IGCSE Biology CIE

What is the order of classification?

Kingdom

Phylum

Class

Order

Family

Genus

Species

Name the types of vertebrates and how to identify them.

Fish - scales, fins and gills

Amphibian - moist skin, no teeth

Reptile - dry scales, leathery shells

Bird - feathers, beak

Mammal - fur, mammary glands

Name the types of invertebrates and how to identify them.

Mollusc - hard shell, no jointed limbs or segments

Arthropod - segments, jointed limbs, exoskeleton

Annelid - segments, exoskeleton, no jointed limbs

Nematode - no segments, jointed limbs or exoskeleton

Name the types of arthropods and how to identify them.

Insects - 3 body segments, wings usually on adults

Crustaceans - 2 pairs of antennae, more than 5 pairs of legs

Arachnids - 2 body segments, 4 pairs of legs

Myriapods - many segments, 1-2 pairs of legs per segment

Compare monocotyledons and dicotyledons.

Monocotyledons:

Veins usually parallel, organised vascular bundles, floral parts usually in multiples of 3

Dicotyledons:

Veins usually netlike, vascular bundles in a ring, floral parts usually in multiples of 4 or 5

List the characteristics of life.

Movement

Respiration

Sensitivity

Growth

Reproduction

Excretion

Nutrition

Name 2 features of cells that are found in all organisms.

Ribosomes - protein synthesis

Enzymes - respiration

Describe the structure of a eukaryotic cell.

Nucleus - contains DNA

Cytoplasm - jelly-like fluid in the cell

Cell Membrane - controls what goes through cell

Mitochondria - produces energy

Ribosomes - produces polypeptide proteins

Endoplasmic Reticulum - carries ribosomes

Golgi Apparatus - sorts macromolecules for delivery

Lysosome - main sites of intracellular digestion

Describe the structure of a plant cell.

Chloroplast - carries out photosynthesis

Vacuole - storage

Cell wall - provides rigidity

*Chlorophyll - used for photosyntheses

Nucleus, cytoplasm, cell membrane, mitochondria, ribosome, ER also present

List the different levels of organisation.

Cells

Tissue

Organ

Organ System

Organism

Calculate magnification.

Image/Actual

millimetre = 1000000 nanometres

Define diffusion.

Diffusion: the net movement of particles from a region of their higher concentration to a region of their lower concentration down a concentration gradient, as a result of their random movement.

Discuss the factors of diffusion.

Higher temperature -> more energy in particles

Greater concentration -> more collisions

Smaller molecule size -> lighter, travels faster

Greater surface area -> more is exposed to react

Define osmosis.

Osmosis: the net movement of water molecules from a region of higher water potential (dilute solution) to a region of lower water potential (concentrated solution), through a partially permeable membrane.

State the effects of osmosis on cells in different concentrations.

Plant cells:

Low water potential - plasmolysis, flaccid\nHigh water potential - turgid

Eukaryotic cells:

Low water potential - plasmolysis, crenation

High water potential - haemolysis (ruptures)

Define active transport.

Active Transport: the movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration.

Explain processes involving diffusion, osmosis and active transport.

Diffusion: respiration by lungs in animals

Osmosis: transpiration by spongy mesophyll in plants

AT: ion uptake by root hair cells in plants

List the chemical elements that make up:

- carbohydrates

- fats

- proteins

Carbohydrates: carbon, hydrogen and oxygen

Fats: fatty acids and glycerol

Proteins: nitrogenous organic compounds composed of amino acid chains

Name the monomers of:

- starch and glycogen

- cellulose

- proteins

- fats and oils

Starch and glycogen: Glucose

Cellulose: Glucose

Proteins: Amino acids

Fats and oils: Fatty acids and glycerol

Describe the structure of DNA.

- two strands coiled together to form a

double helix

- each strand contains chemicals called

bases

- cross-links between the strands are formed

by pairs of bases

- the bases always pair up in the same way:

A with T, and C with G

Describe the metabolic processes in which water is an important solvent.

Digestion, excretion and transport.

Explain how enzymes do their jobs.

The enzyme grabs on to the substrate at the active site.

The combination is called the enzyme/substrate complex.

Catalysis occurs.

The enzyme releases the product.

State and explain factors that control the rate of enzyme reactions.

Temperature: temperature increases rate until the enzyme becomes denatured.

pH: Changes in pH also alter an enzyme's shape. The optimum pH for an enzyme depends on where it normally works.

Give the word and chemical equation for photosynthesis.

carbon dioxide + water → glucose + oxygen

6CO2 + 6H2O → C6H12O6 + 6O2

Outline the use and storage of the

carbohydrates made in photosynthesis.

Amino acids - protein

Sucrose - fruit

Fats and oils - cell membrane

Starch - storage

Cellulose - cell wall

Nucleic acid - DNA

Respiration - energy

Explain the limiting factors of photosynthesis in different environmental conditions.

Increasing the light intensity will boost the speed of photosynthesis, until it levels off at a maximum point.

Increasing the carbon dioxide concentration will boost the speed of photosynthesis, until it levels off at a maximum point.

If it gets too cold, the rate of photosynthesis will decrease. Plants cannot photosynthesise if it gets too hot. The optimum temperature for photosynthesis is between 20-30ºC.

Describe how greenhouses speed up the rate of photosynthesis.

Artificial light allows photosynthesis to continue beyond daylight hours. Bright lights also provide a higher-than-normal light intensity.

Artificial heating allows photosynthesis to continue at an increased rate.

Additional carbon dioxide entered from the atmosphere inside the greenhouse allows photosynthesis to continue at an increased rate.

Explain how the internal structure of a leaf is

adapted for photosynthesis.

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

Explain the effects of nitrate ion and magnesium ion deficiency on plant growth.

Lack of nitrate ions: Bottom leaves turn yellow and shrivel

Lack of magnesium ions: Yellow spots on leaves

Describe the importance of nitrate ions and magnesium ions for plants.

Nitrate ions for making amino acids.

Magnesium ions for making chlorophyll.

Explain how age, gender, activity and pregnancy affect human dietary needs.

Age increases the amount of energy needed until adulthood. From then on, we require less energy as we age.

Men tend to need more energy than women.

More active people need more energy.

Pregnant women need more energy because they have a greater mass.

Describe the effects of malnutrition.

Starvation - suffering caused by lack of food

Constipation - too much diary, not enough fibre Obesity - too much fat

Coronary heart disease - caused by obesity

Scurvy - deficiency of vitamin C

Describe the dietary importance of:

- carbohydrates

- fats

- proteins

- vitamins C and D

- calcium and iron

- fibre

- water

Carbohydrates: starches for energy

Fats: insulation, fuel

Proteins: growth, repair

Vitamin C: connective tissue, respiration catalyst

Vitamin D: absorption, deposition

Calcium: teeth, blood clotting

Iron: haemoglobin, muscles

Fibre: retaining water, gut movement

Water: solvent to absorb and dissolve

Explain the causes and effects of vitamin D and

iron deficiencies.

Vitamin D deficiency: rickets

- softer bones, more brittle

Iron deficiency: anaemia

- less haemoglobin, less oxygen in blood

Explain the causes and effects of protein-energy malnutrition.

Kwashiorkor - swollen stomachs

Marasmus - lack of energy, stunted growth

Both can lead to permanent physical and mental problems.

Explain how cholera bacterium infect the body and cause diarrhoea.

Cholera bacterium produces a toxin that causes secretion of chloride ions into the small intestine, causing osmotic movement of water into the gut, causing diarrhoea, dehydration and loss of salts from blood.

Describe the structure of human teeth.

Consists of incisors, canines, premolars and molars.

The structure of a tooth includes enamel, dentine, pulp, nerves, cement and gums.

Describe the process of dental decay.

Food deposits and bacteria form a layer called plaque. Bacteria on the plaque feed on sugars, producing acid. This acid dissolves enamel, forming a hole.

Dentine underneath the enamel is softer - it dissolves more rapidly (painful).

If the hole reaches the pulp cavity, bacterial infection can get to the nerve. This results in toothache and possibly, an abscess (an infection in the jaw).

Describe ways to prevent dental decay.

- Avoiding foods with a high sugar content

- Using toothpaste and drinking water containing fluoride

- Regular, effective brushing to prevent the build-up of plaque

State the functions of amylase, protease (pepsin and trypsin), and lipase.

Amylase breaks down starch to simpler sugars

Protease breaks down protein to amino acids

- Pepsin in stomach, trypsin in small intestine

Lipase breaks down fats to fatty acids and glycerol

Describe the digestion of starch in the alimentary canal.

Amylase is secreted into the alimentary canal and breaks down starch to maltose.

Maltose is broken down by maltase to glucose on the membranes of the epithelium lining the small intestine.

Explain the functions of the hydrochloric acid in

gastric juice.

The low pH of hydrochloric acid:

- denatures enzymes in harmful microorganisms in food

- gives the optimum pH for pepsin activity

Outline the 2 major roles of bile.

1. Neutralising the acidic mixture of food and gastric juices entering the duodenum from the stomach, to provide a suitable pH for enzyme action

2. Emulsifying fats to increase the surface area for the chemical digestion of fat to fatty acids and glycerol by lipase.

Describe the structure of a villus and its adaptations.

- Walls are only one cell thick to allow dissolved molecules to pass through quickly

- Contain many blood capillaries which absorb glucose and amino acids

- Contain lacteals which are part of the lymphatic system and absorb fats

- Many of them to increase the surface area inside the small intestine.

State the functions of xylem and phloem.

Xylem: transports water and ions from roots to leaves

Phloem: transports sucrose and amino acids in all directions of the plant

Describe the structure of xylem and phloem.

Xylem: dead cells, thick, walls contain lignin for support

Phloem: made of living cells with sieve tubes

Describe the path of water uptake in a plant from the point it enters a root hair cell to leaving the plant and entering the atmosphere.

1. Osmosis causes water to pass into the root hair cells, through the cortex and into the xylem vessels

2. Water moves through the xylem vessels in a continuous transpiration stream, that draws up a column of water molecules, held together by cohesion.

3. Osmosis drags water through the spongy mesophyll.

4. Water vapour evaporates our of the stomata.

Describe the adaptations of root hair cells.

- Protrusion to increase surface area, which increases the rate of the absorption of water by osmosis and ions by active transport

- Large vacuole to allow more storage space for water

- Contain lots of mitochondria to have sufficient energy for active transport

Explain how and why wilting occurs.

Plants wilt to slow down the rate of transpiration when water supply is scarce.

Explain the effects of variation of temperature and humidity on transpiration rate.

Temperature - Transpiration is faster in higher temperatures because evaporation and diffusion are faster at higher temperatures.

Transpiration - Transpiration is slower in humid conditions because the diffusion of water vapour out of the leaf slows down if the leaf is already surrounded by moist air.

Explain translocation.

The movement of sucrose and amino acids in phloem from a source to a sink.

Parts of a plant may act as a source and a sink at different times during the life of a plant.

Outline what a circulatory system is.

A system of blood vessels with a pump and valves to ensure one-way flow of blood.

Compare the single and double circulation in a fish and mammal respectively.

Fish:

Blood travels from the heart to the gills, where it absorbs oxygen and releases carbon dioxide.

It then flows from the gills to the organs and tissues in the rest of the body, and back to the heart. There is just one circuit from the heart.

Mammals:

1. Blood passes from the heart to the lungs - where it absorbs oxygen and releases carbon dioxide - then back to the heart.

2. Blood passes from the heart to the organs and tissues in the body, and back to the heart.

Explain the advantages of double circulation.

Higher blood pressure, so a greater flow of blood to the tissues.

Explain the relative thickness:

- of the muscle wall of the left and right

ventricles

- of the muscle wall of the atria compared to

that of the ventricles

The left ventricle has a thicker muscle wall than the right ventricle. This is because the left ventricle has to pump blood all the way around the body, but the right ventricle only has to pump it to the lungs.

The thickness of the arteries are greater than that of the veins. The arteries need to withstand higher blood pressure because they travel into capillaries, so the walls need to be thicker.

Outline blood flow in the heart.

1a) Deoxygenated blood from the vena cava enters the right atrium.

1b) Oxygenated blood from the pulmonary vein enters the left atrium.

2a) Right atrium contracts to pump blood through the tricuspid valve into the right ventricle.

2b) Left atrium contracts to pump blood through the bicuspid valve into the left ventricle.

3a) Right ventricle contracts, semilunar valve opens and deoxygenated blood travels through the pulmonary artery to the lungs.

3b) Left ventricle contracts, semilunar valve opens and oxygenated blood travels through aorta to the rest of the body.

Explain the importance of the septum.

To separate oxygenated and deoxygenated blood.

Explain how exercise increases heart rate.

During exercise, the muscle cells respire more than they do at rest.

- Oxygen and glucose must be delivered to them more quickly

- Waste carbon dioxide must be removed more quickly

This is achieved by speeding up heart rate and breathing rate.

Describe ways to measure heart rate.

ECG, pulse rate and listening to sounds of valves closing.

Discuss the roles of diet and exercise in the prevention of coronary heart disease.

High levels of saturated fats in the diet lead to a build of cholesterol in the arteries, causing a plaque and narrowing of the arteries.

Exercise can help lower blood pressure and cholesterol levels.

Describe coronary heart disease and state the possible risk factors.

The blockage of coronary arteries

Risk factors: diet, stress, smoking, genetic predisposition, age and gender

Describe ways in which coronary heart disease may be treated.

Drug treatment with aspirin and surgery (stents, angioplasty and by-pass).

Explain how the structures of arteries, veins and capillaries are adapted for their functions.

Arteries: thick outer walls, thick layers of muscle and elastic fibres.

Veins: thin walls, thin layers of muscle and elastic fibres, valves to ensure blood flows in one direction

Capillaries: thin walls (only one cell thick) to make diffusion more effective

State the function of arterioles, venules and shunt vessels.

Aterioles - To regulate the flow of blood into different tissues.

Venules - Allow deoxygenated blood to return from the capillary beds to the veins, which then transports the blood back to the heart.

Shunt vessels - Provide channels that bypass capillary beds.

Outline the lymphatic system.

It is a collection of lymph vessels and glands. It has 3 main roles:

Fluid balance - return tissue fluid to the blood

Protection from infection - produce white blood cells lymphocytes

Absorption of fats - transport digested fats from villi to blood stream

List the components of blood.

Blood plasma

Red blood cells (Eurythrocyte)

White blood cells

Platelets

State the functions of each component in the blood.

Red blood cells: Transporting oxygen, including the role of haemoglobin

White blood cells: phagocytosis and antibody production

Platelets: clotting

Plasma: the transport of blood cells, ions, soluble nutrients, hormones and carbon dioxide

State the functions of lymphocytes and phagocytes.

Lymphocytes - antibody production

Phagocytes - phagocytosis

Describe the process of clotting and explain why it is necessary.

1. Blood vessel wall broken.

2. Platelets activated.

3. Platelets interact with fibrinogen, a soluble plasma protein, to form insoluble fibrin.

4. Fibrin forms a mesh, producing a clot which plugs the break.

- prevents blood loss and the entry of pathogens

Describe the transfer of materials between capillaries and tissue fluid.

Capillaries are bathed in tissue fluid.

Tissue fluid provides cells with glucose and oxygen for respiration and removes waste products from cells by diffusion.

Describe how antibodies defend the body.

They lock on to antigens leading to direct destruction of pathogens, or marking of pathogens for destruction by phagocytes

Explain why specific antibodies and needed to fight specific pathogens.

Each pathogen has its own antigens, which have specific shapes, so specific antibodies which fit the specific shapes of the antigens are needed.

State the different defence systems of the body.

Mechanical barriers: skin and hairs in the nose

Chemical barriers: mucus and stomach acid

Cells: limited to phagocytosis and antibody production by white blood cells (which can be enhanced by vaccination)

Explain the process of vaccination.

1. Harmless pathogen given which has antigens

2. Antigens trigger an immune response by lymphocytes which produce antibodies

3. Memory cells are produced that give long-term immunity

Explain ways to control the spread of disease.

Hygienic food preparation, good personal hygiene, waste disposal and sewage treatment.

Describe how pathogens may be transmitted.

Direct contact - blood or other body fluids

Indirectly - from contaminated surfaces or food, from animals, or from the air

Outline Type 1 diabetes.

The immune system mistakenly targets and destroys beta cells in the pancreas, which produce insulin.

Without insulin, people are unable to convert glucose into glycogen for storage.

List the features of gas exchange surfaces in humans that make diffusion faster.

Large surface area

Thin surface

Good blood supply

Good ventilation with air

Explain the differences in composition between inspired and expired air.

Oxygen - more oxygen in inspired air

Carbon dioxide - more carbon dioxide in expired air

Water vapour - more saturated in expired air

Outline the process of human breathing.

Inhalation:

- Diaphragm muscles contract

- External intercostal muscles contract

- Internal intercostal muscles relax

- Rib cage pulled up and out

- Volume of thoraic activity increases

- Pressure in lungs decrease

Exhalation:

- Diaphragm muscles relax

- External intercostal muscles relax

- Internal intercostal muscles contract

- Rib cage falls down and inwards

- Volume of thoraic activity decreases

- Pressure in lungs increase

Explain how the gas exchange system is protected from pathogens and particles.

Goblet cells - secrete mucus

Mucus - sticky substance to trap dust and pathogens

Ciliated cells - moves mucus up respiratory tract into oesophagus where pathogens are killed by stomach acids

Explain how physical activity and deeper breathing cause breathing rate to increase.

Causes an increase of carbon dioxide concentration in the blood due to it being a waste product of respiration, which is detected by the brain, causing an increased rate of breathing.

State the uses of energy in the body of

humans.

Muscle contraction, protein synthesis, cell division, active transport, growth, the passage of nerve impulses, maintenance of a constant body temperature.

Give the word and chemical equation for aerobic respiration.

glucose + oxygen → carbon dioxide + water

C6H12O6 + 6O2 → 6CO2 + 6H2O

Give the word and chemical equations for anaerobic respiration.

In muscles: glucose → lactic acid

Yeast: glucose → alcohol + carbon dioxide

C6H12O6 → 2C2H5OH + 2CO2

Compare aerobic and anaerobic respiration (2).

1. Aerobic respiration requires oxygen.

2. Aerobic respiration releases a lot more energy than anaerobic respiration.

Outline how the oxygen debt is occurs and is removed during recovery.

1. Lactic acid builds up in muscles and blood during vigorous exercise causing an oxygen debt.

2. Fast heart rate continues after exercise to transport lactic acid in blood from muscles to the liver.

3. Deep breathing continues after exercise to supply oxygen to completely oxidise lactic acid into carbon dioxide and water.

Describe the role of the liver.

- Assimilation of amino acids by converting them into proteins

- Site of break down of alcohol and other toxins

- Deamination

- Produces bile for digestion

- Produces fibrinogen for clotting

- Helps fight infection by removing bacteria from the blood

- Forms urea

Describe what effects the volume and concentration of urea.

Water intake -

Temperature -

Exercise -

Outline the structure and functioning of a kidney tubule.

Glomerulus - the filtration from the blood of water, glucose, urea and salts

Convoluted tubule - the reabsorption of all of the glucose, most of the water and some salts back into the blood, leading to the concentration of urea in the urine as well as loss of excess water and salts

Outline how kidney dialysis works.

1. Blood taken from arm and passed through a tube bathed in fluid.

2. The fluid contains:

- glucose concentration similar to a normal level in the blood

- a concentration of ions similar to that found in normal blood plasma

- no urea

3. Substances diffuse in and out of the blood through a partially permeable membrane and the blood is sent back to the body.

4. Blood sent back to body has a correct salt balance, glucose concentration and urea has been removed.

Discuss the advantages and disadvantages of kidney transplants, compared with dialysis.

Dialysis:

- no rejection problems, immediate treatment

- expensive, lengthy sessions, uncomfortable

Kidney transplant:

- one-time procedure, return to normal lifestyle

- long waiting list, risk of rejection, risk of surgery

Describe what the human nervous system consists of.

The central nervous system (CNS) - the brain and spinal cord

The peripheral nervous system - nerve cells that carry information to or from the CNS

Distinguish between voluntary and involuntary actions.

Voluntary - involves conscious thought, a decision is made to carry out an action

Involuntary- not consciously controlled, reflexes that help survival or for protection

Describe a simple reflex arc (involuntary).

Stimulus

Receptor

Sensory neurone

Relay neurone

Motor neurone

Effector

Response

(synapses ensure that impulses travel in one direction only)

Describe the structure and function of a synapse.

Neurotransmitter containing vesicles

Synaptic cleft

Describe how informations passes through the nervous system.

1. An electrical impulse travels along an axon.

2. This triggers the nerve-ending of a neuron to release chemical messengers called neurotransmitters.

3. These chemicals diffuse across the synapse and bind with receptor molecules on the membrane of the next neuron.

4. The receptor molecules on the second neuron bind only to the specific chemicals released from the first neuron. This stimulates the second neuron to transmit the electrical impulse.

Outline the effect of drugs on the nervous system.

Stimulants cause more neurotransmitter molecules to diffuse across the synapse.

Depressants stop the next neurone sending nerve impulses. They bind to the receptor molecules the next neurone that needs to respond to the neurotransmitter molecules.

Describe the function of each part of the eye.

Cornea - refracts light

Iris - controls how much light enters pupil

Lens - focuses light onto retina

Retina - contains light receptors, some sensitive to light of different colours

Optic nerve - carries impulses to the brain

Explain the pupil reflex in bright and dim light.

In bright light:

- Radial muscles of the iris relax.

- Circular muscles of the iris contract.

- Less light enters the eye through the contracted pupil.

In dim light:

- Radial muscles of the iris contract.

- Circular muscles of the iris relax.

- More light enters the eye through the dilated pupil.