block day- may 23, 2012

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

%