Evolution 2006 2007 by Natural Selection What is

Evolution… 2006 -2007 by Natural Selection

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 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

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 Robert Fitzroy

Voyage of the HMS Beagle • Stopped in Galapagos Islands • 500 miles off coast of Ecuador

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 Darwin found: Evidence that creatures have changed over time present day Armadillos Darwin asked: ancient Armadillo 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 Cactus finch Woodpecker finch es ch in ee f Tr fin variation nd Insect eaters Bud eater ou Cactus eater Seed eaters Vegetarian tree finch Small ground finch er Warbl finch Gr Small insectivorous tree finch Large insectivorous tree finch Sharp-beaked finch Medium ground finch Large ground finch natural selection for best survival & reproduction

Earlier ideas on Evolution • La. Marck • 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 • Darwin • 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 uheritable variation exists in populations (we are all different!) uover-production of offspring § more offspring than the environment can support ucompetition § for food, mates, nesting sites, escape predators udifferential survival § successful traits = adaptations udifferential reproduction § adaptations become more common in population

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

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

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

We found the fossil — no joke! Land Mammal ? e h t e ar ? e e r Whe mediat r inte sils? fos Complete series of transitional fossils Someone’s idea of a joke! But the joke’s on them!! Ocean Mammal ? ?

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