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9th grade How relationships between species keep an ecosystem stable worksheet

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How relationships between species keep an ecosystem stable

Grade 9 Science Worksheet - Building Confidence

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Effects on the two partners in a lichen (data: OpenStax Biology)
partner effect
fungus gains
photosynthetic alga gains
1.
Ari reads the table about a fungus and an alga living together in a lichen. Which relationship does it show?
- Parasitism: the alga is harmed by the fungus
- Mutualism: both partners gain from living together
- Competition: the fungus and the alga both lose
- Commensalism: both partners gain from living together
Effects on a bird and the tree that holds its nest (data: OpenStax Biology)
partner effect
bird gains
tree unchanged
2.
Bo reads the table about a bird that builds a nest in a tree. Which relationship does it show?
- Commensalism: the bird gains and the tree is unchanged
- Mutualism: the bird gains and the tree gains too
- Parasitism: the bird gains and the tree is harmed
- Competition: the bird and the tree use one resource
Effects on a model parasite and its host plant (model data)
partner effect
parasite gains
host plant harmed
3.
Esme reads the table about a model parasite that lives on a host plant. Which relationship does it show?
- Parasitism: the parasite gains and the host is harmed
- Competition: the parasite and the host both lose
- Mutualism: the parasite gains and the host gains too
- Commensalism: the parasite gains and the host is unchanged
4.
Jun reads the graph of hare and lynx counts. Which sentence fits the graph?
- The hare count peaks, but the lynx count stays flat
- Both counts peak in the same year, then fall together
- The hare count peaks first, and the lynx count follows it
- The lynx count peaks first, and the hare count follows it
5.
Luz reads the graph. How many years pass from one hare peak to the next hare peak?
- 10 years: from year 4 to year 14
- 14 years: the whole time shown on the graph
- 2 years: the gap from the hare peak to the lynx peak
- 5 years: halfway between two hare peaks
Two species in a model stream (model data)
species individuals share of the phosphorus supplied (percent)
banded tetra 30 95
stream snail 500 5
6.
Milo reads the model data about a stream. Which species is the keystone species?
- Both species: each one lives in the stream
- The stream snail: it has the most individuals
- Neither species: the stream does not depend on one species
- The banded tetra: few individuals, but most of the phosphorus
Two cases of living things sharing a place (model data)
case what happens
A two plant species in one plot use the same limited supply of water, and both grow less
B a bird builds a nest in a tree, and the tree stays the same
7.
Noah reads the two cases. Which case shows competition?
- Both cases: living things share a place in each
- Case A: both species use the same limited water
- Neither case: competition needs animals that touch
- Case B: the bird uses the tree for a nest
Effects on a model parasite and a model host (model data)
partner effect
model parasite Q gains
model host R harmed
8.
Pia reads the table about a model parasite and its model host. Which partner is the host?
- R: the host is the partner that is harmed
- Neither: a host is a third kind of species
- Both: each partner is a host to the other
- Q: the host is the partner that gains
Removing one species from a model community of 12 species (model data)
species removed individuals of that species species left
A 500 11
B 40 5
9.
Tala reads the model data. Which removal changed the community more?
- Species A: it had the most individuals, 500
- Species A: 11 species were left, the larger number
- Neither: both removals changed the community the same way
- Species B: 7 species were lost, though it had fewer individuals
Species in a model stream community by year (model data)
year species
1 12
2 12
3 9
4 8
10.
Zee reads the model data. The banded tetra is absent from the start of year 3. How many fewer species are in year 4 than in year 2?
- 0 fewer: losing one species leaves the community as it was
- 1 fewer: 9 species in year 3 and 8 in year 4
- 3 fewer: 12 species in year 2 and 9 in year 3
- 4 fewer: 12 species in year 2 and 8 in year 4

partner	effect
fungus	gains
photosynthetic alga	gains

partner	effect
bird	gains
tree	unchanged

partner	effect
parasite	gains
host plant	harmed

species	individuals	share of the phosphorus supplied (percent)
banded tetra	30	95
stream snail	500	5

case	what happens
A	two plant species in one plot use the same limited supply of water, and both grow less
B	a bird builds a nest in a tree, and the tree stays the same

partner	effect
model parasite Q	gains
model host R	harmed

species removed	individuals of that species	species left
A	500	11
B	40	5

year	species
1	12
2	12
3	9
4	8

9th grade How relationships between species keep an ecosystem stable worksheet – printable — Print: 1 2 3 4 5 6

About this worksheet

How relationships between species keep an ecosystem stable: mutualism, commensalism, parasitism, competition, the lynx and hare cycle, and keystone species. Every version has 10 questions, and the answer key prints on the second page.

What your child will learn

I can name mutualism (both gain), commensalism (one gains, the other is neither helped nor harmed), parasitism (the parasite gains, the host is harmed) and competition (both use the same limited resource) from an effect table, a growth table or a short description.
I can say that a parasite's host is usually weakened and stays, because the parasite needs time to spread, and I can read that from host counts that fall slowly and stay above 0.
I can read two lines on one graph and say which peaks first, how many years later the second peak comes (the lag), and how many years one cycle lasts. I can use the lag and the cycle length to say when the next peak comes.
I can say that the lynx count follows the hare count, and I can find a notebook line that puts the lynx count first.
I can explain competitive exclusion: two species that need all the same resources cannot share a habitat for long, and one species' count can fall to 0 in a shared tube while both grow well alone. I can also say why using a different area, resource or time of day lets both species stay.
I can pick the keystone species from removal data by its effect on the other numbers, and not by its count. I can work out a percent fall in a nutrient level when a species is absent.

Standard: HS-LS2-6

Words to know

community: All the populations of different species that live in one habitat

symbiosis: Two species living close together for a long time

mutualism: A close partnership where both species gain

commensalism: A close partnership where one species gains and the other is neither helped nor harmed

parasitism: A close partnership where the parasite gains and the host is harmed

host: The living thing a parasite lives in or on

competition: Two species use the same limited resource, such as water, light or space

competitive exclusion: Two species that need all the same resources cannot share a habitat for long

Common mistakes

Your child gave the second partner a gain in commensalism. In commensalism one partner gains and the other is neither helped nor harmed. Ask your child, 'Does the second partner gain, lose or stay the same?'

Your child thought a parasite quickly removes its host. A host is usually weakened but stays, because the parasite needs time to spread to a new host. Ask your child, 'Does the host count really fall to zero in the data?'

Your child put the lynx count ahead of the hare count. The lynx count follows the hare count, peaking 1 to 2 years later. Ask your child, 'Which line peaks first?'

Questions parents ask

What is the most common mistake with how relationships between species keep an ecosystem stable?

Are these 9th grade science worksheets free to print?

Yes. All 6 printable versions at each level are free to print, with the answer key, and no account is needed.

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9th grade How relationships between species keep an ecosystem stable worksheet

Effects on the two partners in a lichen (data: OpenStax Biology)

Effects on a bird and the tree that holds its nest (data: OpenStax Biology)

Effects on a model parasite and its host plant (model data)

Two species in a model stream (model data)

Two cases of living things sharing a place (model data)

Effects on a model parasite and a model host (model data)

Removing one species from a model community of 12 species (model data)

Species in a model stream community by year (model data)