understanding checkpoint
keystone species

1. keystone species are critical to the functioning of an entire ________.
2. keystone species hold the entire food ________ in balance.
3. which is an example of a keystone species?
a. otters b. sea stars
b. beavers d. all of these
4. a keystone species has...
a. a big impact on ecosystem and is a large population.
b. a small impact on ecosystem, but is a small population.
c. a big impact on ecosystem and is a small population.
d. none of these.
5. bees considered a keystone species because ______.
a. they make supports the bear population
b. they pollinate flowers that produce fruit which supports the ecosystem
c. they sting when threatened
d. they live in hives
6. which is not true of a keystone species?
a. they hold an ecosystem together.
b. they are not always the largest or most abundance species in an ecosystem.
c. another species is able to take over its role in an ecosystem when it is removed.
d. they are typically predators.
7. what is a keystone host?
a. a species that can maintain healthy populations despite being preyed upon
b. a species that transfers nutrients from one habitat to another
c. an organism that helps define an entire ecosystem
d. plants and other producers that provide food and shelter for keystone species
8. true or false: keystone species are always predators.
9. true or false: only animals and plants be keystone species.
10. circle the organism in this food web that you expect to be the keystone species.

name yosef s.
date 9/
period 7-3

Question

understanding checkpoint
keystone species

1. keystone species are critical to the functioning of an entire ________.
2. keystone species hold the entire food ________ in balance.
3. which is an example of a keystone species?
   a. otters  b. sea stars
   b. beavers  d. all of these
4. a keystone species has...
   a. a big impact on ecosystem and is a large population.
   b. a small impact on ecosystem, but is a small population.
   c. a big impact on ecosystem and is a small population.
   d. none of these.
5. bees considered a keystone species because ______.
   a. they make supports the bear population
   b. they pollinate flowers that produce fruit which supports the ecosystem
   c. they sting when threatened
   d. they live in hives
6. which is not true of a keystone species?
   a. they hold an ecosystem together.
   b. they are not always the largest or most abundance species in an ecosystem.
   c. another species is able to take over its role in an ecosystem when it is removed.
   d. they are typically predators.
7. what is a keystone host?
   a. a species that can maintain healthy populations despite being preyed upon
   b. a species that transfers nutrients from one habitat to another
   c. an organism that helps define an entire ecosystem
   d. plants and other producers that provide food and shelter for keystone species
8. true or false: keystone species are always predators.
9. true or false: only animals and plants be keystone species.
10. circle the organism in this food web that you expect to be the keystone species.

name yosef s.
date 9/
period 7-3

Accepted Answer

### Question 6
# Brief Explanations:
To determine which statement about keystone species is not true, we analyze each option:
- Option a: Keystone species are critical for ecosystem function, so they "hold an ecosystem together"—this is true.
- Option b: Keystone species don’t need to be the largest or most abundant—this is true (e.g., sea otters in kelp forests).
- Option c: If a keystone species is removed, no other species can typically take over its unique role (they have a disproportionate impact). So this statement is false.
- Option d: Many keystone species are predators (e.g., wolves, sea stars)—this is true.

# Answer:
c. Another species is able to take over its role in an ecosystem when it is removed.

### Question 7
# Brief Explanations:
A keystone host is a species (often plants or organisms) that provides essential resources (food, shelter) for other species, defining the ecosystem. Let’s analyze:
- Option a: Describes prey with healthy populations, not a keystone host.
- Option b: Describes nutrient transfer (not host - related).
- Option c: Describes a general keystone species, not a host.
- Option d: Plants/producers that provide food/shelter for keystone species (or others) fit the "host" role (e.g., oak trees as keystone hosts for many species).

# Answer:
d. plants and other producers that provide food and shelter for keystone species

### Question 8
# Brief Explanations:
Keystone species are not always predators. For example, beavers (engineer ecosystems), bees (pollinators), and some plants are keystone species but not predators. So the statement "Keystone species are always predators" is false.

# Answer:
False

### Question 9
# Brief Explanations:
Keystone species can include non - animal/plant organisms. For example, certain fungi (mycorrhizal fungi) or even bacteria can be keystone species by influencing nutrient cycles or symbiotic relationships. So the statement "Only animals and plants can be keystone species" is false.

# Answer:
False

### Question 3
# Brief Explanations:
- Otters: Sea otters are keystone species (control urchin populations, maintain kelp forests).
- Sea stars: Pisaster ochraceus (sea star) is a classic keystone predator (controls mussel populations).
- Beavers: Engineer ecosystems (create wetlands, affecting many species).
Since all (otters, sea stars, beavers) are keystone species, the answer is "all of these".

# Answer:
d. all of these

### Question 4
# Brief Explanations:
Keystone species have a large impact on the ecosystem but often have a small population (disproportionate impact).
- Option a: Wrong (they don’t need a large population).
- Option b: Wrong (impact is big, not small).
- Option c: Correct (big impact, small population).
- Option d: Wrong (option c is correct).

# Answer:
c. a big impact on ecosystem and is a small population.

### Question 5
# Brief Explanations:
Bees are keystone species mainly because they pollinate flowers. Pollination allows flowers to produce fruit/seeds, supporting many species in the ecosystem.
- Option a: Irrelevant to bear populations.
- Option b: Correct (pollination supports ecosystem - level food webs).
- Option c: Stinging is a defense, not a keystone role.
- Option d: Living in hives is a behavior, not a keystone role.

# Answer:
b. they pollinate flowers that produce fruit which supports the ecosystem

### Question 1
# Brief Explanations:
Keystone species are critical to the functioning of an entire **ecosystem**. Their removal or decline can cause drastic changes to the ecosystem’s structure and species composition.

# Answer:
ecosystem

### Question 2
# Brief Explanations:
Keystone species hold the entire food **web** in balance. Food webs represent the complex interconnections of feeding relationships in an ecosystem, and keystone species regulate these relationships (e.g., controlling prey populations to prevent overgrazing/overpopulation).

# Answer:
web

### Question 10
(Note: Since the food web image is partially visible, we assume a typical aquatic food web. In many aquatic food webs, a top predator (e.g., the heron, or a fish) or a key producer (e.g., algae) could be the keystone species. If we assume a predator - based keystone (common in such webs), the heron (or a top - level fish) might be the keystone. However, without full visibility, we can infer: In a food web with a heron, fish, and smaller organisms, a top predator (like the heron) or a species that controls a lower trophic level (e.g., a fish that controls prey) could be keystone. If we circle the heron (the large bird at the top), it could be a keystone predator controlling fish populations, which in turn control smaller organisms, maintaining the web. )

# Brief Explanations:
In the given food web (with a heron, fish, and other aquatic organisms), a keystone species is likely a top predator (e.g., the heron) or a species with disproportionate impact. The heron (or a key fish) controls lower - level populations, so we circle the heron (or the relevant top - level organism) as the keystone species.

# Answer:
(Assuming the heron is the keystone - like organism in the food web) Circle the heron (the large bird - like organism in the food web diagram).

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