Problem 2 - Campbell Biology

Question

Knowledge/Comprehension The principle of competitive exclusion states that (A) two species cannot coexist in the same habitat. (B) competition between two species always causes extinction or emigration of one species. (C) two species that have exactly the same niche cannot coexist in a community. (D) two species will stop reproducing until one species leaves the habitat.

Step-by-Step Solution

Answer

Option C.

Step 1: Understand the Principle of Competitive Exclusion

The principle of competitive exclusion, also known as Gause's Law, states that two species competing for the same limiting resources cannot coexist at constant population values. This principle is based on the observation that if two species share the exact same niche (the role or position a species has in its environment), they will compete for the same resources, and one species will outcompete the other.

Step 2: Analyze Option A

Option A states: 'two species cannot coexist in the same habitat.' This is incorrect because species can coexist in the same habitat if they occupy different niches or utilize different resources.

Step 3: Analyze Option B

Option B states: 'competition between two species always causes extinction or emigration of one species.' While competition can lead to extinction or emigration, it is not always the outcome because species may adapt or evolve different niches to reduce competition.

Step 4: Analyze Option C

Option C states: 'two species that have exactly the same niche cannot coexist in a community.' This option correctly reflects the principle of competitive exclusion, as species with the exact same niche will compete for the same resources and one will ultimately dominate.

Step 5: Analyze Option D

Option D states: 'two species will stop reproducing until one species leaves the habitat.' This is not a mechanism described by the competitive exclusion principle and does not accurately represent the biological concept.

Step 6: Choose the Correct Answer

Based on the analysis, the accurate representation of the principle of competitive exclusion is provided by Option C.

Key Concepts

Niche Differentiation

First, let's understand what a niche is. A niche encompasses everything a species requires and does in its environment. Think of it as the 'job' of the species within the ecosystem. Each species has its unique niche, which reduces competition for resources.
Niche differentiation occurs when species evolve different ways of utilizing resources. For example, birds living in the same tree might eat at different heights or times of the day. This variation helps species coexist by minimizing direct competition for identical resources. When species exploit different niches, they can share the same habitat without outcompeting each other.
In contrast, if two species have identical niches, they will compete intensively. One will eventually outcompete the other, possibly leading to the latter's extinction or emigration.

Species Coexistence

Species coexistence refers to the ability of multiple species to live in the same habitat without one outcompeting the other. This balance is often achieved through niche differentiation.
In a stable ecosystem, species coexist by occupying different niches. This means they use distinct resources or engage in different behaviors, reducing direct competition. For example, one species might feed on insects found in the bark of a tree, while another might feed on insects in the leaves.
Factors like environmental conditions, resource availability, and evolutionary adaptations play crucial roles in enabling species coexistence. These adaptations can lead to behavioral changes or even physical changes that allow species to exploit different resources.

Resource Competition

Resource competition happens when multiple species vie for the same limited resources. These resources can be anything from food and water to shelter and mates. When resources are scarce, competition intensifies.
There are two main types of resource competition:

• Intraspecific competition: Competition between members of the same species. For example, two tigers may compete for the same prey.
• Interspecific competition: Competition between members of different species. For example, a lion and a hyena competing for the same carcass.

Efficient resource use and adaptations such as behavioral changes are crucial for survival during intense competition. If one species is better at utilizing resources, it may outcompete the other, leading to possible extinction or migration of the less competitive species.

Gause's Law

Gause's Law, or the competitive exclusion principle, states that two species competing for the same limiting resources cannot stably coexist. This concept was formulated by the Russian ecologist G.F. Gause in the 1930s.
According to Gause's Law, if two species have identical niches, one will inevitably outcompete the other. The less competitive species will either adapt, migrate, or face extinction. This principle highlights the importance of niche differentiation for species coexistence.
Examples of Gause's Law in action are seen in laboratory experiments and natural ecosystems. In the lab, Gause demonstrated this principle using two species of Paramecium: Paramecium aurelia outcompeted and led to the extinction of Paramecium caudatum when grown together in a Petri dish with limited resources.