C4.2 Transfer of energy and matter

What does it mean that ecosystems are open systems?

Energy and matter enters and leaves

What does it mean that the earth is a closed system?

Energy can leave or enter, but matter cannot. Therefore, it is a closed system.

What are autotrophs vs heterotrophs?

Autotrophs produce their own food (producer), heterotrophs eat other organisms for food (consumer)

What are the two types of autotrophs?

• chemoautotrophs (use inorganic compounds to synthesize carbon compounds e.g., iron-oxidizing bacteria that oxidizes inorganic compound of iron into organic compound of iron)

• phototrophs (use sunlight to synthesize carbon compounds)

What are the three types of heterotrophs?

• consumers (digest food internally from other organisms)

• Saprotrophs - decomposers (digest food externally from dead organisms)

• Detritivores - decomposers (digest food internally from dead organisms)

These consume other compounds from organisms, break them down in digestion through hydrolysis, and build them into the compounds they need via condensation reactions.

How do autotrophs and heterotrophs release energy from carbon compounds?

Through cell respiration

What is holozoic nutrition?

It is a heterotrophic nutrition. They ingest living organisms internally. This is mostly done by the heterotrophs of consumers.

What is saprophytic nutrition?

It is a heterotrophic nutrition done by saprotrophs. They digest food externally from dead or decaying organisms, by releasing enzymes to break it down.

What is the main source of energy in ecosystems?

Sunlight - for photosynthesis

Are there some ecosystems that do not rely on the sun for energy?

Yes, such as in a cave or in deep waters. Chemoautotrophs are there, which use chemicals instead of sunlight to produce.

How does energy travel through organisms?

It travels from producer to consumer, as they get eaten. Each level has receives less energy from what they eat, as it is lost on the way. The energy travel is represented through a food chain.

Food chain

The arrows show the transfer of energy and organic matter

Food web

What are the trophic levels in a food chain?

Producer, primary consumer, secondary consumer, tertiary consumer, apex predator/quaternary consumer

What do pyramids of energy show?

How much energy is transferred from one trophic level to the next. This decreases when moving up the chain, as approximately 90% energy is lost on the way.

Where is energy lost in the food chain?

• through heat / movement

• many organisms die before they are eaten - no more ATP generated - this is why decomposers are not included in the food chain

• some parts of the organisms are not eaten, such as bones, or are indigestible

What is the consequence of the loss of energy in the food chain?

It limits the number of trophic levels in the food chain, as there is less energy and less transfer of matter

What is primary vs secondary productivity

Primary productivity is how much carbon compounds are synthesized by autotrophs (through chemicals or sunlight), and secondary productivity is how much carbon compounds are synthesized by heterotrophs (through feeding on other organisms)

Give examples of strong and weak primary productivity in ecosystems

Strong - rainforests. They receive a lot of rainfall and sunlight which allows autotrophs to synthesize more carbon compounds and increase in biomass. This allows for greater secondary productivity

Weak - deserts. They are dry and the plants grow slowly. There is low secondary productivity

What is a carbon cycle?

It shows how carbon is reused and recycled in ecosystems. It shows sources and sinks.

What does the keeling curve show?

The carbon concentration in the earth’s atmosphere. As more photosynthesis occurs during the summer, CO2 levels are lower. In the winter, respiration is higher than photosynthesis, so CO2 levels are higher. The clear increase over time in CO2 concentration is due to human activities, particularly the release of fossil fuels into the atmosphere.

How is respiration in heterotrophs and photosynthesis in autotrophs linked together?

Heterotrophs rely on the oxygen produced during photosynthesis from autotrophs, and autotrophs rely on the carbon dioxide produced during respiration from heterotrophs.

Overall, how are chemical elements recycled in an ecosystem?

• Chemical elements and energy are recycled in an ecosystem

• Even when the animal dies, decomposers pass the energy on

• If chemical elements are lost, then productivity (both primary and secondary) would decrease