ECOSYSTEM BASICS
What is an ecosystem?
living and non-living things interacting in an area
Where does most energy in ecosystems come from?
the sun
What trophic level are producers?
first trophic level
What process do plants use to take in CO₂?
photosynthesis
What is carrying capacity?
max population an environment can support
What is an invasive species?
non-native species that harms ecosystems
Give one biotic and one abiotic factor.
What is (example) plant & sunlight
What do producers do with sunlight?
convert it into chemical energy (photosynthesis)
What is a primary consumer
herbivore that eats producers
What process releases CO₂ back into the atmosphere?
cellular respiration
Name two factors that limits population size.
food / water / predators / competition
Why does a population not grow exponentially forever in an ecosystem?
Limited resources and factors like competition, disease, and predation limit growth
What level includes all ecosystems on Earth?
biosphere
How much energy transfers to the next trophic level?
10%
Name one detritivore or decomposer.
bacteria / fungi / earthworm
Why can’t plants use nitrogen gas (N₂) directly? What is the usable forms?
it must be fixed into usable forms nitrates (NO₃⁻) or ammonium (NH₄⁺)
What is the difference between intraspecific and interspecific competition?
same species vs different species
What is succession?
gradual change in an ecosystem over time
Why are abiotic factors important to organisms?
they affect survival and growth
If plants have 5000 kJ, how much energy goes to herbivores?
500 kJ
Why are top predators few in number?
low energy availability
What type of organisms perform nitrogen fixation
bacteria (nitrogen-fixing bacteria)
Why does population growth slow at high density?
increased competition and disease
What is the difference between primary and secondary succession?
no soil vs soil already present
A drought reduces water in an ecosystem. Predict one effect on organisms.
decreased populations due to limited resources
Why are food chains usually short (3–4 levels)?
energy is lost at each level?
An organism eats both plants and animals. What is it and what trophic levels can it occupy?
omnivore; multiple trophic levels
what happens when too much fertilizer enters water systems.
algal blooms → oxygen depletion → organisms die
Give one density-dependent and one density-independent factor.
competition (dependent) and natural disaster (independent)
Why can human activities permanently damage ecosystems?
soil loss, pollution, deforestation, or species extinction preventing recovery