Life Histories (DONE) Flashcards
This is the main deck of flashcards for this topic
What are life histories?
Life histories are the patterns of growth, reproduction & survival an organism undergoes in its lifetime
Influenced by genetics, environment & survival
What are the 3 main components of life histories?
- Growth
- Reproduction
- Survival
How do guppies & whale sharks differ from cod in reproduction?
Guppies & whale sharks give birth to live young, while cod lay millions of eggs
What is r-selection?
A strategy where species “live fast, die young”, reproducing quickly in unstable environments
What is K-selection?
A strategy focussing on competition & slower growth in stable environments
What trade-offs do organisms face in resource allocation?
Between:
- Current & future reproduction
- Growth & reproduction
- Reproduction & survival
Define semelparity:
A reproductive strategy where organisms reproduce once & then die
e.g. salmon
Define iteroparity:
A reproductive strategy where organisms reproduce multiple times throughout their life
e.g. humans
How do high-predation environments affect guppies’ life histories?
They mature faster & reproduce earlier to reduce time at risk or predation
What is senescence?
The process of ageing, marked by declining reproductive success & survival with age
What is mutation accumulation?
The build-up of harmful mutations that manifest later in life when natural selection is less effective
What is antagonistic pleiotropy?
When genes beneficial early in life have detrimental effects later in life
What constraints limit life history evolution?
Phylogenetic, biomechanical & developmental constraints
What does the reproductive value curve represent?
The expected number of offspring an individual will have over the rest of their life
What is the Darwinian Demon?
It is a hypothetical organism that starts reproducing immediately after birth - produces an infinite no. offspring & lives forever
Represents the theoretical “perfect” outcome of evolution - cannot exist tho
Why don’t organisms reach the “Darwinian Demon” ideal?
Bc they cannot reproduce from birth & face trade offs between growth & reproduction
How does condition affect life history strategies?
Variation in resources & environment leads to differences in growth, reproduction & survival
How do semelparous plants allocate energy compared to iteroparous plants?
Semelparous plants = invest more energy in a single reproductive event
Interoparous plants = spread investment over time
What is Cole’s Paradox?
The question of why all organisms aren’t semelparous since producing one extra offspring seems advantageous
What was observed in song sparrows regarding trade-offs?
Predicted trade-offs between reproduction & survival were not always supported
How does extrinsic mortality affect senescence?
Higher external mortality leads to faster ageing since investing in future reproduction becomes less advantageous
How do r- and K- strategists differ in unstable vs stable environments?
r- strategists thrive in unstable environments w rapid reproduction
K- strategists excel in stable environments w competition
What example illustrate extreme senescence in vertabrates?
The Greenland shark –> can live over 400 years
What study used anoles to demonstrate reproductive trade-offs?
An experiment showed that stopping reproduction allows greater growth & survival
How do iteroparous species balance survival & reproduction?
By reproducing less intensely to maintain survival over multiple reproductive events
How do phylogenetic constraints impact life histories?
Evolutionary history limits how much traits can adapt, such as mammals not reverting to fish
What is the disposable soma theory?
The idea that organisms prioritise early reproduction, reducing long-term maintenance & survival
What role does condition-dependent mortality play in life histories?
It shows that individuals in better condition can offset senescence & live longer
What did Ricklefs (1998) observe about mortality in zoos?
Even in protected environments, senescence causes inc mortality late in life
What trade offs were seen in high-predation guppy population?
High-predation fish reproduced earlier but continued reproducing longer than low-predation fish
What is a key takeaway about life history trade-offs?
No strategy is perfect; all involve compromises between growth, reproduction & survival
