Download Evolution - bellevuebiology

• ATB: OPEN LOGBOOK TO DOTS
ACTIVITY
• DO THE 8 QUESTIONS YOU
ATTACHED AT THE END OF THE
PERIOD YESTERDAY
• PLANNER: HW-CHECKUP PRACTICE
DUE FRIDAY
• LOGBOOK CHECK AND CHECKUP ON
FRIDAY
• LEAVE THE BACK TWO (SMALL)
TABLES EMPTY, PLEASE
Questions to answer in your lab book
1. Which, if any, shades of paper squares
survived better than others in the second,
third, and fourth generation starting
populations of paper squares?
0% color survived the best.
2. What might be the reason that predators
did not select these shades as much as they
did other shades?
They blended into the environment
and were more difficult to find.
3. What effect did capturing a particular
shade square have on the numbers of that
shade in the following generations?
The shaded squares that were captured were
decreased in number in the next
generation.
4. What is the average color in generation 1?
What is the average color in generation 5?
Generation 1 = 50% shade
Generation 5 = 13 % shade
5. Did any 50% shade squares turn into
0% squares? Any 100% squares turn No
into 50%?
6. If none of the squares changed into
other squares, then why is the average
member of the dot/square population
different after 5 generations?
The 100% shaded squares were “eaten”
and could not pass on traits to the next
generation. 0% squares continued to
survive and pass on traits to next
generation.
7. How has the amount of variation in the
population changed over time?
The amount of variation has decreased in
the population over time. Most of the
population has 0% shade.
8.What affect do you think the environment
(habitat and predator) has on the average
characteristic and the variation of a
population?
The environment determines which
characteristics are favorable.
• MAKE A NEW ENTRY
TITLED “EVOLUTION
AND NATURAL
SELECTION”
• GET A NOTES SHEET
FROM THE FRONT
COUNTER
THE HORSE ON THE LEFT IS AN ANCESTOR OF THE
HORSE ON THE RIGHT. BASED ON WHAT WE’VE
LEARNED IN THIS UNIT ABOUT VARIATION AND
CHANGES DUE TO THE ENVIRONMENT—HOW
COULD THE AVERAGE HORSE WIND UP LOOKING
LIKE THE ONE ON THE RIGHT (AFTER A LOOOOONG
TIME). USE LEG LENGTH AS YOUR EXAMPLE
• DOTS-- GENETIC OR GET USED TO
THE WHITE BOARD?
• ANTIBIOTIC RESISTANCE—GENETIC
OR “GET USED TO”?
• LACTOSE INTOLERANCE– GENETIC
OR “GET USED TO” MILK
• IF AN ORGANISM DOESN’T HAVE THE
TRAIT—CAN THEY DEVELOP IT?
EVOLUTION
YOUR OWN DEFINITION AND
AN EXAMPLE
Evolution:
Change in the heritable (genetic)
traits of a population over time
Note: when we discuss evolution, we are talking about
populations changing, not individuals
Natural selection:
The main mechanism by
which evolution occurs
4 Conditions for Natural Selection:
1. Variation: Individuals in a population
are not identical to each other.
2. Inheritance: Traits are passed to
offspring; traits have a genetic basis
3. Environmental population limits:
Environmental limiting factors prevent
all individuals from surviving to
reproduce; some die young.
4. Environmental selection:
• Individuals in the population with more
favorable (advantageous) traits are the
ones that survive to reproduce.
• Individuals without advantageous traits
die before reproducing.
These factors result in a change in the
average trait of the population…
Biologists call this EVOLUTION!
1. VARIATION
Members of a population have traits similar to
the average trait of the entire population, but
they are not identical.
YOUR TURN:
Using height as
an example,
sketch a graph to
represent the
statement above.
Mean (average) height
Frequency
•
Height (cm)
2. INHERITANCE
• DNA determines the traits of individuals
DNA
mRNA
protein
trait
• Individuals inherit DNA from their parents
• This causes the traits of the offspring to
resemble the traits of the parents
3. ENVIRONMENTAL
POPULATION LIMITS
Population
A. For all species, if every individual born into a
population were to reproduce, the population
would grow exponentially
Time
3. ENVIRONMENTAL
POPULATION LIMITS
Population
B. Environmental factors (limiting factors) prevent
the majority of individuals from surviving to
reproduce
Time
4. SELECTION
•
Individuals without advantageous traits
die before reproducing.
Individuals with advantageous traits
survive to reproduce.
Frequency
•
These individuals
survive to reproduce
Characteristic
Populations change, not individuals
Frequency
• The “average” characteristic or other measure of
the population changes over generations
These individuals
survive to reproduce
Characteristic
The environment is the selective
force behind evolution
• The environment determines what
characteristics are “favorable”
• Because the environment changes over
time, the characteristic that is more
favorable for a population changes
• Therefore, characteristics of the population
change, or evolution occurs
Questions for discussion
•Describe how variation existed in the
PAPER SQUARES .
•Describe how inheritance existed in the
PAPER SQUARES.
•Describe how population limits existed in
the PAPER SQUARES.
•Describe how environmental selection
affected the PAPER SQUARES.
•PEPPERED MOTHS
Evolution of Peppered Moths
Dark form
Peppered form
Explain the evolution of color in the
peppered moth population.
1. Describe what trait evolved.
2.Describe how each of the 4 conditions
for natural selection exists in the moth
example:
a) Variation
b) Inheritance
c) Population limits
d) Selection (Environmental Selection)
Make a graph that shows how the average
color changed over several generations
• The population of peppered moths became
darker in color near industrial areas.
• Originally, some moths were dark, some moths
were peppered (light).
• Color is determined by genes inherited from
parents.
• Not all moths survive to reproduce- some are
eaten by birds.
• Pollution killed lichen and made the environment
darker, so darker moths were better
camouflaged and not eaten as much as
peppered (light) moths.
• This caused the average color of the moth
population to become darker
• Apply the 4 factors of Natural Selection to the
Giraffe Population
• Variation
• Inheritance
• Population Limits
• Environmental Selection
• Make a graph that shows there is a variety of
neck lengths, but most are like the average
• Make a graph that would show how the average
neck length has changed over time (to be
longer)
•Checkup practice
• A POPULATION OF BIRDS HAD BEAKS WITH
LENGTHS RANGING FROM 5CM TO 15CM. THESE
BIRDS ATE MOSTLY FRUIT AND A FEW SEEDS—
ONLY LONG-BEAKED BIRDS CAN EAT SEEDS.
AFTER 3 YEARS OF DROUGHT, THE AVERAGE
LENGTH OF BEAK INCREASED.
• APPLY THE 4 FACTORS OF NATURAL
SELECTION TO THE BIRDS
• A GRAPH THAT SHOWS THE BIRDS’ BEAKS ARE
SIMILAR BUT NOT IDENTICAL TO ONE ANOTHER
• A GRAPH THAT SHOWS HOW THE AVERAGE
BEAK LENGTH INCREASED OVER A FEW YEARS
Starting Population
Generation
number
1
Surviving Population
15cm
10cm
5cm
15cm
5cm
10cm
6
8
7
3
6
7
2
6
12
14
4
9
13
3
8
18
26
4
15
24
4
8
30
48
• APPLY THE 4 FACTORS OF NATURAL
SELECTION
• GRAPH THAT SHOWS HOW THE
AVERAGE COULD CHANGE OVER TIME
• CALCULATE THE AVERAGE TRAIT OVER
GENERATIONS (DATA TABLE WILL BE
PROVIDED—BRING YOUR OWN
CALCULATOR)
• EXPLAIN WHAT WOULD HAPPEN IF ONE
OF THE 4 FACTORS WERE NOT
PRESENT