Transcript Chpt. 13- Evolutionx - TJ

Chapter 13Evolution
13.1-Voyage of Charles Darwin
I. Voyage of the Beagle
A. Beliefs before he left
1. Accepted the view that God was
responsible for the creation of all
species
2. Believed that God designed each
species of plant and animal to match
its habitat
3. Believed that most species were
unchanging
II. The voyage
A. Galapagos Islands
1. Darwin repeatedly saw
patterns suggesting that
species changed over
time leading to new
species
2. Darwin’s finches
a. 1st Darwin noticed that there were several different species
of finches each specialized to catch food in a different way
b. 2nd Darwin noticed that all the different species of finches
closely resembled one species of South American finch
1. In addition, noticed that all animals and plants on the
island closely resembled those of the nearby coast of
S.A.
B. The question
1. Why did the plants and animals of the Galapagos Islands
resemble the plants and animals of the coast of S.A.
2. If each plant and animal was designed for a particular
environment, then why are there not the same animals and
plants on islands with similar environments
C. The answer
1. A few organism from S.A. must have migrated to the islands
2. Organisms migrated from island to island
3. Over time these plants and animals changed giving rise to new
species
4. Thus, you have evolution
13.2-Darwin proposed natural selection as the mechanism of evolution
I. Evolution: Descent with Modification
A. Descent with modification
1. All present day species arose from previous ancestors
2. As these ancestors spread into new environments they
accumulated diverse modifications (i.e-adaptations)
a. Over millions of years of modifications these organisms
became better adapted for survival giving rise to present
day organisms
B. Darwin proposed natural selection as the mech. of evolution
1. Artificial Selection
a. 1st observation by Darwin
2. Natural selection
a. Members of a pop. vary in the traits they have inherited
1. Individuals with traits giving them an increased chance
of survival & reproduction leave more offspring
b. Organism have a capacity to produce more offspring than
the environment can sustain
1. There becomes a struggle for survival
2. Only those that have inherited certain traits making
them better suited for survival will survive
C. 3 key points to evolution by natural selection
1. Individuals DO NOT evolve
a. Adaptations occur from generation to generation
within a given population
1. How?
2. Natural selection can only amplify or diminish heritable traits
a. Only if traits are coded for in the genes of the gametes will
they be passed to the next generation
3. Evolution is not goal directed
a. Does not lead to a perfectly adapted organisms
b. Environmental stresses vary from place to place and over
time
c. Evolution is a compromise
13.3-Observing natural selection in action
I. Pesticide resistance
II. Peppered Moth
A. The peppered moth
1. Up to 1850’s
a. dark gray peppered moths were rare
b. treasured by British butterfly and moth collectors
c. almost all peppered moths were pale in color
2. around 1850
a. there was a shift in peppered moth coloring
b. the dark gray peppered moth began to become more common
1. usually in heavily industrialized areas of England
3. Why did this event occur?
a. Darwin’s theory of evolution by natural selection provides a
hypothesis
b. Color change coincided with the increase in the number of
factories in England
c. Pale tree trunks became blackened with pollution
1. dark moths escaped being eaten by birds while pale
moths were not
2. overtime the dark moth became more common
III. Antibiotic resistance
A. Penicillin
1. Who?
a. Alexander Fleming
2. When?
a. 1928
3. What?
a. Fungus
13.4/13.5-The Evidence for evolution
I. Understanding the fossil record
A. Fossils are any traces of dead organisms
1. Footprints, insects trapped in sap, bones
B. Dating Fossils
1. Strata
2. Radioactive atoms
a. Contains an unstable combination of protons and neutrons
1. Since it is unstable it will  into a more stable atom of
another element
b. Scientists measure the amount of radioactive decay of
radioactive atoms
1. Rate of decay of a radioactive element is constant
a. Measured as a half-life
1. The amount of time it takes for one-half of the
radioactive atom to decay
2. Example-carbon 14
a. Found in all living things
b. Half-life =5,730
c. 12g sample will have 6g left after 5,730
II. Biogeography
A. Galapagos Islands
1. Species on island resemble species on coast more than they
resemble species on similar islands farther away
III. Comparative anatomy
A. Comparing the way organisms are put together provides
important evidence of evolution
B. Homologous structures
1. Modified versions of structures that occurred in a common
ancestor
a. Similar structure but perform different functions
2. example
a. appear to be very different, BUT
C. Vestigial structures
1. Structures that have marginal or no importance to an organism
2. Remnants of an organism’s evolutionary past
a. pelvis of a whale, eyes of cave salamanders
D. Transitional forms link new species to old
1. Intermediate forms between old and new
2. Tiktaalik (tic-TAH-lick)
a. 375 million years old
3. Hand fish
IV. Molecular biology
A. Concrete evidence for showing relatedness between species
1. Descent with modification
2. If species have changes over time, then their genes will also
change over time
a. The more time has passed the more genes will change
b. The more closely related 2 species are the more their DNA
will be similar
3. Are all life forms related?
a. Molecular biology provides strong evidence
1. All life forms use the same DNA, RNA, & genetic code
2. Bacteria and humans have many genes in common
B. DNA & protein
1. Compare the protein cytochrome c
a. essential for cellular respiration
b. human & chimps identical in all 104 AA
c. human & dogs differ by 13 AA
d. human & rattlesnake differ by 20 AA
e. What does this show
1. chimps are very closely related to humans
2. dogs are more closely related to humans than
rattlesnakes
13.9-Showing Evolution Hardy-Weinberg Equation
I. Intro
A. Natural selction
1. What does natural selection directly act on?
a. Traits
2. Traits are a result of what?
a. Genes
3. Genes are made of what?
a. Alleles
4. So, natural selection indirectly acts on what?
a. Alleles
B. Populations
1. A group of individuals of the same species living in the same
place at the same time
2. Remember individuals do not evolve, populations evolve
a. We can measure evolution as a change in heritable traits in
a population over time
1. Which means a change in alleles
3. How can we measure a Δ in a population look at the gene
pool
a. Gene pool
1. All the alleles within a population for a particular trait
2. Represented as a frequency
a. If there is any change in allele frequency over a
number of generations than evolution has occured
II. The Hardy-Weinberg Equalibrium
A. Basic Principle
1. Tests whether a population is evolving
B. Allele frequencies
1. % of alleles within a given population compared to total # of
alleles in a population
a. Remember that each individual has ? alleles/loci
b. p= Dominant allele
q= recessive allele
2. When dealing with 2 or more alleles/loci, sum of all
frequencies must equal 1 (100%)
a. p + q = 1
3. Example
RR = Red rr = White Rr = pink
340 individuals RR
40 individuals rr
180 individuals Rr
560 individuals
How many alleles in the population?
1120
How many R alleles are there and how many r alleles?
R= (340 ind. X 2) + 180 ind. = 860
r= (40 ind. X 2) + 180 ind. = 260
What is the frequency of p & q?
p = 860/1120 = .77
q = 260/1120 = .23
Double check yourself p+q=1
III. The Hardy-Weinberg Principle
A. Describes a gene pool of a population that is not evolving
1. Hardy-Weinberg equilibrium
a. Allele & genotype frequencies do not ∆ from generation to
generation
B. The equation
1. p2 + 2pq + q2 = 1 (genotype frequencies)
a. p2  Expected frequency of homozygous dominant
b. q2  Expected frequency of homozygous recessive
c. 2pq  Expected frequency of heterozygous
C. Conditions for the Hardy-Weinberg Equilibrium
1. If the population is not evolving (allele frequencies are not
changing over generations) then these 5 conditions are being
met
a. No mutations
b. Random mating
c. No natural selection
d. Extremely large population size
e. No Migration
2. If allele frequencies are changing over generations
(evolution) then one or more of the following conditions is
not met
D. Applying the Hardy-Weinberg principle
1. Must assume 5 conditions are being met
In the town of Thomasville, 78% of Thomasens have extreme intelligence, a
dominant trait. Complete the following information about this population.
q2 =
q=
p=
p2 =
2pq=
78% have the dominant trait = 78% are RR & Rr
Which means that 12% are rr
SO
q2= .22 (frequency of homozygous recessive trait)
q= the √ of .22 = .47
p= 1-q = 1-.47 = .53
p2= .532 = .28
2pq= 2(.65)(.35) = .50
Double Check Your Answer p2+2pq+q2=1 .28+.50+.22=1
16% of the human population has a recessive trait. What are the genotypic &
allelic frequencies of the population?
q2= .16
q= .4
p= .6
p2= .36
2pq= .48