Life history Flashcards
Life history is the … of an organisms life, including birth, …, … and death
maturation, reproduction
Life history includes: 1. ... and ... at maturity 2. ... and ... of offspring 3 ... allocation to reproduction 4. ... of growth and development 5. ... patterns 6. number of ... events 7. Lifespan and ...
- age, size
- number, size
- energy
- timing
- dispersal
- reproduction
- ageing
There is huge … in approaches to life histories across the tree of life
variety
Selection acts to maximise the … … … of organisms
lifetime reproductive success
- produces very different effects in different organisms
In order to maximise LRS you’d ideally want:
- … development
- … maturity
- high … investment
- high … rate
- long …
Why not maximise all of these?
fast, rapid, parental, reproduction, life
reproduction is costly, requiring resources and time - trade-off between different methods of maximisation - different species selected for different methods
Give e.g. of two organisms with very different life history strategies to maximise LRS
Brown rat - fast development and maturity (2 weeks), high reproductive rate (5 litters of up to 14 individuals/year) but low parental investment (95% die within year) and a short life (3 years max)
African elephant - slow development and delayed maturity (20 years) with a low reproductive rate (1 calf/ 2.5 to 9 years), but high parental investment and a long life (up to 70 years)
What decides life history strategy?
Intrinsic factors: e.g. energy/resource constraints, genetic constraints, phylogenetic constraints, mechanical constraints, physiological constraints (e.g. silkmoth adults don’t have mouthparts so rely on resources and nutrition from larval stage)
Extrinsic factors: e.g. ecological factors (predation, mate availability etc.) and climatic constraints
What is senescence?
age-related deterioration of an organism leading to a decline in reproduction and probability of survival
Why does senescence occur (from an evolutionary perspective)? what are the main theories?
- Mutation accumulation
- Antagonistic pleiotropy
- Disposable soma
Selection is most effective for life strategies with … … …
high reproductive rate
(e.g. if an organism is too old to reproduce effectively or at all anymore it won’t pass on any genes to offspring so selection won’t be acting strongly at all anyway)
Mutation accumulation hypothesis for senescence - mutations that are … later in life are more likely to be maintained in the population (selected against far less than mutations that are deleterious earlier in life). These are able to accumulate in the population
deleterious
e.g. huntington’s disease in humans (can reproduce before kicks in - doesn’t prevent this like earlier effect mutations)
Antagonistic pleiotropy - pleiotropic genes that effect more than one phenotypic trait can be … for one trait but … for the other, leading to a …-…. Again, selection acts more strongly towards traits that are positive … in life, even if they lead to more negative traits … in life, as it this doesn’t negatively effect LRS as much.
positive, negative, trade-off, earlier, later
- e.g. gene that causes overproduction of sex hormones (e.g. oestrogen and progesterone) - good for reproduction but can lead to cancer later in life
What is the disposable soma hypothesis?
- resources are finite - energy put towards one function (growth, maintenance, reproduction) is unavailable for others
- limit towards maintenance causes somatic damage (many different types) - if allocating it towards reproduction instead, for example
Overwhelming current view: all hypotheses are linked and we can’t … energy from function
decouple
What is the idea behind maturity?
- if you have time and energy to develop and grow then when you come to reproducing you will be a better parent and your offspring are more likely to survive and spread your genes - despite losing out on reproducing offspring while reaching maturity