GCSE Biology Practice Questions

Question 1

Cell Biology Easy

Name the organelle where aerobic respiration occurs.

Solution:

Aerobic respiration is the process that releases energy from glucose using oxygen
This process occurs in a specific organelle
The organelle contains enzymes for respiration
It has a double membrane and cristae (folds)

Answer: Mitochondria (singular: mitochondrion)

Question 2

Photosynthesis Medium

Write the word equation for photosynthesis.

Solution:

Photosynthesis occurs in chloroplasts
It requires light energy (from the sun)
Reactants: carbon dioxide and water
Products: glucose and oxygen
Energy from light is trapped by chlorophyll

Answer: Carbon dioxide + Water → Glucose + Oxygen
(in the presence of light)

Question 3

Genetics Easy

How many chromosomes are in a normal human body cell?

Solution:

Human body cells are diploid (contain pairs of chromosomes)
Chromosomes come in pairs - one from each parent
There are 23 pairs of chromosomes
Total = 23 × 2 = 46 chromosomes
Note: Gametes (sex cells) have 23 chromosomes (haploid)

Answer: 46 chromosomes (23 pairs)

Question 4

Heart & Circulation Medium

Describe the path of blood through the heart, starting from the vena cava.

Solution:

Vena cava → Right atrium
Right atrium → Right ventricle (through tricuspid valve)
Right ventricle → Pulmonary artery (to lungs)
Lungs → Pulmonary vein
Pulmonary vein → Left atrium
Left atrium → Left ventricle (through bicuspid valve)
Left ventricle → Aorta (to body)

Answer: Vena cava → Right atrium → Right ventricle → Pulmonary artery → Lungs → Pulmonary vein → Left atrium → Left ventricle → Aorta

Question 5

Inheritance Hard

In pea plants, tall (T) is dominant over short (t).

Two heterozygous tall plants are crossed. What proportion of offspring will be short?

Solution:

Both parents are heterozygous: Tt × Tt

Punnett square:

        T    t
    T   TT   Tt
    t   Tt   tt

Offspring genotypes: TT, Tt, Tt, tt
Phenotypes: 3 tall : 1 short
Proportion short = 1/4 = 25%

Answer: 1/4 or 25%

Question 6

Ecology Medium

Explain why energy is lost between trophic levels in a food chain.

Solution:

Energy is lost through:
- Respiration: Energy released as heat
- Movement: Energy used for life processes
- Excretion: Not all material is absorbed
- Not all consumed: Some parts not eaten (bones, roots)
Only about 10% of energy passes to next level
This limits the length of food chains

Answer: Energy lost through respiration (heat), movement, excretion, and uneaten parts. Only ~10% passes to next trophic level

Question 7

Cell Division Medium

What is the difference between mitosis and meiosis?

Solution:

Mitosis:
- Produces 2 daughter cells
- Genetically identical to parent
- Diploid cells (46 chromosomes)
- Used for growth and repair
Meiosis:
- Produces 4 daughter cells
- Genetically different
- Haploid cells (23 chromosomes)
- Produces gametes (sex cells)

Answer: Mitosis produces 2 identical diploid cells for growth; Meiosis produces 4 different haploid gametes

Question 8

Homeostasis Hard

Describe how the body responds to a rise in body temperature.

Solution:

Detection: Thermoregulatory centre in brain detects rise
Response mechanisms:
- Vasodilation: Blood vessels near skin widen, more blood flows to surface, more heat lost by radiation
- Sweating: Sweat glands produce sweat, evaporation cools skin
- Reduced metabolic rate: Less heat produced
Result: Body temperature returns to normal (~37°C)

Answer: Vasodilation (blood vessels widen), sweating (evaporation cools), reduced metabolism - all lower temperature

Question 9

Infection & Response Medium

Explain how vaccination protects against disease.

Solution:

Vaccine contains dead/weakened pathogen
White blood cells detect antigens on pathogen
Lymphocytes produce specific antibodies
Memory cells remain in blood
If real pathogen enters, memory cells rapidly produce antibodies
Pathogen destroyed before symptoms develop
Person is immune

Answer: Vaccine contains dead/weakened pathogen, stimulates antibody production, memory cells remain, rapid response if infected = immunity

Question 10

Biodiversity Hard

Suggest two ways humans have reduced biodiversity.

Solution:

Deforestation:
- Destroys habitats
- Species lose food sources and shelter
- Reduces number of species
Pollution:
- Pesticides kill non-target species
- Toxic waste poisons ecosystems
- Reduces populations
Other examples: Climate change, hunting, monoculture farming

Answer: 1) Deforestation - destroys habitats, 2) Pollution - kills organisms with toxic waste/pesticides

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