Download Evolution

Evolution
• Evolution – populations change over time
• Current theory – life forms have
descended from previous forms through
changes in structure/function. Example
often cited: horse feet.
• Occurs SLOWLY
Cited Evidence
• Fossils – evolutionists say that organisms have
become more complex over time
• Homologous structures – those that have similar
structures but different functions (bird wing
compared to human arm and whale flipper) –
evolutions say this is evidence of descent from a
common ancestor
• Vestigial organs – those that serve no function.
Examples cited – human tail bone and appendix.
Evolutionists say this is evidence of organs in an
ancestor which lost their function.
Darwin’s Finches
• The beaks are different shapes –
corresponding to different feeding habits
Theories of Evolution
• Lamark – acquired characteristics (giraffe necks)
– WRONG
• Darwin – Natural Selection:
– Organisms have natural variation (from mutations)
– Those organisms better able to compete survive to
reproduce
– AKA survival of the fittest
– Most used example: peppered moth
– ****Does NOT change an individual organism!!!!
Important Terms
• Mutation: change in DNA
• Natural Selection: change in gene
frequencies as a result of differences in
survival and reproduction among
organisms
• Gene Flow: Change in the genetic traits
as organisms enter or leave a population
• Genetic Drift: Random changes in gene
frequencies over time
Adaptations
• Adaptation: an inherited characteristic that
makes a species more suited to its
environment (examples – tortoises;
rabbits)
• NOT changes in an individual organism
• Instead, changes in the # of individuals
that have the particular trait
Remember
• Survival of the fittest means that
POPULATIONS evolve – NOT
INDIVIDUAL ORGANISMS
Geographic Isolation
• Geographic isolation occurs when a
population becomes separated by
changes in the environment
• Example – changes in a river’s course,
ponds in Death Valley
Convergent Evolution
• Adaptations of different species that make
them more alike.
• Common in animals in similar
environments
• Example: shape/fins of sharks, penguins
and porpoises.
Divergent Evolution
• When organisms of the same species
develop adaptations that make them more
different.
• Common when separated into different
environments.
• If many adaptations occur, new species
are developed.
• Example: many species of birds from a
common ancestor
Extinction
• Occurs when there is a sudden change in
the environment with no time for
adaptations
• Asteroids, habitat destruction, overhunting
Biodiversity
• All the different life forms on the planet:
The sum of all the genetic material of all
organisms
• All ecosystems, all species, with all their
DNA
• Biodiversity is reduced when man alters
environments (over killing, pollution,
kudzu)
The Fossil Record
• Fossil – any evidence of an organism left
behind
• Examples: bones, molds (i.e. footprints)
• Fossilization begins when an organism is
suddenly buried (volcano, for example).
As sediments pile up over time,
organism’s remains are transformed into a
fossil
Fossil Terms
• Paleontology – the study of fossils
• Stratification – layers of sedimentary
rock. Different fossils are found in different
layers
• Fossils are dated by relative dating. The
fossils themselves are not dated, but are
considered older/younger based on which
layer of rock they are found in.
Absolute Dating
• Radioactive Dating:
– C-14 is present in all living things
– Half life is 5700 years.
Geologic Record
• Evolutionists say that the earth is more than 4
billion years old, and that humans have existed
for only a few hundred thousand years.
• So how do they come up with what was going on
billions of years ago?
• Their key concept: uniformity – all geological
processes going on now (faulting, erosion, etc)
were also going on in the past.