What does asexual reproduction involve?
One parent
No gametes
Mitosis only
Genetically identical offspring
What does sexual reproduction involve?
Two parents
Gametes involved
Meiosis
Genetically variable offspring
What are the gametes involved in animals?
Sperm and egg
What are the gametes involved in plants?
Pollen and egg
How many chromosomes are there in asexual compared to sexual?
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
What are the advantages of asexual reproduction?
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
Advantages of sexual reproduction
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
Examples of asexual reproduction
Binary fission in bacteria Budding in yeast Spider plant producing runner Daffodils Strawberry plant Fungi by spores Malarial protists
How do strawberry plants reproduce asexually?
They send out long shoots called runners, which touch the ground and grow a new plant
How do daffodils reproduce asexually?
Daffodils produce lots of smaller bulbs, which can grow into new plants
Describe meiosis
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
Why is meiosis important?
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
What organisms can reproduce both sexually and asexually?
Many plants e.g. Using bulbs and runners
Many fungi can make spores
Malaria parasites reproduce sexually in the mosquito and asexually in humans
