Population Ecology and Life History Strategies Study Guide

Q8. Distinguish between semelparity and iteroparity. List what factors may favour the evolution of each life history strategy.

Background

Topic: Life History Strategies

This question tests your understanding of reproductive strategies in organisms and the ecological or evolutionary factors that influence these strategies.

Key Terms

• Semelparity: A reproductive strategy where an organism reproduces only once in its lifetime, often producing many offspring at once.

• Iteroparity: A reproductive strategy where an organism reproduces multiple times over its lifespan, usually producing fewer offspring per event.

• Life History Strategy: The overall pattern in average timing and nature of life history events, shaped by natural selection.

Step-by-Step Guidance

1. Define semelparity and iteroparity, focusing on the number of reproductive events and offspring produced.

2. Consider environmental factors such as predictability, mortality rates, and resource availability that might favor one strategy over the other.

3. Think about examples of organisms that use each strategy and why these strategies might be adaptive in their environments.

4. List at least two factors that could favor the evolution of semelparity and two for iteroparity, based on ecological context.

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Q9. Identify “trade-offs” in life history strategies.

Background

Topic: Life History Trade-offs

This question is about understanding how organisms allocate limited resources (energy, time) to growth, reproduction, and survival, and the compromises involved.

Key Terms

• Trade-off: A situation where an increase in one life history trait results in a decrease in another due to limited resources.

• Life History Traits: Characteristics such as age at first reproduction, number of offspring, and lifespan.

Step-by-Step Guidance

1. Recall that resources are finite, so investing more in one trait (e.g., reproduction) means less is available for others (e.g., growth or survival).

2. Identify at least two common trade-offs, such as between number of offspring and parental care, or between early reproduction and longevity.

3. Think about how these trade-offs might differ in r-selected versus K-selected species.

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Q10. Characterize a typical r-selection life history strategy and a typical K-selection life history strategy.

Background

Topic: r/K Selection Theory

This question tests your ability to distinguish between two major reproductive strategies and their ecological contexts.

Key Terms

• r-selection: Selection for traits that maximize reproductive success in uncrowded environments; often associated with high growth rates.

• K-selection: Selection for traits that are advantageous at high population densities; often associated with competitive ability and efficiency.

Step-by-Step Guidance

1. List the main characteristics of r-selected species (e.g., many offspring, little parental care, short lifespan).

2. List the main characteristics of K-selected species (e.g., few offspring, high parental care, long lifespan).

3. Consider the types of environments where each strategy is favored (unstable vs. stable).

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Q11. Explain how density-dependent factors affect population growth.

Background

Topic: Population Regulation

This question is about understanding how certain factors influence population size more strongly as population density increases.

Key Terms

• Density-dependent factors: Factors whose effects on population size increase or decrease depending on the population density (e.g., competition, predation, disease).

• Population Growth: The change in the number of individuals in a population over time.

Step-by-Step Guidance

1. Define what density-dependent factors are and give examples.

2. Explain how these factors can limit population growth as density increases (e.g., increased competition for resources).

3. Describe how density-dependent regulation can stabilize population size near carrying capacity.

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Q12. Explain how weather and climate can function as density-independent factors in controlling population growth.

Background

Topic: Population Regulation

This question focuses on factors that affect population size regardless of density, such as environmental disturbances.

Key Terms

• Density-independent factors: Factors that affect population size regardless of the population's density (e.g., natural disasters, temperature extremes).

• Population Growth: The change in the number of individuals in a population over time.

Step-by-Step Guidance

1. Define density-independent factors and provide examples related to weather and climate.

2. Explain how these factors can cause sudden changes in population size, regardless of how many individuals are present.

3. Discuss why these factors do not regulate population size in the same way as density-dependent factors.

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Q13. Explain how predator and prey populations fluctuate in response to the other.

Background

Topic: Population Dynamics

This question is about the cyclical interactions between predator and prey populations and how each influences the other's size over time.

Key Terms

• Predator-prey dynamics: The interactions between predators and their prey that result in population cycles.

• Population Fluctuations: Changes in population size over time, often in a regular pattern.

Step-by-Step Guidance

1. Describe the typical pattern of predator and prey population cycles (e.g., as prey increases, predator numbers follow, then both decline).

2. Explain the cause-and-effect relationship between the two populations.

3. Consider time lags and other ecological factors that can influence these cycles.

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Q14. Describe the pattern of and major events in the growth of the human population.

Background

Topic: Human Population Growth

This question asks you to summarize the historical and current trends in human population size and the key events that have influenced these trends.

Key Terms

• Exponential Growth: Rapid increase in population size when resources are abundant.

• Demographic Transition: The shift from high birth and death rates to lower birth and death rates as a country develops.

Step-by-Step Guidance

1. Outline the general pattern of human population growth (slow, then rapid, then slowing again).

2. Identify major events that have caused changes in growth rate (e.g., agricultural revolution, industrial revolution, medical advances).

3. Discuss the concept of demographic transition and its impact on population growth rates.

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Q15. Explain current hypotheses about carrying capacity of Earth for human populations.

Background

Topic: Carrying Capacity

This question is about the maximum number of humans that Earth can sustainably support, considering resource use and technological advances.

Key Terms

• Carrying Capacity (K): The maximum population size that an environment can sustain indefinitely.

• Resource Limitation: The idea that finite resources (food, water, space) limit population size.

Step-by-Step Guidance

1. Define carrying capacity and discuss factors that influence it for humans (e.g., technology, consumption patterns).

2. Summarize at least two current hypotheses or estimates about Earth's carrying capacity for humans.

3. Consider the role of ecological footprint and resource distribution in these hypotheses.

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Q16. Describe how ecological footprint can be calculated and its value for the planet, for developed and developing nations.

Background

Topic: Ecological Footprint

This question focuses on measuring human impact on the environment and comparing resource use between nations.

Key Terms

• Ecological Footprint: The amount of land and water area required to produce the resources a person or population consumes and to absorb the wastes they generate.

• Biocapacity: The capacity of ecosystems to produce useful biological materials and absorb wastes.

Step-by-Step Guidance

1. Explain the basic calculation of ecological footprint (resource consumption and waste production per capita).

2. Discuss how ecological footprint varies between developed and developing nations.

3. Describe why understanding ecological footprint is important for sustainability and resource management.

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