Download Evolution-Chapter 11

What traits of
penguins are
adaptive to
the Antarctic
environment?
What factors
would result in
changes to
the genetic
variation of
penguins in a
colony?
Traits: insulating layer of blubber,
feathers, brood pouch
 Changes in genetic variation: mutation,
recombination of alleles

Only those penguins that successfully
reproduce and raise live, healthy chicks
will pass on their genes and the
phenotypes that they code for .
 Individuals do not evolve, populations
do!

Differences in populations, both
genotypic and phenotypic.
 Let’s look at the penguin example again!




1. Do you see any
variation in this
population of
penguins?
2. How would you
describe variation in
a human
population?
3. How might this
population of
penguins change if
Antarctica suddenly
got much warmer?

We are going to look at the phenotypic
variation of two traits: Hitchhiker’s Thumb
and Regular Thumb.
Hitchhiker’s
Thumb
Yes
No
Total
Population
Regular
Thumb
Calculate the frequency and
percentage of each trait.
 Hitchhiker’s thumb and tongue rolling
are examples of phenotypic variation
within a population.
 What would happen to the genetic
variation of the population if, for
example, all of the hitchhiker thumbs left
the class or we added 10 more people
with hitchhikers thumb?

Frequencies would change. Perhaps
some traits would disappear completely.
 Remember: genetic variation is the basis
for the evolution of populations.

What are genes?
 What do you think of when you hear the
word pool?


Connecting Darwinian evolution to
genetics and modern understanding of
inheritance.
Trait: the result of genetic instructions to
DNA (“genes”)
 Variation: results of changes to genes =
mutations
 Alleles: different variants in traits
 Evolution: changes in allele frequencies
over time.

› Example- The Grants studies on the
Galapagos finches
They studied the finch population on
Daphne Major
 Measured the beak sizes every year (just
like you did)
 They made the connection that the
beak sizes fluctuate based on
environmental conditions (drought,
excessive rain, size of seeds)

Changes the population.
 Populations change based on the
individuals fitness of members of that
population.
 Individuals that are “fit” will survive and
reproduce, the frequency (number of
occurrences) of alleles in the next
generation will change.


Phenotype- Physical make-up (you can
see these traits)
› Example: Blue feathers, Claws, beak sizes

Genotype: Genetic make-up, the alleles
an individual has for a specific trait.
› Homozygous: Two copies of the same allele,
TT or tt
› Heterozygous: Two copies of different alleles,
Tt
Sexual reproduction
 One from mom and one from dad

Alleles control the production of proteins
and the proteins determine traits.
 Some are dominant and some are
recessive.

Just
because
it’s
dominant
does not
mean the
organism is
more fit.
Depending upon the demands of the
environment, different phenotypes will
be more or less fit.
 Fitness: the ability of an organism to
survive and pass on those alleles to
future generations.
 What determines fitness?

› ENVIRONMENT

Pesticide resistance: An organism that is
resistant to a pesticide (meaning it can’t
kill them) are more fit than those that die
when the pesticide is sprayed on them /
eat them.
 Artificial
Selection: Humans pick
and choose which traits they
want to breed.
› Example: Labradoodle:
Hypoallergenic and it doesn’t shed
= perfect dog= $$$$$$
A population shares a common gene pool.



Genetic variation leads to phenotypic (ex- body
size and feathers in penguins) variation.
Phenotypic variation is necessary for natural
selection (can be a large range from tall skinny
penguins to short fat penguins).
Genetic variation is stored in a population’s gene
pool.
› Gene pool- the combined alleles of all the individuals
in a population. Different combos are caused from
different animals reproducing together.
› Alleles= what your chromosomes are made of. Traits.
 Allele
frequencies measure genetic
variation.
– measures how common allele is in population
– can be calculated for each allele in gene pool
If brown skin color became more
advantageous, what would likely happen to
the frequencies of alleles G and g in this gene
pool?
 What does advantageous mean in this
example?

The G allele would decrease and the g
allele would increase in frequency and
become more abundant in the gene
pool.
 Advantageous means that the gene is
more “fit” therefore the chance of
passing it onto its offspring is great
because it’s beneficial to the species
survival.


Mutation is a random change in the DNA of a gene.
– Can form new allele
– Can be passed on to
offspring if in
reproductive cells
• Recombination forms new combinations of alleles.
– Usually occurs during meiosis
(sexual reproduction)
– Parents’ alleles arranged in new
ways, it’s like shuffling a deck of
cards. The alleles from both
parents get mixed up and it results
in many different combinations.
Hybridization
is the crossing
of two different species
that share common genes.
› occurs when individuals
can’t find a mate of their
own species
› topic of current scientific
research
Living among similar species
 Can’t find a mate
 Humans do it to better a product / make
an animal more interesting and
marketable.

Natural Selection in Populations

A normal distribution = bell-shaped curve.
– Highest frequency near
mean or middle value. These
phenotypes seem to be the
most common.
– Frequencies decrease
toward each extreme value
being the least favorable
traits.
–Environmental conditions
can change and a certain
phenotype can become
advantageous (nature favors
this)

Microevolution is evolution within a population.
› Observable change in the allele frequencies over
time.
› Occurs in small changes= “micro”
› Can result from natural selection
› There are three stages:
 1. Directional
 2. Stabilizing
 3. Disruptive selection



Causes a shift in a populations phenotypic
distribution. A phenotype that was once
rare in a population becomes more
common.
Ex- Antibiotic resistance (over 200 types of
bacteria have some sort of antibiotic
resistance).
Ex- Ostriches speed and ability to kick
predators, octopus mimicking others, speed
of a cheetah, the jaws and teeth of a
jaguar
 The
intermediate phenotype is favored
and becomes more common in the
population.
 Ex- Gall Flies
They lay their eggs in developing shoots of the tall
goldenrod plant. The fly larvae produce a chemical
that causes the plant tissue to swell around them.
 The mass of tissue = gall. The gall is a home where
the larvae develop.
 There is a range of phenotypes in body size. Each
body size causes a certain size gall to form. The two
main predators of gall flies prefer a certain size.

› Downy woodpeckers like the larger galls
› Parasitic wasp lays its own eggs in the small galls, after they
hatch, they eat the gall fly larvae.

This is a parasitic relationship: the fly receives shelter
and food and the plant is harmed by decreasing its
growth rate.


Supports both extreme phenotypes
while the intermediate are selected
against by something in nature.
Example: Rabbits
Gene flow- the movement of alleles from
one population to another.
 Gene flow occurs when individuals join new
populations and reproduce.
 Increases genetic variation of the receiving
population and keeps the neighboring
populations similar.
 Low gene flow increases the chance that
two populations will evolve into different
species.


Bald Eagle- They
are hatched and
banded on the Gulf
Coast of Florida.
Some of these
hatchlings will leave
the area once they
learn how to fly and
migrate North.
These eagles may
be joining a new
population.






Changes in allele frequencies that are due to
chance.
Causes a loss of genetic diversity in a population
The allele is eliminated
Most common in small populations.
Two processes: Bottleneck Effect and the
Founder Effect
Problems it causes:
› Population loses genetic variation= populations will be
less likely to adapt.
› Lethal alleles that are carried in the homozygous
individual may be carried by the heterozygous animal,
and could potentially become more common in the
gene pool due to chance alone.



Genetic drift that occurs after a catastrophic
event greatly reduces the size of a population.
Ex- Overhunting of Northern elephant seals. They
were hunted to near extinction in the late 1800’s
for its blubber (used to make oil). Population
went to about 20-100 individuals, but since the
males are extremely territorial and fight for
reproductive rights, very few males actually
passed their genes on to the next generation.
Now the population is up around 100,000 ,
however the genetic variability in the population
is very low because many alleles were
completely lost during this, therefore leading to
complete removal from the gene pool.
Genetic drift that occurs after a small
number of individuals colonize a new
area.
 Ex- Amish of Lancaster, Pa- have a high
rate of Ellis-van Crevald Syndrome and
has become more common in this
specific population of Amish people. This
syndrome has been traced back to the
founding couples of the community.
 Polydactyly in Amish people.

http://www.nejm.org/doi/full/10.1056/N
EJMicm1100857
 Certain
traits increase mating success.
 Cost differs between sexes:
› Males- produce many sperm
continuously, therefore each sperm has
little value. Many investments at little cost
to them.
› Females- limited in the number of
offspring they can produce in each
cycle. Each investment is valuable and
they want it to turn out successful.
The cost to the female makes them very
picky about their mate.
 There are two types of selection:

› 1. Intrasexual selection- males compete and
the winner gets to mate with the female.
More focused on physical and aggressive
fighting behavior. Ex- Bighorn sheep
› 2. Intersexual selection- males display traits
that attract the female. Usually a secondary
sex characteristic that tells the female they
are attractive and fit. Ex- male peacock
fanning out its tail.



Some traits may be linked with
genes for good health and
fertility.
Some males offer traits that say
he can be the better father
and defend his offspring from
predators.
Some traits become
exaggerated over time.
Example- red air sacs of the
male frigate bird.
Male giraffes
 Bighorn
Sheep
 Elephant seals
 Moose
 Elk

Peacock
 Sage Grouse
 Frog calls
 Male guppies with
bright blue and
orange spots


https://www.youtube.com/watch?v=gqsMTZQ-pmE

https://www.youtube.com/watch?v=WdnPQrqniIE

https://www.youtube.com/watch?v=ZPFkmwo8DQU

https://www.youtube.com/watch?v=6x4FJseTnJU

https://www.youtube.com/watch?v=fR7Dqf0vzzQ
KEY CONCEPT
Hardy-Weinberg equilibrium provides a framework for understanding
how populations evolve.

The ability to quantify the amount of evolutionary
change from generation to generation to
determine how evolution is affecting the
population.
Going
back
to 7th
Grade!
Give an example of heterozygous alleles
(there are two).
 Give an example of homozygous alleles.
 Sample problem 1. If an organism that is
heterozygous for brown eyes reproduces
with an organism that is homozygous
recessive for blue eyes, what will be the
chance that their offspring will have blue
eyes?

1. Add alleles
from scenario.
 2. Cross them!
 3. Always put the
dominant letter
first (capital
letter)
 4. Remember
there are four
boxes and if the
total is to equal
100% then they
each must equal
25%.
B

b
b
b
50% Bb and 50% bb
 Ratio= 1:1

› Very large population: no genetic drift
› No emigration or immigration: no gene flow
› No mutations: no new alleles added to gene
pool
› Random mating:
no sexual selection
› No natural selection:
all traits aid equally
in survival
NO REAL POPULATION IS
IN HARDY WEINBERG
EQUILIBRIUM….. WHY
DO YOU THINK????
Real populations rarely
meet all five conditions.
Real population data
is
compared to a
model.
Models are used to
study how
populations
evolve.
p2 + 2pq + q2 = 1
 p=frequency of the dominant allele, ex-T
 q= frequency of the recessive allele, ex-t
 p2= frequency of the homozygous dominant
allele, ex- TT
 q2= frequency of the homozygous recessive
allele, ex- tt
 2pq= frequency of the heterozygous allele, ex Tt

p+q=1
 Remember p is dominant and q is
recessive.

p2 + 2pq + q2 = 1
 To solve a HW equation, determine the
frequency of the recessive individual first,
and then solve the rest of the equation!


In pea plants, the allele for purple flowers
is dominant to the allele for white flowers.
If 99% of the plants in the population
have purple flowers, determine the
percentage of heterozygotes in the
population.
1. We know that 99% have purple flowers so
just turn that into a decimal format and that is
your frequency.
 2. p2 + 2pq = .99 (we took the q2 out because
that is recessive and we want to find that first)
 3. q2 = .01 (1 percent)
 4. How do you find just q? It’s squared so we
have to take the square root in order to find
the true value of q.
 5. The square root of .01 = .1 so q=.1

6. If q=.1, now we have to find p.
 7. If p + q = 1, then p + .1 = 1
p= .9
 8. Check your work: .9 + .1 = 1
 9. Now that we know p we can solve for p2
 10. p2 = .92 = .81
 11. Remember we are trying to find the
frequency of heterozygotes, so now we
need to figure out the 2pq.
 12. 2 (.9)(.1)= .18, therefore 18% of our
population are heterozygotes for flower
color.
 Note- if the problem does not equal 1, then
the population is NOT in HW equilibrium.

To determine how a population is
evolving from generation to generation.
 To help to determine which evolutionary
pressures are affecting a population
more / less.

Use the HW equation to calculate
predicted genotype frequencies for this
population.
 In a population of 1,000 fish, 640 have
forked tail fins and 360 have smooth tail
fins. Tail fin shape is determined by two
alleles: T is dominant for forked and t is
recessive for smooth.



Find q2, the frequency of smooth finned
fish (recessive homozygotes).
q2 = 360 smooth finned fish
1000 fish in population
= .36
To find the predicted value of q, take the
square root of q2
 q= √.36 = .6

Use the equation p+q=1 to find the
predicted value of p. Rearrange the
equation to solve for p.
p=1-q
p=1- .6=.4
p=.4 and q=.6

Calculate the predicted genotype
frequencies from the predicted allele
frequencies.
p2 = .42 = .16 = 16%
2pq= 2 X (.4) X (.6) = .48 = 48%
q2 = .62 = .36 = 36%


See worksheet of practice problems.






1. Genetic Drift
2. Gene Flow
3. Mutation
4. Sexual Selection
5. Natural Selection
Evolution is continuous, although very slow
to the human eye, it is a response to
changes. As environments change they
can either adapt or face extinction.

Environments are constantly changing,
which changes what traits are adaptive.

No, because the females select mates
based on the size of their tails-> sexual
selection is occurring.

In order to fully understand speciation
we need to take a look at Taxonomy so
we can understand the “tree of life.”
Speciation explains evolutionary
branching and diversification so let’s
learn the basics first 

Why do you think it’s important for every
living organism on the planet to have a
specific name?
Carl Linnaeus (1707-1778)
 He came up with a means of naming
organisms that was simple and universal.
 Problem- before his method people were
naming organisms multiple names that were
really long, and there wasn’t any
consistency.
 Taxonomy- science of classifying organisms
and assigning each organism a universally
accepted name.


Linnaeus came up with binomial
nomenclature-> two word naming
system
› Genus, species
› Always in italics
› Genus is capitalized and species
lowercased
› Genus always comes first, followed by
species
› Ex- Homo sapiens
Mountain Lion= Puma concolor
 Red Maple Tree= Acer rubrum
 Human= Homo sapiens
 Barn Owl= Tyto alba
 Gray Wolf= Canis lupis


What is a species?








Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Domain is
not typically
represented
in the
diagrams.
Write this
order on
your paint
chip color
palette.
Dear King Phillip Came Over From Great Spain!!!!
 Arises
by evolutionary change
leading to the present biodiversity
we see.
 Divided into Three Domains:
› 1. Bacteria- single celled prokaryotes
(no nucleus)
› 2. Archaea- single celled prokaryotes
(no nucleus)
› 3. Eukarya- Plants and Animals,
complex organelles and multicellular



Bacteria
Archaea
Eukarya






Eubacteria
Archaea
AnimaliaAnimals
Plantae- Plants
Fungi- Fungus
Protista- animal
like and plant
like





True bacteria, mostly heterotrophic, live in
all sorts of environments
Prokaryotic
Largest groups of organisms on Earth
Only a small amount are disease causing
Most have very important roles:
› Photoautotrophs such as cyanobacteria
› Saprophytes- decomposers that break down
dead material.
› Symbionts- they have a relationship with other
organisms






Most recent domain, 1970’s
Prokaryotic-single celled
Live in extreme environments with high
temperatures and some produce methane.
Vast difference in genetic and biochemical
make-up from other bacterium.
Microscopically similar in looks so it is likely that
it has been around for a long time but we just
missed it.
Live in extreme environments
› Hot springs, hydrothermal vents, extremely acidic or
alkaline water, anoxic mud swamps, petroleum
deposits, and the digestive tracts of cows, termites,
and marine life where they produce methane.


Eukarytotes= have a nucleus, membrane
bound organelles, and are unicellular and / or
multicellular
4 Kingdoms
› 1. Kingdom Protista: unicellular eukaryotes,
multicellular algae (dinoflagellates, diatoms, etc)
› 2. Kingdom Plantae: have cells walls, cellulose, and
obtain energy through photosynthesis.
› 3. Kingdom Fungi: Cell walls are made of chitin,
obtain energy by secreting enzymes and absorb
the products they release.
› 4. Kingdom Animalia- no cell walls, obtain energy
by ingesting other organisms.
Archaebacteria
 Eubacteria
 Protista
 Fungi
 Plantae
 Animalia

1. Cell Type
 2. Cell Organization
 3. Mode of Nutrition
 4. Method of Reproduction
 5. Motility


PROKARYOTIC:
› no organized nucleus
› no internal
membranes
› has a rigid, but
flexible cell wall that
surrounds and
protects individual
bacterial cells

EUKARYOTIC:
› organized nucleus
› internal membranes
› cell wall
UNICELLULAR: single-celled ,all life
functions, solitary or colonial (chains or
clumps)
 MULTICELLULAR: many-celled


Unicellular
• Multicellular
LEVELS OF ORGANIZATION (Tissue
Differentiation)

1. cells, 2. tissues, 3. organs, 4. organ
system, 5. organism






PEPTIDOGLYCAN: contain peptidoglycan, a
complex web-like molecule; found only in the
Eubacteria
UNCOMMON LIPIDS: nonpeptidoglycan,
contains uncommon lipids, found only in
Archaebacteria
PECTIN: contain pectin a complex
polysaccharide, found in most Protista
CELLULOSE: contain cellulose a complex
polysaccharide; found in Plantae
CHITIN: contain chitin, a tough material like that
making up crab shells; found only in the Fungi
 AUTOTROPHIC:
make their own
food through photosynthesis.
 CHEMOTROPHIC: makes its own
food through chemosynthesis.
 HETEROTROPHIC: get food from
other organism, ingestion or
absorption
ASEXUAL: only one parent, offspring
genetically identical to parent, no union
of gametes
 SEXUAL: two parents, offspring
genetically different from parents (a
combination of the two), union of
gametes

MOTILE: ability to move from place to
place, may only be motile in larval stage
 NON-MOTILE: cannot move from place
to place, maybe sessile (attached to a
surface)

Eubacteria
Archaebacteria
Protista
Fungus
Plant
Animal
Cell Type
Prokaryotic
Prokaryotic
Eukaryotic
Eukaryotic
Eukaryotic
Eukaryotic
Number of Cells
Unicellular
Unicellular
Most Unicellular
Most Multicellular
Multicellular
Multicellular
Cell
Cell
Most cell
Most tissue
Systems
Systems
Cell Wall (what it’s
made of)
Peptidoglycan
Contains uncommon
lipids
Mode of Nutrition
Autotroph &
Heterotroph
Level of
Organization
Pectin or none
Reproduction
Motility
Ecological
Importance
Fun Facts
Chitin
Cellulose
None
Autotroph &
Heterotroph
(green algae:
cellulose)
Autotroph &
Heterotroph
Heterotroph
(absorption)
Autotroph
Heterotroph
Asexual
Asexual
Sexual/Asexual
Sexual/Asexual
Sexual & Asexual
Sexual & Asexual
Some motile
Non-motile
Motile & non-motile
Most non-motile
Non-motile
Motile
decomposers
Algae :major aquatic
oxygen & food
producers, algal
bloom
Decomposers
Major oxygen &
food source
(photosynthesis trophic level 1)
Human impact on
environment
Can’t live without
them
Invertebrates
fix nitrogen &
decomposers
Gave rise to
eukaryote
organelles
Can live in extreme
conditions
Ancestors of
eukaryotes
Escherichia coli
Examples
Methanobacteria
Streptococcus
Toothpaste teeth
whiteners
Fermented food
products
Food source
Medicine source
Vertebrates
Antibiotics
Algae, diatoms,
amoebas,
Lichen, yeast,
mushrooms
Trees, flowers,
grass
sponges
mammals
YES- this was all done prior to molecular
evidence / DNA
 Linnaeus focuses on physical similarities
only.
 Physical similarities between two species
can be a result from living in the same
environment, not because they are
genetically related.

A giant panda and the raccoon have
similar ears and snouts, and have been
placed in the same family according to
Linnaean classification.
 Genetic evidence has shown us that the
giant panda is more closely related to
other bears than raccoons.
 The red panda is more closely related to
raccoons than to giant pandas.

Modern classification is based on figuring
out evolutionary relationships using
evidence from living species, molecular
DNA, and the fossil record.
 Phylogeny: Evolutionary history for a
group of species.
 Phylogenies are like a family tree. The
branches show how different species are
related to each other.

Classification based on common
ancestry.
 Goal= to place species in the order in
which they descended from a common
ancestor.
 Cladogram= Evolutionary tree that
proposes how species may be related to
each other through common ancestors.

Cladistics and cladogram both have the
root “clade” which means a group of
species that shares a common ancestor.
 Example: Glyptodon was the size a small
car and lived about 10,000 years ago. It
is the common ancestor to about 20
species of armadillos.

Absolutely!
 Some traits such as hard shells in
armadillos have not changed, but size
has certainly changed.
 How do we figure out evolutionary
relationships among a group of species?

› Derived characters= traits that are shared by
some species but are not present in others.



Derived characteristics: traits that are
shared by some species but are not present
in others.
Node: intersection of two branches.
Represents the most recent common
ancestor shared by the entire clade.
Clade: a group of organisms that share
certain characteristics derived from a
common ancestor.
› Identify a clade by the “snip rule.” Wherever you
“snip” a branch under a node, a clade falls off.
1. What trait separates
Lampreys from tuna on this
cladogram?
2. What separates a
salamander from a turtle?
3. Which organism is most
related to the leopard?
4. What 4 traits do these
two organisms share?
5. Which organism will
have DNA most similar to
the turtle?
6. Which organism’s DNA
will differ the most from the
leopard?
7. What trait separates
amphibians from primates
on this cladogram?
8. What separates rabbits
and primates from
crocodiles on this
cladogram?
9. Which organism is most
related to the bird on this
cladogram?
10. What 5 traits do these
two organisms share?
11. Which organism will
have DNA most similar to
the bird?

Shared or identical sequences of DNA
give hard proof of common ancestry,
whereas shared traits or similar
characteristics can be the result of
convergent evolution.

First, let’s play a game of telephone.
Did the message stay the same from the
beginning to the end?
 No, just like DNA it changed a little bit
from person to person.
 DNA changes a little bit from generation
to generation.

Models that use mutation rates to measure
evolutionary time.
 The rate at which mutations occur is
referred to as the ‘ticking” that powers the
molecular clock.
 The more time that has passed since two
species have diverged from a common
ancestor, the more mutations will have built
up, resulting in making two species more
different from each other on the molecular
level (DNA).

Have to find links between molecular
data and real time data.
 Typically they need to know the timing of
a geological event that is known to have
separated the species.
 Example: Scientists know that marsupials
of Australia and South America diverged
about 200 million years ago when the
continents split.

Compare the molecular data (DNA /
amino acid sequences) with the first
appearance of each type of organism in
the fossil record.
 Use the dates and confirm that the
number of amino acid differences
increase with the evolutionary time
between each group of species.

Animal
Amino Acid
Differences
Compared with
Humans
Appearance in Fossil
Record(millions of years
ago)
Mouse
16
70
Human
18
70
Bird
35
270
Frog
62
350
Shark
79
450
Animal species that evolved longer ago compared with
humans have more amino acid differences in the beta
chain of their hemoglobin
Which two
animals in this
table are least
related to
humans?

Humans and birds diverged more
recently than sharks.
Some changes / mutations in DNA
happen rather quickly, while others
occur very slowly.
 Scientists use mitochondrial DNA and
ribosomal DNA to measure appropriate
mutation rate.




DNA found in the mitochondria=
powerhouse of the cell (where energy is
made).
Mutation rate is 10X faster than that of
nuclear DNA (remember nucleus is the
control center of the cell)which makes it a
good molecular clock for closely related
species.
Always inherited from the mom because
the mitochondria are lost in a sperm cell
after fertilization.

Is from both parents.
Ribosomes, the little ball structures that
make proteins in the cell.
 Useful for studying distantly related
species. For example, species that
belong to different kingdoms and phyla.
 Lower mutation rate- ideal for longer
time periods
 Example: Bacteria Archaea diverged
from a common ancestor they share
with bacteria almost 4 billion years ago.


They are capable of mating and
producing fertile offspring.

They are unable to mate or produce
fertile offspring. At that point speciation
has occurred and they are officially
different species.

Separated, by themselves, in a remote
location, far away

Populations become isolated when there is
no gene flow.
› Isolated populations adapt to their own
environments.
› Genetic differences can add up over
generations and in time the two isolated
populations become more and more
genetically different.
› Individuals may also start to behave and look
differently as well.

Occurs when members of different
populations can no longer mate
successfully. The final stage in speciation.
› Not physically able to
› Can’t produce offspring that survive and
reproduce
› Different times
• Speciation is the rise of two or more species from one
existing species.

Rana aurora
and Rana boylii
breed at
different times.
I breed
January to
March
I breed
March
to May



Isolation caused by differences in courtship
or mating behaviors.
Could be through chemical scents (expanda), courtship dances of birds
(peacock), or songs and vocalizations
(frogs and birds).
Ex- over 2,000 species of fireflies are isolated
this way. Males and females produce
flashes of light to attract mates of their own
species. One species may emit a flash once
every second, while others emit a double
flash every 5.5 seconds.



Peacock- the faster the shake and
the more eyespots= the more
attractive he is to her.
Long Tailed widow bird- the longer
the tail the better. Flies around the
grassland showing the females his
long tail.
Sticklebacks- females prefer males
that are able to produce frequent
body shakes during courtship.
Leads to increased nest fanning.
 Geographic
Isolation
- Physical barriers divide populations into two or more groups such as rivers,
mountains, and dried up lakebeds.
- Ex- the Isthmus of Panama created a barrier for many marine species= prevented
them from crossing between the Atlantic and Pacific Oceans.
- Eventually the populations became genetically different.
- Ex- Snapping Shrimp- they look identical, however when males and females get
together they snap at each other instead of courting. They refuse to mate with each
other, therefore they formed different species.
When timing prevents reproduction
between populations.
 Reproduce at different times of the year /
season.
 Ex- Two species of pine tree that grow on
the Monterey Peninsula in California are
closely related. They have two different
pollination times . One sheds its pollen in
February and the other in April. These
species have likely evolved through
temporal isolation.

KEY CONCEPT
Evolution occurs in patterns.
Random events= mutations, genetic
drift, anything that can’t be predicted.
 Natural Selection= not random because
individuals with traits that are better
adapted for their environment have a
better chance of surviving and
reproducing than individuals without
these traits.

Different species must adapt to similar
environments.
 Defined as- evolution toward similar
characteristics in unrelated species.
 Ex- analogous structures such as wings
on a bird and insects.
 Ex- dolphins and sharks have evolved
similar tail fins that help them propel
through the water even though they are
separated by 300 million years.



Closely related species evolve in different
directions.
Ex- the kit fox and red fox- closely related
but grew up in different environments
therefore their appearances are different.
› Red fox- lives in temperate forests and has a
dark reddish coat that allows it to hide from
predators.
› Kit fox- lives in the desert and has large ears for
heat regulation.
Red Fox
Kit Fox
Ancestor
They are examples of convergent
evolution.
 They do not share a common ancestor
and the shells evolved as a means of
protection from predators.


Coevolution- two or more species evolve in
response to changes in each other.
› Usually a specialized relationship – mutualistic
› Ex- the ant and the acacia plant. The acacia
plant is covered with thorns that protect it from
larger herbivores, but small insects like caterpillars
can get in there and eat the sweet nectar which it
produces. There is a species of stinging ants that
live inside the thorns and feed on the nectar. The
ants protect the plant by stinging any organism
that comes close and tries to eat the plant.



“Evolutionary arms race”= species respond
to pressure from the other through a better
adaptation over many generations.
Ex- plants that produce chemicals so
organisms don’t eat them. Natural selection
favors organisms that can overcome the
effects of the chemicals.
Ex- thick shells and spines of murex snails are
an adaptive response to crabs preying on
them. Crabs have evolved to adapt by
growing more powerful claws that are
strong enough to crack the shells.
Extinction is the
elimination of a species
from Earth.
 Usually happens when a
species can’t adapt to a
change in its
environment.
 Background Extinctions
and Mass Extinctions.
 More than 90 % of all
animals that have lived
on Earth are extinct.

Iberian lynxI’m the most
endangered
animal in the
world.
Extinctions that occur continuously but at
a very low rate.
 Part of the cycle of life on Earth.
 Occur at the same rate as speciation
 Usually only affect one or a few species
in a small area.
 Caused by local changes in the
environment such as the introduction of
a new predator or low food supply.

More rare and intense
Often occur on the global level
Destroy many species, even families or orders
They are thought to occur suddenly in geologic time,
usually due to a catastrophic event like the Ice Age or
an asteroid.
 Five Mass extinctions in the past 600 million years.
 The most studied mass extinction, between the
Cretaceous and Paleocene periods about 65 million
years ago, killed off the dinosaurs and made room for
mammals to rapidly diversify and evolve
(www.nationalgeographic.com)
 The causes are unsolved mysteries but they think that
they may have been caused from volcanic eruptions
and asteroids, global warming, mass floods, etc.






Repeating patterns in the history of life.
Punctuated Equilibrium= bursts of evolutionary
activity (speciation) followed by long periods of
stability.
› Ex- Trilobite

Adaptive Radiation= rapid evolution of many
diverse species from ancestral species. Usually
adapted to a wide range of environments.
› Example- Early mammals: they barely resemble the
ones we know about today. 65 mya, they were small,
insect eaters, and mostly nocturnal.
 Fossils
can form in several ways:
› Permineralization
› Natural Casts
› Trace Fossils
› Amber Preserved Fossils
› Preserved Remains

Permineralization occurs when minerals carried
by water are deposited around a hard structure.

A natural cast forms when flowing water removes
all of the original tissue, leaving an impression.

Trace fossils record the activity of an organism.

Amber-preserved fossils are organisms that become trapped
in tree resin that hardens after the tree is buried.

Preserved remains form when an entire organism becomes
encased in material such as ice or volcanic ash.

Specific conditions are needed for
fossilization.
• Only a tiny percentage of living things became
fossils.

Relative dating
estimates the
time during which
an organism
lived.
› It compares the
placement
of fossils in layers
of rock.
› Scientists infer the
order in
which species
existed.

Radiometric dating uses decay of unstable
isotopes.
– Isotopes are atoms of an element that differ in their number of
neutrons.
neutrons
protons
– A half-life is the amount of time it takes for half of the isotope to decay.

Index fossils can provide the relative age of a rock layer.
› existed only during specific spans of time
› occurred in large geographic areas

Index fossils include fusulinids and trilobites.
Eras: last tens to hundreds of millions of
years and consist of two or more periods.
 Periods: Most commonly used units,
lasting tens of millions of years. Each
period is associated with a specific type
of rock system.
 Epochs: smallest unit of geologic time
and last several million years.

ological Time Scale
Organisms
nozoic Era- Recent Life
Quaternary
Includes all present life forms
Tertiary
Mammals, flowering plants, grasslands, insects, fishes,
and birds became more diversified. Primates
evolved.
sozoic Era
Cretaceous (Major Extinction)
Dinosaurs peaked and went extinct, birds survived
and flowering plants arose.
Jurassic
Dinosaurs diversified as well as early trees that are
common today. Oceans were full of squid and fish.
First birds arose.
Triassic (Major Extinction)
Following the largest mass extinction, dinosaurs
evolved, ferns and cycads evolved, and mammals
and flying reptiles arose.
eozoic Era- Ancient Life
Permian (Largest Mass Extinction)
Modern pine trees arose and Pangaea was formed
Carboniferous
Coal forming sediments were laid down in swamps,
fish continued to diversify, amphibians, insects, and
small reptiles were around,
Devonian (Major Extinction)
Fish diversified. First sharks, amphibians, and insects
showed up. First trees and forests arose.
Silurian
Earliest plants arose, glaciers melted and seas
formed, and jawless and freshwater fishes evolved.
Ordovician (Major Extinction)
Diverse marine invertebrates and early vertebrates.
Multicellular organisms first
appeared during the
Paleozoic era.
 The era began 544 million
years ago and ended 248
million years ago.
 The Cambrian explosion
led to a huge diversity of
animal species. All life was
found in the ocean.

• Life moved onto land in the middle of the
Paleozoic era.
The Mesozoic era is known as the Age of Reptiles.
 It began 248 million years ago and ended 65
million years ago.
 Dinosaurs, birds, flowering plants, and first
mammals appeared.



•
The Cenozoic era began 65 million years ago
and continues today.
Placental mammals and monotremes
evolved and diversified.
Anatomically modern humans appeared late in the era.
The origin of life remains a
puzzle……
 Scientists
do agree on two things:
› 1. Earth is billions of years old.
› 2. The conditions of the early planet
and its atmosphere were very
different from those of today.
Solar system was formed by a
condensing nebula (cloud of gas and
dust in space).
 About 4.6 billion years ago, sun formed
from a nebula, material in the nebula
pulled together due to gravity, and the
material that was in that disk circled the
sun.






Miller-Urey Experiment
The input of energy from lightning led to the
formation of organic molecules from inorganic
molecules present in the atmosphere.
They demonstrated that organic compounds
could be made by passing an electrical current,
to simulate lightning, through a mixture of gases.
Gases= methane, ammonia, hydrogen, and
water.
The experiment produced a variety of organic
compounds, such as amino acids- the building
blocks of proteins.
Meteorite that fell near Murchison,
Australia in 1969, revealed that organic
molecules are present in space.
 More than 90 amino acids were
identified, 19 are found on Earth.
 Many were made in Miller- Urey’s
experiment.


Iron Sulfide Bubbles
hypothesis: 1990’s,
hydrothermal vents
produce sulfur that
mixes with ocean
water to make
compartments of
rock. The vents may
have created
conditions conducive
for early life.
RNA was the genetic information that
stored information in living things on early
Earth.
 Ribozymes= RNA molecules that can
catalyze specific chemical reactions.
 RNA can copy itself, chop itself into
pieces, and make more RNA from those
pieces.
 DNA NEEDS enzymes to replicate itself.

› No nucleus or membrane bound organelles
› DNA is suspended in the cytoplasm and circular
› Single celled
› Cell Walls
› Evolved 3.5 bya

› Ex- Bacteria or Archaea
Divided into groups based on their need for oxygen:
› Obligate anaerobes- cannot survive in the
presence of oxygen.
› Obligate aerobe- needs oxygen to survive
› Facultative aerobe- can survive whether or not
oxygen is present.
Evolved more than 3.5 billion years ago
 Marine
 Blue-green algae that can carry out
photosynthesis (make its own food from
sunlight)
 Single prokaryotic cell
 Some live in colonies called stromatolites,
which are domed, rocky structures made
of layers of sediment and cyanobacteria.


We are made up of Eukaryotic cells, so
what are they?
› Has a nucleus with membrane bound
›
›
›
›
›
organelles
Nucleus store the genetic material and
is linear
Multicellular or unicellular
Larger, more complex
Plants and animals are examples
Evolved 1.5 mya




The origin of eukaryotic cells from
prokaryotic ancestors.
Defined as: relationship in which one
organism lives within the body of another,
and both benefit from the relationship.
The first eukaryotic cell came from a large
prokaryote engulfing a smaller prokaryote.
https://www.youtube.com/watch?v=FQmAnmLZtE






First prokaryotes and eukaryotes could only
reproduce asexually.
Sexual reproduction increases genetic diversity.
Allows new combination of genes to come
together.
May mask harmful mutations and may also bring
beneficial mutations together.
Increase in the rate of evolution by natural
selection.
May be the first step in the evolution of
multicellular organisms.
Paleozoic:
Began in the ocean
-Life moved onto land
- 542 million years ago
- Multicellular organisms first
appeared.
- Ended 251 million years
ago with a mass extinction:
90% of marine animal
species and 70% of land
animal species.
- In-between these events,
multicellular organisms
radiated.
- Cambrian Explosion: huge
diversity of animal species
evolved. In the middle life
moved to land.
-Jawless fishes, trilobites,
amphibians,
Mesozoic
Cenozoic
-Began 251 million years ago
and ended 65 million years
ago.
- Age of Reptiles
- Dinosaurs, birds, flowering
plants
- Three periods: Triassic,
Jurassic, and Cretaceous.
- First mammals also evolved
- Ichthyosaurs dominated
the water- marine reptile
- Marsupial mammals arose
- MASSIVE mass extinction.
- Most accepted hypothesis
is that an asteroid hit the
Earth and sent enormous
amounts of dust and debris
into the atmosphere,
-Began 65 mya and
continues today.
- Two periods: Tertiary (61-1.8
mya) and Quaternary (1.8
mya to current).
- Placental mammals and
monotremes evolved.
- Birds, ray finned fishes, and
flowering plants radiated.
- Modern humans appeared
200,000 years ago.
Define: Category of mammals with
flexible hands and feet, forward looking
eyes (three dimensional vision),and
enlarged brains.
 Arms that rotate in a circle
 Thumbs that can move against the
fingers
 Lemurs, monkeys, apes, and humans


Prosimians: oldest living
primate group, and most
are small and active at
night.
› Ex- Tarsiers-changed little in
40 million years.
› Ex- Lemurs
› Ex- Lorises
I’m a living
fossil
Humanlike primates and are
divided into New World
monkeys, Old World
monkeys, and hominoids.
 New World monkeys: all live
in trees, prehensile tail that
allows them to hang and
eat at the same time.

Travel and forage
on the ground as
well as spend time
in trees.
 Larger brains than
New World
monkeys
 Great ability to
manipulate
objects.

Walk upright
 Long lower limbs
 Thumbs that oppose
 Large brains

Walking upright requires change in
skeletal anatomy.
 Changes are found in intermediate
fossils.
 Bipedal= walk on two legs
 Advantages: higher reach when
foraging, frees the hands for carrying
food, infants, using tools, and foraging.
