Evolution is a gradual process in which something changes into a different and usually more complex or better form whereas natural selection is the process in nature by which, according to Darwin's theory of evolution, only the organisms best adapted to their environment tend to survive and transmit their genetic characteristics in increasing numbers to succeeding generations while those less adapted tend to be eliminated.
HOW DOES EVOLUTION OCCUR?
Evolution is the change in frequency of the alleles in a gene pool over time. Evolution occurs with mutations and natural selections. WHat happens is that in a population of species, not all of them are the same. For example, there is a whole colony of fish. Some of the fish are faster than the others. They reproduce and pass on their genes which make their offspring fast as well. The other fish that aren't as fast, die out because they are not fast enough. The fast fish soon become more common, making the species as a whole faster. This occurs in several stages, where the slowest fish are removed each time, and the faster ones reproduce more often. The second aspect is that these fish will often have differences in their genetic codes, called mutations. While bad mutations will normally result in fatality and not get passed on, some are useful and result in increased survival. When these mutations build up, the species we previously had may then become completely different from what is here now. The two groups cannot cross breed, and have become different species.
WHAT TYPE OF EVOLUTIONARY EVENT HAS OCCURRED?
Natural selection and a genetic bottleneck. The DDT resistance is a classic example of natural selection, only the most resistant organisms surviving the treatment and establishing a new, resistant population. The near disappearance of the mosquito population for several years with the new population showing reduced fertility is characteristic of a genetic bottleneck. Only a very small number survived and the genetic diversity in the population is greatly reduced. The survivors are forced to undergo massive inbreeding and reduced fertility is quite common.
SUMMARY:
A recipe for life is raw materials, suitable environment, and energy sources. The conditions on early Earth made the origin of life possible. The chemical and physical conditions made abiotic synthesis of monomers (1st stage), formation of polymers (2nd stage), packaging of polymers into protobionts (3rd stage), and self-replication (4th stage.) In 1953, Stanley Miller tested the Oparin-Haldane hypothesis. He set up an airtight apparatus with gases circulating past an electrical discharge, to stimulate conditions on the early Earth. An alternative hypothesis states that submerged volcanoes and deep-sea hydrothermal vents may have provided the chemical resources for the first life. Cells and protobionts share four characteristics: structural organization, simple reproduction, simple metabolism, and simple homeostasis. The eukaryotic cell probably originated as a community of prokaryotes, when small prokaryotes capable of aerobic respiration or photosynthesis began living in larger cells. Oldest fossils of eukaryotes are about 2 billion years old. Sliding plates are earthquake zones. Also colliding plates form mountains. Those are geologic processes occur at plate boundaries. The supercontinent pangaea altered habitats and triggered the greatest mass extinction in Earth's history. Extinction is the fate of all species and most lineages. The history of life reflects a steady background extinction rate with episodes of mass extinction. Types of extinctions are classified by how shallow/deep water the species lived in. For example, permian extinction, cretaceous extinction.
Human development is paedomorphic, retaining juvenile traits into adulthood. In the evolution of an eye or any other complex structure, behavior, or biochemical pathway, each step must bring a selective advantage to the organism possessing it and must increase the organism's fitness. Other novel structures result from exaptation, the gradual adaptation of existing structures to new functions Natural selection doesn't anticipate the novel use: each intermediate stage must be adaptive and functional. Evolutionary trends do not mean that evolution is goal directed. Natural selection results from the interactions between organisms and their environment. If the environment changes, apparent evolutionary trends may cease or reverse. Systematics classifies organisms and determines their evolutionary relationship. Taxonomists assign each species a binomial consisting of a genus and species name. A phylogenetic tree is a hypothesis of evolutionary relationships within a group. Cladistics uses shared derived characters to group organisms into clades, including an ancestral species and all its descendents. Shared ancestral characters were present in ancestral groups. Molecular systematics compares nucleic acids or other molecules to infer related ness of taxa.
KEY TERMS:
- Macroevolution: major changes over evolutionary time
- Radiometric dating: measurement of the decay of radioactive isotopes
- Geologic record: defined by major transitions in life on Earth
- Continental drift: the slow, continuous movement of Earth's crustal plates on the hot mantle
- Adaptive radiation: a group of organisms forms new species, whose adaptations allow them to fill new habitats or roles in the communities
- Evo-devo: a field that combines evolutionary and developmental biology
- Homeotic genes: master control genes that determine basic features, such as where pairs of wings or legs develop on a fruit fly
- Species selection: the unequal speciation or unequal survival of species on a branching evolutionary tree
- Phylogeny: the evolutionary history of a species or group of species
- Convergent evolution: where analogous similarities result from in similar environments
This is a famous picture of evolution. It started out with the ape on the left, and ends with human being now on the right. It didn't happen just at once, but it took couple steps in between to become a human being from an ape. Also it took extremely long time. Like I said in the beginning, some apes who have different and better genes than others keep being alive, and other apes died out because of some reasons. And whoever that is still alive keep raising their children which are more likely to have "better" genes. This is how evolution occurs. This shows a microevlution.
http://www.youtube.com/watch?v=fVPadCMKJ_8
5 FACTS:
1) Homologous genes have been found in organisms separated by huge evolutionary distances
2) Molecular clocks help track evolutionary time. It can be calibrated in real time by graphing the number of nucleotide differences against the dates of evolutionary branch points known from the fossil record.
3) Life is divided into three domains: the prokaryotic domains Bacteria and Archaea and the eukaryote domain Eukarya.
4) There have been two major episodes of horizontal gene transfer, with transfer of genes between genomes by plasmid exchange, viral infection, and fusion of organisms: gene transfer between a mitochondrial ancestor and the ancestor of eukaryotes, and gene transfer between a chloroplast ancestor and the ancestor of green plants.
5) Shared characters are used to construct phylogenetic trees.
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