Transcript I. Evolution

 HAPPY TUESDAY 
Bellwork: Write down only the bolded red portion and your
answer.
Two species of mice live in a field in the middle of East
Texas. One mouse species is WHITE with BLACK spotting.
The other is BROWN with WHITE spotting.
After a year, the population of white mice has dramatically
decreased, while the population of the brown mice has
slightly increased.
Why would this be happening?
Standard: (7E)Analyze and
evaluate relationship of natural
selection to adaptation.
Essential Question:
What is
Evolution?
I. Evolution: change over time.
A. Scientists involved in the Evolution theory
1. Hutton and Lyell: helped scientists realized 2
things
a. Earth is millions of years old
b. the processes that changed Earth in the past
are the same as the present.
At that time, most scientists believed that the Earth was only
a few thousand years old.
2. Jean-Baptiste Lamarck: one of the first scientists to
recognize that living things have changed over
time.
a. Lamarck proposed that by selective use or
disuse of organs, organisms acquired or lost
certain traits during their lifetime.
b. These traits could be passed to the offspring.
c. Over time, this process led to a change in a
species.
d. Lamarck’s theory proved incorrect because
he did not know that an organism’s behavior has
no effect on its heritable characteristics.
3. Malthus: contributed to
Darwin’s theory of
evolution by establishing
the idea that population
size is limited by
environmental resources.
4. Charles Darwin: contributed more to our understanding of
evolution than anyone else.
a. Darwin traveled, made observations and collected
evidence that led him to propose his revolutionary
process.
b. Darwin published the results of his work in a
book called On the Origin of Species.
Summary of Darwin’s Theory:
 Individual organisms differ and some of these variations are
heritable (passed on)
 Organisms produce more offspring than can survive and
many that do survive do not reproduce
 Because more organisms are produce than can survive, they
must compete for limited resources (food, shelter, etc)
 Each unique organism has different advantages (good) and
disadvantages (bad)
 Individuals best suited to their environment survive and
reproduce successfully
 These organisms that survive pass their heritable traits to
their offspring
Summary of Darwin’s Theory cont’d:
 Other individuals that are not suited for their
environment die or leave few offspring
 This process called natural selection causes species
to change over time
 Species alive today are descended with modification
from ancestral species (their ancestors)
 This process by which diverse species evolved from
a common ancestor unites all organisms on Earth
into a single tree of life
One of Darwin’s most
important insights was
that members of each
species vary from one
another in important
ways.
Today, we know that
heritable variation in
organisms is caused by
variations in their genes.
II. How Evolution Works
A. Artificial selection: selection by humans for
breeding of useful traits
1. The struggle for existence is
competition among
members of a species for
food, living space, and
the other necessities of life.
2. High birth rates and a
shortage of life’s basic
needs eventually forces
organisms into a
competition for resources.
B. Fitness: the ability of an organism to survive and
reproduce
1. Fitness is the result of adaptations.
2. Adaptation: any inherited characteristic that
increases an organism’s chance of survival.
a. Successful adaptations:
- enable organisms to become better suited to
their environment
- increase an individual’s ability to survive and
reproduce.
Humans have thousands of adaptations: large brain,
opposable thumbs, excellent sensory organs, light,
strong skeleton, etc.
C. Natural selection: the process by which individuals with
characteristics that are not well suited to their
environment either die or leave few offspring.
1. Also referred to as survival of the fittest.
2. It is not seen directly, but only observed as changes
in a population over a long time.
3. Zombieland: The Rules