Evolution… by Natural Selection 2006-2007

Why do we accept this as a Scientific Theory? What is Evolution? Evolution changes in living organisms over time explains how modern organisms have descended from ancient organisms Why do we accept this as a Scientific Theory?

What we know, so far…. Many different species alive today All life shares common characteristics The Earth is very old Life is very old Life has changed over time The changes have been little changes over long periods of time But how does this work?

Evolution explains Unity & Diversity Only evolution explains both unity of life similarities between all living things diversity of life wide variety of different creatures on Earth DNA

Charles Darwin Proposed a way how evolution works How did creatures change over time? by natural selection Collected a lot of evidence to support his ideas 1809-1882 British naturalist What did Darwin say? What evidence supports Evolution by Natural Selection? What impact did Evolution have on biology?

Voyage of the HMS Beagle Invited to travel around the world makes many observations of nature main mission of the Beagle was to chart South American coastline After graduation Darwin was recommended to be the conversation companion to Captain Robert FitzRoy, preparing the survey ship Beagle for a voyage around the world. FitzRoy chose Darwin because of his education, his similar social class, and similar age as the captain. Darwin noted that the plants and animals of South America were very distinct from those of Europe Robert Fitzroy

Voyage of the HMS Beagle Stopped in Galapagos Islands 500 miles off coast of Ecuador The origin of the fauna of the Galapagos, 900 km west of the South American coast, especially puzzled Darwin. On further study after his voyage, Darwin noted that while most of the animal species on the Galapagos lived nowhere else, they resembled species living on the South American mainland. It seemed that the islands had been colonized by plants and animals from the mainland that had then diversified on the different islands

Darwin found…many unique species Many of Darwin’s observations made him wonder… Why? Darwin asked: Why were these creatures found only on the Galapagos Islands?

Darwin found…clues in the fossils present day Armadillos Darwin found…clues in the fossils Darwin found: Evidence that creatures have changed over time ancient Armadillo Darwin asked: Why should extinct armadillos & modern armadillos be found on same continent?

Darwin found: Different shells on tortoises on different islands Darwin asked: Is there a relationship between the environment & what an animal looks like?

Darwin’s finches Darwin’s conclusions Variations in beaks differences in beaks in the original flock adaptations to foods available on islands Natural selection for most fit over many generations, the finches were selected for specific beaks & behaviors Offspring inherit successful traits accumulation of winning traits: both beaks & behaviors Speciation- process by which new species arise Separate into different species

The finches cinched it for Darwin

From 1 species to 14 species… Warbler finch Woodpecker finch Small insectivorous tree finch Large insectivorous Vegetarian Cactus finch Sharp-beaked finch Small ground finch Medium ground finch Large ground Insect eaters Bud eater Seed eaters Cactus eater Warbler Tree finches Ground finches natural selection for best survival & reproduction variation

Earlier ideas on Evolution LaMarck evolution by acquired traits creatures developed traits during their lifetime give those traits to their offspring example in reaching higher leaves giraffes stretch their necks & give the acquired longer neck to offspring not accepted as valid

Darwin’s view of Evolution giraffes that already have long necks survive better leave more offspring who inherit their long necks variation selection & survival reproduction & inheritance of best fit traits 

5 Principles of Natural Selection heritable variation variation exists in populations (we are all different!) over-production of offspring more offspring than the environment can support competition for food, mates, nesting sites, escape predators differential survival successful traits = adaptations differential reproduction adaptations become more common in population

Survival & Reproduction of the fittest not the biggest… …the fittest! not the fastest… not the bravest… not the strongest… Adaptations the traits that help an organism fit the environment better to survive & reproduce

evolution Darwin concluded: Each species has descended, with changes, from other species over time. Darwin called this… Descent With Modifications or evolution (change in species over time)

Evidence supporting evolution Fossil record shows change over time Anatomical record comparing body structures homology & vestigial structures embryology & development Molecular record comparing protein & DNA sequences Artificial selection human caused evolution

1. Fossil record Layers of rock contain fossils new layers cover older ones creates a record over time fossils show a series of organisms have lived on Earth over a long period of time

Law of Superposition The deeper you dig, the farther back in time you go. The bottom layer is the oldest.

Life on Earth has changed Fossils tell a story… the Earth is old Life is old Life on Earth has changed

We found the fossil — no joke! Land Mammal ? Complete series of transitional fossils ? Where are the intermediate fossils? ? ? There are innumerable intermediate & transitional forms Whales as land creatures returning to the water…. Where are the intermediate forms of whale ancestors? Cartoon making fun of this idea. The cartoons disappeared 10-12 years ago when this fossil was found. Ambilocetic natans = “Walking whale who likes to swim” 4-5 intermediate forms all found in last 2 decades Indus River valley in between India & Pakistan. Someone’s idea of a joke! Ocean Mammal But the joke’s on them!!

Evolution from sea to land 2006 fossil discovery of early tetrapod 4 limbs Missing link from sea to land animals

3. Anatomical record Animals with different structures on the surface But when you look under the skin… It tells an evolutionary story of common ancestors