4.6 Inheritance, Variation And Evolution

Question 1

What does asexual reproduction involve?

Answer 1

One parent
No gametes
Mitosis only
Genetically identical offspring

Question 2

What does sexual reproduction involve?

Answer 2

Two parents
Gametes involved
Meiosis
Genetically variable offspring

Question 3

What are the gametes involved in animals?

Answer 3

Sperm and egg

Question 4

What are the gametes involved in plants?

Answer 4

Pollen and egg

Question 5

How many chromosomes are there in asexual compared to sexual?

Answer 5

In asexual reproduction, all cells throughout the life cycle have the same number of chromosomes, but in sexual reproduction there are stages where the chromosomes are halved

Question 6

What are the advantages of asexual reproduction?

Answer 6

Only one parent needed so if you live in a hostile environment you can still reproduce. No energy wasted finding mate

No energy finding a mate and competing with rivals

Faster

Identical offspring produced- great if conditions are favourable and organism well suited to exploit resources

Question 7

Advantages of sexual reproduction

Answer 7

Variable offspring- if environment changeable then new variants might have a survival advantage that could lead to the survival of the species by natural selection

Selective breeding leads to increase in food production

Question 8

Examples of asexual reproduction

Answer 8

Binary fission in bacteria
Budding in yeast
Spider plant producing runner
Daffodils
Strawberry plant
Fungi by spores
Malarial protists

Question 9

How do strawberry plants reproduce asexually?

Answer 9

They send out long shoots called runners, which touch the ground and grow a new plant

Question 10

How do daffodils reproduce asexually?

Answer 10

Daffodils produce lots of smaller bulbs, which can grow into new plants

Question 11

Describe meiosis

Answer 11

GETTING READY First the DNA is replicated and the cell grows. There is an increased number of mitochondria and ribosomes

MITOSIS 1 Then separation of homologous chromosomes, I chromosome from each pair to each cell after crossing up

MITOSIS 2 same as mitosis

CYTOKINESIS cytoplasm and cell membrane divide. 4 gametes that are genetically variable are produced

Question 12

Why is meiosis important?

Answer 12

Because it halves the number of chromosomes in gametes. This means fertilisation can restore the full number of chromosomes

23 + 23= 46 chromosomes

Sperm + egg = fertilised egg cell

Question 13

What organisms can reproduce both sexually and asexually?

Answer 13

Many plants e.g. Using bulbs and runners

Many fungi can make spores

Malaria parasites reproduce sexually in the mosquito and asexually in humans