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

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

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

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

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

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

Life histories and survivorship

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

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

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

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)

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)

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

Midterm Review Benjamin Bloom, 1956

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.

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)

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)

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

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)

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

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

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

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

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?

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.