EVOLUTION!!!

Charles Darwin, 1808-1882

WHAT ABOUT HIM???

born into a wealthy familymedical school drop-out - thought surgery was “brutal”his father pushed him into becoming a clergyman and dropped-out of this as welleventually followed his interests in ecology, geology and taxidermy author of “On the Origin of Species” - 1859, provided evidence for evolution by natural selection

SOME OF DARWIN’S INFLUENCES…

Charles Lyell, 1797-1875 - “Principles of Geology”, described landforms as the result of gradual processes over time (Darwin saw evidence of this on his voyage - bands of coral fragments in volcanic rock)

John Henslow, 1796-1861 - botanist/geologist, Darwin’s mentor

SOME OF DARWIN’S INFLUENCES…

Thomas Malthus, 1766-1834 - “An Essay on the Principle of Population”, proposed that if the human population continues to grow “unchecked” it would soon reach carrying capacity…then what???

"In October 1838, that is, fifteen months after I had begun my systematic inquiry,I happened to read for amusement Malthus on Population, and being well preparedto appreciate the struggle for existence which everywhere goes on from long- continued observation of the habits of animals and plants, it at once struck me thatunder these circumstances favourable variations would tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of anew species. Here, then I had at last got a theory by which to work".

Charles Darwin, from his autobiography. (1876)

DARWIN’S VOYAGEwas selected as an unpaid geologist/naturalistvoyaged on the HMS Beagle

purpose of voyage was to chart the coastline of South America over 2 yearsDarwin collected fossils and living organisms and took many notesunfortunately…he was seasick for most of the trip

WHAT DID HE SEE IN THE GALAPAGOS ISLANDS???

Galapagos Islands - volcanic islands west of Ecuador in the Pacific Ocean (16 islands - 5 inhabited), some are still formingobserved birds (later determined to be finches) - similar in appearance with differing beakssince these were islands, all of the birds were assumed to have one common ancestor each bird was adapted to eating a particular food - seeds, insects, etc.

DARWIN’S FINCHES

EVOLUTION BY NATURAL SELECTION???Darwin's theory (yes, you need to know this!):

within a given species, more individuals are produced than can survive due to limited resources (food, shelter, mates)as a result, there is a struggle for existence/competition for limited resources individuals within a species show variation - no two individuals are exactly alike those with advantageous traits have a greater chance of survival, and therefore of reproducingindividuals produce offspring that tend to resemble their parents (inheritance)advantageous traits that promote survival are inherited by offspring, so individuals possessing those traits will become more common in the population over successive generations because they are more likely than individuals not possessing those traits to survive and reproduce

HOW DO ORGANISMS ACQUIRE ADVANTAGEOUS

TRAITS???

GOOD QUESTION!!!

WHAT IS EVOLUTION BY NATURAL SELECTION???

Simply stated:

in nature individuals compete for limited resources and based on those resources, nature selects the

best suited for the environment = natural selection

let’s look at an example…and another…and another…and another…

INDUSTRIAL MELANISM

More on Darwin…Natural selection…less wordy

more organisms are produced than can survivethere is competition for resourcesthose with favorable traits (depending on what the competition is over) win the resource(s)these are the organisms that survive and reproduce (and make more like themselves)favorable traits are the result of differences between organismsdifferences are the result of random mutations

TERMS TO KNOW

adaptation - change in a species that makes it better suited for its environment

natural selection - “nature” selects organisms with better suited traits to survive and reproduce, over time organisms become better adapted

isolation leads to the development of new species - when organisms are isolated and cannot breed, they become more different over time

EVIDENCE FOR EVOLUTION1. fossils - show a pattern of development, all organisms evolved from earlier life forms

FYI…there are few “missing links” or intermediate forms or transitional species

archaeopteryx is one of the few “missing links” - it has both reptile and bird-like features

2. biological molecules - comparing proteins and nucleic acid sequences can reveal a common ancestor

for example - comparing differences in hemoglobin (a protein that carries oxygen in your bloodstream) - more distant ancestors have more differences

3. comparing anatomy can reveal similaritieshomologous structures -similar structures, although

they may have different functions/are adapted to different environments

analogous structures – similar function, but occur in unrelated species adapting to similar environments

4. biogeography – studies locations of organisms around the world closely related organisms can be

adapted to different environments that are nearby (ex. – Darwin’s finches)

unrelated organisms can have similar adaptations to similar environments that are far apart (ex. – Australia’s mammals that resemble mammals in similar environments but are unlike in that they are all marsupials)

5. vestigial structures - structures that have less important/no function as compared to related organismsfor example - the human tailbone (coccyx), ear muscles and the gene to make vitamin C

other vestigial structures - baleen whale pelvis and femur, splint in horses, pelvis and femur in some snakes

6. comparing embryos - early in development many organisms share similar characteristics

phylogeny – puts evidence together to show relationships among organisms

GRADUALISM VERSUS PUNCTUATED EQUILIBRIUM

gradualism - evolution occurs slowly over a long period of time, organism changes many times

for example – human evolution…many small changes occurred…larger brain size, bipedalism

punctuated equilibrium - major environmental changes may cause evolution to occur in spurts, rapid change followed by periods of no changefor example – species that show few “transitional species” such as T. rex