Food Webs and Energy Pyramids Objectives • Identification of the feeding relationships of animals in an ecosystem • Tracing the flow of energy and nutrients through an ecosystem • Understanding how organisms in an ecosystem are interrelated • Understanding the complex and dynamic nature of an ecosystem. Ecosystems • Biotic Factors: Any living part of an environment. • Abiotic Factors: Any non-living part of an environment. Examples: Feeding Strategies • Autotroph - organisms that is able to capture energy from sunlight and use it to produce its own food from inorganic compounds, also called a producer. • Heterotroph -organisms that obtain food by consuming other living things, also called a consumer. Feeding Strategies • Producers/Autotroph- Sunlight is the main energy source for life on Earth. – Definition-organisms that can capture energy from sunlight and use that energy to produce food. – Examples: Feeding Strategies • Consumers/Heterotrophs • Definition:-organisms that rely on other organisms for their energy and food. • Examples: – Herbivores- such as cows, obtain energy by eating only plants. – Carnivores- such as snakes, eat only animals. – Omnivores- such as humans, eat both plants and animals. – Detritivores- such as earthworms, feed on dead matter. – Decomposers- such as fungus, break down organic matter. – Scavengers- such as vultures, consume the carcass of other animals. Trophic Levels Energy, Producers, and Consumers Trophic Levels • Producers • Definition- the beginning level in a food chain that contains organisms that use energy directly from the sun for life processes. For example: Plants and other autotrophs use sunlight to produce sugars and oxygen. • Examples: plants, some protists (algae), some bacteria (cyanobacteria) Trophic Levels • Primary Consumers • Definition- Organisms that obtain nutrients by consuming producers. They indirectly use energy from the sun that was captured by the producers. For example: when plants are eaten by animals. • Examples: Rabbits, field mice, birds, and prairie dogs. Trophic Levels • Secondary Consumers • Definition- Organisms that obtain nutrients by consuming other consumers. They indirectly use energy from the sun that was captured by the producers and other consumers. • For example: Foxes, birds, snakes Trophic Levels • Tertiary Consumers and Top Predator Definition: Tertiary Consumers are carnivores /organisms that eat only animals and they feed on secondary and primary consumers. Examples: Harris’s Hawks, rattlesnakes, dogs, owls, bald eagles, plankton-eating fish, shrew, lions and tigers. Trophic Levels • Detritivores – Definition – organisms that consume dead and decaying organic matter http://www.bing.com/images Trophic Levels • Decomposers Definition: Organisms that break down and obtain energy from dead organic matter. Examples: Bacteria, fungi, mushrooms, mites, gitterbug, millipede, slug, earthworm, snail, and the dung beetle. Trophic Levels Trophic Levels Food Chain vs. Food Web A food chain is a series of steps in which organisms transfer energy by eating and being eaten. Food Chain vs Food Web A food web is a network of several interacting food chains. Dynamic Nature of Ecosystems Changes in Ecosystem • Top Down – Owls increase – Mice decline – Grass increases Changes in Ecosystem • Bottom up – Add fertilizer- more grass – More mice – More owls Energy Pyramid Energy transfer is only 10% from one trophic level to the next higher trophic level Lots of produces Few top predators