1. Evidence of Evolution
1.1. Majority of the research to prove evolution comes from fossils. Dug up bones, shells and woods are evidence of evolution as they can be preserved for thousands - millions of years.
1.2. 4 pieces of evidence for evolution: 1.) Fossil evidence 2.) Anatomical and embryological evidence 3.) Biogeography 4.) Molecular evidence
1.2.1. 1.) Fossil evidence, remains of ancient animals and plants. Many gaps exist because it is difficult to find transitional fossils as only small proportion of organisms turn into fossils.
1.2.2. 2.) Anatomical and embryological, homologous structures is when similarities within species are inherited from common ancestors. Analogous structures are structures in different species that look alike or perform the same tasks for example wings. Embryology is the study of early, pre-birth stages of an organism development
1.2.3. 3.) Biogeography evidence, past and present geographical distribution of species, like the plate tectonics and the movement of continents since Pangaea
1.2.4. 4.) Molecular evidence, DNA carries genetic information and scientists compare DNA of 2 organisms to how they are related and if they find similar patterns or similarities within their DNA they become common ancestors
2. Origins of Earth
2.1. 1.) Actualism, slow process that occurred in the past and occurring in the present causes significant changes in landforms.
2.2. 2.) Uniformitarianism, the earth's surface has changed in the past, is changing in the present and will continue to change in the future in a very gradual way.
2.3. Origins of life on earth
2.3.1. Catastrophism, responsible for extinction of certain species and changes in organisms in an area
2.3.2. Spontaneous Generation, living thins can evolve from non-living matter.
2.3.3. Lamarck's theory, environment can cause change to a certain species
2.3.4. Darwin's Theory, species produce many more offspring that can survive, struggle for survival due to competition between individuals for food and resources. Individuals with the most favourable traits will survive to produce offspring.
3. Natural Selection
3.1. This theory has been invented by Charles Darwin, in the 1800 Darwin observed 3 different patterns to prove his theory of natural selection.
3.1.1. Natural Selection is based on Darwin’s theory of genetic variation - species vary within a given population, overproduction of offspring - when there is an overproduction of offspring there is also a struggle for survival therefore some can survive and pass on their genetic variation, struggle for existence - due to large population there is competition for food, space and mates. Differential survival and reproduction - survivors will reproduce and pass on their desirable traits
3.2. Individuals with heritable traits that favour survival results in a population that is better adapted to its current environment. Leads to evolution over time adaptations accumulate within species.
4. Mechanisms of Evolution
4.1. Genetic drift, change in allele frequency of a population by the chance of events like flipping a coin, this occurs when populations are small, reduces genetic variation and does not result is adaptation.
4.1.1. Genetic drift, the bottleneck effect occurs when a severe event causes reduction in population there fore a small sample of alleles survivors. Even if the sample population survives there will be decreased genetic variation.
4.1.1.1. Founder effect, genetic drift that occurs when few individuals invade a new area and establish a new population and could be due to bottleneck effect, this new group represents only a fraction of the allele pool of the original population this means the new population will contain less diversity of alleles.
4.2. Gene flow, due to migration of individuals or dispersal of seeds or spores, cause evolutionary change if there are differences in allele frequencies among populations. If gene flow occurs often this can prevent natural selection of particular alleles that are favoured in different environments because alleles keep mixing
4.3. Mutations, may occur in somatic or gamete cells. Mutations in gamete cells are passed on is called heritable mutations, causes alleles to change and even create a whole new allele. Can create dominant, recessive and co-dominant alleles, mutations can be harmful. lethal or not effective depending on the environment. Mutations are the only source of genetic variation.
4.4. Directional selection, individuals at one phenotypic extreme have an advantage to survive compared to all the other individuals, this results in deleterious genes decrease in frequency and others increase in frequency. This occurs when mutation gives a ride to a new gene and environment changes to select existing phenotype.
4.5. Disruptive selection, conditions select against individuals of an intermediate phenotype but extreme phenotype are the favourite, this is not common in nature.
4.6. Stabilizing selection, common phenotypes are favoured and both phenotypic extremes are deleterious. Over long periods of time new variations that form are unlikely to result in more fit phenotypes than ones that have been around for thousand of years.
4.7. Sexual selection, females select male to mate with which males compete with other males for female too mate with. Includes sexual dimorphism which is the different physical appearance between male and females, males may be brightly coloured.
5. Speciation
5.1. Species, population in which genes are actually or potentially exchange through interbreeding.
5.1.1. Polymorphism, different alleles within the same species. All members of the species can reproduce with one another, for example dogs.
5.2. Speciation is the formation of new species, requires that subpopulation are prevented from interbreeding (reproductive isolation). Initial gene flow within a single population to form sub-population. Then they isolate so that the 2 sub-population do not interbreed, prevents any further gene flow.
5.2.1. 2 types of reproductive isolation: 1.) Pre-zygotic isolation 2.) Post - zygotic isolation
5.2.1.1. 1.) Pre- zygotic isolation, prevents mating there is no encounter, and isolation by geography (rivers, mountains), ecology (habitat difference), time (seasonal or daily differences) and behaviour (mating signals).
5.2.1.2. 2.) Post- zygotic isolation, prevents successful developments of reproductive offspring.
5.3. Types of speciation, 1.) Allopatric 2.) Sympatric 3.) Peripatric 4.) Parapatric
5.3.1. 1.) Allopatric, is when sub-population isolate from one another. Adaptions occur to different environments or neutral selection such as genetic drift. Different phenotypes and genotypes emerge because of different select pressures, becomes so genetical different unable to reproduce.
5.3.2. 2.) Sympatric, within a single population many varieties in one range become species through adaptation to different aspects of range.
5.3.3. 3.) Peripatric, sub-population goes off in a small range geographically and the subpopulation is smaller than the original.
5.3.4. 4.) Parapatric, sub-population branches off but still is in the same area or space and the sub-population is more isolated.