What did Darwin say? What evidence supports Evolution by Natural Selection? What impact did Evolution have on biology?
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
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
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.
The avian nature of the brain and inner ear of Archaeopteryx (Alonso et al. 2004) - Archaeopteryx, the earliest known flying bird from the Late Jurassic period, exhibits many shared primitive characters with more basal coelurosaurian dinosaurs (the clade including all theropods more bird-like than Allosaurus), such as teeth, a long bony tail and pinnate feathers. However, Archaeopteryx possessed asymmetrical flight feathers on its wings and tail, together with a wing feather arrangement shared with modern birds. This suggests some degree of powered flight capability but, until now, little was understood about the extent to which its brain and special senses were adapted for flight. Alonso et al. (2004) investigated this problem by computed tomography scanning and three-dimensional reconstruction of the braincase of the London specimen of Archaeopteryx. A reconstruction of the braincase and endocasts of the brain and inner ear suggest that Archaeopteryx closely resembled modern birds in the dominance of the sense of vision and in the possession of expanded auditory and spatial sensory perception in the ear. Alonso et al. (2004) concluded that Archaeopteryx had acquired the derived neurological and structural adaptations necessary for flight. An enlarged forebrain suggests that it had also developed enhanced somatosensory integration with these special senses demanded by a lifestyle involving flying ability.
The evolution of resistance to insecticides in hundreds of insect species is a classic example of natural selection in action. The results of application of new insecticide are typically encouraging, killing 99% of the insects. However, the effectiveness of the insecticide becomes less effective in subsequent applications. The few survivors from the early applications of the insecticide are those insects with genes that enable them to resist the chemical attack. Only these resistant individuals reproduce, passing on their resistance to their offspring. In each generation the % of insecticide-resistant individuals increases.
Ch 15 evolution 1 8-2013
er Warbl finch Gr es ch ou Cactus fin nd eater ee fi n Insect eatersTr ch Seed eaters s e Bud eater 2006-2007
A. Proposed a way how evolution works 1. How did creatures change over time? 2. By natural selectionB. Collected a lot of evidence to support his ideas 1. 1809-1882 2. British naturalist
A. Darwin invited to travel around the world • 1831-1836 (22 years old!) • made many observations of nature • mission of the Beagle was to chart South American coastline Robert Fitzroy
B. Explored Galapagos Islands • 500 miles off coast of Ecuador
Recently formed volcanicislands. Most of animals onthe Galápagos live nowhereelse in world, but they looklike species living on SouthAmerican mainland. 800 km west of Ecuador
Many of Darwin’s observations made him wonder… Why? Why were these creatures found only on the Galapagos Islands?
Evidence showed thatcreatures had changedover time present day Armadillos Darwin asked: Why should extinct armadillos & modern ancient Armadillo armadillos be found on same continent?
Evidence showed that creatures had changed over time(extinct) Giant ground sloth present day Sloth Darwin asked: Why should extinct sloths & modern sloths be found on the same continent?
Darwin found...different shells ontortoises on different islands Darwin asked: Is there a relationship between the environment & what an animal looks like?
Darwin was amazed tofind out:All 14 species of birdswere finches…But thereis only one species offinch on the mainland! QuickTime™ and a Photo - JPEG decompressor Finch? are needed to see this picture. Sparrow? Darwin asked: If the Galapagos finches came from the mainland, why are they so different now? Woodpecker? Warbler?
Darwin found: different beaks areThe differences inherited variationsbetween species of serve as adaptationsfinches were that help birds compete for foodassociated with the these birds survive &different food they reproduceate. pass on the genes for those more fit beaks over time nature selected for different species with different beaks
Warbler finch Cactus finch Woodpecker finch Sharp-beaked finch Small er Small insectivorous Warbl ground tree finch finch finch Gr es Cactus ou ch Large Medium nd in eater finsectivorous ground fin ee tree finch Insect eaters finch Tr ch esVegetarian Seed eaters Largetree finch ground Bud eater finch natural selection for best variation survival & reproduction
A. Darwin’s conclusions 1. Variations in beaks in original flock adaptations to foods available on islands 2. Natural selection for most fit over many generations finches were selected for specific beaks & behaviors 3. Offspring inherit successful traits over many generations finches were selected for specific 4. Separate into different species
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
Giraffes that already have long necks survive better Leave more offspring that inherit long necks variation selection & survival reproduction & inheritance of more fit traits
A. Fossil record Shows change over timeB. Anatomical record Comparing body structures 1. homology & vestigial structures 2. embryology & developmentC. Molecular record Comparing protein & DNA sequencesD. Artificial selection Human caused evolution
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
the Earth is old Life is oldLife on Earth has changed
In 2006 fossil discovery of early tetrapod 4 limbs Missing link from sea to land animals?
Land Mammal ? the are ere a diate W h me inter sils? fos ? Complete series of transitional ? fossilsWe found the fossil — no joke! Ocean Mammal
Today’s organismsdescended fromancestral speciesFossil of Archaeopteryx lived about 150 mya links reptiles & birds
Animals with differentstructures on the surfaceBut when you look underthe skin…It tells an evolutionary storyof common ancestors
The same bones under the skin limbs that perform different functions are built from the same bones How could thesevery different animals have the same bones?
Structures that come from the same origin Homo = same logous = information Forelimbs of human, cats, whales, & bats are homologous same structure on the inside same development in embryo different functions on the outside evidence of common ancestor
Don’t be fooled by these! look similar on the outside same function different structure &How is a bird developmentlike a bug? on the inside different origin no evolutionary relationship Solving a similar problem with a similar solution
Dolphins: aquatic mammal Fish: aquatic vertebrate both adapted to life in the sea not closely related
Flight evolved 3 separate times — evolving similar 3 groups with wings solutions to similar • Does this mean they have a “problems” recent common ancestor? They just came up with the NO!same answer!
Why do these pairs look so similar? Monarch male Viceroy male poisonous edible Which is the moth vs. the bee? fly vs. the bee? fly bee moth bee
Hind leg bones on whale fossilsWhy would whaleshave pelvis & legbones if they werealways sea creatures? Because they used to walk on land!
Structures on modern animals that have no function • remains of structures that were functional in ancestors • evidence of change over time some snakes & whales have pelvis bones & leg bones of walking ancestors eyes on blind cave fish human tail bone
Development of embryo tells an evolutionary story • similar structures during development all vertebrate embryos have a “gill pouch” at one stage of development
Comparing DNA & protein structure • everyone uses the same genetic code! Human Macaque Dog Bird Frog Lamprey DNA compare common genes compare common proteins 8 32 45 67 125number of amino acids differentfrom human hemoglobin 0 10 20 30 40 50 60 70 80 90 100 110120
Closely related species are branches on the tree —coming from a common ancestor
How do we know natural selection can change a population? • we can recreate a similar process • “evolution by human selection” “descendants” of wild mustard
Humans create the change over time“descendants” of the wolf