Transcript Revised Evolution PPT

Evolution and Natural
Selection
Change over time
“The Earth is 4,000 years old”
According to some interpretations of the
Bible
If Earth was only 4,000 years
old…
How could there have been time for all
the extinct species, such as dinosaurs
to have lived?
“The Earth is very, very old”
-
Charles Lyell 1797-1875 – Lyell influenced
Charles Darwin’s Theory of Natural Selection
Radiocarbon dating puts the earth at 4.5
Billion years old
Humans have been here less than 1 million
years!
Thomas Malthus made a
contribution to Darwin’s
Theory
Malthus was an economist
He notice that humans produce more
offspring than can survive
A group will die every generation
What happens when the
population exceeds the
resources?
Jean Baptiste Lamarck
1744-1829
Proposed an idea of how organisms
change over time
“The Theory of Acquired Characteristics”
Lamark’s theory
Organisms can acquire new traits and
pass them on to their offspring
If you lift weights your muscles will be
bigger
Your children will have stronger arm
muscles
Lamarck suggested that
giraffes long necks are the
result of individual animals
stretching their necks over long periods
of time to reach the highest leaves
Charles Darwin
Born in 1809
Died in 1882
Published a book called “The Origin of
Species”
Suggested a way that species changed over
time
The Theory of Natural
Selection
1) Variation Exists in all populations
Variation comes from random mutation
2) Those individuals that are best suited
to their environment survive and pass
on their genes to their young
3) Over millions of years species
change
“Survival of the Fittest”
Is not accurate
Natural selection is the survival and
reproduction of the fittest traits
Adaptation: The changing of a
species that results in its
being better suited for its
environment
Rough Green snakes
Adapted camouflage helps
these snakes escape
predators
Some species change color in
the winter
Rabbits have a coat change in
the winter
Turtles adaptation
Turtles have
Exceptional night
Vision. Unlike us, turtles can see in color
at night
Eagles have extraordinary
vision
Vision is 4x as sharp as a human
They have an extra focal point in the back of
their eye
They can see even when they blink their eye
- eyelids are transparent
* can see a rabbit moving a mile away!*
Mollusks also have simple
eyes
Mollusks have many eye features that
are similar to vertebrates.
Lenses
Retina
* Their vision is not as good as ours
Flatworm has “eyes”
Not the kind of eye that can see a
picture
They can sense light and dark
Adaptations can be behavioral
Bears hibernate in the winter
Snakes and other reptiles sun
themselves on rocks to warm
up
Reproductive Adapations
Since Reproduction is necessary for
natural selection, species have adapted
incredible Reproductive adapations!
Likes and Dislikes of Charles
Darwin
Dislikes
Medicine, Blood, Surgery
Likes
Plants and animals esp. animals
Darwin got a job
On the H.M.S. Beagle
His unofficial title was as a
naturalist
The Galapagos Islands
Before Darwin left for his
voyage, People thought
species never changed
But what Darwin found
changed that thought
The Galapagos held a vast array of life
Many of the species Darwin found
closely resembled species Darwin had
seen on the mainland
Darwins drawings of finches
Why would God create so many
different finches?
13 islands 13 different finches
They had differences in the
size of their beaks
The food they ate
Some ate soft nuts
Some ate hard-shelled nuts
Some ate insects
Some ate berries
Darwin had a Hypothesis
Finches must have arrived at the
galapagos a long time ago, and
changed after they arrived!
“Descent with Modification”
Tortoises
11 different species of tortoises on the
13 Galapagos Islands
Different size and shell shape
Evidence of Evolution
1) Fossils – found in sedimentary rock,
these can be dated and show that many
species have changed over time
Evolution of Horse foreleg
bones found in fossils
2) Vestigial Structures
Organs or structures in present day
animals that are not used anymore
Appendix
Did you know whales have leg bones
and hips?
They are no longer attached
to the spine
This suggests that whales have an
ancestor that walked on land!
Evolution of the Whale
3) DNA and Proteins
We all share the same DNA code
Made with the same 4 nucleotides
The more closely related two species are, the
more similarities there are in their DNA code
Humans and chimps are 98% identical!!
All mammals have similar proteins
i.e. hemoglobin
DNA evidence
Most species of mammals are over
90% identical in terms of DNA code
Pseudo genes - multiple copies of DNA
sequences that no longer function
Hox genes
These are found within gene families
Not transcribed or translated
4) Comparative Anatomy
Similar Organisms have similar
structures – The forearm in Vertebrates
all have the same bone structure
5) Artificial Selection
Darwin used this to support his theory,
dog breeders select for specific traits in
a breed
If humans can change an animals traits,
why couldn’t this occur in nature?
Domestic Pigeons? – these
were very popular among
aristocratic English in the
1800’s!
6) Evolutionary history is seen
in the development of
Embryos
Each embryo develops a tail, buds that
become limbs and pouches which contain gill
- like brachial slits
Only fish and amphibians retain these and
have them develop as gills
Amphibians retain gills in their tadpole stages but
get rid of them when they become adults
7) Microevolution
Change in small groups has been
shown to occur
Antibiotic resistance is evolution in
action!!!
Population Genetics
Population – A group of genetically
similar organisms that live together and
interbreed
Species – A group of organisms that
can and do interbreed and produce
fertile offspring
Dogs Canis familiaris are all
the same species
Horses and Donkeys are not
Isolation
Two populations of the same species
cannot breed with each other
Gradualism
Change occurs very slowly over very
long periods of time
American scientists beg to
differ
Successful species remain unchanged for
very long times
They developed the idea of Punctuated
Equilibrium
Michigan State Experiment
Bacteria reproduce 15,000 times faster than
we do
Grew thousands of generations of bacteria
Showed that changes in e. coli occurred
quickly
Explains why our fossil histories often lack the
“intermediate type”
Species remains unchanged
until an environmental
stimulus changes
Peppered Moth
London England
Use of coal during the Industrial
Revolution
Moths had adapted to blend in
with the trees they lived on
Use of coal blackened the
trees and moths no longer
blended in with their
surrounding
By the end of the Industrial
Revolution, most peppered
moths were the darker version
So they adapted to blend in
with their surroundings…
Aren’t the smart?!
How did they do that?
A mutation occurs randomly,
causing the darker versioned
moth
Industrial melanism
The darker version survived better with
the blackened trees.
100 years later, trees are back
to normal
Which moth will survive better?
New species are formed
through Natural Selection
Speciation - appearance of a new
species
Most evolutionary change is too slow to
see
Examples of speciation
Changes in bacteria
1969 - a new species of salt bush
developed from hybrids of a different
salt bush and a salt sage
Salt bush occurs in south Utah
New species of fruit flies have
been created using radiation
treatment
Radiation increases the rate of mutation
and therefore increases variation
Why is variation important to evolution?
Speciation is directly linked
with the ability to reproduce
As soon as two population become so
genetically different that they cannot
produce fertile offspring, they are
technically different sepecies
i.e. Domestic Dog and Wolf
The intermediate of a Wolf-dog is
infertile
In some cases one population will
simply out-compete another and
extinction of a section will occur
Many times the two species
are geographically isolated
and they evolve separately
At one time the Alder flycatcher and the
willow fly catcher were considered the
same species
Ecological isolation
Occurs when two species adapt to
different habitats.
When the habitats are different and no
crossbreeding occurs,
Sometimes there is a
chemical incompatibility
between the two gametes
This sometimes occurs in plants
Sperm and egg may not be chemically
compatible
Behavioral Isolation
Sometimes occurs in animals
Ex. Leopard Frogs mate at different
times in the year and are in the process
of becoming different species
When frogs of one sex in the Northern
limit of the range are brought together
with frogs in the southern limit, they will
not mate
Founder effect
Occurs when one, or a very few
individuals from a population move to a
new area. The new population will be
genetically different from the first
because only the genes of the Founders
are available
Genetic Drift
Change in allele frequency in a
population
Bottleneck Effect
When a stress in the environment
occurs and only a few individuals
survive, the remaining individuals will
determine the genetic makeup of the
new population
Hardy Weinberg Equilibrium
We can calculate Allele frequency in a
population with the following formula
a= dominant allele freqency
b= recessive allele frequency
a+b=1
a2 + 2ab + b2 = 1
a2 = frequency of homozygous
Domanant individuals
b2 = frequency of homozygous
Recessive individuals
2ab = frequency of heterozygous
individuals
Hardy Weinberg Equilibrium
exits in a population when..
1) There is NO Genetic Drift occuring
2) There is no Gene Flow in a
population
Mating is completely RANDOM
There is NO Natural Selection
There is NO mutation
….. So never, but we still use
the formula to estimate allele
frequency in populations =)
Darwin said in his book,
“Origin of Species”,
Humans, gorillas and chimpanzees all
evolved from a common ancestor
NOTE: WE DID NOT EVOLVE FROM
APES!!!
Many fossils strongly confirm
this hypothesis
The first primates evolved 5060 million years ago
They had two features other
mammals lacked
1) Grasping hands and feet - young
could hold on to their mothers
2) Eyes facing forward - many other
mammals didn’t see strait out = Better
depth perception
Prosimian is an example of a
primate that resembles early
Primates
Prosimians survive with their
adaptations
They live in trees
They use their tails to help them
balance
Diurnal v.s Nocturnal
Diurnal - active during the day
Nocturnal - active at night
Cone cells developed for
daytime seeing
Cone Cells - allow us to see in color!
Opposable thumbs
Monkeys feed mainly on fruits and
leaves rather than insects and they
were the first to have opposable
thumbs.
Take away your thumb and
see how hard it is to pick up
and move objects!
Monkeys appeared in Africa
and Asia
Old world Monkeys
New World Monkeys are
monkeys in the Americas
Emergence of the apes
Apes shared a common ancestor with
monkeys
Split that occurred with chimps
and apes occurred relatively
recently
Our ancestors descended
along the same lines as the
great apes
These are some actual skulls
found.