IB Biology Evolution and Speciation A4.1

Evolution

the cumulative change in the inheritable characteristics of a population.

a result of natural selection acting on genetic variation.

Heritable characteristics

characteristics that are capable of being passed from one generation to the next through the genes.

Homologous structures

anatomical structures derived from a common ancestor, but evolved to serve different purposes.

Recent common ancestor.

eg. pentadacty limb - wing, hand, and hoof.

Pentadactyl limb

a limb with five digits

eg. human hand or foot,

in many amphibia, reptiles, birds, and animals,

--> all these species derived from common ancestor.

Population

a group of organisms of one species that interbreed and live in the same place at the same time

Selective breeding

the intentional breeding of organisms with desirable traits in an attempt to produce offspring with similar desirable characteristics or with improved traits.

Species

same characteristics and capable of mating to produce fertile offspring.

Adaptations

a feature of an organism that favours its survival to reproductive age.

can be behavioural, physiological, or structural.

Natural selection

The mechanism of evolution in which various genetic types make different contributions to further generations.

- Populations are generally stable despite large number of offspring.

- Better adapted individuals have a competitive advantage.

- There's heritable variation within species

- Advantageous traits becomes more frequent over generations

Selection pressure

an environmental variable that acts to remove poorly adapted individuals.

Analogous Structures

trait structures which are similar because of convergent evolution.

- two separate species develop similar features, but not from a common ancestral form.

- usually similar function but different structure.

eg. the eye.

Convergent evolution

where species from different lineages show similar characteristics because they are subject to similar selection pressures.

analogous trait

structures which are similar because of convergent evolution.

DNA and Protein Structures

- All living organisms have the same 4 DNA bases

- Proteins are built up of amino acids

--> only 20 amino acids in living organisms

- evidence of common ancestors

- study of genetic code and amino acids can help with links into relatives/clades

- increased similarity = more closely related.

eg. Cytochrome C in the mitochondria.

Theory

well-tested explanation that unifies a broad range of observations

Darwin

English natural scientist who formulated a theory of evolution by natural selection (1809-1882)

Lamark

inheritance of acquired characteristics

Common ancestor

An ancestral species from which later species evolved

Speciation

the evolution of new species

Extinction

A term that typically describes a species that no longer has any known living individuals.

reproductive isolation

Separation of populations so that they cannot interbreed and produce fertile offspring

Geographical isolation

form of reproductive isolation in which two populations are separated physically by geographic barriers such as rivers, mountains, or stretches of water