Key Concepts in Ecosystem Dynamics and Energy Flow

Why do leaves appear green?

Because they absorb other wavelengths and reflect green.

What's the key difference between materials and energy in ecosystems?

Materials are cycled; energy is not.

What must an ecosystem have to recycle nutrients?

Producers and decomposers.

What two gases do photosynthesis and respiration balance?

Carbon dioxide and oxygen.

What raw materials are required for photosynthesis?

Water and carbon dioxide.

What do decomposers do in ecosystems?

Break down large organic molecules into simple inorganic ones.

How can perch be classified in a food web?

As secondary or tertiary consumers depending on the chain.

How does biomass change at higher trophic levels?

It regularly decreases.

What do pyramids of energy show?

How energy flows and is lost; they are never inverted.

Which organisms are major decomposers?

Bacteria and fungi.

Which group has the highest biomass in terrestrial ecosystems?

Producers.

What is an organism's trophic level?

Its position in the food chain.

Why are food webs more accurate than food chains?

Because animals eat multiple types of food.

What do herbivores eat?

Producers.

What is the basic energy flow in ecosystems?

Producers → Consumers → Decomposers.

How do decomposers obtain energy?

From dead organisms.

What defines an autotroph?

It can make its own food via photosynthesis or similar means.

What defines a heterotroph?

It must consume other organisms for energy.

What do omnivores eat?

Both producers and consumers.

What are herbivores classified as?

Primary consumers.

Which ecological pyramid best shows energy flow?

A pyramid of energy.

What principle explains biomass loss in food chains?

The Second Law of Thermodynamics.

What forms the base of an ecological pyramid?

Producers.

Which cycles replenish materials in ecosystems?

Water, carbon, and nitrogen cycles.

What does a pyramid of biomass measure?

Total weight of organisms at each level.

What's the optimal temperature for insect hatching in the graph?

26°C.

How much energy passes from producers to primary consumers?

About 10%.

Where is the greatest productivity in an ecosystem?

At the level of producers.

In the chain oak tree → insect → bird → trout, which heterotroph gets the most energy?

The insect.

What happens if tent caterpillars are destroyed?

Photosynthesis in the ecosystem will increase.

Which is NOT a result of deforestation?

Rapid eutrophication.

In which cycle do bacteria have roles beyond decomposition?

The nitrogen cycle.

What bacteria replenish N₂ in the atmosphere?

Denitrifying bacteria.

Which are abiotic factors?

Temperature, water, and wind (all of them).

What is the correct process that releases nitrogen gas?

Denitrification of nitrates.

Which cycle involves only soil and water?

The phosphorus cycle.

What role do bacteria play in the carbon and nitrogen cycles?

Decompose (carbon) and fix nitrogen (nitrogen cycle).

Why do legumes help soil fertility?

They form symbiotic relationships with nitrogen-fixing bacteria.

What's the correct order from largest to smallest:

Ecosystem → Community → Population → Individual.

If producers capture 100,000 J of energy, how much reaches a snake?

100 J (tertiary consumer).

What is the correct order of energy flow?

Autotrophs → Herbivores → Carnivores → Decomposers.