What does life history mean?
Patter of investment into Growth, maintenance, and reproduction
- history of events during a life that are related to births and deaths
Energy captured could be converted into 3 different things:
- Growth
- Maintenance
- Reproduction
What is life history trait?
The events themselves or the rates that quantify the transition
- Specific ways organisms manage growth, maintenance, and reproduction to maximize lifetime reproductive success (fitness)
What are the two steps of survival?
- Survival to first breeding
- Chance of dying (survival)
What are the 2 steps of Growth?
- Size at first breeding
- Adult size
What are the 6 steps of reproduction?
- Juvenile
- Age at first breeding (α)
- Adult
- Reproduction (fecundity)
- Reproductive interval
- Lifespan
Give an example of life history
- offspring number and size
- growth rate
- size at maturity
- age at maturity
- offspring size and number
- parental care
- Number of breeding attempts
- Life span (dead)
Name some reasons why life history traits are important and interesting
- Vary a lot among organisms
- Targets of strong selection (can evolve rapidly i.e. heritable variation)
- Directly affect population growth/dynamics
- Trade-offs
What is the purpose of a trade-off
Making a decision that is going to maximize your fitness
- does NOT tell you which is the best decision
What is quality v. quantity tradeoff?
Has to do with offspring size/quality and number of offspring you produce
- number of seeds produced per plant and the average seed mass (negative relationship)
- trade off on whether you choose to have very small seeds and overwhelming the environment with your seeds, to put more out there than your predators could eat ORRRR having just a few seeds making them really well provisioned (plant version of parental care)
Explain the trade-off in lizards?
- Variation in number of eggs per nest in lizards
- Depending on where the lizard is located, that will impact the number of eggs and the mean egg size
What does life history strategy mean?
How you allocate energy
Explain the quality-quantity trade-off in human hunter-gatherers
Higher fertility –> lower offspring size at age 5; Lower fertility –> higher offspring size at age 5
Explain the experiment on the Lesser Black-backed Gull
- Ruedi Nager removed each egg from the nest of this gull
- When he did this, he can get females to lay more eggs than she normally would (if you took an egg away from her)
- He could make different females lay normal number or increase number of eggs
- Then he had a different female foster the clutch of eggs that were laid
- Observed probability that chicks from those eggs survived to independence
He did this experiment with multiple different females to get a range of different clutch sizes and had them mothered by different mothers
Explain the experimental evidence from the Black-backed gull
When you had fewer eggs laid, fewer offspring died
- isn’t due to the mom NOT actually taking care of the eggs properly
- seems to be a trade off that the more eggs the bird was forced to lay, the lower quality the eggs were i.e. lower survival
What is survival vs. reproduction trade off?
Maybe you delay reproducing in order to survive longer
What is growth rate vs. reproduction trade off?
Maybe you are in a situation that you need to grow fast and reproduce earlier (or vice versa)
How do Semalparous organisms allocate their energy?
- These grow to a certain size, then put all of their effort into reproducing and then they die
- Marsupial mouse males do this, they will go into reproductive mode and mate with as many females as they can and die due to not eating
How do Lupin plants compared to Tree lupin plants allocate their energy?
Lupin: (annual plants) live only one year, and put their energy into survival and giving it into reproduction (26% of energy goes into seeds)
Tree Lupins: (perennial plants) live multiple years; puts more of their energy in maintenance and less into reproduction (7% of energy goes to seeds)
Explain reproduction vs. survival trade-off in birds
Albatrosses
- Lifespan > 50 years
- Start breeding late
- Lay 1 egg per nest
- Usually don’t reproduce in consecutive years
Sparrows
- Lifespan = 3 years
- start breeding at 1
- Lay 4-7 eggs per nest
- Reproduce every year
Negative correlation between number of eggs produced each year vs. probability of survival
Name some essential features of life history trade-offs
- Negative correlation between traits (paying the price)
- Constraint on energy, space, time, money (example with the beer the constraint was money)
- Trade-offs don’t tell you the right strategy
- E= growth + storage + maintenance + reproduction
- Competing positive ends
- Quantitative traits with variation across environments
E= S + G + M + R, but what does R equal?
R = NC (quality-quantity trade off equation)
- ‘N’umber of offspring
-‘C’ost per offspring (size)
Explain the experiment with Drosophila Melanogaster flies
- Linda Partridge kept male fruit flies with mated OR virgin females
- Previously mated females are less interested in interacting with males
- Males do not spend as much time courting previously mated females
- Males with mated females: had longer life span in direct relationship with body size
Explain the experiment with seed cones
Measured the thickness of growth rings of trees
- If you have a smaller growth ring it means you’re growing faster (vise-versa); what this shows is that fast growing plants had MORE number of cones per tree compared to those who grew slower
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