Body of theory that examines
- How different life cycles evolved via natural selection and sexual selection
- How variation in life events affect fitness
First concerned with the Timing of events in the life course that will affect fitness
- sexual maturity
- Marriage
- Births of offspring
- End of reproduction
- Death
Principles of allocation
- states that energy used for on function cannot be used for another
- Energy has to be spend to produce an outcome
- Growth
- Maintenance
- Reproduction
Growth
- body growth
- Brain growth
- Learning
- Reproductive maturation
Reproduction
- Mating
- Competition
- Pregnancy
- Lactation
- Parental care
Maintenance
- Immune function
- Stress responses
- Cellular repair
- Antioxidant
- Vigilance
Allocation tradeoffs
- orgasms usually finish growing up before they begin reproducing
- species with complicated digestive systems tend to have small brains and vice versa
- sick and undernourished induviduls are often less fertile
Principle of Allocation
- It is important to remember that, for every unit of time that passes, there is less and less chance of being alive.
- Thus, time , in addition to energy is limiting resource for life history decisions
Life history tradeoffs
- Offspring quality versus quantity
- Current versus future reproduction
- Mating effort versus parenting effort
Offspring quality versus quantity
- Parental investment (resources, time) is limited
- When higher fertility yields higher potential RS, id reduces the an=mount of investment available for each offspring
- Affects survival/success of offspring
Current versus future reproduction
- Reproduce now of reproduce later? Are conditions now favarable to success? Or is it better to wait and not squanerd resources?
- Invest in existing offspring or now offspring? When do you stop (or reduce) investing in one offspring and start investing in another?
Inerbirth intervsl
- time between successive births
- if offspring are born very far a part, the mother’s total fertility will be low
- If offspring are born too close together, the compete for resources
~ for humans about 24-35 months after the first child and 24-35 after each child - Average birth intervals are usually close to the optimal balance of speedy reproduction and offspring survival
Mating effort versus parenting effors
- A tradeoff for males
- Time and energy spent to try to attract and compete for new mates cannot be spent on caring for existing offspring
- A male who spends all his efforts to gain new mates will possibly conceive many offspring
- But, a male who invests in a parenting may have more that survive
- Male investment is often related to need,. Males are most likely to invest when it does the most good Or When it is unlikely they can find other mates.
Optimal balance of these trade offs differs
- Between species
- Between individual
- Within individuals at different times of their lives
Optimal balance of these trade offs differs
- Between species
- Between individual
- Within individuals at different times of their lives
Fast life history strategies emphasize producing many offspring very quickly
- low investment in growth ~ Smaller body size and brains ~ Early maturation - low investment in maintenance ~ Short lifespan - Prioritize current reproduction and offspring quantity ~ Fast reproduction rates ~ Large litters ~ Small offspring ~ low investment per offspring
Slow life history strategies emphasize investment in growth and survival
- high investment in growth ~ Larger body size and brain ~ Late maturation - High investment in maintenance ~ Long lifespan - Investment in offspring quality ~ Slow reproductive rate ~ Small litters ~ Large offspring ~ Large investment per offspring
Two life history traits are critical in driving the rest
- Body size
- Extrinsic mortality
What are the advantages of being a large anaimla?
- Fewer animals can prey on you
- You can access more different foods
- Large digestive systems
- Can also produce larger offspring which are less vulnerable to predators
- Efficiency- larger bodies cost less per unit mass
Why are there so many species that are small?
- Important niches for small species
- Can subsist on simple diets
- It takes a long time to grow up… must have a high chance to making it
- Energy spent on growth can’t be spent on reproduction
Allometry
Correlations of traits to body size
Species with high levels of extrinsic mortality
- cannot afford to spend a long time growing up
- Will be unlikely to live a long time
- Should overproduce offspring to ensure the survival of some
Higher reproductive success
Even in species which are selected to have low reproductive rates (“slow” life history), individuals in better condition may be able to produce more offspring
We observe in nature is a result of:
- Species-typical life history pattern
- Individual differences in quality
- Individual differences in strategy
