Evolution - created from Mind Map

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Theories of evolution

Speciation

Evidence for Evolution

Phylogenetic Trees

Natural Selection

Lamarck

Darwin

Modern theory of evolution

Characteristics were inherited by subsequent generations

Characteristics within populations change overtime

Characteristics were acquired by organisms as the need arose e.g. Giraffes necks

Evolution by natural selection

Inheritance of acquired characteristics = genes given to offspring

Reproduction

Excess potential offspring

Variation

Selection

Adaptation overtime

Chance effects

Divergence of speciation

Biological species concept

Reproductive isolation

Allopatric speciation

Sympatric speciation

A species is a group of populations whose members can breed and produce viable, fertile offspring

Ability to mate = formation of a species

Gene flow between populations holds together the phenotype of a population (ongoing exchange of alleles)

The existence of biological factors (barriers) that prevent two individuals of a species from mating and producing viable and fertile offspring

A population forms a new species while geographically isolated from its parent population

A subset of a population forms a new species without geographic seperation

The Fossil Record

Transitional fossils

Comparitive anatomy and embryology

Biogeographical distribution

Comparative biochemistry

Fossils are evidence of organisms that lived on earth in the geological past

Organisms die - fossilisation: organisms are compressed under layers of sediment and their tissues are replaced with carbon film, or minerals

Types of fossils

Mould: dead organism is covered by sediment, they later form sandstone or mudstone, the organism decays and leaves a cavity.

Cast: formed when the cavity within a mould is filled by other material, forming a 3D model

Trace fossils: indirect evidence of past living things. E.g. footprints, teeth marks, nests.

Intermediate forms: if a new species arises from an old by evolution, fossil records should reveal fossils that are intermediate between forms e.g. birds are believed to have evolved from a group of reptiles

Homologous structures: mammals are related by evolution from a common ancestor - shared similarities in structrue regardless of their way of life

Analogous structures: carry out similar functions but are not necessarily similar in basic structures

Vestigial organs: functionless and reduced remnants of organs that were present and functional in their ancestors

Comparing embryos

Divergent evolution: occurs when one ancestral species change over geological time to give rise to many new species

Convergent evolution: natural selection may act on distantly related species to produce superficial similarities that are not due to a shared ancestry - rather the species are adapted to a similar niche

Species living in similar environments but in geographical regions that have been seperated for tens of millions of years may show similarities in appearance

comparing species on basis of proteins, DNA and chromosomes

shows seperation of gene pools and the relative age of these seperations

organisms related by evolution should show similarities in their molecular composition

A phylogenetic tree is based ont he sharing of homologous features - summary diagram showing how organisms are related and how they have diverged during evolution

Overproduction

Variation

Competition

Survival of the fittest

Favourable traits become more common

When a species produces more young than will survive to reproductive age

Individuals varying in many characteristics where some variations are better suited to the conditions of the time than others

Where there is competition for limited resources such as food

Where the individuals with the most favourable combinations of chracteristics will be most likely to survive and pass on their genes to the next generation

Where each new generation will contain proportionately more descendants of individuals with favourable characteristics