Darwin, Evolution and Natural Selection Insect eaters Bud eater Seed eaters Cactus eater Warbler finch Tree finches Ground finches 2006-2007

Who was Charles Darwin? British naturalist 1809-1882 Proposed a way how evolution works Called the method natural selection Collected a lot of evidence to support his ideas What did Darwin say? What evidence supports Evolution by Natural Selection? What impact did Evolution have on biology?

How did Darwin figure out his idea? Was hired to work on the HMS Beagle as a naturalist 1831-1836 (22 years old!) 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 Captain 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: Different shells on tortoises on different islands Darwin asked: Is there a relationship between the environment & what an animal looks like?

Darwin found… birds Darwin found: Many different birds on the Galapagos Islands. He thought he found very different kinds… Finch? Sparrow? Woodpecker? Warbler?

But Darwin found… a lot of finches Darwin was amazed to find out: All 14 species of birds were different species of finches… Large ground finch Small ground finch But there is only one species of finch on the mainland! Finch? Sparrow? Darwin asked: If the Galapagos finches came from the mainland, why are they so different now? Warbler finch Tree finch Woodpecker? Warbler?

The finches cinched it! different beaks are inherited variations serve as adaptations that help birds compete for food these birds survive & reproduce pass on the genes for those more fit beaks over time nature selected for different species with different beaks Darwin found: The differences between species of finches were associated with the different food they ate. Darwin said: Ahaaaa! A flock of South American finches were stranded on the Galapagos… Large ground finch Big seed eater Small ground finch Small seed eater Insect eater Warbler finch Leaf & bud eater Tree finch

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

What is Natural Selection? Process in which a trait becomes more or less common in a population. Natural selection acted on peppered moth color… light moths survived when there was less pollution and dark moths survived when coal blackened the trees.

What evidence supports evolution What evidence supports evolution? (don’t write these down yet, we will look in more detail as we continue) Fossil record shows change over time Anatomical record comparing body structures Molecular record comparing protein & DNA sequences Artificial selection human caused evolution

1. Fossil record (fossil = “dug up”) Layers of rock contain fossils Bones, shells, tracks, impressions, etc. New layers cover older ones Show a series of organisms have lived on Earth

Dating Fossils Absolute dating Relative dating Use radioactive isotopes to determine age Relative dating Use other objects around a fossil to approximate age

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

Analogous structures Dolphins: aquatic mammal Sharks: aquatic cartilaginous fish both adapted to life in the sea not closely related

Vestigial structures Evolutionary “leftovers” Hind leg bones on whale fossils Vestigial pelvis bones on modern whales

Bottlenose dolphin mutation Dolphin caught in 2006 had two hind limbs Possible re-emergence (through mutation) of a vestigial trait

Vestigial traits in humans Humans have vestigial traits too! The appendix vestigial form of the cecum Still have a cecum, but it is smaller herbivores use the cecum to digest plant fiber (cellulose)

Human vestigial traits cont. All humans have a tailbone (coccyx) rarely someone is born with a vestigial tail

Human vestigial traits cont. The goose-bump response Remains from a time when we had thicker fur Could stand hair on end to frighten predators or insulate from the cold

Comparative embryology Development of embryo tells an evolutionary story similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development

3. Molecular record Comparing nucleic acid & protein structure everyone uses the same code! DNA & RNA (nucleotides) Proteins (amino acids) compare common genes compare common proteins number of amino acids different from human hemoglobin

Building “family” trees Closely related species are branches on the tree (called a cladogram) — coming from a common ancestor Common ancestor is now extinct

“descendants” of the wolf 4. Artificial selection How do we know selection can change a population? we do it all the time! “evolution by human selection” “descendants” of the wolf

More examples of artificial selection Agricultural crops Farm animals