Topic 6- Reproduction

Question 1

What are gametes?

Answer 1

-Sex cells (Sperm cells and egg cells in animals, pollen and egg cells in flowering plants)
- Haploid (half the number of chromosomes)

Question 1

What is sexual reproduction?

Answer 1

-Type of reproduction
-Involves the production of gametes by meiosis
-A gamete from from each parent fuses to form a zygote
-Genetic information from each gamete is mixed so the resulting zygote is unique

Question 2

What is meiosis?

Answer 2

-Form of cell division involved in the formation of gametes (non-identical haploid cells) in reproductive organs
-Chromosomes number is halved
-Involves two division

Question 3

What must occur prior to meiosis?

Answer 3

Interphase- copies of genetic information are made during this process

Question 4

What happens during the first stage of meiosis

Answer 4

-Chromosome pairs line up along the cell equator
-The pair of chromosomes are separated and move to opposite poles of the cell (the side to which each chromosome is pulled is random, creating variation)
-Chromosome number is halved

Question 5

What happens during the second stage of meiosis?

Answer 5

-Chromosomes line up along the cell equator
-The chromatids are separated and move to opposite poles of the cell
-Four unique haploid gametes are produced

Question 6

Why is meiosis important for sexual reproduction?

Answer 6

-It increases genetic variation
-It ensures that the zygote formed at fertilisation is diploid

Question 7

Describe fertilisation and its resulting outcome

Answer 7

Gametes join together to restore the normal number of chromosomes and the new cell then divides by mitosis (which increases the number of cells)
As the embryo develops, cells differentiate

Question 8

What is the advantage of sexual reproduction?

Answer 8

It creates genetic variation in offspring, increasing the probability of a species adapting to and surviving environmental changes
Natural selection can be speeded up by humans in selective breeding to increase food production

Question 9

Describe the disadvantages of sexual reproduction

Answer 9

-Two parents are required. This makes reproduction difficult in endangered populations or in species which exhibit solitary lifestyles
-More time and energy is required so fewer offspring are produced

Question 10

What is asexual reproduction?

Answer 10

Type of reproduction
Involves mitosis only
Produces genetically identical offspring known as daughter cells

Question 11

Describe the advantages of asexual reproduction

Answer 11

Only one parent is required
Lots of offspring can be produced in a short period of time, enabling the rapid colonisation of an area and reducing competition from other species
Requires less energy and time as do not need a mate

Question 12

What is the disadvantage of asexual reproduction?

Answer 12

No genetic variation (except from spontaneous mutations) reducing the probability of a species being able to adapt to environmental change

Question 13

Describe the circumstances in which Malarial parasites reproduce sexually and asexually

Answer 13

Sexual reproduction in the mosquito
Asexual reproduction in the human host

Question 14

Describe the circumstances in which fungi reproduce sexually and asexually

Answer 14

Asexual reproduction by spores
Sexual reproduction to given variation

Question 15

Describe the circumstances in which plants reproduce sexually and asexually

Answer 15

Sexual reproduction to produce seeds
Asexual reproduction by runners (e.g strawberry plants) or bulb division (e.g daffodils)

Question 16

What is DNA?

Answer 16

A double-stranded polymer of nucleotides, wound to form a double helix
The genetic material of the cell found in nucleus