Key Area 3-Variation and Sexual Reproduction Flashcards
(42 cards)
What is sexual reproduction?
The formation of haploid gametes of 2 parents that fuse nuclei to form diploid zygotes
What are the two main disadvantages of sexual reproduction?
- half of the population are unable to produce offspring (paradox of the existence of men)
- by mixing the genetic information between two individual each parent disrupts a successful genome and only passes in half to each offspring
What is the main benefit of sexual reproduction?
It creates genetic diversity and variation therefore allows evolution
How does genetic variation link to the red queen hypothesis?
It’s essential that genetic variation occurs to allow constant running to stay in the same place
What is asexual reproduction?
The cloning of one single parent to form genetically identical offspring
Where does asexual reproduction occur?
Usually prokaryotes but some eukaryotes such as plants
Where is asexual reproduction particularly successful as a reproductive strategy?
Very narrow niches or when recolonising disturbed habitats
What is the name given to asexual reproduction in plants?
Vegetative propagation
Where is vegetative propagation a useful strategy?
Perennial weeds
What are two examples of eukaryotic organisms reproducing asexually?
Vegetative propagation
Parthenogenesis
What is parthenogenesis?
Where animals are capable of reproducing without fertilisation of eggs
What are the two conditions where parthenogenesis usually occurs?
Cooler climates
Where parasite diversity/density is low
Give two specific examples of parthenogenesis
Komodo dragons where females can reproduce alone in the absence of males and produce male offspring only
Stick insects can reproduce alone in the absence of males and produce female offspring only
What is mitosis?
The process of cell division that results in the formation of new diploid cells
What is meiosis?
The process of cell division that results in the formation of new haploid cells
What is a homologous chromosome?
Homologous chromosomes have the same:
Size
Centromeres in the same place
Carry the same genes at the same Loki
How does meiosis affect variation in organisms?
Increases variation
What are the two divisions in meiosis and the products formed at each division?
Meiosis I - two haploid daughter cells with double the DNA
Meiosis II - four haploid gamete cells
What cell begins meiosis?
A gamete mother cell (2n)
What is the first stage in meiosis I?
Interphase where DNA replicates to form 2 sister chromatids
What occurs in meiosis I after interphase?
Homologous chromosomes line up in pairs along the metaphase plate
How do homologous chromosomes line up along the metaphase plate?
In an independent assortment
What does an independent assortment assure in meiosis?
Further variation
What occurs in meiosis I after homologous chromosomes line up?
The pairs touch at chiasmata and crossing over occurs which results in recombination of alleles (swapped DNA)
