Life History #7: Life History Strategies, Trade-Offs

Question 1

Life History

Answer 1

Life History: Consists of major events related to organisms’ development, growth, reproduction, and survival

Question 2

Life History Strategy

Answer 2

Life History Strategy: Pattern in timing and nature of history events averaged across all individuals in species

Example:
- When to metamorphose (direct development)?
- How fast to grow?
- How large to grow?
- When to begin reproducing?
- How many offspring, and of what size?
- Whether to care for offspring?
- How often to breed?
- How long to live?

Note: Mode of Reproduction (sexual/asexual) = Basic Life History trait
- Sexual reproduction very costly, but can “keep ahead” to avoid pathogens rather than being killed off due to being genetic identical

Question 3

Life History Trade-Offs: Offspring Number vs Offspring Survival

Answer 3

Offspring Number vs Offspring Survival:
- Clutches w/ fewer eggs = all/most young birds survive fledging
- Clutches w/ more eggs = fledging survival chance were poorer

Question 4

Life History Trade-Offs: Offspring Number vs Offspring Size

Answer 4

Offspring Number vs Offspring Size:
- Plant species producing lot seeds tend to produce small seeds
- Plant species producing few seeds tend to produce large seeds

Question 5

Life History Trade-Offs: Offspring Number vs Parental Survival/Growth

Answer 5

Offspring Number vs Parental Survival/Growth
- Producing more cones = slower tree growth = less growth rings

Question 6

Indirect Development: Complex Life Cycles

Answer 6

Indirect Development:
- Take advantage of resources in other habitats
- Avoid immediately competing with adults of own species
- Good for dispersal

Complex Life Cycles: 2 distinct life stages

Question 7

Direct Development: One Life Stage

Answer 7

Direct development:
- Avoid predators in other habitats
- Already in place that your species can survive in
- Avoid “washing away”