Environmental Science / Unit 4: Populations
4.4 Reproductive Strategies
Notes
Species have different life-history strategies.
| Trait | r-strategist | K-strategist |
|---|---|---|
| Offspring | Many, small | Few, large |
| Parental care | Little or none | Extensive |
| Maturity | Early | Late |
| Lifespan | Short | Long |
| Environment | Unstable, disturbed | Stable, near carrying capacity |
| Examples | Insects, weeds, bacteria | Elephants, whales, humans |
- Survivorship curves show how death rates change with age. Type I (humans) has most deaths late in life; Type III (oysters, many fish) has most deaths very young.
- K-strategists are more vulnerable to extinction because they reproduce slowly.
- Example: a dandelion that makes thousands of seeds with no parental care is an r-strategist.
Practice
Which organism is most likely an r-strategist?
r-strategists produce many offspring with little care.
Why are K-strategists more vulnerable to rapid habitat loss?
Slow reproduction means a lost population takes a long time to rebuild.
Most oysters die as larvae, but the survivors live a long time. Their survivorship pattern is Type III. This pattern fits which strategy?
Many offspring with little care and high early death is typical of r-strategists.
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