4.2

What is the initial source of energy for most communities?

Light

How does energy move through a food chain?

energy enters as sunlight;

trapped by plants / producers / autotrophs;

converted to chemical energy in photosynthesis;

energy flows through the trophic levels in food chain;

passed to first consumers when they eat plants then from consumer to consumer by feeding;

energy passes to decomposers in dead organic matter;

How is energy lost from a food chain?

lost from the community as heat as a result of cell respiration / metabolism / movement;

energy is lost between trophic levels due to parts that are not eaten / assimilated and due to excretion;

Why are food chains usually limited to only a few trophic levels?

energy transfers between trophic levels are very inefficient/high energy losses between levels

approximately 90% lost / 10% passed on between trophic levels;

number of trophic levels limited by amount of energy entering into the ecosystem

Why is the biomass lower at higher trophic levels than at those below them?

due to losses of carbon dioxide, water and other waste products of metabolism

Explain the difference in the movement of energy and nutrients in ecosystems.

energy enters from (sun)light and is captured by producers;

energy flows through the trophic levels;

energy transfer is (approximately) 10% from one level to the next due to heat energy is lost through (cell) respiration, energy loss due to material not consumed / assimilated / excreted;

nutrient cycles within ecosystem / nutrients are recycled;

nutrients absorbed by producers and move to consumers through food chain by eating / digestion of other organisms;

nutrients recycled from decomposition of dead organisms;

State the role of decomposers in an ecosystem

To recycle nutrients

Explain the shape of, a typical pyramid of energy.

\-the shape of pyramid shows energy lost from base to top of pyramid

each level on the pyramid is about 10% of the size of the one below it because 90% energy lost between levels;

energy is lost as it flows through a food chain, most as heat through respiration and the rest by waste products / not all the organism is consumed;