1. How organisms grow and produce offspring
Life Histories
How organisms grow and produce offspring

2. Life History
The schedule of an individual’s life: age at maturity, number of offspring, life span
Ultimately, all the processes that contribute to the reproductive output of an individual
Life history traits evolve in populations

3. Life histories and the principle of allocation
All organisms take in energy at a limited rate
Trade-offs in the allocation of resources provide a basis for understanding life histories

4. Life histories and the principle of allocation
Trade-off between number and size of offspring:
organisms that produce many offspring must produce smaller offspring
organisms that produce large offspring can only produce a limited number

5. Life histories and survivorship
Also a trade-off between reproductive effort and survival:
More energy allocated to reproduction means less energy available for growth and maintenance
Delayed reproduction increases the risk of dying before reproduction occurs
Adult mortality rates in populations influence the age at which individuals first reproduce

6. Life histories and survivorship
Populations with high adult survival rates should have individuals that delay reproductive maturity and allocate a smaller proportion of their total energy to reproduction
Populations with high adult mortality should have individuals that reproduce earlier and allocate a higher proportion of their energy to reproductive effort

7. Life histories and survivorship

8. Variation in life histories
Life history strategies can be organized along a continuum from fast to slow:
r-selected species – life history dominated by intrinsic rate of increase: reach maturity quickly, high fecundity - produce many small offspring
K-selected species – life history affected more by resources & competitive advantage: mature later or at a larger size, produce fewer, larger offspring

9. Variation in life histories
r-selected species – expected to occur in variable or unpredictable environments; Type III survivorship
K-selected species – expected to occur in more stable environments; Type I or II survivorship

10. Plant life histories
Two main environmental variables that dictate plant life history traits (J.P. Grime, 1979):
Disturbance
Stress
Increasing
disturbance
Increasing
stress

11. Plant life histories – Grimes “CSR” model
Ruderals
(Disturbance-
Tolerant
Organisms)
Increasing
Disturbance
(more disturbed
habitats)
Competitive
organisms
Stress-tolerant
organisms
Increasing stress
(more severe habitats)

12. Plant life histories – CSR model
High Disturbance, Low Stress: Ruderal plants
Grow quickly, reproduce rapidly, produce large numbers of seeds
Low Disturbance, High Stress: Stress Tolerant plants
Grow slowly, conserve resources for periodic reproduction when conditions are favorable; low competition
Low Disturbance, Low Stress: Competitive plants
Can grow quickly, but eventually will compete for resources; life history will maximize competitive advantage (e.g., later maturity; large size; fewer, larger offspring)

13. Correspondence between r – K and CSR life history classifications
ruderal plants tend to be r-selected species
competitors and stress tolerators tend to be K-selected species

14. Midterm Review
Benjamin Bloom, 1956

15. Midterm Review Bloom’s Taxonomy
1. Knowledge: arrange, define, duplicate, label, list, memorize, name, order, recognize, relate, recall, repeat, reproduce state.
2. Comprehension: classify, describe, discuss, explain, express, identify, indicate, locate, recognize, report, restate, review, select, translate,
3. Application: apply, choose, demonstrate, dramatize, employ, illustrate, interpret, operate, practice, schedule, sketch, solve, use, write.
4. Analysis: analyze, appraise, calculate, categorize, compare, contrast, criticize, differentiate, discriminate, distinguish, examine, experiment, question, test.
5. Synthesis: arrange, assemble, collect, compose, construct, create, design, develop, formulate, manage, organize, plan, prepare, propose, set up, write.
6. Evaluation: appraise, argue, assess, attach, choose compare, defend estimate, judge, predict, rate, core, select, support, value, evaluate.

16. Midterm Review
Biomes
Physical processes on earth that shape wind / weather patterns (water availability)
Relative energy availability in different areas of earth
Energy / water availability in different terrestrial biomes
Major aquatic biomes, and their main physical properties (light, nutrients, temp)

17. Midterm Review
Biomes
Physical processes on earth that shape wind / weather patterns (water availability)
Relative energy availability in different areas of earth
Energy / water availability in different terrestrial biomes
Major aquatic biomes, and their main physical properties (light, nutrients, temp)

18. Midterm Review Individual Temperature, Water and Energy Relations
Individual adaptations for limiting water loss, regulating heat gain/loss
Principle of Allocation, energy limitations and energetic trade-offs

19. Midterm Review Population Genetics
Allele frequencies and genotype frequencies
Hardy-Weinberg equilibrium: p2 + 2pq + q2 = 1
Processes that cause deviation from equilibrium (i.e., evolution)

20. Midterm Review Population Distribution and Abundance
Different types of distribution patterns of individuals in populations, and what causes these patterns to occur in nature.

21. Midterm Review Population Dynamics
Different types of distribution patterns of individuals in populations, and what causes these patterns to occur in nature.
Life tables, fecundity
Major variables associated with these calculations
Survivorship, Survivorship curves

22. Midterm Review Population Growth
Different patterns of population growth
Geometric, exponential, logistic
Major variables associated with these equations

23. Midterm Review Life Histories
Know major patterns in life history trade-offs
Size, number of offspring, age at maturity, adult survival, etc.
r- and K-selected life histories
Grimes’ plant life history categories

24. Midterm Review – Sample Practice Question
You are a gardener and you need to choose a species of tree to plant in your city park. You want a tree that will grow fairly quickly, reach a large size, and live for a long time. If you had to choose a tree from one of Grimes’ three plant life history categories, which do you think would be the most appropriate category to select from, and why?

25. Midterm Review – Sample Practice Question
You are a land manager who wishes to conserve several separate populations of trout lilies within a national wilderness area. There are many populations threatened by logging, but you are only allowed to focus your conservation efforts on four populations. If you are interested in maintaining the highest level of gene flow possible between the populations you save, should you choose populations that live in areas with or without deer (deer occasionally eat adult lilies)? Support your answer with what you’ve learned about life histories.