Evidence for evolution Darwin’s theories

Darwin – Evolution by Natural selection Survival of the fittest. The ones that are most “fit” are adapted to survive, have more offspring and pass on the traits to those offspring

Darwin or Lamarck?

“Origin of Species” 2 main points of Darwin 1) Descent with modification 2) Natural selection – A differential success in reproduction caused by an interaction between the environment and the phenotypes of a population

Darwin’s big adventure! He sailed around the world

He sailed on the Beagle No, Not that beagle!!!!!!!

HMS Beagle This one

Darwin observed There was a change in diversity as he sailed. There was more diversity close to equator which became less as he sailed toward poles

Galapagos islands

He studied lots of interesting creatures

Especially finches

Darwin’s Finches Finches on different islands developed type beaks due to natural selection according to type of food available.

Finches Ground finch – Seed eater Small tree finch – Insect eater Woodpecker finch – Tool user

Beak Variation Throughout many generations the beak shape changes depending on the available food sources. The changes are reflected in the genetic differences of the finches. The finches adapt to the food source that is available

Natural selection requires three conditions to be met Variation must exist in the population These variations lead to differences in reproductive success of individuals These variations are transmitted to the next generation

The Peppered Moth Studied for the last two hundred years. Majority had light colors, camouflage while on trees and lichen. Pollution in England caused lichens to die during the Industrial Revolution. Trees became black with soot causing moths to die off due to predators. This helped the darker moths flourish because they were ability to hide on dark trees.

Peppered moth Moths adapt to pollution on tree bark better camouflaged survive Problem: peppered moths do not rest on tree trunks!

Examples of natural selection Evolution of drug resistance in HIV

Antibiotic Resistant bacteria

Artificial selection The breeding of domestic plants and animals Traits are SELECTED by scientists, or breeders

Corn artificially selected

Evidence for evolution Fossil Evidence Anatomical Evidence Vestigial structures Embryological Homology Molecular Homologies

1. Fossil Evidence Fossilization is an event that preserves evidence of past living organisms Fossilization is relatively rare in softer tissue There are fossils found that appear to be possible ancestors of modern organisms Some transition fossils (intermediates) have been found, but never as many as Darwin predicted

archaeopteryx Winged reptile. Possible link between reptiles and birds. Probably a type of velociraptor

Horse evolution Has more fossil evidence than any other but still has several gaps.

2) Anatomical Evidence Homologous structures Analogous structures Vestigial organs

Homologous structures Homologies Structural resemblance that possibly indicate related ancestry of species Ex. Bat wing, cat leg

Analogous structures Analogies- Structures that are similar in function but different in development and don’t indicate relationship Ex. Bird wing and insect wing

Analogies or homologies

Analogies or homologies

Analogies or homologies

3) Vestigial structures Structures that have little or no use in an organism. (historical remnants) Ex. Whales and snakes with vestigial hip bones

4) Embryological Homologies Haeckel (1874) Said all vertebrate classes pass through an identical evolutionarily progression though out development

Proved NOT true Actual photographs

However There are some similarities between all vertebrate embryos at early development. Pharyngeal pouches (similar to gill slits) and tails

5) Molecular Homologies Similar DNA and Proteins The Primary evidence to determine relatedness

Similarities in DNA Sequence 38 38

Comparative hemoglobin structure Why compare DNA & proteins across species? The sequence in DNA & proteins is a molecular record of evolutionary relationships. 10 20 30 40 50 60 70 80 90 100 110 120 Lamprey Frog Bird Dog Macaque Human 32 8 45 67 125 Comparative hemoglobin structure Why compare these genes? Molecular Record What are we comparing here? - comparing DNA (base sequence) & proteins (amino acid sequence) What assumption do we make about genes and relatedness?  the more closely related, the more DNA bases & amino acids you have in common have to compare genes for protein the organisms have in common… can’t compare genes for proteins you don’t have compare common genes cytochrome C (respiration) hemoglobin (gas exchange) Number of amino acid differences between hemoglobin (146 aa) of vertebrate species and that of humans

Patterns of Evolution Co-evolution Convergent evolution Divergent evolution

Co-evolution when 2 organisms evolve together Ex. star orchid and hawk moth Each Have specific structures adapted to each other for pollination

coevolution Host – parasite Hook worm – lives in humans Can provide humans with disease prevention and lower bad immune response

Convergent evolution Organisms that appear similar but are not closely related. Developed similar structures for same environment independently Ex. Shark and porpoise = fish and mammal

Divergent evolution –When related species become more and more different. Ex. German shepherd and poodle = both dogs

Elephant and mammoth Called divergent parallel evolution Thought to have a common ancestor long ago, and then evolved similarly

Biogeography Geographic isolation leads to differences                                Biogeography Geographic isolation leads to differences The flying lizards (genus Draco) of Southeast Asia. Differ in size according to location