IB Biology Topic 4 Notes

This page contains our IB Biology notes for topic 4. By reading each one of these notes, you will fully cover the content for IB Biology 'Ecosystems'.

All Topic 4 Sub-topics A4.1: Evolution & Speciation (HL)A4.1: Further speciation A4.2: Conservation Of Biodiversity B4.1: Adaptations B4.2: Ecological Niches C4.1: Populations & Communities C4.2: Energy & Matter Transfer D4.1: Natural Selection (HL)D4.1: Further natural selection D4.2: Stability & Change (HL)D4.2: Ecological stability D4.3: Climate Changes (HL)D4.3: Further climate change

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Chapters

A4.1: Evolution & speciation

1. Evolution

2. Base sequences

3. The Fossil record

4. Selective breeding

5. Homologous structures

6. The Pentadactyl limb

7. Speciation

8. Bonobos

A4.1: Further speciation (HL)

1. Speciation

2. Adaptive radiation

3. Hybridization

A4.2: Conservation of biodiversity

1. Biodiversity

2. Mass extinction events

3. Ecosystem loss

4. Biodiversity crisis

5. Conservation of biodiversity

6. EDGE of existence program

B4.1: Adaptations

1. Habitats

2. Adaptations

3. Species distributions

4. Transects

5. Coral reef formation

6. Biomes

7. Adaptations To Biomes

B4.2: Ecological niches

1. Niches

2. Aerobes and anaerobes

3. Modes of nutrition

4. Hominids

5. Herbivory adaptations

6. Predation adaptations

7. Light adaptations

8. Realised niches

C4.1: Populations & communities

1. Populations

2. Population size estimation

3. Population dynamics

4. Competition and cooperation

5. Community interactions

6. Mutualism

7. Predation

8. Competition

9. Testing competition

C4.2: Energy & matter transfer

1. Ecosystems

2. Food webs & chains

3. Modes of nutrition

4. Trophic levels

5. Heat loss

6. Pyramids of energy

7. Pyramids of biomass

8. Primary production

9. Secondary production

10. The Carbon cycle

11. Negative carbon fluxes

12. Carbon conversion

13. Positive carbon fluxes

14. The Keeling curve

D4.1: Natural selection

1. Criteria for natural selection

2. Sequence of natural selection

3. Sexual selection

4. Modelling of selection

D4.1: Further natural selection (HL)

1. Gene pool

2. Genetic equilibrium

3. Hardy-Weinberg conditions

4. Artificial selection

D4.2: Stability & change

1. Ecosystem stability

2. Amazon deforestation

D4.2: Ecological stability (HL)

1. Succession

2. Primary succession

3. Cyclical succession

4. Arrested succession

D4.3: Climate changes

1. Climate change

2. Global warming

3. Boreal forests

4. Land fast ice and sea ice

5. Oceanic currents

6. Species migration

7. Coral reefs

8. Carbon sequestration

D4.3: Further climate change (HL)

1. Phenology

2. Tawny owls

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Evolution

Topic 4 focuses on ecosystems and changes within them. In the context of organisms, the changes they undergo are mostly due to evolution. This is the change in heritable characteristics of a species over time.

Given evolution's previously controversial history since its proposition of theory in the mid 19th-century by Charles Darwin and Alfred Russel Wallace, it is important to understand the process.

The theory of evolution by natural selection is governed by four tenets:

More offspring are produced than can survive.
Morphology, physiology, and behavior greatly varies between individuals.
Different traits results in different rates of survival and reproduction.
Traits are passed down generations.

The evidence for evolution is provided by several key pieces of information, including:

Base sequences
The fossil record
Selective breeding
Homologous structures

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