Problem 11 - Campbell Biology

Question

Synthesis/Evaluation EVOLUTION CONNECTION Explain why adaptations of particular organisms to interspecific competition may not necessarily represent instances of character displacement. What would a researcher have to demonstrate about two competing species to make a convincing case for character displacement?

Step-by-Step Solution

Answer

Character displacement involves evolutionary changes that reduce competition between species and must show genetic differences due to competition.

Step 1: Understand Interspecific Competition

Interspecific competition occurs when individuals of different species compete for the same resources, such as food or space.

Step 2: Define Adaptations

Adaptations are characteristics that have evolved to improve an organism's ability to survive and reproduce in its environment.

Step 3: Explain Character Displacement

Character displacement refers to the phenomenon where two species that compete for the same resources evolve distinct traits to minimize competition and allow for coexistence.

Step 4: Differentiate Adaptations from Character Displacement

Not all adaptations due to interspecific competition are examples of character displacement. Character displacement specifically refers to an evolutionary change that reduces competition between species by altering a trait.

Step 5: Criteria for Character Displacement

To demonstrate character displacement, a researcher must show: (1) the traits are different in sympatric populations (populations living in the same geographic area) versus allopatric populations (populations living in separate geographic areas), (2) the differences are genetically based, (3) the traits reduce resource competition between the species, and (4) the changes are a result of evolutionary pressure rather than phenotypic plasticity.

Key Concepts

Interspecific Competition

Interspecific competition takes place when different species vie for the same resources, such as food, light, or space. This competition may restrict the availability of resources that are critical for survival and reproduction. For example, two bird species might compete for the same types of insects.

Some important points to remember about interspecific competition:

• This type of competition occurs between distinct species, not within the same species.
• It can drive evolutionary changes to better suit the species for survival in a competitive environment.
• It does not always result in one species entirely outcompeting the other; both species may find ways to coexist.

Evolutionary Adaptation

An evolutionary adaptation is a trait that has evolved through natural selection, enhancing an organism's ability to survive and reproduce in its environment. These adaptations can be physical, like the long neck of a giraffe, or behavioral, like birds migrating south for the winter.

Here are a few key aspects of evolutionary adaptations:

• Adaptations are the product of generations of natural selection.
• They make organisms better suited to their environment and more competitive.
• The changes are genetic, passed from one generation to the next, and offer a clear survival or reproductive advantage.

Sympatric vs. Allopatric Populations

Sympatric populations live in the same geographical area and have the opportunity to interact frequently, while allopatric populations are separated by geographical barriers, such as mountains or rivers, that prevent interaction.

Understanding these terms is crucial in studies of character displacement:

• Sympatric populations may evolve distinct traits to minimize competition.
• Allopatric populations do not face the same competitive pressures and may retain similar traits.
• Research on character displacement often involves comparing these two population types to see if and how they differ.

Genetic Traits

Genetic traits are inherited characteristics passed down from parents to offspring through their genes. These traits can influence physical attributes like eye color or behavioral tendencies like predator avoidance.

Key points about genetic traits include:

• They are encoded in an organism’s DNA.
• Traits can be the result of single genes or combinations of multiple genes.
• Natural selection acts on these genetic traits, favoring those that improve survival and reproduction.

Phenotypic Plasticity

Phenotypic plasticity refers to an organism's ability to change its phenotype (observable characteristics) in response to environmental conditions, without genetic change. This is a flexible response, unlike genetic changes which are permanent.

Some aspects to consider about phenotypic plasticity:

• It allows organisms to better cope with varying environments.
• These changes are not passed to the next generation unless they provide a selective advantage that becomes genetically fixed.
• Examples include plants growing taller in shaded environments or animals developing thicker fur in cold climates.

Unlike genetic adaptations, phenotypic plasticity offers a reversible solution to environmental challenges, which makes it an important strategy for survival in fluctuating habitats.