Bio Section 2 BC online

What is an ecosystem?

A community of living organisms interacting with the nonliving components of their environment.

What is energy flow in an ecosystem?

The transfer of energy from producers to consumers, with energy lost as heat at each step.

What is the primary source of energy for most ecosystems?

The sun.

What are producers (autotrophs)?

Organisms that make their own food using sunlight or chemical energy.

What process do most producers use to capture energy?

Photosynthesis.

What are consumers (heterotrophs)?

Organisms that obtain energy by eating other organisms.

What is a primary consumer?

An organism that eats producers (herbivores).

What is a secondary consumer?

An organism that eats primary consumers.

What is a tertiary consumer?

An organism that eats secondary consumers.

What are decomposers?

Organisms that break down dead organisms and waste, returning nutrients to the ecosystem.

Why are decomposers important?

They recycle nutrients back into the ecosystem for reuse by producers.

What is a trophic level?

A feeding position in an ecosystem.

Why is energy flow considered unidirectional?

Energy enters as sunlight and exits as heat; it is not recycled.

Why is energy lost at each trophic level?

Energy is used for metabolism, growth, and lost as heat.

What is a food chain?

A linear pathway of energy transfer between organisms.

What is a food web?

A network of interconnected food chains within an ecosystem.

Why do ecosystems have fewer organisms at higher trophic levels?

Less energy is available at each successive level.

What is the 10\% rule?

Only about 10\% of energy is transferred from one trophic level to the next.

What is biomass?

The total mass of living organic matter in a trophic level.

What is an ecological pyramid?

A diagram showing energy, biomass, or number of organisms at each trophic level.

How does matter differ from energy in ecosystems?

Matter is recycled; energy is not.

What is a biogeochemical cycle?

The movement of elements through biological, geological, and chemical parts of Earth.

Why are biogeochemical cycles essential to life?

They recycle nutrients needed for organisms to survive.

What are the major biogeochemical cycles studied in ecology?

Water, carbon, nitrogen, and phosphorus cycles.

What is the water cycle?

The movement of water through evaporation, condensation, precipitation, and runoff.

What role do organisms play in the water cycle?

They absorb, release, and transpire water.

What is the carbon cycle?

The movement of carbon between the atmosphere, organisms, oceans, and Earth.

How do producers affect the carbon cycle?

They remove carbon dioxide from the atmosphere through photosynthesis.

How do consumers affect the carbon cycle?

They release carbon dioxide through cellular respiration.

What is the nitrogen cycle?

The process by which nitrogen is converted into forms usable by living organisms.

Why can’t most organisms use atmospheric nitrogen directly?

It must be converted into usable forms by bacteria.

What is nitrogen fixation?

The conversion of atmospheric nitrogen (N_{2}) into ammonia by bacteria.

What is the phosphorus cycle unique for?

It does not have a gaseous phase.

Why is phosphorus important to living organisms?

It is a key component of DNA, RNA, and ATP.

How do human activities affect biogeochemical cycles?

They can disrupt natural cycles through pollution, agriculture, and fossil fuel use.