Download NOTES: CH 16 - Intro to Evolution

NOTES: CH 16 – Darwin’s
Theory of Evolution by
Natural Selection / Evidence
for Evolution
• Vocabulary
– Artificial Selection
– Natural Selection
– Homologous
Structures
– Analogous Structures
– Vestigial Structures
How many scientists are involved in developing the
theory of evolution?
William Bateson
Carolus Linneaus
George Buffon
Charles Lyell
Watson and Crick
Thomas Robert Malthus
Hugo de Vries
Ernst Mayr
Theodosius Dobzhanky
Gregor Mendel
Eldredge and Gould
John Ray
J.B.S. Haldane
George Simpson
Hardy and Weinberg
G. Ledyard Stebbins
James Hutton
Alfred Russel Wallace`
Thomas Huxley
Alfred Wagner
Jean Baptiste Lamarck
What kinds of sciences did these
scientists study?
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Biology
Paleontology
Geology
Genetics
Botany
Naturalists
Microbiology
Biochemistry
Molecular chemistry
Ecology
Chemistry
When did the theory of evolution
begin to develop?
• Late 1600’s with John Ray
– Major contribution was his
writings called Historia
Plantarum
• Rejected the system of
dichotomous division
where species were
classified by a
preconceived type of
system
• Instead, plants were
classified by similarities
and differences from
observation
• Coined the term “species”
• When did Darwin
write Origin of the
Species?
– 1859
– So, about 200 years
after John Ray
NOTES: CH 16 – Darwin’s
Theory of Evolution by Natural
Selection / Evidence for
Evolution
DEFINITION OF EVOLUTION:
● change over time: the process by which modern
organisms have descended from ancient
organisms.
The Life of Charles Darwin
Portrait of Darwin in 1840
(31 years old)
(Darwin 65 years old)
The Life of Charles Darwin
• Born 1809 (England)
• Completed college after
studying to become a
doctor but could not
stand sight of blood …
• Set sail on 5 year
voyage on H.M.S.,
Beagle in 1831 as the
natural historian for
expedition.
The Life of Charles Darwin
• Made extensive drawings and notes
on the trip but also collected many
species of plants and animals.
• Began to OBSERVE that animals were well
adapted to their environments,
(wondered why were different animals found in areas that appeared to
be similar in climate? and some survived while others did not?)
• Argentina
• Australia
• Europe
All had grasslands but very
different animals
The Life of Charles Darwin
• He collected fossils.
– noticed some looked like living organisms
– others looked like nothing he had ever seen
before
• Were these related to the living (present day)
organisms?
• Why did some organisms disappear altogether?
The Life of Charles Darwin
Galapagos Islands
Organisms Darwin Observed on the Galapagos
• Land Tortoise = different shaped carapace (shell)
depending what island they inhabited.
• Finches = different shaped beaks depending on
environment in which they lived.
• he realized that characteristics of many animals and plants
varied noticeably among the different islands of the
Galapagos.
• On the journey home he began to pose the question…
– Could animals on the different islands once
have been members of the same species?
Those Who Influenced Darwin
Hutton (Geologist)
– Geologic processes operate extremely slowly (take
millions of years!)
– therefore, the earth is very old
Lyell (Geologist)
– Scientists must explain past events in terms of
processes that they can actually observe
• processes that shaped the Earth millions of years
ago continue to shape present day Earth
• this explained how geological features can be built
or torn down over long periods of time.
Darwin wondered…
• If the earth could change over time, could life
change as well?
• Also: it must have taken many, many years
for life to change the way Darwin had in mind
– This would only be possible if the earth was very
old…
Those Who Influenced Darwin
Malthus (Economist)
• proposed that war, famine, disease,
limits the growth of human populations
• if populations continue to grow
unchecked, they will run out of
resources (food/shelter)
2 IMPORTANT CONCEPTS TO HELP US
UNDERSTAND THE PROCESS OF
EVOLUTION:
Variation &
Adaptation
VARIATION:
differences
between
individuals in a
population
Give me an
example,
PLEASE!!
ADAPTATION: inherited
characteristic that increases an
organism's chances of survival
EXAMPLES OF ADAPTATIONS!
What are some
adaptations this
polar bear has?
How do they
help polar
bear’s survive?
How are the adaptations of
this bear different than those
of the polar bear?
What are some
adaptations of a
cactus?
What about this
desert plant?
What helps this kelp crab
survive? (It lives on the kelp
in the ocean.)
What the
heck are
these?
EVIDENCE FOR EVOLUTION
1) Fossils:
● evidence of once-living things (shells, casts,
bones, teeth, imprints)
● show a succession of forms through a vast span of
time
● progressive changes based on the order they were
buried in sedimentary rock
few fossils / species  many fossils/ species
simple organisms  complex organisms
EVIDENCE FOR EVOLUTION
2) Biogeography and age of the earth:
● distribution of plants & animals
 13 species of finches on the 13
Galapagos Islands
 57 species of kangaroos…
all in Australia!
2) Biogeography and age of the earth:
● Radioactive dating tells us the earth is
about 4.6 billion years old
● Rate of motion of tectonic plates
3) Adaptations: Evidence for Evolution
● MIMICRY: one species resembles another
● CAMOUFLAGE: enables species to blend
with their surroundings
● PHYSIOLOGICAL: ability to resist disease
or drought
4) “Artificial Selection”
4) Applied Genetics ("artificial
selection"):
● Darwin noticed that farmers “selected”
the best crops, animals – he wondered
if there could be a “selective” force in
nature
● today we see DDT-resistant insects;
antibiotic-resistant bacteria
5) Anatomical Structures:
Evidence for Evolution
5) Homologous and Vestigial Structures
5) Homologous Structures =
shared common anatomical or biochemical traits
ex: " forearm bones”
• structures that develop from the same clumps of cells
– later develop into structures that have different forms and
functions
• arms, flippers, & wings look very similar at the
beginning of development, but differ as the animal
matures
– The function differs as well!
5) Vestigial Structures:
structures that no longer serve a purpose in an
organism
 ex: wisdom teeth, tailbone, appendix, nictitating
membrane, some pythons & boa constrictors have tiny
leftover leg bones (and whales!)
 koala's have a large functioning appendix (eat
primarily plant materials)
6) Embryological Development
• Similarities of vertebrate organisms in early
stages of development
• All animal development begins in the same way
(from the same ball of cells)
– BUT recognizable features for that species
develop as the organism grows
•
7) Cellular and Molecular Evidence:
Cellular Evidence
• All organisms are made of cells
– consist of membranes filled with water containing
genetic material, proteins, lipids, carbohydrates,
salts and other substances
7) Cellular and Molecular Evidence
Molecular Evidence
• the DNA code links all life on Earth to a
common ancestor
– DNA and RNA = simple four-base code that
provides the recipe for all living things
• Transfer genetic material from the cell of one
living thing to the cell of another
– the recipient would follow the new instructions as if
they were its own
• EX: Roundworms share 25% of their genes with humans.
Protein Sequence Similarities!
Review—major evidence for evolution
• Fossil record
• Biogeography and age of the earth
(using radioactive dating)
• Adaptations
• Artificial Selection
• Homologous structures and vestigial organs
• Embryology
• Cellular and Molecular Evidence
EVOLUTION:
DARWIN vs. LAMARCK
LAMARCK’s explanation on evolution
ASSUMPTION #1
Law of Use and Disuse:
an organism can change
certain body parts during
its lifetime and pass
these changes on.
CRITICISM OF
THIS
ASSUMPTION
Implies that an organism
can sense its needs and
change to meet them.
LAMARCK continued…
ASSUMPTION #2
CRITICISM OF
THIS
ASSUMPTION
Inheritance of Acquired
Characteristics: acquired
traits can be passed on to
offspring  over time the
population changes.
Suggests that changes in
body cells can be
inherited / passed down.
2 factors that helped DARWIN
formulate his explanation
1) Overproduction
of offspring
occurs in nature;
competition for
food, space,
mates
2) Artificial
selection
(selective
breeding) Darwin wondered
if a similar force
existed in nature.
Charles Darwin’s Explanation on Evolution
(six major ideas of Darwin)
Overproduction
occurs in nature
Not all organisms
can survive
Variation occurs in
all populations
Variations are
inherited
Organisms with
favorable variations
survive and
reproduce
Populations as a
whole become FIT
= evolved!
LAMARCK:
Individuals
can change
DARWIN:
Evolution
acts on
populations
DARWIN’S THEORY OF
NATURAL SELECTION
1.
ORGANISMS
HAVE MORE
OFFSPRING
THAN CAN
SURVIVE
AND…
…a herd of
giraffes would
produce
hundreds of
descendents
over several
generations.
2. RANDOM,
HERITABLE
VARIATION
EXISTS AMONG
THESE
ORGANISMS
(EX.
MUTATIONS),
SO…
…by genetic
“chance”, some
giraffes were
born with
longer necks.
3. BECAUSE
THERE IS A
STRUGGLE FOR
EXISTENCE
(COMPETITION),
THEN…
…giraffes were
competing for
food source
(vegetation).
4. THE
ORGANISMS WITH
FAVORABLE
VARIATIONS (THE
“FITTEST”)
SURVIVE AND…
…a long neck
enabled giraffes to
reach an
“untapped” food
source…tree tops!
(short-necked
giraffes ran out of
food and starved)
5. GENES FOR
FAVORABLE
FEATURES ARE
PASSED TO
OFFSPRING
THROUGH
REPRODUCTION,
AND THEREFORE,
THE POPULATION
EVOLVES!!!
The giraffes with
longer necks survive
and pass their genes
(for longer necks) on
to their offspring…the
process continues,
and whole population
EVOLVES.
AND, if populations are
geographically isolated,
changes will accumulate to
the point of reproductive
isolation
( NEW SPECIES!!)
EVOLUTIONARY CONCEPTS
• Mutations, genetic recombination, crossing
over, etc. are “accidents” in the genes of
organisms. They do not appear according to
any purpose; they just happen.
• Mutations cause a large amount of variation
among organisms in a population.
• There is room on Earth for only a fraction of
organisms that are born or hatched. The
individuals which happen to have the
mutations giving them the best adaptations to
the environment will be the ones that survive.
EVOLUTIONARY CONCEPTS
• The survivors will have their own offspring.
The offspring will be subject to their own
random mutations. Again, only the most
advantageous mutations will result in the
survival of the next generation of offspring,
and hence be “passed down” to the next
generation.
• Countless generations of mutations and
natural selection result in organisms that
have very different structures.