Food Webs
In a food chain where grass is eaten by grasshoppers, which are eaten by frogs, what happens to frogs if the grass is destroyed?
Frog numbers will decrease because their food source (grasshoppers) will have less food.
True or False: All invasive species are non-native to the environment they invade.
True.
In a relationship where ants protect aphids and get food, what is this type of symbiosis?
Mutualism — both organisms benefit.
If mountain lions eat rabbits, what happens to rabbit numbers when lion numbers go up?
Rabbit numbers will go down.
Between 1919 and 1923, snowshoe hare populations dropped. What likely happened to lynx populations?
Lynx populations likely dropped because they had less food (hares).
In a food chain: grass → grasshopper → frog → snake. What happens to the snake population if grasshoppers decrease?
The snake population will decrease because there will be fewer frogs to eat.
What is a main way that invasive species harm native species?
They outcompete native species for resources like food, water, and space.
Define mutualism in your own words.
A relationship where both species help and benefit each other.
If wolves are added and they eat deer, what will happen to the plants deer usually eat?
Plant populations will increase because fewer deer will be eating them.
If hare numbers rise sharply, what will eventually happen to lynx numbers?
Lynx populations will rise because there is more food available.
Explain the flow of energy in this chain: plants → insects → small birds → hawks.
Energy moves from plants to insects, then to small birds that eat insects, then to hawks that eat birds.
A fish species spreads in a new river and drives out native fish. What type of impact is this?
This is competition that harms native species — a negative ecological impact.
Give an example of mutualism.
Bees pollinate flowers while getting nectar for food.
Why would a rise in deer populations hurt the amount of plants available?
More deer means more plants are eaten faster, reducing plant numbers.
Hares rise, lynxes rise, hares fall — what happens to lynxes next?
Lynx populations will fall after hares fall because their food supply shrinks.
Why is it dangerous to an ecosystem if plants (producers) are removed?
Producers provide energy for all other levels; without them, the entire food web collapses.
Choose the best description: (A) invasive species always reproduce faster, (B) invasive species cause harm. Which is better and why?
B — invasive species cause harm even if they don’t reproduce faster.
What is one major difference between mutualism and competition?
In mutualism both species benefit; in competition, both species are harmed by trying to get the same resource.
Wolves and mountain lions both hunt rabbits. Is this competition or predation?
Competition — both are fighting over the same food source.
Why do predator numbers often peak after prey numbers peak?
Predators grow in response to more prey, but it takes time for births and growth.
In a chain of plants → insects → frogs → snakes → hawks, what happens if pesticides kill most insects?
Frogs will starve, leading to fewer snakes and hawks because each depends on the level below for food.
A new plant species spreads quickly, and fewer bees visit native flowers. Why is this species invasive?
It harms native plants by competing for pollinators and changes the ecosystem’s balance.
Fish clean parasites off a bigger fish and get protection in return. What type of relationship is this and why?
Mutualism — cleaners get food and protection, and the big fish gets health benefits.
If a disease kills most wolves, what will happen first to deer and then to plants?
Deer populations will rise due to fewer predators; plant populations will fall because of overgrazing by deer.
If plants decline from drought, what chain reaction happens to hares and lynxes over 5 years?
Plants decrease → hares have less food and decrease → lynxes have less prey and decrease later.