High School Earth Science: Ecosystems and Human Populations - Ecosystems — Flashcards

An ecosystem consists of all the organisms and the physical environment with which they interact. These biotic and abiotic components are linked together through nutrient cycles and energy flows. Energy enters the system through photosynthesis and is incorporated into plant tissue.

There are many different types of ecosystems. Climate factors determine which type of ecosystem is found in any given location. Different organisms live in different types of ecosystems, but every ecosystem has the same general roles and feeding relationships.    

Two basic roles that are found in all ecosystems are the roles of producer and consumer. Every ecosystem has producers, which are organisms that produce food in the form of chemical energy. The major producers are algae in the oceans, plants on land, and bacteria at hydrothermal vents. Plants and algae use the energy in sunlight to produce food by photosynthesis. Bacteria at hydrothermal vents use the energy in chemicals to produce food by chemosynthesis.    
All other organisms in an ecosystem are consumers. Consumers are organisms that obtain food energy by consuming other organisms. There are many different types of consumers. Herbivores are organisms that eat plants or other producers. These organisms break down plants or other producers to get the matter and energy they need. Deer are herbivores. Carnivores are organisms that eat other animals. They may eat herbivores or other carnivores. Lions are carnivores. Omnivores may eat plants and animals as well as fungi, bacteria, and organisms from other kingdoms.    
Raccoons are omnivores.    

The various ways in which organisms obtain food from other living things are called feeding relationships. There are a variety of different feeding relationships. For example, predators such as lions kill and eat prey organisms, such as antelope and zebra. Scavengers eat organisms that are already dead. For example, a hyena might eat the remains of an animal that was killed but not completely consumed by a lion. Decomposers break down dead organisms or the waste products of living organisms. In the process, they return nutrients to the ecosystem. Bacteria and fungi are examples of decomposers.