PKA: Answer on your own paper and
turn in to Ms. Deel
• 1. Do populations of organisms change over
time? How do you know?
• 2. Why would organisms need to change?
• 3. Is there evidence that any organisms living
today have experienced any change?
• 4. What factors would contribute to any
change?
What did this organism look like when
it was alive?
http://www.sciencemag.org/site/multimedia/slideshows/343.6169.dino/dino.slideshow.ht
ml
Horse Evolution Lab
www.docstoc.com
www.itsokaytobesmart.com
What changes occurred and why?
www.fillthevoid.org
http://www.sepa.duq.edu/darwin/education-tools-hor
Fossils
• Fossils: Any trace or remains of an organism
that has been preserved by a natural process
• Comparing structure of fossils with present
day organisms allows us to infer evolutionary
relationships
www.mindbodyspiritonline.co.uk
• Evolution: Change over time
– Geological Evolution: the evolution of the Earth
itself
– Organic Evolution: the evolution of living things
• Most of the time organisms decay without
leaving a trace causing the fossil record to be
incomplete
• Why would organisms that die not be
fossilized?
– Not in sedimentary rock
– Decay quickly
– Get eaten
– Ex- tropical rain forest organisms decay too fast
• Fossils are found in Sedimentary rock
www.en.uni-muenchen.de
Sedimentary rocks are formed by sediment that is deposited over time,
usually as layers at the bottom of lakes and oceans.
Types of Fossils
• 1. Amber and Ice
• 2. Bones and Petrification
• 3. Molds, Casts, and Imprints
Age of fossils
• 1. Relative dating
– Age determined by relating fossil to others
• Use index fossils- fossils found only during on
period of time
• Law of Superposition: Layers on the top were
deposited later than layers on the bottom;
layers on the bottom are older than on the top
Law of Superposition
tle.westone.wa.gov.au
Which layer is the youngest? Oldest?
ufo-connguoithuongde.blogspot.com
http://quizlet.com/4079105/relativeabsolute-agedatingfossils-flash-cards/
• 2. Absolute Dating
– Radioactive dating gives more precise time
• Radioactive Dating: use rate of decay of
radioactive elements found in organisms to
find their absolute age.
– Ex: carbon dating
• The universe is full of naturally occurring
radioactive elements. Radioactive atoms are
unstable
• Over time, radioactive “parent atoms” decay
into stable “daughter atoms.”
• Half life: how many years it takes for half of
the amount of an element to decay.
Radioactive Decay Example
• Carbon-14 has a half life of 5,730 years. If the
original amount of C-14 in a dead horse is 14g,
how old is the organism if the amount of C-14
is currently 7g? If 3.5g is left?
• 5,730 years
• 11,460 years
• Evolution is the change in the inherited
characteristics of populations over successive
generations
• Darwin vs. Lamarck
ciencialibrecolombia.wordpress.com
Lamarck
• 1. Tendency towards perfection- all organisms
have the urge to become better.
• 2. Use and Disuse- organisms can alter their
traits by use or disuse
• 3. Acquired characteristics- the traits that an
organism acquires during a lifetime will be
passed on to offspring
Darwin
• 1. Overproduction- Each species produces
more offspring than can survive to adulthood
• 2. Competition/Struggle- Because of
overproduction, organisms must compete for
resources like water, shelter, food, escape
predators
• 3. Genetic Variation- variations or differences
occur among members of the same species
Darwin
• 4. Survival of the fittest/ Natural SelectionOrganisms with traits that make them well
adapted to their environment have a better
chance of surviving to adulthood to reproduce
and therefore passing on their well adapted
genes to the next generation
• 5. As natural selection continues over
generations, species change and become better
adapted to their environment= EVOLUTION
Whose theory was correct?
Example: Giraffes
• Using the theories to explain why giraffes have
such long necks
Example: Giraffes
• Lamarck:
1. Giraffes want longer necks
2. They stretched their necks a lot to reach leaves
high on trees
3. They passed the long neck trait they acquired on
to their offspring
Example: Giraffes
• Darwin:
1. Over production- too many giraffes
2. Struggle- not enough food, leaves high on trees
3. Variation- Giraffes with short, medium, and long
necks
Example: Giraffes
– Darwin Continued:
4. Natural Selection- the giraffes with the long necks
could reach the higher leaves and survive to
reproduce more than others
5. After generations the giraffes with short and
medium necks died out and long necked giraffes
increased in the population.
Example: Darwin’s Finches
• Using the theories to explain who finches
where there are large, hard seeds to eat have
evolved large thick beaks.
Example: Darwin’s Finches
• Lamark:
1. Finches want bigger beaks.
2. Finches use their beaks a lot and they got thick
3. They passed the thick beak trait they acquired on
to their offspring
Example: Darwin’s Finches
• Darwin:
1. Over production- too many finches
2. Competition- not enough food, only large seeds
3. Variation- Finches with small, medium, and large
beaks
Example: Darwin’s Finches
– Darwin Continued:
4. Natural Selection- the finches with the large thick
beaks could open seeds and survive to reproduce
more than others
5. After generations the finches with short and
medium beaks died out and large beaked finches
increased in the population.
Evidence of Evolution, Evolution of
Populations
• Evolution- a change in a population over time
• Gene pool- all genes in a population
• Population- groups of interbreeding
individuals that live in the same place at the
same time
How are these structures alike?
How are they different?
Evidence that organisms descended
from a common ancestor
• 1. Homologous body structures: Structures
that have different mature forms but develop
from the same embryonic tissue.
• Ex- The forelimbs of vertebrates
www.bio.miami.edu
• 2. Vestigial structures: Structures that no
longer function or function less than in an
ancestor, but are present because they are left
over from an ancestor.
• Ex- Tailbone in humans, appendix in humans,
wisdom teeth in humans, toe on a boa
• 3. Similarities in Embryology: The more
similarly the embryos of different organisms
develop the more closely related they are.
• 4. Darwin’s Finches: there are 13 species of
finches on the Galapagos that descended from
1 common ancestor from the mainland of
South America. Similar because inherited
similar DNA from common ancestor, different
because environmental pressures caused
natural selection.
• 5. Antibiotic Resistance in Bacteria:
• Back to Darwin’s idea’s
– Overpopulation- too many bacteria
– Struggle- antibiotics
– Variation- some bacteria have genetic resistance
to antibiotics, some do not
– Survival of the fittest- the bacteria that are
resistant survive and reproduce more
– Evolution-there is an increase in antibiotic
resistant bacteria
• 6. Pesticide resistance in Tobacco Budworm
– Over time the Tobacco Budworm has become
resistant to pesticides. Using Darwin’s Theory to
explain this phenomenon
– 1968-tobacco budworm infestation; farmers
sprayed pesticide and killed budworms
– 1969-small infestation; farmers sprayed; pesticide
didn’t help
– 1970- infestation; farmers sprayed; pesticide
didn’t work
• 7. Sickle Cell Anemia & Malaria:
• Sickle Cell Anemia is a deadly genetic disease;
causes blood cells to form a sickle shape; gene
common in tropical Africa and Asia
• Malaria- leading cause of death in Africa; a
pathogenic disease caused by a protist that is
transmitted by the bite of a certain mosquito
found in tropics
Why has natural selection not
eliminated the harmful gene?
• AA- does not have sickle cell, NOT resistant to
malaria
• Aa- does not have sickle cell, resistant to
malaria
• Aa- has sickle cell anemia, resistant to malaria
• Individuals heterozygous have a better chance
of surviving and reproducing
www.mhhe.com
Toothpick Fish Lab
Weedy Sea Dragon
www.ripleyaquariums.com
Natural Selection Depends on:
• Variation
• Struggle
• Survival of the “fittest”
• Remember natural selection is based on the
LAWS OF GENETICS
• Sources of Variation in a gene pool
• 1. Crossing over- exchange of genes from one
homologous chromosome to another
www.phschool.com
• 2. Sexual reproduction
• 3. Mutation- change in genetic material (only
source of NEW gene type)
• 4. Migration- the movement of organisms into
or out of a population
• 5. Isolation- a group of organisms becomes
separated from its original population
– Organisms can be separated by:
• Geography (by river, mountains) OR
• Reproduction (mate at different times, places, etc)
• The isolated population may have different
environmental pressure and therefore
different genes may be selected for.
• This may cause the isolated population to
become very different from the original
population.
• Isolation often leads to speciation.
• Speciation- the development of a new species
• Ex- Squirrels around the Grand Canyon; A
group become isolated on the other side and
become a different species because of
different environments
• How new species can emerge:
• Genetic variation → environmental change→
natural selection→ new species
Rate of Species Survival
• The two evolutionary "strategies" :
• r-selection for those species that produce
many "cheap" offspring and live in unstable
environments
• K-selection for those species that produce few
"expensive" offspring and live in stable
environments.
R-Selected Example
http://education-portal.com/academy/lesson/r-selected-species-examples-definitionquiz.html#lesson
K-Selected Example
www.acuteaday.com
• Of course, the animal or plant is not thinking:
"How do I change my characteristics?"
• Natural selection is the force for change
• But, natural selection has produced a
gradation of strategies, with extreme rselection at one end of the spectrum and
extreme K-selection at the other end.
r Unstable environment, density independent
K Stable environnent, density dependent
interactions
small size of organism
large size of organism
energy used to make each individual is low
energy used to make each individual is high
many offspring are produced
few offspring are produced
early maturity
late maturity, often after a prolonged period of
parental care
short life expectancy
long life expectancy
each individual reproduces only once
individuals can reproduce more than once in
their lifetime
type III survivorship pattern
in which most of the individuals die within a
short time
but a few live much longer
type I or II survivorship pattern
in which most individuals live to near the
maximum life span
Rate of Evolution
• Gradualism- process of evolution by slow
change (remember the evolution of horses)
• Punctuated Equilibrium- species remain
unchanged for millions of yeas suddenly die
off with a short time and new species take
over. Ex dinosaurs died off which allowed
mammals to take their place
• Adaptive Radiation- when a single species or
small group of species evolves into many
different forms.
• Ex- After the dinosaurs died out there were a
few species of mammals that then evolved
into many different forms of mammals. They
filled the places of the dinosaurs
Types of Evolution
• Divergent Evolution- different species develop
from a common ancestor.
– Ex- Grizzly bears and Polar bears have a common
bear ancestor, but different climates selected for
different climates selected for different variations
• Convergent Evolution- unrelated organisms
have similar traits due to similar environments
– Ex- sharks and dolphins are unrelated but live in
similar environments and eat the same things so
same color patterns and shape
Types of Natural Selection
• 1. Directional Selection- results in species
having one extreme of a trait.
– Ex- male cardinals, resistant bacteria
www.sparknotes.com
• 2. Disruptive Selective- results in species
having both extremes of a trait; can lead to
speciation
– Ex- frogs
www.sparknotes.com
• 3. Stabilizing Selection- results in species
having average of the same trait
– Ex human birth weight
www.sparknotes.com
en.wikipedia.org
• Using the familiar example of giraffe necks,
there was a selection pressure against short
necks, since individuals with short necks could
not reach as many leaves on which to feed. As
a result, the distribution of neck length shifted
to favor individuals with long necks.
• Directional Selection
• Imagine a plant of extremely variable height that
is pollinated by three different pollinators, one
that was attracted to short plants, another that
preferred plants of medium height and a third
that visited only the tallest plants. If the
pollinator that preferred plants of medium height
disappeared from an area, medium height plants
would be selected against and the population
would tend toward both short and tall, but not
medium height plants.
• Disruptive Selection
• A plant that is too short may not be able to
compete with other plants for sunlight. However,
extremely tall plants may be more susceptible to
wind damage. Combined, these two selection
pressures select to maintain plants of medium
height. The number of plants of medium height
will increase while the numbers of short and tall
plants will decrease.
• Stabilizing Selection