IB Environmental systems and societies Topic 3.1C Species Diversity Revision Notes (SL/HL)

IB Environmental systems and societies Topic 3.1C Species Diversity Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Species Diversity: Richness and Evenness Combined

Definition

Species diversity

Species diversity is the variety of species in an ecosystem, including both species richness (the number of species) and species evenness (the relative abundance of each species).

Species diversity is a key measure of biodiversity, set by species richness and species evenness.
Together these determine how balanced and functionally stable a community is.

The Two Components of Species Diversity

Species Richness

Definition

Species richness

Species richness is the total number of different species present in a community.

Species richness is a simple count of how many different species are present.
It shows variety but not how evenly individuals are spread among species.
Higher richness means more ecological roles and interactions.

Example

A coral reef with 100 fish species has higher richness than a lake with 10.

Species Evenness

Definition

Species evenness

Species evenness is the relative abundance of each species in a community.

Species evenness describes how uniformly individuals are distributed among the species.
High evenness, with similar population sizes, suggests a balanced, stable ecosystem.
Low evenness, where one or a few species dominate, suggests lower stability.

Example

A forest where tree species have similar population sizes has high evenness.
A forest dominated by one species has low evenness.

How Richness and Evenness Combine

High richness, low evenness (unstable)
1. Many species exist, but a few dominate.
2. The dominant species can outcompete others, causing imbalance.
Low richness, high evenness (limited but steadier)
1. Fewer species, in similar proportions, so none dominates.
2. More stable than a low-evenness system, but still vulnerable to disturbance.
High richness, high evenness (most resilient)

Nice try, unfortunately this paywall isn't as easy to bypass as you think. Want to help devleop the site? Join the team at https://revisiondojo.com/join-us. exercitation voluptate cillum ullamco excepteur sint officia do tempor Lorem irure minim Lorem elit id voluptate reprehenderit voluptate laboris in nostrud qui non Lorem nostrud laborum culpa sit occaecat reprehenderit

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

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 nisi ut aliquip ex ea commodo consequat.

Duis aute irure dolor in reprehenderit

Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.

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

Nemo enim ipsam voluptatem quia voluptas sit aspernatur aut odit aut fugit, sed quia consequuntur magni dolores eos qui ratione voluptatem sequi nesciunt. Neque porro quisquam est, qui dolorem ipsum quia dolor sit amet, consectetur, adipisci velit.

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 nisi ut aliquip ex ea commodo consequat.

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.

Unlock the rest of this chapter with a free account

Species Diversity: Richness and Evenness Combined

Definition

Species diversity

Species diversity is the variety of species in an ecosystem, including both species richness (the number of species) and species evenness (the relative abundance of each species).

Species diversity is a key measure of biodiversity, set by species richness and species evenness.
Together these determine how balanced and functionally stable a community is.

The Two Components of Species Diversity

Species Richness

Definition

Species richness

Species richness is the total number of different species present in a community.

Species richness is a simple count of how many different species are present.
It shows variety but not how evenly individuals are spread among species.
Higher richness means more ecological roles and interactions.

Example

A coral reef with 100 fish species has higher richness than a lake with 10.

Species Evenness

Definition

Species evenness

Species evenness is the relative abundance of each species in a community.

Species evenness describes how uniformly individuals are distributed among the species.
High evenness, with similar population sizes, suggests a balanced, stable ecosystem.
Low evenness, where one or a few species dominate, suggests lower stability.

Example

A forest where tree species have similar population sizes has high evenness.
A forest dominated by one species has low evenness.

How Richness and Evenness Combine

High richness, low evenness (unstable)
1. Many species exist, but a few dominate.
2. The dominant species can outcompete others, causing imbalance.
Low richness, high evenness (limited but steadier)
1. Fewer species, in similar proportions, so none dominates.
2. More stable than a low-evenness system, but still vulnerable to disturbance.
High richness, high evenness (most resilient)

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 3.1C Species Diversity 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

Species Diversity: Richness and Evenness Combined

The Two Components of Species Diversity

Species Richness

Species Evenness

How Richness and Evenness Combine

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

Species Diversity: Richness and Evenness Combined

The Two Components of Species Diversity

Species Richness

Species Evenness

How Richness and Evenness Combine

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