1st Year Biology — MCQs & Practice Questions

Any four of: movement, respiration, sensitivity, growth, reproduction, excretion, nutrition.

Independent variable: the factor deliberately changed. Dependent variable: the factor measured in response. Controlled variable: a factor kept constant so it does not affect the result.

1. Hypothesis: dough rises faster at higher temperatures (up to an optimum)[1]
2. Independent variable: temperature[1]
3. Dependent variable: rise in height (or volume) in a fixed time[1]
4. Keep controlled variables constant: same dough recipe, mass, container, time[1]
5. Measure the rise for each temperature[1]
6. Repeat each temperature several times and average for reliability[1]

Hypothesis that warmth speeds rising; IV = temperature, DV = rise; keep recipe/mass/time constant and repeat for reliability.

Actual size = image size ÷ magnification = 40 ÷ 2000 = 0.02 mm.

Advantage: it magnifies far more and shows much finer detail (higher resolution). Limitation: it cannot be used on living specimens, which must be dead and specially prepared.

1. Independent variable: the concentration of caffeine[1]
2. dependent variable: the heart rate of the water flea[1]
3. Control the temperature[1]
4. and the size/age of the water fleas (or same species)[1]
5. Repeating gives an average and reduces the effect of random error, improving reliability[1]

IV = caffeine concentration, DV = heart rate; control temperature and flea size; repeat for a reliable average.

Starch: add iodine solution — a blue-black colour is positive. Reducing sugar: warm with Benedict's solution — a change from blue to a brick-red precipitate is positive.

A protein's function depends on its specific 3-D shape (e.g. an enzyme's active site). Strong heating denatures it — changes its shape — so it can no longer carry out its function.

1. Carbohydrate monomer: a monosaccharide (e.g. glucose)[1]
2. Protein monomer: an amino acid[1]
3. Condensation joins monomers and releases water[1]
4. hydrolysis splits polymers by adding water[1]
5. Lipids store energy / insulate the body[1]
6. cushion organs / form cell membranes (any two)[1]

Carbohydrate monomer = monosaccharide, protein monomer = amino acid; condensation joins (releases water), hydrolysis splits (adds water); lipids store energy, insulate, cushion and build membranes.

It is a good solvent, so reactions occur in solution and substances are transported dissolved in it; and it has a high heat capacity, so it resists temperature change and helps keep organisms at a steady temperature.

Lipids contain about twice as much energy per gram as carbohydrates, so they store a lot of energy compactly for the long term (and also insulate). Carbohydrates like glucose are soluble and quickly broken down, making them ideal for immediate, short-term energy.

1. Reducing sugar: warm with Benedict's solution[1]
2. a positive result is blue changing to a brick-red precipitate[1]
3. Protein: add biuret solution[1]
4. a positive result is blue changing to purple[1]
5. Iodine blue-black shows starch is present[1]
6. starch is an insoluble energy store, so it does not affect the cell's water balance[1]

Benedict's (blue→brick-red) for reducing sugar; biuret (blue→purple) for protein; iodine blue-black shows starch, a compact insoluble store.

An enzyme has a specifically shaped active site. Only a substrate whose shape is complementary to the active site can fit and bind, forming an enzyme–substrate complex. Because only one substrate fits, the enzyme catalyses only that one reaction.

High temperature breaks the bonds that hold the enzyme's 3-D shape, denaturing it. The active site changes shape so the substrate can no longer bind, and the reaction almost stops.

1. As pH rises toward the optimum, the rate increases[1]
2. conditions increasingly suit the enzyme's active site[1]
3. Beyond the optimum the rate falls[1]
4. the enzyme is denatured — the active site changes shape and substrate no longer binds[1]
5. Temperature[1]
6. substrate (or enzyme) concentration[1]

Rate rises to an optimum pH then falls as the enzyme denatures; other factors: temperature and substrate/enzyme concentration.

Amylase digests starch (carbohydrate) to sugars; protease digests protein to amino acids; lipase digests fats to fatty acids and glycerol.

Cooling gives particles less kinetic energy, so there are fewer, less energetic collisions between enzyme and substrate — the reaction slows. But it does not break the bonds holding the enzyme's shape, so the active site is unchanged and the enzyme works normally again when warmed.

1. As temperature rises to the optimum, the rate (gas produced) increases[1]
2. molecules have more kinetic energy and collide more often[1]
3. so more enzyme–substrate complexes form[1]
4. Above the optimum the rate falls sharply[1]
5. the heat breaks the bonds holding the enzyme's shape (denaturing)[1]
6. the active site changes shape so the substrate no longer fits and the reaction stops[1]

Rate rises to an optimum (more successful collisions), then falls as the enzyme denatures and its active site is destroyed.

Cell wall — support and shape (cellulose); chloroplasts — photosynthesis; large permanent vacuole — stores cell sap and keeps the cell turgid.

Diffusion is the passive net movement of particles from high to low concentration (no energy needed). Active transport moves particles against the gradient, from low to high concentration, and needs energy from respiration.

1. Osmosis is the movement of water[1]
2. across a partially permeable membrane from a dilute to a more concentrated solution[1]
3. In pure water the cube gains mass[1]
4. because water enters the cells by osmosis (cells more concentrated than pure water)[1]
5. In concentrated sugar solution the cube loses mass[1]
6. because water leaves the cells by osmosis toward the more concentrated solution[1]

Osmosis = water moving across a partially permeable membrane to the more concentrated side; cube gains mass in water, loses mass in concentrated sugar.

Diffusion only moves substances down a concentration gradient (high to low) and needs no energy. Active transport uses energy from respiration to move substances against the gradient, from low to high concentration.

A cell wall and chloroplasts (also a large permanent vacuole). The cell wall (cellulose) supports and shapes the cell; chloroplasts carry out photosynthesis; the vacuole stores cell sap and keeps the cell turgid.

1. Osmosis[1]
2. In pure water the solution is more dilute than the cell contents[1]
3. so water enters the cells by osmosis and the mass increases[1]
4. In a concentrated solution the outside is more concentrated than the cells[1]
5. so water leaves the cells by osmosis and the mass decreases[1]

Osmosis; gains mass in water (water enters), loses mass in concentrated solution (water leaves).

Two Latin words: the genus first (capital letter) and the species second (lower case); the whole name is italicised (or underlined), e.g. Homo sapiens.

Any three, e.g. Prokaryotae — no nucleus; Plantae — photosynthesise; Animalia — multicellular, feed on other organisms; Fungi — absorb nutrients, chitin walls.

1. A group of similar organisms[1]
2. that can breed together to produce fertile offspring[1]
3. Kingdom, phylum, class, order,[1]
4. family, genus, species[1]
5. Each species has one unique, universal name[1]
6. understood worldwide, avoiding the ambiguity of common names[1]

Species = organisms that interbreed to give fertile offspring; hierarchy kingdom→…→species; binomial names are unique and universal.

A dichotomous key is a set of paired statements or questions, each offering two choices about an observable feature. At each step you pick the option that matches the organism, which directs you to the next pair, until you reach the organism's name.

For example a cactus: a thick waxy cuticle to reduce water loss, and spines (reduced leaves) that lower water loss and deter herbivores. (Any organism with two valid habitat adaptations is acceptable.)

1. To identify organisms and organise the diversity of life[1]
2. and to study their relationships / shared ancestry[1]
3. A binomial name is unique to one species[1]
4. and is understood worldwide, avoiding the ambiguity of common names[1]
5. Species[1]

Classify to identify/organise and show relationships; binomial names are unique and universal; the smallest group is the species.

Any three: no nucleus (DNA is a free circular loop); no membrane-bound organelles; a cell wall; sometimes plasmids or a flagellum; reproduces by binary fission.

1. A virus is genetic material (DNA or RNA)[1]
2. surrounded by a protein coat[1]
3. It cannot respire, grow or reproduce by itself[1]
4. it only replicates inside a host cell[1]
5. Antibiotics target bacterial structures/processes (e.g. cell walls)[1]
6. viruses have no such structures and hide inside host cells, so antibiotics do not affect them[1]

A virus is nucleic acid in a protein coat; non-living because it needs a host to replicate; antibiotics hit bacterial structures viruses lack.

Antibiotics target structures and processes found in bacteria (such as the cell wall), killing them or stopping them dividing. Viruses have no such structures and replicate inside the body's own cells, so antibiotics cannot affect them.

1. The bacterium invades and multiplies rapidly in the body[1]
2. and releases toxins that damage tissues, causing symptoms[1]
3. Decomposers break down dead matter, recycling nutrients[1]
4. nitrogen-fixing bacteria convert nitrogen gas into compounds plants can use[1]
5. and bacteria are used to make foods (yoghurt/cheese) or medicines (insulin/antibiotics)[1]

Pathogens multiply and release toxins that damage tissue; useful bacteria decompose, fix nitrogen and make food/medicine.

Eukaryotic with chitin cell walls; made of hyphae forming a mycelium; feed saprotrophically (external digestion then absorption); reproduce by spores; cannot photosynthesise (any three).

1. Mosses (bryophytes) are non-vascular / need damp places[1]
2. and reproduce by spores[1]
3. Ferns have vascular tissue (xylem and phloem)[1]
4. and reproduce by spores[1]
5. Flowering plants reproduce by seeds enclosed in fruits and have flowers[1]
6. with efficient vascular tissue, making them highly adaptable to land[1]

Mosses: non-vascular, spores; ferns: vascular, spores; flowering plants succeed via seeds in fruits, flowers and vascular tissue.

Harmful: a pathogenic fungus such as the cause of athlete's foot or a crop rust. Useful: yeast (for bread and alcohol) or Penicillium (for the antibiotic penicillin).

1. Mosses have no vascular tissue and no true roots[1]
2. and need water for reproduction (so they must stay damp)[1]
3. A waterproof waxy cuticle reduces water loss[1]
4. vascular tissue (xylem and phloem) transports water and supports tall growth[1]
5. seeds and pollen allow reproduction without water[1]

Mosses lack vascular tissue and need water to reproduce; cuticle, vascular tissue and seeds/pollen adapted later plants to drier land.

A hard exoskeleton and jointed legs (also a segmented body).

1. Fish: gills / scales / eggs in water[1]
2. Birds: feathers / wings / hard-shelled eggs[1]
3. Mammals: hair / feed young on milk / live young[1]
4. Reptiles have dry, scaly, waterproof skin (reduces water loss)[1]
5. amphibians have moist skin and must stay damp[1]
6. reptiles lay leathery eggs on land, so they need no water to breed (amphibians lay eggs in water)[1]

Fish (gills), birds (feathers), mammals (milk); reptiles beat amphibians on land via waterproof skin and land-laid eggs.

Advantage: the animal keeps a steady body temperature and stays active even in the cold, so it can live in many habitats. Disadvantage: it must eat much more food to generate that heat.

1. A hard exoskeleton[1]
2. and jointed legs[1]
3. The exoskeleton protects and reduces water loss (success on land)[1]
4. jointed legs allow fast, precise movement[1]
5. small size and metamorphosis let many live in small niches without competing[1]

Exoskeleton + jointed legs; success from waterproof protection, agile movement, small size and metamorphosis reducing competition.

Glucose + oxygen → carbon dioxide + water (+ energy). Most aerobic respiration occurs in the mitochondria.

Aerobic uses oxygen, releases a lot of energy, and gives carbon dioxide and water. Anaerobic uses no oxygen, releases little energy, and gives lactic acid.

1. Light intensity[1]
2. carbon dioxide concentration[1]
3. temperature[1]
4. Increasing light increases the rate[1]
5. while light is the limiting factor[1]
6. it levels off when another factor (CO₂ or temperature) becomes limiting[1]

Limiting factors: light, CO₂, temperature; rate rises with light then plateaus when another factor limits it.

Boil the leaf to kill it, then decolourise it in hot ethanol (away from a flame) and rinse it. Add iodine solution: a blue-black colour shows starch has been made, indicating photosynthesis.

Being thin gives a short diffusion distance so gases and light reach the inner cells quickly; the many stomata allow carbon dioxide to diffuse in (and oxygen out) fast enough for photosynthesis.

1. Carbon dioxide + water → glucose + oxygen (light energy, chlorophyll)[1]
2. Light intensity[1]
3. carbon dioxide concentration[1]
4. temperature[1]
5. As light increases the rate rises (light is limiting)[1]
6. then levels off when another factor becomes limiting[1]

CO₂ + water → glucose + oxygen; limiting factors light/CO₂/temperature; rate rises with light then plateaus when another factor limits it.

Amylase digests starch (carbohydrate) into sugars; protease digests protein into amino acids; lipase digests fats into fatty acids and glycerol.

Autotrophic nutrition makes food from simple inorganic molecules (e.g. plants by photosynthesis). Heterotrophic nutrition takes in ready-made organic food from other organisms (as in animals and fungi).

1. Large food molecules are insoluble[1]
2. so they must be broken into small soluble molecules that can be absorbed into the blood[1]
3. The lining is folded into villi, giving a large surface area[1]
4. the villi have walls one cell thick for a short diffusion distance[1]
5. each villus has a rich blood supply (capillaries)[1]
6. which carries absorbed food away, keeping a steep concentration gradient[1]

Digestion makes molecules small and soluble enough to absorb; villi give large area, thin walls and a rich blood supply for fast absorption.

Scurvy — lack of vitamin C; rickets — lack of vitamin D (or calcium); anaemia — lack of iron; kwashiorkor — lack of protein. (Any three.)

1. Absorption is the passage of digested food from the gut into the blood[1]
2. assimilation is the cells taking up and using those molecules[1]
3. The liver stores excess glucose as glycogen[1]
4. breaks down excess amino acids, making urea[1]
5. and breaks down toxins (or builds some proteins)[1]

Absorption = food into blood; assimilation = cells using it; the liver stores glycogen, makes urea from excess amino acids, and detoxifies.

There are millions of alveoli giving a large surface area; their walls are one cell thick for a short diffusion distance; they have a moist lining so gases dissolve; and they are surrounded by many capillaries that keep the concentration gradient steep.

Breathing is the physical movement of air in and out of the lungs (ventilation). Respiration is the chemical process in cells that releases energy from glucose. Breathing supplies the oxygen respiration needs.

1. Trachea → bronchi → bronchioles[1]
2. → alveoli[1]
3. The diaphragm and intercostal muscles contract[1]
4. the diaphragm flattens and the ribcage moves up and out[1]
5. so the volume of the chest increases and the pressure inside falls[1]
6. air moves in from the higher outside pressure to the lower pressure in the lungs[1]

Trachea → bronchi → bronchioles → alveoli; muscles contract, chest volume rises, internal pressure falls, so air flows in.

During hard exercise the muscles respire anaerobically and build up lactic acid. Extra oxygen (the oxygen debt) is needed afterwards to break down this lactic acid, so deep breathing continues until it is cleared.

Tar contains carcinogens that cause lung cancer; tar paralyses the cilia so mucus and dirt build up, causing infection; and the alveoli walls break down (emphysema), reducing the surface area for gas exchange. (Carbon monoxide also reduces oxygen transport.)

1. A large surface area (millions of alveoli)[1]
2. walls one cell thick for a short diffusion distance[1]
3. a moist lining and a rich capillary blood supply (steep gradient)[1]
4. Carbon monoxide binds to haemoglobin in red blood cells[1]
5. taking the place of oxygen, so the blood carries less oxygen[1]

Alveoli: large area, thin walls, moist lining, rich blood supply; CO binds haemoglobin, cutting oxygen transport.

Red blood cells carry oxygen (using haemoglobin); white blood cells defend the body against disease; platelets help the blood to clot.

1. Arteries have thick muscular elastic walls[1]
2. to carry high-pressure blood away from the heart without bursting[1]
3. Veins have thinner walls and valves[1]
4. to return low-pressure blood to the heart and prevent backflow[1]
5. In double circulation blood is returned to the heart after the lungs[1]
6. so it can be pumped to the body at high pressure, giving faster delivery of oxygen[1]

Arteries: thick muscular walls for high pressure; veins: thin walls with valves for low-pressure return; double circulation keeps body-delivery pressure high.

During exercise the muscles respire faster and need more oxygen and glucose while producing more carbon dioxide. A faster heart rate pumps blood around more quickly, delivering oxygen and removing wastes at the higher rate needed.

1. Capillary walls are only one cell thick[1]
2. giving a very short diffusion distance[1]
3. and they form a dense network reaching close to every cell[1]
4. An artery has thick, muscular, elastic walls[1]
5. to withstand the high pressure of blood pumped from the heart[1]
6. and the elastic recoil helps keep the blood moving[1]

Capillaries: thin walls, short diffusion distance, close to every cell; arteries: thick elastic muscular walls for high-pressure blood.

Xylem carries water and minerals upward in dead tubes; phloem carries dissolved food (sucrose) in living cells, in both directions.

Higher temperature and wind speed evaporation, and dry air gives a steeper water-vapour gradient out of the leaf, so more water is lost. On a cool, still, humid day all these are reduced.

1. Transpiration is the loss of water vapour from a plant[1]
2. mostly through the stomata[1]
3. Wind increases the rate[1]
4. it removes water vapour, keeping a steep gradient so evaporation continues[1]
5. Nitrate (or magnesium)[1]
6. for proteins (or chlorophyll)[1]

Transpiration = water-vapour loss via stomata; wind speeds it; nitrate is needed for proteins (magnesium for chlorophyll).

The cells lose water and become flaccid, so they lose their turgor pressure. Without turgor to support them, the stems and leaves droop — the plant wilts.

The moving air blows away water vapour from around the leaves, keeping a steep water-vapour gradient, so transpiration (and therefore water uptake) speeds up.

1. Water enters root hair cells by osmosis[1]
2. it travels up the xylem[1]
3. in the transpiration stream, pulled up as water evaporates from the leaves[1]
4. Higher temperature (or lower humidity)[1]
5. more wind (or brighter light)[1]

Water enters roots by osmosis, rises in the xylem (transpiration stream); faster in warm, dry, windy or bright conditions.