Download Evolution - Newark City Schools

Evolution
• The processes that have
transformed life on earth from
it’s earliest forms to the vast
diversity that characterizes it
today.
• A change in the genes!!!!!!!!
The one scientist who is most
well known for evolution is
Charles Darwin
He did not reach this conclusion on his own…
Ideas that helped shape
Darwin’s thinking
• James Hutton – Theory of geological change.
• He proposed that the earth is shaped by geological
forces that took place over extremely long periods of
time. He estimated the earth to be millions of years
old, not thousands (as previously thought).
• This idea led Darwin to realize that
if the earth was millions of years
old (not thousands), it would mean
there was enough time for
organisms to evolve.
Ideas that helped shape
Darwin’s thinking
• Charles Lyell published “Principles of
Geology”.
• Explained that the processes occurring now have
shaped earth’s geological features over long
periods of time. These processes are still
changing earth today.
• This idea led Darwin to
realize that if the earth
could change then so
could life
Ideas that helped shape
Darwin’s thinking
• Jean Baptiste Lamarck (early 1800’s) proposed:
“The inheritance of acquired characteristics”
• He proposed that
by using or not
using its body
parts, an individual
tends to develop
certain
characteristics,
which it passes on
to its offspring.
Ideas that helped shape
Darwin’s thinking
• First scientist
to propose a
mechanism for
how organism
change.
• HE WAS
WRONG!!!
Ideas that helped shape
Darwin’s thinking
• Thomas Malthus – Predicted
that the human population will
grow faster than the space and
food supplies needed to
sustain it.
• This same prediction applies to
organisms in nature as well
and leads to competition
among them
Charles Darwin
• With this information in his mind Darwin set sail
on the H.M.S. Beagle (1831-1836) to survey the
south seas to collect plants and animals.
• On the Galapagos Islands, Darwin observed
species that lived nowhere else in the world.
Charles Darwin
• Even though the islands are fairly close
together they have different environments.
Varying from lush jungle to bare volcanic
land.
Charles Darwin
• In these different environments Darwin
found different types of animals
– Finches were very different on each island
– Tortoises had very different necks on each
island
Charles Darwin
• Charles Darwin is credited with the theory of
evolution, but scientists knew that organisms
change over time before Darwin…..what
Darwin really came up with is the mechanism
for change (HOW organisms changed over
time)
Darwin’s observations on
the Galapagos and his
knowledge that things
change over time led him to
write a book….
Charles Darwin
• Wrote in 1859: “On the Origin of Species
by Means of Natural Selection”
• Two main points:
1. Species were not created in their
present form, but evolved from ancestral
species.
2. Proposed a mechanism for evolution:
NATURAL SELECTION
Natural Selection
• Individuals with favorable traits are
more likely to leave more offspring
better suited for their environment.
Example: Peppered moth
• Has both dark and light
types
Natural Selection
• Overtime, natural
selection results in
changes in the
inherited
characteristics of a
population.
• These changes
increase a species
fitness (survival rate)
Natural Selection
• Natural selection is also sometimes called “survival
of the fittest". In this case, “fittest” does not
necessarily mean fastest, strongest, etc… “Fittest”
simply means the organism has a trait that helps it
survive and reproduce (called an adaptation)
•
•
If you are a turtle “fittest” might
mean strongest shell
If you are a chameleon “fittest”
might mean best camouflage
Artificial Selection
• The selective breeding of domesticated
plants and animals by man.
• nature provides variation, humans select
variations that are useful.
• Example - a farmer breeds only his best
livestock
Evidence of Evolution
1. Fossil Record:
Fossils, and the order
in which they appear in
layers of sedimentary
rock, show the history
of life on earth and
how different groups of
organisms have
changed over time
Evidence of Evolution
2. Biogeography:
Geographical distribution of
species. Similar animals in
different locations were the
product of different lines of
descent
Evidence of Evolution
3. Homologous Structures:
Structures that are similar
because of common ancestry.
e.g. Wing of bat,
human arm, leg of
turtle
Provides strong evidence that all
four-limbed animals have
descended, with modifications,
from a common ancestor
Evidence of Evolution
3. Homologous Structures:.
Not all homologous structures
serve important functions. The
organs of many animals are so
reduced in size that they are just
vestiges, or traces, of homologous
organs in other species. These
vestigial organs are organs that
serve no useful purpose in an
organism
e.g. pelvic bones in whales, appendix,
wisdom teeth and coccyx in humans
Evidence of Evolution
4. Comparative embryology:
In their early stages of development,
chickens, turtles and rats look similar,
providing evidence that they shared a
common ancestry.
Evidence of
Evolution
Evolution can be observed
all around us…..