1 Characteristics and classification of living

organisms
1.1) Characteristics of living organisms
1.2) Concept and uses of classification systems
1.3) Features of organisms
Biology is the study of organisms. An organism is a complete living thing. Such as you and
me.

So, how do we know if it's a living organism? We use Mrs Gren

Movement An action by an organism or part of an organism causing a change

in position or place

Respiration The chemical reactions in cells that break down nutrient molecules
and release energy for metabolism

Sensitivity The ability to detect and respond to changes in the internal and
external environment

Growth A permanent increase in size and dry mass

Reproduction The process that make more of the same kind of organism

Excretion The removal of waste products of metabolism and substances in

excess of requirements

Nutrition Taking in materials for energy, growth and development

Organism A living thing

Dry mass The mass of an organism after it has been killed and water is
removed from it

The biological classification system

Common ancestor A species that lived in the past that has given rise to several
different species today

The smallest group of organisms biologist classifies are known as species. They provide
offspring that are fertile. Parents that are from different species produce an infertile
offspring
 Species A group of organisms that can produce a fertile offspring

Fertile Able to reproduce

Infertile Not able to reproduce

The binomial naming system

The first name is the genus while the second is species

Dichotomous key

Unit 1- Classification- Dichotomous key (with past paper questions)

Kingdoms

There are the animal kingdom, plant kingdom, fungus kingdom, protoctista kingdom,
prokaryote kingdom, fish kingdom

Animal kingdom ● Have a nucleus

● Feed on organic substances

Plant kingdom ● Have a chlorophyll

● Have cellulose
● Feed by photosynthesis
● Roots, stems and leaves

Fungus kingdom ● Multicellular

● Have nuclei and cell walls
● Don't have chlorophyll
● Feed by digesting organic material

Protoctista kingdom ● Multicellular and unicellular

● Have a nucleus
● Some feed by photosynthesis or
organic substances

Prokaryote kingdom ● Usually unicellular

● No nucleus
● Have cell walls
● No mitochondria
 ● Have a circular loop of DNA
● Often have plasmids

The animal kingdom (2)

● Their cells have nucleus but no cell wall or chloroplasts
● They feed on organic substances made by other living organisms

The plant kingdom (3)

● Their cells have a nucleus and cell walls are made from cellulose which contains
chloroplasts
● Feed by photosynthesis
● May have roots, stem, leaves

The fungus kingdom (4)

● Some may be multicellular and unicellular
● Have nuclei and cell walls made from chitin
● Do not have chlorophyll
● Feed on dead organisms
The protoctists kingdom (3) (mixed kingdom)
● Multicellular or unicellular
● Have nucleus and may or may not have cell wall and chloroplasts
● Some feed by photosynthesis and some feed by dead organisms

The prokaryote kingdom(6)

● Usually unicellular
● No nucleus
● Have cell walls made from peptidoglycan
● No mitochondria
● Have circular loop of DNA that is free in the cytoplasm
● Have plasmids

Groups within the animal and plant kingdom

Vertebrates group (animal) (4)
● They have backbones

Fish ● Scaly skin

● Gills
● Fins
● Eggs have no shells and are laid in
water

Amphibians ● Vertebrates with no scales but

smooth skin
● Tadpoles live in water
● Goes through metamorphosis

Reptiles ● Vertebrates with scaly skin

● Lay eggs with soft shells

Birds ● Have feathers

● Have a beak
● Have wings
● Lay eggs with hard shells

Mammals ● Hair on skin

● Young develop in a uterus, attached
to the placenta
● Have mammary glands
 ● Have different kinds of teeth
● Have a pinna (ear flap) outside of
body
● Have sweat glands
● Have a diaphragm

Key terms

Organic substances Substances whose molecules contain

carbon and is made from living things

Chlorophyll Green pigment found in plants that absorb

light energy for photosynthesis

Cellulose Carbohydrate that forms long fibers that

makes up the cell wall

Decomposers Organisms that break down organic

substances outside their bodies, releasing
nutrients for other organisms

Spores Very small groups of cells surrounded by a

protective wall

Multicellular Made out of many cells

Unicellular Made of a single cell

Pinna A flap outside of the body that directs sound

to the ear

Placenta Organ that connects the growing fetus to

the mother for exchange of nutrients and
waste substances

Mammary glands Only found in mammals that produce milk

to feed the young

Diaphragm Muscle that aids in breathing

Arthropods (No backbone) (Invertebrate)

● Several pairs of jointed legs

● Have an exoskeleton
Insects

● Arthropods with 3 pairs of jointed legs

● 2 pairs of wings
● Breathe through tracheae
● Divided to head, thorax and abdomen
● One pair of antennae

Crustaceans ● Arthropods with more than 4 pairs of

jointed legs
● 2 pairs of antennae

Arachnids ● Arthropods with 4 pairs of jointed

legs
● No antennae
● Divided to 2 parts, a cephalothorax
and abdomen

Myriapods ● Many similar segments

● All have many jointed legs
● One pair of antennae

Plant

Ferns ● Plants with roots, stem, leaves

● Don't produce flowers
● Reproduce by spores

Flowering plants ● Plants with roots, stem, leaves

● Reproduction using flowers and
seeds
● Seeds are produced in an ovary
Monocotyledon and dicotyledons (6)
 Dicotyledons Monocotyledons

Seeds with 2 cotyledons Seeds with 1 cotyledon

Network like roots Tap root

Network of veins Parallel leaves

Have flower parts in multiples of 4 or 5 Flowers in multiples of 3

Vascular bundles arranged in a ring Vascular bundles arranged randomly

Viruses
● Not living organisms
● Host in different organisms

2 Organisation of the organism

2.1) Cell structure
2.2) Size of specimens
Animal and plant cells

Cells The smallest units from which all organisms

are made
Cell membrane A very thin layer surrounding the cytoplasm
of every cell that controls what enters and
what leaves

Cytoplasm Jelly-like material in a cell where chemical

reactions happen

Mitochondria A small structure in a cell where aerobic

respiration takes place that releases energy
from glucose

Small vacuole A fluid-filled space in a cell that stores

nutrients or waste products

nucleus A structure containing DNA in the form of

chromosomes

Ribosomes Where protein synthesis occurs

Cell wall A tough layer outside the cell that allows

the support of the cell

Cell membrane A very thin layer surrounding the cytoplasm

of every cell that controls what enters and
leaves

Nucleus A structure that contains DNA in the form of

chromosomes

Cytoplasm A jelly-like material that fills a cell

Vacuole A fluid filled space inside a cell that stores

nutrients and waste products

Mitochondria A small structure in a cell where aerobic

respiration releases energy from glucose

Chloroplast Small structures found inside of the plant

cells where photosynthesis occurs

Ribosomes Where protein synthesis happens

 DNA A molecule that contains genetic
information in the form of genes, that
control how and what proteins are made

Chromosome A length of DNA found in the nucleus of a

cell that contains genetic information in the
form of many different genes

Nucleus A structure containing DNA in the form of

chromosomes that controls the activities of
the cell

Bacterial cells

Cell membrane A thin layer surrounding the cell that

controls the in and outs.

DNA DNA is a substance that contains genetic

information made from genes that encodes
for proteins

Cell wall A tough layer outside of a cell that supports

the cell
 Plasmid Small, circular molecules of DNA found in
many prokaryotic cells

Cytoplasm A jelly-like fluid that allows chemical

reactions to happen

Ribosomes Protein synthesis

Specialized cells

Ciliated cell Beats rhythmically to sweep mucus and

dust upwards

Neurone Conducting electrical impulses

Red blood cell Transporting oxygen

Sperm cell Male gamete in sexual reproduction

Egg cell Female gamete in reproduction

Root hair cell Absorption of water and mineral ions

Palisade mesophyll cell Photosynthesis

Order of cells

Cell A smallest unit an organism are made

Tissue A group of similar cells that work together

to perform a specific function

Organ A group of tissues that work together to

perform a specific function

Organ system A group of different organs that work

together to perform a specific function
 Organism A living thing
Sizes of specimens

1 micrometer = 1000 cm

3 Movement into and out of cells

3.1) Diffusion
3.2) Osmosis
3.3) Active transport
The particles are always moving. The higher the temperature, the faster they move. This is
because the particles have more kinetic energy at higher temperatures.

Diffusion is the movement of particles from high concentration to low concentration down a
concentration gradient to fill the empty space.

● Kinetic energy//energy of moving objects

● Diffusion//The net movement of particles from a region of higher concentration to a
region of lower concentration in a random movement
● Net movement//overall of average movement
● Concentration gradient//an imaginary slope from high concentration to lower
concentration

Diffusion in living organisms

● Air moving into the stomata in the leaf

● Oxygen diffusing into the cell

Osmosis

Osmosis is the net movement of water molecules from high water potential to lower water
potential through a partially permeable membrane.

● Compound//a substance formed by the chemical combination of two or more

elements in fixed proportions
 ● Partially permeable membrane//a membrane that lets some particles move through
it, but prevents others passing through
● Osmosis//the net movement of water molecules from high water potential to lower
water potential through a partially permeable membrane
● High water potential//region with high number of water molecules
● Low water potential//region with low number of water molecules

Osmosis in living organisms

● Water entering plant cells

● If a plant cell is in a liquid with very low water potential, water will travel out. This
causes the plant cell to be plasmolyzed
● If a plant cell is in a liquid with a low water potential, water will also travel out but not
alot, thus making the plant cell flaccid
● If a plant cell is in a liquid with very high water potential, water will travel in, making
the plant cell turgid

Plasmolyzed When a cell has its cell membrane pulled or

torn away from its cell wall

Flaccid When a cell is soft

Turgid When a cell is hard and firm

Plasmolysed A description of a cell in which the cell

membrane tears away from the cell
As an animal cell have a no cell wall, it can’t withstand high water pressure

● If an animal cell is placed in a liquid with high water potential, water enters and
causes the cell to burst (cytolysis)
● If an animal cell is placed in a liquid with low water potential, water leaves and
causes the cell to shrivel up

Active transport

Active transport is the movement of molecules or ions through a cell membrane from a
region of lower concentration to a region of higher concentration using energy from
respiration

Active transport and diffusion in living organisms

● Carrier proteins use energy from respiration to change shape to match the
molecule and move it out of the cell
● Channel proteins use diffusion to move substances in and out of the cell

4 Carbohydrates, fats and proteins

4.1) Biological molecules

Glucose Carbon, hydrogen, oxygen ● Stores as glycogen in

animals
● Stores as starch in plants

Protein Carbon, hydrogen, oxygen, ● Amino acids in body produce

nitrogen antibodies, keratin, enzymes

Fats Carbon, hydrogen, oxygen ● Stored as lipids

Carbohydrates

The simple types of carbohydrates with the smallest molecules are sugars.
 ● Carbohydrates//substances that include sugars, starch and cellulose, they contain
carbon hydrogen and oxygen
● Sugars//carbohydrates that have relatively small molecules, they are soluble in water
and they taste sweet
● glucose//sugars that is used in respiration to release energy
● glycogen//a carbohydrate is used as an energy store in animal cells
● Starch//a carbohydrate that is used as an energy store in plant cells

To detect the presence of starch, we can use iodine solution

● The color changes from brown to blue black if its positive for starch

To detect the presence of glucose, we use Benedict’s solution

● The color changes from blue to a range of colors to brick red if its positive for glucose

Fats and oils

Fats and oils are known as lipids

● A fat and oils is a lipid

● At room temperature, fats are solid
● At room temperature, oils are liquid
● Lipids are substances contain have Carbon, Hydrogen, Oxygen
● Emulsion//a liquid containing two substances that do not fully mix, one of them form
tiny droplets dispersed throughout the water

To test for fats or oils, we can use emulsion test

 ● The liquid changes from transparent to cloudy if there is a positive result for fats or
oils

Proteins

● Protein contains carbon, hydrogen, oxygen and nitrogen

● Protein molecules contain and is made out of many smaller molecules called amino
acids
● Proteins//a substance whose molecules are made of many amino acids linked
together, each different protein has a different sequence of amino acids

To test for proteins

● The color changes from blue to purple if there is a positive test for protein

The structure of DNA

DNA is the material that makes up our genes and chromosomes. It carries a code that

instructs the cell which amino acids link toget

her.

● DNA is made of smaller molecules called nucleotides

● Each nucleotide contains a base
● Each DNA contains two chains of nucleotides

Aidan Tan, Grace Chung

● Nucleotides//molecules that are linked together into long chains to make up a DNA
molecule
● Base//One of the components of DNA that determines the sequence of the proteins
made in the cell
● Complementary base pairing//the way in which the bases of the two strands of DNA
pair up; AT CG

5 Enzymes
5.1) Enzymes

Alimentary canal Part of the digestive system through which

food passes through from the mouth to
anus

catalyst A substance that increase the rate of

reaction, remaining unchanged

enzymes Proteins that are involved in metabolic

reactions to increase its speed
 amylase An enzyme that catalyzes the breakdown
from starch to maltose

protease An enzyme that catalyzes the breakdown

from protein to amino acids

catalase An enzyme that catalyzes the breakdown

from hydrogen peroxide to water and
oxygen

carbohydrates Enzymes that break down carbohydrates

lipases Enzymes that break down lipids

maltase Enzymes that break down maltose to

glucose

sucrase An enzyme that breaks down sucrose

substrate The substance that causes an enzyme to

react

How enzymes work?

● Every enzyme has a complementary active site to its substrate

Factors that affect enzyme activity

● pH and temperature

Where enzyme activity is the greatest is called an optimum temperature

Going beyond the optimum temperature will cause the enzyme to change its active site
shape, this is called denaturation.
 1. Random movement of substrate
2. Substrate collide and bind to specific complementary enzyme
3. Formation of enzyme substrate complex
4. Enzyme then catalyzes the reaction
5. Products are formed

Factors that affect enzymatic activity

Temperature ● Higher temp leads to more kinetic

energy
● More random collisions
● More enzyme-substrate complex
formed

pH ● Optimum pH keeps the site the same

shape
● More enzyme-substrate complex

6 Plant nutrition
6.1) Photosynthesis
6.1) Photosynthesis continued
6.2) Leaf structure
Plants can make their own food, this process is called photosynthesis

Photosynthesis The process by which plants synthesize

carbohydrates from raw materials using
energy from light
Chlorophyll is where photosynthesis occurs, it transfers light energy to chemical energy for
the synthesis of carbohydrates

● Glucose is too reactive to be transported around the plant, thus it gets converted to
sucrose initially

How does a plant use carbohydrates?

Releasing useful energy Respiration

Storing to use later Storage for cold winters

Making sucrose for transport

Making cellulose To build cell walls

Making nectar To attract pollinators

Making amino acids To make important proteins such as cells

Making other substances such as To make chlorophyll, etc

chlorophyll

What are the 2 elements you need to know at the IGCSE level that are essential for plants?

Element Nitrogen Magnesium

Mineral salt Nitrate ions Magnesium ions

Why needed To make amino acids, to then To make chlorophyll

make proteins and also aid in
making of chlorophyll

Deficiency Weak growth, yellow leaves Yellowing of leaves between veins

Nectar A sweet liquid secreted by many insect-

pollinated plants to attract their pollinators
 stomata Openings in the surface of the leaf and is
surrounded by pairs of guard cells that
decide when to open or close

Guard cells A pair of cells that surrounds a stomata and

control its opening and closing

Chloroplast

● Chloroplast can move around to get the best quantity of sunlight

● Many mitochondria to allow respiration

Factors affecting photosynthesis

● Supply of raw materials

● Quantity of sunlight
● temperature

Limiting factors

Limiting factors Factor that is in a short supply which

restricts a certain activity from happening in
a faster rate

Light intensity

As plants need light to photosynthesise, when light intensity increases, the rate of
photosynthesis increases until the plant is photosynthesising to its maximum, at this point,
the plant cannot photosynthesise more, why?

● The plant may be lacking a higher temperature

 ● The plant may be lacking more carbon dioxide

These are known as limiting factors as they are limited in supply they will limit the rate of
photosynthesis

Higher temperature

● As there are higher temperature, the faster it can photosynthesise, but when it
reaches its maximum, it reaches a point where there is either carbon dioxide or light
being limited
● But at one point, the rate of reaction would decrease as enzyme are denatured

Higher carbon dioxide

● As there are higher carbon dioxide, the faster it can photosynthesise, but when it
reaches its maximum, it reaches a point where there is either temperature or light
being limited
7 Human nutrition
7.1) Diet
7.2) Digestive system
7.3) Physical digestion
7.4) Chemical digestion
7.5) Absorption
The food an animal eats everyday is called a diet (6)

● Carbohydrates
● Proteins
● Fats
● Vitamins
● Minerals
● Water
A diet which contains all of these things is called a balanced diet

diet The food eaten in one day

Balanced diet A diet that contains all the nutrients in

suitable proportions and the right amount of
energy

Nutrients

Carbohydrates Needed for energy

Fats and oils Needed for energy, insulation

Proteins Build new cells, growth, make important

amino acids to form enzymes, antibodies,
etc

Vitamins
Vitamin C Formation of
collagen to avoid
scurvy

Vitamin D Helps absorption

calcium to avoid
rickets

Minerals
 Calcium To avoid brittle
bones

Iron To avoid anemia by

making hemoglobin

Fibre To avoid constipated and allow stimulation

of muscles to perform peristalsis

Water To allow chemical reactions to happen

peristalsis The muscles contracting rhythmically to

move food through the alimentary canal

The human digestive system

Digestive system A group of organs that carry out the

digestion of food

Liver A large red organ that carries out functions

such as productive bile and regulation blood
glucose concentration

Pancreas A creamy white organ that secretes

pancreatic juice, regulates blood
concentration
 Absorption The taking up or nutrients through the walls
of the small intestine

Ingestion Taking food and drink into the mouth

Digestion The breaking down of food

Absorption The movement of nutrients from alimentary

canal into the blood

assimilation The uptake and use of nutrients by the

cells, becoming part of the cells

egestion The removal of undigested food from the

body as feces

The alimentary canal

● A long tube runs from the mouth to the anus

● Lubricated with mucus to allow food to pass through tube
● Has sphincter muscles (close tube completely in certain places)

Anus The exit from the alimentary canal which poop is removed

Sphincter muscles Rings of muscle that can contract to close a tube

Lubricated Made smooth and slippery to reduce friction

Mucus A smooth viscous fluid secreted by many different organs in

the body

Goblet cells Cells found on the lining of the respiratory passages and the
digestive system that secretes mucus
The mouth

The salivary glands make saliva that helps digest food, lubricate food and allows it to form a
bolus that will slide down the esophagus

Ingestion mouth

Digestion Mouth, esophagus, stomach, small intestine

Absorption Small intestine, large intestine

Assimilation Liver, all organs of the body

The esophagus leading down from the back of the mouth to the
stomach

The stomach

The stomach has strong muscular walls that contract and relax
to mix the food with the enzymes and mucus

The small intestine

The small intestine is part of the alimentary canal between

the stomach and the colon, the small intestine specializes
in absorbing nutrients

Salivary glands Groups of cells close to the mouth which

secrete saliva into salivary ducts

Oesophagus Tube leading from mouth to stomach

Trachea The tube through which air travels to the

lungs as it has rings of cartilage to prevent
collapsing

Stomach A wide part of the alimentary canal that

food can be stored which digestion of
protein begins

Lumen The space in the center of a tube

Duodenum First part of a small intestine which

pancreatic duct and bile duct empty fluids

The pancreas and liver

The pancreas secrete a fluid known as

Pancreatic juice (ALT)

The liver secrete bile that emulsifies fat into

fat droplets

Small intestine A long narrow part of the alimentary canal

consisting of duodenum and ileum

colon The first part of the large intestine

ileum The second part of the small intestine

where absorption takes place

Pancreatic duct The tube that carries pancreatic fluid from

pancreas to duodenum
 Large intestine A relatively wide part of the alimentary
canal consisting of colon and rectum

rectum Second part of small intestine where feces

are produced and stored

bile An alkaline fluid produced by liver that

emulsifies fats to fat droplets

Gallbladder A small organ that stores bile

Bile duct The tube that carries bile from gallbladder

to the duodenum

Digestion

● Physical digestion (Large pieces of food are broken into smaller pieces done by the
teeth)
● Chemical digestion (Large molecules are broken down to smaller soluble molecules
that are absorbed)

starch amylase Simple reducing sugar

protein protease Amino acids

Fat lipase Fatty acids and glycerol

Teeth
● Used to bite of pieces of food to increase surface area

● Incisors are chisel shaped to bite off pieces of food

● Canines are used to tear of pieces of food
● Premolars allow grinding of food
● Molars allow grinding of food
 enamel Very strong material that covers the tooth

dentine Living tissue in a tooth

cement Holds the tooth in the gum

Incisors Allows biting off pieces of food

canines Tearing off pieces of food

premolars Grinding to increase surface area

molars Grinding to increase surface area

Chemical digestions

Amylase ● Salivary ● In the mouth Glucose

glands ● In the
● By pancreas duodenum
Protease (Pepsin and ● Walls of ● In the Amino acids
then Trypsin) stomach stomach
● By pancreas ● In the
duodenum
lipase ● By pancreas ● In the Glycerol and
duodenum fatty acids

Emulsification Breakdown of large drops of fat and oil into

smaller droplets to increase surface area of
breaking down

Gastric juice A liquid secreted by the walls of the

stomach that contains pepsin and
hydrochloric acid
 Pancreatic juice A liquid that is used to neutralize the
stomach acid and secrete the (ALT)
enzymes (Amylase, lipase, trypsin)

Absorption and assimilation

Assimilation The taking up of nutrients by the cells to be

used for living purposes, becoming part of
the cell.

● Villi are minute finger -like

projections of the walls of the
● small intestine (particularly the
ileum)
● Consists of blood capillaries and
lacteal
● Epithelium is one-cell thin
● Involved in absorption of
digested food substances
● Blood capillaries absorb glucose and
amino acids
● Lacteals absorb fats

● Glucose and amino acids are

absorbed directly into the
● blood capillaries found in the villi by
diffusion/active
transport
● Active transport occurs when the
concentration of
substances in the small intestine is
lower that the
● concentration in the blood
capillaries.
● Absorbed food substances are
transported by the hepatic
portal vein to the liver before they
are
distributed to the
rest of the body by the circulatory
system.

Villi
The inner wall of the small intestine that
contains projections

● Allows breaking down maltose to

glucose
● Absorbs glucose, amino acids, fatty
Acids, glycerol, vitamins, mineral ions,
Water

villi Very small finger like projections that line

the inner surface and increase the surface
area

microvilli Tiny folds on the surface of the cells in the

epithelium of the villi

Hepatic portal vein Blood vessel that carries blood from small
intestine to liver

epithelium One cell thick to maximize absorption

Goblet cell Secrete mucus

lacteal Absorbs fatty acids and glycerol which is

then eventually empties to the blood

Blood capillaries Absorb amino acids, glucose, vitamins,

mineral ions

Adaptations of small intestine Adaptations of villi

Long and coiled Increases the time One cell thick Reduces diffusion
for absorption distance

Numerous folds Increases surface Richly supplied with Allow a steep

area of absorption of blood capillaries concentration
digested food gradient
 molecules

Each villi has Increase surface

microvilli area of absorption

Fat metabolism

Digestion of fats
● Produces bile in gallbladder
● Bile emulsifies fats into fat droplets to increase surface area
● Lipase then acts on the fats droplets

8 Transport in plants
8.1)Xylem and phloem
8.2)Water uptake
8.3)Transpiration
8.4)Translocation

Plant transport system

Xylem A plant tissue made up of dead, empty cells

joined end to end in a continuous tube to
transport water and mineral ions to support
the plant

Phloem A plant tissue made up of living cells joined

end to end to transport substance sucrose
and amino acids

Xylem functions
 ● Transports water and mineral salts from the roots up the xylem to the leaves
● Provides structural support to the plant

Dead, hollow, continuous tubes with empty ● Reduces resistance to water flow
lumen through the xylem vessel/enable
water and mineral salts to move
easily through lumen without
obstruction

No cross walls in xylem cells ● Reduces resistance to water flow

through the xylem vessel, enable
water and mineral salts to pass
through without obstruction

Xylem vessel walls are thickened with lignin ● Lignin strengthens xylem vessel and
prevents collapsing

Narrow lumen ● Allows fast movement of water and

mineral salts via capillary action

Phloem functions

● Transport of sucrose and amino acids from the leaves to the plant

Single row of elongated thin-walled living ● Reduce resistance to the transport

cells flow to manufactured food

Pores in the cross walls separates the cells ● Prevent the oozing out of sugars
● Allow rapid flow of food substances

Narrow thin walled cell with nucleus and ● Provide energy required for
cytoplasm companion cells
● To carry out metabolic reactions to
keep the cell alive
 Root hairs is elongated ● Increases surface area to absorb
water and mineral salts

Contains sap vacuole ● Lowers water potential by osmosis

Cell membrane prevents cell sap from ● Maintains the lower water potential
leaking out of the root hair cell to allow entry of
water via osmosis

Large central vacuole ● Stores large amount of water

Contains mitochondria ● Release energy during cellular

respiration to allow active transport
of ions

Intake of water

● The sap in the root hair cell has a relatively concentrated solution of sugars thus it
has a low water potential
● Water enters the root hair cell via osmosis through a partially permeable membrane
down a water potential gradient
● Water enters the root hair cell, cortex then the xylem
● It then travels to the mesophyll cells and its then used for photosynthesis
● Some water vapor on the mesophyll then evaporates to the air spaces and escape
via transpiration
 Transpiration Loss of water vapor from leaves through
diffusion out from the stomata

Transpiration stream is when water is constantly taken from the top of the xylem vessels to
supply the cells in leaves, thus there is a pressure on the top so water flows up this process
is known as transpiration pull (Just imagine a straw)

Transpiration pull The force produced by the loss of water

vapor which reduces the pressure on the
top of the xylem vessels, causing water to
be “sucked” up

As water goes up, they have the tendency to stick to each other. This is known as cohesion
and adhesion forces
Measuring transpiration rates
Look how much water is lost

Conditions that affect transpiration rate

● Temperature
● Humidity
● Wind speed

Translocation of sucrose and amino acids

Translocation The movement of sucrose and amino acids

in the phloem from the source to the sink

source Part of a plant that releases sucrose or

amino acids to be transported to other parts

sink Part of a plant which sucrose or amino acids

are transported
 ● The higher the humidity, the less
steep the diffusion gradient
● Thus less transpiration

● The rate of transpiration increases in

the presence of wind
● Wind displaces the water vapor and
creates a steep concentration
gradient

● The higher the light intensity, the

temperature increases
● This causes the leaves to heat up
● The stomatas then open and allow
more water vapor to diffuse out

● As temperature increases, rate of

transpiration increases
● More evaporation
● Maintains a steep diffusion gradient

9 Transport in animals
9.1) Circulatory system
9.2) Heart
9.3) Blood vessels
9.4) Blood
The main transport of all mammals is known as the circulatory system
Valves in the heart make sure blood travels in one direction

Circulatory system A system of blood vessels with a pump and

valves to ensure one way flow of blood

Valves Structures that allow a liquid to flow in one

direction only

Double and single circulatory systems

The circulatory system shown on the left is a double circulatory system. Blood travels twice
into the heart in a single circuit.

A single circulatory system is when blood travels into the heart only once in a single circuit.

Double circulatory system A system in which blood passes through the

heart twice on a single complete circuit
 Single circulatory system A system in which blood passes through the
heart once on a single complete circuit

The heart

Atria Thin walled chambers that receive blood

Ventricles Thick walled chambers which pump out

blood

Septum The structure that separates the left and

right sides of the heart

Pulmonary veins Veins that carry oxygenated blood from the

lungs to the left atrium of the heart

Venae cavae The large veins that brings deoxygenated

blood to the right atrium

Aorta The largest artery in the body,

Pulmonary artery The artery that carries deoxygenated blood

 from the right ventricle to the lungs

Atrioventricular valve Valve between an atrium and a ventricle in

the heart, which allows blood to flow from
the atrium to the ventricle but not in an
opposite direction

Semilunar valves Valves close to the entrances to the aorta

and pulmonary artery which prevent the
backflow of blood from the arteries to the
ventricles

The ventricles have thicker walls than atrium

Coronary arteries

Coronary arteries Vessels that deliver oxygenated blood to the heart muscle

Coronary heart Disease caused by blockage of the coronary arteries

disease
Preventing CHD

To measure heartbeat,

We use an ECG

Differences in the muscle wall thickness

The left ventricle is thicker as it has to withstand high pressures to pump blood out of the
body as for the right its thinner as there is less pressure

Valves

Atrioventricular valves A valve between an atrium and ventricle of

a heart, which allows blood to flow from the
atrium to the ventricle but not in the
opposite direction

Semilunar valves Valves close to the entrances of the aorta

and pulmonary artery which prevents
backflow of blood

Coronary arteries

Coronary arteries Vessels that deliver oxygenated blood and

nutrients to heart muscle

Coronary heart disease Disease caused by blockage of coronary

 arteries

Preventing CHD

Heartbeat
● Use a ECG

Pulse rate Number of times artery expands and recoils

in one minute

ECG Showing electrical activity of the heart

How does the heart beat?

Blood vessels
 artery Thick-walled vessel that takes high pressure
blood away from the heart

Capillary Tiny vessels with walls only 1 cell thick

Vein A thinned wall vessel that takes low

pressure blood back to the heart

arteries Carry blood Thick and Relatively low Can withstand

away strong lumen size high pressure

capillaries Allow supply of Very thin Very narrow One cell thick to
nutrients to be lumen size maximize
given nutrients being
absorbed

veins Return blood Quite thin Wide lumen size Have valves to
back to heart prevent
backflow

Naming blood vessels

Blood

Plasma Liquid part of blood

Red blood cells Biconcave blood cells that transport oxygen

White blood cells Blood cells that fight against pathogens

Platelets Tiny cell fragments that aid in blood clotting

hemoglobin A red pigment found in red blood cells that

can carry oxygen

White blood cells

Phagocytes White blood cells that destroys pathogens

by phagocytosis

Lymphocytes White blood cells that secrete antibodies

Platelets

fibrinogen A soluble protein in plasma

fibrin An insoluble protein that is

formed from fibrinogen
when a blood vessel is
damaged

Plasma

water Absorbed in small All cells Excess is removed

intestine by kidneys

Various proteins Fibrinogen is made Remain in blood Fibrinogen aids in

in liver blood clotting when
there is a cut
 lipids Absorbed in ileum Breakdown or Used for energy
storage

carbohydrates Absorbed in ileum To all cells Excess glucose is

converted to
glycogen in the liver

Excretory Produced by amino Kidneys for excretion Urea is removed

substances acids

Mineral ions Absorbed in ileum To all cells Excess ions is

and colon excreted by kidneys

hormones Secreted by To all parts of the Only affect target

endocrine gland body organ and break
down

Dissolved gasses Waste product Lungs for excretion Removed or kept

10 Diseases and immunity

10.1) Diseases and immunity
10.1) Diseases and immunity continued

Transmissions of pathogens

Pathogen A microorganism that causes disease

Host An organism in which the pathogen lives

and reproduces

Transmissible disease A disease that can be pass on from one host

to another, transmissible diseases are
caused by pathogens

Toxin A poisonous substance, a chemical that

damages cells

symptoms Features that you experience when you

have a disease

Transmission The movement of pathogen from one host

to another

Infection The entry of pathogen into the body of the

 host

Body defenses

skin Prevents pathogens from entering the body

Hairs in nose Filter out the air

taste Taste if the food is bad or not

mucus Pathogen can be swept away by the mucus

stomach Hydrochloric acid kills bacteria

● Clean water supply

● Food hygiene
● Personal hygiene
● Waste disposal

Cholera
 1. Cholera bacteria is ingested and multiply
2. Bacteria attach to walls of alimentary canal
3. Bacteria releases a toxin
4. Toxin stimulates the small intestine to release chloride ions
5. The release of chloride ions cause the outside of the small intestine to have a lower
water potential thus water travels out the small intestine via osmosis
6. There is now a lot of water in the canal and the blood lacks chloride ions and water

To solve this, one must take oral rehydration salts

The immune response

Antibodies

antigen A chemical recognised by the body being

foreign and is not part of the normal set of
the body’s chemical substances, thus this
stimulates production of antibodies
Memory cells

Immune response The reaction of the body to the presence of

an antigen that involves antibody
production

Memory cells Long lived cells produced by the division of

the lymphocytes that can contracted their
antigen, memory cells respond quickly if
there is another contraction of the same
antigen

Vaccination (Active vs Passive immunity)

A person has active immunity if their body has made its own antibodies and memory cells
that can protect against the disease. This can be obtained by

● Being vaccinated
● Having the disease and recovering from it

A person has passive immunity if their body has already been given ready-made
antibodies that don't have memory cells. This can be obtained by

● Breast feeding
● Injected with dead pathogens or antibodies

Vaccine A harmless preparation of dead pathogens

to induce an immune response

Active immunity A long term defense against a pathogen by

antibody production

Passive immunity A short term defense against a pathogen by

antibodies acquired from another individual

11 Respiration and gas exchange

11.1) Gas exchange in humans

What is energy used for? (7)

1. Muscle contraction
 2. Making protein molecules
3. Cell division
4. Active transport
5. Growth
6. Transmitting nerve impulses
7. Body temperature regulation

Aerobic respiration

This happens inside the mitochondria

Anaerobic respiration

Aerobic respiration Chemical reactions that take place in the

mitochondria which uses oxygen to break
down glucose and other nutrient molecules
to release energy for use

Anaerobic respiration Chemical reactions in cells that break down

nutrient molecules to release energy
without oxygen
 Aerobic respiration Anaerobic respiration

Involves chemical reactions to break down glucose for energy

Uses oxygen Don't use oxygen

No alcohol or lactic acid produced Alcohol or lactic acid produced

Large amount of energy Small amount of energy

Carbon dioxide made Carbon dioxide is made from yeast and

plants, not animals

Gas exchange in humans

Characteristics of gas exchange surfaces (4)

● Thin to allow gasses to diffuse quickly
● Close to an efficient transport system to take gasses
● Large surface area
● Good supply of oxygen

Gas exchange The diffusion of oxygen and carbon dioxide

into and out of an organism’s body

Gas exchange surface A part of the body where gas exchange

between the body and environment takes
place

The human breathing system

Gas exchange takes place in the lungs, where there are many alveolus. Here, oxygen
diffuses into the blood which allows the alveolus to then also exchange carbon dioxide to
remove it.

Alveoli Tiny air-filled sacs in the lungs where gas

exchange takes place

Trachea The tube through which air travels to the

lungs with rings of cartilage to support it
The cilia also beats
rhythmically to sweep
mucus from the goblet cell out
of the lungs as it collects
dust, pathogens, etc

The nose and mouth Have goblet cells that secrete mucus and
moistens it

The trachea Have rings of cartilage around it to prevent

it from collapsing

The bronchi Allows exchange of gasses

The alveoli ● Large surface area

● Very thin
● Close to a transport system
● Good supply of oxygen
 Ventilation The movement of air into and out of the
lungs, by breathing movements
Comparing inspired air and expired air

component Percentage in inspired air Percentage in expired air

oxygen 21 16

Carbon dioxide 0.04 4

Water vapor Variable Usually very high

Breathing movements

breathing Using the muscles in the diaphragm and the

intercostal muscles, to change the volume
of the thorax so that the air is drawn into
and pushed out from the lungs

Intercostal muscles Muscles between the rib which raise and

lower the rib cage when they contract and
relax
 diaphragm A muscle that separates the chest cavity
from the abdominal cavity in mammals, it
also helps in breathing

Breathing out vs breathing in

Breathing out (expiration) Breathing in (Inspiration)

Volume of thorax decreases Volume of thorax increases

Pressure inside increases Pressure inside decreases

External intercostal muscles relax External intercostal muscles contract

Internal intercostal muscles contract Internal intercostal muscles relax

Oxygen debt

Oxygen debt Extra oxygen that is needed after anaerobic

respiration has taken place, in order to
break down the lactic acid produced

12 Excretion and homeostasis

12.1) Excretion in humans
Definition of excretion

● The process by which metabolic waste products and toxic substances are removed
from the body to maintain homeostasis

Key excretory organs

Lungs ● Excrete carbon dioxide and water, a waste products of aerobic

respiration

Kidneys ● Filter the blood to remove urea, excess salts, water and urine

Skin ● Excretes sweat through sweat glands. Which contains water,

salts and small traces of urea

Liver ● Process amino acids by deamination, converting them to urea

The urinary system

Kidneys ● Filter blood to form urine

Ureters ● Tubes that transport urine from the

kidneys to the bladder

Bladder ● A muscular sac that stores urine

Urethra ● The tube that carries urine from the

bladder out from the body

Kidney structure

● The outer layer where filtration of the

blood takes place

Cortex

● The inner region where there is loops of

Henle and collecting ducts for water
reabsorption
Medulla

Nephron ● The functional unit of the kidney for urine

formation
Nephron

Bowman's capsule ● Site of ultrafiltration

Glomerulus ● Little network of blood capillaries

where blood is filtered

Loop of henle ● Maintains the concentration in the

medulla for water absorption

Collecting duct ● Concentrates the urine as it passes

through the medulla

Formation of urine

Filtration happens in the glomerulus as small molecules such as water, glucose, ions, urea
are filtered out of the blood into the nephron
Selective reabsorption happens in the loop of henle (nephron) such as water and glucose
are taken back into the blood

How is urea produced?

Urea is produced when the liver converts excess amino acids to urea via deamination by
removing the nitrogen-containing part

Deamination The removal of the nitrogen containing part

of amino acids to produce urea

Role of liver

1. Deamination
2. Detoxification
3. Bile production

Homeostasis

Internal environment The conditions inside the body

Homeostasis The maintenance of a constant internal

environment

What can homeostasis control?

● Temperature to work as optimum rate
● Controlling blood glucose concentration

Controlling blood glucose concentration needs a steady supply of glucose to allow them to
respire. Insulin and glucagon control the blood glucose concentration.

Negative feedback

Glucagon A hormone secreted by the pancreas, which

increase blood glucose concentration
 Set point The normal value or range of values for a
particular parameter- for example, the
normal range of blood glucose
concentration or the normal body
temperature

Negative feedback A mechanism that detects a move away

from the set point, and brings about actions
that takes the value back towards the set
point

Diabetes

Controlling body temperature

The human skin

 ● There are sweat glands that secrete sweat and cool down the skin

The hypothalamus

Sweat gland A structure found in the skin of mammals,

which secretes a watery fluid onto the skin
surface to reduce body temperature

Hypothalamus Part of the brain that is involved in the

control of body temperature

When the temperature falls or rises…

When temperature falls,

● Muscles contract, thus shivering
● Metabolism may increase, respiration increase
● Hairs standing up
● Arterioles constrict, thus shunt vessels dilated (vasoconstriction)

When temperature rises,

● Muscles relax, thus less movement
● Metabolism decrease
 ● Hairs lying flat
● Arterioles dilate, shunt vessels narrowed (vasodilation)
● More sweat produced

13 Coordination and response

13.1) Coordination and response
13.2) Sense organs
13.3) Hormones

The mammalian nervous system

● The mammalian nervous system consisted of two parts:

● The central nervous system consists of the brain and spinal cord
● The peripheral nervous system has nerves and neurons which coordinate and
regulate body functions.

● Electrical impulses travel through the neurons

● The nervous system helps with the coordination and regulation of body functions

Types of neurons

Nerve impulse: an electrical signal that passes along the nerve cells called neurons

Axons ● Ensure less time is wasted when the impulse is transferred

from one neuron to another

Dendrites ● Extensions which form a network for easy communication

Motor neurone
 ● Carry impulses from the CNS to the effectors

Neurone A cell that is specialized for conducting

electrical impulses rapidly

Motor neurone A neuron that transmits electrical impulses

from the central nervous system to an
effector

Axon A long, thin fiber of cytoplasm that extends

from the cell body of a neuron

dendrites Short fibers of cytoplasm in a neuron

Nerve impulse An electrical signal that passes rapidly

along an axon

Sensory neurone

● Carry impulses from the sense organs to the CNS

Relay neurone

● The middleman inside the CNS connects sensory to motor neurons

Simple reflex arc

Reflex action: automatically and rapidly integrates and coordinates the stimuli with the
response of effectors.
Synapses
 1. Vesicles containing neurotransmitters move along the neuron
2. The vesicles fuse with the cell membrane and release neurotransmitters
3. These neurotransmitters diffuse along the synaptic cleft
4. The neurotransmitters then bind with the complementary receptor proteins
5. The impulses then travel across the side

Sense organs

Cornea ● Refract light

 Iris ● Controls how much light enters the
pupil

Lens ● Focuses light onto the retina

Retina ● Contains light receptors

Optic nerves ● Carry impulses to the brain

Pupil ● A hole which allows light to enter

Accomodation

Accommodation is the adjusting for near and distant objects

Convex lens Long sightedness The image is focused Closer

too far of the retina

Concave lens Short-sightedness The image is focused Further

too near of the
retina
Bright light Circular muscle relax Radial muscles Circular muscles
contract larger

Dim light Circular muscle Radial muscles relax Circular muscles

contract reduce

Hormones

Adrenal gland Adrenaline Prepares body for vigorous

action

Insulin Reduces the concentration

Pancreas of glucose in the blood

Glucagon Increases the concentration

of glucose in the blood

Testis Testosterone Causes the development of

male secondary sexual
characteristics

Ovary Oestrogen Causes the development of

female secondary sexual
characteristics to aid in the
menstrual cycle

Nervous system Endocrine system

Made up of neurons Made up of glands

Information transmitted in the form of Information transmitted in the form of

electrical impulses chemicals called hormones

Impulses transmitted along neurons Chemicals carried in the blood plasma

Impulses travel fast Chemicals travels more slowly

Nerve impulse only happens for short time Effects of a hormone may last longer
Coordination in plants

Adrenaline A hormone secreted by adrenal glands that

stimulate fight or flight

Tropism A growth response by a plant, in which the

direction of growth is related to stimulus

Phototropism A response in which part of a plant that

grows towards or away from the direction
where light is coming

Gravitropism A response in which part of a plant grows

towards or away from gravity

Auxin

Auxin A plant hormone made in the tips of the

shoots which causes the cells to elongate

Distribution of rods and cones

 Rods Cones

● Provide high detail in dark rooms ● Provide detailed colored images

● Packed most tightly around the ● Most packly tighten on the retinas
retina center

Fovea:

● Part of the retina where the receptors cells are pushed most closely together
● Where light is focused when you look straight at an object

Distribution of rods and cones

● More rod cells than cone cells

● A number of cone cells packed in the fovea (sharp vision)(CF) no rod
● No rod and cone cells at the blind spot, on the optic nerve

14 and 15 Reproduction in plants and animals

14.1) Asexual reproduction
14.2) Sexual reproduction
14.3) Sexual reproduction in plants
15.1) Sexual reproduction and hormones in humans
15.2) Sexually transmitted infections

Asexual reproduction

● The process resulting in the production of genetically identical offsprings from one
parent

Every organism has chromosomes (long threads of DNA found in the nucleus of the cell)
Where genetic information is contained. When an organism reproduces asexually, some of
the parent organisms' cells undergo division through mitosis, producing new cells that are
genetically identical to their parent cells.

Sexual reproduction

● The process involves the fusion of the nuclei of two gametes to form a zygote and the
production of offspring that are genetically different from each other.
 1. Gametes are sex cells that a parent organism that reproduces through sexual
reproduction produces.
2. When two gametes fuse together, they form a new cell known as a zygote which
undergoes fertilization.
3. The zygote then divides several times until a new organism is formed

Gametes

● A gamete only contains half the number of chromosomes than an ordinary cell. When
a zygote forms the two gametes fuse to add to 46 chromosomes

Diploid Two complete sets of chromosomes

Haploid Having only a single set of chromosomes

Mitosis Division of a cell nucleus resulting in two

genetically identical nuclei

Meiosis Division of a diploid nucleus resulting in 4

different genetically different haploid nuclei
.
Self and cross pollination

Self pollination The transfer of pollen grains from the

anther of a flower to the stigma of the same
flower

Cross pollination The transfer of the pollen grains from the

anther of a flower to the stigma of a flower
on a different flower of the same species
Advantages of asexual and sexual reproduction

Asexual reproduction Sexual reproduction

Rapid reproduction rate Promotes genetic diversity

Faster Increases adaptability

Less energy needed Stops harmful mutation

Ensures uniformity for desirable features

Disadvantages of asexual and sexual reproduction

Lack of genetic diversity Slower

Less ability More energy needed

Chance for harmful mutation Can cause undesirable features

The female reproductive system

ovaries Organs that produce female gametes

oviducts Tubes leading from the ovaries to the

uterus

uterus The organ in which a fetus develops before

birth

cervix A narrow opening leading from the uterus to

the vagina

vagina opening from the uterus to the outside of

the body

testes Organs which male gametes are made

scrotum The sac that contains the testes

 Sperm duct A tube that transports sperm from the testis
to the urethra

penis Organ containing the urethra where urine

and sperm are carried

Prostate gland Organ that produce nutritional fluid

ovulation The release of an egg from an ovary

epididymis Part of a testes where sperm is stored

Implantation
The placenta
placenta Organ that connects the fetus to the mother
and allow exchange of nutrients and waste

fetus An unborn mammal with full organs formed

Umbilical cord A structure containing blood vessels that

connects fetus to placenta

Amniotic sac A tough membrane that surrounds a

developing fetus in the uterus

Amniotic fluid A liquid secreted by amniotic sac that

protects the uterus
 Maternal artery Blood that supplies nutrients to the baby

Maternal vein Blood that takes away waste from the baby

Sperm Adaptive features Egg

Size ● Smaller ● Generates ● 30 ● Has energy

than egg swimming times for
cells movement larger fertilization

Structure ● Heads ● Releases energy ● Deep ● Has a

● Tail needed to swim layer of barrier to
● Acrosome jelly allow only
1 sperm
cell

Ability to move ● Can move ● Have enzymes in ● Cannot

acrosome to move
digest jelly coat

Numbers ● Millions ● One

produced
FSH Causes follicles to develop an egg

LH Cause ovulation to happen

estrogen Stimulates a development of lining

progesterone Maintains and thickens the lining

STI (sexually transmitted infection) A disease caused by sexual contact with

another person with the pathogen

AIDS (Acquired immune deficiency Caused by HIV where it destroys white

syndrome) blood cells

HIV Human immunodeficiency virus

16 Chromosomes, genes and proteins
16.1)Chromosomes, genes proteins
16.2) Mitosis
16.3) Meiosis
16.4) Monohybrid inheritance

Chromosome A length of DNA found in the nucleus of the

cell that contains genetic information in the
form of many different genes

DNA A molecule that contains genetic

information in the form of genes that
control what proteins are made

Gene A length of DNA that codes for one protein

Alleles An alternative form for gene

Mitosis and meiosis

Mitosis Division of a cell nucleus resulting in two

genetically identical nuclei

Meiosis Division of a diploid nucleus resulting in 4

different genetically different haploid nuclei

Meiosis is said to be a reduction division

Reduction division Describe what happens in the meiosis

where chromosomes are halved
Homozygous Having two identical alleles

Heterozygous Having two different alleles

Genotype and phenotype

genotype The genetic makeup of an organism in

terms of the alleles present

Phenotype The observable features of an organism

Dominant allele An allele that is expressed if present

Recessive allele An allele that is only expressed without a

dominant allele

Codominance

Codominance Alleles that are both expressed in the

 phenotype when they are both present

Alleles in gametes

Inheritance The transmission of genetic information

from generation to generation
Important ratios to remember

Homozygous + Homozygous 100% offspring homozygous

Heterozygous + Homozygous 50% homozygous 50% heterozygous

Heterozygous + Heterozygous 25% homozygous 25% another homozygous

50% heterozygous

Sex determination and sex linkage

 Sex-linked genes Genes that are found on a part of a sec
chromosome and not on the other sex
chromosome, this leads to a certain gender
getting more of that characteristics

Genes and protein synthesis

Protein synthesis

Messenger RNA A molecule that carries a copy of

information on DNA to a ribosome to
synthesize a protein
 1. Gene is copied in the MRNA in the nucleus (transcription)
2. MRNA moves out to the nucleus into the cytoplasm
3. MRNA passes through ribosome
4. Ribosomes assemble amino acids to form proteins in a particular order by the MRNA

17 Variation and selection

17.1) Variation
17.2) Adaptive features
17.3) Selection
Variation

Variation Differences between individuals of same

species
Discontinuous variation Variation in which there are distinct
categories of phenotype
Population A group of organisms of one species living
in the same area at the same time
Continuous variation Variation in which there are continuous
range of phenotype

Causes of genetic variation

mutation Random change in the base sequence in the

DNA

Adaptive features

Adaptive feature A feature that allows an organism to survive

and reproduce in the wild
18 Organisms and their environment

18.1) Energy flow

18.2) Food chains and food webs
18.3) Nutrient cycles
18.4) Populations
 habitat The place where an organism lives

community All the populations of all the different

species in an ecosystem

ecosystem A unit containing all the organisms in a

community and their environment,
interacting with one another

Energy flow

Food chain Diagram showing the flow of energy

Food web A network of interconnected food chains

Producer An organism that makes its own organic

nutrients

Consumer An organism that feeds off from other

organisms

Herbivore An animal that feeds off plants

Carnivore An organism that feeds of dead or waste

organic material
Pyramids of numbers, pyramids of energy

Pyramid of numbers A diagram in which the area of the bar at

each trophic level shows the relative
number of organisms

Pyramid of biomass A graph showing the relative quantity of

biomass in each trophic level

Why are trophic levels always below 4 levels or 5?

● Not all animal or plant parts can be digested

● Energy is lost via respiration and excretion
● Energy can be used for other processes

The carbon cycle

The nitrogen cycle

Nitrogen fixation Converting inert nitrogen gas into
ammonium

Nitrification Converting ammonium ions to nitrate ions

denitrification Converting nitrogen ions to ammonia

19 Human influences on ecosystems

19.1) Food supply
19.2) Habitat destruction
19.3) Pollution
19.4) Conservation

Improve in farming
● Use of machinery
● Chemical fertilizers
● Insecticides
● Selective breeding

Monocultures

Monocultures An area of ground covered by a single

species crop

Biodiversity The number of different species that live in

that area

Why are monocultures bad?

● Increase in pests
● Reduction in soil fertility
● Higher chances of diseases

Intensive livestock farming

Farming of monoculture using high amounts of pestities, herbicides and fertilizers.

Animals are kept in high densities and energy loss is limited.

● Welfare issues
● Spread of disease
● Waste can produce methane
● Large quantities of water may need to be provided
Pollution by greenhouse gasses

Greenhouse gasses Gasses such as carbon dioxide and methane

that trap heat in the atmosphere

Greenhouse effect The heating effect on the earth of the

trapping of heat

Conservation

Sustainable resource One that is produced as rapidly as it is

removed from the environment, so that it
does not run out
Conserving the stocks

● Quotas
● Some areas no fish zones
● Some areas seasonal fishing
● Types of nets
● Inspectors

Captive breeding Keeping animals in captivity, in a zoo

Seed banks Facilities in which seeds of different plant

species, or crop varieties are stored for long
periods of time

Reasons for conservation programs

● Global warming
● Losing species
● No medicines as plant contain chemicals
● Lose useful alleles
20 Biotechnology and genetic modification

20.1) Biotechnology and genetic modification

20.2) Biotechnology
20.3) Genetic modification

Biotechnology Using organisms usually microorganisms to

produce required substances

Genetic modification Changing the genetic material by inserting

individual genes to produce desired proteins

Growing microorganisms in a fermentor

What can genetic modification do?

● Making human proteins
 ● Making herbicide and pest resistant crop plants
● Improving nutritional qualities

How is genetic modification done?

1. Required target gene is in human DNA

2. Restriction enzymes are cut and isolated
3. The same restriction enzyme is then used to cut as the plasmid is removed
4. Plasmid form sticky ends
5. Place target gene and allow them to bond with DNA ligase
6. Forms a recombinant plasmid
7. Insert back to the plasmid of the organism
 8. Grow and reproduce in fermentor

IGCSE BIO DEFINITION

1. Characteristics and classification of living organisms

Movement As an action by an organism or part of an organism causing a change

in position

Respiration Chemical reactions in cells that break down nutrient molecules to

release energy for metabolism

Sensitivity The ability to detect and respond to changes in the environment

Growth As the permanent increase in size and dry mass

Reproduction The processes that make more of the same kind of organism

Excretion As the removal of the waste products of metabolism

Nutrition Taking in of materials for energy, growth and development

Species A group of organisms that can produce fertile offspring

Binomial system Naming species as an internationally agreed system in which the

scientific name of an organism shows part showing genus and species

2 Organization of the organisms

Tissue Tissue as a group of cells with similar structures working together to

perform a shared function

Organ As a structure made up of a group of tissues working together to

perform a specific function

Organ system As a group of shared organs with related functions working together
to perform body functions

3 Movement in and out of cells

Diffusion Diffusion is the net movement of particles from higher concentration

with lower concentration down a concentration gradient

Osmosis Net movement of water molecules from region of high water

potential to lower water potential through a partially permeable
membrane

Active transport Net movement of particles through a cell membrane from a region of
lower concentration to a region of higher concentration through a
partially permeable membrane against a concentration gradient
Enzymes

Catalyst A substance that increases the rate of chemical reaction and is not
changed or affected by the reaction

Enzymes Enzymes as proteins that are involved in all metabolic reactions where
they act as biological catalysts

Plant nutrition

Photosynthesis The process by which plants synthesize carbohydrates from raw

materials using energy from the light

Human nutrition

Balanced diet Balanced diet is a diet that consists all the necessary nutrients in
the correct amounts for maintaining human health

Ingestion Taking of substances into the body

Physical digestion Breakdown of food to small pieces

Chemical digestion Break down of large insoluble molecules to small soluble

molecules

Absorption Movement of nutrients from small intestine to bloodstream

Assimilation Movement as uptake of nutrients by the cells, becoming part of

the cells

Egestion Removal of undigested food from the body as poop

Transport in plants

Transpiration Loss of water vapor when water evaporates from the surface of
the mesophyll cells and leaves the leaves via water vapor

Translocation Movement of sucrose and amino acids in phloem from source to

the sink

Source As the parts of the plants that release sucrose or amino acids

Sink Sink is the parts of plants that use or store sucrose or amino
acids

Transport in animals
 Circulatory system System of blood vessels with a pump and valves to ensure one
way flow of blood

Diseases and immunity

Pathogen A disease causing organism

Transmissible disease A transmissible disease as a disease in which pathogen is

transferred from one host to another

Active immunity A defense against a pathogen by antibody production in the

body

Passive immunity Short term defense against a pathogen by antibodies

acquired from another individual placenta and breast milk

Antibodies Proteins that bind to antigens leading to direct destruction of

pathogen or marking for destruction by phagocytes

Cholera Disease caused by a bacterium which is transmitted by

contaminated water

Excretion in humans

Deamination Removal of the nitrogen containing part of the amino acids

to form urea

Coordination and response

Synapse The function between two neurons

Reflex action The means of automatically and rapidly

integrating and coordinating stimuli with the
responses of effectors

Sense organ Organs with a group of receptor cells

responding to specific stimuli

Hormone A chemical substance produced by a gland

which alters the activity of the organs

Homeostasis Maintenance of a constant internal

environment

Gravitropism Response to which parts of a plants grow

due to gravity

Phototropism Response to which parts of a plants grow

due to light
Drugs

Drugs Any substance taken into the body that

modifies or affects chemical reactions in the
body

Reproduction

Asexual reproduction Asexual reproduction as a process resulting

in the production of genetically identical
offspring from one parent

Sexual reproduction Sexual reproduction is the process of the

fusion of the nuclei of two gametes that are
genetically different from each other

Fertilization Fusion of the nuclei of the gametes

Pollination Transfer of pollen grains from the anther to

a stigma

Self pollination Transfer of pollen grains from the anther of

the flower to the stigma of the same plant

Cross pollination Transfer of pollen grains from the anther of

a flower to the stigma of the same flower

Sexually transmitted infection An infection that is caused by the

transmission of fluids through sexual
contact

Inheritance

Inheritance The transmission of genetic information from generation to

generation

Chromosomes Chromosomes are made of DNA which contains genetic

information in the form of genes

Gene Genes as the length of DNA that codes for a protein

Allele Allele is an alternative form of a gene

Haploid Nucleus containing a single set of chromosomes

Diploid Nucleus containing two sets of chromosomes

Mitosis Nuclear division giving rise to genetically identical cells

Meiosis The reduction devising in which the chromosome number is

halved from diploid
 Stem cell Unspecialised cells that divide by mitosis to produce daughter
cells that can become specialized cells for specific functions

Genotype The genetic makeup of an organism in terms of alleles present

Phenotype Observable features of an organism

Homozygous Two identical alleles of a particular gene

Heterozygous Two different alleles of a particular gene

Dominant Allele expressed in a genotype

Recessive Allele that is expressed if there is no dominant allele in a

genotype

Codominance Situation where both alleles is present in the genotype

Sex-linked Feature in which the gene is responsible is located on a sex

characteristics chromosome and characteristics is shown to occur in a certain
gender more

Variation and selection

Variation Differences between individuals of the same species

Mutation Mutation as genetic change

Gene mutation Change in the base sequence of an DNA

Adaptive feature An inherited feature that helps the organism to survive and
reproduce

Adaptation Adaptation resulting from natural selection where populations

become more suited to the environment over the year

Organisms and their environment

Food chain Showing the transfer of energy from one organism to another

Food web Network of interconnected food chains

Producer An organism that makes its own organic nutrients

Consumer An organism that gets its energy from feeding on other organisms

Herbivore Animal that gets its energy by eating plants

Carnivore Animal that gets its energy by eating other animals

Decomposer Organism that gets its energy from dead or waste organisms
 Trophic level Position of an organism in a food chain, food web or ecological pyramid

Population A group of organisms of one species living in the same area same time

Community A group of populations of different species living in an ecosystem

Ecosystem A unit containing the community of organisms and its environment

Human influences on ecosystems

Biodiversity Number of species living in that area

Sustainable One which is produced rapidly despite being removed from the
resource environment and is not run out

Biotechnology and genetic modification

Genetic Changing of the genetic material of an organism by removing,

modification changing or inserting individual genes

Common questions

Enzymes

● Enzymes act as biological catalysts, speeding up reactions without being consumed.

● Enzyme action follows the "lock and key" model.
● Temperature and pH affect enzyme structure and function (denaturation at
extremes).

Photosynthesis

● Photosynthesis is the process by which plants produce glucose using light energy, CO₂, and
water.
● Equation: 6CO2+6H2O→C6H12O6+6O26CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂6CO2+6H2O→C6H12O6
+6O2.
● Chlorophyll converts light to chemical energy.
● Carbohydrates made are stored as starch and used for growth and respiration.
● Light, CO₂, and temperature are limiting factors in photosynthesis.
● Experiments with aquatic plants and hydrogen carbonate indicators show the role of
light in gas exchange.

Digestive System

● Digestion: Physical (chewing), Chemical (enzymes breaking down food).

● Small intestine receives enzymes from the pancreas and bile from the liver.
● Bile emulsifies fats, increasing their surface area for digestion.
● The villi and their blood vessels/lacteals help absorb nutrients and transport them.

Plant Transport
 ● Root hair cells absorb water and minerals via osmosis and active transport.
● Xylem carries water upwards through cohesion and transpiration pull.
● Factors like temperature, humidity, and light intensity affect transpiration.
● Wilting can prevent excess water loss in drought conditions.
● Translocation moves sugars from sources (leaves) to sinks (growing tissues).

Animal Transport

● Fish have single circulation, while mammals have double circulation, which is more
efficient.
● The left ventricle has thicker walls because it pumps blood to the entire body.
● Heart rate increases during physical activity.
● Coronary heart disease can be caused by risk factors like smoking, high cholesterol,
and lack of exercise.

Disease and Immunity

● Pathogens have unique antigens, and the body uses lymphocytes and antibodies to
fight infections.
● Vaccination helps control the spread of diseases by promoting active immunity.
● Cholera is caused by Vibrio cholerae and leads to severe dehydration due to the toxin
it produces.

Gas Exchange in Humans

● The alveoli provide a large surface area for gas exchange.

● The trachea has cartilage to keep it open during breathing.
● During exercise, increased CO₂ stimulates deeper and faster breathing.

Respiration

● Aerobic respiration: C6H12O6+6O2→6CO2+6H2O+EnergyC₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O +

EnergyC6H12O6+6O2→6CO2+6H2O+Energy.
● Anaerobic respiration in yeast and muscles generates less energy and produces
ethanol/lactic acid.

Excretion in Humans

● The kidney filters blood, reabsorbs essential substances, and produces urine.
● Excretion removes toxic substances like urea.

Coordination and Response

● The eye and nervous system regulate bodily responses.

● The pupil reflex and accommodation adjust light intake and focus.
● Hormones, like adrenaline, regulate functions such as heart rate.

Homeostasis

● Homeostasis involves maintaining internal conditions like temperature and glucose

levels.
● Insulin and glucagon regulate blood glucose.
● Negative feedback mechanisms are crucial for balance.
Tropic Responses

● Phototropism and gravitropism involve plant growth responses to light and gravity,
controlled by auxins.

Drugs

● Antibiotics treat bacterial infections, but overuse can lead to resistance, e.g., MRSA.

Reproduction

● Sexual reproduction creates genetic diversity; asexual reproduction is faster but

offers no variation.
● Fertilization restores the diploid number of chromosomes.

Plant Reproduction

● Pollination leads to fertilization; the type of pollination affects genetic diversity.

● Seed germination is influenced by environmental factors.

Human Reproduction

● Puberty is driven by testosterone and estrogen.

● The placenta and umbilical cord nourish the fetus.
● HIV is transmitted through body fluids and can lead to AIDS.

DNA and Protein Synthesis

● DNA codes for proteins, with mRNA carrying instructions to ribosomes for translation.

Cell Division

● Mitosis produces identical cells; meiosis produces gametes with half the chromosome
number.
● Stem cells have the potential to differentiate.

Monohybrid Inheritance

● Genetic crosses, including Punnett squares, predict offspring traits.

● Codominance and sex-linked traits affect inheritance patterns.

Variation and Selection

● Variation can be continuous or discontinuous.

● Natural selection favors adaptive traits, while artificial selection is human-directed.

Human Influences on Ecosystems

● Monoculture, deforestation, and pollution negatively affect ecosystems.

● Conservation efforts focus on sustainable resources and biodiversity protection.

Biotechnology
 ● Bacteria and yeast are useful in industry for producing biofuels and other products.
● Enzymes are used in food processing and detergents.

Genetic Modification

● Genetic engineering alters organisms' traits for various purposes, including improved
crop resistance.