GCSE Biology 5 — Questions and Answers
Question 1: What evidence from the fossil record supports the theory of evolution by natural selection?
- Fossils show that all species have remained unchanged over millions of years
- Fossils reveal a gradual change in organisms over time, showing transitional forms (Correct answer)
- Fossils demonstrate that species were each created separately at different times
- Fossils only preserve soft-bodied organisms, providing no useful evidence
Correct answer: Fossils reveal a gradual change in organisms over time, showing transitional forms
The fossil record shows gradual anatomical changes across geological time, including transitional fossils that link ancestral and descendant species.
Question 2: Which term describes a protein that speeds up a chemical reaction without being consumed in the process?
- Hormone
- Enzyme (Correct answer)
- Substrate
- Coenzyme
Correct answer: Enzyme
Enzymes are biological catalysts made of protein that lower activation energy and are regenerated after each reaction.
Question 3: How does the structure of a red blood cell relate to its function?
- It has a large nucleus to control haemoglobin production
- Its biconcave disc shape increases surface area for oxygen diffusion (Correct answer)
- Its thick cell wall protects haemoglobin from damage
- It contains chloroplasts to produce energy for oxygen transport
Correct answer: Its biconcave disc shape increases surface area for oxygen diffusion
The biconcave disc shape of red blood cells maximises surface area-to-volume ratio, allowing rapid diffusion of oxygen to and from haemoglobin.
Question 4: What is meant by the term 'limiting factor' in the context of photosynthesis?
- A factor that is always present in excess and has no effect on the rate
- A factor that is present in the lowest quantity relative to need, restricting the rate of photosynthesis (Correct answer)
- A toxin that prevents the plant from photosynthesising at all
- A factor that speeds up photosynthesis beyond its natural maximum
Correct answer: A factor that is present in the lowest quantity relative to need, restricting the rate of photosynthesis
A limiting factor is the variable present in the least adequate amount that constrains the overall rate of photosynthesis, such as light intensity, CO₂ concentration, or temperature.
Question 5: Which method of reproduction produces offspring that are genetically identical to the parent?
- Sexual reproduction
- Fertilisation
- Asexual reproduction (Correct answer)
- Cross-pollination
Correct answer: Asexual reproduction
Asexual reproduction involves only one parent and no fusion of gametes, producing genetically identical offspring called clones.
Question 6: What is the role of platelets in the blood?
- Transporting oxygen around the body
- Producing antibodies to fight infection
- Clotting the blood to prevent excessive blood loss (Correct answer)
- Carrying carbon dioxide back to the lungs
Correct answer: Clotting the blood to prevent excessive blood loss
Platelets are cell fragments that accumulate at wound sites, releasing chemicals that initiate the clotting cascade to form a fibrin mesh.
Question 7: Which adaptation helps a cactus survive in a hot desert environment?
- Broad flat leaves to maximise photosynthesis
- Shallow widespread roots to capture rainwater quickly
- Thick waxy skin and stomata that open only at night (Correct answer)
- Deciduous leaves that are shed during dry seasons
Correct answer: Thick waxy skin and stomata that open only at night
Cacti have a thick waxy cuticle to reduce water loss, and their stomata open at night (CAM photosynthesis) to minimise transpiration in daytime heat.
GCSE Biology 5
What evidence from the fossil record supports the theory of evolution by natural selection?