GCSE Combined Science Biology 2

Question 1

In genetics, what does the term 'heterozygous' mean?

Accepted Answer

Having two different alleles for a gene

Answer

Heterozygous means having two different alleles for a particular gene — one inherited from each parent (e.g., Bb). If both alleles are the same (e.g., BB or bb), the organism is homozygous.

Question 2

Which ecological term describes a community of organisms and their physical environment interacting together?

Accepted Answer

Ecosystem

Answer

An ecosystem includes all the living organisms (biotic factors) and non-living components (abiotic factors) in an area, and the interactions between them. Examples include a pond, a woodland, or a coral reef.

Question 3

During exercise, which substance builds up in muscles when there is insufficient oxygen for aerobic respiration?

Accepted Answer

Lactic acid

Answer

When muscles cannot get enough oxygen during intense exercise, they switch to anaerobic respiration, which produces lactic acid. This causes muscle fatigue and cramps. The oxygen debt must be repaid after exercise to break down the lactic acid.

Question 4

What is the function of the stomata in a leaf?

Accepted Answer

To allow gas exchange and control water loss

Answer

Stomata are tiny pores on the leaf surface (mainly underside) that allow carbon dioxide in for photosynthesis and oxygen out. Guard cells open and close the stomata to regulate gas exchange and reduce water loss through transpiration.

Question 5

Which type of pathogen causes diseases such as measles and influenza?

Accepted Answer

Viruses

Answer

Viruses cause measles and influenza. Viruses are not living cells — they are small particles containing genetic material (DNA or RNA) inside a protein coat. They can only reproduce inside living host cells, damaging them in the process.

GCSE Revision Practice Test

GCSE Revision Practice Test

GCSE Combined Science Biology 2