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Evidence for Evolution
Transcript of Evidence for Evolution
Scientists have collected thousands of well dated fossils from around the globe. These fossils clearly show a progression of organisms through time.
Animals without backbones predate vertebrates. Amphibians appear after bony fish, mammals appear after reptiles, and the oldest known fossils contain bacteria.
Evidence of Evolution
The evolution of the horse occurred over a period of 50 million years transforming a small, dog sized mammal, Eohippus into the modern horse.
Several fossils of different horse ancestors show small changes over time that resulted in the modern Equus.
La Brea tar pits are still revealing
clues to California's past.
New fossils are still being discovered today.
Coelacanth: The living fossil fish
Scientists understood anatomy long before Darwin's idea of Evolution
Small leftover organs or structures that had a function in an ealier ancestor but have no apparent function in modern species. (Pelvic bones in whales and snakes, Appendix, Tailbone, Wisdom teeth)
Background: In the 1700s people believed that at conception, organisms were simply a smaller version of themselves that grew larger. It was not until later that anatomists and physicians believed that organisms developed from a formless egg and became increasingly complex, an idea they called Epigenisis.
Cladograms look at common characteristics and structures in organisms.
Comparative anatomy and Cladograms
Gradualism and Catastrophism
Biogeography is the study of the distribution of organisms around the world.
Which one does not belong?
Genetic Evidence: Genome sequencing
Paleontology, Anatomy, Geology, and Molecular Biology all support the theory of gradual change over millions of years by which descendants come to differ from their ancestors.
All living things share the same genetic code, DNA, and make most of the same proteins from the same 20 amino acids.
All eukaryotic organisms use ATP as a chemical energy storage molecule and have similar cell structure.
Some genes are found in many organisms from fruit flies to humans and therefore give evidence of a very distant common ancestor.
Example: Homeobox gene that controls devlopment.
Species: a group of organisms that can reproduce
Fossils: are traces of organisms that existed in the past. The locations of fossils in different rock layers give scientists insight to the earth's past.
Variation: The differences in the physical traits among individuals in a group of organisms. (Changes in DNA)
Adaptation: A feature that allows an organism
to better survive in its environment.
Are mules considered a species?
Horses and Donkeys are separate species but can produce offspring which are mules. Mules cannot have children of their own.
Evidence of common ancestry among species comes from many sources
An ancient order of fish with one recently (1999) discovered extant species in Indonesia.
The first fossil evidence of the Coelacanth dates back to the Devonian peiod about 380 million years ago. A jawbone fossil found in Australia was dated to be approximately 360 million years old. They were believed to have become extinct until living specimens were discovered.
Homologous Structures: Features that are similar in structure but appear in different organisms and may have different functions. (Front limbs)
Analogous structures: Structures that
perform a similar function but are not
similar in origin or shape. (Wings, Fins)
The similarities in developing embryos of
several species of animals suggest common
ancestry and common mechanisms for cell
division and specialization.
Organisms change to adapt to their specific environments
Darwin hypothesized that the finches from the
Galapagos had migrated there from the mainland. Different islands had different food
sources, climates and predators. The different
environmental factors favored different traits.
Since 2003, researchers have continued to sequence the genomes of hundreds of organisms. A study in 2005 revealed that human DNA is 96% similar to chimpanzee DNA. By comparing genomes, genetics can give a clearer picture of relatedness and common ancestry.
Catastrophism is the theory that nautral disasters such as floods and volcanic eruptions happened often during Earth's history and these events shaped landforms and caused species to become extinct.
Gradualism is the theory that landforms resulted from slow changes over a long period of time. For example the creation of canyons by rivers cutting through rock are an example of gradualism.
Uniformitarianism is the theory that states that the geologic processes that shape the Earth are uniform through time, meaning that small changes in Earth's features are still happening today.