60 Apes Chapter 5 Vocab

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Apes Chapter 5 Vocab

Introduction to Chapter 5

Chapter 5 of the AP Environmental Science (APES) curriculum delves into the intricate world of ecosystems. In this chapter, students will explore the various components and processes that make up an ecosystem, as well as the factors that influence its stability and resilience. To fully grasp the concepts presented in this chapter, it is essential to familiarize oneself with the vocabulary associated with ecosystems. This article aims to provide a comprehensive overview of the key terms and definitions found in APES Chapter 5, allowing students to enhance their understanding and excel in their studies.

1. Ecosystem

An ecosystem refers to a dynamic complex of plant, animal, and microorganism communities and the nonliving environment, interacting as a functional unit. It encompasses both the biotic (living) and abiotic (nonliving) components within a specific area.

2. Biotic Factors

Biotic factors are the living components of an ecosystem, including plants, animals, fungi, and microorganisms. These organisms interact with one another and their environment, shaping the structure and function of the ecosystem.

3. Abiotic Factors

Abiotic factors refer to the nonliving components of an ecosystem, such as temperature, rainfall, sunlight, soil composition, and air quality. These factors play a crucial role in determining the distribution and abundance of organisms within an ecosystem.

4. Autotrophs

Autotrophs, also known as producers, are organisms capable of synthesizing organic compounds from inorganic substances. They harness energy from the sun (photosynthesis) or chemical reactions (chemosynthesis) to produce food, thus forming the base of the food chain in an ecosystem.

5. Heterotrophs

Heterotrophs, also known as consumers, are organisms that obtain energy by consuming other organisms. They cannot produce their own food and rely on autotrophs or other heterotrophs for sustenance. Heterotrophs can be further classified as herbivores, carnivores, or omnivores, depending on their feeding habits.

6. Herbivores

Herbivores are heterotrophs that consume only plant material. They play a crucial role in regulating plant populations and nutrient cycling within an ecosystem. Examples of herbivores include deer, cows, and rabbits.

7. Carnivores

Carnivores are heterotrophs that primarily consume other animals. They are often classified into different trophic levels based on their feeding habits. Primary carnivores feed directly on herbivores, while secondary and tertiary carnivores consume other carnivores. Examples of carnivores include lions, wolves, and snakes.

8. Omnivores

Omnivores are heterotrophs that consume both plant and animal material. They have a flexible diet and can adapt to different food sources. Humans are an example of omnivores, as they consume both plants and animals.

9. Decomposers

Decomposers are heterotrophs that break down organic matter into simpler compounds. They play a vital role in nutrient recycling within an ecosystem by converting dead organisms and organic waste into inorganic substances that can be utilized by autotrophs. Examples of decomposers include bacteria and fungi.

10. Trophic Levels

Trophic levels represent the different levels in a food chain or food web. They indicate the position of an organism in the transfer of energy and nutrients. The first trophic level consists of autotrophs, followed by herbivores, primary carnivores, secondary carnivores, and so on.

11. Food Chain

A food chain illustrates the flow of energy and nutrients from one organism to another within an ecosystem. It shows the linear transfer of energy as organisms consume and are consumed by others. For example, a simple food chain could be grass (producer) → rabbit (primary consumer) → fox (secondary consumer).

12. Food Web

A food web is a more complex representation of the feeding relationships within an ecosystem. It consists of interconnected food chains, demonstrating the multiple pathways through which energy and nutrients flow. A food web provides a more realistic view of the complex interactions between organisms in an ecosystem.

13. Energy Pyramid

An energy pyramid illustrates the flow of energy through different trophic levels in an ecosystem. It represents the decrease in available energy as one moves up the trophic levels, with only a fraction of energy transferred from one level to the next. This pyramid shape is due to the second law of thermodynamics, which states that energy is lost as heat during energy transfers.

14. Biomass

Biomass refers to the total mass of living or organic matter within a specific trophic level or an entire ecosystem. It can be measured in terms of the dry weight of organisms, excluding water content. Biomass provides insights into the productivity and energy storage capacity of an ecosystem.

15. Ecological Efficiency

Ecological efficiency measures the transfer of energy between trophic levels in an ecosystem. It represents the proportion of energy transferred from one trophic level to the next. Ecological efficiency is typically low, with estimates ranging from 5% to 20%, due to energy losses during metabolism, respiration, and incomplete digestion.

16. Nutrient Cycling

Nutrient cycling, also known as biogeochemical cycling, refers to the movement and exchange of nutrients between living organisms, the atmosphere, and the physical environment. The cycling of elements such as carbon, nitrogen, and phosphorus is essential for maintaining the balance and availability of nutrients within an ecosystem.

17. Eutrophication

Eutrophication is the excessive enrichment of water bodies with nutrients, particularly nitrogen and phosphorus. It often occurs due to human activities such as agricultural runoff, sewage discharge, and the use of fertilizers. Eutrophication can lead to algal blooms, oxygen depletion, and the decline of aquatic ecosystems.

18. Limiting Factors

Limiting factors are environmental conditions that restrict the growth, abundance, or distribution of organisms within an ecosystem. They can be biotic or abiotic factors, such as temperature, moisture, nutrient availability, predation, or competition. Limiting factors play a crucial role in shaping the structure and dynamics of ecosystems.

19. Keystone Species

A keystone species is a species that has a disproportionately large impact on its ecosystem relative to its abundance. Its presence or absence can greatly influence the structure and functioning of the ecosystem. Removing a keystone species often leads to cascading effects, affecting multiple trophic levels.

20. Succession

Succession refers to the gradual and predictable changes in the composition and structure of an ecosystem over time. It occurs in response to disturbances or as a natural progression. Primary succession starts in a barren area with no soil, while secondary succession occurs in an area with existing soil.


Mastering the vocabulary associated with APES Chapter 5 is essential for understanding the intricate workings of ecosystems. By familiarizing yourself with these key terms, you will be better equipped to analyze and interpret ecological concepts, enabling you to excel in your AP Environmental Science studies.