Mutation and Natural Selection
Weekly Goal!
 Catalyst:

When
Write in complete sentences!
Don’t talk during the Catalyst!
you hear the word mutation, what
do you think of? Write at least THREE
complete sentences.
What characteristics do you think a
student needs to “survive” high school?
Objectives
By the end of today, all SWBAT…
 Define “mutation”
 Identify environmental pressures
 Describe how natural selection
determines whether organisms live
or die
Agenda







Catalyst Review
What Is a Mutation?
Environmental Pressure and Natural Selection Notes
Online Demo
Quick Guided Practice
Lab
Exit Questions
HOMEWORK: Mutation and Natural Selection worksheet, Finish
lab questions
What is a mutation?


Key Point #1: A mutation is a change in
DNA sequence
Mutations can increase fitness, decrease fitness, or
not matter
 Fitness

= ability to survive and produce offspring
Mutations are caused by…
 Mistake
during transcription or meiosis
 Radiation
 Chemicals
 Gene therapy
LK!
a change here…
means a change here
and here
and finally here
DNA
RNA
Protein
(Trait)
Mutations Cause Variation

Mutations cause variation
Variation
= changes or
differences
Environmental Pressure
Key Point #2: Environmental pressures
cause some organisms to survive better than
others.
 Examples:

 In
grassland,
lions
mustlive
compete
the tundra,
polar
bears
in the against
snow. If each
they
otherbetoseen
catcheasily,
gazelle
(their
can
their
preyfood).
will run away and
they
willis starve.
 What
the environmental pressure?
 What
kind
lions would survive
best?
is
theofenvironmental
pressure?
 What kind of polar bears would survive best?
Natural Selection

Key Point #3: Natural selection is survival of
the fittest.
 Mutations
that increase fitness become more
common.
 Organisms
that fit well in their environment live longer,
and produce more offspring. They pass on their genes!
 Mutations
that decrease fitness become less
common.
 Organisms
that do not fit well in their environment die
sooner, and produce fewer offspring.
So… uhhh… what about humans?
Sickle Cell Anemia


Those with recent African ancestry
have the highest rate of affection.
What is the variation?



What causes this variation?
What is the environmental
pressure?
How can this increase fitness?
Environmental Pressure Demo

AWESOME NATURAL SELECTION DEMO
Guided Practice 1

Long ago, some four-legged organisms lived in the
desert. Some had more eyelashes than others. Their
eyelashes helped to keep sand out of their eyes, so
they could find food more easily.
 What
caused some organisms to have more eyelashes?
 What is the environmental pressure?
 What happened to the organisms with many eyelashes?
 Why?
 What
(“…because…”)
happened to the organisms with few eyelashes?
 Why?
(“…because…”)
Guided Practice 2

Thousands of years ago, primitive four-legged
reptiles lived in the Louisiana swamps. They ate
wildebeest, but there weren’t enough wildebeest
around for everyone. Some reptiles had stronger
jaw muscles than others.
 What
caused reptiles to have different strength jaws?
 What is the environmental pressure?
 What happened to the reptiles with stronger jaws?
 EXPLAIN!
 What
(“…because…”)
happened to the reptiles with weaker jaws?
 EXPLAIN!
(“…because…”)
Guided Practice 3

Deer are hunted by coyotes. In a population of
deer, some are faster than others.
 What
caused variation in how fast the deer run?
 What is the environmental pressure?
 What happened to the faster deer?
 EXPLAIN!
 What
(“…because…”)
happened to the slower deer?
 EXPLAIN!
(“…because…”)
Lab: Skittle Survivor

You have six minutes to…
Fill
in your hypothesis and DV
Read the procedure
Change
on #6 – Predator will collect
SEVEN skittles.
Fill
in your IV
Answer the pre-lab questions
Key Point Wrap-Up
Key Point #1: A mutation is a change in
DNA sequence
 Key Point #2: Environmental pressures
cause some organisms to survive better than
others.
 Key Point #3: Natural selection is survival of
the fittest.

Exit Questions
In the tropical jungle,
some monkeys have
longer arms than others.
The longer-armed
monkeys are more
successful at climbing
trees for food than the
shorter-armed monkeys.
Write in complete sentences!
Don’t talk during the Exit Question!




What caused the variation in
monkeys’ arm length?
What is the environmental
pressure?
Explain what will happen to
the shorted-armed monkeys.
Explain what will happen to
the longer-armed monkeys.