Nutrient Cycling

How does aerobic respiration by autotrophs depend on photosynthesis?

Autotrophs use oxygen produced by photosynthesis.

How does photosynthesis depend on heterotrophs?

Heterotroph respiration produces CO2 used in photosynthesis.

Which elements are essential for carbohydrates and lipids?

Carbon, hydrogen, and oxygen.

Which element is needed to make amino acids and DNA?

Nitrogen.

Which element is needed for DNA and ATP?

Phosphorus.

What is a nutrient cycle?

Recycling of chemical elements in ecosystems.

What do decomposers do?

Break down dead organisms and waste, releasing nutrients.

Name two types of decomposers.

Saprotrophs and detritivores.

How do saprotrophs obtain nutrients?

By secreting enzymes to digest organic matter externally.

What do decomposers convert complex organic matter into?

Usable nutrients for themselves and other organisms.

How do nitrogen-fixing bacteria help the nitrogen cycle?

Trap nitrogen from the air or organic matter in the soil.

What do other bacteria convert nitrogen into?

Ammonia, ammonium, and then nitrates.

How do plants use nitrates?

Incorporate them into proteins and chlorophyll.

How do animals obtain nitrogen?

By eating plants or other animals containing nitrogen compounds.