BIOLOGY

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What is Biology?

‘Bios’ is a Greek term for ‘life’ while ‘logos’ is a Greek term for ‘study’. So Biology is the sub-discipline of science
that deals with the study of life and living organisms

BRANCHES OF BIOLOGY
Biology, like major sub disciplines of science such as Physics and Chemistry, has its branches. Here are some of
them

1. Microbiology - The study of organisms imperceptible to the naked human eye

2. Zoology - The study of the Animal Kingdom
3. Ecology - The study of the relationships between living organisms and their environment
4. Botany - The study of the Plant Kingdom
5. Biochemistry - The study nature and behavior of chemicals in an organism’s body
6. Genetics - This simply is the study of genes, how they differ from each other, and how they are passed
on
7. Anatomy - This branch of Biology deals with the structure of an organism and its parts and functions.
Human anatomy is referred to as physiology
8. Biotechnology - The broad study of how organisms can be used to make products that are of human
benefit
9. Taxonomy – This is the science of the classification of organisms

THE IMPORTANCE OF BIOLOGY

- Better understanding of our bodies
 Enables understanding of various illnesses and how to treat and diagnose them
 The study of Biology has career opportunities such as Pharmacology, Physiology, Veterinary medicine,
Agricultural Engineering etc.
 The study of Biology gives us insight to the past
 With Biology, we can understand environmental problems such as pollution and global warming and
therefore create solutions to these problems

LIVING ORGANSIMS
MULTICELLULAR AND UNICELLULAR ORGANSIMS
Multicellular organisms are organisms that are made up of multiple cells

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  Unicellular organisms are ones that exist as a single cell

CHARACTERISTICS OF LIVING ORGANSIMS

1. Movement: Living organisms can change their location and posture by themselves. Animals do this to
search for food, move away from danger, or to seek a mate. Plants seem to not move at all, but they move
slowly towards stimuli such as light

2. Respiration: Respiration is the decomposition process in which chemical energy is broken down from
glucose. Living organisms can respire, but need oxygen to do so, and therefore absorb the necessary
oxygen from their surroundings. Organisms that live on land have nasal organs that breathe in the oxygen
from the atmosphere, while underwater life use gills to acquire the oxygen they need from the water
dissolved with it.

3. Sensitivity: Living organism are able to detect changes in their environment and act towards them, and
this is what inspires movement in them. An example can be the wildebeest in the African jungle, it senses
a change in their environment (spotting a close by predator) and responds to it (evading away from the
predator). Almost all organism can respond to stimuli varying from light and heat to noticing a potential
mating partner

4. Growth: Growth is simply the permanent increase in size and mass of an organism, which is a
continuous process from the earliest stages of the organism’s existence to a certain point in its life (it
varies with the organism). In unicellular organisms, growth means the cell augmenting into a larger
structure, but as for multicellular organisms, they grow by increasing the number of cells in their bodies
and by means of cell division

5. Reproduction: All organisms reproduce. They can recreate life that is identical to itself either sexually
or asexually. This is done to ensure continuity in the existence of their species

6. Excretion: Excretion is the expulsion of unwanted material off the body. Animals in particular defecate
to remove food waste, urinate to expel toxins filtered by their kidneys, and exhale carbon dioxide which
is an unneeded by product of respiration.

7. Nutrition: All living organisms need to obtain the nutrients needed for their metabolism. Some
organisms are autotrophs, which means they create their own food using the abundant substances around
their environment as raw materials. Some are heterotrophs and rely on already-made food, most of which
was manufactured by the autotrophs. This isn’t it though, as some feed on dead organic matter. These are
saprophytes.

Non-living organisms are different because they do not have all or any of these characteristics

METABOLISM

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Metabolism is the sum of all processes that maintain the living state of an organism

Types of metabolic reactions

 Catabolism: a type of metabolic reaction that breaks down molecules into simpler entities and thus
releasing energy
 Anabolism: a type of metabolic reaction that binds molecules together into more complex structures and
use up energy in the process

THE MICROSCOPE
A microscope is a laboratory instrument used to examine objects too small for the naked eye to see

Parts of a microscope

i) Eyepiece lens
ii) Tube
iii) Arm
iv) Rotating nosepiece
v) Objective lens
vi) Rotating nosepiece
vii) Coarse adjustment knob
viii) Fine adjustment knob
ix) Stage clip
x) Light source
xi) Condenser lens
xii) Diaphragm
xiii) Base

https://www.microscopemaster.com/parts-of-a-compound-microscope.html

FORMULAE FOR MAGNIFICATION USING MICROSCOPE AND

MAGNIFYING GLASS
I. Microscope magnification

Magnification= objective lens magnification x eyepiece lens magnification

Magnification=measured size of specimen/actual size

Actual size= length of specimen x number on scale bar/ length of scale bar

II. Magnifying glass magnification

Magnification= length of drawing/ length of specimen

CELL STRUCTURE AND FUNCTION

What is a cell?
- A cell is defined as the smallest and the most basic unit of life responsible for all its processes

ORGANELLES IN A CELL

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The organelles in a cell are subcellular structures that have one or more functions in a living cell

1. The nucleus – This is the organelles that controls cellular activity. In its structure, it has a nuclear
membrane as an exterior. Its interior has parts like the nucleoplasm, a fluid filled part of the nucleus in
which chromatin, the protein structure that houses DNA and RNA, freely suspend. It is in the DNA and the
RNA where the cell’s genetic information is stored, which can be passed on as the cell divides,
2. The cell wall – Exclusive to plants, fungi, algae and cyanobacteria, it is a cellulose external structure
that provides shape, support, and protection to the cell. It is fully permeable and allows just about any
material to get through it
3. Lysosomes – It digests unwanted material off the cell. It can also destroy other cell organelles and
even the cell itself if need be by a process called autolysis. The lysosome is dubbed the cell’s “suicide bag”
because of this self-destruct mechanism
4. Golgi Bodies – A pile of cavities that store, sort and modify substances made by the Endoplasmic
Reticulum, packaging them into sites of reaction (mostly out of the cell) in vesicles. Scientists sometimes
dub it as the cell’s “post office”. Another reason it is called the “post office” also has the job of transporting
materials in and out of the cell
5. The cell membrane – This is a plasma membrane composed of phospholipids and has pores in it.
With this layer, a cell membrane can carry out its main function of sealing off the cell from the outside
environment and only allowing certain materials in (this is referred to as being semi-permeable). Small
molecules like those of water, oxygen and carbon dioxide easily get through the cell membrane, but as for
larger molecules, like those of urea for instance, they will need the help of carrier molecules
6. Ribosomes – They play a role of synthesizing proteins. They are more than 7000 ribosomes in a cell
7. Chromosomes – Located inside the nucleus, they contain the DNA of a cell and can determine the
sex of an individual. Each cell has 23 pairs
8. Cytoplasm – A jelly-like substances made up of water, organic and inorganic compounds which
surrounds most of the cell’s organelles and keeps various substances suspended in it which the cell and its
organelles will use later on
9. Mitochondria – The powerhouse of the cell which releases the stored chemical energy in
carbohydrates. This same energy is later stored in ATP molecules which power up most metabolic
reactions.
10. Chloroplast – This organelle contains the chlorophyll needed for photosynthesis
11. Endoplasmic Reticulum(ER) - a folded network of tubes attached to the nucleus. They are
classified into 2 types
A. Smooth ER – It contains no ribosomes to form protein synthesis. It therefore synthesizes fats, steroids
and detoxifies harmful substances
B. Rough ER – This type has ribosomes in its structure. With these ribosomes, it builds the proteins that are
to be transported to the Golgi bodies via the vacuole
12. Vacuoles – A vacuole is a fluid-filled membrane. Plant vacuoles store cell sap ( a solution of minerals
salts and sugars) while animal vacuoles store water and nutrients
13. Tonoplast – A membrane surrounding the plant cell’s large vacuole that separates the vacuole from
the cytoplasm
14. Centrioles – they play a role in cell division

THE DIFFERENCE BEWTWEEN ANIMAL AND PLANT CELLS

a) Animal cells have an irregular shape while plant cells have a more rigid form
b) Organelles such as the cell wall and the chloroplasts are present in plant cells but are absent in animal cells.

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 c) A plant cell has no centriole, while this exists in an animal cell
d) In a plant cell, a vacuole exists as one large space, while animal cells store nutrient material in smaller and
more numerous vacuoles
e) In an animal cell, the cytoplasm encompasses more space and has the nucleus at its centre. A plant cell on
the other hand, has its nucleus towards the edge of the cell and its cytoplasm doesn’t cover much space
compared to the animal cell’s cytoplasm

SPECIALIZED CELLS
- Most of the cells in an organism’s body are different and play roles needed in the survival of the organism
- To perform those tasks, they undergo cell specialization
- This is a process by which a cell is modified into a vessel that can carry out a special task

Examples of specialized cells are as follows:

1. Blood cells = there are two types of blood cells: white blood cells and red blood cells

A) White blood cells are cells designed to protect the organism from foreign materials. There are two types of
white blood cells, namely
i) Lymphocytes – They offer protection through secreting antibodies and antitoxins. They are
adapted to this by having a large nucleus and a thin cytoplasm
ii) Phagocytes – They destroy foreign material by engulfing and digesting the pathogen. They
are adapted to this by having a lobed nucleus, amoeboid movement and a cell membrane that
can mold into any needed shape

B) Red blood cells (erythrocytes) are blood cells adapted to nutrient transport by having a biconcave structure
and lacking a nucleus. This is so it can carry more content. It has hemoglobin which has a high affinity
level with oxygen. They are also tiny enough to fit in through capillaries to supply nutrients in other regions
in the organism’s body

2. Muscle cells (myofibrils) = Muscle cells are adapted to support movement and by having multiple
mitochondria. Actin and myosin help in the fiber contractions

3. Palisade cells = A palisade cell is specialized for carbohydrate manufacturing by having multiple
chloroplasts. It has a more cylindrical and horizontal shape in order to allow chloroplasts to move up and
down the cell for it to receive a proper amount of sunlight. This is because excess sunlight has a negative
effect on the chloroplasts

4. Root hair cells = Root hair cells have an elongated tube that increases the surface area for water to
diffuse into. It is concentrated with mitochondria as it requires energy to move water and minerals through
active transport. It has lost its chloroplasts for more vacuole space

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 5. Nerve cells = The main function of these cells is to transmit electric impulses as part of the nervous
system. Dendrites pick up impulses from the synaptic knob of the previous nerve cell, the axon transmits it,
the node of Ranvier speeds it up and the synaptic knob of the neuron passes it on to the next cell in line.

CELL ORGANIZATION IN MULTICELLULAR ORGANISMS

Cell Organization is the process where specialized

Tissue
Tissues are formed when a group of specialized cells come together. Examples of some are listed down below

A. Bone tissue – These tissues are in animal cells only. They support the structure of the animal and
store nutrients such as Calcium, Phosphorus and Vitamin D. These tissues also manufacture red blood cells
B. Nerve tissue – impulses from an animal’s brain are transmitted via these tissues
C. Palisade tissue – multiple chloroplasts are in these tissues thus making them the origin of the by-
products of photosynthesis
D. Xylem tissue – These tissue transport mineral salts and other nutrients from the root hair tissue
E. Phloem Tissue – This tissue is part of the transport system in plants. It serves as a passage for
substance absorbed by the plants roots, usually water and dissolved minerals
F. Blood tissue – These tissues move around nutrients, wastes, gases and many other chemicals via
blood vessel connected to almost every part of the animal’s body
G. Epidermal Tissue – Found on the outermost part of the plant surface, they cover and protect the
internal parts of a leaf and prevent water loss
H. Muscle Tissue – Muscle tissue form three types of muscle: skeletal muscles attached to the skeleton
for voluntary movement, cardiac muscle attached to the walls of the heart and smooth muscles on the walls
of most body tubes. Skeletal muscle contracts to produce movement stimulated by the motor nerves,
cardiac muscle contracts to pump blood from the heart to the body and smooth muscle contract to move
substances move through various body tubes, like those of the oesophagus
I. Epithelium – Made up of goblet and ciliated cells, it is found in the tubular structures of an animal’s
body. Its role is to move mucus that traps dust particles, pathogens and other unwanted material
J. Spongy Tissue -

Organs
Different tissues of different specialties come together and create an organ which performs one function. Examples
of organs are

A. Leaves – A leaf has mesophyll, palisade, epidermal tissue and transport tissue (phloem and xylem). This
makes a leaf an ideal location for photosynthesis
B. Liver – Liver stores

DIFFUSION, OSMSOSIS AND ACTIVE

TRANSPORT
DIFFUSION

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  Diffusion is the movement of particles from a region of higher concentration to a region of lower
concentration down a diffusion gradient
 Concentration is the quantity of particles in a certain area
 A concentration gradient is the difference in concentration

THE FACTORS AFFECTING THE RATE OF DIFFUSION

1) Size of particles: The smaller and lighter a particle is, the faster it will diffuse. The larger the particle, the
harder it is to move though concentration gradients
2) Temperature: When temperature increases, the kinetic energy in particles increases and therefore vibrates.
In the state of vibration, it can diffuse much easier than if it were vibrating less or if it was mot vibrating at
all
3) The Concentration gradient: the larger the difference in concentration, the more likely particles will diffuse
in the area of low concentration. This is in fact the core concept of diffusion
4) Thickness of Membrane: Thinner membranes support diffusion much better than thicker ones
5) Surface area to volume ratio: This means that a wider the membrane, the better it supports diffusion. This is
proven true by the fact that amoeba do not need a special transport system, after all, they have a larger
surface area

THE IMPORTANCE OF DIFFUSION IN LIVING ORGANISMS

a. The exchange of oxygen and carbon dioxide between the lungs and the circulatory system is a result of
diffusion
b. Oxygen in erythrocytes diffuse out of the cell towards body tissue by means of diffusion. The carbon
dioxide in cells moves into the deoxygenated blood erythrocytes also by diffusion
c. Metabolic wastes move out of the cell to the blood stream and exits out of the blood stream into the
excretory system by means of diffusion
d. Transpiration (the loss of water in plants) is a result of water diffusing from the air spaces in leaves to the
stomata
e. Plants use diffusion to get the carbon dioxide needed for photosynthesis. The oxygen that happens to be the
by-product of photosynthesis also leaves via diffusion
f. At night, plants gather the oxygen they need for respiration via diffusion

OSMOSIS
 Osmosis is the movement of a solute through a semi-permeable membrane from a higher concentration area
to a lower concentration area
 Water Potential is the tendency of water molecules to move from one solution to the other
 Water Potential can also refer to the level of water concentration in an area
 Water molecules in pure water have more water potential than those in a concentrated solution

THE EFFECT OF OSMOSIS ON A PLANT CELL

 If a plant cell were to be placed in a hypotonic solution (a solution less concentrated than the cell), the
cell’s vacuole will swell with water pushing towards the cell wall. The cell wall pushes back making it
turgid (stretchy but not breakable)
 If a plant cell were to be placed in a hypertonic solution (a more concentrated solution than the cell), water
will escape the cell, making the vacuole detach from the cell wall, which will leave it plamolysed
 An isotonic solution is a solution with just the same level of solute and solvent (water) in a cell
 A cell in an isotonic solution will be of equal water potential with its water surrounding

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THE EFFECT OF OSMOSIS ON AN ANIMAL CELL
 Once an animal cell is in a hypotonic solution, it absorbs more water and grows more larger
 Without a structure like a cell wall, the animal cell’s plasma membrane explodes. This is referred to as
cytolysis
 If an animal cell is in a hypertonic solution, it loses the water molecules inside it and it grows smaller in
size and spikier in shape. The cell has therefore shriveled or crenated
 An isotonic solution will allow equal water potential between the animal cell and the solution

ACTIVE TRANSPORT
Active transport is the movement of ions from a region of lower concentration to a higher concentration area against
the concentration gradient. It requires energy to do so, and this energy is supplied from living matter

Actions that involve active transport are:

 Root hair cells absorb minerals from the ground using active transport
 The villi in the intestine use active transport

ENZYMES
What are enzymes?
- Enzymes are biological catalysts. Catalysts are substances that speed up the rate of reactions without the substance
itself being changed

A chemical that reacts with an enzyme is called a substrate

The typical enzyme is characterized by…

 mostly being protein in nature

 being a catalyst
 being able to catalyze both forward and reverse reactions
 having its activity affected by temperature, pH levels, concentration of either substrate or enzyme, and
inhibitors or cofactors

HOW ENZYMES WORK

Enzymes speed up reactions by the Key-And-Lock Model. This is actually a theory which states that each enzyme is
in a structure that allows only specific substrates to fit through

The places in which substrates fit through are called active sites. It is this site where chemical reactions take place

FACTORS THAT AFFECT THE CHEMICAL RATE OF

REACTIONS IN ENZYMES
1) Temperature: Enzymes have an optimum temperature, the temperature at which enzymes work the
fastest, any less can slow down the rate of enzyme reaction and any higher can denature the enzyme which
makes it dysfunctional

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 2) pH levels: Some enzymes work best in low pH conditions, while others operate better in more higher,
alkaline conditions. Others may function well in a neutral state ( at pH level 7)

3) Concentration of Substrate: If substrate levels increase, then so will the rate of enzyme activity.
However, the reaction rate remains constant if all enzymes are occupied by substrate

4) Concentration of Enzyme: The more enzymes in an area, the faster the activity. If there are more
substrates to catalyze, the rate of enzyme activity remains constant and never changing until more
substrates appear

5) Inhibitors: An inhibitor is a chemical that slows down or stops the rate of reactions in an enzyme. There
are competitive inhibitors that bind onto the active site causing the site to take on a shape in which a
substrate can’t fit through. An uncompetitive inhibitor binds on the enzyme’s allosteric sites (any part
outside the active sites), completely misshaping the active site and potentially denaturing the enzyme

6) Cofactors: Cofactors improve the rate of enzymes. They can be considered as helper molecules. Among
cofactors, there are coenzymes and activators. Co-enzymes are organic while activators are inorganic

THE INDUSTRIAL APPLICATION OF ENZYMES

1. Biological Washing Detergents

Food stains, such as cooking oil, can be dealt with by ordinary detergents, but some stains, such as blood and
chlorophyll, prove insoluble by these detergents. Biological washing detergents have proteases in them that dissolve
even the toughest of stains

2. The Food Industry

A. Baking = Water, flour, sugar and yeast are the most basic ingredients when preparing any baked
product. Yeast produces an enzyme called zymase which decomposes the glucose in sugar into alcohol
and carbon dioxide. The carbon dioxide creates air bubbles causing the dough to rise
B. Sweeteners = The secret behind sweeteners is fructose. The enzymes glucose isomerase turns glucose
into fructose which has the greatest taste even in smaller amounts
C. Baby Food = Trypsin (a protease), is used to predigest high protein food that can be assimilated by a
digestive system as tender as that of a baby
D. Fruit Juice Production = Cellulase breaks down the cell wall of fruits cells which releases more juice.
The pectin in the juice is broken down by pectinase to create a less foggy effect. To put it simply,
cellulase and pectinase help in juice production by increasing juice yields and prevent jellying, which
is a result of the pectin in the juice that makes it foggy
E. Dairy Products = A protease named rennin clots milk together which turns it into either yogurt and
cheese

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 3. Leather Production

Leather has protein components in its structure, so trypsin is the ideal enzyme that can be used to tan leather.
Trypsin also digests the root hairs of some leather material.

NUTRIENTS
What are nutrients?
- Nutrients are chemical compounds in food that are essential to life
They repair damaged tissue, provide energy, protect against diseases and regulate chemical processes.
Metabolism can’t take place without a constant supply of nutrients

TYPES OF NUTRIENTS
There exists 6 nutrients needed by an organism, namely carbohydrates, lipids, proteins, water, vitamins and mineral
salts. Roughage is a nutrient but isn’t needed in the major metabolic processes of an organism

The nutrients along with their sources, are as follows:

1. Carbohydrates

A carbohydrate, also referred to as a saccharide or a sugar, is a compound made of carbon, hydrogen and oxygen.
There are three types of carbohydrates, which are

 Monosaccharides – These are sugars made of only one sugar unit, making them the simplest carbohydrate
types (in a way one could say they make up all other types of sugars). Glucose, fructose and galactose are
examples of this. Monosaccharides are usually soluble in water, taste sweet, and form crystals when
crystalized
 Disaccharides – These are sugars that have two sugar units. This is because they are the result of combining
two monosaccharides together, which can be separated if the disaccharides are hydrolyzed. Just like
monosaccharides, they are soluble, taste sweet and can crystalize. Sucrose, lactose and maltose are
examples of disaccharides
 Polysaccharides – These sugars are the result of many monosaccharides combining together. Because of
this, they have a complex chemical structure. Cellulose (the main component of a plant’s cell wall), starch
(a food storage molecule in plants) and glycogen (the food storage molecule in animals) are examples of
polysaccharides

These are found in plants and plant products. These are fruits and vegetables and other plant parts such as leaves,
stems and branches.

2. Proteins

Proteins are compounds containing carbon, oxygen, hydrogen and nitrogen, although some amino acids have
Sulphur and Phosphorus in their structure. The simplest form of protein is a monopeptide, or amino acid. When two
amino acids combine via the condensation process, they form a dipeptide. They can further combine with other
amino acids to form a polypeptide molecule, which is a chain of amino acids

There are ten types of amino acids and can be classified as either an essential amino acid (one that an organism’s
body cannot synthesize) or an non-essential amino acid (one that the body easily synthesize)

A protein can also either be a first-class protein, which is one that contains all the essential amino acids that exist in
nature. On the other hand, we have second-class proteins that lack one or more the amino acids

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Proteins can be sourced from animal products such as meat, milk, fish and eggs. Legume seeds such as those of
beans or groundnuts do contain protein products as well

3. Lipids

A lipid is a compound made of smaller units called fatty acids and glycerol. They don’t dissolve in water but do
dissolve in alcohol and organic solvents such as benzene and chloroform.

There are two types of lipids, oils and fats. Oils are in liquid form and are usually from plants while fats are in solid
form and are sourced from animals. Oils can become fats at low temperature and fats can become oils in high
temperature

Lipids can be found in vegetable oil, soybean extracts, some meats, milk and cheese. Fruits such as avocados, olives,
corn and nuts contain lipids as well

4. Water

Water is a compound made up of hydrogen and oxygen. Water can be found just about anywhere in the natural
environment or in foods that have been mixed with water, an example being tea, coffee or in most cooked food

5. Vitamins

Vitamins are organic compounds that animals and plants synthesize in small amounts. Some are soluble in water
(Vitamin B and C) while others (Vitamin A, D, E and K) dissolve in fats

Vitamin A, C, E and K occurs most in fruits and vegetables such as broccoli and cabbage while vitamins B and D
are from animal products(although vitamin B can be sourced from vegetables as well)

6. Mineral Salts

Just like vitamins, they are needed in small amounts but unlike vitamins, they are inorganic in nature. The most
common minerals are iron and calcium

Mineral are numerous and therefore have many food sources. However, most minerals are in fruits and vegetables

7. Fibre

Fibres, known as roughage, are food components that cannot be digested by animals. Most are made of cellulose, the
material that forms the cell wall of fungi and plants

Leafy vegetables are a good source of roughage. Cereals, fruits, grains and legumes also provide roughage

INVESTIGATING THE PRESCENCE OF NUTRIENTS IN FOOD

We use these various tests to demonstrate the presence of a specific nutrient in a piece of food
1. Iodine Starch Test
This test involves using the chemical element Iodine to test the presence of starch, a polysaccharide. Here
is how one conducts an Iodine Starch Test.
If the experiment sample is in powdered form, then add a little amount of the sample on a white tile and
then add a few drops of iodine (2 drops to be precise).
If the experiment sample is in solution or suspension form, then drop 2cm 3 of the sample solution into a
clean and dry test tube and add 2 drops of iodine solution

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If the sample contained no starch, then no colour change should be observed (the sample on its own is
usually yellowish to brownish, and therefore remains that colour)
If the sample did have starch in it, the Iodine solution should have changed its colour to a colour that
intersects blue and black
2. Benedict’s test for reducing sugars
Reducing sugars are all carbohydrates of monosaccharide and disaccharide nature in exception of sucrose,
it is a non-reducing sugar. The Benedict’s test is a way of finding out if it does have a reducing sugar
When conducting this test, the sample needs to be in solution or suspension form. If it is in solid form, it
should be dissolved into distilled water
With that done, add 2cm3 of the sample solution into a clean and dry test tube, and drop Benedict’s
solution on the same test tube thereafter. Shake the test tube and heat it on a water bath
If the mixture of Benedict’s solution changes to green, then there are little reducing sugars. If it turns
yellow, then there is a considerable amount of reducing sugars available, though not too much of it is
present. An abundance of reducing sugars turns it into red, orange or even brown. If no colour change is
observed (Benedict’s solution remains blue), then that means that no reducing sugars were ever present.
3. Benedict’s test for non-reducing sugars
The purpose of this is to find out whether there are any non-reducing in the sample. Non-reducing sugars
include sucrose and others of similar nature
Conducting the test for reducing sugars is a prerequisite for this test. One can only begin with this test if
the Benedict’s solution of the test for reducing sugars turned blue, which means there were no reducing
sugars in the sample
The test for non-reducing sugars begins by adding 2cm 3 of the sample solution onto a clean and dry test
tube. After that, one should add 1cm3 of hydrochloric acid onto the test tube with the sample solution and
heat the test tube for about 3 minutes and wait for it to cool
Once it has cooled down, a sodium hydrogen carbonate solution should be added to the test tube, which
will react with the already existing chemicals inside the test tube and create a fizzing effect. Wait until the
fizzing stops
Once this solution stops fizzing, add a volume of Benedict’s solution that is equal to the volume of the
solution that’s already inside the test tube. This new mixture should be heated in a water bath, and
observations are to be made in the process of the mixture heating
If after all this and the solution still remains blue, that means there were never any reducing sugars
present. But if it does change colour, especially the colours of blue, green, yellow or brick red, then this
solution has reducing sugars in it
4. Biuret’s Test for Proteins
This is a test that helps prove the presence of protein in a sample. Just like Benedict’s test for reducing
sugars, it will require a sample dissolved in distilled water to proceed with this experiment.

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To begin this experiment, one should add 2cm3 of the sample in its dissolved state into a clean and dry test
tube. Once that’s done, add about 7 drops of Biuret’s reagent. It should be added drop by drop, while
shaking the contents of the test tube
Biuret’s reagent is blue by colour, and if it doesn’t change colour after mixing it with the dissolved
sample, then there was no protein in the sample. However, if it does change colour, which is to a more
purple or violet hue, then there are proteins in the sample
5. Emulsion Test
The emulsion test is an experiment that helps to figure out if there are any fats in a sample. To begin, add
a small amount of the sample into the test tube and then add 2cm 3 of ethanol as well. After that, add a few
drops of distilled water into the test tube, which will result in a clear mixture of liquids
If this mixture remain clear, that means there was no fat in the sample, but if it turns cloudy, then the
sample contains fat in it
6. The grease spot test
Just like the emulsion test, it helps prove the presence of fat in a sample. For this test, add a small amount
of sample on a filter paper and then add a drop of distilled water directly to the sample. Next, the filter
paper should be put out to dry under the sun
Once the water that was added to the sample now evaporates, observations can be made. If the sample
disappears, then there were no fats in the sample, but if a greasy or oily spot forms, then fats are present
in the sample

THE IMPORTANCE OF NUTRIENTS TO THE BODY

1} Carbohydrates
 They store energy (by means of polysaccharides such as glycogen and starch)
 The also provide energy as they are the main reactant in respiration
 They provide energy needed for anabolic reactions

1} Proteins
 They are used in the creation and repair of body tissue
 Proteins are combines with other chemical elements to form functional units such as hormones,
enzymes, antibodies and substances like haemoglobin and fibrinogen
 It can be an energy source when the organism is in extreme conditions, such as illness or
starvation

2} Lipids
 They are waterproof
 Lipids form the walls of the cell membrane
 They store and release larger amounts of energy
 They form layers of fat around the organs for protection and under the skin for insulation

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 3} Water
 Water cools down the body by distributing heat from the body. The same heat causes it to
evaporate and leave the skin. This is how sweating occurs
 Water supports most chemical reactions in the body
 Water is needed to dissolve waste material from the kidneys into a liquid solution that can go
through the urinary tract
 Plasma, a major component of blood, is comprised mostly of water and it is necessary to
replenish this part of an animal’s blood

4} Vitamins
 They form the connective tissues of the body
 They function as co-enzymes
 Vitamin B6 and B12 help form blood cells
 Vitamins C helps absorb iron and maintain healthier tissue (better wound recovery and healthier
teeth and gums)
 Vitamin D helps absorb calcium
 Vitamin helps coagulate blood

5} Minerals
 Iron is needed to form haemoglobin that transports oxygen throughout the body within
erythrocytes
 Calcium builds better bones, better nervous transmission and supports muscle contraction
 Iodine helps in the production of thyroxin, a hormone that controls metabolic reactions such as
respiration
 Phosphorus is needed in the formation of the ATP and ADP molecule, the molecules that stores
energy released in respiration

6} Roughage
 Roughage keeps out harmful carcinogens out of the digestive tract
 They improve digestion and reduce the chance of one suffering from constipation
 They also keep the digestive tract clean and healthy
 Fiber regulates blood sugar and cholesterol in the body

MALNUTRITION
As previously mentioned, nutrients are needed in metabolism and other bodily functions. Malnutrition,
however is when one has an imbalance of nutrient intake in their diet. This leads to problems such as
obesity, starvation and deficiency diseases
I. Starvation
 This happens when one’s consumption of nutrient rich food is extremely low (especially in
energy-giving food)
 When one is starved, their bodies use less energy as possible (120g of glucose is normally used
but this turns into 30g)

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  Eventually, the body will run out of sugars, and will be in a state of ketosis
 In ketosis, fatty acids are broken down into ketones which will be used as a replacement for
glucose
 However, the brain can’t make use of these fats as well as it does with glucose this therefore
affects brain activity
 Once the body runs out of ketones, the brain absorbs muscle tissue to continue functioning (this is
called autophagy. Or cannibalism, if you will)
 Starvation weakens the immune system (due to lack of vitamins and minerals)
 If starvation continues after all this, death will occur, either from degradation of body tissue, loss
of energy needed for metabolism or from diseases (their immune system has grown too weak to
fight them off)

II. Obesity
 Obesity, on the other hand, is rather the opposite of starvation, as one’s diet has an excessive
amount of nutrient rich (mostly fat) food
 When one consumes food with fat, they supply their bodies with lipid, a compound that stores
energy
 The human body is adapted to storing energy, so these lipids form layers underneath the skin and
around organs
 More of this creates folds on the skin and can clog blood vessels
 This causes problems such as high blood pressure and other cardiac problems
 Excess fat can also lead to acne breakouts
 Clogged blood vessels supply an inadequate amount of blood to the brain leading to
psychological effects such as low self-esteem and depression

III. Deficiency Diseases

 Deficiency diseases happen when one lacks a certain nutrient in their diet
 Below are listed deficiency diseases

a. Marasmus – a lack of majority of the nutrients needed for survival, but is mostly caused by
the lack of carbohydrates and proteins. Proteins build up tissue while carbohydrates provide
the energy needed for metabolism. Without these, one may suffer weight loss, brittle hair, dry
skin and eyes, respiratory problems and so fourth

b. Kwashiorkor – Caused by a lack of proteins in diet

c. Rickets – A lack of Vitamin D and calcium in diet. Calcium is needed in better bones and
nerves while Vitamin D is needed for calcium absorption. Calcium and flaccid muscles,
deformed bones in the chest area and skull, and stunted growth are the effects of a shortage of
these nutrients. Bow legs are a lasting effect on children who suffered from rickets

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 d. Scurvy – A deficiency disease caused by a lack of Vitamin C. Without Vitamin C, connective
tissues won’t and

e. Anemia – A lack or iron in diet

f. Goiter – A lack of iodine in one’s diet

THE DIETARY NEEDS OF DIFFERENT PEOPLE
 A pregnant woman: a pregnant woman needs to add more Protein, Calcium, Iron and Vitamin D
to her diet. Proteins helps build tissue, iron creates haemoglobin, Calcium and Vitamin D helps
develop a better skeletal system
 A lactating mother: A baby’s digestive system can’t break down glucose well enough, so lactose
takes its place as an energy source for the newborn. A lactating mother therefore needs more
carbohydrates in her diet, but also proteins, calcium and vitamins
 An adolescent: Any child will have a growth spurt, a time in which metabolic rates increase,
affecting the growth of a child. Food rich in protein can help support metabolism of a high rate,
and also Calcium and Vitamin for bone development, and iron to produce haemoglobin needed in
transferring oxygen to support metabolism
 A sick person: One who is sick needs an extra intake of carbohydrates and proteins to quickly
undo the effects of the disease on their body. Vitamin C, the nutrient that boosts immunity, also
needs to be replaced. Other minerals such as Iron have to be replaced as well
 A manual worker: A manual worker uses a lot of energy, and so carbohydrates and lipids should
be a major part of their nutrition. They could also use protein for repairing the injuries that can
arise from their line of work
 An infant: An infant needs carbohydrates for energy, proteins to support growth, lipids for
healthy skin and minerals such as Zinc, Iron and Folate. All the vitamins will serve many
functions in the infants’ body, such as fighting infections, assist in converting food into energy,
and keeping the keeping the infant in perfect health
For more info: https:www.webmd.com/parenting/baby/nutrition

Plant Nutrition
MACRONUTRIENTS
 Macronutrients are nutrients that plant acquire in large amounts
 Nitrogen, Phosphorus, Phosphorus, Carbon, Oxygen, Hydrogen, Magnesium, Calcium and Sulfur
are micronutrients
 These chemical elements are acquired in vast amounts because they are important for a plant’s
metabolism

MICRONUTRIENTS
 Micronutrients are nutrients plants require in small amounts
 Manganese, Copper, Boron, Iron, Zinc, Molybdenum and Nickel are examples of micronutrients

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  Micronutrients are just as important as macronutrients, but are needed in small amounts. Larger
amounts can have a negative effect on the plant

THE EFFECT OF MACRONUTRIENTS DEFIECIENCY IN PLANTS

1} Nitrogen – Chlorosis in leaves, shrinked leaves and shortened internodes, and reduced plant vigor
(plant growth rate)
2} Phosphorus – The plant produces smaller leaves and shorter internodes, and already existing
leaves lose their green pigment for a more red, yellow or blue hue, appear near their main veins
3} Potassium – Leaves and stem are shortened, necrosis and chlorosis occurs, starting with the older
leaves, although this doesn’t happen to all plants
4} Magnesium – A reduction of plant vigor and leaf size, and interveinal and marginal chlorosis
happens uniformly to leaves of all ages and terminal leaves are stinted and deformed into a
triangular shape
5} Calcium – Small yellow lesions form on the basal half of the calcium-deprived leaf, and water
soaked spots appear on the chlorotic part of the leaf. This transfers on to younger leaves, and
chlorotic spots become necrotic which therefore abscises the new leaves prematurely
6} Sulfur – Chlorosis on new leaves occurs. Sulfur deficiency is rare and is confused with Nitrogen
deficiency as effects on pigment color (chlorosis) are similar in both nutrient deficiencies

THE EFFECTS OF MICRONUTRIENT DEFICIENCY IN

PLANTS
1} Manganese – Leaf deformation, chlorosis and stunted growth
2} Copper – Leaf distortion (leaves look dwarfed and sometimes have a hooked appearance) and
stunted, distorted and become more brittle and stiff
3} Iron – Iron-deprived plants have chlorsized leaves, but with different effect (and this is the most
common and unique symptoms of iron deficiency). While the rest of the leaf changes colour, the
veins of the leaf keep their pigment
4} Zinc – Zinc deficiency is known to occur on areca palms only, and no other plant. Chlorosis
happens uniformly to leaves to all ages, and terminal leaves are stunted and deformed into a
triangular shape
5} Molybdenum – Plant may be stunted, leaves are small and chlorotic, and leaf margins may
become scorched
6} Nickel – The tips of a leaf are necrotic and the entire leaf chlorosizes

LEAF STRUCTURE AND

PHOTOSYNTHESIS

THE STRUCTURE OF A LEAF

In order to survive, a plant needs to produce its own food by means of photosynthesis, and the leaf has
evolved to be the ideal organ which can accommodate this metabolic process

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This topic will separately discuss the external and internal structure of a leaf
1. THE EXTERNAL STRUCTURE OF THE LEAF
Looking at the diagram below, it’s easy to see that the external structure of a leaf has many parts. The
ones worth consideration are the lamina and the veins
 The lamina is the most visible part of the leaf. Its large surface enables it to trap more sunlight
and its thin surface allows easy diffusion of gases like oxygen and carbon
 The network of veins is made up of xylem and phloem tissue. The xylem transports nutrients to
sustain the leaf and the phloem transport the end-products of photosynthesis to nourish the rest of
the plant
 The midrib connects the stalk of the leaf to the leaf and is part of the leaf’s vein network. The
stalk hold the leaf away from the stem to receive more sunlight

2. THE INTERNAL STRUCTURE OF THE LEAF

Inside the leaf, beyond the surface of the lamina, is where the core mechanisms of photosynthesis exist.
The internal structure of a leaf has three parts, namely the upper epidermis, the mesophyll and the lower
epidermis
a. The upper epidermis
This part of the leaf’s internal structure is a layer of irregular cells closely packed together
covered by a waxy cuticle. This cuticle offers protection to the epidermis of the leaf and prevents
loss of water by means of evaporation

b. Mesophyll
The mesophyll has two specialized cells, the spongy cells and the palisade cells. Also the
mesophyll has gaps of space in which oxygen, carbon dioxide and even water reside, which
makes the mesophyll the largest portion of the leaf’s internal structure

c. The lower epidermis

Like the upper epidermis, the lower epidermis has a waxy cuticle that has packed irregular cells

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 covered by it. The difference however is the lower epidermis having stomata, encompassed by
two guard cells. The stoma and the guard cells are responsible for gas exchange in the leaf

d. The vascular bundle

this part of the leaf has the xylem and phloem, the transport mechanism in the entire plant. The
phloem transports the by-products of photosynthesis and the xylem transport nutrients from the
ground

PHOTOSYNTHESIS
What is photosynthesis?
It is the process in which plants make their own food with
Photosynthesis happens this way: water molecules extracted from the soil by the plant’s roots and carbon
dioxide molecules that diffuse into the leaf via the stomata are synthesized into glucose. This process is
powered by solar energy from the sun which is trapped by the green pigment called chlorophyll. All this
happens inside the chloroplasts of a Palisade Mesophyll cell or maybe any plant cell that has chloroplasts

LIGHT AND DARK REACTIONS OF PHOTSYNTHESIS

Photosynthesis is complete when both light-dependent (light) and light-independent (dark) reactions take
place.
It begins with the light-dependent reactions. This part of photosynthesis is mainly about photolysis, where
the light trapped in the chloroplasts separates water molecules into hydrogen ions and oxygen atom which
in turn generates ATP and NADPH. The Hydrogen ions, ATP and NADPH will be used in the dark
reactions of photosynthesis while the oxygen is released into the atmosphere
After this happens, the light-independent reactions begin. It starts with the process of carbon fixation,
where carbon dioxide is fixed into a more organic compound by ATP and NADPH. The fixated carbon
dioxide molecule now reacts with the hydrogen ions, forming PGAL, a component of glucose. Cobining
two molecules of PGAL forms glucose

UTILISATION OF PHOTOSYNTHESIS BY-PRODUCTS IN

PLANTS
Glucose, the by-product of photosynthesis, has many uses in the body. Some of these are:
 For respiration
 For amino-acid synthases (combining with nitrogen to create proteins)
 Conversion to fats, oils and nucleic acids
 For cell wall creation (glucose turns to cellulose)
 For manufacturing the energy-storage molecule starch

THE IMPORTNACE OF PHOTOSYNTHESIS IN THE ECO-SYSTEM

 All organisms benefit from glucose, the by-product of photosynthesis, which is part of the
decomposition process of respiration, the most important catabolic process in the body.
 The oxygen and carbon dioxide cycles are balanced by photosynthesis. The carbon dioxide is
used up and releases oxygen into the atmosphere

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  It creates the wood us humans use in our modern civilization for various purposes

STORAGE ORGANS IN THE PLANT

Depending on the plant, they may place the glucose created by photosynthesis in an organ of their
anatomy. We will explore the organs plants use to store food and what type of plant uses a specific organ.
 Root Tubers = These types of plants swells the lateral root with stored food. A sweet potato is an
example of this
 Stem Tubers = An Irish potato is a stem tuber as it swells its stem with stored food. This swollen
part of the stem is what is harvested for consumption
 Bulb = A bulb stores its food in fleshy leaves growing off of the plants’ stem. An onion is a
typical bulb plant
 Rhizome = These are plants with underground horizontal stems. The whole stem of the plant is
swollen with nutrients. The ginger plant is a rhizome
 Corm = These plants use the underground part of their stem to store food. The crocus plant is an
example of a corm plant
 Seeds = Plants may place their nutrients onto seeds to nourish the new plant that is yet to
germinate

SAPROPHYTIC NUTRITION
What is saprophytic nutrition?
- It is the type of nutrition in which an organism feeds on the organic matter of a dead organism. The dead
organism being fed on can be regarded as a substrate since extracellular digestive enzymes will break it
down into something that the organism can use in its metabolism
An organism that feeds this way is called a saprophyte. An example of a saprophyte can be the Rhizopus,
which we will discuss about later on

THE IMPORTANCE OF SAPROPHYTIC NUTRITION

Saprophytic nutrition is helpful in our ecosystem in these ways:
 Saprophytes feed on the dead organisms that could have accumulated our surroundings
 The organisms that depend on saprophytic nutrition recycle substances like carbon and nitrogen,
substances essential in our nutrition
 Heterotrophs like us humans use some saprophytes like mushrooms as food
 We also use saprophytes in food-preparing processes like baking and brewing

PARASITIC AND HOLOZOIC NUTRITION

These are other types of nutrition that other organisms take on. These are
1. Parasitic Nutrition
In this type of nutrition, an organism lives and feeds off of another organism, which is usually larger than
itself. An organism that feeds off another is called a parasite and the organism being fed on is called a
host. Some are endoparasites and live inside the organism, while others are exoparasites that feed on the

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exterior of its host. The process of the parasite feeding on the host, the host is harmed and can lead to
disease, physical injury, or even death
2. Holozoic Nutrition
An organism that feeds through holozoic nutrition has an alimentary canal and goes through the processes
of ingestion (Taking in food through an assigned bodily opening like a mouth), digestion (the breaking
down of food) absorption
3. Mutualism/Symbiosis
With this, two different organisms form a “partnership” in which one organism benefits the other, and
vice versa. Examples like these better explain the context:
 Nitrogen-fixing bacteria live inside legume plants. The legume provides a habitat for the bacteria
while the bacteria fixes nitrogen into a structure the legume can use in its metabolism. The
Nitrogen-fixing bacteria also benefit from the food the legume creates
 There is symbiosis between a sea anemone and a clownfish. The anemone provides a habitat that
can protect the clownfish from predators and offer the clownfish a place it can safely reproduce
while the clownfish lures in the anemone’s next meal (which is most likely a carnivorous sea
organism that sees the clownfish as prey)

THE STRUCTURE OF THE RHIZOPHUS

 The Rhizopus or Mucor is a saprophytic fungus that exists as a mold.
 It exists as threads called hyphae, the root-like hyphae are rhizoids and the horizontal looking
ones are stolons (a mass of hyphae is called a mycelium). Rhizoids and stolons release the
enzymes needed in their saprophytic nutrition
 The spore-bearing hyphae are called sporangiophores. They are called this because they have
spore cases called sporangia. Each sporangium contains numerous spores
 Spores are pretty much like seeds or a better analogy like pollen for the Rhizopus. They are
produced asexually and are a means of reproduction for the fungus

Animal nutrition
ANIMAL DENTITION
What is dentition?
- Dentition refers to the number, types and arrangement of teeth in an animal
Dental formula is the number and arrangement of human teeth according to type
Human teeth is comprised of 4 parts

 Incisors: This part consists of 4 teeth at the front of each jaw. As in the name description, it
incises a piece of a given food (as in biting off food)
 Canines: They are 2 in each jaw, making them 4 in total. As for us humans, we use them for
the same purpose as the incisors. But as for carnivorous animals, they are larger and sharper,
which helps them capture and kill their prey

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  Pre-molars: They are 4 on each jaw. They hold more force compared to the canines and
incisors, and therefore they grind the food torn by the incisors and canines
 Molars: They are 6 at the back of each jaw, and they are also referred to as Wisdom Teeth. Just
like premolars, they also crush and grind food torn by the incisors and canines

THE INTERNAL STRUCTURE OF THE TOOTH

The tooth of an animal is made up of the
I. Crown – This is the most outermost and exposed part of the tooth. With that said, the crown of
the tooth is made entirely of enamel, which apparently is the hardest substance that is part of the
animal’s anatomy. They are dead tissue, however, and cannot recover from external factors like
decay, and therefore must be taken care of. The shape of the enamel determines the role it will
play in an animal’s dental formula, either as an incisor, canines or the molars

II. The neck region – It’s practically the centre of the tooth in between the crown and root. These parts are
located in the neck region of the tooth
a) The gums = Its fleshly, pink connective tissue that is attached to the cementum and neck of the
tooth (the dentine and periodontal ligaments to be specific). It forms a line between the root and
crown of the tooth
b) The pulp and pulp cavity = This is the innermost part of the tooth. The pulp is the centre of the
entire tooth and is made of tiny blood vessels and nerve tissue needed for blood supply and
sensitivity. The pulp cavity is simply the space inside the crown of the tooth which is occupied by
the pulp

III. The root – This is the part of the tooth that extends into the jaw to hold the tooth in place. It has these parts:
a) The root canal = A passageway that contains pulp in it leading to the apical foramen. This canal
paves a path for brain signal to access the existing voluntary nerves and for a proper blood supply
b) Cementum = This is bone-like material that coats the root of the tooth, connecting it better to both
the periodontal ligament and the tooth socket
c) Periodontal membrane = It consists of periodontal ligament and collagen fibres store some blood
vessels and nerves. It helps teeth withstand the pressure of chewing food and also helps connect
the tooth to the jaw

THE DENTAL FORMULA OF VARIOUS ANIMALS

Dental formula is the number and arrangement of teeth according to type on one half of an animal’s upper and lower
jaw

The dental formula of various animals is shown below, including that of humans

2 1 2 3
Humans ¿ i c pm m
2 1 2 3
3 1 3 1
Cat = ¿ i c pm m
3 1 2 1
0 0 3 3
Cattle ¿ c pm m
3 1 3 3

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 1 0 0 3
Rat ¿ i c pm m
1 0 0 3
The dental formula depends on the diet an animal has. A carnivore for example, has adapted to its flesh-only diet
with longer and pointier canines which tear through flesh and suffocate their prey. They also have carnassial teeth
which is sharper upper premolars and sharper lower molars that work like the blades of a scissors to shear off flesh
from the bones

Herbivores also have teeth adapted to their diet. A typical herbivore has no upper incisors an instead has a horny pad
which work in conjunction with the lower incisors to grip and wrench vegetation. Another adaptation to their diet is
having a gap between the incisors and the premolar called a diastema. This is gap was meant to separate food that
has been bitten off the vegetation and one that is already being chewed

As for omnivores, they have no adaptation whatsoever to their diet as their diet

TOOTH DECAY
Tooth decay is a condition of the tooth enamel broken by lactic acid. This is caused when bacteria that formed a
habitat in one’s mouth feed on the food material found in the same mouth, especially sugary foods. On the process
of feeding on the food material, they ferment it into lactic acid

HOLOZOIC NUTRITION
What is holozoic nutrition
- It is the type of nutrition where food is taken in and processed internally inside the alimentary canal

The liver and the pancreas provide other chemicals to aid in digestion

Holozoic nutrition happens in five steps, namely

i. Ingestion – When food is inserted inside the body through the mouth
ii. Digestion – This is the breaking down of food into simpler parts
iii. Absorption – The intake of soluble broken down parts from the alimentary canal to the blood stream
iv. Assimilation – Making use of broken down parts for certain metabolic processes
v. Egestion – The expulsion of undigested food parts from the body to the outside environment

The alimentary canal is a system of organs working together to undergo 4 steps of holozoic nutrition. It is made of
three parts, which are

 The gastrointestinal tract, which a long body tube that transports food, from the animal’s mouth to its anus
 The accessory organs, which are the liver, the pancreas

Assimilation is done by the body

HOW THE ALIMENTARY CANAL PERFORMS HOLOZOIC

NUTRITION
The alimentary canal does the major steps of holozoic nutrition, and in this way:

INGESTION AND DIGESTION IN THE MOUTH

 Once the animal places the food in its mouth, the food has been ingested. Once it begins, it will be digested
both mechanically and chemically

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  When it undergoes mechanical digestion, it will be chewed or masticated by the crushing and grinding
action of the teeth. This increases the surface area for better chemical digestion and makes food more easier
to swallow
 While it is being mechanically digested, saliva, a mixture of water, mucous, and the enzymes amylase and
lysozyme will be mixed with the food by the rolling action of the tongue. Saliva is secreted by the glands
underneath the tongue
 The saliva in water help adjust the temperature of food, either extremely hot or cold, to one in which the
enzymes can work on. The mucous in saliva lubricates the food for easier swallowing.
 The tongue mixes the food and saliva with the help of the palate and once the food is mixed along with
saliva, it becomes a semi-solid mass called bolus
 At this point, it is ready to be swallowed

MOVEMENT OF FOOD DOWN THE GASTROINTESTINAL TRACT

 The oesophagus is the organ in the alimentary canal that accepts the bolus from the mouth and proceeds to
swallow it down to the stomach.
 It does this through a process called peristalsis, a process in which the circular and longitudinal muscles in
the oesophagus contract in a wave-like manner, which helps push it done further and further into the
stomach,

DIGESTION IN THE STOMACH

 The stomach which is a hollow, j-shaped organ with a muscular wall and a mucus lining. This is the organ
the bolus has been transported to by means of peristalsis. It will stay inside there for a while
 While it’s still in there, it will have mixed up with the gastric juices of the stomach. The gastric juices are a
mixture of hydrochloric acid, mucous, and the enzymes rennin, pepsin and lipase.
 Pepsin and rennin are first secreted in their inactive forms, which are pepsinogen and prorennin. The
hydrochloric acid in the gastric juices works to activate them into rennin and pepsin, which can be able to
break down the bolus
 The enzyme lipase breaks down fat into fatty acids, rennin breaks down caesinogen (a protein in milk) into
casein and pepsin breaks down proteins into simple peptides.
 The hydrochloric acid provides the optimum pH level for the enzymes to work on. It also hydrolyses
sucrose into fructose and glucose and kills any potentially harmful pathogens. The rugae has a layer of
mucous on top of it that protects the rugae and the rest of the stomach from the hydrochloric acid that is
part of the gastric juices
 For the best digestive efficiency, the gastric juices must mix with the bolus. To do this, the stomach will
mechanically digest it by rhythmically contracting the muscles of the stomach. Mixing gastric juices with
food material this way is called churning, and once this process is complete, the bolus becomes chyme
 After a while, the process of churning is complete and the bottom sphincter will open, allowing a passage
for the chyme to flow into the small intestines by means of peristalsis

NB: the sphincter is the muscular valve that is found on the tubes that connect the stomach to the rest of the
gastrointestinal tract

DIGESTION AND ABSORPTION IN THE SMALL INTESTINES

 Once the chyme reaches the intestines, it is mixed with the fluids secreted from the accessory organs. These
fluids are bile, which is secreted by the liver and stored in the gall bladder, and pancreatic juice, and as the
name implies, it is secreted by and stored in the pancreas
 The bile travels from the gall bladder to the duodenum through the bile duct. As for pancreatic juice, its
road from the pancreas to the duodenum is the pancreatic duct
 Bile contains sodium hydrogen carbonate, which neutralizes the hydrochloric acid that is part of the chyme
into a more alkaline condition, which is perfect for the enzymes that will later work on the chyme.

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  Bile also has bile salts which emulsify fats, in other words, turn large drops of fat into smaller ones, which
is more convenient for lipase as there is a larger surface area to volume ratio to work on. Bile also happens
to have a pigment, but it only has one job; which is to give faeces its colour.
 Pancreatic juice contains sodium hydrogen carbonate, and just the one found in the bile, it neutralizes the
acidity of the chyme. Sodium hydrogen carbonate is not the only thing that pancreatic juice consists of as
the enzymes trypsin, amylase and lipase are present. Trypsin breaks down protein and amylase breaks
down starch
 Once mixed with these juices, the chyme moves into the duodenum, which is the first part of the small
intestines, by means of peristalsis. After a while, it will leave the duodenum and further move down the
intestines into the jejunum
 Inside the jejunum, the chyme will be once again mixed with another fluid called intestinal juice or succus
entericus. This fluid has a wide array of enzymes contained in it. Peptidase, which mainly catalyzes
polypeptides into amino acids, and lactase that breaks down lactose into glucose and galactose are
examples of enzymes that the intestinal juices contain
 Once all these enzymes are done breaking down the nutrients they were designed to work on, the chyme
will move on to the ileum to be absorbed. At this point, the holozoic process of digestion is complete
 The digested food is now ready to be absorbed by the ileum, the final part of the small intestines. The
ileum has a large surface area and in fact comprises much of the small intestines. In this area, the
epithelium, attached to the walls of the intestine, have finger-like projections called villi, along with smaller
projections in them called microvilli. These absorb the nutrients that the body will assimilate.
 The villi are adapted to absorption by having lateral, which helps absorb fat. It also has a network of
capillaries which help absorb nutrients such as saccharides and amino acids. The villi is one cell thick,
which means it nutrients can diffuse easily into the lacteal and capillaries.
 Once absorbed, these nutrients will be transported to the liver and other parts of the body ny the hepatic
portal vein for assimilation

ASSIMILATION IN THE BODY

 For this process, nutrients are taken to either the liver or other parts of the animal’s body. Broken down
sugars in the form of glucose and broken proteins in the form of amino acids go to the liver, while broken
down fats in the form of fatty acids and glycerol go to other parts of the body
 Glucose will be used as a reactant for an important metabolic process, which is cellular respiration.
 There are times where there is an excess amount of glucose that the body won’t use yet, and when this
happens, the liver turns the leftover glucose into glycogen. About a third of this glycogen is stored in the
liver and the other two thirds is stored in the muscles.
 Amino acids will join back into proteins that will function in many ways in the body. Any excess of this
undergoes deamination in the liver.
 Deamination is the process where an amino group is broken down from the excess amino acids, which
turns it into a toxic substance called ammonia. This ammonia is further converted into urea, a less toxic
substance
 If left to accumulate, urea can intoxicate the liver. To avoid this, the liver will transfer it to the kidney by
means of the bloodstream. The urea is mixed with water and other metabolic wastes, which will be excreted
as urine
 The process of deamination leaves behind what is referred to as a carbon skeleton, which happens to be the
part of the deaminated amino acid that didn’t turn into ammonia. This carbon skeleton is converted into
glucose, under a process known as gluconeogenesis
 As for the fatty acids and glycerol, they will rejoin to form fat, just like how amino acids joined to form
protein. The fat will be used as an alternate energy source when all glucose and glycogen have been used
up, and also for forming part of the cell membrane.
 Excess fat is stored in adipose tissue, in the form of subcutaneous fat (fat stored in adipose tissue that form
a layer under the dermis of the skin) and visceral fat ( the fat stored in adipose tissue that surrounds delicate
internal organs)

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  Even after this, the process of holozoic nutrition is not complete, as egestion has to occur. This will take us
back to the alimentary canal

ABSORPTION AND EJESTION IN THE LARGE INTESTINES, RECTUM AND ANUS

 With all the digestion and absorption that took place in the small intestines, the only thing left of the food is
water mixed along with some minerals and fibres. These apparently were not digested and absorbed and
instead are transferred to the caecum, a part of the large intestines linked to the small intestines
 The caecum has a small projection under its base called the appendix. The appendix serves no special
purpose to the process of holozoic nutrition, although it is said to be a habitat for the microorganism that
live in the gastrointestinal tract. It is called a vestigial organ (an organ that lost its major use as an organism
evolved)
 From the caecum, the food moves to another part of the large intestines, called the colon. The colon works
to absorb the water via osmosis and the nutrients through various means. However, it absorbs the water and
minerals whilst moving through the colon by means of peristalsis. After this process of absorption, there
will be left an indigestible mass called feces
 The feces move to the rectum, ready to leave the body and enter the outside environment through the
holozoic process of egestion. This process happens through an opening linked to the rectum, called the anus
 After all this, holozoic nutrition is complete

AILMENTS OF THE ALIMENTARY CANAL

There are certain disorders or ailments that affect the alimentary canal. Once an animal experiences these ailments,
their digestion is impaired, which can be painful at times. The ailments that affect the alimentary canal or the
gastrointestinal juices include:

a. Diarrhoea: The releasing of watery stools or faeces. This might be caused by pathogens, poor absorption of
food and even allergies or intolerances to some foods (like how someone lactose intolerant ingests milk)
b. Constipation: This is a condition where one’s bowel movements feel uncomfortable or may not happen so
often, it’s sometimes a combination of both. Having a diet deficient in water and fibre or even resisting the
urge to defaecate can cause this.
c. Stomach ulcers: A stomach ulcer is a sore in the lining of either the oesophagus, the stomach, or the small
intestine. The production of gastric juice highly concentrated with pepsin and hydrochloric are a cause of
this ailment
d. Haemorrhoids: An ailment in which the blood vessels surrounding the rectum get swollen and eventually
burst, which stains the faeces with the blood that came out of the burst. Being constipated for too long and
too frequently can cause haemorrhoids

THE LIVER AND ITS AILMENTS

The liver is an accessory organ located right above the stomach in the alimentary canal. It is said to be the largest
organ in the body, and this might be because it has a lot of functions. Apart from deamination and gluconeogenesis,
the liver also…

 Turns old red blood cells into bile, which helps emulsify fats in the process of digestion
 Detoxify alcohol and other poisons. For example, a poisonous substance like hydrogen peroxide is turned
into water and oxygen by the enzyme catalase that mainly exists in the liver
 It stores some vitamins and minerals.
 Generates heat through a series of exothermic/endogenic reactions
 Synthesizes plasma proteins such as fibrinogen, prothrombin and albumin

Sometimes, the liver may not function well. This is because of an ailment, and these are:

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 a) Hepatitis: An inflamed liver
b) Hepatomegaly: a liver that is unusually large
c) Cirrhosis: An irreversible scarring and hardening of tissue

GASEOUS EXCHANGE
What is gaseous exchange?
- This is the exchange of gases between an organism and its environment. It is usually the diffusion of carbon
dioxide outside the bloodstream and the diffusion of oxygen into the bloodstream

HOW VARIOUS ANIMALS CARRY OUT GASEOUS EXCHANGE

Animals, depending on where they live or how they evolved, have different ways of undergoing the process of
gaseous exchange. Terrestrial animals like humans have a respiratory system, aquatic animals like fishes have gills,
insects have trachea and other organisms use their skin

THE HUMAN RESPIRATORY SYSTEM

 When air is inhaled, it passes through the nasal cavity, which has a layer of cilia and mucus that adjusts the
temperature of the air, as well as humidifying it and filtering it from dust and pathogens. This makes the air
more suitable for moving down further into the respiratory system
 Once the air passes through the nasal cavity, it moves into the pharynx, a passageway for both food and air.
The air encounters the epiglottis, an opening that closes during the swallowing of food, and it opens for it to
move to the larynx
 The larynx, or the Adam’s apple, is a part of the respiratory system which vibrates when air moves through
it, and humans use these vibration to form speech
 After moving through the larynx, it moves down the trachea. The trachea, or the windpipe, is a pathway
with rings of cartilage. Its rings of cartilage support the trachea and keep it open, which helps one breathe
in various positions, such as lying on the ground
 As the air moves down the trachea, it will encounter two pathways split form the trachea, which are both
called bronchi. Each bronchus is connected to the lungs, and as the air moves through the bronchus, it will
further split into smaller branches called bronchioles
 The bronchiole further branch down into alveolar ducts, each of which have an alveolar sac that contain a
number of alveoli.
 The alveolus is a gaseous exchange surface where the oxygen from the air moves into the capillaries
attached to the alveolus and the carbon dioxide from the blood in the capillaries moves into the alveolus.
 The carbon dioxide from the blood capillaries moves up the respiratory system, using the same path taken
by the inhaled air, and is exhaled out of the respiratory system through the nose
 There are muscles that support inhalation

AQUATIC RESPIRATION IN FISH

 Water in the sea and oceans has oxygen dissolved in water.
 Fish are adapted to this by having a respiratory system that is different from other organisms and is able to
extract the oxygen dissolved in water
 The fish ingest water by opening its mouth and allowing it to move into the buccal chamber. This chamber
works to push the water through the pharynx and into the gills, where gaseous exchange happens
 The gills are

THE COMPOSITION OF INHALED AND EXHALED AIR

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This table illustrates the gases that exist in both inhaled and exhaled air.

Gases Percentage Percentage in exhaled air

In inhaled air
Oxygen 21% 16%
Carbon dioxide 0.03% 4%
Nitrogen 78% 78%
Water vapour Variable Variable
Other gases In traces In traces

RESPIRATION
Usually, respiration has always been defined as the breakdown of foods like fats or sugars to release oxygen. But
this is cellular respiration, or internal respiration, which is only one part of the story

Respiration also involves how the needed oxygen is supplied to the body tissue, and this involves breathing and
gaseous exchange. The processes of breathing and gaseous exchange are what make up external respiration

There are two types of respiration, which are:

1. Aerobic Respiration
This is a form of respiration where glucose and oxygen are broken down in a series of reactions to generate energy.
All organisms can go through aerobic respiration, in exception of a few microbes
Aerobic respiration releases a great deal of energy (38 ATP) because the glucose molecule is fully oxidized

2. Anaerobic respiration
Also known as fermentation, it’s a type of respiration that also breaks down food to release energy, but without the
oxygen. There are two types of fermentation, lactic acid fermentation and alcoholic fermentation
In alcoholic fermentation, ethanol is released as a waste product of glucose undergoing a series of reactions to
release energy. Microorganisms such as yeast and some bacteria go through the process of alcoholic fermentation,
and release this waste to the outside environment
As for lactic acid fermentation, glucose is broken down for energy, releasing lactate in the process. While some
microorganisms undergo lactic acid fermentation, the muscle tissue of animals respirates anaerobically when under
strenuous physical activity.
The lactic acid that comes as a byproduct of generating energy stays in the muscles and can cause fatigue. To solve
this problem, the lactic acid must be moved out of the muscle tissue via the bloodstream. But the bloodstream is too
oxygen deprived to even do this. This causes heavy breathing to take place in order to pay an oxygen debt, which is
the amount of oxygen needed for the blood to transfer the lactic acid from the muscles to the liver, where it will be
turned back into glucose

Anaerobic respiration produces less energy than aerobic respiration, and this is because aerobic respiration involves
processes that help generate the most ATP, which anaerobic respiration lacks.

THE PRODUCTION OF ATP IN RESPIRATION

The whole point of respiration is breaking down food to release energy. But this energy is not used directly, it is
rather stored in a molecule called ATP (Adenosine Triphosphate). Respiration works to generate more of this
molecule. When the energy in ATP needs to be utilized, ATP loses a Phosphate group and becomes ADP
(Adenosine Diphosphate)

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As mentioned before, aerobic respiration breaks down glucose in a series of reactions. In this series of reactions, we
have glycolysis, a process where glucose is turned into pyruvate and some ATP. This pyruvate is oxidized into
acetyl CoA, which produces some carbon dioxide. Acetyl CoA will now undergo the Krebs cycle, and after this,
Acetyl CoA has been turned into NADH and FADH, which will support the next process of Oxidative
Phosphorylation.
This is a process where protons are pumped from one place to another. This needs the molecules NADH and FADH
to give away electrons to the five complexes that will take part in this process
In anaerobic respiration, glycolysis does take place, but without oxygen, The Krebs cycle can’t begin which means
even Oxidative Phosphorylation won’t happen. Since fermentation doesn’t have these processes, it must repeat
glycolysis over and over again to generate the needed energy

When glycolysis happens, where 1 molecule of glucose reacts with 2 molecules of NAD+ and ADP, along with 2
phosphate groups, to form 2 molecules of pyruvate and 2 molecules of NADH and ATP.

The pyruvate from this can either be decarbolised into acetaldehyde and be reduced to ethanol or straight away be
reduced to lactate. Both reactions help oxidize NADH into NAD+, which can be used to repeat glycolysis

If pyruvate is ultimately turned into ethanol, alcoholic fermentation has taken place. If pyruvate is instead reduced to
lactate, then lactic acid fermentation has taken place

The process of glycolysis generates 2 ATP, the Krebs cycle also generates 2 ATP, and Oxidative Phosphorylation
makes over 30 ATP. This means aerobic respiration creates lots more ATP than anaerobic respiration because of the
Krebs cycle and Oxidative Phosphorylation

THE PRODUCTION OF CARBON DIOXIDE IN RESPIRATION

Carbon dioxide is the by-product of respiration, aerobic or anaerobic. In aerobic respiration, carbon dioxide is
produced when pyruvate is oxidized into Acetyl CoA and is also a byproduct of the Krebs cycle

In alcoholic fermentation, pyruvate becomes acetaldehyde when a molecule of carbon dioxide is subtracted from it.
Pyruvate in this case has been decarbolised into acetaldehyde

Apparently, the process of lactic acid fermentation doesn’t have carbon dioxide as a byproduct

There is an experiment to show whether carbon dioxide is a byproduct of respiration, specifically aerobic
respiration. Here are the steps needed to conduct this experiment

Step 01:Set up three large bottles. Pour lime water into two of the bottles and place a small mammal inside the
remaining bottle. This could be a rat or hamster

Step 02:Have two glass tubes to connect each of the large bottles of lime water to the bottle with the mammal in it

Step 03: Connect the tubes in a way that one extends beyond the surface of the the lime water but as for the other, let
it only be above the surface of the lime water. The bottle with the extended tube will be bottle A and the one without
this extended tube is bottle C. The bottle with the mammal in it will be bottle B

Step 04:Observe what happens next

After a while, the lime water inside bottles A and C will have both turned milky. Lime water turns milky when
around a substantial amount of carbon dioxide, which we can speculate was released from the mammal breathing.
This goes on to show that carbon dioxide is a byproduct of respiration, and is released during breathing.

It is also worth noting that the lime water in bottle A got milky faster than the lime water in bottle C. This
observation proves that exhaled air is more concentrated with carbon dioxide than inhaled air.

THE IMPORTANCE OF RESPIRATION

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When organisms break down food to release energy, they help

 Support various processes that take place inside their bodies or even cells. These process include cell
division, protein synthesis, chromosome synthesis, and the growth of a cell
 In the contraction of skeletal, cardiac and smooth muscle. These support movement, digestion, excretion,
and heart rate
 Regulate body temperature
 In the transmission of nerve impulses
 Supports active transport

GOOD HEALTH AND DISEASE

What is good health?
- Health simply means one’s physical and mental wellbeing. With that said, good health means having a proper state
of mind and body.

What is disease
- A disease is a condition where one’s physical and mental functions are interfered, and usually has signs and
symptoms

A sign of a disease are indications of a disease that can be noticeable or measured. These include a rash, a loss of
weight or behavior such as intense scratching, shivering, sneezing and coughing

On the other hand, symptoms are indications of a disease that only the diseased person can feel and even describe.
This can include a type of pain, a rise or drop of temperature, a state of dizziness, or feeling nauseated

GROUPS OF DISEASES
Diseases can be categorized into two groups; ones that can be transmitted and ones that cannot be transmitted

1. Infectious Diseases
As the name implies, infectious diseases are the type of diseases that can spread from one person to another. The
reason for this is because they are caused by pathogens, or simply organisms that can infect other organisms, most of
which are microscopic. Pathogens can range from bacteria, viruses and protozoans to even fungi and worms

Diseases of this nature are transmitted through:

 Vectors, which are organisms that carry the disease-causing pathogens along with them. There are
mechanical vectors which accommodate the pathogens on the surface of their body and biological vectors
that accommodate the pathogen inside their bodies
 Inhaling air concentrated with infected air droplets a biological vector released when sneezing or coughing.
Pathogens that infect the vector’s respiratory system and cause disease such as tuberculosis, measles, and
influenza spread this way
 Ingesting food and drinking water contaminated with pathogens. The pathogens that cause cholera,
dysentery and hepatitis A and B are known for infiltrating the human body this way. Bilharzia and hook
worms spread mainly through water than food
 Engaging in the act of sexual intercourse with the vector. The HIV virus is well known to be spread
through this activity
2. Non-infectious Diseases
These diseases, unlike the formerly mentioned, are not spread from one person to another. They also are not caused
by any pathogen of any sort, and instead by a number of other factors. These factors are

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  Nutritional deficiency: Diseases like kwashiorkor, marasmus and rickets are caused by being deprived of
specific nutrients
 Genetics: Diseases like the sickle cell anaemia and haemophilia are inherited from one’s parents. Some
disease like albinism are the effect of having mutated genes
 Degenerative diseases: These come by when a part of one’s body experiences decline due to ageing or
overstressing the body part. Arthritis and coronary heart disease are examples of this
 Environmental Diseases: These diseases are the result of constantly intaking pollutants and other chemicals
harmful to the body. Environmental disease include bronchitis and emphysema

CAUSES, SIGNS AND SYMPTOMS OF CHOLERA, BILHARZIA AND MALARIA

Disease Causing Agent SIGNS AND METHOD OF METHOD OF CONTROL
SYMPTOMS TRANSMISSION
BILHARZIA Schistosoma  Aneamia Coming into  Proper and
 Tired contact with sanitary disposal
 Blood in crecaria larvae, of body waste
urine which are mostly  Treatment and
found in stagnant boiling of water
water. Even snails before use
can pass on this  Seek medical
pathogen as they treatment
serve a
mechanical
vectors
MALARIA The Plasmodium  Headache A bite from an  Seek anti
Protozoan  Anaemia infected female malarial drugs
 Shivering anopheles  Find measures of
and mosquito avoiding
sweating mosquito bites
CHOLERA Vibrio cholera  Nausea In taking  Quarantine of
 Diarrhoea contaminated patients
food or water or  Proper disposal
coming into of body waste
contact with a  Warming and
mechanical vector covering food
 Decontamination
with oral
rehydration salts

HIV and AIDS

HIV (Human Immunodeficiency Virus) is a pathogen that causes a disease called AIDS (Acquired
Immunodeficiency Syndrome). As the name of the virus implies, only humans can be affected by it

This pathogen is mainly transmitted when one comes into contact with the body fluids of the biological vector. This
can be through wounds, unclean syringes, mother to child transmission and sexual intercourse

THE EFFECTS OF HAVING MANY SEXUAL PARTNERS

Contracting AIDS is not the only problem that having many sexual partners can cause. Having many sexual
partners….

 Puts one at greater risk of contracting other sexually transmitted diseases except from AIDS
 Can cause unintended pregnancy
 Disintegrates families

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 IMMUNITY
What is immunity?
- The body's resistance to infection due to the presence of antibodies in the blood
There are two types of immunity: Active and passive. Active immunity is the type in which one’s body generates the
antibodies they need to fight infection. As for passive immunity, one receives the needed antibodies from another
source

Immunity can also be natural or artificial. Natural immunity means the person gained their immunity in a natural
way, such as after being a vector of a disease or receiving antibodies from their biological parents.

Artificial immunity means one gained their immunity through man-made methods, such as being vaccinated
weakened versions of a disease or ingesting a man-made substance that already contains ready-made antibodies

One’s immunity is determined by how many antibodies their bloodstream is concentrated with. One who is
passively immune has high immunity once they receive their antibodies, but because they are foreign to the body,
the antibodies are destroyed in the liver and spleen, which weakens one’s immunity until they received the antibody
again

LEVELS OF IMMUNITY
As for someone who is actively immune, they go through a primary and secondary response to antigens. A primary
response is the response it gives when being infected by an antigen for the first time, and it responds to this infection
by creating the needed antibodies for the antigen, which boosts its immunity

A secondary response is the response it gives once it gets infected by an antigen for a second time. In this case, it
creates even more antibodies than it did before, and this is because of the memory cells it created during the primary
response, which were meant to generate more antibodies when infected by the same antigen once again

FACTORS THAT AFFECT IMMUNITY

Immunity is important because with it, one can fight off infections

Immunity can be negatively affected by …

 A poor and inefficient diet

 In taking immuno-depressant drugs
 The attack of the HIV virus
 And pathogens developing resistance

GROWTH IN INSECTS
FLIES AND MOSQUITOES
THE LIFE CYCLE OF THE HOUSEFLY
 In the early stages of its life, a fly undergoes the process of complete metamorphosis. This is the type of life
cycle where in each stage of the cycle, it has a different morphology, it behaves differently and has
different nutritional needs
 It starts off as an egg laid in rotting material by its parent organism.

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  After 8 to 24 hours, it hatches into a larva (the common folk usually call it a maggot). This larva can ingest
the nutrients it needs to live through the cycle with its mouth. A larva is also able to move by using pads on
the lower side of its body
 After feeding for about 4 to 6 days, it has now become a pupa, and it cannot eat or even move. However, a
lot of metabolism goes on as it digests the food it is from ingesting, mostly rotten material
 The metabolic process the pupa is going through are supporting the development of an imago. After 3 or 4
days, it is fully developed, it emerges out of its pupa, breaking its exterior layer called the puparium.
 The imago looks like the smaller version of a housefly and will therefore have to grow in size to develop
into a full grown housefly. As it grows, it will also gain the sexual maturity it requires to reproduce
 After a period of about 14 days, it will have fully matured, both physically and sexually. It can now take
part in reproduction and lay eggs that will repeat the cycle

THE LIFE CYCLE OF A MOSQUITO

 Just like houseflies, mosquitoes are able to undergo metamorphosis. In fact, their life cycle is very similar
to that of houseflies
 First, a larva hatches off an egg laid by its parent mosquito in stagnant water. These larva are able to swim
inside the stagnant pool and feed on the phytoplankton and zooplankton they can find on the pool
 In less than 5 days, the larva becomes a pupa, and cannot move or eat at this point.
 Inside the pupa, an imago is developing, and after a few days, it will emerge out of the pupa as a fully
developed mosquito
 A male mosquito mainly feeds on plant juices, and so do female mosquitoes. But once the female mosquito
carries fertilized eggs in its body, it will seek animal blood to fully develop the eggs
 Once it has attained the needed blood, it will lay its eggs in stagnant water, and the larvae that will soon
hatch off the eggs will repeat the cycle

HOW HOUSEFLIES AND MOSQUITOES CAUSE DISEASE AND HOW TO PREVENT IT

1. Housefly

A housefly is a mechanical vector of pathogens responsible for cholera, dysentery and typhoid. The reason for this is
because of the environments where flies are usually found, such as unsanitary toilets, pit latrines and anywhere dirty
in general. With its ability to fly, it can efficiently transmit the pathogens on various surfaces they touch, including
food. Humans can potentially get sick once they ingest food touched by a fly

If the life cycle of the fly is controlled, then it is possible to prevent the spread of cholera, dysentery and typhoid.
We can do this by…

 Properly disposing of garbage and feces to reduce breeding sites

 Using insecticides to kill insects
 Capturing flies using fly taps
 Covering pit latrines

2. Mosquitoes

The female mosquito, especially the anopheles mosquito are biological vectors of the protozoan that causes malaria
and they transmit this protozoan to an animal by sucking its blood. Just like a housefly, a mosquito is able to fly, and
this makes the pathogen transmit much faster

By controlling its life cycle, we can prevent the transmission of malaria. We can do this by

 Draining stagnant water, where mosquitoes lay their eggs

 Dissolving insecticides into stagnant pools of water that can kill any eggs laid in the pool

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  Adding oil in stagnant water to block the oxygen supply needed to develop the eggs
 Instilling biological control in mosquito ( having a control agent reduce the population of the mosquitoes,
such as having a certain bacterium that would infect and kill mosquito larvae or an insectivorous organism
to eat the eggs

TRANSPORT IN PLANTS
THE STRUCTURE OF ROOTS AND STEMS
Plants need to transfer manufactured food, water, mineral salts and even hormones throughout their bodies for them
to metabolize efficiently. And so, they developed a vascular system to do just that, which consists of xylem, phloem
and cambium which forms a long tube called the vascular bundle. It begins from down the roots to the leaves on the
upper part of the plant

The xylem conducts mineral salts and water from the roots to the rest of the plant, and the phloem conducts food
manufactured from the leaves to the rest of the plant. The cambium, which is in between the xylem and phloem,
contains meristematic tissue that help in cell division

There are two parts of a plant, a root and a shoot. A root is under the soil while the shoot is above the soil. The way
the vascular system is arranged depends on whether the plant is a monocot or dicot and also whether the vascular
system is in the roots or in the stem of a plant, which is part of the shoot

Here’s a cross and longitudinal section of a dicot root and stem

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THE STRUCTURE OF THE XYLEM AND PHLOEM

THE ABSORPTION AND MOVEMENT OF WATER AND

MINERAL SALTS THROUGH THE ROOTS AND STEM
As mentioned earlier, the roots are the part of the plant underneath the soil. They have root hairs, which help absorb
the water and mineral salts found in the soil. Root hairs are made up of root hair cells, and these cells are properly
adapted to absorbing water through osmosis and mineral salts through active transport.

These adaptations include:

 An elongated outgrowth that allows the cell to have a larger surface area for water to diffuse into the
vascular system
 A lack of chloroplasts for an even larger diffusion surface area
 A lot of mitochondria to provide the energy needed to actively transport the mineral salts into the vascular
system
 Having a large vacuole which contains cell sap. This cell sap is made up of sugars and mineral ions, which
make the roots have a lower water potential than the soil, and this allows osmosis to occur

35
. Once absorbed by the root hairs, the water and mineral salts move into the xylem, via three routes, which are:

 The apoplast route, which is through the cell walls of the cells between the root hairs and the xylem
 The symplast route, which is through the cytoplasms of the cells between the root hairs and the xylem
 And the vacuolar route, which is through the vacuoles of the cells between the root hairs and the xylem

Once inside the xylem, the water moves through it from the roots to the leaves, and if forms a continuous stream
called the transpiration stream. Water is able to move through the xylem thanks to these mechanisms, which are…

a) Transpiration pull – The suction force created when water evaporates and diffuses outside the leaf through
an opening called the stomata. The transpiration pull exists because once water brought in by the xylem
moves out the leaf, more water will come to take its position in the leaf

b) Capillarity – The movement of water up narrow tubes such as the xylem due to adhesion and cohesion.
Cohesion is the force of attraction between molecules of the same kind, and adhesion is the force of
attraction between molecules of a different kind. With cohesion, the water molecules that move upward
will move along with the ones it has been attracted to. As for adhesion, it works well with narrow xylems

c) Root pressure – The pressure created when mineral ions pass through the xylem, which increases the water
potential in the roots, and makes osmosis possible

d) Guttation – This is a suction force created when plants loose water from the tips and margins of a leaf
called hydathodes

MOVEMENT OF FOOD ACROSS THE PHLOEM

Food moves from the leaves where it is manufactured (the source sites) to other parts of the plant where it is needed
(the sink sites) through the process of translocation, which occurs in the phloem.

Translocation begins when glucose, the product of photosynthesis is converted into the disaccharide sucrose in the
leaves and then moves into the phloem vessels. Once inside there, the phloem will transport from the leaves to other
parts of the plant. Amino acids also move from the source to the sink sites while dissolved in water

One thing to know is that the leaves are not the only source sites. Even food storage sites can play the same role. For
example, a root tuber such as a beetroot can have its roots be the source site for the process of transpiration

The process of translocation is mainly done with the help of active transport, because moving food from the source
to the sink sites requires energy.

TRANSPIRATION
Transpiration is the diffusion of water vapour from the leaves to the atmosphere through an opening called the
stomata. The water vapour was once water that was transported into the mesophyll cells of a leaf by a xylem vessel
and evaporated in the air spaces that exist in the internal structure of the leaf.

In the internal parts of a leaf, transpiration tends to happen more at the lower epidermis because the air spaces there
are larger and also there is also more stomata than the upper epidermis

FACTORS THAT AFFECT THE RATE OF TRANSPIRATION

The factors below affect the rate at which transpiration occurs

a. Humidity – Humidity is basically how much water vapour there is in the air. If the air is very humid, then
transpiration is less likely to occur, because the air is more concentrated with water vapour than the leaf.

36
 On the flip side, if the air is dry, then transpiration is more likely to occur, given the fact that the leaf is now
more concentrated with water vapour than the air around it
b. Temperature – How warm or how cool the air is has an effect on how likely transpiration takes place. This
is because a high level of kinetic energy in water molecules means it will evaporate faster, and with that
happening, there will be more water vapour transpiring out of the leaf
c. Light intensity – The amount of light present around the leaf determines whether the stomata are open or
closed. If there is more light, the stomata will open; and it there is a little light, then it will close. Light
intensity does affect the rate of transpiration because it determines whether the stomata, the main site of
transpiration, are opened or closed
d. Wind – Wind is simply moving air. If the air around the leaf is moving at great speeds, then it carries along
with it the water vapour around the leaf, and this affects the concentration gradient in a way that increases
the rate of transpiration, because the water vapour inside the leaf will move out of it, where it is less
concentrated. If there is a slow wind, then the opposite happens as water vapour will not diffuse out of the
leaf because outside the leaf is concentrated with water vapour

If the rate of transpiration is higher than the rate of water absorption, then this results in the plant wilting. Wilting is
a process where delicate parts of a plant such as the flowers or the leaves sag, because their cells are plasmolysed
due to the plant losing more water than it absorbs.

There are two types of wilting, temporary wilting and permanent wilting. Temporary wilting is wilting that can be
reversed if the plant receives more water for it to absorb and if possible, reduce the rate of transpiration of the plant.
As for permanent wilting, it is irreversible even if the ratio of water absorption to transpiration was controlled in a
way that would make its plant cells turgid

Here is a picture of a wilted plant

THE IMPORTANCE OF TRANSPIRATION

The process of transpiration is important to a plant, for these reasons:

LEAD ADAPTATIONS TOWARDS TRANSPIRATION

Although transpiration is an important process, it can lead to wilting, and permanent wilting can kill a plant.
Therefore plants are adapted to losing an amount of water that would still benefit them in the ways mentioned
above, and also avoid wilting. Its adaptations are:

 A thick, waxy cuticle that doesn’t allow any water out of the leaf except the stomata
 Hairs on the lower side of the leaf that capture escaping water vaporut
 Leaves that are needle shaped, that makes them smaller and less likely for water to transpire. They are also
able to roll up when water is scarce to avoid any more water loss
 Sunken stomata that are hollow enough to only let a certain amount of water vapour leave the leaf

BLOOD
What is blood?
- Blood is a body fluid circulated throughout the body that is made up of blood cells, platelets and plasma

Blood is made up of:

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 a. Red blood cells(erythrocytes) – These are cells that are the shape of biconcave disks, and contain
haemoglobin, a biochemical with a red pigment. In fact, this is what gives blood its colour . After being
created by either the bone marrow in adults or the liver in infants, they have a lifespan of 120 days, and
after that period, are destroyed in the liver.
b. White blood cells (leucocytes) – These cells are part of the Immune system, an organ system that works to
defend the body from any invading microorganism. Just like red blood cells, they are created in the bone
marrow, but also come from the lymphoid tissue, lymph nodes, tonsils, thymus and spleen. They come in
the form of phagocytes and lymphocytes
c. Plasma – This is basically water that has nutrients, metabolic wastes and other chemicals substances
dissolved in it. It contains these because it carries them from one part of the body to the other. It is the
reason blood is more liquid in nature, as it makes up 55% of blood.
d. Platelets – these are the remnant leftover parts that were from the manufacturing of red blood cells. They,
however, have a role: to clot blood. This will be discussed later on This is how it does this process:
 It first begins when the platelets at the site of injury release the enzyme thromboplastin, which breaks
down the plasma protein prothrombin into its active form, thrombin.
 Thrombin will then work on a plasma protein called fibrinogen, turning it into a more insoluble form
called fibrin, but will require some calcium ions.
 Fibrin will the form a mesh over the site of injury, and this mesh would block anything that tries to
leave the skin through the site of injury

FUNCTIONS OF BLOOD

Blood does a lot of things in the body as it is circulated throughout the body. To better explain how blood works, we
must refer to how each component of blood does its role. Below are the functions of blood

1. Red blood cells (erythrocytes)

 Carry oxygen from more concentrated areas to less concentrated areas with the help of haemoglobin, which
has a high affinity with oxygen. Haemoglobin is useful because when the erythrocyte is in the lungs (an
oxygen rich environment), it will combine with a surrounding oxygen molecule to become
oxyhaemoglobin. Once the erythrocyte is now at other parts of the body (an oxygen deprived environment),
the oxygen molecule will detach from it. in this way, it has been distributed from one place to another

2. White blood cells (leucocytes)

 They eliminate any foreign and invading microorganisms, or pathogens. They do this in different ways
through as phagocytes engulf and consume the pathogens by means of phagocytosis while lymphocytes
create antibodies and antitoxins that will effectively destroy the invaders
3. Plasma
 It dissolves the food absorbed by the ileum into the bloodstream to be assimilated by other organs in the
body
 It also dissolves in metabolic wastes such as urea and transport them to where they could be excreted
 It keeps hormones, plasma proteins and antibodies circulated throughout the body

BLOOD DDISORDERS

A blood disorder is a disorder that has to do blood and tissue components. Examples of these are…

 Leukemia, a condition where the patient makes an abnormal amount of immature leukocyte. It is also
referred to as the cancer of the white blood cells
 Haemophilia, an inherited disorder where one lacks the factor VIII and IX, which are essential for blood
clotting. As a result, the patient bleeds more blood than the average healthy person
 Sickle cell anaemia, which the result of inheriting a gene that makes red blood cell rigid and sickle shaped.
This sickle shaped erythrocyte is way less efficient in transporting oxygen than the normal disk shaped
erythrocyte, and this makes the patient feel fatigued easily than the average healthy person

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THE HEART

What is the heart?

The heart is a muscular organ that pumps blood throughout the body through red blood vessels

THE STRUCTURE OF THE HEART

In order to properly and efficiently do its job of pumping blood, the heart has been structured in a certain way.

The heart is separated into its left and right side by a wall Called a septum. Each side of the heart is further separated
into two parts, the top part being called the atrium and the bottom part being called the ventricle. The heart has not
been separated into four parts or chambers, two of them being atria and the other two being ventricles.

Every Chamber of the heart is connected by either an artery or vein, With the ventricles being connected to an artery
and the Atria being connected to a vein. Here are the names of the arteries and veins connected to the chambers of
the heart:

 The venacava, a vein which transports deoxygenated blood from the body to the right atrium
 The pulmonary vein, a vein that transports blood from

EXCRETION

What is excretion?

It is the expulsion of the toxic substance and the waste products of metabolism

An organ that initiates excretion is an excretory organ while the substances it removes during the process of
excretion are called excretory products

Excretion is very important because if the metabolic wastes and toxic material is not expelled from the organism's
body, then the organism will be affected, even killed.

THE KIDNEY

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