Which one of the following statements about natural selection is not correct?
- A.Natural selection can only occur if there is no variation amongst members of the same species.
- B.Over time, natural selection can increase the frequency of adaptations that are favourable in a given environment.
- C.Species tend to overproduce beyond what the environment can support.
- D.Mutation, meiosis and sexual reproduction cause variation between individuals of a species.
Correct answer
Explanation
The correct answer is A. Natural selection needs variation among members of a species; without variation there is nothing for nature to select, so statement A is the incorrect one.
Charles Darwin and Alfred Russel Wallace explained evolution by natural selection. Organisms produce more offspring than can survive, so they compete for food and space. Individuals differ from one another, and those whose traits suit the environment survive longer and leave more young. Over many generations the favourable traits become common in the population. Variation is therefore the raw material of evolution.
B is correct because natural selection steadily raises the share of useful adaptations in a population. C is correct because overproduction of offspring leads to the struggle for existence. D is correct because mutation, the shuffling of genes during meiosis and the mixing of genes in sexual reproduction create the differences between individuals.
Exam tip: Darwin's chain is overproduction, struggle for existence, variation, survival of the fittest, origin of new species.
Practice Questions
View allIf one set of chromosomes for a given plant is represented as N; in case of double fertilization, the zygote and the endosperm nucleus of a diploid plant would have how many sets of chromosomes respectively?
- A.N and 2N
- B.2N and 2N
- C.N and 3N
- D.2N and 3N
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The zygote is diploid (2N) and the primary endosperm nucleus is triploid (3N). Double fertilisation is a feature of flowering plants.
Read the full explanation →Which one of the following statements is NOT correct for the given reaction? Fe(s) + CuSO4(aq) → FeSO4(aq) + Cu(s)
- A.Iron is the reducing agent
- B.The solution turns green in colour after the reaction
- C.Copper is a more reactive metal than iron
- D.The reaction is an example of a redox reaction
Show answer
The reaction happens because iron is more reactive than copper and pushes it out of its salt, so statement C is false.
Read the full explanation →Which one of the following statements is correct ?
- A.Xylem consists of tracheids, vessels, xylem parenchyma and xylem fibres.
- B.Flexibility in plants is due sclerenchyma.
- C.Parenchyma have no intercellular spaces.
- D.Xylem consists of sieve plate, sieve tube and companion cells.
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These four elements make up the complex tissue that carries water and minerals upward from the roots. Tracheids and vessels are long, dead, thick-walled tubes through which water moves; xylem parenchyma is the only living part and stores food; xylem fibres give support.
Read the full explanation →When light is scattered by a molecule and the frequency of the scattered light is changed, this phenomenon is called
- A.Rayleigh scattering.
- B.Raman effect.
- C.Photoelectric effect.
- D.Rutherford scattering.
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In the Raman effect, a small part of the light scattered by molecules comes out with a changed frequency. C.V.
Read the full explanation →Which one of the following is not an example of a redox reaction?
- A.AlCl3 + 3H2O → Al(OH)3 + 3HCl
- B.2NaH → 2Na + H2
- C.4Fe + 3O2 → 2Fe2O3
- D.CuSO4 + Zn → Cu + ZnSO4
Show answer
This is a hydrolysis reaction in which no element changes its oxidation number, so nothing is oxidised or reduced. A redox reaction is one in which one substance loses electrons (its oxidation number rises) and another gains them (its oxidation number falls).
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