Download Evolution - Scott County Schools

EVOLUTION – change in populations over time
HISTORY – ideas that shaped the current theory

•
James Hutton (1785) –
proposes that Earth is
shaped by geological
forces that took place
over extremely long
periods of time --estimates earth to be
millions of years old.
Scientist now believe
Earth is 4.6 billion
years old!

Jean-Baptiste Lamarck (1809) – Proposed that
organisms changed over time by the inheritance of
acquired traits.
Lamarck thought that you would gain or
lose features if you used or didn't use them,
and you could pass these new traits onto
your offspring.
PROVEN TO BE WRONG!


Charles Lyell (1833) – processes occurring now
have shaped Earth’s geological features over long
periods of time.
Charles Darwin (1859) – Publishes “The Origin of
Species” explaining his theory of evolution by
NATURAL SELECTION.
From 1831 to 1836 Darwin
served as naturalist aboard the
H.M.S. Beagle on a British
science expedition. In South
America Darwin found fossils
of extinct animals that were
similar to modern species. On
the Galapagos Islands, he
noticed variations among
plants/animals of the same
type in South America.

Natural Selection is the process by which
individuals with beneficial traits survive and
reproduce more successfully than other
individuals, causing those beneficial traits
and the genes that code for them to
accumulate in later generations
Mutations cause variation in traits
More offspring are produced
than can survive
Only individuals with beneficial
traits are able to survive &
reproduce
Over many generations, the beneficial
trait will accumulate, causing the
population to be better adapted to the
environment
Acts directly on an organisms
phenotype and indirectly on its
genotype
“Survival of the Fittest”
Fit: Well adapted; reproductively
successful (good at passing on
its genes to the next generation)
Not necessarily the biggest or
strongest!
Examples of Natural Selection
Example 1: Antibiotic resistant
bacteria
Example 2: Pesticide resistant insects
Example 3: Bill length in
Hummingbirds in response to flower
shape


Over long periods of time, Natural Selection causes
populations of organisms to be better suited to
their environment
The characteristics of an organism that help it
survive and reproduce in its environment are called
adaptations.
Example 1: White fur camoflauges polar bears
Example 2: Harmless snakes mimic the patterns of
venomous snakes
Example 3: Spots on moth wings resemble eyes of a larger
animal
EVIDENCE of evolution

FOSSIL RECORD
◦ Fossil: The preserved
remains of an organism
◦ Fossils are a record of life’s
history.
◦ By comparing fossils from
older rock layers with fossils
from younger layers,
scientists have learned that
life on Earth has changed
over time
• All vertebrates go
through similar
stages of embryonic
development.
• The same embryonic
tissues develop into
the same adult
structures E = hog
F = calf
G = rabbit
H = human
• All life is based on DNA
• All organisms use the
same genetic code
Comparison of Human Hemoglobin to
other species
Species
More closely related
species will have more
similar DNA and amino
acid sequences
Amino acid differences
Gorilla
1
Rhesus Monkey
8
Mouse
27
Chicken
45
Frog
67
Lamprey
125

study of body forms and structures in an organism --This can reveal similarities that suggest inheritance from
a common ancestor.
HOMOLOGOUS
STRUCTURES – structures
have different mature forms,
but have the same
underlying anatomy
• Organisms have
descended from a
common ancestor.
ANALOGOUS STRUCTURES –
structures have similar function
and appearance, but different
anatomy
Similarities are due to
environmental pressures, but
do not demonstrate common
ancestry. Appear due to
convergent evolution
VESTIGIAL ORGANS – organs
that are reduced in size and have
no function.
• Structures have no current
function, but can provide
information about ancestors.


Microevolution: The small changes in a
population from one generation to the next.
Macroevolution: The large-scale changes that
occur in a group of organisms over very long
time periods (i.e. the evolution of birds from
dinosaur ancestors).
Because of macroevolution,
Earth’s biodiversity has
increased over time!

Patterns of Macroevolution
◦ Speciation – New species evolve when different
populations of an existing species become isolated,
diverge (split), and evolve independently for
millions of years.
Adaptive Radiation: Many
new species evolve in a
relatively short time period
when an ancestral population
adapts to new environments.
Adaptive radiation of Darwin’s
finches in the Galapagos
Islands is one example of this
process.

Convergent evolution: the appearance of structures
that have similar appearances and functions in distantly
related species.
• many organisms on different
continents look alike and share
many similarities, but are
unrelated
• The similarities evolved due to
exposure to similar
environmental pressures.

CoEvolution is the joint change of two or more species that
interact closely.
◦ Example - Pollinators & the flowers they pollinate have coevolved
so that both have become dependent on each other for survival.

Mass Extinction – Sometimes many species
go extinct (disappear) in a relatively short
period of time.
There have been 5 mass extinctions in
earth’s history. The most recent took
place 65 million years ago and resulted in
the extinction of the dinosaurs.

Endosymbiosis: The hypothesis that an
ancestral eukaryotic cell engulfed other cells,
which became organelles (mitochondria,
chloroplast).
RATES OF EVOLUTION
Gradualism – organisms
descend from a common
ancestor slowly over a
long period of time.
Punctuated Equilibrium –
new species appear
suddenly after long
periods of little change

CLADOGRAMS/PHYLOGENETIC TREES
Phylogeny: The evolutionary
history of a group of an
organism or group of organism
Phylogenetic tree/cladogram:
Like a family tree. Shows the
evolutionary relationships
between species or groups of
species.
• Branching points represent
the common ancestor of two
groups.
• More closely related species
have common ancestors higher
up on the tree than distantly
related species.