IB Biology D4.1 Notes

This page contains our IB Biology notes for D4.1. By reading each one of these notes, you will fully cover the content for IB Biology 'Natural selection'.

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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Criteria for natural selection

Previously, the concept of evolution and evidence supporting the theory was covered. This topic focuses on the process of evolution via natural selection.

Natural selection is the process by which an organism that is more adapted to its environment can survive, and so pass on the genes for its adaptation to its offspring. In order for this to occur, two criteria must be met:

There must be genetic variation within the population that causes different characteristics. These are caused by:
1. Mutation - to form new alleles.
2. Meiosis - to form new combinations of alleles via crossing over in prophase I or random orientation in prophase II.
3. Sexual reproduction - combining alleles from two individuals to form groups of alleles.
This variation must result in an adaptation. This is defined as a characteristic that make an organism suited to a particular way of life.

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