Biology IGCSE

What is movement (as a characteristic of life)?

An action by an organism or part of an organism causing a change of position or place

What is respiration (as a characteristic of life)?

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

What is sensitivity (as a characteristic of life)?

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

What is growth (as a characteristic of life)?

A permanent increase in size and dry mass

What is reproduction (as a characteristic of life)?

The processes that make more of the same kind of organism

What is excretion (as a characteristic of life)?

The removal of the waste products of metabolism and substances in excess of requirements

What is nutrition (as a characteristic of life)?

The taking in of materials for energy, growth and development

How can organisms be classified into groups?

By the features that they share

What is a species?

A group of organisms that can reproduce to produce fertile offspring

What is the binomial system?

An internationally agreed system in which the scientific name of an organism is made up of two parts showing the genus and species

What are dichotomous keys used for?

Constructed and used, based on identifiable features, to identify organisms

What do classification systems aim to reflect?

Evolutionary relationships

What are sequences of bases in DNA used for in classification?

As a means of classification

How does DNA base sequence relate to relatedness of organisms?

Groups of organisms that share a more recent (closer) ancestor have base sequences in DNA that are more similar than those that share only a distant ancestor

What features place animals and plants into the appropriate kingdoms?

The main features used to distinguish animal and plant kingdoms

Name the main groups of vertebrates.

Mammals, birds, reptiles, amphibians, fish

Name the main groups of arthropods.

Myriapods, insects, arachnids, crustaceans

What are the five kingdoms?

Animal, plant, fungus, prokaryote, protoctist

What plant groups must you know for classification?

Ferns and flowering plants (dicotyledons and monocotyledons)

What are the features of viruses?

A protein coat and genetic material

List the structures compared between plant and animal cells.

Cell wall, cell membrane, nucleus, cytoplasm, chloroplasts, ribosomes, mitochondria, vacuoles

What structures make up a bacterial cell?

Cell wall, cell membrane, cytoplasm, ribosomes, circular DNA, plasmids

How are new cells produced?

By division of existing cells

What is the function of ciliated cells?

Movement of mucus in the trachea and bronchi

What is the function of root hair cells?

Absorption

What is the function of palisade mesophyll cells?

Photosynthesis

What is the function of neurones?

Conduction of electrical impulses

What is the function of red blood cells?

Transport of oxygen

What is the function of sperm and egg cells (gametes)?

Reproduction

Define cell, tissue, organ, organ system and organism.

Cell = basic unit of life; tissue = group of cells with similar structure/function; organ = group of tissues working together; organ system = group of organs working together; organism = an individual living thing

State the magnification formula.

Magnification = image size divided by actual size

What units are used to calculate magnification/size of biological specimens?

Millimetres (mm)

How do you convert between mm and micrometres?

1 mm = 1000 micrometres

Define diffusion.

The net movement of particles from a region of higher concentration to a region of lower concentration (down a concentration gradient), as a result of random movement

Where does the energy for diffusion come from?

The kinetic energy of random movement of molecules and ions

How do some substances move into/out of cells by diffusion?

By diffusion through the cell membrane

Why is diffusion of gases and solutes important in living organisms?

It allows exchange of essential substances (e.g. oxygen, carbon dioxide, nutrients) between cells/organisms and their environment

What factors influence the rate of diffusion?

Surface area, temperature, concentration gradient, distance

What role does water play as a solvent in organisms?

Important in digestion, excretion and transport

How does water diffuse through partially permeable membranes?

By osmosis

How does water move into/out of cells?

By osmosis through the cell membrane

What material can be used to investigate osmosis?

Dialysis (Visking) tubing

How are plants supported by water?

By the pressure of water inside the cells pressing outwards on the cell wall

Define osmosis (precise definition).

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

Define turgid.

A cell swollen and firm due to water uptake

Define turgor pressure.

Pressure exerted by cell contents against the cell wall

Define plasmolysis.

The cell membrane pulls away from the cell wall as the cell loses water

Define flaccid.

A cell that has lost water and is not firm/turgid

Why are water potential and osmosis important?

For the uptake and loss of water by organisms

Define active transport.

The movement of particles through a cell membrane from a region of lower concentration to a region of higher concentration (against a concentration gradient), using energy from respiration

Why is active transport important?

As a process for movement of molecules or ions across membranes, including ion uptake by root hairs

What moves molecules/ions across a membrane during active transport?

Protein carriers

What chemical elements make up carbohydrates, fats and proteins?

Carbohydrates and fats: carbon, hydrogen, oxygen. Proteins: carbon, hydrogen, oxygen, nitrogen (sometimes sulfur)

What are starch, glycogen and cellulose made from?

Glucose

What are proteins made from?

Amino acids

What are fats and oils made from?

Fatty acids and glycerol

What test is used for starch and what is the positive result?

Iodine solution test - turns from browny-orange to blue-black

What test is used for reducing sugars and what is the positive result?

Benedict's solution test - heated, turns from blue to brick-red/orange precipitate

What test is used for proteins and what is the positive result?

Biuret test - turns from blue to purple/lilac

What test is used for fats and oils and what is the positive result?

Ethanol emulsion test - forms a white emulsion

What test is used for vitamin C and what is the positive result?

DCPIP test - blue DCPIP is decolourised

Describe the structure of a DNA molecule.

Two strands coiled together to form a double helix; each strand contains chemicals called bases; bonds between pairs of bases hold the strands together; bases always pair the same way: A with T, C with G

What is a catalyst?

A substance that increases the rate of a chemical reaction and is not changed by the reaction

What are enzymes?

Proteins involved in all metabolic reactions, where they function as biological catalysts

Why are enzymes important in living organisms?

They provide the reaction rate necessary to sustain life

Describe enzyme action.

The shape of the active site of an enzyme is complementary to its substrate, allowing formation of products

What happens to enzyme activity with changing temperature and pH?

Activity increases to an optimum then decreases; extremes cause denaturation

Explain enzyme action using key terms.

Active site = region where substrate binds; enzyme-substrate complex forms; substrate = reactant; product = result of reaction

Explain enzyme specificity.

Due to the complementary shape and fit of the active site with the substrate

Explain the effect of temperature on enzyme activity.

Higher temperature increases kinetic energy, increasing frequency of effective collisions up to optimum; beyond optimum the enzyme's shape/active site is altered (denaturation) and activity drops rapidly

Explain the effect of pH on enzyme activity.

Changes in pH alter the shape and fit of the active site; extremes of pH denature the enzyme, reducing/stopping activity

Define photosynthesis.

The process by which plants synthesise carbohydrates from raw materials using energy from light

State the word equation for photosynthesis.

Carbon dioxide + water yields glucose + oxygen (in presence of light and chlorophyll)

What is chlorophyll and where is it found?

A green pigment found in chloroplasts

What does chlorophyll do?

Transfers energy from light into energy in chemicals, for synthesis of carbohydrates

What happens to starch, cellulose, glucose, sucrose and nectar made in photosynthesis?

Starch = energy store; cellulose = builds cell walls; glucose = used in respiration; sucrose = transported in phloem; nectar = attracts insects for pollination

Why are nitrate ions and magnesium ions important for plants?

Nitrate ions for making amino acids; magnesium ions for making chlorophyll

What factors affect the rate of photosynthesis?

Light intensity, carbon dioxide concentration, temperature

How is gas exchange in an aquatic plant investigated?

Using hydrogencarbonate indicator solution under light/dark conditions

State the balanced chemical equation for photosynthesis.

6CO2 + 6H2O yields C6H12O6 + 6O2

What are limiting factors of photosynthesis?

Light, carbon dioxide, and temperature can each limit the rate of photosynthesis in different environmental conditions

Why do most leaves have a large surface area and are thin?

Adaptations to maximise light absorption and gas diffusion for photosynthesis

List the structures in a dicotyledonous leaf.

Chloroplasts, cuticle, guard cells and stomata, upper and lower epidermis, palisade mesophyll, spongy mesophyll, air spaces, vascular bundles, xylem, phloem

How do leaf structures adapt leaves for photosynthesis?

Palisade cells packed with chloroplasts near upper surface for light absorption; spongy mesophyll air spaces allow gas diffusion; stomata allow gas exchange; thin leaf shortens diffusion distance; cuticle reduces water loss

What is a balanced diet?

A diet that contains all the nutrients needed in the correct proportions for health

What is the importance of carbohydrates in the diet?

Provide energy

What is the importance of fats and oils in the diet?

Provide energy (and insulation/cell membranes)

What is the importance of proteins in the diet?

Growth and repair

What is the importance of vitamin C in the diet?

Healthy skin and gums; prevents scurvy

What is the importance of vitamin D in the diet?

Calcium absorption/healthy bones; prevents rickets

What is the importance of calcium in the diet?

Healthy bones and teeth

What is the importance of iron in the diet?

Haemoglobin production

What is the importance of fibre (roughage) in the diet?

Aids gut movement, prevents constipation

What is the importance of water in the diet?

Solvent, transport, temperature regulation

What causes scurvy and rickets?

Scurvy = lack of vitamin C; rickets = lack of vitamin D

Name the organs of the alimentary canal.

Mouth, oesophagus, stomach, small intestine (duodenum and ileum), large intestine (colon, rectum, anus)

Name the associated organs of digestion.

Salivary glands, pancreas, liver, gall bladder

Define ingestion.

Taking substances (food/drink) into the body

Define digestion.

Breakdown of food

Define absorption (digestive system).

Movement of nutrients from the intestines into the blood