IB Environmental systems and societies Topic 3.1B Natural Selection and Speciation Revision Notes (SL/HL)

IB Environmental systems and societies Topic 3.1B Natural Selection and Speciation Revision Notes (SL/HL) | RevisionDojo

Written by official IB examiners

Natural Selection: The Driving Force of Evolution

Definition

Natural selection

Natural selection is the primary mechanism behind evolutionary change, shaping species over time and leading to the incredible biodiversity we see on Earth today.

Natural selection acts continuously on the genetic variation within a population, favouring traits that improve survival and reproduction.
Over millions of years, this process has produced the huge diversity of life across ecosystems.

Analogy

Natural selection works like quality control in nature.
Only the best-adapted designs keep being produced and refined over time.

How Natural Selection Works: Four Principles

Four linked principles drive evolution by natural selection: variation, overproduction, competition, and differential survival.

Exam technique

Show the full chain in exam answers: variation, then selection pressure, then differential survival, then inheritance, then evolution over generations.

Variation

Definition

Variation

Variation refers to the differences in traits among individuals of a population, resulting from genetic and environmental factors.

Individuals vary in their traits because of genetic differences and mutations.
This variation is the raw material for evolution, and it arises through mutation and sexual reproduction.

Example

In a rabbit population, genetic variation may produce fur colours ranging from white to dark brown.

Overproduction

Most species produce more offspring than the environment can support.
Only a fraction survive to adulthood, so those with advantageous traits are more likely to reach reproductive age.

Example

A pair of fish may lay hundreds of eggs, but only a few survive predation and competition to reach adulthood.

Competition and the Struggle for Survival

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Definition

Paywall

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Note

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Excepteur sint occaecat cupidatat non proident

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Tip

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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.
Duis aute irure dolor in reprehenderit in voluptate velit esse cillum.

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Natural Selection: The Driving Force of Evolution

Definition

Natural selection

Natural selection is the primary mechanism behind evolutionary change, shaping species over time and leading to the incredible biodiversity we see on Earth today.

Natural selection acts continuously on the genetic variation within a population, favouring traits that improve survival and reproduction.
Over millions of years, this process has produced the huge diversity of life across ecosystems.

Analogy

Natural selection works like quality control in nature.
Only the best-adapted designs keep being produced and refined over time.

How Natural Selection Works: Four Principles

Four linked principles drive evolution by natural selection: variation, overproduction, competition, and differential survival.

Exam technique

Show the full chain in exam answers: variation, then selection pressure, then differential survival, then inheritance, then evolution over generations.

Variation

Definition

Variation

Variation refers to the differences in traits among individuals of a population, resulting from genetic and environmental factors.

Individuals vary in their traits because of genetic differences and mutations.
This variation is the raw material for evolution, and it arises through mutation and sexual reproduction.

Example

In a rabbit population, genetic variation may produce fur colours ranging from white to dark brown.

Overproduction

Most species produce more offspring than the environment can support.
Only a fraction survive to adulthood, so those with advantageous traits are more likely to reach reproductive age.

Example

A pair of fish may lay hundreds of eggs, but only a few survive predation and competition to reach adulthood.

Competition and the Struggle for Survival

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 3.1B Natural Selection and Speciation 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

Natural Selection: The Driving Force of Evolution

How Natural Selection Works: Four Principles

Variation

Overproduction

Competition and the Struggle for Survival

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

Natural Selection: The Driving Force of Evolution

How Natural Selection Works: Four Principles

Variation

Overproduction

Competition and the Struggle for Survival

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