Download Ch15 Evolution

Evolution
Natural Selection and
Evidence of Evolution
Charles Darwin
 Born February 12th, 1809
 A naturalist, he studied all things of nature.
 Voyage of the H.M.S. Beagle
 Made observations and collected evidence towards
THEORY of EVOLUTION
Evolution: Darwin
Darwin’s Theory:
Natural Variation: Differences
among individuals of a species
Ex. Aquilegia flowers
Artificial Selection: Nature
provides variation among
different organisms, humans
select
Ex. Largest hogs, fastest horses
*Natural Selection favors traits
that benefit organism in
environment Environment
does “selective breeding”
Evolution: Darwin
Fitness: ability to
survive & reproduce in
environment
Adaptation: inherited
characteristics that
increases organisms
chance for survival
Survival of the Fittest
(natural selection):
Individuals better suited
to environment, with
high level of fitness,
survive and reproduce
successfully
Natural Selection: struggle for existence.
Evolution:
Darwin
vs.living
Lamarck
Species
compete
for food,
space…etc.
(mutations & genetic recombination lead to this)
Don’t copy
*Over time, natural
selection results in
changes in the
inherited
characteristics of a
population.
These changes
increase a species
fitness in its
environment.
Steps of Natural Selection
• Variations within a population are raw
material for natural selection
Ex: giraffes with different necks
lengths competing for food
Next…
• Living things face a constant
struggle for existence and produce
a lot more offspring than can
survive
Ex: Giraffes with longer necks reach
leaves in tall trees
Then…
• Only some individuals survive and
reproduce; best genetics produce
offspring
Ex: Giraffes with longer necks were
better at getting food therefore had
more offspring
So…
• Natural selection causes genetic change;
in every generation the amount of
individuals with better traits survive
Ex: Over time long necked giraffes replaced
short necked giraffes
Finally we can say..
• Species adapt to their environment;
selection tends to make the population
more suited to its environment
Ex: Longer necked giraffes are more
successful and becomes the trait for a
successful population
Evolution: Darwin
Descent with modification: species different from their
ancestors; living species descended with changes
from other species over time (GRADUALISM)
Common Descent: all species were derived from
common ancestors meaning a “single tree of life”
Evidence for Evolution:
Common Ancestors
Evidence for evolution: Common Ancestor
1. Fossil Record:
• Darwin believed living
things evolved for
Millions of yrs.
• fossils provide evidence
of Earth’s changing life
Evidence for Evolution: Common Ancestor
2. Geographic Distribution of living things:
Darwin’s finches were so similar, lived in different
places, birds descended with modification from
common ancestor
Living on diff.
continents, same
ecological
condition, similar
pressures from
natural selection
ended up
evolving common
features
Analogous Structures
• Similar in function, different embryonic origins
• Result of convergent evolution (similar environment)
• Ex. Butterfly wing, dragonfly wing, bat wing, bird wing
Evidence for Evolution: Common Ancestor
3. Homologous Body Structures: Similarities among bones
of different organisms; different form and function;
limbs adapted to different environments; common
ancestor
-Structures that originally functioned one way in ancestral species become
modified as they take on new functions; proves evolution “remodeling
process”
Evidence that all four
limbed animals with
backbones descended
with modifications
from common
ancestors.
Create “trees” showing
how recently last
shared common
ancestor
WHALE
HUMAN
Bones develop
from same cell
in embryonic
development
BAT
Evidence for Evolution: Common Ancestor
4. Vestigial Organs: No
function; reduced in
size; No affect on
survival so natural
selection doesn’t
eliminate
Vestigial Structures in Humans
Evidence in Evolution: Common Ancestors
5. Similarities in early
development: embryo of
animals with backbones
very similar. Embryonic
cells develop in same order.
Proves descent with modifications
from common ancestor.
Bird and human
Evidence for Evolution: Common Ancestors
Genetic Similarities
• The closer related the organisms, the less the
differences
• Test DNA and protein sequences
• Ex. Amino acids that differ in Hemoglobin of different
organisms
Natural Selection and Pesticides
Evidence for Evolution: Common Ancestors