Principles of Evolution California Standard 8.e.

Evidence of Evolution, Sect. 13-2 Charles Darwin’s Theory of Evolution (1859) for the first time provided an explanation as to why there was a diversity of animals on Earth and why the fossil past provided a link to the current diversity of animals on Earth. Darwin provided evidence that there are “missing links” between animals and plants of the past and animals and plants we find currently on Earth.

Charles Robert Darwin

Charles Darwin; 1809-1882

Voyage of the HMS Beagle

Galapagos Islands

“The Origin of Species by Means of Natural Selection “The Origin of Species by Means of Natural Selection.” Published in 1859

Darwin’s theory is supported by three major points regarding the Earth: 1. Earth is about 4.5 billion years old. 2. Organisms have inhabited the Earth for most of its history. 3. All organisms living today “evolved” from earlier, simpler life-forms.

Evidence of evolution takes the form of: 1. Fossil evidence 2. Molecular evidence 3. Physical evidence such as, homologous structures and vestigial structures

Burgess Shale Fossils, located in north western Canada

Burgess Shale Discovered in 1909 in Western Canada. This fossil location supported the Theory of Evolution more than any other fossil discovery. Many of the fossils discovered there connected the “missing-link” between species.

Trilobite fossil at the Burgess Shale

Extinct fossil from the Burgess Shale

Biological Molecules Contain a Record of Evolution 1. The amino acid and therefore proteins in closely related species have greater similarity than species which are not closely related. Therefore, species that look similar also have very similar amino acid sequences.

Evolutionary Relationship of Vertebrates

Molecules of Evolution 2. The changes in nucleotides, the building blocks of DNA, are greater in species that are separated a great deal phylogenetically, or how they look, than those that are closely related.

A change in the nucleotide sequence results in a mutation A change in the nucleotide sequence results in a mutation. Some mutations result in speciation.

A change in the nucleotide sequence results in a different gene on a chromosome results… a change in the mRNA which results in… a change in the amino acid sequence which results in… a change in the type of protein formed, which then causes…

mutations… are all mutations bad? Maybe yes. Maybe no.

Was Darwin’s theory correct? How the organism looks or behaves. Or put another way… a mutation causes a change in the adaptation of that organism to a changing environment through natural selection. Was Darwin’s theory correct?

Genetic mutations result in speciation. Speciation results in biological diversity in the Galapagos finches.

Phylogenetically Tree

Where do birds come from? Birds are now thought to have evolved from dinosaurs. The evidence comes out of China. In 1996 a fossil with feathers was discovered in China which started the thought of birds from dinosaurs. The name of the fossil was Archaeopteryx.

Archaeopteryx

Anatomy and Development Suggest Common Ancestry Comparison of anatomical (structures) of different types of organisms often reveal similarities in body structures. Some bones are reduced in size or have no use at all. These anatomical changes which may show evidence of an organism’s past are called vestigial structures.

Vestigial hind limbs of a whale

Vestigial Structures

Vestigial Structures Flightless cormorant with vestigial wings.

Homologous structures: same structures yet different functions Homologous structures: same structures yet different functions. The arm of a penguin, alligator, bat and human.

Homologous Structures. Bat wing and human hand Homologous Structures. Bat wing and human hand. Same structure different function.

The End. Do you see the Frog?