BIO 115
Human evolution
Human evolution
Fichier Détails
| Cartes-fiches | 288 |
|---|---|
| Langue | English |
| Catégorie | Biologie |
| Niveau | Université |
| Crée / Actualisé | 23.01.2021 / 24.01.2021 |
| Lien de web |
https://card2brain.ch/box/20210123_bio_115
|
| Intégrer |
<iframe src="https://card2brain.ch/box/20210123_bio_115/embed" width="780" height="150" scrolling="no" frameborder="0"></iframe>
|
Influence of ageing on natural selection
If mutation kills you in young age -> strong negartive selection as mutation is not passed to the next generation
If mutation kills you late after reproduction -> selection has less power to eliminate mutation
Where is the important correlation? (Life history model)
The important correlation is between mortality rates and reproductive rates
-> power of selection decreases as reproductive potential decreases
What is the same as death for the natural selection process? (Life history model)
Post-reproductive life e.g. post-menopause women
Ageing Theory: The mutation accumulation hypothesis
All deleterious mutations accumulate as natural selection cannot eliminate them -> senescence
Integration of ageing into the life history model
1) Ecological death or extrinsic mortality leads to the evolution of the life cycle
2) Senscence is part of the cycle and part of the adaption to ecological death
3) Repairing damages is expensive -> does not pay-off after reproduction
Antagonistic pleiotropy hypothesis
Williams (1957)
- pleiotropy: one gene has more than one effect on the phenotype
- antagonistic: one effect is beneficial the other is detrimental
-> if organisms race to have as many offspring as possible -> investment in early life would be selected for at the cost of late decline
Example: Antagonistic pleiotropy hypothesis
Mutation increases reproduction in early age and causes deleterious effects at old age -> mutation would be selected for
-> Reproduction is favoured over soma
Life history model (summary)
1) we age because we die - ecological mortality rates determine until when to invest in soma
2) because death is inevitable - does not pay to invest in DNA repair - better invest in reproduction
3) ageing is consequence of accumulating bad mutations at old age
4) age can be accelerated by antagonistic pleiotropy - genes that favour early reproduction are favoured even if they lead to negative effects later on
