AQA GCSE Biology Biology Paper 2 (Foundation), November 2021: Question 5

✅ Correct Answer

Phytophthora

💡 Key Knowledge

Organisms have a two-part Latin name (the binomial system):

• First name (capitalised) = Genus (e.g., Phytophthora).
• Second name (lower case) = Species (e.g., infestans).

❌ Common Errors

Choosing both words together (Phytophthora infestans) or picking the second word (infestans), which is only the species descriptor.

🧠 Exam Technique

Remember Genus comes first in alphabetical order compared to species. The genus always has a capital letter.

✅ Correct Answer

The fungus can get oxygen from the air.

💡 Key Knowledge

Aerobic respiration requires glucose and oxygen:

glucose + oxygen → carbon dioxide + water (+ energy)

The surface has access to air, providing the necessary oxygen gas.

❌ Common Errors

Selecting "water from the potato" or "nitrogen from the soil". While organisms need water and nitrogen, neither is a reactant in respiration.

🧠 Exam Technique

Read the question stem carefully: it specifically asks how it helps the fungus to respire, not just grow.

✅ Correct Answer

The variety of species of organisms in the river.

💡 Key Knowledge

Biodiversity is the variety of all different species of organisms on Earth, or within an ecosystem. It includes animals, plants, fungi, protists, and bacteria.

❌ Common Errors

Choosing "animals only" or "plants only". Biodiversity encompasses all organisms living together.

🧠 Exam Technique

Look for broad, comprehensive ecological terms. "Organisms" covers both plants and animals.

✅ Correct Answer

Any two linked points:

1. Pesticide was washed into the river (surface run-off / carried by rain). [1 mark]
2. Pesticide kills organisms / plants / animals in the river. [1 mark]

🧠 Exam Technique

This is a 2-mark "Explain" question: you must give a cause and an effect:

• Cause: How did it get into the river? (rain washed/ran off).
• Effect: What happened to the river life? (pesticide is toxic and killed organisms).

❌ Common Errors

Simply stating "it polluted the river" without explaining that the chemical was washed in, or stating "it harmed the river" without noting that organisms were killed.

💡 Key Knowledge

Pesticides are toxic agrochemicals designed to kill pests. Rainwater can cause agricultural run-off into freshwater streams, lowering biodiversity by killing non-target aquatic organisms.

✅ Correct Answer

Filled in boxes: Rr , Rr , and rr .

🧠 Exam Technique

Standard genetic convention writes dominant uppercase letters first: write Rr rather than rR (though both are scientifically acceptable, Rr avoids confusion).

✅ Correct Answer

Draw a ring around either RR OR rr .

(Mark scheme also allows ringing both RR and rr ).

💡 Key Knowledge

• Homozygous: Having two identical alleles for a gene ( RR = homozygous dominant, rr = homozygous recessive).
• Heterozygous: Having two different alleles for a gene ( Rr ).

❌ Common Errors

Ringing Rr . The prefix hetero- means different, while homo- means same.

📐 Step-by-Step Calculation

1. Resistance is dominant ( R ). Any plant with at least one R is resistant.
2. Identify matching genotypes from the 4 offspring:
   • RR (Resistant)
   • Rr (Resistant)
   • Rr (Resistant)
   • rr (Not resistant)
3. Resistant count = 3 out of 4.
4. Percentage = (3 ÷ 4) × 100% = 75%

✅ Correct Answer

Tick: 75%

❌ Common Errors

Selecting 25% (confusing the proportion of non-resistant plants rr or homozygous dominant RR with total resistant plants).

✅ Correct Answer

• Mark 1: There is no fusion of gametes / no fertilisation
  OR asexual reproduction involves mitosis.
• Mark 2: (So) the offspring are genetically identical / clones (they have the exact same DNA / inherit allele R ).

💡 Key Knowledge

Asexual reproduction uses mitosis to produce genetically identical copies (clones). Because only one parent is involved and gametes do not fuse, there is no mixing of genetic material.

🧠 Exam Technique

When an exam question mentions asexual reproduction, the mark scheme almost always rewards two key phrases:

• "No fusion of gametes / no fertilisation"
• "Genetically identical / clones"

❌ Common Errors

Vague statements like "the plant just grows from it" or confusing mitosis with meiosis. Meiosis produces non-identical gametes in sexual reproduction!