
3. 80S the size of eukaryotic ribosomes.
4. Abiotic factors the non-living physical and chemical attributes of a
system, for example light or temperature in an environment.
5. Absorptionthe movement of a substance, such as a liquid or solute,
across a cell membrane by means of diffusion, osmosis, or active
transport.
6. Absorption spectrum range of wavelengths of light that a pigment is
able to absorb.
7. Acetylcholine a molecule released by neurons at the neuromuscular
junction that causes muscle contraction.
8. Acrosome reaction a necessary and irreversible step in fertilization,
which is triggered by sperm receptor, in which the sperm’s and ovum’s
membranes fuse and the sperm penetrates the zona pellucida.
9. Actin a protein that forms (together with myosin) the contractile
filaments of muscle cells, and is also involved in motion in other types
of cell.
10. Action potential a localized change in electrical potential, from about -
70 mV to +30 mV and back again, that occurs across a nerve fibre
during transmission of a nerve impulse.
11. Action spectrumrange of wavelengths of light within which
photosynthesis takes place.
12. Activation energy the initial input of energy that is required to
trigger a chemical reaction.
13. Active site the specific portion of an enzyme that attaches to the
substrate.
14. Active site the location on the enzyme where the substrate binds.
15. Active transport movement of substances across membranes using
energy in the form of ATP.
16. Active transport a transport mechanism where ions or molecules move
against a concentration gradient, this movement requires energy.
17. Adaptations a feature of an organism that favours its survival to
reproductive age. Adaptations can be behavioural, physiological, or
structural.
18. Adaptive radiation the diversification of several new species from a
 recent ancestral source, each adapted to utilize or occupy a vacant
adaptive zone.
19. Adenine an organic base found in DNA and RNA in which it pairs with
thymine (or uracil).
20. Adenosine triphosphate (ATP) a nucleotide that releases energy
when its phosphate bonds are hydrolysed.
21. Adhesion the force by which individual molecules cling to surrounding
material and surfaces.
22. Adhesive property the joining of two different substances due to
attractive forces that hold them, such as keeping the water drops on
the surfaces of leaves.
23. Adipose tissue a type of connective tissue that contains stored
cellular fat.
24. Aerobic cell respiration respiration requiring oxygen, involving the
oxidation of glucose to carbon dioxide and water.
25. Aerobic respiration a type of respiration where oxygen is consumed.
26. Aerosol a collection of tiny solid or liquid particles in the
atmosphere that can come from natural sources (such as wildfires) or
people’s activities (such as burning fossil fuels). Some aerosols make
the atmosphere warmer because they absorb energy. Others have a
cooling effect because they reflect sunlight back into space.
27. Age structure The distribution of a population's individuals among
various age groups.
28. AIDS (Acquired immunodeficiency syndrome) the name of the
active HIV infection characterized by the reduction of T-cells and the
appearance of characteristic secondary infections.
29. Albumin the main protein of human plasma. Its main function is to
regulate the osmotic pressure of blood.
30. Algal bloom A dense spread of algae on the surface of water
caused by a rapid population growth.
31. Alien species A species living outside its native distributional range
or ecosystem.
32. Allele one of the possible alternatives of a gene, occupying a
specific position on a chromosome, that controls the same trait.
33. Allele one of the possible alternatives of a gene, occupying a
specific position on a chromosome, that controls the same trait.
34. Allele one of the possible alternative of a gene, occupying a
specific position on a chromosome, that controls the same trait.
35. Allele one of the possible alternatives of a gene, occupying a
specific position on a chromosome, that controls the same trait.
36. allele exchange During crossing over, the switch of alleles for the
same genes.
37. Allele mask when one allele covers the phenotypic expression of
another allele at the same gene locus.
38. allelic frequency The percentage of all alleles at a given locus in a
population gene pool represented by a particular allele.
39. Allergen any substance, often a protein, that induces an allergy:
common allergens include pollen, grasses, dust, and some
medications.
40. Allium The genus of monocotyledonous flowering plants that
includes the onion, garlic, chives, scallion, shallot, and the leek as well
as hundreds of wild species.
41. Allosteric inhibitor a molecule that binds at a site away from the
active site triggering a conformational change that prevents the
binding of substrate.
42. Alpha cells (α-cells) endocrine cells in the pancreas that synthesize
and secrete glucagon, which elevates the glucose levels in the blood.
43. Alpha helix a coiled conformation common in many proteins; it is
characterized by a spiral chain of amino acids stabilized by hydrogen
bonds in which the resulting structure resembles a spring or helix.
44. Alveolus (plural alveoli) air sac that constitutes the gas exchange
surface of the lungs.
45. Amino acid building block of proteins that consists of a basic
amino group (NH2), an acidic carboxylic group (COOH), a hydrogen
atom (-H), and an organic side group (-R) attached to the carbon atom.
46. Amino acid building block of proteins consisting of a basic amino
group (NH2), an acidic carboxylic group (COOH), a hydrogen atom (-H),
and an organic side group (R) attached to the carbon atom.
47. Amino acids building block of proteins consisting of the basic
amino group (NH2), the acidic carboxylic group (COOH), a hydrogen
atom (-H), and an organic side group (R) attached to the carbon atom.
48. Amino group NH2
49. Amniocentesis a procedure used to diagnose genetic defects in the
early stages of pregnancy; it involves collecting amniotic fluid using a
needle and syringe.
50. Amphipathic molecule that has hydrophobic and hydrophilic
regions.
51. Amylase an enzyme, found mainly in saliva and pancreatic fluid, that
converts starch and glycogen into simple sugars.
52. Amylopectin a soluble polysaccharide and highly-branched polymer
 of glucose found in plants as one of the two components of starch (the
other being amylose).
53. Amylose a polysaccharide found in plants as one of the two
components of starch (making up approximately 20-30% of the
structure).
54. Anabolism the synthesis of complex molecules from simpler
molecules, including the formation of macromolecules from monomers
by condensation reactions.
55. Anaerobic cell respiration respiration in the absence of oxygen,
involving the formation of lactic acid or ethanol.
56. Anaerobic organisms occur in the absence of oxygen or do not require
oxygen to live. For example, anaerobic bacteria produce energy from
food molecules without the presence of oxygen.
57. Analogous trait structures which are similar because of convergent
evolution.
58. Anaphase the stage of mitosis and meiosis in which the chromosomes
move to opposite ends of the nuclear spindle.
59. Antagonistic muscle a muscle that opposes the action of another.
60. Antagonistic muscle a muscle that opposes the action of another; for
example, the biceps and triceps are antagonistic muscles.
61. Antibiotic a chemical produced by microbes to kill off competing
microbes.
62. Antibiotic a chemical that kills or inhibits growth of bacteria by
deregulation of metabolic pathways.
63. Antibody an antigen-binding protein produced by B-cells.
64. Antibody a Y-shaped protein on the surface of B-cells that is secreted
into the blood or lymph in response to an antigenic stimulus, such as a
bacterium or virus.
65. Anticodon three consecutive bases on tRNA that are complementary
to a codon on mRNA.
66. Antidiuretic hormone (ADH) a hormone released by the pituitary
gland that controls the permeability of the walls of the collecting duct
in the kidney, preventing the production of dilute urine.
67. Aorta the main artery of circulatory system that carries blood
from the left side of the heart to the arteries of all limbs and organs
except the lungs.
68. Archaea a domain of prokaryotes.
69. Archaeans one of the prokaryotic domains of life. They tend to live in
extreme environments, they have RNA polymerases and ribosomes
that are closer to eukaryotes.
70. Arteriole a small terminal branch of an artery that connects with a
capillary.
71. Artery a vessel that carries blood away from the heart to organs
through the body.
72. Artificial selection the human intervention in animal or plant
reproduction to ensure that certain desirable traits are represented in
successive generations.
73. ATP a nucleotide triphosphate that is a common source of energy in
cells.
74. ATP (adenosine triphosphate) The energy molecule.
75. ATP synthase an enzyme that utilizes the H+ electrochemical
gradient to synthesize ATP.
76. Atrium (plural atria) a chamber that receives blood returning to the
heart.
77. Autoradiographytechnique that relies on the emission of radioactive
particles from within the subject to produce an image.
78. Autosomal genes chromosomes that do not determine sex.
79. Autosomes chromosomes that do not determine sex.
80. Autotroph an organism that uses solar energy or chemical energy to
manufacture the organic compounds it needs as nutrients from simple
inorganic compounds obtained from its environment.
81. Autotroph (or producer) an organism that is able to form nutritional
organic substances from simple inorganic substances such as carbon
dioxide.
82. Autotrophs organismsthat use solar energy or chemical energy to
manufacture the organic compounds they need as nutrients from
simple inorganic compounds obtained from their environment.
83. Auxin a plant hormone that causes the elongation of cells in
shoots and is involved in regulating plant growth.
84. Axon of neurons the long thread-like extension of a nerve cell that
conducts nerve impulses from the cell body.
85. B-cell a type of lymphocyte that, when stimulated by a particular
antigen, differentiates into plasma cells that synthesize the antibodies
that circulate in the blood and react with the specific antigens.
86. Bacteria a domain of prokaryotes.
87. Bacteria one of the prokaryotic domains of life, more diverse than
archaeans.
88. Base sequence the order of nucleotide bases in a DNA molecule.
89. Base sequencing the procedure of determining the order of
nucleotides in a DNA section.
90. Beta cells (β-cells) cells in the pancreas that make insulin, a
hormone that controls the level of glucose (a type of sugar) in the
blood.
91. Beta pleated sheet a structure that occurs in many proteins and
consists of two or more parallel adjacent polypeptide chains arranged
in a zigzag pattern, so that hydrogen bonds can form between the
chains.
92. Binary fission method of prokaryotic cell division.
93. Binary fission a type of asexual reproduction common among
prokaryotes where one cell divides giving rise to two cells, each
having the potential to grow to the size of the original cell.
94. Binomial nomenclature agreed upon system for naming organisms
consisting of genus and species.
95. Bioaccumulation The accumulation of a substance, such as a
toxic chemical, in various tissues of a living organism.
96. Biochemical oxygen demand (BOD) The amount of oxygen required
by aerobic microorganisms to decompose the organic matter in a
sample of water. It is used as a measure of the degree of water
pollution. Also referred to as biological oxygen demand.
97. Biodiversity The number and variety of organisms found within a
specified geographic region or ecosystem.
98. Biofuel a type of fuel produced from plants or other forms of
biomass. Examples of biofuels include ethanol, biodiesel, and biogas.
99. Biogeographic factor A factor that effects distribution
of species and ecosystems in geographic space and time (e.g.
island size, climate).
100. Bioinformatics the application of computers to the study of biological
information.
101. Biological control A method of controlling pests using other living
organisms. It relies on predation, parasitism, herbivory, or other
natural mechanisms to control the population of the pest species.
102. Biomagnification The process, in an ecosystem, in which a higher
concentration of a substance in an organism is obtained higher up the
food chain.
103. Biomass the total mass of living matter within a given unit of
environmental area, expressed in terms of living or dry weight per unit
area.
104. Biomass the total mass of living matter within a given unit of
environmental area.
105. Biomass material that comes from living things, including trees,
 crops, grasses, and animals and animal waste. Some kinds of biomass,
such as wood and biofuels, can be burned to produce energy.
106. Biome Regions of similar climate and dominant plant types (i.e. a
type of ecosystem).
107. Biotic factors attributes in an ecosystem that refer to living
organisms.
108. Biotic index a scale for showing the quality of an environment by
indicating the types of organisms present in it.
109. bivalents A structure in which 2 pairs of homologous sister
chromatids have synapsed with one another
110. Blastocyst a thin-walled hollow structure in early embryonic
development that contains a cluster of cells, called the inner cell
mass, from which the embryo arises.
111. Blood clotting the process by which blood becomes thick and stops
flowing, forming a solid cover over any place where your skin has been
cut or broken.
112. Blood glucose the concentration of glucose in the blood, measured in
milligrams of glucose per 100 ml of blood. Normal adult blood glucose
levels range from 70 to 115 mg/100 ml.
113. Blood pressure the hydrostatic force that blood exerts against the
wall of a blood vessel.
114. Body mass index (BMI) a measure for human body shape based on
an individual's mass and height (kg/m2).
115. Boiling point the temperature at which the vapour pressure of a
given liquid reaches atmospheric pressure and thus starts to boil
(100°C for water).
116. Bottom-up limting factors Factors that limit population growth by
affecting resources or lower tropic levels (e.g. interspecific
competition for resources).
117. Bound ribosomes ribosomes that are attached to the outer
surfaces of endoplasmic reticulum and produce proteins that are used
within the plasma membrane or are expelled from the cell via
exocytosis.
118. Bowman’s capsule a double-walled membrane around the
glomerulus of each nephron of the vertebrate kidney, its main role is to
filter to remove organic wastes, excess inorganic salts, and water.
119. Bronchi the two main branches of the trachea that go into the lungs;
this then further divides into the bronchioles and alveoli.
120. Bronchioles any of the fine, thin-walled, tubular extensions of a
bronchus.
121. Calvin cycle the use of ATP and reduced NADP in the stroma to
regenerate RuBP and generate carbohydrates in the light independent
stage of photosynthesis.
122. Cancer general term for more than 100 diseases that are
characterized by uncontrolled, abnormal growth of cells.
123. Capillary a microscopic blood vessel that penetrates the tissues and
consists of a single layer of endothelial cells to allow exchange with
interstitial fluid.
124. Capillary one of the minute blood vessels that connect arterioles and
veins where the interchange of various substances occur.
125. Capillary tubing a tube of small internal diameter that holds liquid by
capillary action.
126. Captive breeding The process of breeding animals in controlled
environments within well-defined settings, such as wildlife reserves
and zoos.
127. capture–mark–release–recaptureA method used to estimate the
population size of mobile animals.
128. Carbohydrates organic compounds with the general formula (CH2O)n,
including sugars, starches, and celluloses, that are an important
source of food and energy for animals.
129. Carbohydrates any of a large group of organic compounds, including
sugars and polysaccharides, such as cellulose, glycogen, and starch,
that contain carbon, hydrogen, and oxygen, with the general formula
(CH2O)n. They are an important source of food and energy for animals.
130. Carbon dioxide (CO2) molecule resulting from oxidation of organic
carbon compounds, and formed in the tissues and eliminated by the
lungs.
131. Carbon dioxide (CO2) a colourless, odourless, incombustible gas
present in the atmosphere and formed during respiration, the
decomposition and combustion of organic compounds, and in the
reaction of acids with carbonates.
132. Carbon dioxide (CO2) a colourless, odourless greenhouse gas
produced naturally when dead animals or plants decay. It is used by
plants during photosynthesis. People are adding carbon dioxide into
the atmosphere, mostly by burning fossil fuels.
133. Carbon fixation the incorporation of inorganic CO2 into an organic
molecule.
134. Carbon flux the flow of carbon from one carbon pool to another.
135. Carboxylic group COOH
136. Cardiac output the volume of blood pumped per minute by the left
 ventricle of the heart.
137. Carrying capacity The maximum population of a species that a
particular ecosystem can sustain (due to limited resources).
138. Cartilage a type of flexible connective tissue with an abundance of
collagenous fibres that controls muscle contractions.
139. Catabolism the breakdown of complex molecules into simpler
molecules, including the hydrolysis of macromolecules into monomers.
140. Catalase an enzyme found in the blood, and in most living cells, that
catalyses the decomposition of hydrogen peroxide into water and
oxygen.
141. Cell plate a membrane that forms midway between dividing plant cells
during cytokinesis and later becomes the cell wall.
142. Cell respiration the controlled release of energy from organic
compounds to produce ATP.
143. Cell respiration a series of metabolic processes that take place within
a cell in which biochemical energy is produced from organic
substances and stored as energy carriers (ATP) for use in the energy-
requiring activities of the cell.
144. Cell respiration a series of metabolic processes that take place within
a cell in which biochemical energy is produced from organic
substances and stored in ATP for use in the energy-requiring activities
of the cell.
145. Cell theorytheory that states that all organisms are composed of cells,
and that all cells come from pre-existing cells.
146. Cell wall non-living carbohydrate-based extracellular material.
147. Cellulose a polysaccharide with the formula (C6H10O5)n, consisting
of a linear chain of between several hundred to over ten thousand β-
linked D-glucose units.
148. Cellulose a complex carbohydrate that is composed of glucose units,
and forms the main constituent of the cell wall in most plants.
149. Centi- metric prefix 1/100th or 1 × 10–2.
150. Centrioles a self-replicating cylindrical organelle that is involved in the
process of nuclear division.
151. Centromere the region joining the two sister chromatids where it
becomes attached to the spindle fibres.
152. Centromere region of the chromosome that becomes attached to
the spindle fibres during cell division.
153. Chemical energy energy released from a substance, or absorbed
in the formation of a chemical compound, during a chemical reaction.
154. Chemiosmosis a process for making ATP using the energy stored in
 an electrochemical gradient of hydrogen ions.
155. Chemiosmosis the process of making ATP using the energy stored in
a proton gradient.
156. chi-square test A statistical method used to calculate whether the
observed and expected genotype frequencies of a population are
significantly different.
157. Chi-squared test a statistical test of the fit between a theoretical
frequency distribution and a frequency distribution of observed data
for which each observation may fall into one of several classes.
158. chiasmata The X-shaped, microscopically visible region representing
homologous chromatids that have exchanged genetic material through
crossing over during meiosis.
159. Chlorophyll main photosynthetic pigment of green plants.
160. Chloroplast cell organelle that is the site of photosynthesis.
161. Cholesterol a lipid that prevents the membrane from becoming too
and also prevents it from crystalizing.
162. Cholinergic synapse a junction between two cells that employs
acetylcholine as its transmitter substance.
163. Chorionic villus sampling technique for diagnosing genetic defects
while a foetus is in the uterus. A small sample of the placenta is
removed and analysed.
164. Chromatography a method of separating and identifying the
components of a complex mixture by differential movement through a
two-phase system.
165. Chromosome a structure within the cell that bears the genetic
material as a thread-like linear strand of DNA with the genes in a linear
order (the human species has 23 pairs).
166. Chromosome a structure within the cell that bears the genetic
material as a thread-like linear strand of DNA that carry the genes in a
linear order (the human species has 23 pairs).
167. Chromosomes linear strand of DNA bonded to proteins in the nucleus
of eukaryotic cells that carries the genetic information.
168. Circadian rhythm a physiological cycle of about 24 hours present
in eukaryotic organisms that persists even in the absence of external
cues.
169. Circular muscles the inner layer of smooth (involuntary) muscle of
the muscle coat (muscularis externa) of the small intestine in which
the muscle fibres encircle the lumen.
170. Clade a group comprised of an ancestral species plus all of the
species that have evolved from the organism.
171. Cladistics constructing a phylogenetic tree based on primitive and
shared derived characteristics.
172. Cladograms a diagram which shows groupings based on primitive
and shared derived characteristics.
173. Class a subdivision of a phylum, a class is composed of one or
more orders of organism.
174. Climate the average weather conditions in a particular location or
region at a particular time of the year. Climate is usually measured
over a period of 30 years or more.
175. Climate change a significant change in the Earth’s climate, including
changes in weather patterns, the oceans, ice and snow, and
ecosystems around the world.
176. Climax community A community composed of species that
represents the final stage of colonization of a habitat.
177. Climograph A graphical representation of basic climatic
parameters (e.g. monthly average temperature and precipitation) at a
certain location.
178. Clones a group of genetically identical cells or individuals.
179. Clones (of plasma cells) differentiated plasma cells that secrete a
specific antibody and a clone of memory cells that make the antibody
on subsequent encounters.
180. Clotting factors proteins in the plasma that serve to activate various
parts of the blood clotting process by being transformed from inactive
to active forms. Also known as coagulation factors.
181. Co-dominant alleles two alleles at a particular locus that have
different effects and are distinguishable in a heterozygous individual
(e.g. AB blood groups).
182. Coarse focus dial used to initially focus a light microscope on a
specimen.
183. Codon each sequence of three bases standing for one of the 20
possible amino acids.
184. Cohesion the force by which individual molecules stick together.
185. Cohesive property the sticking together of similar molecules, such
as one water molecule being attracted to another water molecule. It
also causes water molecules to form drops.
186. Collagen a glycoprotein that forms strong fibres, found in connective
tissue and bone (the most abundant protein in the animal kingdom).
187. Collecting duct a non-secretory tubule that receives urine from
several nephrons and discharges it into the pelvis of the kidney.
188. Colour blindness an abnormal condition caused by an X-linked
 recessive allele and characterized by the inability to clearly
distinguish different colours of the visible light spectrum.
189. Commensalism An ecological relationship between species in which
one is benefited but the other is little affected.
190. Community formed by populations of different species living
together and interacting with each other.
191. Compartmentalization seen in eukaryotes; consequence of
organelles being membrane-bound.
192. Competition An interaction between individuals of the same
species or different species whereby resources used by one are made
unavailable to others.
193. Competitive exclusion principle Principle stating that no two species
competing for the same resource can coexist indefinitely.
194. Competitive inhibitor a molecule that binds to the active site of an
enzyme and prevents the binding of a substrate.
195. Complementary base pairing is the standard arrangement of bases
in nucleotides in relation to their opposite pairing, such as cytosine
paired with guanine and adenine with thymine (or uracil in RNA).
196. Complementary base pairs the standard arrangement of bases in
nucleotides in relation to their opposite pairing, such as cytosine
paired with guanine and adenine with thymine (or uracil in RNA).
197. Concentration gradient a gradient resulting from an unequal
distribution of ions across the cell membrane.
198. Concentration gradient the gradient resulting from an unequal
distribution of ions across the cell membrane.
199. Condensation formation of larger molecules involving the removal of
water from smaller component molecules.
200. Condensation formation of larger molecules from smaller component
molecules involving the removal of water.
201. Conjugated protein a biochemical compound, such as hemoglobin,
made up of a protein molecule and a non-protein prosthetic group.
202. Consumers heterotrophs that feed on living organisms by
ingestion.
203. Continuous variation the variation in phenotypic traits, such as body
weight or height, in which a series of types are distributed on a
continuum rather than grouped into discrete categories.
204. continuous variation An assemblage of measurements of a
phenotypical characteristic which forms from a continuous spectrum
of values, such as body height, skin color or hair curl
205. Convergent evolution where species from different lineages show
 similar characteristics because they are subject to similar selection
pressures.
206. Coral Marine invertebrates in the class Anthozoa (phylum Cnidaria).
They typically live in compact colonies of identical individual polyps.
The group includes the important reef builders that secrete calcium
carbonate to form a hard skeleton.
207. Coral reef a marine ridge or reef consisting of coral and other organic
material consolidated into limestone.
208. Cortical reaction a reaction that occurs during fertilization, when
the sperm cell unites with the egg’s plasma membrane, that prevents
entry of a second sperm.
209. Covalent bonds a chemical bond formed by the sharing of one or more
electrons, especially pairs of electrons, between atoms.
210. Cristae invaginations of the inner mitochondrial membrane.
211. Cross bridge forms in the sarcomere when the globular head of a
myosin molecule attaches temporarily to an adjacent actin filament.
212. Crossbreeding when members of different species breed together.
213. Crossing over exchange of genetic material between non-sister
chromatids during meiosis I.
214. crossing over Process in which homologous chromosomes exchange
portions of their chromatids during meiosis.
215. Cyclic photophosphorylation involves photosystem 1 in a pattern of
electron flow where ATP is generated.
216. Cyclins a family of closely related proteins that regulate the cell
cycle in eukaryotic cells.
217. Cystic fibrosis a mutation in a gene that changes a protein that
regulates the movement of salt in and out of cells; characterized by
the production of thick and sticky mucus.
218. Cytokinesis the division of the cytoplasm and the plasma
membrane, following the division of the nucleus, resulting in two cells
in mitosis.
219. Cytosine an organic base found in DNA and RNA in which it pairs with
guanine.
220. Davson-Danielli model model of the cell membrane in which the
phospholipid bilayer is between two layers of protein.
221. Decarboxylation a chemical reaction that involves the removal of CO2.
222. Degenerate code there are more codons (64) than there are amino
acids to be coded, so most amino acids are coded by more than one
code.
223. Dehydration the excessive loss of water from the body, or from an
 organ or body part, as a result of illness or fluid deprivation.
224. Deletion a type of chromosomal aberration in which a segment of the
chromosome is removed or lost.
225. Denaturation a structural change in a protein that results in a
permanent loss of biological properties.
226. Denaturation a structural change in a protein that alters its three-
dimensional shape and causes the loss of its biological properties.
227. Denitrification A process facilitated by bacteria, in which nitrates
(NO3) break down to molecular nitrogen (N2).
228. Denitrifying bacteria Bacteria that facilitate the process known as
denitrification, as part of the nitrogen cycle, e.g. Pseudomonas.
229. Density dependent limiting factors A factor limiting population
growth that increases as the population increases.
230. Density independent limting factors A factor limiting population
growth that equally effects small and large populations.
231. Depolarization a positive-going change in the membrane potential of
neurons making it more positive, or less negative. It may result in an
action potential.
232. Desert A dry ecosystem characterised by little rainfall, extreme
temperatures, and sparse vegetation.
233. Detritivores heterotrophs that obtain organic nutrients from dead
organisms by internal digestion.
234. Diabetes a group of metabolic diseases in which a person has high
blood sugar, either because the pancreas does not produce enough
insulin, or because cells do not respond to the insulin that is produced.
235. Dialysis the separation of smaller molecules from larger molecules,
or of dissolved substances in a solution by selective diffusion through
a semi-permeable membrane,
236. Diaphragm a dome-shaped muscular partition separating the thorax
from the abdomen. It plays a major role in breathing as its contraction
increases the volume of the thorax and so inflates the lungs.
237. Diastolic pressure the minimum blood pressure during relaxation of
heart muscles.
238. Different conformations alternative structures of the same protein.
239. Differentiation the alteration of a cell’s morphology and physiology
through changes in gene expression.
240. Differentiation the process regulated by different gene expression by
which cells or tissues undergo a change toward a more specialized
form or function, especially during embryonic development.
241. Diffusion passive movement of particles from a region of higher
 concentration to a region of lower concentration.
242. dihybrid cross A cross between two individuals, concentrating on
two definable traits, for example pea color and height of pea plant
243. Dipeptide two amino acids linked together.
244. Diploid a cell containing two sets of chromosomes (2n), one from
each parent.
245. diploid An organism or cell having two sets of chromosomes or
twice the haploid number
246. Diploid cells have nuclei containing two sets of chromosomes (2n),
one set from each parent.
247. directional selection Natural selection in which individuals at one end
of the phenotypic range survive or reproduce more successfully than
do other individuals.
248. Disaccharide sugar (carbohydrate) composed of two
monosaccharides joined by condensation.
249. Disaccharide a sugar (carbohydrate) composed of two
monosaccharides joined by condensation.
250. Discontinuous variation the variation in phenotypic traits in which
types are grouped into discrete categories with few or no intermediate
phenotypes.
251. discrete variation Inherited characteristic that have a limited
number of variations, such as the ability or inability to roll one's tongue
252. disruptive selection form of natural selection in which a single curve
splits into two; occurs when individuals at the upper and lower ends of
a distribution curve have higher fitness than individuals near the
middle
253. Distal convoluted tubule the convoluted portion of the nephron that
lies between the loop of Henle and the non-secretory part of the
nephron that is concerned especially with the concentration of urine.
254. Divergent evolution the change in the genetic composition of a
population during successive generations, as a result of natural
selection acting on the genetic variation among individuals, and
resulting in the development of new species.
255. Divergent evolution a pattern of evolution where an ancestral
species evolves into a number of distinct species due to exposure of
different populations to different selection pressures.
256. DNA a nucleic acid consisting of two long chains of nucleotides
twisted into a double helix that carries the genetic information in the
cell and is capable of self-replication and synthesis of RNA.
257. DNA gyrase a bacterial enzyme that catalyses the breaking and re-
 joining of bonds linking adjacent nucleotides in circular DNA to
generate supercoiled DNA helices.
258. DNA ligasea linking enzyme essential for DNA replication.
259. DNA methylation the modification of a strand of DNA after it is
replicated, in which a methyl (CH3) group is added and is one of the
methods used to regulate the expression of genes.
260. DNA polymerase an enzyme that catalyses the elongation of new
DNA during replication.
261. DNA polymerase an enzyme that catalyses the elongation of new
DNA during replication.
262. DNA polymerases various enzymes that function in the replication
and repair of DNA by catalysing the linking of nucleotides in a specific
order, using single-stranded DNA as a template.
263. DNA primase an enzyme involved in the initiation of DNA replication
that catalyses the polymerization of short RNA primers on the
template DNA.
264. DNA profiling the analysis of a small amount of genetic material
used to identify multilocus DNA banding patterns that are specific to
an individual is often used to provide evidence in criminal law cases;
also called genetic fingerprinting.
265. DNA profiling (DNA fingerprinting) the analysis of a small amount
of genetic material, which is as unique per individual as a fingerprint
is, as an aid to identification.
266. DNA replication the process of making an identical copy of a DNA
molecule, using existing DNA as a template for the synthesis of new
DNA strands.
267. Domains one of the three major categories of life: archaea, bacteria,
and eukarya.
268. Dominant alleles the allele that is fully expressed in the
phenotype of a heterozygote.
269. Down syndrome a human genetic disease resulting from having an
extra chromosome 21 (characterized by having a delay in mental
development).
270. Down syndrome a human genetic disease resulting from having an
extra chromosome 21 (characterized by having a delay in mental
development).
271. Ecological niche The ecological role and space that
an organism fills in an ecosystem.
272. Ecological succession describes the process by which a sequence
of increasingly complex communities develop over time.
273. Ecosystemcommunity of different species interacting with each other
and with the chemical and physical factors making up the non-living
environment.
274. Ecosystema system that includes all biotic factors (living organisms)
in an area as well as its abiotic factors (physical environment)
functioning together as a unit.
275. Edge effect The changes in population or community structures
that occur at the boundary of two habitats.
276. Elastic fibres a thick, yellow connective-tissue fibre composed
principally of elastin and characterized by giving great elasticity to
tissues in the body.
277. Electron carriers proteins arranged in chains on the membrane to
allow the transfer of electrons from one carrier to another.
278. Electron micrograph a photograph or image of a specimen taken using
an electron microscope.
279. Electron tomography a method used to generate a three-dimensional
image of the inner mitochondrial membrane.
280. Electron transport chain a group of proteins that accept and donate
electrons in a series.
281. Embryo the earliest stages in the development of a new plant or
animal from a fertilized ovum and entirely dependent on nutrients
supplied by the parent.
282. Embryo an organism in its early stages of development, especially
before it has reached a distinctively recognizable form.
283. Embryonic gonads the male and female sex organs in the embryo.
284. Emergent property a property of a system that emerges from the
interaction of the elements of the system.
285. EmigrationDecreases to population size by movement of individuals to
external populations.
286. Emphysema a chronic respiratory disease where there is over-
inflation of the air sacs (alveoli) in the lungs causing a decrease in
lung function and often breathlessness.
287. Endangered species A species which has been categorized by the
International Union for Conservation of Nature (IUCN) as likely to
become extinct.
288. Endemic species A species unique to a defined geographic
location or ecosystem.
289. Endergonic energy storing reactions.
290. Endocytosis the process in which the cell takes in materials from
the outside by infolding of the membrane to form a vesicle.
291. Endometrium the mucous membrane lining the womb, which
thickens during the menstrual cycle in preparation for possible
implantation of an embryo.
292. Endopeptidase any of a large group of enzymes that catalyse the
hydrolysis of peptide bonds in the interior of a polypeptide chain or
protein molecule.
293. Endoplasmic reticulum (ER) site of synthesis of proteins destined
for export or for secretion.
294. Endosymbiotic theorya theory that some eukaryotic organelles, such
as mitochondria and chloroplasts, originated as free-living prokaryotes
that invaded primitive eukaryotic cells.
295. Energy flow the movement of energy around an ecosystem by
biotic and abiotic means.
296. Enzyme activity a measure of the ability of an enzyme to catalyse a
specific reaction.
297. Enzymes a class of proteins that catalyses chemical reactions.
298. Enzymes proteins or conjugated proteins produced by living
organisms and functioning as biochemical catalysts.
299. Epidemiology the study of the incidence and causes of disease.
300. Epinephrine a hormone produced as a response to stress, also
called adrenaline.
301. Epithelium the thin tissue forming the outer layer of a body's surface
and lining the alimentary canal and other hollow structures.
302. Equatorial plate the figure formed by the chromosomes in the centre of
the spindle during mitosis.
303. Estrogen a female steroid hormone produced by the ovaries and
responsible for promoting and maintenance of female secondary sex
characteristics.
304. Estrogen any of several steroid hormones produced chiefly by the
ovaries and responsible for promoting oestrus and the development
and maintenance of female secondary sex characteristics.
305. Ethanol alcohol formed by microbial fermentation of carbohydrates.
306. Eukaryote organisms with membrane-bound nuclei.
307. Eukaryotes one of the three domains of life, cells are
compartmentalized.
308. Eutrophication The response of aquatic ecosystems to the addition of
artificial or natural nutrients through detergents, fertilizers, or sewage.
Commonly an intial algal blooms is followed by a decline in dissolved
oxygen.
309. Evenness A measure of biodiversity based on how even the
 abundance of each species in a geographic region or ecosystem.
310. Evolution the change in the genetic composition of a population
during successive generations, as a result of natural selection acting
on the genetic variation among individuals, and resulting in the
development of new species.
311. Ex situ conservation Off-site conservation or the conservation of
genetic resources outside natural ecosystems.
312. Exergonic energy releasing reactions.
313. Exocrine glands glands that secrete their products into ducts.
314. Exocytosisthe process in which the cell releases materials to the
outside by discharging them as membrane-bounded vesicles that pass
through the cell membrane.
315. Exon sequence of DNA that codes information for protein synthesis
that is transcribed to messenger RNA.
316. Exoskeleton a rigid external covering for the body in some
invertebrate animals, especially arthropods.
317. Expiration when the muscles of the thorax contract to cause the
volume to decrease, this increases the pressure in the lungs and air
moves from the higher pressure inside the lungs to the lower pressure
outside the body.
318. Exponential phase Phase of unlimited growth of a population in an
unlimited environment. Represented by a J-shaped curve when
population size is plotted over time.
319. External fertilization a form of fertilization in which a sperm cell is
united with an egg cell external to the bodies of the reproducing
individuals.
320. Extracellular matrix a network of material that is secreted by cells
that serves to support, strengthen, and organize cells.
321. Facilitated diffusion diffusion through a membrane that requires
proteins.
322. Family a subdivision of an order: composed of one or more genera.
323. Fatty acids any of the group of a long chain of hydrocarbon
derived from the breakdown of fats having a single carboxylic group
and aliphatic tail.
324. Fermentation anaerobic breakdown of glucose with the end-
products of ethanol and carbon dioxide or lactic acid.
325. Fertilization the action or process of fertilizing an egg or a female
animal or plant, involving the fusion of male and female gametes to
form a zygote.
326. fertilization Male sex cell (sperm) unites with female sex cell into
 one cell (46 chromosomes -- 23 from each).
327. Fibrin the activated form of the blood-clotting protein fibrinogen.
328. Fibrinogen a protein in the blood plasma that is essential for the
coagulation of blood and is converted to fibrin by the action of
thrombin.
329. Figwort a family of angiosperms.
330. First consumer the name given to an organism that feeds on the
producer in a food chain. For example, a goat is considered a first
order consumer since it eats green plants.
331. Flagellum a relatively long extension of the cell used in locomotion.
332. Flowering the process of producing conspicuous flowers.
333. Fluid mosaic model a model conceived by S.J. Singer and Garth
Nicolson in 1972 to describe the observed structural features of
biological membranes.
334. Fluidity refers to the viscosity of a lipid bilayer of the membrane
that allows it to change shape.
335. Food chains a feeding hierarchy in which organisms in an
ecosystem are grouped into trophic (nutritional) levels and are shown
in a succession to represent the flow of food energy and the feeding
relationships between them.
336. Food conversion ratio is a measure of an animal's efficiency in
converting feed mass into the mass of desired output.
337. Food web A diagram showing feeding relationships of organisms
within an ecosystem or community. It consists of multiple interlinked
food chains.
338. Fossil a remnant, or representation, of an organism that existed in
a past geological age, or of the activity of such an organism, occurring
in the form of mineralized bones, shells, etc., as casts, impressions,
and moulds.
339. Fossil fuel a type of fuel created over millions of years as dead plant
and animal material becomes trapped and buried in layers of rock, and
then heat and pressure transform this material into a fuel deep within
the Earth. Examples of fossil fuels include coal, oil, and natural gas.
340. Fossilised organic matter when remains of organisms of a past
geologic age have been preserved in a fossil form.
341. Frame shift a genetic mutation, caused by a deletion or insertion
in a DNA sequence, that shifts the way the sequence is read.
342. Free ribosomes can move about anywhere in the cytoplasm and the
proteins they make are free to go anywhere within the cell.
343. Freezing point the temperature at which a liquid solidifies (0°C for
 water).
344. Fundamental niche The full range of environmental conditions and
resources an organism can possibly occupy and use (when limiting
factors are absent in its habitat).
345. fusion of gametes occurs when two haploids (an egg and sperm)
join to form one zygote (first cell of life)
346. Gamete a reproductive cell or sex cell that contains the haploid set
of chromosomes, e.g. sperm cell (male reproductive cell) and egg cell
(female reproductive cell).
347. Gamete a mature haploid male or female germ cell, which is able to
unite with another of the opposite sex in sexual reproduction to form a
zygote.
348. Gametes one of two haploid reproductive cells, egg or sperm, whose
union is necessary in sexual reproduction to produce a diploid zygote.
349. Gametes one of two haploid reproductive cells, egg or sperm, whose
union is necessary in sexual reproduction to produce a diploid zygote.
350. gametes A haploid cell such as an egg or sperm. Gametes unite
during sexual reproduction to produce a diploid zygote.
351. Gametogenesis the process in which cells undergo meiosis to form
gametes.
352. Gel electrophoresis the separation of nucleic acids or proteins on the
basis of their size and electrical charge by measuring their rate of
movement through a gel.
353. Genbank database an open access, annotated collection of all
publicly available nucleotide sequences and their protein translations.
354. Gene a heritable section of DNA that controls a specific trait.
355. Gene a hereditary unit consisting of a sequence of DNA that occupies
a specific location on a chromosome and determines a particular
characteristic in an organism.
356. Gene a hereditary unit consisting of a sequence of DNA that occupies
a specific location on a chromosome and determines a particular
characteristic in an organism.
357. Gene a hereditary unit consisting of a sequence of DNA that occupies
a specific location on a chromosome and determines a particular
characteristic in an organism.
358. Gene a section of DNA on a chromosome that controls a specific trait.
359. Gene expression the synthesis of a functional gene product, often
protein, but also rRNA, tRNA, or snRNA.
360. Gene expression conversion of the information from the gene into
mRNA via transcription and then to protein via translation resulting in
 the phenotypic manifestation of the gene.
361. gene loci specific locations of genes along the chromosome
362. Gene mapping the process of determining the locus for a particular
biological trait.
363. Gene pool The gene pool is the set of all genes, or genetic information,
in any population, usually of a particular species.
364. Genetic code a nearly universal sequence of nucleotides in DNA
that determines the specific amino acid sequence in the synthesis of
proteins.
365. Genetic code the order of bases in DNA that determines the
sequence of amino acids in proteins.
366. Genetic modification the change to the genetic constitution of an
organism by artificial methods.
367. Genome the total genetic material of an organism.
368. Genome the total genetic material of an organism.
369. Genome total genetic contents of an organism.
370. Genotype the genetic constitution of an organism.
371. Genus a subdivision of a family: composed of one or more species.
372. Germ-line cells the cellular lineage of a sexually reproducing
organism from which eggs and sperm are derived.
373. Gersmehl diagrams Diagrams showing the inter-relationships
between nutrient stores and flows in an ecosystem.
374. Gigatone equivalent to a one billion tonnes.
375. Global warming the increase in temperature near the surface of the
Earth as a result of natural causes. However, the term is most often
used to refer to recent and on-going warming caused by people’s
activities.
376. Glomerulus a group of capillaries, situated within a Bowman’s
capsule in the nephron of the vertebrate kidney, which filter waste
products from the blood and so initiate urine formation.
377. Glucagon a hormone secreted by the pancreas that raises blood
glucose levels by hydrolysing glucagon molecules in the liver.
378. Glucose a simple monosaccharide sugar (C6H12O6) that serves as
the main source of energy and as an important metabolic substrate for
most living organisms.
379. Glucose monosaccharide that is an end product of carbohydrate
metabolism, and is the chief source of energy for living organisms.
380. Glutamic acid a non-essential amino acid, occurring in proteins, that
is replaced by valine in cases of sickle cell anaemia.
381. Glycerol a metabolic intermediate and structural component of the
 major classes of biological lipids, triglycerides, and phospholipids.
382. Glycogen a branched polymer of glucose that is mainly produced in
liver and muscle cells, and functions as secondary long-term energy
storage in animal cells.
383. Glycogen a polysaccharide that is the main form of carbohydrate
storage in animals and occurs primarily in the liver and muscle tissue.
It is readily converted to glucose when needed by the body to satisfy
its energy needs.
384. Glycolysis a metabolic pathway that breaks glucose down to pyruvate.
385. Glycoproteins proteins that contain oligosaccharide chains.
386. Golgi body a eukaryotic organelle that modifies proteins after
translation.
387. gradualism A proposed explanation in evolutionary biology stating
that new species arise from the result of slight modifications
(mutations and resulting phenotypic changes) over many generations.
388. Greenhouse gases natural or man-made gases that trap heat in the
atmosphere and contribute to the greenhouse effect. Greenhouse
gases include water vapour, carbon dioxide, methane, nitrous oxide,
and fluorinated gases.
389. Gross production The amount of organic matter (biomass)
produced by plants, expressed as energy per unit area per unit time
period.
390. Growth an increase in physical size.
391. Guanine an organic base found in DNA and RNA in which it pairs with
cytosine.
392. Gyres A large system of rotating ocean currents, there are five
major rotating currents in the Earth's oceans.
393. Haemodialysis a method used after kidney failure for the removal of
certain elements from the blood based on the difference in their rates
of diffusion through a semi-permeable membrane while being
circulated outside the body. The process involves both diffusion and
ultrafiltration.
394. Haemoglobin the oxygen-carrying pigment of red blood cells that
gives them their red colour and serves to convey oxygen to the tissues.
395. Haemophilia a sex-linked inheritable disease characterized by loss
or impairment of the normal clotting ability of blood, so that a minor
wound may result in fatal bleeding.
396. haploid An organism or cell having only one complete set of
chromosomes
397. Haploid cells have one chromosome of each pair (have one full set
 of the chromosomes that are found in its species).
398. Haploid cells have one chromosome of each pair (have one full set
of the chromosomes that are found in its species).
399. Haploid cells have one chromosome of each pair (have one full set
of the chromosomes that are found in its species).
400. Helicase an enzyme involved in DNA replication, responsible for
unwinding the double helix.
401. Helicase a prokaryote enzyme that unwinds the DNA helix at the
replication fork, breaking the hydrogen bonds, to allow the resulting
single strands to be copied.
402. Heritable characteristics characteristics that are capable of being
passed from one generation to the next through the genes.
403. Heterotroph an organism that gets its organic nutrients by feeding
on autotrophs or other heterotrophs.
404. Heterotroph an organism that obtains carbon by feeding on the
organic material present in other organisms, living or dead.
405. Histamine a physiologically active amine found in plant and animal
tissue and released from mast cells as part of an allergic reaction in
humans. It causes the dilation of capillaries, constriction of bronchial
smooth muscle, and decreased blood pressure.
406. Histone a protein associated with DNA that plays a role in gene
expression and the packing of DNA.
407. Histone any of several small, basic proteins most commonly found
in association with the DNA in the chromatin of eukaryotes.
408. Histones globular proteins associated to chromosomes in eukaryotic
cells.
409. Homeostasis the process in which an organism regulates activities
within cells and their bodies to keep conditions stable.
410. Homologous chromosomes chromosome pairs with genes for the same
characteristics at corresponding loci.
411. Homologous chromosomes chromosome pairs with genes for the same
characteristics at corresponding loci.
412. Homologous structures structures derived from a common
ancestor or same evolutionary or developmental origin but not
necessarily in function, e.g. the wing of a bird and the foreleg of a
horse
413. Homologous trait Traits that are shared by species with a common
ancestor. These traits are similar in structure, but may have very
different functions and appearances.
414. Hormone a substance, usually a peptide or steroid, produced by one
 tissue and transported by the blood to another to affect physiological
activity, such as growth or metabolism.
415. Hormone-binding sites proteins on the outside of the membrane
that allow specific hormones to bind.
416. Human chorionic gonadotropin (HCG) a hormone produced by the
placenta that maintains the corpus luteum during pregnancy.
417. Human Genome Project an international scientific research project
to determine the sequence of chemical base pairs that make up human
DNA, and to identify and map all of the genes of the human genome.
418. Huntington’s disease caused by a genetic defect on chromosome 4;
the defect causes a part of DNA, called a CAG repeat, to occur many
more times than it is supposed to.
419. hybrid vigour The increased vigour (eg: growth, litter size, milk
production) of crossbred animals
420. Hybridomaa cell hybrid produced in vitro by the fusion of a lymphocyte
that produces antibodies and a myeloma tumour cell in order to
produce a continuous supply of a specific antibody.
421. Hydrogen bond a weak bond caused by electrostatic attraction
between a positively-charged part of one molecule and a negatively-
charged part of another.
422. Hydrogen bond a chemical bond in which a hydrogen atom of one
molecule is attracted to an electronegative atom of another molecule.
423. Hydrogen bonds a chemical bond in which a hydrogen atom of one
molecule is attracted to an electronegative atom of another molecule.
424. Hydrolysis decomposition of a chemical compound by reaction with
water.
425. Hydrophilic molecules that are attracted to water.
426. Hydrophilic molecules capable of interacting with water through
hydrogen bonding (having an affinity for water).
427. Hydrophobic molecules that are not attracted to water but are
attracted to each other.
428. Hydrophobic molecules that lack an affinity for water (water
insoluble).
429. Hydrostatic pressure gradient the stress that develops when
solutions containing different concentrations of solute in a common
solvent are separated by a membrane that is permeable to the solvent,
but not the solute.
430. Hypertonic a more concentrated solution relative to another fluid.
431. Hypothalamus a region of the brain that functions as the main control
centre for the autonomic nervous system.
432. Hypotonic a less concentrated solution relative to another fluid.
433. Immigration Increases to population size by movement of
individuals from external populations.
434. Immunoglobulins group of large glycoproteins that function as
antibodies in the immune response by binding with specific antigens.
435. In situ conservation On-site conservation or the conservation of
genetic resources in natural ecosystems.
436. Incompressibility of water the incapability of water to lose volume in
response to pressure.
437. independent assortment the random distribution of the pairs of
genes on different chromosomes to the gametes
438. Indicator species A species presence whose absence can be used
as a indicator of environmental conditions.
439. Infrared radiation a type of electromagnetic radiation. The Earth
gives off energy in the form of infrared radiation, which is not visible to
the naked eye and feels like heat to the human body.
440. Inorganic nutrients chemical elements, compounds, and other
substances necessary to sustain life processes that are not
chemically carbon-based.
441. Insectivorous plants Plants that derive some or most of their
nutrients (but not energy) from trapping and consuming commonly
insects (other arthropods, protozoans and animals may also be
trapped).
442. Insertion the addition by mutation of one or more nucleotides to a
chromosome.
443. Inspiration when the air moves from a higher pressure (outside the
body) to the lower pressure (inside the lungs).
444. Insulin a hormone that lowers blood glucose levels by synthesizing
glycogen.
445. Insulin a hormone that lowers blood glucose levels by synthesizing
glycogen.
446. Insulin a hormone that lowers blood glucose levels by promoting
the uptake of glucose by most body cells and the storage in the liver.
447. Integral proteins proteins embedded in the phospholipid bilayer.
448. Interbreeding when two members of the same species mate and
produce offspring.
449. Intercostal muscles muscles found between the ribs. They are mainly
involved in the mechanical aspect of breathing.
450. Internal fertilization when fertilization takes place inside the female
body.
451. Interspecific interactions Interplay between species that affects one
or more of them.
452. Intraspecific interactions Interplay between members of the same
species that affects one or more of them.
453. Intron a segment of a gene situated between exons that is
removed before the translation of messenger RNA and does not
function in coding for protein synthesis.
454. Intron segment of a gene situated between exons that is removed
before the translation of messenger RNA and does not function in
coding for protein synthesis.
455. Invasive species A plant or animal species that is not native to a
particular eosystem or location and has a tendency to spread causing
damage to the environment, human economy and/or human health
456. Isomers chemical compounds of the same chemical formula but
different structure (cis or trans).
457. Joint capsule a ligamentous sac that surrounds the articular cavity
of a freely movable joint. It is attached to the bones, completely
encloses the joint, and is composed of an outer fibrous membrane and
an inner synovial membrane.
458. Karyogram shows the chromosomes of an organism in
homologous pairs of decreasing length.
459. Karyotype a method of organizing the chromosomes of a cell in
relation to number, size, and type.
460. Karyotype a method of organizing the chromosomes of a cell in
relation to number, size, and type.
461. Keystone species Species that have effects on communities that
far exceed their abundance.
462. Kingdom a taxonomic group that contains one or more phyla.
463. Lactase the enzyme responsible for catalysing the split of lactose
into galactose and glucose.
464. Lactose a disaccharide sugar that is commonly found in milk and
consists of galactose and glucose.
465. Lactose a disaccharide (C12H22O11) found in milk that may be
hydrolysed to yield glucose and galactose.
466. Lagging strand the strand of the DNA double helix that, because of its
orientation that is opposite to the working orientation of DNA
polymerase III, is synthesized in a series of short fragments known as
Okazaki fragments.
467. Leaching The loss of water-soluble nutrients from the soil, due to rain
and irrigation. Nutrients lost from soils enter aquatic ecosystems.
468. Leading strand DNA strand being replicated by continuous
polymerization at the 3′ growing tip.
469. Legumes A plant of the pea family. Most species have symbiotic
nitrogen-fixing bacteria in structures called root nodules.
470. Leptin an adipose-derived hormone that plays a key role in
regulating energy intake and expenditure, including appetite and
hunger, metabolism, and behaviour.
471. Light band the zone of thin filaments in the sarcomere that is not
superimposed by thick filaments.
472. Light energy the energy produced or given off directly from the sun
causing the growth of plants and the existence of most life forms.
473. Light-dependent reactions the reactions within photosynthesis that
use light to generate ATP and reduced NADP.
474. Light-independent reactions the photosynthetic reactions that
take place within the stroma and use reduced NADP and ATP to
generate carbohydrates.
475. Limestone a sedimentary rock consisting mainly of calcium carbonate,
deposited as the calcareous remains of marine animals or chemically
precipitated from the sea.
476. Limiting factors an environmental factor, such as carbon dioxide or
light intensity, that controls the process of photosynthesis.
477. Limits of tolerance The highest/lowest values of abiotic factor that
an organism can survive.
478. Link reaction a decarboxylation reaction that occurs in the
mitochondrion between glycolysis and the Krebs cycle.
479. linked genes Genes located on the same chromosome that tend to
be inherited together in genetic crosses
480. Lipase a pancreatic enzyme that catalyses the breakdown of lipids
through the hydrolysis of the linkages between fatty acids and glycerol
in triglycerides and phospholipids.
481. Lipids organic compounds, including the fats, oils, waxes, sterols,
and triglycerides, that are insoluble in water, but soluble in non-polar
organic solvents.
482. Lipids organic compounds, including the fats, oils, waxes, sterols,
and triglycerides, that are insoluble in water,but soluble in non-polar
organic solvents.
483. Liver a large glandular organ located in the upper right side of the
abdominal cavity active in the secretion of bile and various metabolic
processes.
484. Locus the position of a gene on the chromosome (loci plural).
485. Locus the position of the gene on the chromosome (loci plural).
486. Long wave radiation (infrared light) radiation emitted in the spectral
wavelength greater than 4 µm corresponding to the radiation emitted
from the Earth and atmosphere.
487. Longitudinal muscles (of the stomach)the outer longitudinal layer of
smooth muscles, continuous with that of the esophagus.
488. Loop of Henle the U-shaped section of the nephron of a vertebrate
kidney that is situated between the proximal and distal convoluted
tubules and plays a role in the regulation of the concentrating of ions
in the urine.
489. Louis Pasteur French scientist that proved, among other things, that
the emergent growth of bacteria in nutrient broths is due to
biogenesis, not spontaneous generation.
490. Lumen the inner open space or cavity of the small intestine.
491. Lymphocyte a white blood cell that could be a B-cell or a T-cell.
492. Lysis splitting
493. Lysosome a cellular organelle involved in cellular digestion.
494. Macromolecule a very large molecule, such as a polymer or protein,
consisting of many smaller structural units linked together.
495. Macroplastic debris Plastic particles larger than 1mm that are a
marine pollutant.
496. Magnification ratio of image size to actual size.
497. Malpighian tubule system the organ of excretion in insects and many
other arthropods consisting of narrow tubules opening into the
anterior part of the hindgut.
498. Maltose a disaccharide formed when two glucose monomers join
together.
499. Medulla the lowest part of the brain that controls autonomic and
homeostatic functions.
500. Medulla the inner, darker portion of the parenchyma of the kidneys
that consists of the renal pyramids.
501. Meiosis the process of cell division in sexually reproducing
organisms that reduces the number of chromosomes in reproductive
cells from diploid to haploid.
502. Meiosis reduction division involving the production of gametes.
503. Meiosis the process of cell division in sexually reproducing
organisms that reduces the number of chromosomes in reproductive
cells from diploid to haploid, leading to the production of gametes in
animals and spores in plants.
504. Melanism an increased amount of black or nearly black pigmentation
 (as of skin, feathers, or hair) of an organism, resulting from the
presence of melanin.
505. Melatonin a hormone derived from serotonin that plays a role in sleep,
ageing, and reproduction in mammals.
506. Memory cell a long-lived cell of the immune system that has
previously encountered a specific antigen and that upon re-exposure
produces large amounts of antibody.
507. Memory cell a type of lymphocyte that is released as a specific
immune response and is stored in case of a second exposure to the
same antigen.
508. Menstrual cycle the monthly series of physiological changes in women
that occurs in the uterus and ovary for the purpose of sexual
reproduction. If the egg is not fertilized, the lining of the uterus breaks
down and is discharged during menstruation.
509. Meristem a region of plant tissue, found chiefly at the growing tips of
roots and shoots and in the cambium, consisting of actively dividing
cells forming new tissue.
510. Mesocosm an experimental tool that brings a small part of the natural
environment under controlled conditions.
511. Messenger RNA (mRNA) a type of RNA that attaches to ribosomes
and specifies the sequence of amino acids in a protein.
512. Metabolic chains a series of reactions, with each one catalyzed by
a different enzyme.
513. Metabolic cycles a cycle of enzyme catalyzed reactions that
regenerates a series of organic molecules with each turn of the cycle.
514. Metabolic pathways a series of enzymatic reactions that converts
one biological material to another.
515. Metabolic rate the chemical processes occurring within a living cell
or organism during a certain period.
516. Metabolism the sum of all of the chemical reactions that occur
within an organism or within a cell.
517. Metabolism the process involving biochemical reactions of life.
518. Metabolism all of an organism’s chemical processes.
519. Metabolism the totality of all the chemical processes in an
organism, consisting of anabolic and catabolic mechanisms.
520. Metabolism the sum total of all chemical reactions that occur
within an organism.
521. Metaphasestage in mitosis in which chromosomes become arranged at
the equatorial plate.
522. Metastasischaracteristic of malignant tumours of transferring the
 disease from one organ to another not directly connected with it.
523. Methane a light, colourless gas (CH4).
524. Methane (CH4) an odourless, colourless, flammable gas. It is the
major constituent of natural gas, which is used as a fuel, and is an
important source of hydrogen and a wide variety of organic
compounds.
525. Methane (CH4) a colourless, odourless greenhouse gas that occurs
both naturally and as a result of people’s activities. Methane is
produced by the decay of plants, animals, and waste, as well as other
processes.
526. Micro- metric prefix 1 × 10–6.
527. Microplastic debris Plastic particles smaller than 1mm that are a
marine pollutant.
528. Micropropagation the propagation of plants by growing plantlets in
tissue culture and then planting them out.
529. Microtubule fibres hollow protein tubes seen during the mitosis of
animal cells.
530. Milli- metric prefix 1 × 10–3.
531. Mineral ions individual elements with an electrical charge.
532. Mitochondrial matrix a compartment inside the inner membrane of the
mitochondrion.
533. Mitosis the process where a single cell divides into two identical
cells, each containing the same number of chromosomes and genetic
content as that of the original cell.
534. Mitosis a type of cell division that results in two daughter cells
each having the same number and kind of chromosomes as the parent
nucleus, it is typical of ordinary tissue growth.
535. Mitotic index the ratio between the number of cells in mitosis to the
total number of cells.
536. Molecular clock using the number of differences in DNA or amino acid
sequences to deduce how long ago species split.
537. Monoclonal antibodies any of the highly specific antibodies
produced in large quantities by the clones of a single hybrid cell that
has been formed in the laboratory by the fusion of a B-cell with a
tumour cell.
538. Monomer a molecule that can combine with others to form a polymer.
539. Monomers consist of a single component.
540. Monosaccharidethe simplest form of carbohydrate (examples include
fructose, glucose, and ribose) that constitutes the building blocks of
more complex forms of sugar.
541. Monosaccharidethe simplest form of carbohydrate (for example
fructose, glucose, and ribose) that constitutes the building blocks of a
more complex form of sugars.
542. Monounsaturated an unsaturated molecule that contains only one
double or triple bond in the carbon chain.
543. Mortality Decreases to population size as a result of death (e.g.
predation, senescence)
544. Mucosa a mucus-secreting membrane lining all bodily passages that
are open to the air, such as the digestive tract.
545. Mucous membranes membrane lining all body passages and having
cells and associated glands that secrete mucus. Also called mucosa.
546. Mutagen a chemical or physical agent that interacts with DNA and
causes a mutation.
547. Mutagens chemical agents that increase the rate of genetic mutation.
548. Mutation a change of the DNA sequence within a gene or
chromosome of an organism that results in the creation of a new
character or trait not found in the parental type.
549. Mutation a change in DNA.
550. Mutualistic relationship an association between organisms of two
different species in which each member benefits.
551. Myelination the process of development or formation of a myelin
sheath around a nerve fibre.
552. Myofibril a long, cylindrical organelle in striated muscle cells,
composed mainly of actin and myosin filaments, that runs from one
end of the cell to the other and is organized in repetitive subunits
called sarcomeres.
553. Myogenic contraction a contraction of the heart without external
stimulation from a nerve.
554. Myosin filament one of the contractile elements in skeletal, cardiac,
and smooth muscle fibres.
555. Naked DNA DNA not associated with histones or histone-like
proteins.
556. Naked DNA the DNA in prokaryotic cells that is not associated
with proteins.
557. Nano- metric prefix 1 × 10–9.
558. Nanometre one billionth (10–9) of a metre.
559. Natality Increases to population size through reproduction (i.e.
births)
560. Natural selection survival to reproductive age of the varieties that
are best adapted to existing environmental conditions.
561. Nature reserve A protected area of importance for wildlife, flora,
fauna which is reserved and managed for conservation.
562. Negative feedback when the system responds in an opposite
direction to a perturbation.
563. Nephron the structural and functional units of the kidney, numbering
about a million in the renal parenchyma, each one is capable of
forming urine.
564. Net production The amount of organic matter produced by plants
minus what is needed for plant respiration, expressed as energy per
unit area per unit time period.
565. Neuron a specialized, impulse-conducting cell that is the functional
unit of the nervous system, consisting of the cell body and its
processes, the axon, and dendrites.
566. Neurotransmitter a substance that transmits nerve impulses
across a synapse.
567. Nitrification The process by which ammonia is converted to nitrite
(NO2-) and then nitrate (NO3-) by microorganisms.
568. Nitrifying bacteria Bacteria that facilitate part of the process
known as nitrification, as part of the nitrogen cycle, e.g. Nitrosomonas
convert ammonia to nitrite and Nitrobacter convert nitrite to nitrate.
569. Nitrogen fixation The conversion of atmospheric nitrogen into
compounds that plants and other organisms can assimilate, e.g.
ammonia.
570. Nitrogen-fixing bacteria Microorganisms capable of fixing
atmospheric nitrogen into compounds that plants and other organisms
can assimilate. Bacteria can be free-living in the soil (e.g. Azotobacter)
or living mutualistically with plants roots (e.g. Rhizobium).
571. Nitrous oxide (NOx) a colourless, odourless greenhouse gas that
occurs both naturally and as a result of people’s activities. Major
sources include farming practices (such as using fertilizers) that add
extra nitrogen to the soil, burning fossil fuels, and certain industrial
processes.
572. Non-coding DNA components of an organism’s DNA that do not encode
protein sequences. Some non-coding DNA is transcribed into functional
non-coding RNA molecules while others are not transcribed.
573. Non-competitive inhibitor a molecule that binds to an enzyme at a
location outside the active site and inhibits the enzyme’s function.
574. Non-disjunction an error during mitosis or meiosis in which both
members of a pair of homologous chromosomes or both sister
chromatids fail to move apart.
575. non-disjunction meiosis in which there is a failure of paired
homologous chromosomes to separate
576. Non-polar amino acid an alpha-amino acid in which the functional
group (R-) attached to the alpha-carbon has hydrophobic properties.
577. non-sister chromatidsChromatids from opposite members of a
homologous pair. These cross over at prophase I.
578. Nucleic acids linear chains (DNA or RNA) of monomeric nucleotides,
whereby each monomeric unit is composed of phosphoric acid, sugar,
and nitrogenous base.
579. Nucleic acids biological molecules, such as DNA or RNA, composed
of nucleotides that control cellular functions and heredity.
580. Nucleic acids complex compounds found in all living cells composed
of bases, carbohydrates, and phosphoric acid. Nucleic acids in the
form of DNA and RNA control cellular function and heredity.
581. Nucleoid a region of the prokaryotic cell where DNA is located.
582. Nucleosome the basic bead-like unit of DNA packing in eukaryotes,
consisting of a sequence of DNA wound around a protein core
composed of eight histones.
583. Nucleosome structural unit of a eukaryotic chromosome,
consisting of a length of DNA coiled around a core of histones.
584. Nucleotides the building blocks of nucleic acids consisting of a
five-carbon sugar, a nitrogenous base, and a phosphate group.
585. Nucleotides the building blocks of nucleic acids consisting of a
five-carbon sugar, a nitrogenous base, and a phosphate group.
586. Nucleotides the building blocks of a nucleic acid, consisting of a
carbon sugar covalently bonded to a nitrogenous base and a
phosphate group.
587. Nucleus membrane-bound organelle found in eukaryotes that
contains DNA; it is the site of replication and transcription.
588. Objective lens the part of the microscope that gathers light from the
specimen and focuses it to produce a real image.
589. Oncogenes a gene that causes normal cells to change into
cancerous tumour cells.
590. Oogenesis the process of formation of female gametes.
591. Order a subdivision of a class, composed of one or more families
of organism.
592. Organelle a sub-cellular structure or membrane-bound compartment
with a distinct structure and function.
593. Oscilloscope an electronic instrument used to observe and measure
changing electrical signals.
594. Osmoconformers marine animals which, in contrast to
osmoregulators, maintain the osmolarity of their body fluids such that
it is always equal to the surrounding seawater.
595. Osmoregulation control of the water balance of a living organism.
596. Osmoregulator a body mechanism concerned with the maintenance
of constant osmotic pressure relationships.
597. Osmosis passive movement of water molecules from a region of
lower solute concentration to a region of higher solute concentration.
598. Osmosis net movement of water molecules through a semi-
permeable membrane from an area of higher water potential to an area
of lower water potential.
599. Osmosis the diffusion of fluid through a semi-permeable membrane
from a solution with a low solute concentration to a solution with a
higher solute concentration until there is an equal concentration of
fluid on both sides of the membrane.
600. Oxidation the loss of electrons or loss of hydrogen.
601. Oxidative phosphorylation the production of ATP through a series of
oxidation and reduction reactions.
602. Oxytocin a hormone released by the pituitary gland that causes
increased contraction of the womb during labour.
603. Ozone (O3)a gas made up of three atoms of oxygen bonded together.
High in the atmosphere, ozone naturally shields the Earth from harmful
ultraviolet radiation and closer to the Earth’s surface is a pollutant
that is formed by other pollutants that react with each other. Ozone is
also a greenhouse gas.
604. Pacemaker a specialized region of the right atrium that sets the
rate of heart contraction, also called the sinoatrial (SA) node.
605. Palisade mesophyll photosynthetic tissue below the epidermis in a
leaf.
606. Pancreas a gland in vertebrates, lying behind the stomach, that
secretes pancreatic juice into the duodenum and insulin and glucagon
into the bloodstream.
607. Pancreas a long, irregularly-shaped gland in vertebrates that secretes
pancreatic juice into the small intestine and insulin and glucagon into
the bloodstream.
608. Paramecium genus of single-celled ciliated organisms.
609. Parasitism Situation in which an individual organism, the parasite,
consumes nutrients from another organism, its host, resulting in a
decrease in fitness to the host as a result of the interaction.
610. Pathogen any organism that causes disease, such as a bacterium or
 fungus.
611. Pathogen an agent that causes disease or illness in another
organism.
612. Peat a compact, brownish deposit of partially decomposed vegetable
matter saturated with water, it found in uplands and bogs in temperate
and cold regions and used as a fuel.
613. Penicillin any of the antibiotic drugs obtained from penicillium moulds
or produced synthetically, most active against gram-positive bacteria
and used in the treatment of various infections and diseases.
614. Pentadactyl limb a limb with five digits, such as a human hand or
foot, which is found in many amphibia, reptiles, birds, and animals,
which can allow us to deduce that all species in these categories
derived from one common ancestor.
615. Peptide bond a covalent bond that joins amino acids, at the carboxyl
group of one amino acid to the amino group of the other amino acid,
with the release of a molecule of water.
616. Peptide bonds a covalent bond that joins amino acids, at the carboxyl
group of one amino acid to the amino group of the other amino acid,
with the release of a molecule of water.
617. Peripheral proteins proteins on the surface of the plasma membrane.
618. Permeability the rate of passive diffusion of molecules through the
membrane, which depends on the electric charge, size, and polarity of
the molecule.
619. Phagocytic white blood cells a type of white cell that carries
endocytosis of large foreign substances.
620. Phenotype the physical and physiological traits of an organism.
621. Phloem the food-conducting tissue of vascular plants that conducts
synthesized nutrients to different parts of the plants.
622. Phospholipid bilayer two layers of phospholipids arranged so that
their hydrophobic tails are projecting inwards while their polar head
groups are on the outside surfaces.
623. Phospholipids a lipid consisting of a glycerol bound to two fatty
acids and a phosphate group.
624. Phospholipids a lipid consisting of a glycerol bound to two fatty
acids and a phosphate group.
625. Phosphorylation the addition of a phosphate group to a molecule.
626. Photoactivation the production of energetic electrons in reaction
centers through the absorption of light.
627. Photolysis the splitting of water.
628. Photolysis of water chemical decomposition of water induced by
 light.
629. Photophosphorylationthe production of ATP using the energy of
sunlight.
630. Photosynthesis the production of carbon compounds in cells using
light energy.
631. Photosynthesis the process in green plants and certain other
organisms by which carbohydrates are synthesized from carbon
dioxide and water using light as an energy source.
632. Photosystem 1 an integral protein transport system used in the light-
dependent reactions – it can carry out cyclic photophosphorylation,
and produces reduced NADP.
633. Photosystem 2 the first photosystem in the light-dependent reactions
– it uses electrons from photolysis, and produces ATP.
634. Phylum a subdivision of a kingdom, composed of one or more
classes of organism.
635. Pilli extensions of the prokaryotic cell surface membrane used for
reproduction.
636. Pineal gland a small, cone-shaped organ in the brain that secretes
the hormone melatonin.
637. Pituitary gland an endocrine gland that secretes nine hormones that
regulate homeostasis.
638. Placenta a flattened circular organ in the uterus of pregnant
eutherian mammals, nourishing and maintaining the foetus through the
umbilical cord.
639. Plasma cell any of the antibody-producing cells, and derived from
B-cells. It plays a major role in antibody-mediated immunity reacting
with a specific antigen.
640. Plasma cell a fully differentiated B-lymphocyte (white blood cell)
that produces a single type of antibody.
641. Plasmid extra-chromosomal DNA in a prokaryote.
642. Plasmid the DNA of a prokaryote in the circular chromosome.
643. Plasmid the DNA of prokaryote in the circular chromosome.
644. Plasmid the DNA of prokaryote in the circular chromosome.
645. Plateau phase The population has reached the carrying capacity and
population growth ceases due to limited resources. Mortality and
death equal natality and Immigration.
646. Platelet a small fragment of red blood cells found in the blood
plasma that functions to promote blood clotting.
647. Pneumocyte one of the cells lining the alveoli (the air sacs) in the
lung that assists in gas exchange and in the secretion of pulmonary
 surfactant.
648. Point mutation the exchange of a single nucleotide for another in the
DNA sequence of a gene.
649. Polar amino acid an alpha-amino acid in which the functional
group (R-) attached to the alpha-carbon has hydrophilic properties.
650. Polarity property of having distinct and opposite charges (poles).
651. Pollination the process of transfer of pollen from the anther to the
stigma of a plant.
652. Pollutant Pollutant is a contaminant that causes adverse change to
an ecosystem or environment.
653. polygenic inheritance An additive effect of two or more gene loci on a
single phenotypic character
654. Polymer a compound made up of several repeating units
(monomers).
655. Polymer a large molecule consisting of many identical or similar
monomers linked together.
656. Polymerase chain reaction (PCR)a technique for amplifying DNA in
vitro.
657. Polymerase chain reaction (PCR)a technique for amplifying DNA in
vitro by incubating it with primers, DNA polymerase, and nucleotides.
658. Polypeptide a peptide, such as a small protein, containing many
molecules of amino acids, typically between 10 and 100.
659. Polypeptide a polymer of amino acids joined together by peptide
bonds.
660. Polypeptides a polymer of amino acids joined together by peptide
bonds.
661. Polypeptides a polymer of amino acids joined together by peptide
bonds.
662. Polypeptides a polymer of amino acids joined together by peptide
bonds.
663. polyploidy A chromosomal alteration in which the organism possesses
more than two complete chromosome sets. Found in plants
664. Polysaccharide a complex carbohydrate composed of a chain of
monosaccharides joined together by glycosidic bonds.
665. Polysome a group of ribosomes joined by a molecule of messenger
RNA containing the genetic information code that is to be translated
during protein synthesis.
666. Polysomes several ribosomes that are attached to the same mRNA at
one time.
667. Polyspermy an egg that has been fertilized by more than one
 sperm.
668. Polyunsaturateda type of molecule that contains more than one double
or triple bond in the carbon chain.
669. Population a group of organisms of the same species who live in the
same area at the same time.
670. Population a group of organisms of one species that interbreed and live
in the same place at the same time (e.g. deer population).
671. Positive feedback feedback in which the system responds to a
perturbation in the same direction as the perturbation.
672. Potometer a device used for measuring the rate of water uptake of a
plant due to photosynthesis and transpiration.
673. Presynaptic neuron a neuron from which an electrical impulse is
transmitted across a synaptic cleft to a postsynaptic neuron by the
release of a chemical neurotransmitter.
674. Primary structure the linear sequence or order of amino acids of a
protein; it determines how the protein will fold into a more advanced
structure, such as the unique three-dimensional structure of protein.
675. Primary succession Ecological succession on entirely new land
without any established soil (due events such as s volcanic eruptions
or glacier retreat).
676. Primer a segment of DNA or RNA that is complementary to a given
DNA sequence and that is needed to initiate replication by DNA
polymerase.
677. Producer (or autotroph) an organism that is able to form nutritional
organic substances from simple inorganic substances such as carbon
dioxide.
678. Progesterone a steroid hormone secreted by the corpus luteum of
the ovary and the placenta that acts to prepare the uterus for
implantation of the fertilized ovum, to maintain pregnancy, and to
promote development of the mammary glands.
679. Progesterone a steroid hormone secreted by the corpus luteum of
the ovary and by the placenta that acts to prepare the uterus for
implantation of the fertilized ovum and maintains pregnancy.
680. Prokaryote category of a cell without a membrane-bound nucleus:
archaea and bacteria.
681. Promoter site in a DNA molecule at which RNA polymerase and
transcription factors bind to initiate transcription of mRNA.
682. Prophase first stage of mitosis during which the chromosomes
become visible as paired chromatids and the nuclear envelope
disappears.
683. Prosthetic group the non-protein component of a conjugated
protein, for example the heme group in hemoglobin.
684. Protein organic molecule composed of polymers of amino acids
joined together by peptide bonds and taking a particular three-
dimensional shape.
685. Protein organic molecule composed of polymers of amino acids
joined together by peptide bonds and taking a particular three-
dimensional shape.
686. Proteome the complete set of proteins that can be expressed by the
genetic material of an organism.
687. Proton gradient a difference in proton concentration on either side of a
membrane.
688. Proximal convoluted tubulethe convoluted portion of the vertebrate
nephron that lies between the Bowman’s capsule and the loop of Henle
and functions especially in the reabsorption of sugar, sodium and
chloride ions, and water from the glomerular filtrate.
689. Pulmonary circulation the separated circulatory system that links
the lungs and heart in humans.
690. Pulse the force of blood leaving the heart in one heartbeat; it is
felt where arteries pass near the skin.
691. punctuated equilibrium Pattern of evolution in which long stable
periods are interrupted by brief periods of more rapid change
692. Punnett grid (or Punnett square) a tool that helps to show all possible
allelic combinations of gametes in a cross of parents with known
genotypes in order to predict the probability of their offspring
possessing certain sets of alleles.
693. Putrefaction Decomposition of organic matter by microorganisms.
694. Pyramids of energy a graphical model to show how the energy flows
through a food chain, how the amount of energy is decreasing and
becoming less available for organisms as it enters each trophic level,
and how much of the energy in the ecosystem is lost to the
atmosphere as heat.
695. Pyruvate the end product of glycolysis.
696. Quadrat sampling square or rectangular plot of land, a quadrat,
marked off at random to isolate a sample and determine the
percentage of vegetation and animals occurring within the marked
area.
697. Quaternary structure the particular shape of a protein defined by the
characteristic three-dimensional arrangement of its constituent
polypeptide subunits.
698. R group the chemical group attached to the alpha carbon in an
amino acid that is different for each of the common 20 amino acids
found in proteins.
699. Radiation energy that travels in the form of a particle or a wave and
exists in many different forms, such as electromagnetic radiation, X-
rays, ultraviolet radiation, infrared radiation, and visible light.
700. Radioactive element an element subject to spontaneous degeneration
of its nucleus accompanied by the emission of alpha particles, beta
particles, or gamma rays.
701. Random number generator A tool used to ensure unbiased sampling
points are chosen.
702. Random numbers a number chosen by a random sampling from a
table or generated by a computer.
703. Random orientation the orientation of homologous chromosomes in
the spindle axis during metaphase I is random and either maternal or
paternal homologue may orient towards a given pole.
704. random orientation the random position of each pair of
chromosomes in the nucleus when the spindle microtubules become
attached. Their random orientation will eventually result in which
chromosomes end up where.
705. Rate of photosynthesis the rate of conversion of carbon dioxide
and water to photosynthetic products.
706. Realized niche The part of fundamental niche that an organism
occupies as a result of presence of limiting factors in its habitat.
707. Recessive allele an allele that has an effect on the phenotype only
when present in the homozygous state.
708. recombinants Offspring whose phenotype differs from that of the
parents; also called recombinant types
709. Reduced NAD the energy rich form of the hydrogen carrier.
710. Reduced NADP produced by photosystem 1, it is an energy source for
the Calvin cycle.
711. Reduction the gain of electrons or gain of hydrogen.
712. Reductionism an approach to science that holds that a complex
system can be best understood as the sum of its parts, and that
variables can be studied in isolation.
713. Refractory period the delay after repolarization where the resting
potential is restored.
714. Replication fork a site on a DNA molecule at which the unwinding of
the helices and synthesis of daughter molecules are both occurring
during DNA replication.
715. Replication of DNA making a copy of a DNA molecule.
716. Repolarization the change in membrane potential that returns the
membrane potential to a negative value after the depolarization phase
of an action potential.
717. Repressor substance that binds to the operator and obstructs the RNA
polymerase from binding to the promoter and transcribing the gene.
718. reproductive isolationSeparation of species or populations so that they
cannot interbreed and produce fertile offspring
719. Reproductive status Whether an organism is capable of participating
in the process of reproduction.
720. rER rough ER – ER with ribosomes attached.
721. Resolution the ability to see adjacent objects or structures as distinct
from each other.
722. Respirometer apparatus for the measurement of respiratory gaseous
exchange.
723. Response in behavioural science, the behaviour that is the
consequence of a stimulus.
724. Resting potential the potential difference between the two sides of
the membrane of a nerve cell when the cell is not conducting an
impulse.
725. Restriction endonucleases an enzyme that cuts DNA at specific sites,
producing small fragments used in genetic engineering.
726. Rhodopsin a visual pigment consisting of retinal and opsin.
727. Ribose a monosaccharide (chemical formula C5H10O5) found in
RNA and other metabolically important compounds.
728. Ribosome organelle involved in protein synthesis.
729. Ribosome cell organelle functioning as the site of protein synthesis.
730. Ribosomes cell organelle that functions as the site of protein
synthesis.
731. Richness A measure of biodiversity based on the number of different
species present in a geographic region or ecosystem.
732. RNA a nucleic acid consisting of a long single-stranded chain of
nucleotides involved in protein synthesis.
733. RNA polymerase an enzyme that links together the growing chain
of RNA during transcription.
734. RNA polymerase an enzyme that links together the growing chain
of RNA during transcription.
735. Rubisco an enzyme that fixes CO2 to RuBP in the Calvin cycle.
736. Rubisco (ribulose carboxylase) is the enzyme that catalyses the first
step of photosynthesis (probably the most abundant protein on Earth).
737. RuBPthe molecule that reacts with CO2 during carbon fixation.
738. Saltatory conduction the propagation of action potentials along
myelinated axons from one node of Ranvier to the next node,
increasing the conduction velocity of action potentials.
739. Saprotrophs heterotrophs that obtain organic nutrients from
detritus by external digestion.
740. Sarcomeres the contractile units of a myofibril. Sarcomeres are
repeating units, delimited by the Z bands, along the length of the
myofibril.
741. Saturated fat a fatty acid with all potential hydrogen binding sites
filled.
742. Saturated fatty acid a form of fatty acid that lacks unsaturated
linkages between carbon atoms.
743. Saturated fatty acids a form of fatty acid that lacks unsaturated
linkages between carbon atoms.
744. Scale bar a means of visually indicating the magnification of an
image.
745. Scanning electron microscope an electron microscope that
generates a three-dimensional image.
746. Secondary consumer an organism that feeds on primary consumers.
747. Secondary structure the repetitive folding of the polypeptide
backbone of a protein due to the hydrogen bonds formed between the
peptides.
748. Secondary succession Occurs when succession starts on existing
soil following a natural or artificial disturbance.
749. Secretion when material is released from a cell.
750. Selection pressure an environmental variable that acts to remove
poorly adapted individuals.
751. Selective breeding the intentional breeding of organisms with
desirable traits in an attempt to produce offspring with similar
desirable characteristics or with improved traits.
752. Semi-conservative replication in the process of DNA synthesis each
original strands of the molecule acts as a template on which a new
complementary strand is created.
753. Semi-permeable membranemembrane that allows some substances to
diffuse through but not others. Transport pumps proteins in the plasma
membrane that use ATP to move substances across the membrane.
Vesicles a bubble-like membranous structure that stores and
transports cellular products.
754. Seminiferous tubules any of the numerous long convoluted tubules in
 the testes which are the sites where spermatozoa mature.
755. Sequencing of DNA to determine the order of nucleotide bases in a
DNA molecule.
756. sER endoplasmic reticulum that synthesizes new membrane and does
not have ribosomes attached.
757. Sex chromosomes the pair of chromosomes responsible for
determining the sex of an individual.
758. Sex-linked inheritance traits controlled by genes located on one
sex chromosome but not the other.
759. Sexual reproduction reproduction involving the union of gametes.
760. Shoot apex the tip of a shoot, the apical or lateral shoot
meristematic dome together with the leaf primordial, from which
emerge the leaves and sub-adjacent stem tissue.
761. Shoot apex the tip of a shoot, the apical or lateral shoot
meristematic dome together with the leaf primordial, from which
emerge the leaves and sub-adjacent stem tissue.
762. Sickle cell anaemia an autosomal recessive anaemia due to
substitution of a single amino acid (valine for glutamic acid)
characterized by red blood cell becoming sickle-shaped and non-
functional.
763. Sieve tubes an element of phloem tissue consisting of a
longitudinal row of thin-walled elongated cells with perforations in
their connecting walls through which food materials pass.
764. Sigmoidal growth curve A growth curve having a sigmoid or "S"
shape (sigmoid curve).
765. Simpson’s reciprocal index A index that can be used to measure the
biodiversity of an ecosystem.
766. Singer-Nicholson model current model of membrane structure that
incorporates a fluid mosaic structure in a discontinuous lipid bilayer.
767. Sister chromatids two identical strands of DNA joined by a common
centromere.
768. Sister chromatids replicated forms of a chromosome joined
together by the centromere and eventually separated during mitosis or
meiosis.
769. Sister chromatids replicated forms of a chromosome joined
together by the centromere and eventually separated during mitosis or
meiosis.
770. Small intestine the narrow, winding, upper part of the intestine where
digestion is completed and nutrients are absorbed by the blood.
771. Smallpox an acute, highly infectious, often fatal disease caused by a
 poxvirus. It is characterized by high fever and aches, and is believed to
have been eradicated globally by widespread vaccination.
772. Solubility the property of a substance of being soluble (dissolved).
773. Solvent a liquid in which substances (or solutes) are dissolved to
form a solution.
774. Somatic cell all body cells except sex cells (cells producing
gametes).
775. Spatial habitat The physical environment (i.e., the chemical resources
and physical conditions) of an organism or organisms.
776. speciation An evolutionary process in which one species splits into
two or more species.
777. Species groups of organisms that can potentially interbreed to
produce fertile offspring.
778. Species an individual belonging to a group of organisms (or the
entire group itself) having common characteristics and been capable
of mating with one another to produce fertile offspring.
779. Species a naturally interbreeding group of organisms with similar
morphology.
780. Species a group of related organisms that can successfully
interbreed in the wild.
781. Specific heat capacity the amount of energy required to raise the
temperature of water by one degree Celsius (water has to absorb 4.184
joules of heat for the temperature of one gram of water to increase by
1°C).
782. Spermatogenesis the production or development of mature
spermatozoa.
783. Spindle fibres network of filaments that collectively form a mitotic
spindle in mitosis. They are involved in moving the chromosomes
during nuclear division.
784. Spirometer an instrument for measuring the volume of air entering
and leaving the lungs.
785. Splicing of mRNA removal of introns from a primary transcript and
the subsequent joining of exons in the production of a mature RNA
molecule.
786. Spontaneous generation old theory that believed in the formation of
living organisms from non-living matter.
787. stabilizing selection Natural selection in which intermediate
phenotypes survive or reproduce more successfully than do extreme
phenotypes.
788. Staining treating (specimens for the microscope) with a reagent or
 dye that makes certain structures visible without affecting others.
789. Starch a polysaccharide carbohydrate (C6H10O5)n found in plants
that consists of a large number of glucose monosaccharides.
790. Starch a polysaccharide composed of glucose units that occurs
widely in plant tissues in the form of storage.
791. Stargardt’s disease a degenerative eye disease that has been the
target of stem cell research.
792. Stem the main body or stalk of a plant or shrub, typically rising above
ground, but occasionally subterranean.
793. Stem cell a relatively undifferentiated cell that can give rise to other
types of cells and retains the ability to divide.
794. Sterilization technique used for the elimination of microbiological
organisms to achieve a sterile microbial environment.
795. Steroids lipid-based hormones that are related to the four-ring
structure of cholesterol.
796. Stroma the chemical medium between the inner chloroplast
membrane and the thylakoid membrane.
797. Substrate the substance on which an enzyme works.
798. Substrate the substance that binds to the enzyme at the active site.
799. Sucrose a disaccharide composed of the monosaccharides glucose
and fructose.
800. Supercoiling twisting in the opposite direction to the turns of the
double helix during the first stage of mitosis.
801. Surface area to volume ratio a variable that decreases as cells
grow, so that it sets a limit to the size of cells.
802. Surface tension the force that causes the molecules on the surface of
a liquid to be pushed together and form a layer.
803. Surface tension (of water) the intermolecular hydrogen bonds
between molecules of water at the surface.
804. Surfactant a substance composed of lipoprotein that is secreted by the
alveolar cells of the lung and serves to maintain the stability of
pulmonary tissue by reducing the surface tension of fluids that coat
the lung.
805. Sustainable communities communities that are capable of being
maintained at a steady level without exhausting natural resources or
causing severe ecological damage.
806. Svedberg unit unit of molecule size based on the position that
material settles out in a centrifuge tube after spinning. Larger
particles tend to settle out faster and so have higher Svedberg values.
807. Symbiosis Literally "living together," a close association between two
 or more species.
808. Synapses the junction between two nerve cells, consisting of a
minute gap across which impulses pass by neurotransmitters.
809. synaptomenal complex where cross over occurs between two non-
sister chromatid to allow for cross-over
810. Synovial fluid the fluid found in joints like the elbow and knee, it is
contained within a membrane that lubricates the joint and allows
smooth and pain-free movement.
811. Synovial joint the most common and movable type of joint, which is
characterized by the presence of a layer of cartilage that lines the
opposing bony surfaces, as well as a lubricating synovial fluid.
812. System a level of organization that emerges due to the interaction
of elements.
813. Systemic circulation the separated circulatory system that links the
heart to the rest of the body.
814. Systolic pressure the maximum blood pressure caused by heart
muscles contracting and pumping blood.
815. T-lymphocyte a type of white blood cell that completes maturation
in the thymus and that has various roles in the immune system,
including the identification of specific foreign antigens in the body and
the activation and deactivation of other immune cells.
816. TagiaMoist subartic forest ecosystem dominated by conifer trees.
817. Tandem repeats copies of genes repeated one after another along a
chromosome.
818. Taq DNA polymerase a heat resistant enzyme found in the bacillus
Thermus aquaticus, which lives in hot springs, that can endure the
high temperatures of the polymerase chain reaction.
819. Taxon a group of species which shares and evolutionary
relationship.
820. Taxonomy the science of classification.
821. Telomere a region of repetitive nucleotide sequences at each end of a
chromatid that is involved in the replication and stability of DNA
molecules protecting the end of the chromosome from deterioration.
822. Telophase the final stage of mitosis in which the separated
chromosomes reach the opposite poles of the dividing cell and the
nuclei of the daughter cells form around them.
823. Terminator sequence of nucleotides that signals the end of
transcription or translation and the completion of the synthesis of a
nucleic acid or protein molecule.
824. Tertiary structure the irregular folding of a protein molecule due to
 the interactions of the R- groups involving hydrophobic interactions,
ionic bonds, hydrogen bonds, or disulfide bonds.
825. Testosterone a steroid hormone and the principal male sex
hormone.
826. Threshold potential the critical level to which the membrane
potential must be depolarized in order to initiate an action potential.
827. Thrombin a protease in blood that facilitates blood clotting by
converting fibrinogen to fibrin.
828. Thrombus a clot formed in the coronary arteries.
829. Thylakoid the membrane that is the site of photosynthesis.
830. Thylakoid space the lumen of the thylakoid.
831. Thymine an organic base found in DNA, but not in RNA, that pairs
with adenine.
832. Thyroid gland an endocrine gland at the base of the neck that makes
and stores hormones that help regulate the rates of metabolism,
growth, and development.
833. Thyroxin an iodine-containing hormone produced by the thyroid
gland, that increases the rate of cell metabolism and regulates growth,
and that is made synthetically for treatment of thyroid disorders.
834. Tidal volume the volume of air inspired or expired in a single breath
during regular breathing.
835. Tissue a group of cells with a common function and structure.
836. Top-down limiting factors Population growth pressures applied by
other organisms at higher trophic levels, e.g. predation.
837. Trachea thin-walled, cartilaginous tube descending from the larynx
to the bronchi and carrying air to the lungs.
838. Transcription when the DNA sequence of bases is converted into
mRNA.
839. Transcription the process of copying of DNA into messenger RNA in
gene expression.
840. Transcription process by which messenger RNA is synthesized from
a DNA template resulting in the transfer of genetic information from
the DNA molecule to the messenger RNA.
841. Transect A line or path along which the occurrences of studied
organisms are recorded.
842. Transfer RNA (tRNA) an RNA molecule that brings specific amino
acids that match the codons in the mRNA.
843. Transition state a state in which all of the original bonds are under
maximum strain resulting in an unstable intermediate.
844. Transitional phase Phase of population growth where the population
 continues to grow, but increasingly slowly as competition increases as
availability of resources are reduced.
845. Translation when the sequence of bases on mRNA is decoded into
an amino acid sequence (proteins).
846. Translation the transfer of information from a RNA molecule into a
polypeptide, involving the changing of language from nucleic acid to
amino acid.
847. Transmission electron microscope an electron microscope that
produces two-dimensional images.
848. Transparency property that allows light to penetrate molecules of
water.
849. Transpiration the loss of water by evaporation in terrestrial plants,
especially through the stomata (accompanied by a corresponding
water uptake from the roots).
850. Transport pumps proteins in the plasma membrane that release
energy and use it to move substances across the membrane.
851. Triglycerides an energy-rich compound made up of a single
molecule of glycerol and three molecules of fatty acid.
852. Triglycerides an energy-rich compound made up of a single
molecule of glycerol and three molecules of fatty acid.
853. Triose phosphate an intermediate in the Calvin cycle, also known
as glyceraldehyde-3-phosphate.
854. tRNA RNA molecules that transport amino acids to ribosomes for
incorporation into a polypeptide undergoing synthesis (according to
directions coded in the mRNA).
855. Trophic level the position in a food chain occupied by a group of
organisms with similar feeding modes.
856. Tropical rainforest A forest ecosystem with high rate of
precipitation and high humidity, usually located near the equator.
857. Tropisms the turning or bending movement of an organism or a part of
an organism toward or away from an external stimulus, such as light,
heat, or gravity.
858. Tropomyosin a muscle protein that binds to molecules of actin and
troponin to regulate the interaction of actin and myosin.
859. Troponin a complex of muscle proteins which, when combined with
Ca2+, influence tropomyosin to initiate contraction.
860. Tumours abnormal proliferation of cells, either benign or malignant.
861. Ultra sound treatment the application of ultrafrequency sound
waves to tissues in order to promote healing, break down substances,
and reduce pain and swelling.
862. Ultrafiltration a high pressure filtration through a semi-permeable
membrane in which colloidal particles are retained, while the small
sized solutes and the solvent are forced to move across the membrane
by hydrostatic pressure forces.
863. Ultrastructure the detailed structure of a biological entity.
864. Ultraviolet (UV) radiation a type of electromagnetic radiation, not
visible to the naked eye that is produced by the sun. Most UV radiation
is blocked by ozone high in the Earth’s atmosphere, but some of it
reaches the Earth’s surface and can lead to skin cancer and eye
damage.
865. Unsaturated fatty acid a form of fatty acid that contains more than
one double bond between carbon atoms.
866. Uracil a nitrogen-containing base found in RNA, but not in DNA,
that pairs with adenine.
867. Urea a molecule created from ammonia and carbon dioxide as the final
nitrogenous excretion product of many organisms.
868. Vaccine a preparation of a weakened or killed pathogen, such as a
bacterium or virus, or of a portion of the pathogen’s structure that
stimulates antibody production or cellular immunity against the
pathogen once administered, but is incapable of causing severe
infection.
869. Valine an essential amino acid occurring in proteins that replaces
glutamic acid in cases of sickle cell anaemia.
870. Valvea membranous structure in a hollow organ or passage that folds
or closes to prevent the return flow of the body fluid passing through
it.
871. Variation the range of phenotypes within a population.
872. Vasoconstriction when the circular muscles in the artery wall
contract, narrowing the lumen.
873. Vasodilation when the circular muscles relax, increasing the lumen
size and hence blood flow to downstream tissues.
874. Vein a vessel that returns blood to the heart.
875. Ventilation rate the volume of air passing into and out of the lungs per
minute.
876. Ventricles the chambers on the left and right side of the heart that
receive blood from the atria and contract to force it into the aorta and
pulmonary artery respectively.
877. Villus (plural villi) one of the minute finger-shaped processes of the
mucous membrane of the small intestine that serve in the absorption
of nutrients.
878. Viruses non-living biological entities that have infectious properties
– non-living pathogens.
879. Vitamin any of various fat-soluble or water-soluble organic
substances essential in minute amounts for normal growth and activity
of the body and obtained naturally from plant and animal foods.
880. Water tension the force created by evaporation of water coupled
with the cohesive and adhesive forces in plants, enough to support a
column of water against the forces of gravity in plants and trees.
881. Water vapour (H2O) water that is present in the atmosphere as a gas,
and as a greenhouse gas it plays an important role in the natural
greenhouse effect.
882. Waterlogged soil a soil that is soaked or saturated with water.
883. Wavelength the distance between peaks of a wave of light, which
determines its colour.
884. Wildlife corridor An area of habitat connecting wildlife populations
separated by human activities or structures.
885. X-ray diffraction an analytical method in which X-rays change direction
on contact with matter, resulting in changes in radiation intensity, that
is used to determine the three-dimensional arrangement of atoms.
886. Xylem the woody tissue which supports and transport water in
vascular plants.
887. Yeasts a unicellular fungus that lives in liquid or moist habitats.
888. Z lines a thin membrane in a myofibril, seen on longitudinal
sections as a dark line in the centre of the band. The distance between
Z bands delimits the sarcomeres of striated muscle.
889. Zone of stress The range of values of an abiotic factor that an
organism can survive but are not optimal.
890. Zooxanthellae Endosymbiotic algae that inhabit the endoderm of
tropical cnidarians such as corals, sea anemones, and jellyfish.
891. Zygotes the diploid product of the fusion of haploid gametes (a
fertilized egg).