Download Natural selection - Effingham County Schools

Evolution
 Evolution –process through which species
change over time. The process by which
modern organisms (multicellular) have
descended from ancient organisms
(unicellular)
 Jean Baptiste de Lamarck
was the first scientist to
propose a model of how
life evolves
Lamarck’ s theory of acquired
characteristics

Lamarck said
organisms acquired
traits by using their
bodies in new ways

These new
characteristics were
passed to offspring

Lamarck was unable
to provide an
evidence to support
his ideas
Charles Darwin (1809-1882)
Sailed around the world (1831-1836)
Brainpop - Charles Darwin
What did Darwin’s travels
reveal?
 The diversity of living
species was far greater
than anyone had
previously known!!
 Darwin made
observations on his
voyage that later became
the foundation for his
theory of evolution by
natural selection
How did the finches differ
among the islands of the
Galapagos?
 Darwin noticed differences
between the finches on the
island and those of the
nearby mainland
 Each island had its own
type of finch that were
clearly different from the
other islands
 Darwin specifically noticed
the differences in the shape
of their beaks and in the
food they ate
Darwin Thought
 Darwin wondered why
the island finches were
different from the mainland
finches
 He hypothesized that
perhaps some finches were
blown to the island by a
storm and over time the
finches that survived
adapted to different ways
of living on the islands
Darwin Finches
Darwin’s Thoughts
Continued
 Darwin looked to selective breeding for
clues
 selective breeding - humans, not nature,
select which traits will be passed along to
the next generation (a farmer breeds only
his best livestock)
Darwin’s Thoughts Continued
 Darwin proposed that nature works somewhat in the
same way… organisms that are better adapted are
able to survive and reproduce
 So they are somewhat “selected” by nature and pass
their helpful trait to their offspring
 Natural selection – members of a species that are best
suited to their environment survive and reproduce at a
higher rate than other members of the species
Brainpop - Natural Selection
Darwin’s Thoughts Continued
 Mutation – change in the DNA
- mutation causes no effect
-mutation is harmful
-mutation is beneficial
Beneficial mutations allow organisms to
survive and reproduce at a higher rate
Natural Selection Wins!
 In 1859, Darwin published
his results in his book
called On the Origin of
Species by Means of
Natural Selection
 Darwin theorized that
evolution occurs through
a process he called
natural selection
(survival of the fittest)
Natural Selection in 4 Steps
 1. Overproductioneach species
produces more
offspring than will
survive to maturity.
 2. Genetic Variationthe individuals in a
population are slightly
different from one
another. Some traits
increase the chances
that the individual will
survive and reproduce.
Natural Selection in 4 Steps
 3. Struggle to
 4. Successful
Survive - a natural
Reproduction - the
environment does not
individuals that are
have enough food,
well adapted to their
water, and other
environment are
resources to support
more likely to
all the individuals
survive and
born. In addition,
reproduce.
many are killed by
other organisms.
Insecticide Resistance
 Insects quickly develop resistance to
insecticides because they produce many
offspring and usually have short
generation times.
 A generation time is the period between
the birth of one generation and the birth of
the next generation.
In the 50 years that insecticides have been used, more than
500 species of insects have developed resistance to certain
insecticides.
3 Ways Speciation Can Occur
 1. Separation - a
newly formed
canyon, mountain
range, or lake are
a few ways that
populations can
be divided.
 2. Adaptation - if a population has
been separated, the environment may
also change. To live the species must
adapt to the new environment.
 3. Division - over
thousand or millions of
generations, the two
groups of a population
may become so
different that they can
no longer interbreed.
At this point, they are
no longer the same
species.
Peppered Moths of Manchester
 Peppered moths spent most of
their time resting on the bark of
oak tree trunks. Most of the oak
trees in England were light brown,
speckled with green.
 Most of the peppered moths at
that time were light brown too.
 Some dark ones around, but few.
Peppered Moths of Manchester
 Pollution from Industrial
Revolution stained
London trees dark brown
 Suddenly scientists noticed
the population of dark
moths increased, and the
light moths population
decreased
Peppered Moths of Manchester
 Birds were the moths major predator
 Birds can not see moths (prey) that
blend in with tree trunks because they
were camouflaged
 The dark moths reproduced which
increased the population of dark
moths
 Kettlewell- scientist who studied
peppered moths
Fossils are
evidence
of
Evolution!
Fossil Rock
Anthem
Paleontology- study of extinct life
Fossils – remains of organisms preserved in
the earth
Mastadon
Pterosaur
T-Rex
1. Fossils provide evidence
about the history of life
2. Fossils show how
organisms have
changed over time
3. Fossil records are
incomplete because
most organisms die
without leaving any
trace!
Brittle Star
Vestigial Structures
 Vestigial Structures- body
parts that are reduced in
size and have no function
 Whale evolution
 Suggests that as the body
part was no longer needed
in the environment they
were lost or reduced in
size
 Examples
 hip and leg bones in
snakes
 pelvic and femur bones in
whales suggest they once
had back legs
Older fossils are usually
found in the bottom geologic
layer!