Scottish National 4 (Nat 4) Biology (National 4) Syllabus

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.

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

What three things does a plant need for photosynthesis?

Carbon dioxide, water, and light energy (absorbed by chlorophyll).

Write the word equation for aerobic respiration.

$$\text{glucose} + \text{oxygen} \rightarrow \text{carbon dioxide} + \text{water} \; (+\,\text{energy})$$

Write the balanced chemical equation for aerobic respiration.

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

State one key difference between photosynthesis and respiration in terms of energy.

Photosynthesis stores light energy as chemical energy in glucose; respiration releases energy from glucose for the cell to use.

List the levels of organisation in a multicellular organism, from smallest to largest.

Cells → tissues → organs → organ systems → organism.

Define a tissue.

A group of similar cells that work together to perform a particular function (e.g. muscle tissue).

Define an organ.

A group of different tissues working together to carry out a specific function (e.g. the heart).

What are the male and female gametes (sex cells) in animals?

The male gamete is the sperm; the female gamete is the egg (ovum).

What is fertilisation?

The fusion (joining) of the nucleus of a male gamete with the nucleus of a female gamete to form a zygote.

What are the male and female gametes in a flowering plant, and where are they found?

Male gamete: pollen (made in the anther). Female gamete: ovule/egg (found in the ovary).

Name the main organs of the human digestive system in order.

Mouth → oesophagus → stomach → small intestine → large intestine.

What is the role of the lungs in the respiratory system?

Gas exchange — oxygen diffuses into the blood and carbon dioxide diffuses out, at the alveoli.

Name the three main blood vessels and one feature of each.

Arteries (carry blood away from the heart, thick walls, high pressure); veins (carry blood to the heart, have valves); capillaries (thin walls for exchange of materials).

What is the nervous system's role in control and communication?

It detects stimuli and sends rapid electrical messages (impulses) along neurons to coordinate fast responses.

Describe the reflex arc pathway.

Stimulus → receptor → sensory neuron → relay neuron (in CNS) → motor neuron → effector → response.

What are the two parts of the central nervous system (CNS)?

The brain and the spinal cord.

How does hormonal (endocrine) control differ from nervous control?

Hormones are chemical messengers carried in the blood — slower but longer-lasting; nervous control uses electrical impulses — fast and short-lived.

What hormone controls blood sugar level, and which organ releases it?

Insulin, released by the pancreas, lowers blood sugar level.

Define an ecosystem.

All the living organisms (community) in a particular area together with the non-living (abiotic) factors of their environment, interacting together.

Define biodiversity.

The variety of different species of living organisms in an ecosystem (or on Earth).

What is a food chain and what does the direction of the arrows represent?

A diagram showing the feeding relationships between organisms; the arrows show the direction of energy flow (from prey to predator).

Define a producer and a consumer.

A producer (e.g. green plant) makes its own food by photosynthesis; a consumer is an organism that gets energy by eating other organisms.

What is an adaptation?

A feature or characteristic of an organism that makes it better suited (adapted) to survive in its environment.

Explain the basic process of natural selection.

Variation exists in a population; those with adaptations best suited to the environment are more likely to survive, reproduce and pass on their favourable characteristics to offspring ('survival of the fittest').

Give two examples of human activities that negatively impact the environment.

Burning fossil fuels (air pollution / increased CO2), deforestation, overuse of fertilisers, and dumping of waste/chemicals — any two.

What is an indicator species and what does it indicate?

A species whose presence or absence indicates the level of pollution (environmental quality) in an area, e.g. lichens indicate clean air.

In designing an investigation, what is the difference between the independent and dependent variable?

The independent variable is the one you deliberately change; the dependent variable is the one you measure as a result.

Why is it important to repeat an experiment and identify variables to keep constant?

Repeating and averaging results makes the data more reliable, and keeping all other variables constant makes the experiment a fair test so the results are valid.