WorksheetsKeystone species and Trophic Cascades
Total questions: 27
Worksheet time: 16mins
Why were wolves absent from Yellowstone from the 1920's to 1995?
There was no prey available, so they starved.
When all the elk died, the wolves moved to Canada.
Humans hunted and killed all the wolves in Yellowstone and the surrounding area.
The wolves migrated south to Texas for a warmer climate.
Wolves and elk sometimes hunt together for the same prey.
True
False
Why was the songbird population reduced by the presence of too many elk in Yellowstone?
Elk ate young trees, so birds had fewer places to nest.
Elk ate too many songbirds.
Wolves at songbirds when no elk were available.
Other species that feed from an elk killed by wolves include
foxes, rabbits, and mice
bears, foxes, and beavers
bears, eagles, and coyotes
beavers, rabbits, and mice
The species that creates habitat for fish and amphibians by building dams in rivers is
otters
coyotes
elk
beavers
A niche ________________.
is the function that an organism performs in the food web of that community.
includes everything else the organism does and needs in its environment.
is specific to each individual animal and plant.
All of the above.
How long were the wolves absent from Yellowstone National Park?
1 year
5 years
10 years
70 years
Explain why the population of elk built up.
There were just a lot of them and so they reproduced quickly.
There was lots of food for the elk in the park so they reproduced well.
There was no natural predator to hunt them so they became over populated.
No one is actually sure why this happened.
What happened to the vegetation because of the elk population?
The elk ate it all, They reduced the vegetation to almost nothing, or they devoured it, leaving it bare.
Nothing at all. the vegetation just grew as normal.
A drought actually caused the vegetation to die and the elk trampled what was left.
The elk ate some of it but lots of the vegetation remained.
Why did the height of trees grow dramatically?
The weather had been much better and the trees grew taller.
The trees did not grow dramatically. Everything stayed the same.
The elk was not there to eat it, and now it can grow.
Song birds & migratory birds returned because...
They come back in the spring every year as normal.
They came to find shelter in trees, as there were more and taller trees.
They liked to follow the wolves and eat their left overs.
As the weather was much better, they enjoyed the park more.
What happened to the vegetation because of the elk population?
The elk ate it all, They reduced the vegetation to almost nothing, or they devoured it, leaving it bare.
Nothing at all. the vegetation just grew as normal.
A drought actually caused the vegetation to die and the elk trampled what was left.
The elk ate some of it but lots of the vegetation remained.
Explain why the population of elk built up.
There were just a lot of them and so they reproduced quickly.
There was lots of food for the elk in the park so they reproduced well.
There was no natural predator to hunt them so they became over populated.
No one is actually sure why this happened.
Why did the height of trees grow dramatically?
The weather had been much better and the trees grew taller.
The trees did not grow dramatically. Everything stayed the same.
The elk was not there to eat it, and now it can grow.
Song birds & migratory birds returned because...
They come back in the spring every year as normal.
They came to find shelter in trees, as there were more and taller trees.
They liked to follow the wolves and eat their left overs.
As the weather was much better, they enjoyed the park more.
Beavers returned because...
There were more trees. They like to build dams and eat trees. They build many habitats and niches for other animals
They liked the warmer temperatures in the park because of climate change.
They are carnivores and will eat the wolves.
They are carnivores and will eat the elk.
Predator population lags behind prey population because......
Increase in predators leads to decrease in prey
Increase in predators leads to increase in prey
Increase in predators leads to decrease in producers
Increase in producers leads to increase in prey
in 1995 Wolves were reintroduced to Yellowstone National Park. Which answer below most accurately describes a possible trophic cascade the could result from the reintroduction of wolves?
wolves reintroduced-> deer population increased -> tree and vegetation cover decreased
wolves reintroduced-> beaver population decreased -> tree and vegetation cover increased
wolves reintroduced-> deer population decreased -> tree and vegetation cover increased -> beaver population increased
wolves reintroduced-> deer population decreased -> beaver population decreased -> songbird population increased
What is species diversity?
the different animals in an area
the different habitats in an area
the different plants in an area
the different living things (plants and animals) in an area
Why does increasing producers increase the populations of all trophic levels?
Producers increase the size of a habitat
Producers help keep predator populations in check
With more energy available the carrying capacity increases
Producers do not have a large impact on population sizes
What are limiting factors?
The maximum number of organisms an area can sustain
Scarce resources that limit the size of a population
Conditions that limit how much energy flows to the next trophic level
How diverse the populations of a community are
If the producer level of an ecosystem has 750,000 J of energy, how much energy would be passed on to the secondary consumers?
75,000 J
7,500 J
750 J
75 J
What type of graph represents exponential population growth?
A fluctuating graph
W - shaped curve
S-shaped curve
J - shaped curve
What does carrying capacity mean?
The amount of abiotic factors present in the environment
The total number of species living in an ecosystem
The number of offspring one mother can have in a year
The number of organisms an ecosystem can sustain
Which of the following would be a density independent limiting factor?
A virus spreading through a population
A forest fire burning down a forest
Birds competing for a limited amount of seeds
A new predator moving to an area
Which of the following would be a density-dependent limiting factor?
Two wolf packs having overlapping territories
Pollution
A flood
Deforestation
How does competition affect population?
Most populations do not have competition
It maximizes the carrying capacity of an ecosystem
It limits population sizes and drives natural selection
It benefits both species and increases their populations
