Week 6 Flashcards
Who was the person to propose the evolutionary concept of the life cycle?
John Bonner
How is evolution involved in changing life history?
Alters life cycles through time
How are genetics involved in changing life history?
Inheritance of mechanisms between life cycles - how you inherit a particular life cycle
How is development involved in changing life history?
Cause changes in structure which may happen during one life cycle
(1) is the central unit to biology
Life cycle
What are the 2 pillars of life history theory
- Resources (and therefore energy) need to be obtained and divided amongst competing tissues
- The optimal pattern of what you spend energy on changes in your lifespan (e.g. don’t devote energy to reproduction in childhood)
Give some examples of ways we can measure investment in a particular function
Birth weight, age at sexual maturity, lifespan, litter size, adult body size
Which are the 4 main biological functions which compete for energy?
Growth
Reproduction
Defense (immune system, guarding)
Maintenance (implicated in chronic disease!)
Describe how maintenance is involved in chronic disease
Maintenance is the least important of the 4 biological necessities, when the body’s energy reserves are limited (e.g. when undernourished) maintenance will be sacrificed at the expense of something else, may lead to chronic disease
The body’s only overall goal is to reproduce
When are fast life histories an optimal strategy?
Disease/predation (mortality) high
Fast life strategies are called (R/K)
R-strategy
Slow life strategies are called (R/K)
K
When the environment is unpredictable, it might be beneficial to be (R/K selected)
R-selected
When the environment is stable, it might be beneficial to be (R/K selected)
K-selected
Describe the investment in reproduction in R-strategy species
Environment unpredictable: pump out babies
Describe the investment in reproduction in K-strategy species
Invest in one or two quality offspring, might hold off on having them depending on environment
Why aren’t rabbits big?
They don’t invest much energy in growth, doesn’t make sense to grow bigger
A large animal is more likely to be (R/K strategy)
K strategy
Which of the 4 biological investment areas when highly invested in tends to give long, healthy lifespan
Maintenance
When environmental mortality is high, maintenance is inversely proportional to…
Reproductive rate
What is a key determinant on lifespan length?
Mortality risk
Describe the example with the guppies in Trinidad
2 groups of the same species of guppies geographically isolated by a waterfall: Above waterfall (upstream) = safer, downstream = less safe
Upstream guppies grow slower and breed later
Downstream guppies grow faster and breed earlier
Transplant downstream guppies upstream: Slower life history emerges
Transplant predators upstream: Faster life history emerges
The example of life history in the guppies demonstrates that…
Life history can exhibit plasticity - life history can evolve
Describe the evolutionary strategy behind compensatory/catch up growth
“Grow now pay later” - a short-term strategy for survival, it is beneficial in a high-mortality environment
Which of the 4 biological spending areas gets priority over all others when it is being highly invested in?
Immune defense: if not you die
How does living in a high disease risk area affect growth?
If immune system is running: so expensive, taking away energy for growth: capacity is lower in early life (if affected at that time), etc.
When is an example of a time when it is not beneficial to turn on immune function?
While pregnant: pregnancy requires SO much energy – increases risk of disease!
As a fetus grows inside a mother, how does her risk for malaria change?
Increases as the baby ages: mother’s risk peaks during lactation
Why might giving vitamins to a malnourished group of people not make them better?
Depending on what their circumstances are, that energy might go to different functions, like reproduction or immunity: may remain malnourished