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Microevolution and Charles Darwin. son of a famous English Physician - a Noblemen was a Naturalist by hobby - collected specimens of nature did not like Medical School got his college degree in Theology in his 20’s took a job as a naturalist aboard the Beagle - PowerPoint PPT Presentation
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Microevolution and Charles Darwin
•son of a famous English Physician - a Noblemen
•was a Naturalist by hobby - collected specimens of nature
•did not like Medical School
•got his college degree in Theology
•in his 20’s took a job as a naturalist aboard the Beagle
•his biology teacher got him the job
•sailed around the world for five years collecting specimens
•based on his findings he introduced Natural Selection as the means of species evolution
Darwin had practiced Artificial Selectionin Pigeons by breeding them for specific traits
Artificial Selection: Animal Data
Darwin had seen the effects of Artificial Selection in plant products by breeding them for specific traits
Artificial Selection: Plant Data
The forelimbs of all mammals have the same skeletal elements
Comparative Anatomical Data
Comparative Embryological Data
Identifies anatomical homology that is less apparent in adults
Geological Data
1830: Lyell publishes Principles of Geology
Fossil Data
Transitional fossils link the past with the present
It is believed that whales evolved from terrestrial creatures. These fossils from Egypt and Pakistan show an extinct whale (Brachiosaurus) that had hind limbs.
“Living Fossil” Data
Horseshoe Crabs are an example of a “living fossil”They have evolved very little over the last 600 million years.
Darwin sails around the worldand in South America is puzzledby the absence of rabbits.
Instead he finds these rabbit-like Patagonian Hares or Mara (Dolichotis patagonum) that are not rabbits but have similar characteristics as rabbits.
He postulates that they must have evolved just like rabbits because of their similar environments
South American Data
Darwin sailed next to the Galapagos Islands, a set of islands 3000 miles awayfrom any other land source.He carefully characterized the island finches based ontheir specific traits. He found that several differenttypes of birds existed and each had specific traits thatwould allow them access to a specific food source on theisland.
Galapagos Data
Darwin’s Logic on Natural Selection
•Any population has the capacity to produce more individuals than it can support.
•If the natural resources are limited this will create a competition for those resources.
•Variations in physical traits could give some individuals an advantage in the competition.
•This advantage would increase the individual’s survival and reproduction chances.
•These physical traits would then be passed on to the individual’s offspring via natural selection.
•In this way populations evolve, not individuals.
Evolutionary Timeline Summary
•10-20 bya: Galaxy forms
•5 bya: Earth forms
•4 bya: Life forms from non-life
•3 bya: Cyanobacteria evolve photosynthesis
•500 mya: Explosion of Life - Massive Extinction
•150 mya: Dinosaurs evolve
•66 mya: Dinosaurs become extinct
•5 mya: Humans begin to evolve
•50 tya: Neanderthals/Cro-Magnon
•10 tya: Homo sapians sapians
•radial nerve•nerve net•segmental nerve•ganglion•nervous system
Evolution of Nervous Systems
•Crater found
•Dated to dinosaur extinctions
•66 million years ago
•Iridium
•Would we have evolved if this didn’t happen?
Dinosaur Extinction?
Humble Beginnings?
The Human Lineage
•midbrain emphasis decreases
•forebrain emphasis increases
•cerebellar emphasis increases
Vertebrate Brain Evolution
Human Evolution and Brain Size Increases
Association Areas Increase with Evolution
Varied Cortical Commitment
Varied Cortical Surface Area
Genetics and Evolution
Modern Day Chimpanzee Modern Day Human
HumanChimpanzee
•A random mutation causes the larynx to drop in human ancestor•This increases the complexity of sounds that the species could make•Couple this with a more complex brain and we have the advent of language•And the evolution of the species based on cognition and language
High in throat
Low in throat
Evolution of Language