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
Describe the investment in offspring as number of offspring increases
When there are more offspring, each one receives less care
Describe the lifespan of humans with more kids
They tend to not live as long
Describe the biology of sibling rivalries
You are only share 50% of your genes with your sibling: will compete with them for attention (investment) from parents
What does hPL do? (3)
Where is it secreted?
Human placental lactogen - secreted by placenta
Increases maternal blood glucose
reduces maternal glucose usage
increases maternal lipolysis (using energy from fatty acids)
Describe the effect of hPL on the pancreas
A healthy pancreas can withstand hPL, but a compromised one (like one which was poorly set up during hyperplasic growth) may be less equipped to deal with it: can lead to gestational diabetes
If hPL is being secreted in large amounts, what happens to the fetus?
Fetus might grow too large: difficulty coming out leading to decreased capacity: increased risk for obesity
The body’s “savings account” is…
Adipose tissue
Why don’t all animals have a “savings account” in the form of fat?
E.g. birds, would have to fly around with extra weight, spend more energy than the fat is worth
What are income and capitol breeders?
Income: eat to pay for reproduction
Capitol: acquire surplus energy before reproduction to pay for it
What is the primary cellular switch for deciding where energy gets invested?
Insulin! Cells can alter their sensitivity to insulin
What organ is referred to as our “risk management organ”
2: brain and fat!
Adipose tissue is a powerful solution to… (4)
- Buffering stochasticity in energy supply
- Buffering brain growth
- Thermoregulation
- Immune function
Which kinds of birds tend to pack on fat?
Migratory birds: need to have energy for migration!
Why is it very important for bears to put on fat in the fall?
Go into hibernation: females will give birth and lactate during hibernation: so need TONS of energy for this
Typically, other than humans, mammals with large brains will have (a little/a lot of) adipose tissue
A little
How does adipose tissue provide energy for life history functions? (2)
- Signalling pathways about energy availability and requirements (leptin)
- involved in allocating energy between functions (responds to signals for tissues which require energy, releasing triglycerides to specific locations)
Adipose tissue secretes these 3 things which determine where energy goes in the body
Pro-inflammatory cytokines
Anti-inflammatory cytokines
Growth factors
Which hormone secreted by adipose tissue makes the tissues more sensitive to insulin?
Adiponectin
Where are receptors for adiponectin?
Ovaries, testes, endometrium
Adiponectin causes the allocation of energy towards this function
Reproduction
Which of the 2 human risk-management systems is best for buffering short-term stress?
Brain: fight or flight
Which of the 2 human risk-management systems is best for buffering long-term stress?
Adipose: energy store
Why is adipose tissue considered to be a “second brain”?
Adipose tissue signals to brain to get it to secrete hormones: act in conjunction with the brain to steer life history
What is neural peptide Y (NPY)?
Plays a role in stimulating appetite
During what stage of development do humans start depositing body fat? When do most mammals start depositing fat?
The third trimester
After birth
How much of a human baby’s body is body fat?
15%
Why do humans have high adiposity at birth? (2)
- To buffer the heightened energy needs of the brain at this age
- This is also the time we are most sensitive to the environment: need energy stores for growth and immune function
Visceral fat is usually bad, but is helpful for…
Running immune system: releases cytokines
Describe the characteristic body fat pattern involved in HIV/AIDS
Body tends to redistribute subcutaneous fat and place it viscerally
Describe the different thermoregulation properties for White adipose tissue (WAT) and brown adipose tissue (BAT)
WAT: Thicker layer of subcutaneous fat = better insulative layer
BAT: heat-generating fat: convert food energy directly into heat
Which kinds of fat are WAT?
Visceral and subcutaneous
What kinds of fat are BAT?
It’s its own specialized kind of heat-producing fat cell
Why do infants have more BAT than adults?
Infant humans can’t shiver: need BAT to keep them warm
Brown adipose tissue is packed with this kind of organelle
Mitochondria
What is special about the mitochondria of BAT cells?
Have uncoupling proteins which disrupt the ETC and result in the release of energy from the chain as heat
Why is brown fat brown-coloured?
Packed with mitochondria
How does BAT play a role in preventing obesity?
So energetically expensive, lowers blood glucose levels
What effect on obesity did transplanting BAT in mice have?
Mice were less obese
In what order did the following evolve: UCPs (uncoupling proteins), WAT, adipocytes, BAT
Adipocytes (fat stored in organs) > WAT (fat becomes an organ) > UCPs > BAT (evolved to take advantage of UCPs)
Which hormone appears evolutionarily at the same time as WAT?
Leptin
Which kinds of animals have BAT?
Only mammals
The strongest selection pressure for altering life history is…
A lack of clear ecological signals: volatile environment – lack of something to adapt to, which is why we have a double risk management system
Why might women be more evolutionarily adapted to extreme long-distance running?
Are better able to access fat energy stores due to estrogen: estrogen promotes the storage of glucose and lipolysis of fatty acids
How do humans deviate from the ape pattern of life history? (3)
Extended maturation
Extreme longevity and short inter-birth intervals
Large brains and high adipose tissue
