Evolution

1. Evolution By Simone Badiu

2. In 1858, Charles Darwin and Alfred Russell Wallace put forward a theorum stating that evolutionary changes are a result of organisms adapting to their environment to survive and produce more offspring. This is referred to as “natural selection”.

3. Natural Selection has 4 basic steps: • One: There are variations in the genes carried by individuals. • Two: Environmental pressures select some individuals and reject others. • Three: The best adapted individuals have the genes that allow them to survive the environmental pressures. • Four: Genes are passed on to many generations. • Charles Darwin and Alfred Russell Wallace (1858) • Who were the two scientists who first proposed evolution through natural selection?

4. Fossils are traces of a once living organism.They may be parts of plants or animals, or the traces that they left e.g. dinosaur footprints or the tubes left by worms.Through the study of fossils, Scientists can study how Organisms have changed over time, finding evidence supporting the theory of natural selection.

5. Fossils are formed in sedimentary rocksThis is the process in which they formed:

6. Fossils need to be dated to accurately provide evidence of natural selection • Fossils are usually found in sedimentary rocks. • The age of rocksare determined using radioactive dating. • The age of rocks can also be determined by correlating the fossils found in them with rocks of known age. • The relative age of sedimentary rocks can be deduced by making the assumption that younger sedimentary rocks are above older sedimentary rocks (assuming no geological upheavals have occurred).

7. Transitional Forms • Fossils have been found which appear to have the characteristics of two different groups of organisms. • These fossils are called transition fossils. • The evolution from ancient reptiles to mammals is well documented by a series of transition fossils. A famous transition fossils are archaeopteryx, which provides evidence for the common ancestry of birds and reptiles.

8. Homologous Structures • Homologous structures are structures found in plants or animals that have the same origin, but not necessarily exactly the same form or the same function. • The development of homologous structures is an example of divergent evolution. Divergent evolution occurs when a number of species develop from one common ancestor, becoming less and less alike over time due to their different habitats. • The pentadactyl limbs of vertebrate animals (mammals, reptiles and amphibians) are examples of homologous structures. All of these groups have limbs with five digits (finger-like structures) which have the same basic structural plan, but have altered (adapted) to differentenvironments and ‘life-styles’ (i.e. different methods of locomotion, feeding, etc). • This suggests that all of these groups of animals originated from some original group of animals (the “common ancestor”).

9. Bio geography • Biogeography is the study of living things in relation to geographical regions. At one stage, the earth was one super continent – Pangea, then animals were separated, over time evolving due to the pressure of different habitats.An example of this is flightless bird (emu, ostrich etc.) This proves that natural selection is in action everyday, providing evidence that evolution is real.

10. Comparative Embryology • The comparison and contrasts embryos of different species to show how all animals are related and were adapted over time as a result of environmental pressure. (example human vs. rabbit).

11. Comparative DNA • DNA and other biochemical evidence can be used to check the accuracy of evolution. By comparing the proteins molecules from DNA we can see if species evolve from a common ancestor. The number of differences is proportional to the time since they have been separated and thus adapting as a result to change in climate.