Download Ch. 15, Darwin`s Theory of Evolution

Evolution Unit
• Chapter 15, Darwin’s Theory of Evolution
– Puzzle of life’s diversity
– Ideas that shaped Darwin’s thinking
– Darwin presents his case
• Chapter 16, Evolution of Populations
– Genes and variation
– Evolution as genetic change
– Process of speciation
• Chapter 17, History of Life
–
–
–
–
Fossil record
Earth’s early history
Evolution and multicellular life
Patterns of evolution
Why Care About Evolution?
1. Curiosity about the origins of life, how all the species
came into being, how the living world came into
being.
2. Curiosity about what may happen to the natural world
in the future.
3. Predict what new life forms research will discover in
the future.
4. Evolutionary theory can help predict which
strains of flu, AIDS, and West Nile virus will
be most deadly next year.
5. Desire to learn about all life, past,
present and future.
6. Want to pass this biology class
and the TAKS test.
Definitions to Know
• Scientific Theory = a well-supported, testable Box 1
explanation of phenomena that have occurred in the
natural world.
• Evolution = change over time, the process by which
modern organisms descended from ancient
organisms
Box 2
• Is Evolution Fact or Fiction?
– Scientists believe it’s Fact.
• Proof?
– Fossils
– Speciation
– Geological evidence
– DNA evidence
– Etc.
Charles Darwin (1809-1882)
• British naturalist famous for his theories of
evolution and natural selection.
• Like several scientists before him, Darwin believed
all the life on earth evolved (developed gradually)
over millions of years from a few common
ancestors.
• In 1831, Darwin took a trip around the world on the
ship, the M.S. Beagle, where he collected
evidence that led him to propose his famous
Theory of Evolution.
There’s a huge
tortoise lurking behind
me, interesting. And
he has weird birds on
his back.
Charles Darwin
Box 3
Darwin’s Voyage on M.S. Beagle
Box 4
Ewww,
nasty.
Starting point:
1831, England
Ending point:
1836, England
I spent 5 years on a
ship, can you
imagine what that
was like? What we
all smelled like?
Did you know there are no rabbits in Australia?
No kangaroos in England? No monkeys in
North America? No elephants in Alaska?
Darwin’s observations showed him there were
patterns to the diversity of life on Earth. Organisms
are adapted to the environment where they
Boxlive.
5
Fossils
• Darwin didn’t just observe and collect living animals,
he also collected fossils.
• Fossils = preserved remains of ancient organismsBox 6
• This led to questions like….
– “Where did all these organisms go?” “Why aren’t
they still here?” “Why do they resemble organisms
we have living today?”
This is too much
of a coincidence.
Glyptodon = dead
Armadillo=
alive
Homo sapiens- existed
from about 200
thousand years ago
(TYA) to the present
Australopithecinesexisted between 5 and
2 million years ago
Homo hablis- existed
2.4 to 1.5 million
years ago
Neanderthal man- existed
from about 250 to 30
thousand years ago
Homo erectusexisted around 1.8
million years ago
Do we look
alike?
The Galapagos Islands
• The most important, influential stop onBox 7
Darwin’s trip was the Galapagos Islands
• 1000 km west of S. America, a cluster
of islands isolated by miles of sea
• The islands had different climates, and
therefore, had different varieties of animals
I’m
and
plants
That’s my
lonesome
Box 7
friend Finchy!
George
Animals Darwin studied:
1.
Giant Tortoises
3. Finches
2. Iguanas
Galapagos Turtles
Each turtle lives on a
certain island, and their
shells are different, islanddependent! Brilliant!
Box 8
Pinta
Tower
Marchena
Pinta Island
Intermediate shell Fernandina
Hood Island
James
Saddle-backed shell
Santa Cruz
Isabela
Santa Fe
Floreana
Isabela Island
Dome-shaped shell
Hood
The shape of each turtle’s shell is
different and the different shapes
depend on the turtle’s habitat.
Darwin’s Finches
• Darwin also collected finches, birds, matching their beak and
body shapes with different islands- just like the tortoises.
• Beak shapes in the finches indicated their type of diet, what
Box 9
they ate, and this told him where they lived
Box 10 and 11
The finches of the Galapagos Islands provide a classic example of
Adaptive Radiation —the evolutionary process through which a
single lineage gives rise to species occupying diverse
environmental niches.
In one model of how species form, geographical separation
leads to evolutionary divergence (growing apart).
Tree Finch
Ground finch
In other words, if you get
separated from your own
species, you evolve or change
in response to your
environment.
Darwin’s
Finches
FYI, each beak is
designed for a
different purpose.
Box 12
Leaves
Seeds and Fruit
Seeds
Insects
Grubs
Tool using
Scientists Who Influenced
Darwin
• Discovery of fossils helped shaped the scientists
•
Box 13
of Darwin’s time
2 biologists who influenced Darwin were James
Hutton and Charles Lyell, they helped scientists
Box 14
recognize that:
1. Earth is many millions of years old (Hutton)
2. The same natural process happening THEN are stillBox 15
happening NOW (Lyell)
•
Jean Baptiste de Lamarck
–
–
–
Box 16
Living things have changed over time
Living things respond to their environments
Through either use or disuse, organisms acquired or
lost certain traits during their lifetime, and these traits
could be passed on to the next generation
Thank you. I’m
pretty smart.
Lamarck here,
nicely done
Darwin!
Eeek! It’s the C Gang,
they won’t leave me
alone!
Use it or lost it
Oh, I’ve GOT to
grow that claw!
Look, it’s Crabby,
what a jerk. Hey,
Crabby, you loser!
You just wait! I’ll
get you one day!
Stay away from me!
Hi! I’m Crabby.
I want to be
superior, how
can I do that?
The Next Day……
Ha Ha! Are you
scared? Huh? Are
you scared you little
twerps!
Where are you going?
Run away! Run away!
I know! I’ll grow
a huge claw, and
I’ll squash those
other crabs!
Let’s drop him!
Yeah, thanks dad!
Boy, dad sure did know
what he was doing when
he developed this huge
claw- weapon!
Thomas Malthus (1798)
• English economist who introduced the concept of
human population growth and the problem of too
many people, too little space
• Populations don’t grow uncontrollably,
there is a limit to population growth
• Why do some survive and some die?
She’s about to be shark
bait. Sharks are perfect
predators, perfect
killing machines.
He has no heart, he’s a
mathematician.
Thomas Malthus
Box 17
Too many people,
too little space,
let the shark have
her!
What took him so long? 25 years
later….
• In 1858, Alfred Wallace sent Darwin an essay with the same
Box 18
ideas about evolution!
• They presented their work together at a conference, but….
You stole MY idea!
• This pushed Darwin to publish
Cheat! Thief!
his work, before Wallace
You’re famous and
I’m not!
• The Origin of the Species
– Proposed a mechanism for evolution, called
Natural Selection
– Presented evidence that evolution has
been happening for millions of years
I procrastinated, and
came close to losing my
chance for fame! And I
aged quite a bit.
Shut up Wallace, you sore
loser. Survival of the fittest
and all that.
Artificial Selection and Natural
Selection
• Variation exists in nature and animal and plant breeders use this
Box 19
through artificial selection
– A farmer may like a see a plant with bigger tomato and use
the seeds of that plant for next year’s crop
– Or he may breed the two best milk cows to get a cow who is
an even better producer of milk
• Darwin’s greatest contribution was his concept of natural
selection
• In the struggle for survival, the most fit- the fastest prey, the
strongest predator, the one with the sharpest
Box 21claws, wins the
Box 22
game of survival. Survival of the fittest.
• Fitness = the ability to survive and reproduce in a specific
environment
Box 23
Adaptation = any inherited
characteristic that increases an
organisms chance of survival
How is your fitness?
Did you notice how fat
Wallace was? NOT fit.
Box 20
Proof for Evolution
Beaver
Muskrat
Beaver and
Muskrat
Coypu
• Fossil record = Darwin argued that
the fossil record provided evidence
that living things have been evolving
for millions of years
Box 24
Capybara
Coypu and
Capybara
They all look
like rats to me.
• Geographic Distribution of living
Box 25
species:
Descent with modification, says that
similar species in similar
environments but in different
locations, were products of different
evolution paths
Homologous Body Structures
Box 26
Homolgous structures all•
develop from the same
embryo tissues but have
different functions in the •
adult organism.
What does Homo mean?
– Homo = same, similar
Remember these?
– Homozygous- same allele for a trait, tt, TT
– Homologous chromosomes- same chromosome,
one from mom one from dad
Turtle
Alligator
Ancient lobe-finned fish
Bird
Mammal
Vestigial organs
• Why do we need our appendix?
• It’s useless now, but it may have served some
function in our past
• Vestigial organs = organ with little or no
Box 27
function, left over from the past, ex. appendix
If you can live without
it, with no medical
help, then it’s useless!
Ch. 16, Evolution of Populations
• Why are we all so different?
• Variation in populations is the raw
material for evolution
• 2 main sources of variation:
– Mutations = any change in a
Box 28
sequence of DNA, some are
harmful, some are beneficial and
some don’t have any effect at all
– Gene shuffling = mixing of genes
Box 29
due to random sexual mating
• 23 pairs of chromosomes can
produce 8.4 million different
combinations of genes
• Crossing over during Meiosis
Variation and Gene Pools
• Genetic variation is studied in POPULATIONS,
not individuals
• Members of a population share a Gene Pool
• Gene pool = consists of all genes, including all the
different alleles that are present in a population
– Why?
– They descended from a common ancestor
• Relative frequency of an allele = number of
times an allele occurs in a gene pool
• So, evolution is any change in the relative
frequency of alleles in a population
Box 29
Box 30
Natural Selection and
Speciation
Box 31
• Natural Selection= (Dr. Malone’s definition) when Write as much as you
want from this
individuals who have what it takes survive and
paragraph
reproduce best; survival of the fittest, it’s a dog eat
dog, you got to step on someone else to get where
you want to go, world
• Founder Effect = when a population shrinks down toBox 32
only a few members, then rebounds so all of the
future members have the “founder’s” genes
• Speciation = when natural selection and Box 33
other random effects lead to the creation
of a new species
– Reproductive Isolation = populations become
reproductively isolated from each other, so it
Box 34
leads to evolution of a new species
This is why cats and dogs can’t
have cat-ogs, or is it do-cats?
Dogats? Cadogs?
If all our women moved to
China, could we continue to
interbreed? Ha ha. Don’t
think so!
Speciation
• Behavioral Isolation = when two populations can
interbreed, but their different behaviors, or
reproductive strategies, just don’t turn each other
on, get it?
• Geographic Isolation = two populations are
separated by geographic barriers, like mountains or
oceans and they can’t interbreed
•Temporal Isolation = two populations are
separated by different reproductive
I say go
It’s tootimes
Move mountain!
Move mountain!
far to fly!
for it!
Box 35
Box 36
Box 37
Ch. 17, The History of Life
Box 38
• Paleontologists (pay-lee-un-TAHL-uh-jists) =
scientists who study fossils, history written into
stone
• The fossil record:
– Provides evidence about the history of life
on Earth
– Shows how species have changed over
Box 39
time (evolved)
• 99% the species that have lived on Earth
Box 40
are extinct!!!!
• Fossils form in sedimentary layers of rock
– Fossils at the top are younger than fossils
at the bottom, common sense,
I’m extinct. There are and will
or relative dating
be no others like me, it’s so
tragic.
Help!
Box 43
How old are Fossils?
Box 41 and 42
Half-Life = length of
time it takes for ½ of
the radioactive atoms
in a sample to decay
• Relative dating is comparing fossils with other
fossils to see estimate the age of each, but it’s not
very precise
• Radioactive Dating- calculating the age of fossils
based on the amount of remaining radioactive
isotopes they contain
Do you remember?
Isotopes = an element with a different number of neutrons in its atom
How many
neutrons in C-12?
6
Carbon-12
6
Carbon-14
6
C
12
How many neutrons in C-14?
C
14
Radioactive!!!
8
Geologic Time Scale
You are HERE
Era
(millions of
Period
Time years ago)
Era
1.8–present
Tertiary
65–1.8
Cretaceous
145–65
Devonian
410–360
Jurassic
208–145
Silurian
440–410
Triassic
245–208
Ordovician
505–440
Cambrian
544–505
Box 44
Paleozoic Era
Mesozoic Era
Cenozoic Era
Permian
Era
290 – 245
Quaternary
Geologists divide the time
between Precambrian and the
present into 3 eras:
1.
2.
3.
of
Time (millions
years ago)
Period
Carboniferous 360–290
Which era does Tyrannosaurus
Rex belong to?
Jurassic
Period
Time
Vendian
650–544
Patterns of Evolution
•
•
Macroevolution = large-scale evolutionary patterns
occurring over long periods of time
Important topics in macroevolution:
1. Extinction = over 99% of all species that have
ever lived on earth are now dead, extinct.
2. Adaptive Radiation = a single species evolving
over time into diverse forms that live in different
ways
Box 45
Box 46
Macroevolution Cont.
3. Convergent Evolution = unrelated organisms come
to resemble one another
Box 48
4. Co-evolution = process by which 2
species evolve in response to changes in
each other over time
-Predator- prey pressures, what food is
available, pollination, etc.
Box 47
Macroevolution Cont.
Box 49
5. Punctuated equilibrium = the pattern of long stable
periods of time interrupted by brief periods of more
rapid change
Yikes! I’m outta
here! He’s crazy!
Hee hee! I’m coming
to get you!