Podcast
Questions and Answers
What is the primary factor that influences when Daphnia enter diapause in Michigan?
What is the primary factor that influences when Daphnia enter diapause in Michigan?
Which of the following best describes 'central place foraging'?
Which of the following best describes 'central place foraging'?
Which of the following statements about risk-sensitive foraging is true?
Which of the following statements about risk-sensitive foraging is true?
What role do ultimate factors play in the response of organisms to environmental changes?
What role do ultimate factors play in the response of organisms to environmental changes?
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How does predation affect the maturity of mayflies?
How does predation affect the maturity of mayflies?
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What does the term 'life history' refer to in an evolutionary context?
What does the term 'life history' refer to in an evolutionary context?
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Which of the following components is NOT included in life history?
Which of the following components is NOT included in life history?
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How is the number of eggs in a clutch size correlated with environmental factors?
How is the number of eggs in a clutch size correlated with environmental factors?
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Which of the following statements best describes the relationship between survivorship and fecundity?
Which of the following statements best describes the relationship between survivorship and fecundity?
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What is one primary trade-off organisms must face regarding reproduction?
What is one primary trade-off organisms must face regarding reproduction?
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What is the average number of offspring produced annually, according to the content?
What is the average number of offspring produced annually, according to the content?
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In terms of life histories, which group of organisms is likely to exhibit fast life histories?
In terms of life histories, which group of organisms is likely to exhibit fast life histories?
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Which factor is considered when determining the best age for reproduction from an evolutionary perspective?
Which factor is considered when determining the best age for reproduction from an evolutionary perspective?
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What does natural selection favor in terms of reproductive age?
What does natural selection favor in terms of reproductive age?
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What is the primary trade-off when life span is short and few offspring survive?
What is the primary trade-off when life span is short and few offspring survive?
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Which reproductive strategy is characterized by organisms that reproduce once and die?
Which reproductive strategy is characterized by organisms that reproduce once and die?
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In what scenario is semelparity sometimes favored?
In what scenario is semelparity sometimes favored?
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What is the term for a decline in function with age across all animals?
What is the term for a decline in function with age across all animals?
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Which of the following is an example of dormancy in animals?
Which of the following is an example of dormancy in animals?
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What is often the response of life histories to environments with high survival rates?
What is often the response of life histories to environments with high survival rates?
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Internal and external storage in animals is a response subject to which process?
Internal and external storage in animals is a response subject to which process?
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Study Notes
Life Histories and Evolutionary Fitness
- Individuals exist to produce many successful offspring.
- Life history is the pattern of a species' development, growth, life span, and reproduction.
- Life histories are adapted to the environment and are subject to natural selection.
- Key components of life history include age at maturity, parity (number of times an organism reproduces), fecundity (number of offspring per reproductive episode), and longevity (life span).
- Clutch size (number of eggs) is correlated with hours of light available for food gathering.
- Life histories vary along a continuum from slow to fast.
- Relationships are observed between survival and fecundity.
- Survivorship curves illustrate patterns of survival over a lifetime.
- Trade-offs exist between current and future reproduction.
- Primary trade-offs organisms face: age at first reproduction, fecundity and survival, growth (of parents) and fecundity.
- Natural selection favors the age that results in the greatest offspring production over the life of the animal.
- Many organisms exhibit determinate growth. The longer they delay sexual maturity, the greater their fecundity.
- Trade-offs exist between fecundity and survival (fecundity curve levels off due to diminishing returns on investment)
- When life span is long and offspring survival is high, adult survival is favored over fecundity.
- When life span is short and offspring survival is low, fecundity is favored over survival.
- Trade-offs exist between growth and fecundity.
- Long-lived species show a preference for growth over fecundity. Short-lived species prefer fecundity over growth.
- Examples like hypothetical fish species with different life history strategies are given; data such as body weight, growth increment, weight of eggs, cumulative weight of eggs show this graphically.
- Individuals may reach maturity at a specific age, mass, or somewhere between those markers.
- Predation may influence time to maturity (e.g., mayflies and trout presence).
- Animals forage to maximize fitness through central place foraging.
- European starlings and leatherjackets maximize fitness when foraging from a central place. Starling mealworm experiments show that starlings bring larger loads of food when food sources are farther away.
- Risk-sensitive foraging is also a factor related to maximizing fitness.
- Reward must be worth the risk. The creek chub experiment showcased this.
- Semelparity – organisms reproduce once and die (e.g., plants in harsh habitats, or when reproduction is extremely costly).
- Iteroparity – organisms reproduce repeatedly.
- Periodical cicadas are an example.
- Senescence - decline in function with advancing age; happens in all animals, but rates vary.
- Life histories respond to the environment.
- Organisms store food and build reserves for adverse conditions (e.g., cacti store water, chaparral plants have fire resistant root crowns).
- Dormancy is an inactive state that allows organisms to survive temporarily inhospitable environments (e.g., hibernation to avoid winter food scarcity, diapause to avoid winter freezing/summer dessication, Aestivation).
- Proximate and ultimate factors influence environmental change.
- Responses to environmental stimuli differ by location (e.g., Daphnia diapause).
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