Transcript Theories of Evolution

• Welcome to the World of Evolution
• Evolution just means that a species
changes over time.
Types of Evolution
 Geographic Evolution – gradual,
continuous change in the physical earth
over the last 4.5 billion years.
 Organic Evolution – the gradual,
continuous change in living organisms over
long periods of time.
 Evolution attempts to answer the question:
“How did life begin and how has it changed
into the millions of species living today?”
Theory of Evolution
Theory: idea supported by scientific
evidence over a long period of time.
Evolution: Change in a species due to DNA
mutation over a long time.
Mutations: accumulate as time goes on until
a new species is formed.
Scientist have collected evidence
Six types of evidence:
1. Fossils
2. Comparative anatomy
3. Comparative embryology
4. Comparative Biochemistry
5. Plate Tectonics
6. Adaptations
1. Fossil Evidence: Once living remains of
organisms
But its Limited:
• Incomplete record
• Easily disrupted (erosion)
• Not all organisms get fossilized.
Types of Fossils:
1. Preserved in Amber
or Ice
2. Bones
3. Petrifaction
4. Imprints – most
abundant kind of
fossil.
• Most fossils are found in
sedimentary rock – formed
when water flows over
land,
• carrying the sediment (and
whatever life form) into a
body of water.
• Over time pressure turns
the sediment into rock,
preserving what’s inside.
Formation of Sedimentary
Rock
Section 17-1
Water carries small
rock particles to lakes
and seas.
Go to
Section:
Dead organisms are
buried by layers of
sediment, which
forms new rock.
The preserved
remains may later
be discovered and
studied.
2.Comparative Anatomy:
comparing body parts in different
species.
A. Homologous Body Structures – same bone
structure but different functions.
Example – wing of bird, flipper of whale,
human hand.
Why? Same ancestors that evolved in different
environments.
A. Homologous Structures: bone
structures are almost identical but used
differently.
B. Analogous Body Structures – same function but totally different
structure.
Example – wing of bat, wing of a butterfly.
B. Analogous
Structures
• Different underlying
structures because
they have different
ancestors.
• Same function
because they evolved
in similar
environments (air)
Comparative Anatomy Structures:
Homologous:
1. Different ancestors 1. Same ancestor
2. “analogy”=like
2. “homo”=same
3. Different
3. Same underlying
underlying
structures
structures
4. Different Functions
4. Same Function
5.
Evolved
in
Different
5. Evolved in Similar
Environments
Environments
Analogous:
C. Vestigial Organs: organs or traces of organs
that serve no purpose.
Example – hip bone and leg bone in whale
Whale evolution
C. Vestigial Organs: traces of organs that we evolved
away from needing.
• Example: human tailbone: no longer have tail.
• Human appendix: was used to digest raw meat
3. Comparative embryology:
Similar embryo development between
species
Human
Mouse
4. Comparative Biochemistry
• Proteins of all living things are made from the
same 20 amino acids.
• All organism have DNA made of the same four
bases: GCAT
• Includes the same sugar-phosphate backbone.
• Similar Genes /DNA sequences (order of base
pairs)
5. Plate Tectonics
• continents were one large,
single land mass called
Pangea.
• explains closely related
species on separated
continents.
• Ex. Grizzly Bear and
Panda Bear
6. Adaptations: Traits that
help them survive is a
particular environment
Example 1: Inuit people,
who live in the extreme
cold of the Arctic, have
short, thick bodies that
hold in heat
Masai people who
live in the hot,
dry lands of
Africa have tall,
lean bodies that
release heat
easily.
Example 2:
Plant Adaptations
Venus Fly Trap
• Captures animals to
supplement what is
missing from its
environment.
• Acquires minerals
needed for
photosynthesis
Leaf Adaptations:
Succulents: found in areas
with little rain fall.
• Thick leaves
• Store water, to prevent
drying out
Pine Needles
• Shed snow
• Less water loss
• Tolerate wind
Flower Adaptations:
Fly pollination:
• Hair along petals
• Putrid smell
Bee pollination:
• Smooth petal
• Sweet smell
Example 3: Bird Beak
Adaptations
DESCENT WITH
MODIFICATION: Each
species has descended, with
changes, from other species
over time.
All living organisms are related
to one another.
Similar DNA codes, Similar
amino acid sequences, similar
body parts and internal
structures.
• Actual tree of life is
much more complex
that even this.
• 99.9% of all species
that have ever existed
are extinct.
• Common descent – all
species – living and
extinct – were derived
from common
ancestors.
• Humans did not evolve
from apes.
• We have a common
ancestor that was
neither human nor ape.
Theories of Evolution:
• Lamarck
• Malthus
• Darwin
• Jean-Baptiste Lamarck
•
One of the first to try to
describe why things change
over time AKA evolution
• Two ideas
1. Use & Disuse
2. Inheritance of Acquired Traits
Both are INCORRECT
1. USE and Disuse – use of a body part would
make it evolve, disuse (no use) would make it
disappear.
2. Ex. USE – Birds use front limbs for flying grows wings.
• Ex. DISUSE – If birds stopped using wings, –
they would decrease in size and disappear over
time.
INCORRECT
Lamark said “Use of
structure results in
evolution
• When a giraffe
stretches its neck for
this high leaves, it
grows bigger from
parent to offspring.
USE AND DISUSE
2. INHERITANCE Of ACQUIRED TRAITS:
Lamarck claimed that if a body part was altered then
it would be passed on to the offspring.
• Ex. If you work out and gain muscle mass – your
offspring will be just as big.
• Disproved by Weisman – he cut off the tails of mice
and mated them. Babies born with tails.
Thomas Malthus’s talked about
population
This influenced Darwin big time.
• 1798 said that babies were being
born faster than people were
dying.
• The population explosion would
lead to competition for food and
space.
• Famine, war and disease are our
only threats.
Malthus’s Contribution
to Darwins:
• Populations grow to a
maximum level
• Food and land become
scarce leading to
competition.
• Fit animals outcompete the less fit
Charles Darwin’s explanation:
Natural Selection:
“Survival of fit”
1. Fit: best traits for certain
area
2. Fit out compete others food,
space and mates
3. they reproduce and babies
have same traits: best fit
4. Best adapted species survive
5. Less fit die: starve,
predators, illness
How did he come up with natural
selection?
• 1831 set sail on H.M.S. Beagle to voyage
around the world.
• He made many observations, collected
samples, and made many hypothesis's about
changes in life over time = evolution
• His explanation is called NATURAL
SELECTION.
VOYAGE OF THE BEAGLE 1831-1836
DARWIN’S VOYAGE
• In 1835 he landed in the Galapagos
Islands.
• What he observed and recorded, along
with the specimen he took, changed the
world
WHAT DID DARWIN
SEE?
• In the Galapagos Islands he
noticed the diversity of life
on Earth.
• Many, many different types
of animals
• Some were similar to
animals on the mainland of
South America
PATTERN’S OF DIVERSITY
• Saw different species with similar traits.
• All of the islands were close together but were
very different.
• Tropical, marine, jungles, and mountainous.
• Finches were in all of these places but each
looked a little different.
• Ground Finches
have crushing
beaks,
• They lived in
environments with
seed.
• Crushing beaks
could easily break
the shell seed.
• The Warbler
Finch has a
probing beak.
• It good at digging
into trees and
catching insects
• They are a
different species
but similar
• Darwin noticed
similarities and
differenced on
other animals as
well
• Tortoises
• Iguanas
• Marine iguanas:
long slender tails
for swimming.
• Eat mostly food in
the water and have
to swim to catch it
• Tree iguanas: short tails,
climbing feet.
• Ate food in trees
• Each had traits best for their
environment
• Tree iguana could not feed
easily in the ocean
• Marine Iguana might
struggle in the tree
• They are a different species
but similar.
• Darwin began to wonder if all the
finches were part of the same species
at one time
• The tortoises and iguanas too.
• And the environment must play some
role.
• His conclusion: animals have
different traits such as the finch
beaks because they adapted to a
changing environment.
• They were at one time, part of
the same species.
• They branched out to different
environments and changed over
time, as the environment
changed.
• Those birds with well adapted
beaks to a specific environment
survived those without died.
DARWIN’S
THINKING
• During this time
Darwin was seen as a
radical for his views.
• Europeans thought
that robins always
looked as the do and
never changed
DARWIN PRESENTS HIS
CASE (not in notes)
• 1858 he received an essay
from Alfred Russel Wallace
(naturalist)
• He summarized what
Darwin was doing for 25
years and was going to
publish his own findings.
PUBLICATION OF ON THE
ORIGIN OF SPECIES (not in
notes)
• Darwin wanted to beat him and
published his works (1859).
• He said evolution had been
taking place for millions of years
& continues.
• He proposed the theory of
NATURAL SELECTION.
• Wasn’t received well by the
nonscientific community.
Natural selection:
The environment is always
changing. It selects which traits
will allow an organism to be
successful and survive to pass
on those traits.
Those organisms with the most
beneficial traits are the “most
fit” to their environment
• Individuals with low levels of
fitness = die
• Individuals with high levels of
fitness = live
5 parts of Natural Selection
1.
2.
3.
4.
5.
Overproduction
Competition
Variations
Adaptations
Speciation
1. Overproduction: more individuals are
born than the environment can support
•
•
•
•
Resources such as food, water, and space are
limited.
This leads to competition.
Some species reproduce so fast, and would
overpopulate the earth.
Some must die.
2. Competition: members of a species
must compete for limited resources to
live.
• A STRUGGLE FOR EXISTENCE
• Members of each species compete regularly
for food, space, sunlight, mates etc
Faster deer to escape predators.
Animals hide using camouflage?
Beak shaped for food.
3. Variation: differences found in individuals of the
same species.
• Example: finch beaks, insect colors
• Much variation is found in nature.
• Some variations make organisms better able to
survive in their environments.
• Put those same organisms in another environment
and they die
• They get out competed by other organism better
adapted to that environment.
4. Adaptation: because of the variations or
differences, some organisms are better adapted
to their environment.
Ex: crushing beaks are good in areas with seeds,
long slender tails are good in areas with water.
• Fitness – the ability of an individual to survive
and reproduce in it’s environment due its traits
• Survival in nature – live long enough to pass
genes on to offspring.
• Traits that make organisms successful are
passed to the next generation
5. Speciation: a new
species is created when
enough time has passed.
• over time, variations that
make a species successful
accumulate
• Eventually, the entire
species is different than it
was.
• the changes become so
great, a new species is
formed.
SUMMARY OF DARWIN’S THEORY
• Individual organisms differ from on another.
• Organisms produce more offspring than could
survive.
• Members of each species must complete for
limited resources.
• Organisms have different advantages in the
struggle for existence.
• Individuals best suited for their environment
survive.
• Species change over time.
• Species alive today have descended with
modifications.
• All organisms have a common ancestor.
MODERN THEORY OF EVOLUTION –
Darwin’s theory was correct, but he couldn’t
explain “WHY” evolution was.
He didn’t know about DNA
Where do variations come from?
• Variations - Differences in traits
• They come from mutations in DNA
(genes)
• They are Random
• Must occur in sex cells to be passed on
to future generations
POPULATION GENETICS
• Evolution happens to populations, not
individuals.
• Population – organisms of the same species
living together in a given region that can breed.
• As individuals reproduce and die, the genetic
makeup of the population changes.
• As the genes of a population changes from
generation to generation, the population
EVOLVES.
Sources of Variation in a population
1. Mutations: mutations are the reason for
genetic change and therefore evolution.
Darwin did not know about DNA
2. Sexual reproduction: new combinations of
DNA bring about new traits.
3. Migration: individuals moving in & out of a
population.
What is a species?
• To be part of the same
species, organisms
must:
• Show similar
characteristics
• Successfully
interbreed
• Producing fertile
offspring
Donkey + Horse=
Mule (infertile)
Geography and Speciation
Speciation: creation of a new species. It
can occur naturally over a long period of
time.
• Each species is found in a certain range.
• In different parts of the range, characteristics of the
species can vary.
• The organisms must be able to adapt to the
particular conditions in which they live.
• Differences may include: body size, coloration,
behaviors.
How long does evolution
take?
• 2 theories:
1. Gradualism
2. Punctuated equilibrium
1. Gradualism
Small gradual
changes over a
long period of
time
gradualism
2. Punctuated
Equilibrium
• Large changes that
happen rapidly
• Followed by long
periods of no
change
Punctuated equilibrium
Graphs showing time frame of
Evolution:
• Gradualism:
#
S
P
E
C
I
E
S
Time
• Punctuated Equilibrium
#
S
P
E
C
I
E
S
Time
• Adaptive Radiation: the process by which
species evolve into a # of different species,
each occupying a different niche or living
area.
• “radiation”= branching from one source
• “adaptive”= traits which promote survival
• One species branches out
to different environments
and over many
generations, each changes
in its own way.
• Each eventually becoming
its own unique species.
• (they will be different
species, but share traits in
common).
• Example – Darwin’s
finches
Common Ancestor: all living organisms have a
common ancestor and all life can be traced back to
one original cell.
• Common ancestor mean that living things can be
traced back to a common relative.
• Example: Humans did not evolve from Apes but had a
common ancestor with them 5 to 8 million years ago.
• This organism was neither human nor ape.
• In its attempt to survive, this common ancestor branch
out (adaptive radiation/divergent evolution.
• It ended up in different places where one group evolved
into a human and another an ape
• Descent with modification: organisms are modified
and vary from their decedents.
Common ancestry
Make a list of adaptations that make these
animals successful in their environments.
Snow leopard
cheetah
• Adaptations of the Snow Leopard
• STRONG LEGS: jump long distances.
• BIG PADS ON FEET To help travel on the rocky surfaces and
not sink into the snow.
• GREY, WHITE, SPOTTED FUR Camouflage to sneak up on
prey.
• DOUBLE-LAYERED COAT Insulated warmth from the cold
climate.
• LONG TAIL: balanced on top of the mountains.
• COMPACT BODY To keep insulated from the cold.
• BIG LUNGS To breathe in the high altitudes of the Himilayas.