Sexual and asexual reproduction and when each is an advantage, what meiosis does and how it differs from mitosis, and organisms that use both.
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1.What is sexual reproduction?
Reproduction involving the fusion of male and female gametes, mixing genetic information from two parents.
2.What is asexual reproduction?
Reproduction involving only one parent and no gametes. There is no mixing of genetic information.
3.Which type of cell division is used in asexual reproduction?
Mitosis.
4.What are the offspring of asexual reproduction called?
Clones, because they are genetically identical to the parent.
5.Name the gametes in animals.
Sperm cells and egg cells.
6.Name the gametes in flowering plants.
Pollen cells and egg cells.
7.What type of cell division produces gametes?
Meiosis.
8.Where does meiosis happen?
In the reproductive organs.
9.How many cells does meiosis produce, and what are they like?
Four cells, each genetically different from the others and from the parent cell.
10.How many chromosomes does a gamete have compared with a body cell?
Half as many. A human gamete has 23, a body cell has 46.
11.Describe what happens during meiosis.
The chromosomes are copied, then the cell divides twice, so four gametes are formed each with a single set of chromosomes.
12.What happens at fertilisation?
Two gametes fuse, restoring the normal number of chromosomes and forming a new cell with a mix of genetic information from both parents.
13.What happens after fertilisation?
The new cell divides repeatedly by mitosis, and as the embryo develops the cells differentiate into specialised types.
14.Give two advantages of sexual reproduction.
It produces variation in the offspring, and if the environment changes that variation gives a survival advantage by natural selection. It is also used in selective breeding.
15.Give three advantages of asexual reproduction.
Only one parent is needed, it is much faster than sexual reproduction, and many identical offspring can be produced when conditions are favourable.
16.Give a disadvantage of asexual reproduction.
There is no variation, so if conditions change or a disease appears, the whole population may be affected equally.
17.Which organism can reproduce both sexually and asexually depending on conditions?
Malarial parasites reproduce asexually in the human host and sexually in the mosquito. Many fungi and plants can also do both.
18.How do many plants reproduce asexually?
By producing runners, bulbs or tubers, as strawberry plants and daffodils do.
19.How do fungi reproduce in both ways?
They produce spores asexually to spread quickly, and reproduce sexually to give variation.
20.Compare the daughter cells from mitosis and meiosis.
Mitosis produces two genetically identical cells with the full number of chromosomes. Meiosis produces four genetically different cells with half the number.
21.Why is variation from sexual reproduction useful?
It means some individuals may be better suited to a changed environment, so the species is more likely to survive.
22.Why does meiosis have to halve the chromosome number?
So that when two gametes fuse at fertilisation the offspring has the correct number, rather than double it each generation.
23.What does it mean to say gametes are haploid?
They contain one set of chromosomes rather than two.
24.What does diploid mean?
Containing two sets of chromosomes, which is the normal state of a body cell.
25.Give an example of asexual reproduction used commercially.
Taking cuttings from a plant with desirable characteristics to produce many identical plants cheaply.
26.Why might a gardener prefer asexual reproduction?
The offspring are identical to the parent, so a plant with good flowers or fruit is reproduced exactly.
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