Flow of Energy
Cycling of Matter
Population Dynamics
Biodiversity & Conservation
Biomes
100
This image depicts the simplest model for energy flow in an ecosystem, with arrows depicting energy flow and who is eating who. 
What is a food chain?
100
This is the step of the water cycle in which water is returned to the biosphere in the form of rain, sleet, or snow.
What is precipitation?
100
These factors are nonliving and interact with living factors to form an ecosystem.
What are abiotic factors?
100
This is the most biodiverse terrestrial biome.
What is the tropical rainforest?
100
This biome is characterized by a layer of permanently frozen soil called permafrost.
What is tundra?
200
This model shows complex feeding relationships for all species in an ecosystem. 
What is a food web?
200
Methane and carbon dioxide are known as this type of gas, which retains heat in the atmosphere and warms the earth.
What are greenhouse gases?
200
This relationship involves one organism benefitting while the other is being harmed. Example: a tick on a dog feeding on its blood.
What is parasitism?
200
A cat has a litter of kittens, three of them are orange like her, one is calico, and two are black. This is an example of this kind of biodiveristy.
What is genetic diversity?
200
This biome is also called Taiga.
What is boreal forest?
300
In an ecological pyramid, producers start with 100% of energy and primary consumers only get 10% of that energy due to energy being transformed and "lost" as this.
What is heat?
300
Detritivores, such as some mushrooms, eat this type of organic matter.
What is dead or decomposing matter?
300
This relationship involves two organisms both benefitting. Example: a flower provides a bee with nectar for food and the bee pollinates the flower for reproduction.
What is mutualism?
300
These are the three types of biodiversity.
What are genetic, species, and ecosystem?
300
This marine biome is a transitional biome between fresh and saltwater and consists of bogs, marshes, or swamps.
What is a wetland?
400
This process is how producers, such as plants or phytoplankton, use light or chemical energy to create their own food energy.
What is photosynthesis?
400
Too much of this nutrient can cause eutrophication, or algae blooms, that can kill off local fish and plant life in aquatic ecosystems.
What is Nitrogen or Phosphorus?
400
This dynamic involves one species preying on another for food. Example: a lion hunting a gazelle.
What is predation?
400
This is a species that affects an ecosystem's balance and stability more than other species.
What is a keystone species?
400
This marine biome consists of flowing freshwater that starts with a head and travels until it deposits water into the ocean at its mouth. Water only flows one direction in this biome.
What is a river?
500
This process is how plants and animals take in oxygen to allow for cells to break down glucose into usable energy (ATP) and release carbon dioxide into the atmosphere.
What is cellular respiration?
500
This organism is required for nitrogen fixation of nitrogen which allows for it to be used by plants. Hint: it is very, very small.
What is bacteria?
500
This relationship involves one organism benefitting while the other is not harmed or helped. Example: a bird nesting in a tree.
What is commensalism?
500
A habitat includes a lake, a forest, and a prairie. This is an example of this kind of biodiveristy.
What is ecosystem diversity?
500
In the open ocean, this zone allows for light to penetrate and sustains multiple species of producers such as plankton.
What is photic zone?