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

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

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