Unit 8: Ecosystems and Food Webs
How energy and matter move through a habitat, one bite at a time, and what happens when one link in the chain disappears.
8 topics · 27 questions
Each topic is a path, not a menu: work down it in order and every question builds on the one above. Click any of them to watch the answer draw itself.
Food Chains
- How it worksHow does energy flow in one direction from a plant to a plant-eater to a meat-eater along a food chain?
- Common mistakeWhy isn't a food chain a real chain where energy passes back and forth in both directions?
- Going furtherWhat happens to the rest of a food chain if the plant at the very bottom disappears?
Your turn1 of 2
Why does every single food chain eventually trace back to the sun?Food Webs
- How it worksHow do overlapping food chains connect into one interlocking food web?
- Worked exampleFind how many different food chains run through a food web where a hawk eats both snakes and mice, and snakes also eat mice.
- Common mistakeWhy doesn't removing just one animal from a food web only affect that one animal's direct predator?
- Going furtherWhat happens to a whole food web when a keystone species like a wolf is removed from it?
Your turn1 of 2
In a food web, a hawk eats both snakes and mice, and snakes also eat mice. With 7 different plant types at the base, find the total number of distinct food chains from a plant to the hawk (each plant reaches the hawk either through a mouse directly, or through a mouse then a snake).Producers, Consumers, and Decomposers
- How it worksHow do producers make energy, consumers eat it, and decomposers recycle it all back into the soil?
- Worked exampleFind which role each organism plays: an oak tree, a deer, a wolf, and a mushroom, sorted into producer, consumer, or decomposer.
- Common mistakeWhy aren't decomposers just trash feeders with no important job in the ecosystem?
Your turn1 of 2
An oak tree, a deer, a wolf, and a mushroom need to be sorted by role. Which one is the DECOMPOSER?Energy Pyramids
- How it worksHow does only about 10 percent of the energy at one level of a food chain make it to the next level up?
- Worked exampleFind how much energy reaches a hawk if a mouse has 1000 units of energy and only 10 percent transfers to the next level.
- Common mistakeWhy doesn't all the energy a rabbit eats get passed on to whatever eats the rabbit?
- Going furtherWhat happens to how many top predators an ecosystem can support as the energy pyramid's levels stack higher?
Your turn1 of 2
Find how much energy reaches a hawk if a mouse has 6995 units of energy and only 10 percent transfers to the next level.Habitats and Biomes
- How it worksHow does an area's temperature and rainfall decide which biome, like a rainforest or a tundra, forms there?
- Common mistakeWhy isn't a habitat the same thing as a biome, even though the words get used interchangeably?
- Going furtherWhat happens to the plants and animals living in a biome when its average temperature and rainfall shift?
Your turn1 of 2
Why couldn't a polar bear survive if you dropped it into the middle of a desert?Ecosystems in Balance
- How it worksHow do predators, food, and disease keep a population from growing forever inside an ecosystem?
- Common mistakeWhy doesn't balance in an ecosystem mean every population stays at a perfectly fixed number forever?
- Going furtherWhat happens to a pond's balance when an invasive species with no natural predators is introduced?
Your turn1 of 2
Why does a healthy pond keep roughly the same number of fish and frogs year after year without anyone managing it?Symbiosis
- How it worksHow do mutualism, commensalism, and parasitism each describe a different kind of relationship between two species?
- Worked exampleFind which type of symbiosis each pair shows: a tick feeding on a dog, a clownfish and an anemone, a bird nesting in a tree.
- Common mistakeWhy isn't every close relationship between two species helpful to both of them?
Your turn1 of 2
A tick feeds on a dog's blood, harming the dog while benefiting itself. Which type of symbiosis is this?Populations
- How it worksHow do limiting factors like food, space, and predators cap how large a population can grow?
- Worked exampleFind the size of a rabbit population after one generation if 20 rabbits double, then a food shortage kills half.
- Common mistakeWhy doesn't a shrinking population always mean a species is heading toward extinction?
- Going furtherWhat happens to a predator's population when its main prey's population crashes?
Your turn1 of 2
Find the size of a rabbit population after one generation if 142 rabbits double, then a food shortage kills half.