AQA GCSE Biology · 4.6

Inheritance, variation and evolution

50 exam-style questions with answers for 4.6 Inheritance, variation and evolution in AQA GCSE Biology (spec 8461). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below. Not official AQA material.

All 50 questions and answers

Question 1 · Spec 4.6.1.1 · Reproduction
State two differences between sexual and asexual reproduction. [2 marks]
Answer:
Any two from: sexual reproduction involves two parents, asexual one (1); sexual involves fusion of gametes, asexual does not (1); sexual produces variation, asexual produces genetically identical clones (1); asexual involves mitosis only (1).
Question 2 · Spec 4.6.1.1 · Gametes
Name the gametes in animals and in flowering plants. [2 marks]
Answer:
Animals: sperm and egg cells (1). Flowering plants: pollen and egg cells (1).
Question 3 · Spec 4.6.1.2 · Meiosis
Describe what happens in meiosis. [3 marks]
Answer:
Copies of the genetic information are made (1); the cell divides twice to form four gametes (1); each gamete has a single set of chromosomes and all are genetically different (1).
Question 4 · Spec 4.6.1.2 · Meiosis
Why do gametes need half the number of chromosomes? [1 mark]
Answer:
So that when gametes join at fertilisation, the full number of chromosomes is restored.
Question 5 · Spec 4.6.1.3 · Reproduction
State two advantages of sexual reproduction. [2 marks]
Answer:
Any two from: produces variation in offspring (1); a species can survive if the environment changes (1); humans can use selective breeding (1).
Question 6 · Spec 4.6.1.3 · Reproduction
State two advantages of asexual reproduction. [2 marks]
Answer:
Any two from: only one parent needed (1); more time and energy efficient (1); faster than sexual reproduction (1); many identical offspring when conditions are favourable (1).
Question 7 · Spec 4.6.1.3 · Both types
Give two examples of organisms that reproduce both sexually and asexually. [2 marks]
Answer:
Any two from: malarial parasites (1); fungi (1); plants such as strawberries (runners) and daffodils (bulbs) (1).
Question 8 · Spec 4.6.1.4 · DNA
What is a gene? [1 mark]
Answer:
A small section of DNA that codes for a particular sequence of amino acids to make a specific protein.
Question 9 · Spec 4.6.1.4 · DNA
What is the genome? [1 mark]
Answer:
The entire genetic material of an organism.
Question 10 · Spec 4.6.1.4 · Human genome
State two reasons why studying the human genome is important. [2 marks]
Answer:
Any two from: searching for genes linked to diseases (1); understanding and treating inherited disorders (1); tracing human migration patterns (1).
Question 11 · Spec 4.6.1.5 · DNA structure
Describe the structure of DNA. [2 marks]
Answer:
A polymer of two strands forming a double helix (1); made of repeating nucleotide units (1).
Question 12 · Spec 4.6.1.5 · DNA structure
What does each nucleotide consist of? [2 marks]
Answer:
A common sugar and a phosphate group (1); and one of four bases: A, C, G or T (1).
Question 13 · Spec 4.6.1.5 · DNA structure · Higher only
Which bases pair together in DNA? [1 mark]
Answer:
A pairs with T, and C pairs with G.
Question 14 · Spec 4.6.1.5 · Protein synthesis · Higher only
Describe how proteins are made on ribosomes. [2 marks]
Answer:
The order of bases in a gene is a code; three bases code for one amino acid (1); carrier molecules bring amino acids to the ribosome to join in the correct order (1).
Question 15 · Spec 4.6.1.5 · Mutations · Higher only
Explain how a mutation can change a protein. [2 marks]
Answer:
A change in the base sequence changes the amino acid sequence (1); so the protein folds into a different shape and may not work, e.g. an enzyme's active site changes (1).
Question 16 · Spec 4.6.1.6 · Genetics
Define the term 'allele'. [1 mark]
Answer:
A different form of the same gene.
Question 17 · Spec 4.6.1.6 · Genetics
Define 'homozygous' and 'heterozygous'. [2 marks]
Answer:
Homozygous: both alleles are the same (1). Heterozygous: the two alleles are different (1).
Question 18 · Spec 4.6.1.6 · Genetics
What is the difference between genotype and phenotype? [2 marks]
Answer:
Genotype is the alleles present (1); phenotype is the characteristic that is expressed (1).
Question 19 · Spec 4.6.1.6 · Genetic crosses
Two heterozygous parents (Bb) are crossed. What is the probability of a homozygous recessive offspring? [2 marks]
Answer:
Offspring genotypes: BB, Bb, Bb, bb (1); probability of bb = 1 in 4 (25%) (1).
Question 20 · Spec 4.6.1.6 · Genetic crosses
A cross gives 75 tall and 25 short plants. What is the ratio of tall to short? [1 mark]
Answer:
3 : 1.
Question 21 · Spec 4.6.1.7 · Inherited disorders
What causes polydactyly and how is it inherited? [2 marks]
Answer:
Extra fingers or toes (1); caused by a dominant allele (1).
Question 22 · Spec 4.6.1.7 · Inherited disorders
What is cystic fibrosis and how is it inherited? [2 marks]
Answer:
A disorder of cell membranes causing thick mucus (1); caused by a recessive allele, so both parents must be carriers or sufferers (1).
Question 23 · Spec 4.6.1.7 · Embryo screening
Give one argument for and one against embryo screening. [2 marks]
Answer:
For: prevents suffering from inherited disorders (1). Against: it is expensive, and some people fear it could lead to 'designer babies' (1).
Question 24 · Spec 4.6.1.8 · Sex determination
Which sex chromosomes do males and females have? [2 marks]
Answer:
Females: XX (1). Males: XY (1).
Question 25 · Spec 4.6.1.8 · Sex determination
What is the probability of a baby being female? [1 mark]
Answer:
50% (1 in 2), as half of sperm carry X and half carry Y.
Question 26 · Spec 4.6.2.1 · Variation
State the two causes of variation. [2 marks]
Answer:
Genetic causes (the genes inherited) (1); environmental causes (the conditions in which they develop) (1).
Question 27 · Spec 4.6.2.2 · Evolution
Describe the theory of evolution by natural selection. [3 marks]
Answer:
There is variation in a population due to mutations (1); individuals with characteristics best suited to the environment are more likely to survive and breed (1); they pass on their alleles, so over many generations the characteristic becomes more common (1).
Question 28 · Spec 4.6.2.2 · Speciation
When have two populations become different species? [1 mark]
Answer:
When they can no longer interbreed to produce fertile offspring.
Question 29 · Spec 4.6.2.3 · Selective breeding
Describe the process of selective breeding. [3 marks]
Answer:
Choose parents with the desired characteristic (1); breed them together (1); choose the best offspring and repeat over many generations (1).
Question 30 · Spec 4.6.2.3 · Selective breeding
State one risk of selective breeding. [1 mark]
Answer:
Inbreeding, which makes some breeds prone to disease or inherited defects.
Question 31 · Spec 4.6.2.4 · Genetic engineering
Describe the process of genetic engineering. [3 marks]
Answer:
The required gene is cut out using enzymes (1); it is inserted into a vector such as a bacterial plasmid or virus (1); the vector inserts the gene into the required cells (1).
Question 32 · Spec 4.6.2.4 · Genetic engineering
Give two examples of genetic engineering. [2 marks]
Answer:
Any two from: bacteria modified to make human insulin (1); GM crops resistant to insects or herbicides (1); crops with bigger, better fruits (1).
Question 33 · Spec 4.6.2.4 · Genetic engineering
Give one benefit and one concern about GM crops. [2 marks]
Answer:
Benefit: increased yields (1). Concern: possible effects on wild flowers and insect populations or on human health (1).
Question 34 · Spec 4.6.2.5 · Cloning
Describe tissue culture. [2 marks]
Answer:
Small groups of cells from part of a plant are used (1); to grow identical new plants, for example rare species (1).
Question 35 · Spec 4.6.2.5 · Cloning
Describe how adult cell cloning is carried out. [3 marks]
Answer:
The nucleus is removed from an unfertilised egg cell (1); the nucleus from an adult body cell is inserted into it (1); an electric shock makes it divide to form an embryo, which is inserted into the womb of an adult female (1).
Question 36 · Spec 4.6.2.5 · Cloning
What are embryo transplants? [2 marks]
Answer:
Cells from a developing animal embryo are split apart before they specialise (1); the identical embryos are transplanted into host mothers (1).
Question 37 · Spec 4.6.3.1 · Darwin
What evidence helped Darwin develop his theory? [2 marks]
Answer:
Observations during a round-the-world voyage, e.g. on the Galápagos Islands (1); experimentation and his knowledge of geology, fossils and breeding (1).
Question 38 · Spec 4.6.3.1 · Darwin
State two reasons why Darwin's theory was only gradually accepted. [2 marks]
Answer:
Any two from: it challenged the idea that God made all living things (1); there was not enough evidence at the time (1); the mechanism of inheritance and variation was not known (1).
Question 39 · Spec 4.6.3.1 · Lamarck
What was Lamarck's theory? [1 mark]
Answer:
That changes during an organism's lifetime could be inherited.
Question 40 · Spec 4.6.3.2 · Speciation
Who was Alfred Russel Wallace? [1 mark]
Answer:
A scientist who independently proposed natural selection and worked on warning colouration and speciation.
Question 41 · Spec 4.6.3.3 · Genetics
What did Mendel discover? [2 marks]
Answer:
From breeding pea plants, he found characteristics are determined by 'units' passed on unchanged (1); he did not know about genes or chromosomes, so his work was not recognised until after his death (1).
Question 42 · Spec 4.6.3.4 · Evidence for evolution
State two pieces of evidence for evolution. [2 marks]
Answer:
Any two from: fossils (1); antibiotic resistance in bacteria (1); comparing DNA of different species (1).
Question 43 · Spec 4.6.3.5 · Fossils
State two ways fossils are formed. [2 marks]
Answer:
Any two from: from parts of organisms that have not decayed because conditions were unsuitable (1); when parts are replaced by minerals (1); as traces such as footprints and burrows (1).
Question 44 · Spec 4.6.3.5 · Fossils
Why is the fossil record incomplete? [2 marks]
Answer:
Many early forms of life were soft-bodied and left few traces (1); many fossils have been destroyed by geological activity (1).
Question 45 · Spec 4.6.3.6 · Extinction
State three causes of extinction. [3 marks]
Answer:
Any three from: new predators (1); new diseases (1); new, more successful competitors (1); changes to the environment, such as climate change (1); a catastrophic event (1).
Question 46 · Spec 4.6.3.7 · Resistant bacteria
Explain how antibiotic resistance develops. [3 marks]
Answer:
A random mutation makes some bacteria resistant (1); they survive the antibiotic and reproduce (1); the resistant strain spreads because people are not immune and there is no effective treatment (1).
Question 47 · Spec 4.6.3.7 · Resistant bacteria
State two ways to reduce the development of resistant strains. [2 marks]
Answer:
Any two from: doctors should not prescribe antibiotics for non-serious or viral infections (1); patients should complete the course (1); restrict agricultural use of antibiotics (1).
Question 48 · Spec 4.6.4 · Classification
List Linnaeus's classification groups in order from kingdom. [2 marks]
Answer:
Kingdom, phylum, class, order (1); family, genus, species (1).
Question 49 · Spec 4.6.4 · Classification
What is the binomial system? [1 mark]
Answer:
Naming organisms by their genus and species, e.g. Homo sapiens.
Question 50 · Spec 4.6.4 · Classification
Name Carl Woese's three domains. [2 marks]
Answer:
Archaea and Bacteria (1); Eukaryota (1).

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