Evolution of Sex Flashcards
Modes of Reproduction
Asexual and Sexual
Asexual Reproduction
Amixis - No mixing
Mitotically based reproduction with no syngamy(fusion of gametes with reduced ploidy)
- Colonial
- Clonal
Amixis
No mixing
Syngamy
Fusion of gametes with reduced ploidy
Asexual Reproduction:
Colonial
Cell division adds to existing colony
- coral reefs
Asexual Reproduction:
Clonal
Reproduction with an individual not connected to you.
- Budding
- Polyembryony
- Apomixis
Asexual Reproduction:
Clonal - Budding
Vegetative reproduction
- seeds fall to ground and grow
- hydra grows a second organism on its side that splits and goes on its own way.
Asexual Reproduction:
Clonal - Polyembryony
One fertilized egg develops into multiple individuals
- Different morphologies but start as 1 embryo
- armadillos
- human twins
Asexual Reproduction:
Clonal - Apomixis
Single unfertilized egg develops into adult.
- an egg never needs sperm to come in and fertilize.
- typically there used to be reproduction but the female population decided to get rid of males.
- males are unnecessary from a biological perspective
Sexual(mixis) Reproduction
Meiotic reduction of ploidy followed by syngamy.
- Automixis
- Amphimixis
Mixis
Mixing of genes
Sexual(mixis) Reproduction:
Automixis
Syngamy within the same parent
- syngamy within mother fuse and creates a new offspring that is diploid
- shuffled the genome still which means it is not a clone
- being Asexual without partner BUT still sexual as you are shuffling your own genome.
Sexual(mixis) Reproduction:
Amphimixis
Syngamy between parents.
- two sexes each produce a miotically reduced gamete which then come together in syngamy to produce diploid offspring.
- Human reproduction
When did sex evolve?
Proterozoic Eon.
1.2 BYA.
Bacteria and Archaea did not engage in sexual reproduction.
How did sex evolve?
Unknown.
3 working models:
- DNA repair strategy(of single chromosome organisms)
- Selfish Genetic Elements
- Transformation(bacterial)