Reproductive Value and Life History Theory Flashcards
What is the Darwinian Demon
A hypothetical organism that maximises all aspects of fitness (reproduces early, lives long, has many high-quality offspring) - but it doesn’t exist because of trade-offs in real life
What is Life History Theory
The study of how traits evolve to influence fitness at different life stages, helping explain the diversity of life strategies
What is an altricial species
An organism born underdeveloped and dependent on parents - e.g. kangaroo joey
What is a precocial species
An organism born relatively mature and independent - e.g. Ugandan kob
What is determinate growth
Growth that stops at maturity
What is indeterminate growth
Growth that continues throughout life
Describe the “Sit and Wait” growth strategy
Slow, opportunistic growth; waits for resources (e.g. some desert plants)
Describe the “Climb and Climb” strategy
Rapid vertical growth to capture light, without much investment in support (e.g. vines)
What does “mature in utero” mean
Giving birth to already pregnant young
What is semelparity (senaberous)
Reproducing once before death
What’s an example of producing only one large offspring
Kiwi bird - lays a very large single egg
What environmental factor can influence the sex ratio in some species?
Temperature during critical periods of embryonic development
What does ‘lifespan’ refer to in life history theory
The total duration of an organism’s life, from birth to death
Why is lifespan an important life history trait
Because it affects how resources are allocated over time between growth, reproduction, and survival, influencing fitness
What trade-offs are associated with a short lifespan
Often associated with early reproduction and high offspring number, but low parental investment
What trade-offs are associated with a long lifespan
Typically includes delayed reproduction, fewer offspring, and greater investment in survival and parental care
How is average lifetime reproductive success calculated
Sum of l × m across all age classes
(l = survivorship, m = fecundity)
What does R₀ represent in population ecology
Net reproductive rate: average number of female offspring per female over her lifetime.
What does
R₀ = 1
R₀ > 1
R₀ < 1
mean
R₀ = 1 → stable population
R₀ > 1 → growing
R₀ < 1 → declining
What is Reproductive value (Rv)
The expected future contribution of an individual to future generations, based on its age
Why do older offspring typically have higher Rv than newborns
They are closer to reproduction, so parents are selected to value them more
What does high average Rv in newborns imply
Likely evolution of parental care - investment in young increases survival
How does natural selection relate to deleterious mutations and age
Selection is strongest when Rv is high (early life) → fewer harmful mutations expressed then
How can evolutionary theory explain menopause
After Rv = 0, women can still contribute through grandmothering, increasing integrative fitness
