BIO 115

Ageing is caused by the accumulation of irreparable damages to cells and tissues

- Organsims keep genetic repair at maximum -> when damage overcomes repair rate -> ageing

- animals with higher metabolism live longer

- caloric restriction -> reduces metabolic rates -> less oxidative stress and slower ageing -> supports rate of living theory

1) Austad and Fisher (1991) tested amount of energy expended per gram per lifetime -> ageing is not a direct by-product of metabolic rate because animals with higher metabolic rate for the same size would have aged faster

 Expect that animals of same size and close taxa to have same lifspan -> not true

2) If repairing damages is key factor -> selection for extended lifespan would not be possible -> not true, longevity can be selected for (inherited)

- ageing caused by accumulation of somatic damage

- focus on evolution of cell maintenance

- trade-offs between soma and reproduction

-> somatic maintenance needs only to be as good as their chance of survival in the wild

- ageing because we die compared to the other theories where -> we die because we age

- death is an external factor that cannot be completely controlled for by the organism -> time is the most important limitation

Assumptions:

1. Time is a limited ressource

Because accidental death cannot be controlled for (external factor)

The higher the extrinsic mortality the faster the animal's life history

Animal living in high mortality environments -> high rates of predators or accidents -> have shorter life spans -> invest in having more offspring earlier in life

Death is inevitable -> average lifespan is consequence of the ecological mortality rates -> the power of removing deleterious mutations decreases as the chances of accidental death increases

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

The important correlation is between mortality rates and reproductive rates

-> power of selection decreases as reproductive potential decreases

Post-reproductive life e.g. post-menopause women

All deleterious mutations accumulate as natural selection cannot eliminate them -> senescence

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

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

Mutation increases reproduction in early age and causes deleterious effects at old age -> mutation would be selected for

-> Reproduction is favoured over soma

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

- Development of new organisms (IS NOT EVOLUTION)

- Antibiotic resistance -> same bacteria from the 50s are back but resistant to antibiotics

- HIV -> two sources from same ancestor with different traits (HIV1 from chimpanzees and HIV2 from Sooty mangabey)

- Senescence -> natural ageing process

- Model organisms -> mice, drosophila etc.

- Eidos: supernatural ideal imperfectly imitated by humans

- Variation is accidental imperfection

- Species have fixed properties

- Species created by God in similar form as tody

- God's creation follows a plan

- Great chain of being: angels >humans > higher form of life > invertebrates > plants > barely animate forms of life > inanimate objects

- Systema naturae -> classification of animals and plants

- Science was to catalogue God's creation

- Related species -> genera

- Similarities -> populations as one group

- Theory of organic progression -> Transformation of species

- First coherent theory of evolution

- Species originate out of nothing -> spontaneous creation

- Lamarckism -> Inheritance of acquired characteristics

- Species differ because of different needs -> nervous fluid in organs triggers growth e.g. neck of giraffes

- Variational evolution

- Explorer ship -> mocking birds are diffrent on different islands

- Different lineages from single ancestor

- Evolution is not goal-oriented

- Descent with modification -> ancestor

- Natural selection -> survival of the fittest (struggle of life)

Lamarck: Transformational evolution -> e.g. all giraffes developped longer necks to be better adapted

Darwin: Variational evolution -> there is variation in the neck length of giraffes and those who were best adapted produced better adapted offspring (Natural selection)

- Characteristics of organsisms change over time

- Common descent

- Gradualism -> incremental evolution, evolution does not happen over night

- Populational change -> Change in proportions of individuals that have different characteristics

- Natural selection -> Ability to survive and reproduce as a result of changes in adaptions

- History of events by which taxa have originated from common ancestor

- Describes the history of species, gene families, tumors, cell lineages, languages and DNA sequences

- Each branch point (node) is division of ancestral lineage

- Humans and great apes are cousins (we did not descend from apes)

- Phenotypic similarity is not the same as phylogenetic similarity

- Example: Crocodiles and birds share a more recent ancestor but look very different as birds underwent more evolutionary changes than crocodiles

- Demonstrates which tree of phylogeny is the likeliest

- Tree that takes the fewest evolutionary changes is the most likeliest

- Joining of separate lineages into one e.g. hybridization -> genes have moved horizontally between organsims