Charles darwin

Charles Darwin

1. all species are descended from ancestral species

2. mechanism that drives changes in species is natural selection

What is natural selection

Individuals with traits best-suited to survive in their environment will out-survive those less suited; therefore, the most useful traits will be passed on

Natural selection AKA survival of the fittest

• Individuals with traits best-suited to survive in their environment will out-survive those less suited;

• therefore, the most useful traits will be passed on

What are the three main factors

• Struggle for existence

• Natural variation

  • Role of the environment

Struggle for existence

• tendency of species to produce more offspring than environment can support direct competition among members in a species

Natural variation

differences among members of same species (heritable)

Role of the environment

selects individuals with adaptations best-suited for the environment

Pieces of evidence to support evolution as a theory

• Fossil record

• Geographical distribution

• Comparative anatomy

Fossil record

• fossils embedded in layers of rock strata tell approximate age

Geographical distribution

• Closely related but different

  • Distantly related, but similar

Closely related but different

descendants of a single ancestral species living in different habitats pass on adaptations best-suited to that habitat

Distantly related but similar

descendants of different ancestral species living in similar habitats pass on similar adaptations

Biogeography

the observed geographic patterns of distribution of species

– Based on living and fossilized species

• Darwin – found “unusual” animals on Galapagos!

Comparative anatomy

• Homologous structures

• Analogous structures

• Vestigial organs

Homology

Similarity in characteristics resulting from common ancestors is known

Homologous structure

• structure of an organism that is similar in structure, function, or both

• can different functions in different organisms

Similarity in 1 or more body parts in different organisms

descent from a common ancestor

Analogous features

• Evolved independently to have the same function

• Suggests distant evolutionary relationship

Example of analogous features

Eyes/wings of insect vs. eyes/wings of birds

Analogous structures

have similar functions/superficial appearance but very different anatomy

Similarities is analogous structures are there because of

due to similar selective pressures but do not demonstrate any recent common ancestry

Vestigial organs

• structures with no current function, but which are homologous to functional structures in related organisms

  • Historical remnants of structures that HAD important functions in ancestors

Psuedogenes

Genes that have undergone mutation and no longer serve a purpose

Fossil record

Preserved organisms of the past

•When fossils are arranged in order of their age, a progressive series of change can often be seen

• Although sometimes incomplete, provides very good evidence

Comparative embryology

Closely related organisms go through similar stages in their embryonic development

– all vertebrate embryos go through a stage in which they have gill pouches on the sides of their throats