Levels of Organization
What is the correct order from smallest to largest: ecosystem, biosphere, organism, community, population?
Organism → Population → Community → Ecosystem → Biosphere
What is the main source of energy for most life on Earth?
The Sun
What do all food chains begin with?
Producers
Define symbiosis.
A close relationship between two different species.
What is the biosphere?
The part of Earth that supports all living things, including land, water, and air.
What is the difference between a community and an ecosystem?
A community has only living things; an ecosystem includes both living and nonliving things.
What process allows producers to convert solar energy into sugar?
Photosynthesis
What do arrows in a food chain represent?
The direction of energy flow
Both species benefit—what is this called?
Mutualism
How does matter move through ecosystems?
Matter cycles through living and nonliving parts of the ecosystem.
Give one example of a biotic factor and one abiotic factor.
Biotic: tree, bacteria; Abiotic: sunlight, soil, water.
What is the 10% rule?
Only 10% of energy passes to the next level; rest lost as heat.
Why are food webs more accurate than food chains?
They show many feeding relationships
One benefits, one unaffected—what is this called?
Commensalism
What is the difference between weather and climate?
Weather = short-term; Climate = long-term average.
What is a population?
A group of the same species living in the same area.
Why are there fewer predators than prey?
Energy decreases at higher trophic levels.
If grass → rabbit → snake → hawk, what is the secondary consumer?
The snake
One benefits, one harmed—what is this called?
Parasitism
Why are greenhouse gases important for life on Earth?
They trap heat and keep Earth warm enough to sustain life.
What would happen to a community if one population disappeared?
It could disrupt food webs and species interactions.
If producers capture 10,000 J of energy from sunlight, approximately how much energy will be available to tertiary consumers?
About 10 J — energy decreases by 90% at each trophic level (10% rule: 10,000 → 1,000 → 100 → 10).
What would happen if decomposers were removed?
Nutrients wouldn’t recycle; waste would build up.
Give one example of each type of symbiosis.
Mutualism: bee & flower; Commensalism: barnacle & whale; Parasitism: tick & dog.
Why are decomposers essential to the cycling of matter in an ecosystem?
Because they break down dead organisms and return nutrients to the soil, making them available for producers again.