Transcript The Theory of Evolution

Evolution
AP Biology
Chapter 17
What is Evolution?
 Defined
as the accumulation of
inherited changes within populations
over time.
– group of individuals of one
species that live in the same area
i.e. all organisms have descended from
common ancestors with modifications,
over long periods of time
Population
Some questions that can be
answered by evolution.

Why are there bones and fossil evidence of
creatures that no longer exist? What
happened to them?

Why do so many different animals have the
same structures?
 Ex.
The arm bones in a human are the same
bones as a flipper in a whale.

Why do organisms have structures
they no longer use?
 Ex. The appendix in humans,
non-functioning wings in
penguins, pelvic bones in whales
Why do so many organisms’ morphology
and anatomy follow the same plan?
 Why is the sequence of DNA very similar
in some groups of organisms but not in
others?
 Why do the embryos of animals look very
similar at an early age?


Why do males often develop elaborate
traits/characteristics despite the possible
effect on their survival?

Evolution is considered a Unifying concept
of Biology, because it answers many of
these questions and offers an explanation
for the data.
Lamarke’s Theory of Acquired
Characteristics

Hypothesized that an organism gains or
loses features if they were not used.
 Use/Disuse
 Tendency
toward perfection
Then, these traits would be passed on to
your offspring.
 Inheritance of Acquired Characteristics

 Ex.
A giraffe stretched its neck to reach higher
leaves, stretched neck would be inherited by
offspring.
Darwin’s Theory of Evolution by
Natural Selection


Charles Darwin –
naturalist
He observed many
species on trips to
places like Galapagos
Islands
 Particularly
interested in
the finches

Wrote “On the Origin of
Species”
Animals in the Galapagos Islands
Darwin’s Theory of Natural
Selection
1.
2.
3.
4.
Variation exists among individuals in a species.
Individuals of species will compete for
resources (food and space).
Some competition would lead to the death of
some individuals while others would survive.
Individuals that had advantageous variations
are more likely to survive and reproduce.
Darwin’s Theory of Natural
Selection
This process = Natural Selection
 Favorable variations = Adaptations
 Example of the Finches:

 Looked
the same except for the beak size and
shape.
 Concluded that all the finches were descendents
of the same original population.
 Shape of the beaks were adaptations for eating
a particular type of food.
Artificial Selection

Choosing certain traits and breeding only
individuals that display the desired traits
 Breeds
of dogs
 Plant varieties


Ex. Cabbage, broccoli, cauliflower, Brussels sprouts,
kale, collard greens – all the same species
Occurs in just a few generations
•Different dog breeds are
examples of how
selection can change the
frequency of alleles in a
population.
Evidence of Evolution

Fossil Evidence
 If
today’s species came from ancient species, then
we should find remains of those species that no
longer exist.

There are tons of fossils of creatures that no longer exist
but bear striking resemblance to creatures that do exist
today.
 Carbon-dating:
gives an age of a sample based on
the amount of radioactive carbon
 Fossil Record – creates a geologic time scale
Evidence of Evolution
Evidence of Common Ancestry
 Homologous Structures – structures that are
embryologically similar, but have different
functions (p.378)

 Ex.

Wing of bird and forearm of human
Vestigial organs – functionless parts
 Ex.
Snakes have small pelvic and limb bones
 Ex. Humans have a tail bone
Biochemistry and DNA
 Observation of species change (wolves/dogs,
peppered moths)

Examples of Evolution
Industrial Melanism
 Dog Breeds (artificial selection)
 Bacteria and Antibiotics
 Elephant Tusks

Evolution – on a small scale

Bacterial Resistance
life cycle – very short!
 Bacteria continually evolving – even inside the bodies
of hosts.
 Bacteria develop genetic resistance through mutations
and from acquiring new genes from plasmids or
viruses.
 Surviving bacteria that resist antibiotics pass on their
genes to future generations.
 Poor prescribing practices and poor patient compliance
are factors that determine bacteria resistance.
 Bacteria
The Synthetic Theory of Evolution
Darwin knew that individuals transmitted
traits to the next generation.
 What Darwin didn’t know:

 How
or Why individuals vary within a
population.
During the 30’s and 40’s, biologists
combined the principles of genetics with
Darwin’s theory of Natural Selection
 The unified explanation of evolution is
known as the synthetic theory of evolution.

The Synthetic Theory of Evolution

Explains Darwin’s observation of variation
among offspring in terms of mutation.
 Mutation
provides the genetic variability on
which natural selection acts.

Universally accepted and constantly
studied by scientists.
Convergent Evolution

Independent evolution of similar structures
in distantly related organisms
 Ex.
Aardvarks, anteaters, and pangolins
 Resemble one another in lifestyle and
structural features
 Strong, sharp claws to open ant/termite
mounds and long, sticky tongues to catch
insects
 However, they evolved from 3 distantly
related orders of mammals.
aka: analogy
Phylogeny


The evolutionary history of a group of related species.
Phylogenetic trees can be constructed to show
relationships:

Diagrams showing lines of descent
Evolutionary hypotheses can be
tested experimentally

Guppy Experiment – Reznick and Endler
 Observed
that different streams have different
kinds and numbers of fishes that prey on guppies
 Differences in predation are correlated with many
differences in guppies:

Male coloration, behavior, age and size at sexual
maturity, number of offspring per litter, size of offspring,
and the frequency of reproduction
Sexual Selection

Natural selection that acts on an
organism’s ability to mate
 Selection
where organisms go to extreme
lengths to attract a mate.
 Sometimes results in features that are harmful
to the individuals survival.
http://www.pbs.org/wgbh/nova/evolution/creatur
e-courtship.html
Examples of Sexual Selection
Peacock image courtesy of Rock Maple Farm.
Elephant seals image courtesy of Craig’s Homepage.
Review Questions – Chapter 17

Questions p. 388-389
 Post
Test # 1-6, 8-15
 Review Questions # 1-4, 7
 YMTC # 5