Scottish National 5 (Nat 5) Biology Syllabus

What is ATP and why is it important in respiration?

ATP (adenosine triphosphate) is the energy-carrying molecule produced by respiration. It stores chemical energy that cells use for processes such as muscle contraction, cell division and protein synthesis.

Name the stages of mitosis in order and state its purpose.

The chromosomes are copied, then separated equally into two identical nuclei. Mitosis produces two genetically identical diploid daughter cells, maintaining the diploid chromosome number for growth and repair.

Why must chromosomes be copied before a cell divides by mitosis?

So that each new daughter cell receives a complete and identical set of chromosomes, keeping the diploid chromosome number constant.

What are stem cells and what are the two main types?

Stem cells are unspecialised cells that can divide and differentiate into specialised cell types. The two types are embryonic stem cells and adult (tissue) stem cells.

Put these in order of increasing size/complexity: organ, cell, organism, tissue, organ system.

Cell → tissue → organ → organ system → organism.

Define a tissue and give an example.

A tissue is a group of similar cells working together to carry out a particular function, e.g. muscle tissue or nervous tissue.

Name the three types of neurone in a reflex arc, in order.

Sensory neurone → inter (relay) neurone → motor neurone.

How is a nerve impulse passed from one neurone to the next across a synapse?

The electrical impulse triggers release of a chemical (neurotransmitter) that diffuses across the synaptic gap and binds to receptors on the next neurone, passing the signal on.

Describe the principle of negative feedback in controlling blood glucose.

A change away from the norm is detected and triggers a response that reverses the change, returning conditions to normal. E.g. high blood glucose triggers insulin release, lowering it back to normal.

Which hormones control blood glucose and what does each do?

Insulin lowers blood glucose (converts glucose to glycogen in the liver); glucagon raises blood glucose (converts glycogen back to glucose). Both are made by the pancreas.

What is the difference between a gamete and a zygote, and how many chromosomes does each have in humans?

A gamete (sperm/egg) is a sex cell with the haploid number (23 chromosomes). A zygote is the fertilised egg formed when two gametes fuse, with the diploid number (46 chromosomes).

Name the male and female gametes in animals and in flowering plants.

Animals: sperm (male) and egg/ovum (female). Flowering plants: pollen (male) and ovule/egg cell (female).

Define the terms genotype and phenotype.

Genotype is the genetic make-up of an organism (the alleles it carries, e.g. Bb). Phenotype is the observable physical characteristic that results (e.g. brown eyes).

What do the terms dominant, recessive, homozygous and heterozygous mean?

Dominant: allele expressed even with one copy. Recessive: only expressed when homozygous. Homozygous: two identical alleles (e.g. BB or bb). Heterozygous: two different alleles (e.g. Bb).

In a cross between two heterozygous parents (Bb × Bb), what is the expected phenotype ratio?

3 dominant : 1 recessive (genotype ratio 1 BB : 2 Bb : 1 bb).

Distinguish continuous from discrete variation.

Continuous variation shows a range of values with no distinct categories (e.g. height) and is controlled by many genes. Discrete variation falls into clear-cut categories (e.g. blood group) and is usually controlled by one or few genes.

State the function of the red blood cells, white blood cells, plasma and platelets.

Red blood cells carry oxygen (contain haemoglobin); white blood cells defend against pathogens; plasma transports dissolved substances; platelets help blood clot.

List the path of blood through the heart, naming the four chambers.

Body → right atrium → right ventricle → lungs → left atrium → left ventricle → body. (Right side pumps deoxygenated blood to lungs; left side pumps oxygenated blood to body.)

Compare arteries, veins and capillaries by structure and function.

Arteries carry blood away from the heart at high pressure (thick muscular walls). Veins return blood to the heart at low pressure (thinner walls, valves). Capillaries are one cell thick for exchange of materials with tissues.

What features make alveoli efficient for gas exchange?

Large surface area, thin (one-cell-thick) walls, moist lining, and a good blood supply, giving short diffusion distance and steep concentration gradients.

Name two harmful chemicals in tobacco smoke and a disease linked to smoking.

Nicotine (addictive, raises heart rate), carbon monoxide (reduces oxygen carriage) and tar (carcinogen). Linked diseases include lung cancer, emphysema and heart disease.

Define the ecological terms ecosystem, community and population.

Population: all organisms of one species in an area. Community: all the populations of different species in an area. Ecosystem: the community plus the non-living (abiotic) environment they interact with.

Distinguish between a biotic and an abiotic factor, giving one example of each.

Biotic factors are living influences (e.g. predation, competition, disease). Abiotic factors are non-living influences (e.g. temperature, light intensity, soil pH, moisture).

Name two sampling techniques used to measure the distribution of organisms.

A quadrat (to sample plants/slow-moving animals in an area) and a pitfall trap (to sample small ground invertebrates). Pooters and nets are also used.

Write the word equation for photosynthesis.

$$\text{carbon dioxide} + \text{water} \xrightarrow{\text{light energy}} \text{glucose} + \text{oxygen}$$

Write the balanced chemical equation for photosynthesis.

$$\ce{6CO2 + 6H2O ->[light] C6H12O6 + 6O2}$$

Name three uses of the glucose made in photosynthesis by a plant.

Used in respiration for energy, converted to starch for storage, and used to make cellulose for cell walls (also used to build proteins with nitrates).

Why does a food chain rarely have more than four or five trophic levels?

Only about 10% of energy is passed to the next trophic level; the rest is lost as heat, movement and undigested waste, so there is too little energy left to support further levels.

Define biodiversity and give one reason it is important.

Biodiversity is the variety of all the different species of organisms in an ecosystem. High biodiversity makes ecosystems more stable and able to recover from change, and provides resources and services for humans.

State the four key ideas of natural selection (Darwin's theory).

1) Variation exists within a species; 2) more offspring are produced than can survive, so there is competition; 3) better-adapted individuals survive and reproduce (survival of the fittest); 4) they pass on the favourable alleles, so the population changes over generations.

Give two examples of human activities that increase carbon dioxide in the atmosphere and one consequence.

Burning fossil fuels and deforestation increase atmospheric CO2. A consequence is the enhanced greenhouse effect leading to global warming/climate change. (Other human impacts: pollution from fertilisers, habitat destruction reducing biodiversity.)