Section 15-3
* When Is a Flipper a Wing?
* All living things are related. Some relationships are easy
to see—
your pet cat may not roar like a lion, but it clearly
resembles one.
Other relationships are less obvious.
*
*
1. On a sheet of paper, construct a table that has five columns
and six rows. In the columns, write the following heads:
Animal Group, Example, Legs, Fins, and Tail. Then, place the
following animal groups in their own row: Mammal, Bird, Fish,
Amphibian, Reptile, and Insect.
*
2. Give one example for each group, and then fill in the
information for that example. For Legs, write in the number of
legs that each animal has. Do animals with fins have legs? Do
animals with wings have legs? If so, how many?
*
3. Can you tell from your table if a fish is more closely
related to a bird or to an amphibian? Explain your answer.
*
*
*
* After Darwin’s journeys he wrote and published
a book called On the Origin of Species
* In this book he proposed his thoughts on how
evolution happened called natural selection
*
*Influences on Darwin
*Thomas Malthus—(Essay on the Principle of Population, 1798)
* plants and animals produce more offspring than can survive.
* human overpopulation would lead to decreasing living standards if left
unchecked.
*Charles Lyell (1797-1875)
* Assumed natural forces in past same as today (erosion, sedimentation, etc.)
* Uniformitarianism (idea originally proposed by James Hutton but popularized by
Lyell)
"In October 1838, that is, fifteen months after I had begun my systematic inquiry, I happened to read for amusement Malthus on
Population, and being well prepared to appreciate the struggle for existence which everywhere goes on from long- continued
observation of the habits of animals and plants, it at once struck me that under these circumstances favourable variations would
tend to be preserved, and unfavourable ones to be destroyed. The results of this would be the formation of a new species. Here,
then I had at last got a theory by which to work".Charles Darwin, from his autobiography. (1876)
"I am well aware that this doctrine of natural selection . . . is open to the same objections which were at first urged against Sir
Charles Lyell’s noble views on ‘the modern changes of the earth, as illustrative of geology;’ but we now very seldom hear the
action, for instance, of the coast waves, called a trifling and insignificant cause, when applied to the excavation of gigantic
valleys or the formation of the longest lines of inland cliffs. Natural selection can act only by the preservation and accumulation
of infinitesimally small inherited modifications, each profitable to the preserved being; and as modern geology has almost
banished such views as the excavation of a great valley by a single diluvial wave, so will natural selection, if it be a true
principle, banish the belief of the continued creation of new organic beings, or of any great and sudden modification in their
*
* Darwin proposed that as populations grew that
there would be a struggle for existence
* A key factor in the above would be survival of
the fittest
* Successful adaptions enable organisms to be
better suited for environment
* Those adaptations are then passed on to next
generations
* Those that are adapted best for their
environment will have more offspring and those
that are not will either die or have few offspring
* http://www.youtube.com/watch?v=nS1tEnfkk6M
* http://www.youtube.com/watch?v=GPbWJPsBPd
A&feature=fvsr
*
Natural selection
*
*
*
Some members of a species have characteristics that
enable them to survive, produce more offspring than
others, and pass these characteristics on.
*
Fitness—the relative ability of an organism to survive and
transmit its genes to the next generation.
Adaptation—a characteristic that increases the chances
an organism will survive and reproduce in its
environment.
*
*
(Species—a group of similar organisms capable of reproducing with one another).
3 Types:
1.
2.
3.
Morphological/Structural
Behavioral
Biochemical
Note: It is species that evolve, not individuals.
*
Gene pool—the entire collection of genes among a population of organisms.
*
Population genetics—the study of gene pools and their changes.
*
* Observations
* Populations tend to be
constant
* Naturally occurring
variations—small
differences between
members of a species
* Inferences
* If more offspring are born, yet
population is constant, then
there is competition for food,
water, light, etc.
* Some variations are helpful
and others aren’t. Natural
selection eliminates those that
aren’t.
* Good variations are
adaptations
• If variations are selected, then organisms may
change—given enough time this may result in a
new species.
*
*Recombination of genes during mating.
*Genotype—the genetic makeup of an individual.
*Phenotype—the visible characteristics of an
organism
*“Crossing-over”
*Mutation
What is crossing over?
Bivalent
Centromere
Chiasma (site of
crossing-over)
*
*
* Darwin proposed that over long periods of time
organisms developed different structures to
adapt to different environments
* As a result species today look different from
their ancestors
* Common Descent
* All species-living and extinct-were derived from
same ancestors
Archaeopteryx
*
*
*
Section 15-3
Beaver
Beaver
NORTH
AMERICA
Muskrat
Muskrat
Beaver and
Muskrat
Coypu
Capybara
Capybara
SOUTH AMERICA
Coypu
Coypu and
Capybara
*
*Intermediate fossil forms
*Archaeopteryx indicates that birds probably evolved from
reptiles.
*Changing populations
*Artificial selection (domestication)
*Antibiotic resistant bacteria
*Anol Lizards in the Bahamas, Etc.
*Homologous structures—2 organisms w/parts that have similar
organization that is functionally unnecessary (meaning the similarity is unnecessary
but the trait in question may be, and usually is, functional).
* Indicates a common ancestor
* May or may not have similar function today
* Whale fin & our forelimb
• The forelimbs of vertebrates are
homologous structures.
*
* Analogous structures (for contrast with homologous structures—
analogous structures are not evidence for common descent)—2
organisms w/parts that have similar function, but different internal
structure.
* Did not come from a recent common ancestor
* Whale vs. shark fin
* Insect vs. bird wing
* Vestigial structures—parts that are no longer useful.
* Appendix—human
* Snakes with nerves to their “legs”
* Birds have genes that code for a reptilian mouth and tail.
*
* Overpopulation—Tendency to have more offspring than
can survive
* Variations—within a species there are variations—hair,
color, height, etc.
* Inheritance of variations
* Not all survive. Struggle for existence. Competition for
resources.
* Survival of the fittest, the best adapted.
*
Section 15-3
Turtle
Alligato
r
Typical primitive fish
Bird
Mammals
*
*
*
Evidence of
Evolution
includes
The fossil
record
Geographic
distribution of
living species
Homologous
body structures
Similarities
in early
development
which is composed of
which indicates
which implies
which implies
Physical remains
of organisms
Common
ancestral
species
Similar genes
Similar genes