به انگلیسی

Spend now or save for later

Science · Ecology & Conservation · ages 20-22

Name ______________________ Date ____________

A survivorship curve records 20, 5, 4 and 4 survivors at ages 0, 1, 2 and 3. Where do most recorded deaths occur?
- Between ages 1 and 2
- Between ages 0 and 1
- Between ages 2 and 3
With energy intake held fixed, why can growth and reproduction trade off?
- Both draw on a limited budget, so allocating more to growth leaves less for reproduction
- Growth and reproduction have separate budgets that decline together as the animal ages
- Growth builds reserves for reproduction, so growing more provides energy for later broods
Which example illustrates semelparity?
- Songbirds that breed in several years but raise one brood in each year
- Mammals that breed repeatedly but raise one young during each episode
- Chinook salmon that spawn once and die before a later breeding season
An 18-unit reproductive budget is shared equally among young. What does each receive with six young, and with nine young?
- 3 units with six young; 2 units with nine young
- 6 units with six young; 9 units with nine young
- 2 units with six young; 3 units with nine young
Adult survival is low, and delaying breeding gives no increase in later offspring production. Which timing does this support?
- Delay breeding to avoid spending energy during the risky adult stage
- Breed earlier to reproduce before deaths remove another opportunity
- Keep the same timing because food intake, not survival, sets breeding age
A life table shows more deaths just after first breeding. No comparison group was studied. What can you conclude?
- The timing identifies breeding as the cause of the mortality increase
- The timing identifies ageing as the cause of the mortality increase
- The timing fits a reproductive cost but does not identify the cause
Individuals obtaining more food both grow more and reproduce more. This observation alone proves there is no allocation trade-off.
Circle one: True False
Two hypothetical broods use the same 24-unit budget: six young with survival probability 0.5 each, or twelve with probability 0.2 each. Which pair of expected survivor counts is correct?
- Six young: 0.5; twelve young: 0.2
- Six young: 3.0; twelve young: 2.4
- Six young: 3.0; twelve young: 6.0

Answer key

For grown-ups. Fold this page away before handing over the rest.

Spend now or save for later W1-mt_eGwlydfDWO-s1

Between ages 0 and 1 · The losses are 20 - 5 = 15, 5 - 4 = 1 and 4 - 4 = 0. Most recorded deaths occur between ages 0 and 1.
Both draw on a limited budget, so allocating more to growth leaves less for reproduction · Both functions draw on the same limited supply. With intake fixed, allocating more energy to growth leaves less for reproduction.
Chinook salmon that spawn once and die before a later breeding season · Chinook salmon have one spawning episode and then die. Semelparity describes one lifetime reproductive episode, not a particular brood size.
3 units with six young; 2 units with nine young · 18 / 6 = 3 units each, while 18 / 9 = 2 units each. More young receive less each when the total budget is fixed.
Breed earlier to reproduce before deaths remove another opportunity · Waiting risks death before breeding. The prompt rules out an increase in later offspring production that could compensate for that risk.
The timing fits a reproductive cost but does not identify the cause · The pattern is consistent with a reproductive cost. Age, disease or seasonal conditions could also explain it, so timing alone does not establish causation.
False · Greater resource acquisition can support both outcomes. An allocation trade-off can still exist when a fixed resource supply is divided.
Six young: 3.0; twelve young: 2.4 · Six young give 6 x 0.5 = 3 expected survivors. Twelve give 12 x 0.2 = 2.4. Under the stated comparison, the six-young brood does better.