Chapter 3Ecosystem Ecology

Ecosystem – a particular location on Earth distinguished by its particular mix of interacting biotic and abiotic components

Ecosystem Ecology Examines Interactions Between the Living and Non-Living World

Some ecosystems, such as a caves and lakes have very distinctive boundaries

However, in most ecosystems it is difficult to determine where one ecosystems stops and the next begins

Ecosystem Boundaries

Even though it is helpful to distinguish between two different ecosystems, ecosystems interact with other ecosystems

Ecosystem Processes

Energy Flows through Ecosystems

Producers (autotrophs) are able to use the sun’s energy to produce usable energy through the process called photosynthesis

Photosynthesis and Respiration

Cellular respiration is the process by which other organisms gain energy from eating the tissues of producers

Photosynthesis and Respiration

Consumers (heterotrophs) – obtain energy by consuming other organisms

Primary Consumers (herbivores) – consume producers

Secondary Consumers (carnivores) – obtain their energy by eating primary consumers

Tertiary Consumers (carnivores) – eat secondary consumers

Trophic Levels, Food Chains, and Food Webs

Consumers (heterotrophs)

• scavengers: feed on dead organisms

Consumers (heterotrophs)

• detritivores: feed on detritus (partially decomposed organic matter, such as leaf litter & animal dung) and breakdown this organic material into smaller particles

Consumers (heterotrophs)

• decomposers: consumers that complete the “circle of life” by digesting organic materials into smaller molecules

What is the difference between a food chain and a food web?

Food Chains

Food chain – the sequence of consumption from producers through tertiary consumers

Food web – a more realistic type of food chain that takes into account the complexity of nature

Food Web

Gross primary productivity (GPP) – the total amount of solar energy that the producers in an ecosystem capture via photosynthesis over a given amount of time

Net primary productivity (NPP) – the energy captured (GPP) minus the energy respired by producers◦NPP = GPP – energy used by producers◦Measured in kg C/m2/year

Ecosystem Productivity

Where in the world is NPP the highest?

Net Primary Productivity

Net Primary Productivity

Why do food chains rarely have more than 4 or 5 trophic levels?

What do you think?

Food Chains

Which are more numerous in an ecosystem: producers or consumers?

Producers are always more numerous than consumers, why?

Energy LossOf the energy that an organism consumes, only a

small fraction (ecological efficiency of about 10%) is transferred to the next trophic level

Where does that energy go?

• Most of the energy is lost as heat