Transcript Darwin and Evolution 2

Darwin and Evolution
Evidence
Adaptation
Speciation
Darwin’s Voyage
H.M.S. Beagle (1831) – as the ship’s naturalist
collected plant and animal specimens
collected fossils
some resembled organisms still alive
some were completely unknown
Darwin’s Voyage
Galapagos Islands (west of South America)
found giant land tortoises, marine iguanas and
finches with differently shaped beaks
Darwin’s Voyage
Returned to England in 1836
discovered that the organisms found on the
Galapagos were found nowhere else
BUT, each species looked like similar species
found on the mainland
1859 he published On the Origin of Species
Proposed the idea of natural selection
struggle for existence
survival of the fittest – live to reproduce
Ideas That Influenced Darwin
James Hutton – proposed that Earth is
shaped by geological forces that took place
over extremely long periods of time
Charles Lyell – explained that processes
occurring now have shaped Earth’s
geological features over long periods of
time
Ideas That Influenced Darwin
Jean-Baptiste Lamark – proposed that by
selective use or disuse of organs, organisms
acquired or lost certain traits during their
lifetime
These traits could be passed on to their offspring
Alfred Wallace – wrote to Darwin,
speculated about evolution by natural
selection based on his studies of plants and
animals
Darwin’s Theory
Variations exist in a population and are
inherited
In nature, there is a tendency toward
overproduction
Species compete for limited resources
Each individual has advantages and
disadvantages
Darwin’s Theory
Individuals best suited to the environment
survive and reproduce; those not as well
suited die or have fewer offspring
Species change over time – new species
appear and others disappear
Descent with modification
Common descent
Evidence for Evolution
Anatomy
Embryology
Biochemistry
Genetics
Anatomy
comparative anatomy – study of structures
of different organisms
vestigial organs – structures that have no
function in the living organism (appendix)
homologous parts – similar body parts
Embryology and Biochemistry
comparative embryology – study of
developing organisms
embryos start out very similar, but as they
develop, they become distinct
comparative biochemistry – studies of
organisms on a biochemical level (proteins,
DNA)
Genetics
production of new alleles and genetic
recombination
mutations
selective breeding
DNA of humans and chimps is 99%
identical
Adaptation
Structural
Physiological
Behavioral
What is an adaptation?
Any trait that aids the chances of survival
and reproduction of organisms
Variations vs. Adaptations
Adaptations are products of evolution by
natural selection (always good)
Variations are the raw materials upon which
natural selection acts (can be good or bad)
Complex adaptations
e.g. the eye
Does not arise
overnight
Occurs over many,
many generations
Does not invent, but
modifies what already
exists
Types of adaptations
Structural adaptations – adaptations
involving structure or anatomy
(woodpecker’s beak, anteater’s snout)
Physiological adaptations – adaptations
with a chemical basis that is associated with
an organism’s function (spider’s web, snake
venom)
Behavioral adaptations – results from the
response of an organism to its environment
(bird’s migrating, plants growing to light)
Human Evolution
Homo habilis
Homo erectus
Homo sapien
Primate adaptations
Humans are primates (so are monkeys and
apes)
Problem-solving ability
Flexible shoulders and forelimbs that can be
rotated
Opposable thumb
African origins
Australopithecines –
“southern ape”
Lucy – 3.5 million years
old
3-4’ tall and about 66
pounds
If she were alive today,
she would not be
considered human
Origin of Humans
Hominids – modern humans
Handy man (Homo habilis) – 1.8 million
yrs ago – made tools
Upright man (Homo erectus) – 1 million yrs
ago – learned to make and use fire
Modern man (Homo sapien)
Neanderthals – short, powerfully built
Cro-magnons – fully modern height, skull
structure, skeleton, teeth and brain size