Biology Chapter on Reproductive Strategies

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Questions and Answers

What is a trade-off that organisms face in reproduction?

Increasing reproductive success at the expense of vulnerability to predators. (correct)

Ensuring high survival rates without compromising reproduction.

Maintaining constant fitness across all genotypes.

Maximizing all life-history traits simultaneously.

What does natural selection favor in terms of life histories?

Genotypes that prioritize predator avoidance over reproduction.

Genotypes where survival and fecundity lead to the highest relative fitness. (correct)

Genotypes that feature the highest reproductive rates regardless of survival.

Genotypes with maximum growth rates only.

Which statement accurately characterizes r-strategy organisms?

They exhibit slow growth and extended parental care.

They emphasize rapid reproduction and growth rates. (correct)

They prioritize stable maximum resource use.

They have lower reproductive rates with higher survival probabilities.

Which of the following is a characteristic of K-selection?

Greater investment in quality and survival of fewer offspring. Signup and view all the answers

Why is it difficult for organisms to maximize fitness?

Due to limitations on resources, leading to trade-offs between traits. Signup and view all the answers

What characterizes a fast life history strategy?

High fecundity and short lifespan Signup and view all the answers

How do male Chinook Salmon differ in their life strategies?

They can be large hooknose males or small jacks. Signup and view all the answers

In what way do 'sneaker' males differ from more traditional male strategies?

They avoid competition by sneaking to fertilize eggs. Signup and view all the answers

What role does frequency-dependent selection play in alternative strategies?

It can maintain multiple reproductive strategies within a population. Signup and view all the answers

What is the usual outcome of intensive harvesting on species with alternative life histories?

Genetic changes that result in smaller sizes at maturity. Signup and view all the answers

Which of these statements about sexually dimorphic species is true?

Competition for resources often occurs among males. Signup and view all the answers

What leads to a decline in body size among bighorn sheep populations?

Selective hunting of males with large horns. Signup and view all the answers

What can trigger the emergence of alternative reproductive tactics within a species?

High competition and varying reproductive success. Signup and view all the answers

What feature is common among male dung beetles with respect to reproductive strategies?

They exhibit both large horned and small hornless males. Signup and view all the answers

What defines the term sexually dimorphic?

Males and females exhibit different physical characteristics. Signup and view all the answers

What happens to the fitness of rare reproductive strategies compared to common strategies?

Rare strategies can achieve higher fitness when they are infrequent. Signup and view all the answers

Why might sneaker strategies be advantageous in certain populations?

They provide opportunities for fertilization without direct competition. Signup and view all the answers

Study Notes

Costs of Reproduction

Organisms cannot maximize all life-history traits simultaneously.
There is a trade-off between traits, meaning an increase in one trait may lead to a decrease in another.
For example, bright male guppies have high reproductive success, but they are more visible to predators.
The cost of reproduction can vary, such as the increased risk of predation for brightly colored guppies.

Selection on Life Histories

Evolutionarily successful organisms survive to reproduce and reproduce successfully.
Natural selection favors genotypes that result in the highest fitness relative to other genotypes.
This is a fundamental component of the meaning of life.

r-Selection vs. K-Selection

Life histories can be categorized into r-strategy and K-strategy.
r-strategy emphasizes rapid growth and fast reproduction, often with many offspring, while K-strategy emphasizes slower growth, reaching a stable maximum with fewer offspring.
Examples of r-selected organisms include squirrels, while examples of K-selected organisms include sharks and humans.

Fast vs. Slow Life Histories

Life histories can be further categorized into fast and slow.
Fast life history is characterized by high fecundity, short lifespan, lots of offspring, and a young age of maturity.
Slow life history is characterized by low fecundity, long lifespan, few offspring, and an old age of maturity.

Alternative Life Histories

Life histories can vary within a species and multiple strategies can be successful.
This can be seen in Bluegill Sunfish, where males can employ different reproductive strategies.
Examples of alternative life histories include:
- Parental: Male guards eggs and cares for young.
- Sneaker: Smaller male quickly fertilizes eggs, a "dead-beat dad" strategy.
This can lead to frequency-dependent selection, where the fitness of a particular strategy depends on the frequency of other strategies.

Harvest-Induced Evolution

Intensive harvest can lead to genetic changes, driving earlier age of maturity and smaller size at maturity.
Selective hunting of males with large horns has led to a decline in body size and horn length in Alberta's bighorn sheep.
This demonstrates how human activities can influence the evolution of life histories, even leading to declines in populations.

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Description

Explore the fascinating concepts of reproductive costs and selection on life histories in this quiz. Delve into r-selection and K-selection strategies and understand how organisms balance trade-offs to maximize their fitness. Test your knowledge of these essential principles in evolutionary biology.