IB Environmental systems and societies Topic 2.1A Organisms Revision Notes (SL/HL)

IB Environmental systems and societies Topic 2.1A Organisms Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Species: The Basic Unit of Biodiversity

Ecology is studied at rising levels of organisation: individual, population, community, ecosystem, biosphere.
This article covers the individual and the species, the foundation on which every higher level is built.

What a Species Is: The Biological Species Concept

Definition

Species

A species is a group of organisms that can interbreed and produce fertile offspring under natural conditions.

Members of a species share a gene pool, so they can exchange genetic material through reproduction.
The most common definition is the Biological Species Concept (BSC), which sets three tests.
1. Interbreeding: members can reproduce with each other in nature.
2. Fertile offspring: their offspring can also reproduce.
3. Reproductive isolation: different species cannot naturally interbreed to produce viable, fertile offspring.

Example

A horse and a donkey produce a mule, which is sterile.
A lion and a tiger can breed, but their hybrid (a liger) is usually infertile, so they stay separate species.

Limitations of the Biological Species Concept

Geographically isolated populations may evolve apart yet still count as one species, so the test is hard to apply.

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Definition

Paywall

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

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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.

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Species: The Basic Unit of Biodiversity

Ecology is studied at rising levels of organisation: individual, population, community, ecosystem, biosphere.
This article covers the individual and the species, the foundation on which every higher level is built.

What a Species Is: The Biological Species Concept

Definition

Species

A species is a group of organisms that can interbreed and produce fertile offspring under natural conditions.

Members of a species share a gene pool, so they can exchange genetic material through reproduction.
The most common definition is the Biological Species Concept (BSC), which sets three tests.
1. Interbreeding: members can reproduce with each other in nature.
2. Fertile offspring: their offspring can also reproduce.
3. Reproductive isolation: different species cannot naturally interbreed to produce viable, fertile offspring.

Example

A horse and a donkey produce a mule, which is sterile.
A lion and a tiger can breed, but their hybrid (a liger) is usually infertile, so they stay separate species.

Limitations of the Biological Species Concept

Geographically isolated populations may evolve apart yet still count as one species, so the test is hard to apply.

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 2.1A Organisms 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: The Basic Unit of Biodiversity

What a Species Is: The Biological Species Concept

Limitations of the Biological Species Concept

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: The Basic Unit of Biodiversity

What a Species Is: The Biological Species Concept

Limitations of the Biological Species Concept

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