Specimen Prep - Organisms and Populations

Specimen Prep Guide: Organisms and Populations

Key Concepts (Recall & Understanding)

• Organism and its Environment: Understand the major abiotic factors (temperature, water, light, soil) and the responses of organisms to them (regulate, conform, migrate, suspend).
• Adaptations: Know the adaptations of organisms to different environments (e.g., desert plants and animals).
• Populations: Understand population attributes (birth rate, death rate, sex ratio, age pyramids) and population growth models (exponential and logistic).
• Population Interactions: Know the different types of interactions between species (predation, competition, parasitism, commensalism, mutualism).

Application Corner

• Problem Type: Interpreting age pyramids to determine if a population is expanding, stable, or declining.
• Example: A population has a large number of pre-reproductive individuals. What does this indicate about the future of the population? (Answer: The population is likely to expand).

Analytical Thinking

• Scenario: Two species of barnacles are found on the same rocky shore. One species is found in the upper intertidal zone, and the other is found in the lower intertidal zone. What type of interaction does this represent?
• Analysis: This is an example of competitive exclusion, where one species outcompetes the other for resources.
• Diagram Interpretation: Be able to interpret graphs showing logistic and exponential population growth.

Key Case Study

• Gause's Competitive Exclusion Principle: This principle states that two species competing for the same limiting resources cannot coexist at constant population values. One species will eventually outcompete and eliminate the other.

Assertion-Reason Practice

1. Assertion: In a logistic growth model, a population reaches a carrying capacity (K). Reason: The carrying capacity is the maximum population size that an environment can sustain indefinitely.

   • (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion.

2. Assertion: The interaction between a sea anemone and a clownfish is an example of commensalism. Reason: The clownfish gets protection from predators, while the sea anemone is neither harmed nor benefited.

   • (a) Both Assertion and Reason are true and Reason is the correct explanation for Assertion.

HOTS (Higher-Order Thinking Skills) Question

• Why is the logistic growth model considered more realistic than the exponential growth model for most animal populations?
  • Answer: Because resources in most habitats are finite. The logistic model accounts for the carrying capacity of the environment, which limits population growth as it approaches its maximum sustainable level.