Photosynthesis and Ecosystems Flashcards

In the carbon cycle, which process returns carbon dioxide to the atmosphere from living organisms?

Answer: Cellular respiration

Cellular respiration in all living organisms breaks down glucose, releasing CO₂ back into the atmosphere.

What term describes organisms such as bacteria and fungi that break down dead organic matter?

Answer: Decomposers

Decomposers break down dead organic material, recycling nutrients back into the soil for use by producers.

Which of the following ecosystems stores the most carbon per unit area?

Answer: Tropical rainforest

Tropical rainforests have the highest density of plant biomass, making them the largest terrestrial carbon stores per unit area.

An ecosystem loses its top predator. What is the most likely immediate effect?

Answer: Herbivore populations increase unchecked

Without top predators, herbivore populations grow unchecked, which can lead to overgrazing and ecosystem destabilization.

Which nutrient cycle involves both the processes of fixation and denitrification?

Answer: Nitrogen cycle

The nitrogen cycle includes nitrogen fixation (N₂ → usable forms) and denitrification (nitrates → N₂ gas).

What percentage of energy is typically transferred from one trophic level to the next?

Answer: 10%

Only about 10% of energy is passed to the next trophic level; the rest is lost as heat through metabolic processes.

A pond ecosystem has algae, water fleas, small fish, and large fish. If algae are drastically reduced by pollution, which population is FIRST to be directly affected?

Answer: Water fleas

Water fleas are primary consumers that feed directly on algae, so they would be the first population to suffer from reduced algae.