Evolution

Evolution= genetic change of a population over time

How do we know about evolution? In 1831, at the tender age of 22, Charles Darwin set sail on the HMS Beagle. The original purpose of the voyage was to map out trade routes for Great Britain, but Darwin arranged to work as a field naturalist, recording details and illustrations of interesting flora and fauna as he sailed (read: job for slackers). The voyage did not return to England until 1836.

These are Charles Darwin’s drawings! These are Charles Darwin’s notes!

Voyage of the Beagle

Interesting Galapagos Species Galapagos Tortoise Blue-Footed Booby! Marine Iguana Galapagos Penguin

Darwin began to notice that organisms in isolated locations (i. e Darwin began to notice that organisms in isolated locations (i.e., on islands) often bore resemblance to their mainland counterparts, but with slight morphological changes. He began to wonder about the long-held assumption that species were created in their present forms.

In 1859, Darwin published his magnificent work, The Origin of Species. Two main points of the text were: Descent with Modification - Darwin proposed that species were, in fact, not created in their present forms, but rather had common ancestry with other extant species. Darwin proposed natural selection as the mechanism for this descent with modification. A word on Thomas Huxley

But wait… What took him so long?! 1. Natural theology had ruled the sciences for many years. 2. He was unsure about the nature of variation which natural selection acted upon. “We are profoundly ignorant of the causes [of variations]…” - Charles Darwin 3. He was young and insecure about the idea.

His ideas weren’t entirely original either… Alfred Russel Wallace (1823-1913) A professional collector stumbled upon the ideas of Descent with Modification and Natural Selection while observing beetles in Malaysia. He wrote Darwin a famous letter in 1858 and disclosed his ideas.

Darwin’s magnum opus, The Origin of Species, laid out a clear and simple description of natural selection that helped to support their claims.

The two men presented joint letters to the Linnaean Society in 1858.

Darwin’s Four Postulates 1. In every population, there is variety.

2. Some of that variety is passed on to offspring. Aw, he has your eyes!

3. There are always more individuals produced than can survive. Some will die because of disease, predators, or resource availability

4. So, Over time, the individuals who are the most fit for their environment will survive better to reproduce. If that fitness is attributed to their genetics, this will lead to an increased representation of their alleles in future generations (genetic change/time) (not THIS kind of fit!)

Natural Selection Certain traits will be selected by the environment in which the population lives. Individuals with those traits will go on to better reproduce offspring with those traits.

Natural Selection

Did he do it alone?

No!!!!! Not only did Wallace have similar ideas, Darwin was influenced by the work of many scientists before him…

Carolus Linnaeus AKA Hot Pants (1707-1778) Father of Taxonomy Developed binomial nomenclature

Okay, so this thing definitely doesn’t look like my dog… Georges Cuvier (1769-1832) Okay, so this thing definitely doesn’t look like my dog… Father of Paleontology Described hundreds of fossils evidencing extinct life forms

True to natural theology, Cuvier described these fossils as a result of CATASTROPHISM. And, to be clear, many of them were the result of major catastrophes

James Hutton and Charles Lyell Fathers of Geology Gradualism Uniformitarianism

Jean-Baptiste Lamarck “You get what you need” Inheritance of acquired characteristics

Don’t laugh! Lamarck was the first person to place fossils in an evolutionary record! Lamarck acknowledged the old age of the Earth!

So, what’s the evidence? What convinced Darwin and what have we learned since?

Biogeography

Biogeography: Distribution of species around the earth Biological diversity results from descendants of a common ancestor becoming adapted to diverse environments. Seeing where species are located (fossils) and where they’ve moved to, as well as how they’re related (DNA)

Make

Fossils Fossils prove the existence of many different organisms through time that are related to existing organisms. These fossils prove that there were living organisms from which every living thing today was derived.

Fossil Analysis

Homologous Structures Homologous structures provide strong evidence that all four-limbed vertebrates have descended, with modifications, from a common ancestor.

Homologous Structures Structurally similar but have different functions. Homologous Structures

Vestigial Structures

Vestigial Organs The organs of many animals are so reduced in size that they are just vestiges, or traces, of homologous organs in other species. (leftovers)

Comparative Embryology There are many similarities in the early stages of development of vertebrates, which suggests common ancestry.

Comparative Embryology

Molecular Biology

Molecular Biology Protein synthesis is essentially the same in all organisms. Proteins in all organisms are composed of the same 20 amino acids. DNA is very similar between two closely related organisms Compare amino acid sequences of 2 organisms The more amino acids organisms share, the more closely related they are