Pearson Edexcel GCSE Combined Science · B4

Natural selection and genetic modification

50 revision questions with answers for B4 Natural selection and genetic modification in Pearson Edexcel GCSE Combined Science (spec 1SC0). Practise with flashcards, a topic quiz, a random quiz across the course, 5 crosswords, or read every question and answer below.

All 50 questions and answers

Question 1 · Spec B4.2
What does evolution mean?
Answer:
Change in inherited characteristics of populations over generations.
Question 2 · Spec B4.2
What is natural selection?
Answer:
Individuals with advantageous inherited traits survive and reproduce more successfully, making those traits more common.
Question 3 · Spec B4.2
Why is variation necessary for natural selection?
Answer:
Individuals must differ in inherited characteristics for some to have a reproductive advantage over others.
Question 4 · Spec B4.2
What is a selection pressure?
Answer:
An environmental factor, such as predation or disease, that affects survival and reproductive success.
Question 5 · Spec B4.2
Why must a beneficial characteristic be inherited to spread through natural selection?
Answer:
It must be passed to offspring for its frequency to increase across generations.
Question 6 · Spec B4.2
Why is saying organisms change because they need to misleading?
Answer:
Variation does not arise in response to need; selection favours existing or newly arising inherited differences.
Question 7 · Spec B4.2
How can camouflage become more common in a prey population?
Answer:
Better-camouflaged individuals are less often eaten and leave more offspring carrying the relevant alleles.
Question 8 · Spec B4.3
How can an antibiotic-resistant bacterium first arise?
Answer:
A random mutation can produce an allele that gives resistance.
Question 9 · Spec B4.3
How does antibiotic use select resistant bacteria?
Answer:
Susceptible bacteria are killed; resistant survivors reproduce and pass resistance to descendants.
Question 10 · Spec B4.3
Why does antibiotic resistance provide evidence for evolution?
Answer:
It shows inherited population characteristics changing over generations in response to selection.
Question 11 · Spec B4.3
Why does an antibiotic not teach bacteria to resist it?
Answer:
It selects resistant variants rather than deliberately producing a useful response in each bacterium.
Question 12 · Spec B4.3
Why can unnecessary antibiotic use increase resistance problems?
Answer:
It creates additional selection favouring resistant bacteria, allowing them to become more common.
Question 13 · Spec B4.4
How old is Ardi in the specification?
Answer:
About 4.4 million years.
Question 14 · Spec B4.4
What combination of features makes Ardi informative about evolution?
Answer:
It has evidence consistent with upright walking alongside climbing adaptations, including a grasping big toe.
Question 15 · Spec B4.4
How old is Lucy in the specification?
Answer:
About 3.2 million years.
Question 16 · Spec B4.4
What features support the interpretation that Lucy walked upright?
Answer:
Her short broad pelvis and inward-angled thigh bones support weight-bearing on two legs.
Question 17 · Spec B4.4
Which named evidence is associated with Richard Leakey's team and about 1.6 million years ago?
Answer:
Homo erectus fossils, including the Turkana Boy skeleton.
Question 18 · Spec B4.4
What do Homo erectus body proportions suggest about locomotion?
Answer:
Relatively long legs and shorter arms support efficient upright walking compared with earlier forms.
Question 19 · Spec B4.4
Put Ardi, Lucy and the 1.6-million-year-old fossils in age order, oldest first.
Answer:
Ardi, Lucy, then the fossils associated with Richard Leakey's team.
Question 20 · Spec B4.4
How much older is Ardi than Lucy, using the specified ages?
Answer:
4.4 − 3.2 = 1.2 million years.
Question 21 · Spec B4.4
Why should a fossil's interpretation be based on several skeletal features?
Answer:
One incomplete feature may be ambiguous; several independent observations strengthen the conclusion.
Question 22 · Spec B4.5
What broad trend is seen in stone-tool development?
Answer:
Tools generally became more carefully shaped, complex and suited to particular uses over time.
Question 23 · Spec B4.5
How can the environment around a stone tool help date it?
Answer:
Its position in sediment layers and the ages of associated rocks or remains can constrain its age.
Question 24 · Spec B4.5
Why is the depth of a tool alone not a precise numerical date?
Answer:
Deposition rates vary and layers can be disturbed; additional dating evidence is needed.
Question 25 · Spec B4.5
Why do stone tools provide different evidence from bones?
Answer:
Tools indicate behaviour and practical abilities, while bones provide evidence about body structure.
Question 26 · Spec B4.7
What evidence led scientists to reconsider the five-kingdom classification?
Answer:
Genetic comparisons revealed major differences between groups previously placed together, especially among prokaryotes.
Question 27 · Spec B4.7
Name the three domains.
Answer:
Bacteria, Archaea and Eukaryota.
Question 28 · Spec B4.7
Why can DNA comparisons reveal relationships missed by appearance alone?
Answer:
They compare inherited molecular information, which may reveal differences or similarities not obvious in external form.
Question 29 · Spec B4.7
Does changing a classification system make previous observations useless?
Answer:
No. New systems reinterpret existing observations alongside new evidence.
Question 30 · Spec B4.8
What is selective breeding?
Answer:
Humans choose organisms with desired characteristics as parents for the next generation.
Question 31 · Spec B4.8
Describe the main steps of selective breeding.
Answer:
Choose suitable parents, breed them, select offspring with desired traits and repeat over generations.
Question 32 · Spec B4.8
Give two desired characteristics in food plants.
Answer:
High yield and resistance to disease; improved food quality is another possibility.
Question 33 · Spec B4.8
Give two desired characteristics in domesticated animals.
Answer:
High milk or meat yield and suitable temperament.
Question 34 · Spec B4.8
Why can selective breeding reduce genetic diversity?
Answer:
Breeding from a restricted group of similar individuals limits the alleles passed to later generations.
Question 35 · Spec B4.8
Why can inbreeding increase inherited problems?
Answer:
Related individuals are more likely to carry the same harmful recessive alleles, increasing homozygous offspring.
Question 36 · Spec B4.8
How does selective breeding differ from natural selection?
Answer:
Humans choose breeding parents in selective breeding; environmental pressures affect reproductive success in natural selection.
Question 37 · Spec B4.10
Define genetic engineering.
Answer:
Modifying an organism's genome to introduce a desired characteristic.
Question 38 · Spec B4.10
How can genetically engineered bacteria help people with diabetes?
Answer:
Introducing a human insulin gene enables the bacteria to produce insulin for medicines.
Question 39 · Spec B4.11 · Higher only
What does a restriction enzyme do in genetic engineering?
Answer:
It cuts DNA at particular sequences, allowing a required gene or a vector to be prepared.
Question 40 · Spec B4.11 · Higher only
What are sticky ends?
Answer:
Short exposed base sequences at cut DNA ends that can pair with complementary ends.
Question 41 · Spec B4.11 · Higher only
Why cut a gene and plasmid with the same suitable restriction enzyme?
Answer:
It produces complementary sticky ends that can pair together.
Question 42 · Spec B4.11 · Higher only
What does DNA ligase do?
Answer:
It joins DNA fragments by sealing their sugar-phosphate backbones.
Question 43 · Spec B4.11 · Higher only
What is a vector in genetic engineering?
Answer:
A carrier, such as a plasmid or virus, that transfers a gene into a target cell.
Question 44 · Spec B4.11 · Higher only
Outline gene transfer using a plasmid.
Answer:
Cut out the gene, cut the plasmid, join matching ends with ligase and introduce the recombinant plasmid into target cells.
Question 45 · Spec B4.14
Give a possible benefit of genetically modified crops.
Answer:
They may resist pests, improve yield or improve nutritional quality, depending on the introduced characteristic.
Question 46 · Spec B4.14
Give a possible environmental risk of genetically modified crops.
Answer:
Introduced genes may spread to wild relatives or affect non-target organisms; risks require evidence-based assessment.
Question 47 · Spec B4.14
Why can genetic engineering raise ethical questions in medicine?
Answer:
People may disagree about acceptable interventions, access to treatment and consequences for individuals or future generations.
Question 48 · Spec B4.14
Compare the speed of selective breeding and genetic engineering.
Answer:
Selective breeding usually requires many generations; genetic engineering can introduce a selected gene more directly.
Question 49 · Spec B4.14
Why should benefits and risks be assessed for a specific modified organism?
Answer:
Different genes, organisms and environments produce different outcomes, so one general claim cannot cover every application.
Question 50 · Spec B4.14
What makes an evaluation of a breeding or modification programme convincing?
Answer:
Use relevant evidence, compare benefits with risks and costs, acknowledge uncertainty and justify the conclusion.

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