Question

Over time, dark forms of the peppered moth (Biston betularia) became more common in polluted environments because predators were less able to detect them on trees darkened by soot. These moths are regarded by many as a(n) a. keystone species. b. indicator species. c. umbrella species. d. flagship species. e. endangered species.

Short answer

The term that best describes the peppered moth (Biston betularia) in this situation is an 'indicator species' (Option b).

Step-by-step solution

Understanding the problem

A biological event is described where a certain species, the peppered moth, undergoes a change over time in polluted environments, becoming more common due to better camouflage against predators on soot-darkened trees.

Defining the terms

'Keystone species' refers to a species that has a disproportionately large effect on its environment relative to its abundance. An 'indicator species' indicates the health of the ecosystem, their presence (or absence) can signal a change in the environment. An 'umbrella species' is a species selected for making conservation-related decisions, typically because they are vulnerable to threat. A 'flagship species' is one chosen to represent an environmental cause. An 'endangered species' is one that is at serious risk of extinction in the near future.

Matching the situation with terms

It does not appear that the moths have a large effect on their environment nor are they used for conservation decisions or to represent an environmental cause and they are not mentioned to be at risk of extinction. However, their presence and frequency of appearance indicate a change in the environment, i.e., pollution, making them an 'indicator species'.

Key concepts

Indicator Species

Indicator species are organisms used by ecologists and environmentalists to gauge the health of an ecosystem and to detect changes in environmental conditions. When populations of an indicator species decline or behave unusually, scientists can deduce that a change in the ecosystem is occurring. This could be due to factors such as pollution, habitat destruction, or climate change.

One classic example of an indicator species is the peppered moth (Biston betularia), which played a significant role during the Industrial Revolution. Before industrialization, the peppered moth predominantly exhibited a light coloring, which provided camouflage against the light-colored trees and lichens, helping them to avoid predation by birds. However, as pollution increased and soot covered the trees, the dark-colored moths, which were once a rarity due to their visibility to predators, became more common.

The change in frequency of dark-colored moths signaled a change in the environment caused by industrial pollutants. Thus, their presence and the changing frequency of different color morphs serve as a key indication of environmental alterations, fulfilling the role of an 'indicator species'.

Natural Selection

Natural selection is the process by which heritable traits that confer some advantage to an organism increase in frequency in a population because they contribute to an individual's reproductive success. The concept is a fundamental mechanism of evolution and was first formulated by Charles Darwin. It explains how species adapt over time to their environments.

In the case of the peppered moth, natural selection can be seen in the way the darker coloration became more prevalent in response to environmental pollution. Predators such as birds were less able to detect the dark moths against the soot-darkened trees, leading to increased survival rates of the dark moths compared to the lighter moths. Over time, this selective pressure increased the proportion of dark moths in the population.

The exercise showcasing peppered moth evolution illustrates how an external environmental change can lead to a selective pressure that affects a species’ physical characteristics, ultimately altering the gene pool of the population over generations.

Environmental Pollution

Environmental pollution refers to the introduction of harmful substances or conditions into the environment as a result of human activity. These pollutants can take various forms, including chemical substances, noise, heat, and light. Pollution has a profound impact on ecosystems, affecting wildlife and human health.

During the Industrial Revolution, one of the most evident forms of pollution was the release of soot from factories, which covered trees and buildings, turning them black. This environmental shift had a significant role in the evolution of the peppered moth. Prior to the pollution, the lighter moths were favored, as they were well-camouflaged against the light bark and lichens. However, post-industrial soot deposition flipped this advantage, favoring moths with darker pigmentation. The moth population's response to this pollutant is a clear example of how human actions can change the environment and influence the traits selected for in a species through natural selection.

Understanding how pollution affects species is crucial for conservation efforts and to mitigate negative impacts on biodiversity and ecosystem functions.