Transcript Natural Selection and the Evidence for Evolution

Natural Selection and the
Evidence for Evolution
Evolution is…
the changing of species over generations.
* Once an organism’s DNA is set after
fertilization it will not change. Individual cells
may experience mutations, but they will likely
die off (unless the mutation is a cancer).
However, mutations to an organism’s sperm or
egg could create a change in the offspring.
Fossil evidence formed the basis of early evolutionary concepts
Charles Darwin 1809-1882
The voyage of the HMS Beagle
Thomas Malthus
All populations will grow faster
than the food supply.
What does that mean for those
organisms that are part of that
population?
How did Darwin apply these ideas to
Evolution?
Many species produce large amounts of
offspring (more than the habitat can support).
This leads to competition for food, living
space, mates and shelter.
What is artificial selection?
Breeding organisms with specific and desired
traits to produce offspring with those same
traits.
Dogs are a great example
As different as they look, they still
belong to the same species.
What is natural selection?
A mechanism for change in populations. This
occurs when an organism with favorable traits
survives, reproduces and thus passes on those
favorable traits.
We say that they were “selected” by nature for
survival.
Those without favorable traits were selected for
extinction.
To this very day, this
book generates
strong feelings on
both sides of the
issue of evolution.
This book was
banned by many
religious
organizations.
One of the problems with acceptance of
Darwin’s theory is that evolutionary
processes are difficult to observe directly.
Change only happens from one
generation to the next and those changes
are likely not even observable.
With that in mind, what would evolve
faster? An elephant or a bacterium?
Our understanding of genetics means
that the definition of evolution should
also include that it is a change in the
gene pool of a population over time
• Traits that hindered an organism’s survivability
die with them.
• Traits that helped an organism to survive and
reproduce will be passed on and therefore
become more common.
• This is called allelic frequency.
View Peppered Moth Video
• http://www.youtube.com/watch?v=LyRA807dj
Lc
As the trees darkened due to the
Industrial Revolution, nature
“selected” the black moth for
survival (in this case it was man that
changed the conditions, but the idea
is the same).
At this point we would say that the
“allelic frequency” of the color of the
moths has changed.
An adaptation is…
A trait that helps an organism to either survive
or get mates.
The goal of all organisms is to get their genes
into the next generation and to block their
competitors from doing so.
Think of two examples of traits that an animal or
plant has that helps it to either feed itself or
spread their genes by getting mates. Write
those in.
According to Darwin’s
theory, adaptations in
species develop over
many generations.
What is mimicry?
An adaptation that makes a species
look like a more formidable or
dangerous one
Examples of mimicry in nature
Monarch
butterflies taste
horrible to birds,
but the Viceroy
butterfly does
not. Birds
cannot tell the
difference so
they don’t eat
either.
Plants will mimic, too.
Not poisonous
What is camouflage?
An adaptation that enables an organism to
blend in with their surroundings (it can be
used for hunting or hiding).
Physiological Adaptations
• Changes that help an organism to survive,
such as disease resistance.
• Different from structural adaptations because
they are invisible (chemical traits, such as
blood type).
Fossils allow us to relatively date.
They also provide a record of past life and show
changes over time.
How sedimentary rock layers are
formed;
• https://www.youtube.com/results?search_qu
ery=how%20sedimentary%20rock%20layers%
20are%20formed&sm=3
How are fossils formed:
• https://www.youtube.com/watch?v=SEDfRy6
DQns
Evolutionary biologists believe that
structural similarities are evidence
that…
Some organisms share a common ancestor.
What is that? What common ancestor do you
and your cousins have in common?
Homologous Structures – Use the pictures
below to help formulate an answer.
Analogous structures – Use the pictures below
to help you formulate an answer.
Are the wings of a butterfly and the
wings of a bird homologous or
analogous?
Explain your answer.
Vestigial Structures
Go to the following website to help you explain
vestigial structures and give an example of a
vestigial structure in humans.
http://3.bp.blogspot.com/-ChvT1VSn0k/UsFesKo2_I/AAAAAAAAAxA/FqFhVQP5HZw/s1600/Vitruvi
an+Man+-+Human+Vestigial+Structures.jpg
For #25 you have enough info to figure
it out on your own.
4 sources to determine evolutionary
relationships. The following slides give you
hints.