Reproduction

Question 1

What does sexual reproduction involve

Answer 1

Involved the joining fusion of male and female gametes
- speem and egg in animals
- pollen and egg cells in flowering plants.

Question 2

What is sexual reproduction?

Answer 2

There is a mixing of genetic information which leads to variety in the offspring. Formation of gametes involves meiosis

Question 3

What is asexual reproduction?

Answer 3

Involves only one parent and no fusion of gametes. There is no mixing of genetic information. This leads to genetically identical offspring - clones. Only mitosis is involved

Question 4

Mitosis

Answer 4

Nuclear division which gives rise to cells that are genetically identical. Used for growth, repair and damaged tissues, replacement of cells and asexual reproduction

Question 5

Meiosis

Answer 5

A type of nuclear division that gives rise to cells that are genetically different - it is used to produce gametes (sex cells)

Question 6

What happens when a cell divides to form gametes?

Answer 6

• Copies of genetic information are made
• the cell divides twice to form, four gametes, each with a single set of chromosomes
• all gametes are genetically different from each other

Question 7

What happens to gametes during fertilization

Answer 7

Gametes join at fertilization to restore the normal number of chromosomes. New cell divides by mitosis. Number of cells increases. As the embryo develops cells differentiate

Question 8

What must happen to the number of chromosomes when a gamete is formed?

Answer 8

It must be halved. This occurs during meiosis- reduction division - chromosome is halved from diploid to haploid resulting in genetically different cells.

Question 9

Fertilization

Answer 9

Gametes join at fertilization to restore normal no. Of chromosomes. Becomes a zygote - divided by mitosis to form new cells and continue to divide to form embryo. Cell division continues many new cells become specialized to form particular functions

Question 10

Advantages of sexual reproduction

Answer 10

• Produces variation in offspring
• if environment changes variation gives survival advantage by natural selection
• natural selection can be speeded up by humans in selective breeding to increase food production

Question 11

Advantages of asexual reproduction

Answer 11

• only one parent needed
• more time and energy effecient as do not need to find mate
• faster then sexual
• many identical offspring can be produced when conditions are favorable

Question 12

Which organisms reproduce by both methods?

Answer 12

• malarial parasites reproduce asexually in human host, sexually in mosquito
• many fungi reproduce asexually by spores but also produce sexually to give variation
• many plants produce seeds sexually, asexually by runners such as strawberries plants, or bulb division such as daffodils

Question 13

Disadvantages of sex reproduction

Answer 13

Takes time and energy to find mates

Difficult for isolated members of the species to reproduce

Question 14

Disadvantage of ASex reproduction

Answer 14

Limited genetic variation in population

The population is vulnerable to changes in conditions and may only be suited for one habitat

Disease is more likely to affect the whole population as there is no genetic variation

Question 16

Which cells divide by meiosis

Answer 16

Cells in the reproductive organs to form gametes. Number of chromosomes must be halved when the gameteformed

Question 18

What happens after the zygote is formed?

Answer 18

Contains the full number of chromosomes half from male half from female. Divide by mitosis to form two new cells which continued to divide and after a few days for an. Embryo. Cell division continues, and eventually many of the new cells become specialized