Ecology Lecture Review

Community Ecology Overview

Population Definition

• Population: A group of individuals of the same species sharing a common area and resources, interacting with each other and their environment.

• Key questions regarding populations include:

  • What is the population size?

  • Where is it located?

  • How is it distributed?

  • What are the age structures?

  • How many offspring does each individual produce?

  • Is the population increasing or decreasing?

Learning Outcomes

• Identify and describe types of interspecific interactions.

• Explain niches and their role in species competition.

• Identify and differentiate between dominant, keystone, and foundation species.

• Draw and analyze food chains and food webs.

• Describe primary and secondary succession processes.

Interspecific Interactions

• Competition (-/-): Competition occurs over limiting resources (e.g., water).

Understanding Ecological Niches

Niche Definition and Concepts

• Niche: The range of resources a species can utilize and the conditions it can tolerate.

• Niche Overlap: When species share resources leading to competition.

• Fundamental Niche: The theoretical range of resources a species could use without limitations.

• Realized Niche: The actual resources used by a species, constrained by factors such as competition.

• Principle of Competitive Exclusion: Two species cannot coexist in the same niche in the same area; one will outcompete the other, leading to exclusion.

• Niche Differentiation: Competing species evolve to reduce competition by adapting to different niches.

• Character Displacement: Changes in species characteristics to minimize overlap and competition (e.g., beak depth in G. fortis).

Community Organization

Trophic Levels

• Trophic Level: Levels of feeding within an ecosystem.

• A sequence depicting energy flow is known as a Food Chain.

• Detritivores: Consume dead organic matter.

• Primary Producers: Organisms that create their own food and are food sources for other species.

• Primary Consumers: Herbivores that eat producers.

• Secondary Consumers: Carnivores that consume primary consumers.

Food Webs

• Illustrate complex trophic interactions and energy flow among organisms in an ecosystem.

• Arrows indicate direction of energy flow between species.

Key Species Roles

• Dominant Species: The most abundant species, exerting control through numbers (e.g., American chestnut).

• Keystone Species: Not necessarily abundant but crucial for community structure (e.g., sea otters).

• Ecosystem Engineers (Foundation Species): Modify habitats and maintain community structure (e.g., beavers).

Disturbance and Succession

Ecological Disturbance

• Any event that alters a community by removing organisms or changing resource availability.

Succession Stages

• Ecological Succession: Recovery process following a disturbance.

• Primary Succession: Begins in a lifeless area without soil.

• Secondary Succession: Occurs after disturbances that leave soils intact.

Soil Formation in Primary Succession

• Soil develops through weathering of rocks and accumulation of organic matter, supporting plant growth.

Stages of Succession

• Pioneer Species: Initial colonizers in disturbed areas.

• Subsequent stages include longer-lived plants leading to a Climax Community: a stable final community.

Summary of Key Concepts

• Community interactions can be beneficial, harmful, or neutral.

• Biological communities are characterized by diversity and trophic structures.

• Ecological disturbances influence species diversity and community composition.