One advantage of sexual reproduction over asexual reproduction is that it helps species to survive over long evolutionary time. This is because sexual reproduction produces :
- A.more offspring in each reproductive cycle.
- B.robust and healthy offspring.
- C.genetically similar offspring.
- D.more variation in offspring.
Correct answer
Explanation
The correct answer is D, more variation in offspring. Sexual reproduction mixes the genes of two parents, so the young differ from each other and from their parents, and variation helps a species survive changing conditions.
In sexual reproduction, gametes are formed by meiosis, during which crossing over and the random sorting of chromosomes shuffle the genes. Fertilisation then combines a gamete from each parent, creating a new mix every time. When the environment changes, through a new disease, a drought or a change in temperature, some of these varied individuals are more likely to cope and pass on their genes. Over long periods this variation is the raw material for natural selection and evolution.
A is wrong because asexual reproduction usually produces more offspring, and faster.
B is wrong because sexual reproduction does not guarantee robust or healthy young; harmful traits can be passed on too.
C is wrong because genetically similar offspring, or clones, are the result of asexual reproduction.
Exam tip: sexual reproduction gives variation, the raw material of evolution; asexual reproduction gives clones.
Practice Questions
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