Chapter 4.1
 How
does sexual reproduction and
change in the genetic information result
in variation within populations?
 How can we measure variations in a
population?
 Describe how mutations may improve an
individual organisms chance for survival
and reproduction?
 What is “Natural Selection”?
 An
adaptation is a structure, behavior or
physiological process
 These
help an organism to survive and
reproduce in particular environment
 Example: camouflage
 Can
you find the “hidden organisms” in
the following slide?
 Complete
Launch Lab – page 113
“Could Cockroaches Rule the Earth?”
*Complete the analysis questions 1-4

Biochemical and Body
Processes
 Hibernation in ground
squirrel

Structural Adaptation
 Sharp talons and excellent
vision of owl
 Thick leaves of buffalo
berry that help to reduce
the water loss on hot
summer days
 They
are a result of a gradual change of
characteristics over time
A
variation that helps an individual in a
population is likely to be passed on from
survivor to survivor
 Some
variations help and some do not,
not all variations become adaptations!
 Question:
Are there measureable
differences in sizes among individuals of
a species?
 As a class, each measure your thumb and
your middle finger
 Take the class data and graph this
information
 Use a data table and a graph that best
suits the data gathered
 Conclude what you see with this data
A
group of reproductively compatible
populations
How
does variation
within a species
occur?
 Organisms
that reproduce sexually have
a blueprint from both parents
 Through this reproduction, particular
traits are passed on to the new organisms
 Mutations
are genetic changes that
happen in DNA
 Occur from mistakes that happen when
DNA is being copied
 For
example: Your DNA has about 175
mutations compared to your parents.
 Sometimes you notice mutation, other
times it has no effect
Evolution observed at the molecular scale
 Down
Syndrome: a genetic disorder
caused by the presence of all or part of
an extra 21st chromosome
 Often Down syndrome is associated with
some impairment of cognitive ability and
physical growth as well as facial
appearance
 Klinefelter's
syndrome: Affected males
have an extra X sex chromosome. The
principal effect is abnormal testes
development and reduced fertility.
 Sickle
Cell Anemia: A genetic disorder
passed on when BOTH parents have the
trait or are carriers for the trait
 The blood no longer flows easily through
the body. Many times the blood starts to
clot in the veins and arteries – not
allowing regular blood flow to the organs
in the body!

Sometimes a mutation allows for a trait that has benefits
especially in a changing environment – it will select
which organisms will survive

A population will change in its ability to survive as the
abiotic conditions around it will select those suitable to
survive in the environment

Mutations may provide a new selective advantage


A Housefly with resistance to DDT
A California ground squirrel that has a factor in their blood that
helps them combat rattlesnake venom when bitten
Depends on reproductive success
Operates on a population, NOT on an
individual
Dynamic between genetic change and the
changing environment
Environment exerts Selective Pressure:
environmental conditions that select for
certain individuals and select against others
Natural Selection can take time or can
happen quickly
eg: Bacteria vs. Finches
 Complete
the Thought Lab 4.1 – omit
procedure
 Complete
the Though Lab 4.2
 Complete
Section 4.1 Review Q’s 1-9