B10.1 : Asexual and Sexual Reproduction

Question 1

Asexual reproduction

Answer 1

1. Asexual reproduction is the process of reproduction that forms genetically identical offspring from only one parent.
2. Asexual reproduction is common in single-celled organisms and some plants.

Question 2

Key features of Asexual reproduction

Answer 2

1. Offspring are clones
2. Only one parents
3. Cells divide by mitosis
4. No gamete fusion

Question 3

Cells divide by mitosis

Answer 3

1. The two sets of chromosomes are pulled to opposite ends of the cell.
2. Then, the nucleus divides into two.

Question 4

Pros of asexual reproduction

Answer 4

1. lots of identical offspring : This is very useful for crop production, as when favourable characteristics are shown these can be replicated.
2. faster : Asexual reproduction is faster than sexual reproduction.
3. No mate required : Asexual reproduction is efficient with regards to time and energy.

Question 5

Cons of asexual reproduction

Answer 5

1. can’t cope with environmental change : There is no variation in the population, and so any change in the environment affects all individuals of the species.

Question 6

Examples of asexual reproduction

Answer 6

1. Sponges
2. Blackberries
3. Starfish
4. Hydra

Question 7

Bacteria

Answer 7

1. Reproduces tremendously fast (as often as every 20 minutes)
2. Bacteria needs to have certain conditions in which to reproduce
3. Conditions often not met and that is one thing that keeps bacteria from growing out of control

Question 8

Types of asexual reproduction

Answer 8

1. Budding
2. Spores
3. Runners
4. Bulbs
5. Binary fission
6. Cuttings

Question 9

Bulbs

Answer 9

1. Many plants naturally develop underground food storage organs that later develop into the following year’s plants
2. potato tubers and daffodil bulbs are examples of this.

Question 10

Runners

Answer 10

1. Some plants naturally produce side branches with plantlets on them.
2. The spider plant does this.
3. Other plants, such as strawberries, produce runners with plantlets on them.

Question 11

Cuttings

Answer 11

1. The simplest and easiest way to clone a plant is to take a cutting from it
2. A side branch is cut off a parent plant
3. The lower leaves are removed and the stem is planted in damp compost or placed in water
4. The cut end of the stem can be dusted with rooting powder before planting
5. This contains the plant hormone auxin which encourages growth of new roots

Question 12

Sexual Reproduction

Answer 12

1. The process of reproduction where the nuclei of two gametes (sex cells) fuse to form a zygote (a process known as fertilisation), producing offspring that are genetically different to one another.

Question 13

Key features of sexual reproduction

Answer 13

1. Two parents
2. Male and Female gametes fuse
3. Offspring are not identical
4. Cells divide by meiosis

Question 14

Male and Female gametes fuse

Answer 14

1. Sperm and egg cells are the gametes in animals.

2. Pollen and ovum cells contain the gametes in flowering plants.

Question 15

Pros of sexual reproduction

Answer 15

1. variation in offspring

2. selective breeding

Question 16

Cons of sexual reproduction

Answer 16

1. harmful variations

2. need two parents

Question 17

Selective breeding

Answer 17

1. Humans can speed up artificial selection through selective breeding of plants and animals.
2. This depends on genetic variation and being able to select those with the most favourable characteristics.
3. This process has many benefits, including boosting food production and breeding fast horses.

Question 18

Harmful variations

Answer 18

Fertilisation is random, and so harmful variations can be created.

Question 19

Variation in offspring

Answer 19

1. Variation in the offspring increases the chances of a population being able to survive environmental change by natural selection.
2. This is because some individuals are likely to be adapted to the new conditions.

Question 20

gametes and zygotes

Answer 20

1. During sexual reproduction, gamete nuclei fuse to form a zygote.
2. There is an important difference between the nuclei of these types of cell.

Question 21

Zygote nuclei

Answer 21

1. Zygote nuclei are diploid.
2. This means they contain two complete sets of chromosomes.
3. This is because they have one set of chromosomes from each parent.
4. In humans, each diploid cell has 23 pairs of chromosomes.

Question 22

Gamete nuclei

Answer 22

1. Gamete nuclei are haploid.
2. This means they contain half the number of chromosomes found in a normal cell.
3. HaploidThis is because they contain one complete set of chromosomes.

Question 23

haploid

Answer 23

one set of chromosomes

Question 24

diploid

Answer 24

two sets of chromosomes