Transcript Theories of Evolution - Mr. Schultz Biology Page

 The process of change within a living system over a
period of time
 Genotype changes vs. Phenotype changes
 Micro vs. Macro Evolution
 Many different scientists have proposed theories about
this process….…
Microevolution:
Small-scale evolutionary changes,
usually on the molecular level, that
occur over the span of a few
generations and can therefore be
detected in living populations.
Macroevolution:
Large scale evolutionary changes,
speciation events, that may require
many hundreds of generations and are
usually only detectable in the fossil
record
Natural Selection:
The differential reproductive success
of certain phenotypes within a given
environment
“Survival of the Fittest”
“Acquired Traits”
 Theory of use and disuse
 If an organ is used , it becomes stronger and better
developed
 If an organ is not used, it becomes weaker and withers
away
 An organism acquires traits from its experience
(not genes) and those traits are passed down, or
inherited by their offspring
 Example: Lamarck believed that giraffes stretched
their necks to reach food. Their offspring and later
generations inherited the resulting long necks.
 If you have a nose job, your kids will inherit the new
nose!
 In real life, what nose will your kids get? (the old one
or the new one?)
 Answer: the old one!
 What determines that traits are passed to their
children?
 DNA
 If you change your appearance, will your children
inherit the new appearance
 No, because your DNA did not change
 Environmental
Selection
 Role of the
Environment
 Acquired traits????
(Lamarck)
 Charles Darwin
 Theory-descent w/ modification
 Theory-natural selection-main principles:
 A naturalist (studied and preserved biological
specimens that he collected)
 5 year voyage around the world aboard the HMS Beagle
 Theory of evolution by natural selection
 Nature will select the organisms that have variations
that allow them to better survive (survival of the fittest)
 Descent by Modification
 Darwin collected different species that were very similar
and hypothesized that they shared a common ancestor
insects
finches
 Described his theory of evolution
 Caused a lot of controversy and angered the church
 The church initially believed that evolution is a sin
against God
 Before Darwin died, the church accepted his theory
and he was buried in a famous church in England
 Darwin’s theories are accepted today as the most
accurate explanation for evolution
 Overproduction – too many giraffes
 Struggle or compete for food
 Variation in length of neck exists naturally
 Longer neck…reach food...survive
 Longer necked giraffes survive and reproduce to
eventually originate a new species of giraffes
 Added the concept that mutations in DNA are what
cause organisms to change or have variations
 Evolution is changes in
DNA that is then inherited
(microevolution)
 Each species has organisms with
varying characteristics for
example:
 some are taller
 some have bigger feet
 some run faster
 some have better vision
 some smell better
 Overproduction of a species causes competition for
resources to survive
 food
 water
 shelter
 space
 Variations may give certain organisms advantages to
survive, while other organisms died
 Nature selects those organisms that will die or survive
 Fossil record
 Biogeography
 Comparative
Anatomy
 Embryology
 Biochemistry
 Similar shape
 Different function
 Shared origin
 Example: arms of human, wings of bats, wings of
penguins, arms of alligators
 Divergent evolution
 Different shape
 Similar function
 Different origins
 Example: wings of a humming bird and wings of a
moth, both allow the organism to hover
 Convergent evolution
 A structure that had a use in an ancestor but has no
use in a particular organism
 Examples:
 Appendix in humans
 Tail bones in humans… we have no tails
 Tiny leg bones in snakes…they have no legs
 Wings in penguins…they do not fly
 Nipples on boys…they do not produce milk
 The study of an organism from creation to birth
 Embryos have
 tails that vanish into their spines
 gill slits, like fish to breath that vanish into ears
 coats of hair that fall off at birth
 2 chambers like fish hearts
 3 chambers like reptiles
 4 chambers like birds and mammals
 A trait that increases an organisms chances of survival
Mutation
2. Migration (gene
flow)
3. Genetic drift
1.


Random events
Small populations
4. Non-random
mating
5. Natural selection-4
types;
 Stabilizing
 Directional
 Disruptive
 Aka diversifying
 sexual
 What leads to these
changes?
 Random mutations
 Organisms w/ shorter
generation times have
higher mutation rates & so
evolve quicker than animals
w/ longer generation times
 Examples:
 Industrial Revolution vs.
Peppered Moth
 those aspects of the environment that can have a
notable impact on the reproduction of members of a
particular species over evolutionary time.
 adaptations
 Different ways for organisms to defend themselves
 Example: thorns on rose bush
 Copying the appearance of another, more dangerous
specie
 Example, the fat bumble bees do not sting, but they
copy the yellow/black appearance of thin bumble bees
that do sting
 The ability of an organism to blend into their
environment
 Example, fish have pale bottoms and dark tops
 Frogs are shades of green