block day- may 23, 2012
DESCRIPTION
Block Day- May 23, 2012. Homework : pGLO Corrections/Retakes by Friday Finish DOTS activity questions- due Friday. Warm up: the horse on the left is an ancestor of the horse on the right. How could the average horse wind up looking like the one on the right? Use leg length as your example. - PowerPoint PPT PresentationTRANSCRIPT
Block Day- May 23, 2012Homework:pGLO Corrections/Retakes by Friday
Finish DOTS activity questions- due Friday
Warm up: the horse on the left is an ancestor of the horse on the right. How could the average horse wind up looking like the one on the right?Use leg length as your example
EVOLUTION(We will make an entry for the
notes handout later )
GIVE YOUR OWN DEFINITION AND AN EXAMPLE
Definition of Evolution:
Change in the heritable (genetic) traits of a population over time
Note: when we discuss evolution, we are talking aboutpopulations 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.
Freq
uenc
y
Height (cm)
Mean (average) height
YOUR TURN: Using height as an example, sketch a graph to represent the statement above.
Your height?
2. INHERITANCE
• DNA determines the traits of individuals
• Individuals inherit DNA from their parents
• This causes the traits of the offspring to resemble the traits of the parents
DNA mRNA protein trait
3. ENVIRONMENTAL POPULATION LIMITS
A. For all species, if every individual born into a population were to reproduce, the population would grow exponentially
Time
Pop
ulat
ion
B. Environmental factors (limiting factors) prevent the majority of individuals from surviving to reproduce
3. ENVIRONMENTAL POPULATION LIMITS
Pop
ulat
ion
Time
4. SELECTION• Individuals without advantageous traits
die before reproducing.• Individuals with advantageous traits
survive to reproduce.
These
indiv
iduals
die w
ithou
t rep
roduc
ing
These individualssurvive to reproduceFr
eque
ncy
Characteristic
Populations change, not individuals
• The “average” characteristic or other measure of the population changes over generations
Freq
uenc
y
Characteristic
avera
ge, 1
st gen
.
These
indiv
iduals
die w
ithou
t rep
rodu
cing
avera
ge, 2
nd ge
n.
These
indiv
iduals
die w
ithou
t rep
roduc
ing
avera
ge, 3
rd ge
n.
avera
ge, 5
0th ge
n.
These individualssurvive to reproduce
Entry 54: Dots Activity• Get 1 data table and 1 handout
per person from front counter and begin reading directions for today’s activity
0%shade
50%shade
100%shade
Color Identification Key
Starting Population Surviving Population
Generation number
0%color
50%color
100%color
0%color
50%color
100%color
1 10 10 10
234
5
Starting Population Surviving Population
Generation number
0%color
50%color
100%color
0%color
50%color
100%color
1 10 10 10 9 5 72
3
4
5
Starting Population Surviving Population
Generation number
0%color
50%color
100%color
0%color
50%color
100%color
1 10 10 10 9 5 72 18 10 14
3
4
5
•Make a table heading (not an entry) “class data”
•Get a set of class data
Starting Population Surviving Population
Generation number
0%color
50%color
100%color
0%color
50%color
100%color
1 10 10 10 9 5 7
2 18 10 14 15 4 7
3 30 8 14 26 6 9
4 52 12 18 43 6 4
5 86 12 8
Genera
tion 1
Genera
tion 2
Genera
tion 3
Genera
tion 4
Genera
tion 5
0
10
20
30
40
50
60
70
80
90
100Dot Shade/Color Histogram
0% Shade 50% Shade100% Shade
Num
ber
of D
ots
Starting Population Surviving Population
Generation number
0%color
50%color
100%color
0%color
50%color
100%color
1 10 10 10 9 5 7
2 18 10 14 15 4 7
3 30 8 14 26 6 9
4 52 12 18 43 6 4
5 86 12 8
Generation 1 Generation 2 Generation 3 Generation 4 Generation 50
10
20
30
40
50
60
Average ColorSh
ade
%
50% 45% 35% 29% 13%
Gen 1 Gen 2 Gen 3 Gen 4 Gen 5
• Get a set of questions-(1 per person) from the front counter• Answer the questions using
the class data
Generation 1 Generation 2 Generation 3 Generation 4 Generation 50
10
20
30
40
50
60
Average ColorSh
ade
%