Problem 6 - Campbell Biology Concepts & Connections

Question

Which of the following best illustrates ecological succession? a. A mouse eats seeds, and an owl eats the mouse. b. Decomposition in soil releases nitrogen that plants can use. c. Grasses grow in a deserted field, followed by shrubs and then trees. d. Imported pheasants increase in numbers, while local quail disappear.

Step-by-Step Solution

Answer

Option C.

Step 1: Understand the Concept of Ecological Succession

Ecological succession is the process by which the structure of a biological community evolves over time. It typically involves a series of stages, starting from a pioneer species and increasingly more complex communities until reaching a stable climate community.

Step 2: Analyze the Given Options

Review each option and determine which one best fits the definition of ecological succession.

Step 3: Evaluate Option A

Option A describes a food chain where a mouse eats seeds and an owl eats the mouse. This illustrates a predator-prey relationship rather than succession.

Step 4: Evaluate Option B

Option B explains a nutrient cycle involving decomposition and nitrogen use by plants. This depicts nutrient cycling, not ecological succession.

Step 5: Evaluate Option C

Option C describes a sequence where grasses grow in a deserted field, followed by shrubs and then trees. This illustrates the stages of ecological succession, starting with pioneer species and progressing to more complex plant communities.

Step 6: Evaluate Option D

Option D describes changes in population sizes of imported pheasants and local quail. This example fits competitive displacement but not ecological succession.

Step 7: Select the Best Option

Among all the options, only Option C illustrates the process of ecological succession with the clear progression of different biological communities.

Key Concepts

biological community

A biological community consists of various species of plants, animals, and microorganisms living together and interacting in a particular area. Each member of the community plays a specific role and relies on the presence of others to maintain balance. The composition and function of these communities can change over time due to factors such as competition, predation, and environmental conditions.
For example:

• Plants provide oxygen and food for other organisms.
• Animals can help with seed dispersion and pollination.
• Decomposers like fungi and bacteria break down dead material, recycling nutrients back into the ecosystem.

Understanding how these interactions work helps us predict changes and manage ecosystems better.

pioneer species

Pioneer species are the first organisms to colonize barren or disturbed environments. They pave the way for other species by modifying the environment, often making it more habitable. Examples of pioneer species include:

• Lichens and mosses in rock areas.
• Grasses and weeds in abandoned fields.

Pioneer species are tough and adaptable, with traits that allow them to survive harsh conditions. These traits include high reproductive rates and the ability to grow in poor soils. By establishing themselves, they create conditions where other, less tolerant species can eventually thrive.

ecosystem development

Ecosystem development is a process that starts with bare land or a disturbed area and progresses through a series of stages until reaching a stable, mature state known as a climax community. This development can take many forms:

• Primary succession begins with no soil, like a lava flow.
• Secondary succession occurs in areas where soil remains after a disturbance, like an abandoned farm.

Throughout these stages, the ecosystem becomes more complex and supports a greater diversity of species. For instance, an abandoned field will first see grasses and weeds, followed by shrubs, and eventually trees as the soil improves and microhabitats increase.

plant community stages

Plant community stages are the sequential phases of growth and species replacement observed during ecological succession. These stages help illustrate the dynamic nature of ecosystems. Key stages include:

• Pioneer Stage: Characterized by hardy species like grasses and lichens that stabilize the environment.
• Intermediate Stages: Shrubs and small trees begin to grow as soil conditions improve.
• Climax Community: A mature, stable ecosystem with diverse plant and animal species.

Each stage supports different wildlife and has unique environmental conditions. The process ensures a gradual increase in biological diversity and ecosystem complexity.