IB Environmental systems and societies Topic 2.1J Keystone Species Revision Notes (SL/HL)

IB Environmental systems and societies Topic 2.1J Keystone Species Revision Notes (SL/HL) | RevisionDojo

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Keystone Species: Small Presence, Outsized Impact

A keystone species has an effect on its ecosystem far larger than its abundance or biomass would suggest.
What defines a keystone species is this disproportionate impact relative to its abundance, not whether the species is common or rare.
Remove the keystone and the structure, diversity, and stability of the whole community can unravel.

Definition

Keystone species

A keystone species is an organism that has a disproportionately large impact on its ecosystem relative to its population size.

Key Characteristics: How to Spot a Keystone Species

Disproportionate influence: their impact far exceeds what their population size or biomass would predict.
Regulation of populations: they keep competitors, prey, or plants in check so no single species takes over.
Maintenance of biodiversity: by preventing domination, they sustain high species richness.
Habitat complexity: their feeding or behaviour creates varied niches for other organisms.
Stabilisation: they add to a community's resilience against disturbance.

Note

Keystone status is set by how large an effect a species has relative to its abundance, not by whether it is abundant or rare.
Some keystone species are fairly common and others are scarce, yet each punches well above its weight in shaping the community.
Do not treat being abundant as the defining trait; a numerous species is keystone only if its influence is out of proportion to its numbers.

Pisaster: A Keystone Predator (Paine 1966)

Location: rocky intertidal zones of the North Pacific coast.
Ecological role: the purple sea star (Pisaster ochraceus) is a predator keystone species.
Its key function is to eat mussels (Mytilus californianus) and stop them monopolising the rock.

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Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Keystone Species: Small Presence, Outsized Impact

A keystone species has an effect on its ecosystem far larger than its abundance or biomass would suggest.
What defines a keystone species is this disproportionate impact relative to its abundance, not whether the species is common or rare.
Remove the keystone and the structure, diversity, and stability of the whole community can unravel.

Definition

Keystone species

A keystone species is an organism that has a disproportionately large impact on its ecosystem relative to its population size.

Key Characteristics: How to Spot a Keystone Species

Disproportionate influence: their impact far exceeds what their population size or biomass would predict.
Regulation of populations: they keep competitors, prey, or plants in check so no single species takes over.
Maintenance of biodiversity: by preventing domination, they sustain high species richness.
Habitat complexity: their feeding or behaviour creates varied niches for other organisms.
Stabilisation: they add to a community's resilience against disturbance.

Note

Keystone status is set by how large an effect a species has relative to its abundance, not by whether it is abundant or rare.
Some keystone species are fairly common and others are scarce, yet each punches well above its weight in shaping the community.
Do not treat being abundant as the defining trait; a numerous species is keystone only if its influence is out of proportion to its numbers.

Pisaster: A Keystone Predator (Paine 1966)

Location: rocky intertidal zones of the North Pacific coast.
Ecological role: the purple sea star (Pisaster ochraceus) is a predator keystone species.
Its key function is to eat mussels (Mytilus californianus) and stop them monopolising the rock.

Definition

Paywall

(on a website) an arrangement whereby access is restricted to users who have paid to subscribe to the site.

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Note

Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam quis nostrud exercitation.

Excepteur sint occaecat cupidatat non proident

Tip

Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.
Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

IB Environmental systems and societies 2.1J Keystone Species Notes

Topic 1: Foundation 3 subtopics

Topic 2: Ecology5 subtopics

Topic 3: Conservation and biodiversity3 subtopics

Topic 4: Water4 subtopics

Topic 5: Land2 subtopics

Topic 6: Atmosphere and climate change4 subtopics

Topic 7: Natural resources3 subtopics

Topic 8: Human populations and urban systems3 subtopics

HL lenses 3 subtopics

Keystone Species: Small Presence, Outsized Impact

Key Characteristics: How to Spot a Keystone Species

Pisaster: A Keystone Predator (Paine 1966)

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account

Keystone Species: Small Presence, Outsized Impact

Key Characteristics: How to Spot a Keystone Species

Pisaster: A Keystone Predator (Paine 1966)

anim nostrud sit dolore minim proident quis fugiat velit et eiusmod nulla quis nulla mollit dolor sunt culpa aliqua

Duis aute irure dolor in reprehenderit

Excepteur sint occaecat cupidatat non proident

Unlock the rest of this chapter with a free account