The Blueprint Of Life

Evolutionary Change

A diverse variety of organisms have inhabited the earth
All organisms have many biochemical features in common suggesting a common ancestor
Competition for resources and changes in the physical and chemical environment influences the evolution of plants and animals
Throughout evolution, there have been many periods of mass extinctions followed by diversification of surviving populations

Evidence For Evolution

Biological evolution states that all organisms have developed from pre-existing organisms
The theory of evolution can be tested by examining fossils and comparing organisms to see whether predictions made from the theory hold true
The evidence for evolution include the following
Fossils
The fossil record, which shows change from simple organisms in the oldest rocks to more complex organisms in the youngest rock
Transition fossils which have characteristics of different groups of organisms and therefor suggest a common ancestry
Archaeopteryx
lobe fin fish
Similarity of fossils to present day organisms (e.g. horse-like fossils)
Comparative anatomy
Homologous structures demonstrate common ancestry.
Structures have similar anatomy but are adapted for a variety of functions
Biochemical similarity
All organisms share the same basic chemistry
Consist of organic substances
Use protein enzymes
Have similar cell membranes
Use a genetic code of DNA or RNA
Amino acid sequences of proteins are more similar among closely related organisms then less closely related organisms (e.g. cytochrome-c)
Embryology
The similarity or embryonic development suggests evolution from a common ancestor
Biogeography
The distribution of fossil and living plants and animals according to geographic regions is consistent with the theory that these organisms evolved from ancestral species within their geographic region

Natural Selection And Isolation

Darwin proposed the theory of evolution by natural selection. Natural selection was an explanation of how evolution could occur
The theory was based on the observations that many more offspring are produced than usually survive to reproduce considerable inheritable variations exist among organisms organisms are closely adapted to their environment many different species are very similar a variety of domestic breeds have been developed through careful and selective breeding these observations led Darwin to the conclusion that all members of a single species were not identical and some varieties would be more likely to survive and reproduce then others hence those organisms best adapted to their environment were more likely to survive and reproduce to pass on their characteristics to the next generation.
In this way, over many generations, species might change and become better adapted to their environment
Darwin’s theory of evolution by natural selection lacked an explanation of how new variations could arise within populations
Darwin’s theory of evolution by natural selection influenced society economics and religion
Isolation acts as a mechanism of evolution, allowing populations to evolve separately so that over a long time the separate populations no longer interbreed and thus become different species
Biologists continue to argue about the roles of different mechanisms of evolution. therefor present day mechanisms to explain the process of evolution are continually beng added to and refined
The Darwin/Wallace theory of evolution by natural selection and isolation accounts for adaptive radiation leading to divergent evolution and convergent evolution

Mendel: Ignored But Not Forgotten

Gregor Mendel developed much of the early knowledge of genetics from breeding experiments with peas
There are factors (now called genes) in living cells that control all living characteristics
Between one generation and the next, these genes segregate and they recombine in the cells of the next generation, but they do not merge they remain spate
Mendel was not