Lesson 22: Ecosystem capture energy and cycle chemicals

one

Energy flow in ecosystems is ____-way

10

Energy transfer between trophic levels is inefficient: only ~__% of energy at one level is available to the next.

lost as heat or unassimilated

Most energy is ____________ (second law of thermodynamics) or _______________ (feces).

Net primary productivity

The energy left after plant respiration, and it determines energy available for herbivores.

Secondary productivity

Energy used by consumers for growth and reproduction.

evaporates, condenses, precipitates

Water Cycle: Water __________, transpires from plants (~90% in vegetated areas), ______________,_______________, infiltrates into aquifers, and is taken up by plant roots.

photosynthesis

Carbon dioxide is fixed in _____________ into organic molecules.

ammonia

Atmospheric nitrogen (N₂) is fixed into ___________ by bacteria (biotic) or lightning (abiotic).

nitrate

Nitrogen Cycle: Atmospheric nitrogen (N₂) is fixed into ammonia by bacteria (biotic) or lightning (abiotic). Ammonia becomes ____________ through nitrification.

Nitrogen Cycle

Atmospheric nitrogen (N₂) is fixed into ammonia by bacteria (biotic) or lightning (abiotic). Ammonia becomes nitrate through nitrification. Taken up by plants → consumed by animals → returned via

Phosphorus

Released by rock weathering → absorbed by plants → consumed by animals → returned by decomposers. Easily lost through runoff and sedimentation.

Top-down effects

Higher trophic levels influence lower ones (e.g., predators reducing herbivores, allowing algae to flourish).

Bottom-up effects

Primary productivity (energy at the base) determines how much energy is available for higher levels.

increases

As productivity ___________, herbivore and carnivore biomass increases after thresholds are met.

colonization and extinction

Species richness on islands is a balance between ____________ and _____________.

decrease

Colonization rates ____________ as more species are added; extinction increases as more species compete.