Ecosystems Food Webs Trophic Levels How is Life

Ecosystems Food Webs & Trophic Levels How is Life Connected?

The Web of Life - Ecosystems • Ecosystem is defined as a community including both nonliving (abiotic) and living (biotic) components. • By adding the physical environment, this level is given a whole new dimension to study. • The physical environment brings on new characteristics to study and measure such as energy flows and biochemical cycles.

The Web of Life • There are millions of different types of life on this planet. • All are interconnected in the web of life. • Sometimes the connection is easily seen, other times it is hard to see. • No organism, including humans, live on this planet in isolation—we are all interconnected.

Energy Transformation • Life in an ecosystem requires a source of energy. • The ultimate source of energy (for most ecosystems) is the sun • Solar energy is transformed into chemical energy by the process of photosynthesis. • It is stored as potential energy in plant tissues (in the form of starch). Most of this energy is used to carry on the plant's life activities. • Potential energy is transformed into mechanical energy (and heat is given off) during metabolic activities. • The rest of the energy is passed on as food to the next level of the food chain.

Energy Pyramids • An energy pyramid is a graphical model of energy flow in a community. • The different levels represent different groups of organisms that might compose a food chain. – Food chain: shows who’s eating who in the community.

Trophic Levels • When one organism eats another, molecules are metabolized and energy is transferred. • As a result, energy flows through an ecosystem from producers to consumers. • A trophic level is an organism’s position in a sequence of energy transfers in a food chain or food pyramid. – Examples include producers and primary, secondary and tertiary consumers.

Trophic Levels

The Triangle Shape • Why are energy pyramids shaped the way they are? • It shows the amount of useful energy that enters each level.

• 90% of the energy is consumed (at each level) only 10% is passed to the next level.

Trophic Levels • Organisms that get their energy from nonliving sources (sun, organic matter) are called autotrophs (or producers) and make up the 1 st trophic level. • Primary consumers make up the 2 nd trophic level. These are usually herbivores that eat plants. • The 3 rd trophic level consists of secondary consumers that eat primary consumers, and are primary carnivores. • The 4 th trophic level consists of tertiary consumers (or secondary carnivores).

Producers Are Autotrophs • Life in an ecosystem requires a source of energy. – Producers (Autotrophs). They are organisms that can synthesize organic substances from simple organic compounds, using light energy from the Sun, in the process of photosynthesis. – Producers provide food for virtually all other organisms in food chains and food webs. – Examples would be green plants, algae, and some types of bacteria. More examples: Chemosynthetic bacteria at hydrothermal vents & phytoplankton

Consumers: Primary, Secondary and Teritary • A consumer is an organism that eats other organisms to obtain energy. • They can be either primary, secondary, or tertiary consumers – Primary (Herbivore)—An organism that eats only plants. (Example: butterfly fish) – Secondary (Carnivore)—an organism that feed on herbivores. – Teritary – organisms that feed on secondary consumers Omnivore—an organism that obtains organic food molecules by eating other organisms or their products (they eat plants and animals). Secondary carnivore eats primary carnivores

Decomposers and Detritivores • Detritivores feed on the “garbage” of an ecosystem. This waste (or detritus) includes organisms that are dead, fallen leaves, and animal wastes. – Vultures, catfish, crawfish and crows are examples of detritivores. • Decomposers are organisms (like bacteria, worms and fungi). • Decomposers are important because they break down dead organic matter and change it to simpler nutrients which can be recycled in the ecosystem

Food Chains and Food Webs • Food chains and food webs model the flow of energy in an ecosystem. – A food chain is a simple model that shows a sequence of feeding relationships. – A food web provides a more complex picture of the network of feeding relationships among organisms in an ecosystem.

A Pond Food Chain This pond food chain shows how energy flows from the producers (plants & phytoplankton) to the primary, secondary and tertiary consumers and then to the decomposers.

A Mangrove Food Web What are the producers of this Mangrove Food Web: Do you know how to read this food web? The arrows point toward the organism that is the consumer.

Create a Food Web • Use the hand out to create a food web. • On the back of the food web, create a table listing all of the producers and consumers. • For each consumer tell whether it is a herbivore, carnivore or omnivore. • Draw a trophic level pyramid and tell which organisms would be in each trophic level.