Feeding Relationships Teacher Notes PDF

Feeding Relationships A. What happens to energy in an ecosystem as one organism eats another? The energy flows in a one-way path through the ecosystem. Energy enters the ecosystem in the form of sunlight. Photosynthetic organisms convert the sun’s energy into molecules of glucose. This energy is th...

Feeding Relationships A. What happens to energy in an ecosystem as one organism eats another? The energy flows in a one-way path through the ecosystem. Energy enters the ecosystem in the form of sunlight. Photosynthetic organisms convert the sun’s energy into molecules of glucose. This energy is then passed on to the animals that eat the plants and to the animals that eat other animals. B. Energy flows through an ecosystem in one direction, from the sun to autotrophs and then to various heterotrophs. C. Food Chains 1. The energy stored by producers in the form of glucose molecules can be passed through an ecosystem along a food chain. 2. A food chain is a series of steps in which organisms transfer energy from one organism to another by eating and by being eaten. 3. All food chains begin with an autotroph. 4. Examples: a) grass à mouse à snake à hawk b) marine algae à zooplankton à small minnow à squid à whale D. Food Webs 1. In an ecosystem, the feeding relationships between organisms are much too complex to be shown in a single food chain. 2. Many consumers eat more than one type of food. More than one species may feed on the same organism. 3. There are many complex interactions between many different food chains. 4. Food web: The network of complex interactions formed by the feeding relationships among the various organisms in an ecosystem. 5. A food web links all the food chains in an ecosystem together. E. Trophic Levels 1. Each step in a food chain is called a trophic level. The trophic level indicates the organism’s position in the sequence of energy transfers. 2. The first trophic level in a food chain is always made up of producers. These organisms are referred to as primary producers. 3. The second trophic level is occupied by the herbivores that feed on the producers. These organisms are referred to as primary consumers. 4. Predators of herbivores belong to the third level. These organisms are referred to as secondary consumers. 5. A tertiary consumer eats the secondary consumer. 6. Each consumer depends on the trophic level below it for energy. 7. Most ecosystems contain only three or four trophic levels.