Download BIOLOGY REVISION Levels of Organisation: LEVEL 1 – Cells Are

BIOLOGY REVISION
Levels of Organisation:
LEVEL 1 – Cells
Are the basic unit of structure and function in living things.
May serve a specific function within the organism
Examples- blood cells, nerve cells, bone cells, etc.
LEVEL 2 - Tissues
Made up of cells that are similar in structure and function and which work together to
perform a specific activity
Examples - blood, nervous, bone, etc. Humans have 4 basic tissues: connective, epithelial,
muscle, and nerve.
LEVEL 3 - Organs
Made up of tissues that work together to perform a specific activity
Examples - heart, brain, skin, etc.
LEVEL4 - Organ Systems
Groups of two or more tissues that work together to perform a specific function for the
organism.
Examples - circulatory system, nervous system, skeletal system, etc.
The Human body has 11 organ systems - circulatory, digestive, endocrine, excretory
(urinary), immune (lymphatic), integumentary, muscular, nervous, reproductive, respiratory,
and skeletal.
LEVEL 5 - Organisms
Entire living things that can carry out all basic life processes. Meaning they can take in
materials, release energy from food, release wastes, grow, respond to the environment, and
reproduce.
Usually made up of organ systems, but an organism may be made up of only one cell such as
bacteria or protist.
Examples - bacteria, amoeba, mushroom, sunflower, human
Cell Structure
Animals and Plants
Part
Function
Nucleus
Contains genetic material, which controls
the activities of the cell
Cytoplasm
Most chemical processes take place here,
controlled by enzymes
Cell membrane
Controls the movement of substances into
and out of the cell
Mitochondria
Most energy is released by respiration here
Ribosomes
Protein synthesis happens here
Just Plants
Part
Function
Cell wall
Strengthens the cell
Chloroplasts
Contain chlorophyll, which absorbs light
energy for photosynthesis
Permanent vacuole Filled with cell sap to help keep the
cell turgid
Diffusion
Diffusion is the net movement of particles down a concentration gradient from an area of
high concentration to one of low concentration.
E.g.
Location
Particles move
From
To
Gut
Digested food products
Gut cavity
Blood in capillary of villus
Lungs
Oxygen
Alveolar air space
Blood circulating around the lungs
Osmosis
Osmosis is the movement of water from a less concentrated solution to a more
concentrated solution through a partially permeable membrane.
E.g. Osmosis is important to plants. They gain water by osmosis through their roots. Water
moves into plant cells by osmosis, making them turgid or stiff so they that able to hold the
plant upright.
RUPTURED
INCIPIENT PLASMOLOSIS
CRENATED
TURGID
INCIPIENT PLASMOLOSIS
FLACCID
Active Transport
Active transport is the process by which dissolved molecules move across a
cell membrane from a lower to a higher concentration.
In active transport, particles move against the concentration gradient - and therefore
require an input of energy from the cell. Sometimes dissolved molecules are at a higher
concentration inside the cell than outside, but, because the organism needs these
molecules, they still have to be absorbed. Carrier proteins pick up specific molecules and
take them through the cell membrane against the concentration gradient.
In humans: during the digestion of food in the small intestine. Carbohydrates are broken
down into simple sugars such as glucose. The glucose is absorbed by active transport into
the villi, to be passed into the bloodstream and taken around the body.
In plants: Cannot absorb minerals by osmosis or diffusion so the root hair cells have carrier
molecules on their surface that pick up the minerals and move them into the cell against the
concentration gradient.
Factors Affecting Movement of Substances In and Out of Cells:
 Surface Area to Volume Ratio
 Temperature: Gives particles more energy so increases the speed of movement.
 Concentration Gradient: The steeper it is the faster movement carried out is.
Environment and Feeding Relationships
Habitat
The place where an organism lives
Population
All of the members of one species living in an area
Community All the living things, animals and plants, living in a particular habitat
Ecosystem
Habitat + Community
Use of Quadrats:
 Quadrats should be placed randomly so that a representative sample is taken
 You should look at the results from several quadrats in an area to reduce the effect
of an unusual distribution
 The results are more reliable when you look at the results from many quadrats
 Quadrats may also be used for slow moving animals such as snails/slugs
Trophic Levels
Food Chains: A food chain shows the different organisms that live in a habitat, and what eats
what.
Food Webs: When all the food chains in a habitat are joined up together they form a food
web.
Pyramids of number, biomass and energy transfer
Transfer or substances and energy along a food chain:
In an ecosystem there is energy, and this is what allows the organisms to live. This energy
mainly comes from one original source: photosynthesis. The plants use this solar energy to
produce carbohydrates, which are then consumed by other organisms: transferring the
energy.
The plants, however, use not all of the energy from sunlight they are far from efficient.
Much sunlight misses the plant, is in the wrong wavelength or lost in the inefficiencies of
photosynthesis. We use the term gross primary production to refer to the total energy in the
molecules of the plant; and net primary production is the surplus energy not used by the
plant itself.
At each level of the food chain energy is lost because the organism itself for respiration uses
it. This limits the number of steps there can be on a food chain as only 10% of energy is
transferred between trophic levels.
Also if a toxin such as a pesticide gets passed along the food chain, it continually increases in
concentration. When it reaches a top consumer at a tertiary level, amounts can often
become harmful and affect fertility and therefore population.
Human Influences on the Environment: Pollution
AIR
CFC’s:
 Chlorofluorocarbons
 1930 first produced by Thomas Midgely Junior
 Used in air conditioning and spray deodorants
 O-zone pollutant at ground level and blocks UV rays
Carbon Monoxide:
 CO
 Colourless, odourless + tasteless but highly toxic
 Produced In petrol engines
 Can cause acid rain
 Used in WWII to gas people
 Attaches to haemoglobin so it can’t carry oxygen – Asphyxiation
Carbon Dioxide
 CO2
 Released from burning of (fossil) fuels
 Keeps in light rays so warming the earth, ice caps melt, low lying countries liable to
flooding
GREENHOUSE GASES
 CO2
 CH4
 H2O
 CFC’s
 NO
Smoke
 Smoke Pollution can be domestic and industrial
 1956 clean air act
 Affects respiratory system
Sulphur Dioxide
 SO2
 Dissolves in water to form acidic solution
 Affects pH balance in rivers and lakes harming ecosystem
 Acid rain can affect photosynthesis
 Can cause asthma
Lead Compounds
 Pb
 Lead in atmosphere causes problems in the nervous system in infants and
adolescents slowing down mental development.
WATER
Lead Compounds
 Domestic plumbing system made of lead leading to lead poisoning
 Lead weights used by fishermen
Pesticides
 Used to make crops grow
 Rain washes substances and chemicals away from the soil into streams and lakes,
small animals consume it and bioaccumulation occurs E.g. D.D.T
 Organic has a balance of minerals and is low release
 Inorganic such as NPK drains into rivers and ponds causing plants to grow very
quickly. Then decomposing bacteria multiply rapidly to consume excess dead plant
and use up all the oxygen in the water. Sewage has a similar affect. This is
EUTROPHICATION.
Oil
 Oil spills from tankers, ships dumping and draining
 Birds get poisoned, blinded and reduced insulation causing hypothermia. They can’t
fly properly due to oil on their wings
 Blocks light coming through water so stops photosynthesis
 Cleaning Techniques:
 Bioremediation
 Controlled burning
 Dispersants
 Secondary containment
 Skimming
Acidification
 Naturally acidic soils leach into water ways
 SO2 CO2 NO2 combine with water to make acids
 Animals like leeches with soft skin absorb acidic water and die; Crustaceans cannot
make exoskeletons; buildings made of limestone are eroded.
 Solutions:
o Use cleaner coal
o Catalytic convertors
o Alkalis in air/water
Thermal Pollution
 It lowers the oxygen’s solubility in water
 Fish and water mammals are unable to extract oxygen
LAND
Deforestation
 Cutting down trees to create more land space, furniture, fuels
 12 million hectares cut down per year
 All forest could be gone by 2050 if rate continues
 Interferes with Carbon Cycle – CO2 released and not absorbed by trees and
surrounding plants
 Water Cycle messed up – no transpiration, desertification and dryer climate
 Loss of bio-diverse habitat for many species
 Soil becomes thin and infertile and is washed away easily (no longer held in place by
roots
Landfills
 A huge crater in the ground filed with rubbish then covered over
 Bacteria break down rubbish releasing methane into surrounding area
 Many materials are not biodegradable and becomes an eye-sore
 Seepage of toxic ions into rivers when it rains
CYCLES
WATER CYCLE:
CARBON CYCLE
Nitrogen Cycle
N2 is inert but humans and plants
need it for proteins (and amino
acids.)
3 Forms:
Nitrates – NO3Ammonium – NH4+
Nitrites – NO2Bacteria:
N2 Fixing: N2 to NO3Nitrifying: NH4+ to NO3Decomposers: Waste to NH4+
Denitrifying: NO3- to N2
Lightning can carry out the same
job as Nitrogen fixing bacteria
Nutrition in Humans
Carbohydrates:
Elements- C, H, O
Functions:
 Energy
 Structural (Cellulose Cell Wall in Plants)
Types:
1. Monosaccharides – Simple Sugars
2. Disaccharides – Complex Sugars
3. Polysaccharides
Monosaccharides
Properties: Sweet tasting, white crystals, soluble in water.
Function: Quick energy supply
TEST – BENEDICTS SOLUTION 85°C = BLUE
TO BRICK RED
Formula: C6H12O6 (Ratio 1:2:1)
E.g. Fructose, Glucose, Galactose, Ribose
Disaccharides
Properties: Sweet tasting (not as much as monosaccharides), white crystals, soluble in water.
Function: Energy Supply
Formula: C12H22O11 (One H2O molecule taken from the monosaccharide and then doubled)
E.g.
 Lactose – Glucose + Galactose
 Sucrose – Glucose + Fructose
 Maltose – Glucose + Glucose
Polysaccharides
Properties: Insoluble, tasteless, large molecules
Functions: Food store, Structural Carbohydrates
Formula: C6H12O6 x 3000
E.g.
 Cellulose – Straight, no branches, structural cell.
 Glycogen – Coiled molecules, more branches, food store in ANIMALS, stored in
muscle and liver.
 Starch – Coiled molecules, branches, food store in PLANTS. TEST – IODINE = BROWN
TO BLUE/BLACK
Cellulose
Glycogen
Starch
Proteins
Elements – C, H, O, N (P, S)
Structure – AMINO ACID
Side chain one of 20
different types.
A total of 20 naturally occurring Amino Acids:
 Essential (have to come from diet, 8 types)
 Non-essential (produced by the body)
Chains of Amino Acids joined together form 100 to 10,000 units long
Examples:
 Insulin – regulates sugar levels
 Collagen – holds the skin in place
 Tendon – holds muscle to bone
 Muscle – for movement
 Enzymes – speeds up/ controls reactions
 Haemoglobin – carries Oxygen in the blood
TEST – Biuret A + B = BLUE to PURPLE (lilac)
Lipids/Fats
Elements – C, H, O
Properties – High-energy store/content, insoluble in water, less dense than water
Formula/structure: 2 parts –
 Glycerol x 1
 Fatty Acid x3
Soluble Hydrophilic
Insoluble Hydrophobic
Types
1. Saturated – Animal Fats
2. Unsaturated – Plant Fats
Functions:
 Energy Store
 Thermal Insulation
 Electrical Insulation
 Mechanical Insulation
 Buoyancy
TEST – Dissolve in Ethanol, then water = CLOUDY WHITE EMULSION
ENZYMES
 Enzymes are biological catalysts that speed up chemical reactions.
 A type of protein
How enzymes work: Lock and key hypothesis
N.B Enzymes are specific and
only work with one
particular substrate.
Types of Enzymes:
Class
Cardohydrase
Example
Amylase
Amylase
Maltase
Protease
Pepsin
Trypsin
Peptidases
Lipase
Lipase
Digestive Action
Starch to Maltose
Starch to Maltose
Maltose to Glucose
Source
Salivary Gland
Pancreas
Wall of the
Small Intestine
Protein to Peptide Stomach Wall
Protein to Peptide Pancreas
Peptides to Amino Wall of the
Acids
Small Intestine
Lipids to Glycerol Pancreas
and Fatty Acids
Where it Acts
Mouth
Small Intestine
Small Intestine
Stomach
Small Intestine
Small Intestine
Small Intestine
Factors Affecting Enzymes:
 Temperature: When heated to optimum temperature rate of reaction is fastest. At
colder temperature activity stops and when too hot the enzyme denatures.
 Concentration of Enzyme/substrate
 pH: Every enzyme has an optimum pH
A BALANCED DIET
A diet that provides everything the body needs should include:
 Carbohydrates
 Protein
 Lipids
 Vitamins
 Minerals
 Water
 Fibre
Carbohydrates:
Sources – Potato, bread, pasta, cereal
Function – High-energy source
Protein:
Sources – Red meat, nuts, beans
Function – Muscle repair and growth
Lipids:
Sources - Butter, milk, cheese, chocolate
Function – Insulation, energy store
Vitamins:
 A
o Carrots, liver, butter
o Night Vision
 C
o Citrus Fruit, vegetables
o Formation of connective tissue
 D
o Ultra-Violet light
o Bone and tooth building
Minerals
 Iron
o Liver, beef, vegetables
o Haemoglobin in red blood cells
 Calcium
o Milk, cheese
o Bones, teeth and body fluids
Water
Source – Everything
Function – Allows chemical reactions to take place in the body, composes 70% of our body
Fibre
Source – Wholegrain cereal
Function – Maintains a healthy digestive system
What a lack of a balanced diet can cause:
Obesity – eating too much
Anorexia – eating too little
Deficiency Diseases – Scurvy, stunted growth, rickets
Average Calorie Intakes in KJ
 New-born baby – 2000
 Girl Aged 15-17 – 9000
 Male Office Worker – 10,500
 Manual Labourer – 15,000
 Pregnant Woman – 10,000
THE DIGESTIVE SYSTEM
Mouth
Food is chewed and salivary glands release amylase and begin the breakdown of starch
Oesophagus
The tube connecting the mouth to the stomach where food is passed along through
peristalsis
Stomach
Pummels (mechanically breaks down) the food. Releases Hydrochloric Acid to kill bacteria
and create optimum acidic conditions of enzymes such as protease, which is released from
the wall of the stomach to break down protein.
Small Intestine
Most of the digestion happens here. Proteases, carbohydrases and lipases are all released
here. All the products of digestion are absorbed here across the surface of the small
intestine into the blood.
Villus
 Products of digestion are absorbed across the surface of
the villus
 Amino acids, sugars pass into the capillary network by
active transport
 Fatty acids and glycerol pass into the lacteal and are
transported via the lymphatic system.
Adaptations to absorb food efficiently
 Short diffusion distance due to very thin wall
 Microvilli and shape give a very large surface area
 Well connected to capillaries and lacteals so have a
good blood supply and nutrients can be carried away
easily.
Pancreas
Secretes enzymes (proteases, carbohydrases, lipases) and other proteins such as Insulin.
Liver
Produces Bile:
 Emulsifies fats (breaks them down into smaller droplets creating a larger surface
area and more available substrate for the enzymes)
 Neutralises Acid for the stomach
 Creates optimum pH for the pancreatic digestive enzymes
Gall Bladder
Where the bile is stored
Large Intestine
Absorbs excess water. Rectum is where undigested food is stored before it is egested out of
the anus.
Digestive Processes
Ingestion – Consumption of a substance
Digestion – Breaking down of foods into nutrients that can be taken into the blood stream
Absorption – Uptake of substances into the blood stream
Assimilation – Conversion of nutrients into a form usable by the body
Egestion – Discharging of undigested food from the body
PERISTALSIS
The movement of food along the gut is Peristalsis:
Layers of circular and longitudinal muscles push food bolus through the gut via waves of
contraction and relaxation.
RESPIRATION
Respiration is the process of releasing energy from food. There are two types; aerobic and
anaerobic.
Aerobic:
Glucose + Oxygen
Carbon Dioxide + Water (+ ENERGY)
In Animals:
 Using Glucose in this equation is essential to humans as both the heart and the brain
can only use glucose as fuel.
 To prevent cell damage from excess energy a ‘energy-rich molecule’ Adenosine
Triphosphate (ATP) is made.
In Plants
Plants respire just as animals do using it to release energy from photosynthesis
 Plants respire just as animals do using it to release energy made in photosynthesis.
 Oxygen is obtained by diffusion of air through the stomata.
Anaerobic Respiration
This differs between plants and animals:
In Animals:
 Glucose Lactic Acid (+Energy)
 C6H12O6 2 C3H6O3
 When our muscles need energy and we cannot obtain enough oxygen to aerobically
respire our body uses anaerobic respiration to generate energy.
 Less energy is produced than in aerobic respiration
 Lactic Acid is highly toxic so anaerobic respiration can only continue for a short while
 Once exercise has finished the lactic acid must be converted back to glucose using
Oxygen; the is know as PAYING BACK THE OXYGEN DEBT
In Plants:
 Glucose Ethanol (+Energy)
 C6H12O6 2 C2H5OH + 2CO2
 Plants perform this if the roots of a plant get waterlogged and oxygen supply is low.
 Less energy is produced than in aerobic respiration
 Ethanol is poisonous so must be converted back like in animals using oxygen
 This is also known as FERMENTATION - process carried out by yeast and bacteria.
Gas Exchange in Humans
Inhalation
External INTERCOSTAL
muscles contract
Rib cage moves UP and
OUT
Diaphragm CONTRACTS
and FLATTENS
Volume of chest cavity
increases so pressure
decreases
Air is pulled in from the
outside
Exhalation
External INTERCOSTAL muscles
relax (internal intercostal muscles
may contract for forced exhalation)
Rib cage moves DOWN and IN
Diaphragm RELAXES and
CURVES UPWARDS
Volume of chest cavity decreases so
pressure increases
Air is forced out
The air enters the lungs down the trachea, which branches into the right and left bronchi.
Each bronchus then divides further into bronchioles. After about 20 branchings you reach
the air sacs, the alveoli.
Each alveolus has a thin layer of epithelial cells separating the air from blood capillaries - a
bit like the villi in the digestive system.
Oxygen molecules diffuse from the alveoli into the blood stream, where there is a lower
concentration of oxygen. The carbon dioxide diffuses the other way, from the high
concentration in the blood to the alveoli.
Adaptations for gas exchange:
1. Huge total surface area for gas exchange
2. Thin for rapid diffusion
3. Moist surface for gas to dissolve in during diffusion.
4. Excellent blood supply for gas transport and to maintain a good diffusion gradient
Consequences of Smoking to the Lungs and Circulatory System:
 Tar from smoke paralyses ciliated cells, which normally sweep germs upwards in
mucus. Germs therefore remain and cause infections such as Bronchitis.
 Tar causes Emphysema: breakdown of the alveoli and reduces surface area for
oxygen absorption.
 CO causes 15% of haemoglobin to become carbonoxyhaemoglobin which is unable
to pick up oxygen so reduces athletic ability
 CO in smoke promotes ATHEROSCLEROSIS (laying down fatty deposits in the
arteries) insufficient oxygen reaching the heart via coronary arteries may result in a
heart attack.
 Insufficient oxygen to limbs may result in amputation owing to gangrene.
Transport in Humans
Blood:
Made up of 4 main components:
 Plasma
 Red Blood Cells
 White Blood Cells
 Platelets
Plasma – Transports dissolved substances around the blood including:
 Hormones
 Nutrients: water, glucose, amino acids,
minerals and vitamins.
 Waste substances: carbon dioxide and urea.
Red Blood Cells – Transport oxygen around the body and are adapted in several ways to do
this:
 Have no nucleus so extra space for oxygen
 Are a BICONCAVE DISC maximizing surface area for oxygen diffusion
 Contain a protein called HAEMOGLOBIN – combines with oxygen to form
OXYHAEMOGLOBIN to carry it round the body to respiring muscles.
 Tiny so they can fit in small capillaries and carry oxygen everywhere in the body
 There are huge numbers of red blood cells
White Blood Cells – Part of the body’s immune system that identify and destroy pathogens
in the blood. There are two types:
 Phagocytes
 Lymphocytes
Phagocytes – These perform phagocytosis once the have spotted a pathogen by its surface
antigens:
The phagocyte detects the presence of a pathogen, puts out projections called
PSEUDOPODIA that engulf the pathogen into a small vacuole where digestive enzymes are
secreted and the pathogen is digested becoming nutrients for the cell. (The granular
appearance of the cells is due to this breaking down of the pathogen inside the cell)
Lymphocytes – These give a specific response to a particular pathogen. An activated
lymphocyte divides many times and produces proteins called ANTIBODIES which fight
disease in one of the following ways:
 Make bacteria stick together so that phagocytes can ingest them more
easily
 Making bacterial cells burst open
 Sticking to the pathogen so the phagocyte can recognise it
 Neutralising toxins produced by the pathogen
Some lymphocytes remain in the blood as MEMORY CELLS making that person immune to
theta pathogen in the future.
Vaccination and Immunisation:
Vaccination aims to make a person immune to a disease even though they have never
suffered or been ill with it. Once a person has been vaccinated memory cells will work
against that particular pathogen are produced, this meaning that if a pathogen re-enters the
body the immune system can respond so quickly that no symptoms occur.
Vaccination works by injecting people with one of the following:
 A weakened strain of the actual organism (T.B, polio and measles)
 Dead microorganisms (Typhoid and whooping cough)
 Modified toxins of the bacteria (Tetanus and diphtheria)
 Antigens (Influenza)
 Harmless bacteria genetically engineered to carry the antigens of a disease
carrying microorganism (Hepatitis B)
Platelets – These clot the blood to avoid excess bleeding due to an injury and prevent
harmful pathogens entering the body.
Injury – Platelets are activated and release clotting factors – These convert soluble
FIBROGEN into insoluble FIBRIN – Cells are trapped in these threads like a fine net forming a
CLOT or THROMBOSIS by stopping the flow of blood.
THE HEART
N.B
1. The bicuspid and tricuspid valve are
collectively know as the ATRIOVENTRICULAR VALVES
2. The left ventricle has a thicker wall
than the right as the aorta has to
carry blood all the way round the
body requiring a higher pressure
whereas the right ventricle only
pumps to the lungs.
3. The function of the valves is to
prevent BACKFLOW of blood and the
tendons are there to stop the valves
inverting.
The Cardiac Cycle – Blood is moved through the heart by a series of contractions and
relaxations of cardiac muscle in the walls of the four chambers.
1. Blood enters the atria. It cannot yet pass into the ventricles as the bicuspid and
tricuspid valves are closed.
2. The walls of the atria contract. This raises the pressure of the blood in the atria
which forces open the atrio-ventricular valves. Blood passes through these valves
into the ventricles.
3. When the ventricles are full, they contract. This increases the pressure of the blood
in the ventricles, which closes the atrio-ventricular valves, which prevents the
backflow of blood into the atria.
4. The ventricles continue to contract and increase pressure. This forces the semi-lunar
valves open at the base of the aorta and the pulmonary artery. Blood is ejected into
these two arteries. The aorta carrying blood all the way around the body and the
pulmonary artery to the lungs.
5. As the ventricles empty, higher pressure in the pulmonary artery and the aorta
causes the semi-lunar valves to close. The cycle then begins again as the atria fill
with blood.
N.B Contractions is known as SYSTOLE and Relaxation is known as DIASTOLE
Heart Rate: This is usually about 70 beats per minute.
If the body is respiring quickly like when we exercise our heart
rate increases – The increased CO2 level is detected by the
medulla of the brain and the cardiac centre instructs the heart
to speed up or slow down via accelerator or decelerator nerves.
These communicate with a ‘pacemaker’ on the wall of the right
atrium, which controls the heart rate though, electrical
impulses.
When adrenaline is produced by the adrenal gland it
prepares the body for ‘fight or flight’. The heart pumps faster
as blood is diverted to muscles to provide them with oxygen
for respiration so they can move quickly
Coronary Heart Disease
Caused by a blood clot in the coronary arteries that supply blood to the heart. Clotting is
more likely if you have lots of atheroma (fatty deposits) in your arteries. Atheromas are
more likely to develop if you have RISK FACTORS in your life:
 Stress
 Lack of exercise
 Smoking
 Too much saturated fat in the diet; from animal products as this causes
HIGH CHOLESTEROL
 Hereditary factors i.e. you have a predisposition to heart disease in your
genes
 High Blood pressure which can be cause by too much salt in the diet
Reversing what you can of these risk factors makes blockage much less likely.
Circulatory System
Arteries, capillaries and veins
Factor
Function
Nature of Blood Flow
Structure and
Thickness of wall
Width of vessel
lumen
Valves?
Reasons for
structure
Arteries
Carry oxygenated
blood away from the
heart
High pressure, fast,
pulsatile
Capillaries
Carry blood close to
every cell
Very thick, elastic
(STRETCH + RECOIL),
muscle
Narrow
Thin (1 cell thick),
fenestrations
Veins
Carry deoxygenated
blood back to the
heart
Slow (faster than
capillaries), low
pressure
Thin, little muscle or
elastic
Extremely tiny
Wide
No
Withstand, maintain
high blood pressure
No
Short diffusion
distance
Yes
Same blood volume
as arteries at lower
pressure
Slow, dropping
pressure
Plant Nutrition
PHOTOSYTHESIS
Photosynthesis is essentially the opposite to respiration as it uses Carbon Dioxide and Water
to create Glucose and Oxygen. It is essential to life as it converts light energy to chemical
energy.
Its is affected by:
 Light intensity
 Carbon Dioxide concentration
 Temperature
Light intensity
Without enough light, a plant
cannot photosynthesise very
quickly, even if there is plenty of
water and carbon dioxide.
Increasing the light intensity will
boost
the
speed
of
photosynthesis.
Temperature
If it gets too cold, the rate of
photosynthesis will decrease. Plants
cannot photosynthesise if it gets too
hot.
Leaf Structure
Carbon dioxide concentration
Sometimes photosynthesis is
limited by the concentration of
carbon dioxide in the air. Even if
there is plenty of light, a plant
cannot photosynthesise if there
is insufficient carbon dioxide.
Adaption
Purpose
Large surface area
To absorb more light
Thin
Short distance for carbon dioxide to diffuse into leaf cells
Chlorophyll
Absorbs sunlight to transfer energy into chemicals
Network of veins
To support the leaf and transport water and carbohydrates
Stomata
Allow carbon dioxide to diffuse into the leaf
Adaption
Purpose
Epidermis is thin and
transparent
To allow more light to reach the palisade cells
Thin cuticle made of wax
To protect the leaf without blocking out light
Palisade cell layer at top of leaf
To absorb more light
Spongy layer
Air spaces allow carbon dioxide to diffuse through the leaf, and
increase the surface area
Palisade cells contain many
chloroplasts
To absorb all the available light
Plants need to take in a number of elements to stay alive. The most important are:
 Carbon
 Hydrogen
 Oxygen
Plants get hydrogen and oxygen from water in the soil, and carbon and oxygen from carbon
dioxide and oxygen in the atmosphere. Water and carbon dioxide are used to synthesise
food during photosynthesis. Oxygen is used to release energy from food during respiration.
In addition to these three elements, plants need a number of minerals for healthy growth.
These are absorbed through the roots as mineral ions dissolved in the soil water. Two
important mineral ions needed by plants are:
 Nitrate - for making amino acids, which are needed to make proteins
 Magnesium - for making chlorophyll
If a plant does not get enough minerals, its growth will be poor. It will suffer from deficiency
symptoms:


Deficient in nitrate - it will suffer from stunted growth
Deficient in magnesium - it's leaves will turn yellow
Plants obtain water and minerals by absorbing water through the root hair cells through
osmosis and active transport.
Plant Gas Exchange Cont.
Plants carry out both respiration and photosynthesis. PSN fluctuates greatly throughout the
course of the day but respiration remains fairly constant.
Stomata are pores in the leaf that let gases in and out by diffusion. When hot they close and
when they have a good water supply remain open. They are open and closed by guard cells
Leaf adaptation for Gas Exchange –
 Stomata: free unhindered diffusion of CO2 into leaf and O2 out of leaf.
 High Stomata Density: the more stomata the greater the amount of gas exchanged.
 Thin: the shorter the distance the faster the rate of diffusion of CO2 and O2.
 Great Surface Area: the greater the surface area the greater the gas exchanged.
 Flat: maintains the highest possible concentration difference for fastest diffusion.
 Internal Air Spaces: diffusion of CO2 and O2 is much faster in air than in water.
 Moist Internal Surface: required for the absorption and release of gas from the leaf
cells.
PLANT TRANSPORT
Plants have two different types of 'transport' tissue. Xylem transports water and solutes
from the roots to the leaves, phloem transports food from the leaves to the rest of the
plant. Both of these systems are rows of cells that make continuous tubes running the full
length of the plant.
Xylem cells have extra reinforcement in their cell walls, and this helps to support
the weight of the plant. For this reason, the transport systems are arranged differently
in root and stem – in the root it has to resist forces that could pull the plant out of the
ground. In the stem it has to resist compression and bending forces caused by the weight of
the plant and the wind.
Stem – the xylem and phloem are arranged in bundles near the edge of the stem to resist
compression and bending forces.
Comparison of xylem and phloem
Tissue
Process
What is moved
Structure
Xylem
Transpiration Moves water and minerals from roots to Columns of hollow,
leaves
dead reinforced cells
Phloem Translocation Moves food substances (sucrose and Columns of living cells
amino acids) between the leaves and the
rest of plant
Transpiration
The transpiration stream keeps the upright with cells turgid.
Water taken up by the roots of a plant is transported through a plant to the leaves and lost
into the air. The stages of the process are:
 Water enters root hair cells by osmosis.
 The root hair cell is hypertonic to the surrounding soil water. This means that it has a
lower water molecule concentration.
 Water then moves from cell to cell through the root cortex by osmosis along a
concentration gradient; this means that each cell is hypertonic to the one before it.
 In the centre of the root the water enters the xylem vessels.
 Water may move by diffusion through the cell walls and intercellular spaces.
In the leaves, water molecules leave the xylem vessels and move from cell to cell. They move
through the spongy mesophyll layer by osmosis along a concentration gradient. Water then
evaporates into spaces behind the stomata and diffuses through the stomata into the
surrounding air.
Water rises from the roots to the leaves through the xylem vessels because of two
properties of water molecules:
Adhesion
Water rises in the narrow vessels partly because water molecules are attracted to the walls
of the vessels.
Cohesion
Water molecules are attracted to each other, and as water evaporates from the leaves
columns of water are drawn up through the xylem vessels.
The loss of water from the leaves of a plant is called transpiration, and the resulting flow of
water through the plant is called the transpiration stream. The transpiration stream is
important because:
 It carries water for photosynthesis to the palisade cells in the leaves
 The water carries essential mineral salts in solution
 Evaporation from the leaves has a cooling effect
Factors that affect transpiration rate
Factor
Description
Explanation
Light
In bright light
transpiration increases
The stomata (openings in the leaf) open wider to
allow more carbon dioxide into the leaf for
photosynthesis
Temperature Transpiration is faster in
higher temperatures
Evaporation and diffusion are faster at higher
temperatures
Wind
Transpiration is faster in
windy conditions
Water vapour is removed quickly by air
movement, speeding up diffusion of more water
vapour out of the leaf
Humidity
Transpiration is slower in Diffusion of water vapour out of the leaf slows
humid conditions
down if the leaf is already surrounded by moist
air
Plant Coordination and Response
Plants do not move from place to place but others parts of the plant such as the stem and
flowers respond to stimuli by twisting, turning, opening and closing – what are called
TROPISMS or NATISMS respectively
There are many different types:
 Negative or Positive
 Phototropism/Photonastic
 Geotropism
 Hydrotropism
 Thigmotropism
 Hydrotropism
Auxin is a chemical messenger that in the stem and root of a plant causes it to grow in a
particular direction. In the shoot it causes the shoot to bend towards the source of light.
The Auxin accumulates on the dark side causing cells on that side to elongate and bend
towards the light.
Plant Reproduction
There are two types of reproduction Asexual and Sexual. Plants can do both naturally and
artificially.
Asexual Reproduction
Bulbs – Potatoes, daffodils
Cuttings – Geranium
Runners – Strawberry
Sexual Reproduction
The production of an organism from two parents making use of their sex cells.
Advantages
There is variation in the offspring
New varieties are produced
Disadvantages
Two parents are always needed
Growth of a plant from seed is vegetative
propagation
In plants seeds are produced and dispersed
away from the parent plant, thus reducing
the competition
Plant Structure:
Functions of different parts of a flower:
Stamens make the male gamete, which is stored in pollen grains.
Carpel, the female part of a flower, makes the female gametes. These are stored or are
present in ovules.
Male gametes from the pollen grains travel (get dispersed) and then pollinate and fertilise
the female gametes in the ovules.
The fertilised ovules grow to become seeds.
Pollination:
Cross Pollination
Self Pollination
Transfer of pollens from the anther of a
The pollen is transferred to the stigma of the
plant to stigma of another plant of the same same flower
species
Needs agent for pollinations; water, insects, Less chances of failure of pollination
birds or man
Results in healthy and strong offspring
Purity of race is maintained
Results in production of large number of
Avoids wastage of pollen grain
seeds
New varieties with useful characters are
Flowers do not need to be large and showy
produced
Cross pollination is used for producing new
Continuation of self pollination results in
kinds of vegetables and fruits
weak progeny
A plant requires a lot of energy and food
New varieties and species of plants are not
material to bring about pollination
produced
Differences:
Feature of Flower
Position of Stamens
Position of Stigma
Type of Stigma
Size of Petals
Colour of Petals
Nectaries
Pollen Grains
Insect Pollinated
Enclosed within the flower so that
the insect must make contact
Enclosed within the flower so that
the insect must make contact
Sticky so pollen grains attach from
insects
Large to attract insects
Brightly coloured
Wind Pollinated
Exposed so pollen can be
blown away easily
Exposed to catch pollen
blowing in the wind
Feathery to catch pollen
blowing in the wind
Small
Usually green but not
brightly coloured
Present as nectar is a reward for the Absent
insects
Larger, sticky grains to stick to the Smaller, smooth inflated
insects body
grains to carry in the wind
1 - filament
2 - anther
3 - stigma
4 - style
5 - petal
6 - ovary
7 - sepal
8 - flower stalk
9 - stamen
10 - carpel
11 - perianth
Growth of pollen tube and fertilisation
1. Pollen grain of the same species reach the
stigma
2. Pollen tubes are formed, triggered by sugary
solution on the stigma
3. The pollen tube grows down through the style
and reaches the ovule
4. Pollen tube contains two male gametes
5. The tube pushes its way through the ovary wall
and through the micropyle of the ovule
6. Fertilisation occurs
Formation of seed and fruit:
 After fertilisation occurs the sepals, petals, stamens, styles and the stigma of the
flower wither and fall off
 The ovary grows rapidly and forms a seed
 The seed now contains the embryo (tiny root radicle, shoot plumule) and the
cotyledons.
 The wall of the ovule thickens to form the seed coat/testa
 The wall of the ovary grows to form the fruit. It may be fleshy or dry
 A fruit protects and distributes the seed
Seed dispersal can occur by wind or animal:
Wind: seeds bear parachutes like wing, fine hairs, are very light
Animals: belong to succulent fruits or hooked fruits
Factors that affect Germination:
Water – needed to activate enzymes for converting soluble food stores in the cotyledons to
soluble food, which can be used for growth by the baby plant.
Oxygen – needed for respiration as soon as growth process begins and required for energy
to mobilise the chemical changes.
Warmth – enzymes present in the seed get activated and work best at optimum
temperature (20-40°C), which triggers growth.
Sexual Reproduction in Humans
1. Testes: males gonads that produce sperm
2. Scrotum: a sac that holds testis outside the body
3. Epididymis: a mass of tubes in which sperms are
stored
4. Seminal vesicle: adds fluid and nutrients to
sperm to form semen
5. Sperm duct: muscular tube which links the testis
to the urethra to allow the passage of semen
containing sperm
6. Prostate gland: adds fluid and nutrients to form
semen
7. Urethra: to pass semen containing sperm
through the penis also carries urine from the
bladder at times
8. Penis: organ to transfer sperm to the vagina
Secondary sexual characteristics: broadening of
shoulders. Growth of body hair, deepening of voice,
increased development of musculature, penis becomes
larger, and testes start to produce sperm
1. Ovary: contains follicles in which ova are
produced
2. Oviduct: carries the ovum to the uterus.
This is the fallopian tube and the site of
fertilisation
3. Funnel of oviduct: direct and extends from
the ovary to oviduct
4. Uterus: where the foetus develops
5. Cervix: a ring of muscles that separates the
vagina from the uterus
6. Vagina: receives male penis during
intercourse. Sperm is deposited here.
7. Urethra: carries urine form the bladder
8. Puberty: period when reproductive organs
become functional
Secondary sexual characteristics: breasts grow,
nipples enlarge, hair develops under arms and in
pubic area, uterus and vagina become larger,
ovaries start to release eggs and menstruation
begins and hips become wider.
Menstruation
The periodic discharge of blood, mucus and epithelial cells from the lining of the uterus
through the vaginal opening is called menstruation. It happens every 28 days and lasts for 45 days.
Ovum is produced every 28th day
Ovum cannot be fertilised after 48 hours
Sperms live for 48 hours
Fertilisation:
 Sperm reaching the fallopian tube has a chance to meet ovum
 It penetrates the ovum and the zygote is formed
 The zygote rapidly divides by mitosis as it travels down through the fallopian tube
forming a small ball of many cells called a blastula
 This ball of cells becomes embedded or implanted in the mucosa of the uterus
Development of foetus:
 In humans, the egg is without reserve nutrients
 The embryo gets nutrients and oxygen from the mother until birth
 The embryo develops three embryonic membranes that surround it
Amniotic sac – membrane formed from the cell of the embryo, which contains amniotic fluid
and encloses the developing foetus and prevents entry of bacteria
After implantation an organic connection is established between the extra embryonic
membranes of the embryo and the uterine wall of the mother known as the placenta.
The functions of the placenta are:
1. Receiving dissolved food substances from the mothers blood
2. Receiving oxygen from the mothers blood
3. Excreting CO2, nitrogenous waste and urea
4. Serving as an important but temporary endocrine gland
Antenatal care:
A balanced diet: Protein for growth, calcium for skeleton, iron for RBC development of
skeleton, vitamin c for good bones and skin, carbohydrates for fats and energy, vitamins and
minerals to prevent deficiency
Process of Birth:
1. Labour triggered by hormone oxytocin
2. Muscular walls of the uterus start to contract
3. The pressure breaks the amniotic sac
4. Contractions become more frequent pushing the baby down towards the cervix
5. Cervix becomes dilated allowing the baby to pass
6. The vagina stretches for the baby to pass
7. The baby is still attached to the placenta by the umbilical cord
8. Placenta breaks away from the uterine wall and passes out (after birth)
9. Umbilical cord is cut and tied
Birth Control:
1. Mechanical Methods
a. Condom
b. Femidom
c. Diaphragm
d. IUD (intrauterine device)
2. Natural Methods
a. Withdrawal
b. Abstinence
c. Rhythm
3. Chemical Methods
a. The pill
b. Spermicidal
4. Surgical Methods
a. Vasectomy
b. Laparotomy/ tubectomy
Homeostasis: The maintenance of a constant internal environment
Things that are kept constant:
 Level of sugar
 Temperature: Thermoregulation
 Water level: Osmoregulation
 Level of salt
Waste products like urea cannot exceed a certain level
Blood pH would become too low if levels of CO2 or lactic acid get too high
Enzymes are adversely affected by changes in pH or temperature
Changes in a body system are detected by RECEPTORS and EFFECTORS bring about the
necessary corrections.
Sugar (HYPOGLYCAEMIC AND HYPERGLYCAEMIC)
Two hormones control levels of glucose: Insulin and Glucagon
Thermoregulation:
Mammals and birds have a constantly warm body temperature regardless of their
surroundings and are therefore described as being HOMEOTHERMIC. As their body heat is
primarily generated by their own chemical reactions, they are also described as
ENDOTHERMS. In contrast cold-blooded animals get body heat from the sun –
ECTOTHERMIC. Mammals including humans have a THERMOREGULATORY CENTRE in the
HYPOTHALAMUS of the brain, which monitors blood temperature. This will regulate body
temperature by sending nerve impulses that bring about physical changes such as sweating.
There are also temperature receptors in the skin that inform the hypothalamus of changes
in environmental temperature.
HOT
1. When our skin hot it acts to increase
heat loss
2. The hair erector muscle relax and
make the hair lies flat against the skin
trapping less and more heat is lost by
radiation
3. Sweat glands make more sweat which
evaporates from the surface taking
away heat
4. VASODILATION blood vessels widen
and increases heat loss by radiation
COLD
1. Our skin acts to decrease heat loss
when it is cold
2. The hair erector muscles contract and
make the hair stand more upright. This
traps warm still air close to the surface
of the skin. Less heat is lost by
radiation.
3. Sweat glands stop making sweat
4. VASOCONSTRICTION blood vessels
near the skin get narrower and less
heat is lost by radiation
Osmoregulation
This is controlled by the anti-diuretic hormone (ADH)
ADH works by making the collecting duct of the nephron in the kidney more permeable to
water. If there is too high concentration of ADH in the blood the collecting ducts will become
more permeable and more water will move back from the urine to the blood stream; when
there is too little water in the blood. If there is too much water in the blood then less ADH is
released. This is an example of NEGATIVE FEEDBACK.
Excretion: is removal from the body of the waste products of metabolism
The Kidney:
The Nephron:
N.B
Kidneys lie at the back of the abdomen
Kidneys require a unusually high blood supply to
maintain high blood pressure
Women suffer from bladder infections more
because the urethra is shorter and close to the
anus making a greater chance of transfer of
bacteria
We have two separate kidneys in case one is
damaged:
If a kidney is damaged then people need a
transplant or dialysis.
Dialysis: a machine that when connected to the
body removes urea and other toxins.
Transplants: are considered easy for kidneys due
to the fact that kidneys are only connected via the
renal artery and vein
Arteriole: takes blood into the capillaries of the
glomerulus. The arteriole is wider on the way in
than on the way out the blood pressure is very
high
Glomerulus: a knot of capillaries
Bowman’s Capsule: water and small molecules
(amino acids, salts, urea and glucose) enter here
by ULTRAFILTRATION
First Coiled Tubule: Useful molecules such as
glucose and amino acids and water are
SELECTIVELY REABSORBED here.
Loop of Henlé: This concentrates the filtrate and
allows more reabsorption of water.
Second Coiled Tubule: more reabsorption
Collecting Duct: Is where the exact water
content of the filtrate is determined by the
hormone ADH and where the finished filtrate,
urine, emerges.
N.B Excretion can also occur as sweating through pores of the skin and exhalation of Carbon
Dioxide from the lungs
The Endocrine System
Produces and secretes chemical messengers called hormones.
Gland
Pituitary
Hormone Produced
1.ADH
2.LH
3.FSH
Thyroid
Adrenal
Pancreas
Thyroxin
Adrenaline
Insulin
Ovary
1.Oestrogen
2.Progesterone
Testes
Testosterone
Action
1.Water balance
2.Ovulation, progesterone
production
3.Growth of follicle
Controls metabolic rate
Prepares the body for action
Control of blood glucose
level
1.Controls puberty and
menstrual cycle
2.Maintains pregnancy
Controls puberty in male
Effects of Adrenaline:
Target Organ
Effects of Adrenaline
Biological
advantages
Heart
Beats faster
Pumps more blood
to get oxygen and
glucose
Breathing center of the Faster and deeper More oxygen into
brain
breathing
blood and carbon
dioxide out of blood
Arterioles of skin
Vasoconstriction
Blood getting where
it is most needed
Arterioles of digestive Constricts them
Blood getting where
system
it is most needed
Muscles of alimentary Relax
To save energy
canal
Muscles of body
Tenses them
Ready for action
Liver
Conversion
of Used for respiration
glycogen to glucose
Fat deposits
Fats to fatty acids
Used for respiration
Effect
Thumping heart
Panting
Person goes paler
Dry mouth
‘Hollow’ stomach
feeling
Tense feeling
No sensation
No sensation