Theodoslus Dobzhansky: Integrating Genetics and Evolution A Russian geneticist who moved to the United States, provide laboratory evidence for natural selection and variation where previously there had been only field observation. Dobzhansky’s work with Drosophila, or fruit flies, provided new evidence that supported Darwin’s theory that natural selection, acting on genetic variation in populations , is a driving force in evolution.

History of Evolutionary Thought Lamarck (early 1800’s) was one of the first scientists to propose that species can change. Proposed that individuals could change their physical appearance through use or disuse of a body part. He then went to say that these changes could be passed down to the next generation.

Lamarck’s evidence and inference Use and disuse Inheritance of acquired characteristics Comparisons between current species and fossils: lines of descendents

Charles Darwin 1809 – 1882 British Naturalist Proposed the idea of evolution by natural selection Collected clear evidence to support his ideas.

Voyage of the HMS Beagle 1831 – 1836 Travels around the world Makes many observations of natural world Main mission of the Beagle was to chart South American coastline

What Darwin saw During the voyage Darwin spent as much time on land as possible collecting specimens. Once he returned and was able to look closely at his specimens he noticed many similarities and differences. Most interesting were his specimens from the Galapagos Islands.

Darwin’s Finches Darwin discovered 13 species of finches on the small islands. Only 1 species on South American mainland Must have originated from South America!

Finches Darwin presumed that the finches originated from the mainland.

Finches Darwin presumed that the finches originated from the mainland.

Finches Darwin presumed that the finches originated from the mainland.

Finches Darwin presumed that the finches originated from the mainland.

Finches Darwin presumed that the finches originated from the mainland. Once on the island, they were able to take advantage of habitats that weren’t available on the mainland.

Natural Selection

Natural Selection Natural selection says that the “fittest” individuals in a group are the ones that survive and REPRODUCE to pass on their genes.

Originally, the vast majority of peppered moths (Biston betularia) had a light, mottled coloring which was a good camouflage against predators. Before the industrial revolution, a uniformly dark variant of the peppered moth made up 2% of the species. The Peppered Moth

Originally, the vast majority of peppered moths (Biston betularia) had a light, mottled coloring which was a good camouflage against predators. Before the industrial revolution, a uniformly dark variant of the peppered moth made up 2% of the species. After the industrial revolution, 95% of peppered moths showed this dark coloration. The best explanation as to why this change in the species occurred is that the light moths lost their advantage of camouflage as light surfaces were darkened by pollution, and so light moths were eaten more frequently by birds. The Peppered Moth

What makes an organisim more “Fit” An organism is more fit if it is able to reproduce more than other individuals. Better suited to it’s environment, able to avoid predators, able to find more food, etc. These differences are caused by natural variations in the DNA!

Descent with Modification Descent with Modification: says that newer forms of organisms are really modified descendants of older species. He then went on to say all species are descendants of one or a few original species.

End of Day 2 Slide Show

Theodoslus Dobzhansky: Integrating Genetics and Evolution A Russian geneticist who moved to the United States, provide laboratory evidence for natural selection and variation where previously there had been only field observation. Dobzhansky’s work with Drosophila, or fruit flies, provided new evidence that supported Darwin’s theory that natural selection, acting on genetic variation in populations , is a driving force in evolution.

Evidence Supporting Evolution

Where to find evidence? Evidence can be found many places, mostly in natural world. Comparing structures in living organisms Comparing embryos of organisms Comparing molecules in organisms Fossil Record

Comparing Structures Many organisms have structures that are similar, but serve different purposes. The forelimbs of the organisms below have very similar bone structures, but they serve different purposes. These are called: Homologous structures

Comparing Structures con’t Many organisms have evolved DIFFERENT structures that do serve the SAME function. These are called Analogous Structures: EX: Fish Fins and Dolphins fins. Both serve the purpose of helping stabilize when swimming. Are structured differently. Are not closely related.

Structures Continued Vestigial Strucutres These are structures in an organism that serve no purpose. EX: Humans appendix Tail bone Do not provide any advantage, but do not create a disadvantage.

Vestigial Structures Continued Whales have bones which at one point in time were part of a pelvis and legs. Currently serve no purpose Ancestors used to live on land. Pelvis was necessary for walking! Snakes also have pelvis and small leg bones.

Similarities in Development of Embryos Many organisms have very similar development patterns in their embryos. EX: Humans have structures that resemble gill slits in an early stage of development. These structures become the bones of our inner ear.

Similarities in Molecules Many molecules in organisims are the same, or very close to the same. EX DNA- all living organisms use it, same basic structure! Ex: Hemoglobin The more similar the molecule, the more closely related the organisms.

Fossil Record.

Pace of Evolution Gradualism When a species acquires small changes over time that build to form a new species. Originally thought the only way evolution happens.

Pace of Evolution Punctuated Equilibrium When a species has very little change, followed by large amounts of change in “RELATIVELY” short time. This seems to be the more common way evolution happens.

Patterns of Evolution Hawk Moth and Star Orchid from Madagascar. 28 cm proboscis to reach nectar. The Bee Orchid Produces no nectar, but still attracts male bee pollinators. HOW? Co- Evolution: Process in which 2 or more organisms evolve together. Some plants can only be pollinated by a certain insect. Some parasites can only live in certain hosts. Some Organisms have evolved very close relationships. Ex: Acacia tree and Ants.

Patterns of Evolution Convergent Evolution: Process in which organisms evolve similar structures to fit in a similar environment. (Analogous Structures) Ex: Insect and Bird Wings.

Patterns continued Divergent Evolution: A single species evolves into two separate species. Also called Speciation or Adaptive Radiation

Artificial Selection Can be referred to as human directed evolution.