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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
Artificial Selection: Animal Data
Darwin had practiced
Artificial Selection
in Pigeons by breeding
them for specific traits
Artificial Selection: Plant Data
Darwin had seen the effects of Artificial Selection in plant products
by breeding them for specific traits
Comparative Anatomical Data
The forelimbs of all mammals have the same skeletal elements
Comparative Embryological Data
Identifies anatomical homology that is less apparent in adults
Geological
Data
1830: Lyell publishes
Principles of Geology
Fossil
Data
It is believed that
whales evolved from
terrestrial creatures.
These fossils from
Egypt and Pakistan
show an extinct whale
(Brachiosaurus) that
had hind limbs.
Transitional fossils link the past with the present
“Living Fossil”
Data
Horseshoe Crabs are an
example of a “living fossil”
They have evolved very little
over the last 600 million
years.
South American Data
Darwin sails around the world
and in South America is puzzled
by 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
Galapagos Data
Darwin sailed next to the
Galapagos Islands, a set
of islands 3000 miles away
from any other land source.
He carefully characterized
the island finches based on
their specific traits. He
found that several different
types of birds existed and
each had specific traits that
would allow them access to
a specific food source on the
island.
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
Evolution of
Nervous
Systems
•radial nerve
•nerve net
•segmental nerve
•ganglion
•nervous system
Dinosaur Extinction?
•Crater found
•Dated to dinosaur
extinctions
•66 million years ago
•Iridium
•Would we have
evolved if this didn’t
happen?
Humble Beginnings?
The Human Lineage
Vertebrate
Brain Evolution
•midbrain emphasis decreases
•forebrain emphasis increases
•cerebellar emphasis increases
Human Evolution and Brain Size Increases
Varied Cortical Commitment
Association Areas Increase with Evolution
Varied Cortical Surface Area
Genetics and Evolution
Modern Day Chimpanzee
Modern Day Human
Evolution of Language
Chimpanzee
Human
High in throat
Low in throat
•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