chapter 16.1 introduction to evolution and evidence · chapter 16.1 introduction to evolution and...
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Chapter 16.1 Introduction to Evolution
and Evidence
• Vocabulary
– Artificial Selection
– Natural Selection
– Homologous
• Key Concepts
– Who was Darwin and what
was his theory on evolution?
– How structural and
physiological structures relate – Homologous
Structures
– Analogous Structures
– Vestigial Structures
physiological structures relate
to evolution?
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 MendelTheodosius 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?
• Biology
• Paleontology
• Geology
• Genetics• 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 • 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?Species?
– 1859
– So about 200 years
after Ray
Look at the drawings carefully then answer the following questions…
1) What is the main difference you notice about the Galápagos finches?
2) Why do you think this difference exists?
Natural Selection and the Evidence for Evolution (16.1)
• change over time: the process by which modern organisms have descended from ancientorganisms.
DEFINITION OF EVOLUTION:
The Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles Darwin
Portrait of Darwin in 1840 (Darwin 65 years old)
(31 years old)
• Born 1809 (England)
• Completed college after studying to become a doctor but could not stand sight of blood …
The Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles Darwin
stand sight of blood …
• Set sail on 5 year voyage on H.M.S., Beagle in 1831 as the natural historian for expedition.
• 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,
The Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles Darwin
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
• He collected fossils. – noticed some looked like living organisms
– others looked like nothing he had ever seen
The Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles DarwinThe Life of Charles Darwin
– others looked like nothing he had ever seen
before
• Were these related to the living (present day)
organisms?
• Why did some organisms disappear altogether?
Where are the Galapagos?
The Life of Charles DarwinGalapagos 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.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 DarwinThose Who Influenced DarwinThose Who Influenced DarwinThose 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 – 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 populationslimits the growth of human populations• if populations continue to grow
unchecked, they will run out of resources (food/shelter)
Variation &
2 IMPORTANT CONCEPTS TO HELP US
UNDERSTAND THE PROCESS OF
EVOLUTION:
Variation &
Adaptation
VARIATION:
differences
between 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?bear’s survive?
How are the adaptations of 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 ● 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 ● 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
● 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 � 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 – 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, 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– 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)(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
CRITICISM OF
THIS
ASSUMPTION
its lifetime and pass
these changes on.
Implies that an organism
can sense its needs and
change to meet them.
LAMARCK continued…
ASSUMPTION #2
Inheritance of Acquired
Characteristics: acquired
traits can be passed on to
offspring → over time the
CRITICISM OF
THIS
ASSUMPTION
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;
2) Artificial selection
(selective
breeding) -occurs in nature;
competition for
food, space,
mates
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
Variation occurs in
Not all organisms
can survive
Variations are Variation occurs in
all populations
Variations are
inherited
Populations as a
whole become FIT
= evolved!
Organisms with
favorable variations
survive and
reproduce
LAMARCK: DARWIN:LAMARCK:
Individuals
can change
DARWIN:
Evolution
acts on
populations
DARWIN’S THEORY OF
NATURAL SELECTION
1.
ORGANISMS
HAVE MORE
…a herd of giraffes would produce HAVE MORE
OFFSPRING
THAN CAN
SURVIVE
AND…
produce hundreds of descendents over several generations.
2. RANDOM, HERITABLE VARIATION EXISTS AMONG THESE ORGANISMS (EX. (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 …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 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,
The giraffes with
longer necks survive REPRODUCTION,
AND THEREFORE,
THE POPULATION EVOLVES!!!
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 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.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 and hence be “passed down” to the next
generation.
• Countless generations of mutations and
natural selection result in organisms that
have very different structures.
