Ch 16: Evolution of Population

Notes #3

Ch 16: Evolution of Population

What makes up a Population?

ANS: Organisms that belong to the same species and live in the same area.

Human Population in Alhambra

Total Population: 85, 077

What is a Species?

ANS: Members of the same population that can interbreed (mate) and have fertile offsprings

Ex. Horse + Horse = Pony (same species)

What is a Gene Pool?

ANS: Total # of genes found in a population at one time and area

Ex. Gene pool for field mouse fur B = Black fur; b = brown

48%Bb

36%bb 16%

BBGene poolin Field mousePopulation

Phenotype64% Black36% brown

Causes of Genetic Variations in a Population

(4 types)1. Mutations: Changes in the DNA lead to

genetic and physical differences. Ex. Wild-type Fruit Fly vs White-eye fly

2. Gene Shuffling

Mixing of genes during crossing over in Meiosis

Independent Assortment of genes into sex cells (gametes)

Ex. BbHH

BH bH

3. Genetic Drift

Tragic events that change the future genotype of a small population

Ex. Small Population of Green & Brown Beetles exist, then catastrophic event occurs, leaving a limited # of survivors

Genetic Drift of a Small Population of Beetles

Which colored beetle will dominate the population in the next 10 years?ANS: BrownWhy?

4. Gene FlowIt is the migration of genes moving in and

out of a population; leads to the intro of new genes

Ex. Two separate populations of beetles (Green vs Brown), one brown beetle migrates and introduces new genes to green beetle population

Process of Speciation

What is Speciation?ANS: Process where new species are formed

due to some type of isolation mechanism

Isolation Mechanisms Creating New Species

Types of Isolation Mechanism

1. Geographic Isolation: 2 population separated by geographic barriers (rivers, mountains,valleys, large bodies of water) can no longer meet or breed together.

Ex. Two population of squirrels separated by a river, evolved and became more different from each other over time

Geographic Isolation

2. Reproductive Isolation

Occurs when 2 different species can’t breed and produce fertile offspring

What do you get when you mate a horse with a donkey?

A mule. Which is incapable of having its own offspring, b/c the parents are not the SAME species.

+ =

Sterile Hybridmother father

(2 types)

a. Behavioral Isolation: 2 populations can’t breed or understand each other b/c they have different mating rituals/calls.

Ex. 2 population of birds (Pigeons & Crows) can’t mate b/c they sing different mating songs to attract mates

b. Temporal Isolation

2 populations have different mating seasons or feeding times, so they won’t meet and mate with each other.

Ex. One species of birds feeds during the morning and the other feeds at night, both won’t be able to meet and mate

Natural Selection Affecting Phenotype of a Population

Types of Natural Selection on Physical Traits

3 Types of Selection1) Directional Selection2) Stabilizing Selection3) Disruptive Selection

Background Information

Moth Survival Rate during the Industrial Revolution

(Black Winged vs. Grey Winged vs White Winged Moths)

Factories built & ashes from burning coal polluted the surrounds

1800s

Types of Moths

Black

Peppered

White

Moths’ Natural Predator

Mmmm…I love eating moths!

1) Directional Selection

Natural Selection favors the survival of one extreme phenotype compared to the others

Environment: Entire area covered in black ash

Which type of Moth will have higher fitness (survival)?____________

Black Winged

What will the curve look like? Graph below

# of MothsIn Pop.

(Moth wing color)

White BlackPeppered

OriginalPopulation

PopulationAfter Selection

2) Stabilizing Selection

Natural Selection favors the survival of the intermediate/mixed phenotype & against the extreme colored ones

Environment: Snow that is mixed with black ash

Which type of moth will have a higher fitness? ______________

Peppered Winged

What will the curve look like? Graph below

# of MothsIn Pop.

White Peppered Black

(Moth wing color)

PopulationAfter Selection

OriginalPopulation

Selection against extremes

3. Disruptive Selection

Natural Selection favors the survival of the two extreme phenotypes and against the intermediate/mixed ones.

Environment: One side of town covered in black ashes and the other covered in snow

Which type of moth(s) will have a higher fitness?________________

Peppered winged

What will the curve look like? Graph below

# of MothsIn Pop.

White Peppered Black(Moth wing color)

PopulationAfter Selection

OriginalPopulation

Selection against the intermediate

Question of the day

If a new moth eating bird is introduced to the environment and eats only black winged moths, which Selection will the moth’s population show?

A) Stabilizing SelectionB) Disruptive SelectionC) Directional Selection

Which moths will dominate the surrounds? ____________White winged

Classwork

Section 16-1, 16-2, 16-3 (Wkbook; Answers ONLY)

Section Assessment (Write down Q’s & A’s_16-1; p. 396; #1-4 16-2; p. 402; #1-5 16-3; p. 410; #1-4Stamps Needed for All work

Make sure to finish Per 2’s Classwork (Section 15-3 Wkbk & Section Assessment 15-3 from Mon)