A4.1 Evolution and Speciation*

Evolution

cumulative change in the heritable characteristics of a population over time

3 factors defining an evolution

Changes must be passed on genetically from one generation to the next

If enough changes occur in a population, a new species can arise in a speciation split

Difference between original and new population mean they can no longer interbreed

6 steps Natural Selection

1. Organism are over reproduced leading to an increase in competition

2. Mutation creates genetic variation

3. Organisms with the advantageous alleles will be able to adapt the selection pressure

4. Organisms with the advantageous alleles will survive and reproduce

5. Passing on the advantageous alleles to the offspring

6. Increasing the advantageous allele frequency in the gene pool over generations

evolution evidence

genes and proteins

selective breeding

homologous structure

Genes and Proteins

DNA/RNA base sequence and amino acid sequence

Similarities and differences can show evolutionary relationships and common ancestry

the closer the evolutionary relationship the two species are, the fewer differences in their DNA/amino acid sequences.

Selective breeding of domesticated crop plants and animals

Organisms are selected to breed based on their desired features, and after repeating for several generations, yield a group of organisms with that specific feature.

It shows that artificial selection can cause evolution as it changes the features by keeping the desired allele

causing rapid evolution.

Homologous structures

those with similar anatomical position and structure, despite differences in function.

result of divergent evolution from a common ancestor.

eg, Pentadactyl limb

2 types of evolution

Divergent vs convergent evolution

Analogous characteristics

structures with a common function, but a different evolutionary origin

Speciation

The formation of a new species due to reproductive isolation

speciation occur through (speed)

gradual divergence over thousands of years

suddenly

Differential selection

the process where different environments impose different selective pressures on separate populations of the same species, causing them to accumulate distinct genetic differences over time.