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Evolution.pptx
- 3. Evolution • Evolution is the change in the characteristics of a species over several generations and relies on the process of natural selection. • The theory of evolution is based on the idea that all species are related and gradually change over time.
- 4. Evolution • Evolution relies on genetic variation in a population which affects the physical characteristics (phenotype) of an organism.
- 5. Theory of Natural Selection • English naturalist Charles Darwin developed the idea of natural selection after a five- year voyage to study plants, animals, and fossils in South America and on islands in the Pacific.
- 6. Theory of Natural Selection • Natural selection is the process through which populations of living organisms adapt and change. • Individuals in a population are naturally variable, meaning that they are all different in some ways. • Through this process of natural selection, favorable traits are transmitted through generations.
- 7. Theory of Natural Selection • Natural selection can lead to speciation, where one species gives rise to a new and distinctly different species. • It is one of the processes that drives evolution and helps to explain the diversity of life on Earth.
- 8. Theory of Natural Selection • Darwin chose the name natural selection to contrast with “artificial selection,” or selective breeding that is controlled by humans.
- 9. How Gene Frequencies Affects Evolution Synthetic Theory of Evolution • Described by Sewall Wright which attempts to explain evolution in terms of changes in gene frequencies. • This theory states that a species evolves when gene frequencies changes and the species moves it to a higher level of adaptation for a specific ecological niche.
- 10. How Gene Frequencies Affects Evolution • Example of this phenomena is the peppered moth in England.
- 11. How Gene Frequencies Affects Evolution • Because population changes require changes in gene frequencies, it is important to understand how these frequencies can change. • The three primary methods of change are mutation, migration and selection. Each will be considered individually.
- 12. Three primary methods of change in Genetic Frequency • Mutations are classified as beneficial, harmful or neutral. Harmful mutations will be lost if they reduce the fitness of the individual. If fitness is improved by a mutation, then frequencies of that allele will increase from generation to generation.
- 13. Three primary methods of change in Genetic Frequency • Migration, in a sociological context, implies the movement of individuals into new populations. In a genetic context, though, migration requires that this movement be coupled with the introduction of new alleles into the population. This will only occur after the migrant has successfully mated with an individual in the population. The term that is used to described this introduction of new alleles is gene flow.
- 14. Three primary methods of change in Genetic Frequency • Selection is a natural result of mutation is that new forms develop, and these new forms may or may not add to the fitness of the individual. If the fitness of the individual leads to a reproductive advantage then the alleles present in that individual will be more prevalent in the population.
- 15. Microevolution • Microevolution is simply a change in gene frequency within a population. Evolution at this scale can be observed over short periods of time — for example, between one generation and the next, the frequency of a gene for brown coloration in a population of beetles increases.
- 16. Mechanisms of Microevolution • There are a few basic ways in which microevolutionary change happens. Mutation, migration, genetic drift, and natural selection are all processes that can directly affect gene frequencies in a population.
- 17. Mechanisms of Microevolution • Mutation Some “green genes” randomly mutated to “brown genes” (although since any particular mutation is rare, this process alone cannot account for a big change in allele frequency over one generation).
- 19. Mechanisms of Microevolution Genetic drift • When the beetles reproduced, just by random luck more brown genes than green genes ended up in the offspring.
- 20. Mechanisms of Microevolution Natural selection • Beetles with brown genes escaped predation and survived to reproduce more frequently than beetles with green genes, so that more brown genes got into the next generation.
- 21. Adaptive Evolution • It pertains to evolutionary changes in an organism that make it suitable to its habitat. • The changes result in an increased chance of survival and reproduction. The changes enable the particular organism to fit to an environment. The changes are the organism’s adaptive traits and they arise as a result of natural selection
- 22. Speciation • Speciation is how a new kind of plant or animal species is created. • Speciation occurs when a group within a species separates from other members of its species and develops its own unique characteristics. • The demands of a different environment or the characteristics of the members of the new group will differentiate the new species from their ancestors.
- 23. Speciation • An example of speciation is the Galápagos finch. Different species of these birds live on different islands in the Galápagos archipelago, located in the Pacific Ocean off South America.
- 24. References • https://education.nationalgeographic.org/resource/natural- selection/ • https://www.yourgenome.org/facts/what-is-evolution/ • https://www.ndsu.edu/pubweb/~mcclean/plsc431/popgen/p opgen4.htm#:~:text=The%20synthetic%20theory%20of%20 evolution,for%20a%20specific%20ecological%20niche • https://education.nationalgeographic.org/resource/speciatio n/
Hinweis der Redaktion
- Species - a group of closely-related organisms that have common physical and genetic characteristics and are able to interbreed to produce fertile offspring.
- Genetic Variation - This is differences in DNA. Variation between individuals in their DNA is what makes them different. Some of these characteristics may give the individual an advantage over other individuals which they can then pass on to their offspring.
- In 1859, he brought the idea of natural selection to the attention of the world in his best-selling book, On the Origin of Species.
- This variation means that some individuals have traits better suited to the environment than others. Individuals with adaptive traits—traits that give them some advantage—are more likely to survive and reproduce. These individuals then pass the adaptive traits on to their offspring. Over time, these advantageous traits become more common in the population. Darwin did not know that genes existed, but he could see that many traits are heritable—passed from parents to offspring.
- Give examples about king cobra The king cobra (Ophiophagus hannah) is a venomous elapid snake species, endemic to South and Southeast Asia. It is sole member of the genus Ophiophagus.
- Several factors such as mutation of alleles and migration of individuals with those new alleles will create variation in the population. Selection will then chose the better adapted individuals, and the population will have evolved.
- The classic example which supports this theory is that of the peppered moth in England. The moth can be either dark or light colored. Prior to the industrialization of central England, the light-colored allele was most prevalent. The light-colored moths would hide on the white-barked trees and avoid bird predation. But the pollution generated by the new industries stained the light-colored trees dark. Gradually the light-colored moth was attacked and that allele became much less prevalent. In its place, the dark-colored allele became the most predominant allele because moths that carried that allele could camouflage themselves on the stained trees and avoid being eaten by their bird predators. Clearly the population had evolved to a higher adaptive condition.
- The mutation could be a change in one allele to resemble one currently in the population, for example from a dominant to a recessive allele. Alternatively, the mutation could generate an entirely new allele. Most of these mutations though will be detrimental and lost. But if the environment changes, then the new mutant allele may be favored and eventually become the dominant alelle in that population. If the mutation is beneficial to the species as a whole, migration from the population in which it initially arose must occur for it to spread to other populations of the species.
- The two effects of migration are to increase variability within a population and at the same time prevent a population of that species from diverging to the extent that it becomes a new species. The first effect is important because it provides the variability that a population will require to survive if the environment changes drastically. As migration continues over a period of time, the new mutation will be shared between populations. This blending effect helps stabilize the similarities between the population and prevent more isolated populations form evolving reproductive barriers that may lead to speciation.
- In this manner the alleles of this individual are selected. The process is called selection. In a Darwinian, context this is also called natural selection. The three forces that have been described lead to changes in gene frequencies within a population. But evolution, as defined by Darwin, is driven by natural selection.
- An example of adaptive evolution is the horse’s teeth. Its teeth are one of the traits that made it fit for a grass diet.