Evolution
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Transcript of Evolution
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EvolutionChapter 16
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Early Theory of EvolutionLamarck, a French biologist,
proposed:◦That body structures could change
according to the actions of the organism.
◦Acquired characteristics could be passed on to any offspring.
◦He was incorrect, but paved the way for Darwin.
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Developing the Modern Theory of Evolution
@Charles Darwin published ideas on how species evolved and they became the basis of modern evolutionary theory@; ◦He took a job as a naturalist on the HMS
Beagle where he traveled to South America and the Galapagos Islands collecting samples of specimens
◦He made many observation and after further experimentation he proposed the process of natural selection.
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Darwin’s observations:Finches and tortoises had
different beaks and shells/necks depending on diet.
However, all the finches and all the tortoises have many similar physical characteristics suggesting a common ancestor for each.
The differences in the finches and tortoises was due to adaptation to the food source.
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Natural Selection @Survival of the fittest, those
individuals better suited to survive@◦Darwin wrote “ On the Origin of
Species by means of Natural Selection”, after years of observations and studying evidence he collected on the mechanism of change.
4 principles of Natural Selection: Variation Heritability Overproduction Reproductive advantage
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Evolution@Is cumulative changes in
groups of organisms through time.@
Natural selection is not evolution but it is the mechanism by which it occurs.
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5 Types of Evidences of Evolution1. Fossils - Recorded for Earth’s
history.
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5 Types of Evidences of Evolution2. Anatomy
Homologous structures – Similar structures, Different use or function.
Analogous structures – different structure but are similar in function.
Vestigial structures – a body part structure that has no function in a present day organism but was useful to an ancestor. (ex human appendix)
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5 Types of Evidences of Evolution3. Chemistry – reveals
relationships between organisms, species, and individuals.
◦ Using RNA and DNA.
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5 Types of Evidences of Evolution4. Embryology – through
development of a tail and gill silts can be seen in embryos of birds, reptiles, and mammals.
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5 Types of Evidences of Evolution5. Distribution – geographical
distribution
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Extra Credit Question
What is this fish’s name and what TV show is it from?
Blinky. The Simpsons
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Adaptation@A trait shaped by natural
selection that increases an organisms reproductive success.@
Mimicry – is a structural adaptation that enables one species to resemble another; predator may avoid them if they look harmful.
Camouflage – an adaptation that enables species to blend with their surroundings.
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Population GeneticsPopulations evolve not
individuals.Natural selection acts on poor
phenotypes that will not benefit the survival of the organism.
Genes in the population are called gene pool.
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5 Mechanisms of Evolution
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5 Mechanisms of Evolution1. Genetic drift – change in
frequency of gene variations in a population. Founder’s effect reduction in alleles
resulting from a small group settling in a separate location away from the rest of the population.
Bottleneck effect is a reduction in alleles resulting from a chance event that drastically decreases population size.
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5 Mechanisms of Evolution2. Genetic flow – migrating
individuals transport genes.
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5 Mechanisms of Evolution3. Non-random mating –
organism mate with individuals in close proximity.
4. Mutation – change in genetic material.
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Extra Credit QuoteMutation, it is the key to our evolution. It has enabled us to evolve from a single-celled organism into the dominant species on the planet. This process is slow, and normally taking thousands and thousands of years. But every few hundred millennia, evolution leaps forward. –Professor X (X-Men 1)
Or-Dr. Jean Gray (X-Men 2)
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5 Mechanisms of Evolution5.Natural Selection acts on variation – “Survival of the fittest”
Types of Natural selection◦Stabilizing selection – favors average
individuals. ◦Directional selection – favors one extreme or
the other, example very large or very small. ◦Disruptive selection – favors individuals of
both extremes.◦Sexual selection – changes in frequencies of traits based on ability to attract mates.
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SpeciationSpeciation – evolution of new
species. Allopatric speciation – physical barrier
divides a population into 2 or more population.
Sympatric Speciation – a species evolves into a new species without physical barriers.
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Reproductive isolation occurs when formerly interbreeding organisms can no longer mate and produce fertile offspring.◦Prezygotic isolation – prevent fertilization
Geography Behavioral Mating time Physical differences
◦Postzygotic isolation – when fertilization occurs, prevent hybrid organism from reproducing. (sterility)
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Patterns of EvolutionAdaptive radiation (Divergent
evolution) – when ancestral species evolve into an array of species to fit number of diverse habitats. ◦patterns in which similar species
become increasingly different.
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Patterns of EvolutionConvergent evolution – patterns
of evolution in which distantly related organisms evolve similar traits.
Due similar environmental pressures.
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Rate of SpeciationGradualism is the idea
of that species originating through a gradual change of adaptation.
Punctuated equilibrium is rapid speciation, in burst with long periods of genetic equilibrium in between.