Evidence for evolution

Evolution definition

The change in heritable characteristics of a population over time

Lamarkism

• Evolution based on inheritance of acquired characteristics

• Characteristics of individuals can change over time = acquired characteristics

Darwinian

• Characteristics of population change over time = evolution

• Evolution concerns heritable characteristics

• Mechanism = natural selection

Evolution by natural selection

• Changes in characteristics that are not inherited, do not lead to evolution

• Heritable characteristics are determined by the alleles of genes that are present in an individual

• Alleles may change because of random mutation, causing them to become more or less advantageous

• Heritable characteristics that are advantageous are more likely to be passed on to offspring, leading to a gradual change in a species over time

Evolution evidence

• DNA / RNA

• Selective breeding

• Homologous structures

• Analogous structures

• Speciation

• Fossils

Selective breeding

Process where humans breed plants or animals with desired characteristics

Process of selective breeding

• Selection of desired characteristics by humans

• Cross breeding of male and female with desired characteristic

• Selection of offspring showing desired characteristic

• Repeating the process over many generations until allele for desired characteristic increases in frequency.

Homologous structures

• Anatomical features that are similar in basic structure but are used in different ways

• Illustrate adaptive radiation, where new species rapidly diversify from the same ancestor to utilise a specific niche

• E.g. pentadactyl limb

Analogous structures

• Have the same function but derive from different ancestors

• Result of convergent evolution, occurs when distantly related species live in habitats with similar selection pressures, so similar characteristics provide survival advantage

• Evidence for passing on of advantageous characteristics during natural selection