Unit 11 — Ecology
BIO.5 Interdependence of Organisms and Their Environments
Unit 11: Need to Know and Be Able to Do
11.1 - Ecological Hierarchy
Need to know
- Levels from smallest to largest: organism, population, community, ecosystem, biome, biosphere.
- A population is one species in one area; a community is all the populations, living things only.
- An ecosystem is a community plus the abiotic factors (water, soil, sunlight, temperature).
- Biotic means living or once living; abiotic means never alive.
Be able to do
- Classify a description as organism, population, community, or ecosystem.
- Sort biotic and abiotic factors.
- Put the levels of organization in order.
11.2A - Trophic Levels, Food Chains and Webs
Need to know
- Producers make their own food and are always trophic level 1.
- Consumers eat other organisms: herbivores, carnivores, omnivores; decomposers recycle nutrients.
- Food-chain arrows point from the eaten to the eater, the direction energy flows.
- A food web is many connected food chains.
Be able to do
- Order a food chain starting with sunlight and a producer.
- Identify primary, secondary, and tertiary consumers.
- Predict what happens in a food web when one population is removed.
11.2B - Energy Pyramids and the 10% Rule
Need to know
- About 10% of the energy passes up to the next trophic level; about 90% is used or lost as heat.
- The top of a pyramid has the least energy and biomass.
- There are more producers than consumers because less energy is available at higher levels.
- Energy flows one way; it is not recycled.
Be able to do
- Calculate the energy at any level with the 10% rule.
- Identify the level with the least biomass.
- Count steps between levels, not the levels themselves.
11.3A & 11.4 - Cycling of Matter
Need to know
- Carbon: photosynthesis removes CO2; respiration, decomposition, and burning release it.
- Nitrogen: nitrogen-fixing bacteria and lightning turn N2 into forms plants can use, such as nitrates.
- Water: evaporation, transpiration, condensation, precipitation, runoff.
- Phosphorus cycles through rocks, soil, and organisms with no gas phase.
Be able to do
- Trace an atom of carbon or nitrogen through a cycle diagram.
- Explain the role of nitrogen-fixing bacteria.
- Predict how killing soil bacteria would affect the nitrogen cycle.
11.3B - Greenhouse Gases and Climate
Need to know
- Greenhouse gases (CO2, methane, water vapor) trap heat in the atmosphere.
- Burning fossil fuels and clearing forests add CO2.
- Atmospheric CO2 rises when it is released faster than it is removed.
- Effects include rising sea level, longer growing seasons, and more acidic oceans.
Be able to do
- Read emissions and concentration graphs.
- Describe a direct relationship between two graphs.
- Predict future CO2 trends from data.
11.5 - Ecological Relationships
Need to know
- Mutualism +/+, commensalism +/0, parasitism +/−, predation +/−, competition −/−.
- Mimicry: a harmless species looks like a harmful one.
- Predator and prey populations rise and fall in cycles.
- Coevolution: two species change in response to each other.
Be able to do
- Classify a relationship from a description.
- Read a predator–prey graph.
- Explain how mimicry protects a species.
11.6 - Limiting Factors and Carrying Capacity
Need to know
- Exponential growth makes a J-curve; logistic growth makes an S-curve.
- Carrying capacity is the largest population an environment can support over time.
- Density-dependent factors (competition, disease, predation) get stronger with crowding; density-independent factors (fire, flood, drought) do not.
- A population that overshoots carrying capacity can crash and lower the carrying capacity.
Be able to do
- Identify carrying capacity on a graph.
- Classify limiting factors.
- Explain what shifts growth from exponential to logistic.
11.7 - Ecological Succession
Need to know
- Primary succession starts on bare rock with no soil; pioneers are lichens and mosses.
- Secondary succession starts where soil remains, such as after a fire; grasses grow first.
- Succession builds soil, species, and biomass toward a climax community.
- Ponds fill in over time and become land.
Be able to do
- Classify events as primary or secondary succession.
- Order the stages of succession.
- Explain the changes in a pond-to-forest diagram.
Unit 11 Flashcards
Study 88 cards by lesson deck or as one whole-unit deck.
Open flashcards full pageUnit 11 Interactive Review
Practice 48 questions per run, sampled from the complete 190-question Unit 11 review bank.
Start interactive reviewUnit 11 Quiz Options
Practice Quiz gives feedback after each answer. Unit Quiz shows results after you submit.
Practice Quiz—with feedback Unit Quiz11.1 Ecological Hierarchy
11.2A Trophic Levels, Food Chains and Webs
11.2B Energy Pyramids and the 10% Rule
11.3A & 11.4 Cycling of Matter
Trace carbon, nitrogen, water, and phosphorus through ecosystems.
Open untimed reviewTake graded quiz11.3B Greenhouse Gases and Climate
11.5 Ecological Relationships
Classify mutualism, commensalism, parasitism, predation, and mimicry.
Open untimed reviewTake graded quiz11.6 Limiting Factors and Carrying Capacity
11.7 Ecological Succession
Additional BIO.5 Review Links
Open the BIO.5 section of the Biology Review Doc for Blooket games and Wayground reviews.
Open BIO.5 review documentExplore with NASA
See Earth's ecosystems from space and the living things NASA studies in orbit.
Earth from SpaceSpace Biology GalleryWeather and Climate