Topic 6: Evolution

Topic Six: Evolution
Variation in Stickleback

5.1 Evidence for Evolution
Essential idea: There is overwhelming evidence
for the evolution of life on Earth.

Understandings
Statement Guidance
5.1 U.1 Evolution occurs when heritable characteristics of a species change.
5.1 U.2 The fossil record provides evidence for evolution.
5.1 U.3 Selective breeding of domesticated animals shows that artificial
selection can cause evolution.
5.1 U.4 Evolution of homologous structures by adaptive radiation explains
similarities in structure when there are differences in function.
5.1 U.5 Populations of a species can gradually diverge into separate species
by evolution.
5.1 U.6 Continuous variation across the geographical range of related
populations matches the concept of gradual divergence.

Applications and Skills
Statement Guidance
5.1 A.1 Development of melanistic insects in polluted areas.
5.1 A.2 Comparison of the pentadactyl limb of mammals, birds, amphibians
and reptiles with different methods of locomotion.

Evolution is the accumulated inherited changes in
a population over time
Evolution is one of the most powerful unifying
concepts in science and is a critical
underpinning to modern biology. It has been
stated that without evolution biology, biology
makes no sense.
Dobzhansky, 1973
5.1 U.1 Evolution occurs when heritable characteristics of a
species change.

What "theory" means in ordinary speech:
The term "theory" means a very different thing when used in everyday conversation
and in science. In our day to day speech, we often use "theory" to mean a guess or
unsubstantiated idea about how something works (as in "I have a theory that gremlins
are hiding my car keys").
In science, we would call such a guess a hypothesis, not a theory. A hypothesis is a
proposed explanation for an observation. In this case, I am proposing that the
explanation for why I can't find my car keys is that gremlins are hiding them.*

But the Fossil record…
OBSERVATION

Evidence supporting evolution
I. Fossil record
• transition species
II. Anatomical record
• homologous & vestigial structures
• embryology & development
III. Biogeography (Contential Drift)
IV. Molecular record (Neo-Darwinsim)
• protein & DNA sequence
species change.

• Fossil is the naturally preserved remains or traces of animals
or plants that lived in the past. There are two main types of
fossils; body and trace. Body fossils include the remains of
organisms that were once living and trace fossils are the
signs that organisms were present (i.e. footprints, tracks,
trails, and burrows).
Trace Fossil Body fossils

Fossil
Preservation
• Petrified
• Prints and molds
• Resins which turn to Amber
• Tar
• Peat which is acidic preventing
decay
• Frozen in Ice or Snow
• Sediments which turn to rock

Mount Everest
29,002 ft above sea level

Hillary’s Step
Fossilized
sea shells located
just a few feet
away from the
top of the world

Fossil Record
• Sedimentary rock is laid down
over time… new on top, older
rocks below
• As one digs down, find related
fossils, which are progressively
older as one digs deeper
• Consistent and steady increases
in size/complexity of structures
or the whole organism, or just
the opposite, are seen in
successive stratigraphic layers
Oldest
Youngest

• Layers of sedimentary rock contain fossils
– new layers cover older ones, creating a record over time
– fossils within layers show that a succession of
organisms have populated Earth throughout a long
period of time

The fossil record provides the dimension of time to the study of
evolution – the layer of rock in which a fossil is found can be dated and
therefore used to deduce the age of the fossil.
http://sciencelearn.org.nz/Contexts/Dating-the-Past/Sci-Media/Images/Fossils-in-sedimentary-rock

http://sciencelearn.org.nz/Contexts/Dating-the-Past/Sci-Media/Images/Fossils-in-sedimentary-rock
There are gaps in the fossil record due to:
• Special circumstances are required for fossilization to occur
• Only hard parts of an organism are preserved
• Fossils can be damaged so that only fragments remain to be discovered
The fossil record is the sum of all
discovered and undiscovered fossils
and their relative placement in rock.

Radioactive Dating
• Unstable atomic isotopes that decay
over time. Organisms incorporate
these isotopes in their bodies. This
can be detected and used to
radioactive dating a fossil, because
radioactive decay follows a
predictable exponential decay with
time.
Half-life is the period of time it
takes for a substance undergoing
decay to decrease by half. Example
below

• For instance, organisms take
up C, both as 14C and 12C but
the 14C decays away, so that
one can determine how old
the fossil is by the ratio of 14C
to 12C in the fossil. The older it
is, the greater the relative
quantity of 12C vs. 14C.
Then, as with 14C
dating, the age in half
lives can be deduced
from the decay curve
Half life of 14C is 5730
years, so it is useful for
dating samples that are
between 1000 &
100,000 years old

Potassium-Argon dating
• Proportions of parent 40K atoms and daughter 40Ar atoms are
measured
• Half-life of 40K is 1250 million years so it is very useful for dating
samples older than 100,000 years old.

5.1 U.3 Selective breeding of domesticated animals shows that
artificial selection can cause evolution.
https://phaven-prod.s3.amazonaws.com/files/image_part/asset/954254/z9zJXMj-QvJF-
DjAAnbdUsdnL2I/large_Brassica_oleracea_cauliflower_broccoli_etc_DP347.jpg
Selective breeding is the process by which humans use animal breeding and plant
breeding to selectively develop particular phenotypic traits (characteristics) by choosing which
typically animal or plant males and females will sexually reproduce and have offspring together.

Artificial selection Wild Mustard Plant
http://www.evolutionevidenc
e.org/wp-
content/uploads/2013/08/mu
stardselection1.jpg
http://upload.wikimedia.org/wikipedia/commons/2/2f/Wi
ld_Mustard.jpg

Selective breeding

species change.
The raw genetic material producing
wings, feathers and beaks, (variation)
is hidden in each of them.
http://upload.wikimedia.org/wikipedia/commons/9/90/Rock_Dove_
(Feral_Pigeon)_(Columba_livia)_-_geograph.org.uk_-_1309587.jpg

species change.
http://4.bp.blogspot.com/-
6EXGifOabDY/T75wOIZARKI/AAAAAAAAEkk/OSmkn
25kUhE/s1600/darwin-finches.jpg

species change.
At 9:03

The Galapagos
Islands created
diverse
environments due to
the different ages of
the islands. Coastal
areas and higher
elevations also show
a large temperature
and precipitation
difference.
species change.
Various ages of the island of the Galapagos *

Organism respond to changing environmental conditions, these
responses lead to new species.
Example of varied conditions: Hawaiian island and the violets (Viola)
– Nine taxa, seven species distributed over most islands
– Species occupy several different habitats across six main islands
• Dry forest
• Dry cliff
• Stream bank
• Swamp (cloud) forest
• Open bog
– Species growing in same habitat on different islands are almost
identical morphologically, anatomically
5.1 U.5 Populations of a species can gradually diverge into separate
species by evolution.

Some Viola species on Kauai
Viola tracheliifolia
(treelet, dry forest)
Viola wailenalenae
(shrub, swamp)
Viola kauaiensis
(herb, open bog)

Ages of the Hawaiian Islands
Kauai = 5.1 my
Hawaii =
400,000-180,000 my
Maui Nui complex =
1.9 my-800,000 y
Oahu = 3.7-2.6 my
The different ages of the island lead to different environments over time

Topography of Kauai
Waimea Canyon
(extremely arid)
Alakai Swamp/Mt Waialeale
(wettest place on earth)
Sandy or rocky
Coastal sites
Low-elevation
Moist forest
High-elevation
wet forest, cliffs

5.1 U.6 Continuous variation across the geographical range of related
populations matches the concept of gradual divergence.
• Geographic variation is the term used to refer to differences between populations, in
phenotype associated with local environment conditions (temp., precipitation, altitude
latitude…)
• Understanding how initial population size, gene flow, mutation frequency, and
environmental (abiotic) factors give rise to and maintain geographical variation can shed
light on direction and rate of evolutionary change.
• For instance, yarrow plants vary with geographical location across the Sierra Nevada

Comparative Anatomy
• Homologous structures
• Analogous structures
– Convergent evolution
– Parallel Evolution
• Vestigial Organs
• Embryology
5.1 A.2 Comparison of the pentadactyl limb of mammals, birds,
amphibians and reptiles with different methods of locomotion.

Homologous structures (Pentadactly limb)
similarities in characteristics resulting from common ancestry
Divergent Evolution

Homologous structures
• Similar structure
• Similar development
• Different functions
• Evidence of close evolutionary
relationship
– recent common ancestor

Vestigial Structures *
• describes a characteristic of organisms that
have seemingly lost all or most of its original
function through evolution.
• Fossil record supports the hypothesis that
whales are derived from ancient vertebrates
• Vestigial hind limbs are present in modern
whales internal bones. Vestigial limbs are
found in many animals, including the python.

Embryology*
• Similar features seen in developmental stages of related organisms
• Gill pouches and tails seen in developing vertebrates
• They have a common ancestor

5.1 A.1 Development of melanistic insects in
polluted areas.
http://upload.wikimedia.org/wikipedia/commons/
http://en.wikipedia.org/wiki/Peppered_moth_evolution
#mediaviewer/File:Biston.betularia.f.carbonaria.7209.jp
g
Example of evolution taking place
• The peppered moth…. Two forms
(morphs) the gray mottled form and the
dark form. Changes in relative numbers
was hypothesized to be the result of
selective predation by birds. High
industrial pollution make the darker
moth less likely to be seen.
• Melanin gives color to moths
Black is a mutation of the white form
(morphs), it is dominant.
With industrial pollution the black allele
became favorable. Increase in
population of the dominant allele.
Clean air, return of lichen , increase in
recessive allele. *

5.1 A.1 Development of melanistic insects in
polluted areas.
http://upload.wikimedia.org/wikipedia/commons/b/b7/Lichte_en_zwarte_versie_berkenspanner.jpg

Essential idea: The diversity of life has evolved and
continues to evolve by natural selection.
5.2 Natural Selection
https://s-media-cache-ak0.pinimg.com/736x/51/3d/86/513d86a093998ac870e98e052dde0ed3.jpg

Understandings
Statement Guidance
5.2 U.1 Natural selection can only occur if there is variation among members
of the same species.
5.2 U.2 Mutation, meiosis and sexual reproduction cause variation between
individuals in a species
5.2 U.3 Adaptations are characteristics that make an individual suited to its
environment and way of life.
5.2 U.4 Species tend to produce more offspring than the environment can
support.
5.2 U.5 Individuals that are better adapted tend to survive and produce more
offspring while the less well adapted tend to die or produce fewer
offspring
5.2 U.6 Individuals that reproduce pass on characteristics to their offspring.
[Students should be clear that characteristics acquired during the
lifetime of an individual are not heritable. The term Lamarckism is not
required.]
5.2 U.7 Natural selection increases the frequency of characteristics that make
individuals better adapted and decreases the frequency of other
characteristics leading to changes within the species.

Statement Guidance
5.2 A.1 Changes in beaks of finches on Daphne Major.
5.2 A.2 Evolution of antibiotic resistance in bacteria.

Mechanism for Evolution
Natural Selection The ultimate goal of any
population is that it must produce the next
generation. This is complicated by four basic
characteristics of life:
1. Variation among individuals means they individually have
different ability to obtain resources. Sexual reproduction promotes
variation in a species.
2. Reproduction Individuals that survive and then reproduce
transmit these variations to their offspring.
*The environment is the agent of natural selection determining
which species will survive.
3. Overpopulation Each generation produces more offspring then
the environment can support.
4. Competition with finite resources along with an increase in the
population there is a competition of those resources leading, a
survival of the fittest

5.2 U.1 Natural selection can only occur if there is
variation among members of the same species.
Variation among individuals means they individually have different ability to
obtain resources. Sexual reproduction (along with mutations in the sex cells)
promotes variation in a species.
http://upload.wikimedia.org/wikipedia/commons/thumb/5/53/Theba_geminata_variability.jpg/1280px-Theba_geminata_variability.jpg

1. Frequency of Genes (Genetic Variation)
• Inheritable differences among
individuals
• Raw material of evolution
• Happens in 3 ways
A. Mutations
B. Recombination
(meiosis)
C. Fertilization
5.2 U.2 Mutation, meiosis and sexual reproduction
cause variation between individuals in a species.
http://media-2.web.britannica.com/eb-media/70/81270-004-3B7A77F2.jpg

A. Mutations
• Permanent change in genetic variation
• Only source of new alleles
• Do not arise out of need
• Causes of mutation
– Spontaneous occurrence
– Radiation
– Chemicals
– Transposons (DNA sequence that can change its position)
http://www.britannica.com/EBchecked/topic/376514/Merychippus

Results of Mutations
• Harmful
Non-adaptive
Eliminated by selection
• Beneficial
Adaptive
Selected and persist
• Neutral
Neither adaptive nor non-
adaptive
May or may not persist in gene
pool
http://4.bp.blogspot.com/--
zKT77cA4Rc/URACaqRE7kI/AAAAAAAAAFI/ZktOQD8BRk
Y/s1600/horse_evolution.gif

Example of a gene mutation: phenylketonuria (PKU)
• C to T base-substitution mutation results in wrong amino acid
(similar to sickle-cell mutation)
• Individuals can not metabolize amino acid phenylalanine an
enzyme needed to degrade phenylalanine is not made so it
accumulates in the brain and causes developmental disabilities.

Example of a chromosomal mutation:
Klinefelter’s syndrome:
• receipt of an extra ‘X’ chromosome by males-> result is
feminization of secondary sex characteristics, sterility and learning
impairment may be present.
• Chromosomal mutations tend to have less evolutionary
significance because they typically cause death or sterility and will
not be passed on.

B. Recombination
• Major source of genetic variation
• Three processes
Segregation: Each pair of chromosome separates independently
Random assortment (metaphase I): The random distribution of
maternal and paternal homologues of about 8 million possibilities
Crossing over (Prophase I): About 20,000 genes each with a potential to
exchange information with a homologous pair

C. Fertilization: the resulting zygote can have one of 64
trillion possible diploid combinations (without considering
variations from crossing over!)

5.2 U.3 Adaptations are characteristics that make an
individual suited to its environment and way of life.
• Where and how an organism lives is
largely due to its specific adaptations
that allow it to survive and reproduce in
a particular area or habitat
• In other words their structure allows
them to function in that environment
• Polar bears are well adapted to life in the
Arctic. They have a large layer of blubber
to keep them warm. They are strong
swimmers, aided by their strong forearms
and layer of blubber for buoyancy. They
have hollow fur to aid in insulation as
well. For plants, cacti have water storage
tissue and spines (prevent water loss)
because of the infrequent rainfall in the
desert.
• Adaptations develop over time through
natural selection

Millions of years of reproductive changes have
taken place in order for the polar bear to exist

Polar Bears diverge from Brown Bear, its closest relative
between 600,000 and 5 million years ago.

• In the winter, temperatures in the Arctic are usually around -29 degrees
and can reach as low as -92 F. *

Animals have: Structural Adaptations
Definition: Actual body parts or coloration that help an organism survive in
their environment.
EX: camouflage, mimicry, bent hind legs, sharp teeth and claws, body
structures.

Animals have: Behavioral Adaptations
• Definition: Ways an organism act to help them survive in their
environment.
• EX: Migration, hibernation, warning calls, mating dances,
hunting in packs.
5.2 U.3 Adaptations are characteristics that make an individual suited
to its environment and way of life.

PLANT ADAPTATIONS
All living things adapt is a characteristic of life. All 6 kingdoms adapt. Animals
are not the only organisms to adapt.
Structural Plant Adaptations
1. Structures - adaptations on the body:
2. Seeds – all seeds have adaptation to better enable it to survive long
enough to plant itself and grow.
holdfasts, empty space for water storage, catch animals for minerals,
tallness, heartiness, thorns, flexibility, floatation devices
3. Protection – thorns, bad taste, poison, coloration, spikes
4. Obtaining Food – All plants do photosynthesis and make glucose in their
leaves. The larger the leaves the more Sun they can capture.

Structural Adaptations
Adaptations for reproduction
– Sweet fruit attracts animals that spread seeds far away.
– Some seeds are shaped to catch the wind.
– Brightly colored flowers with nectar attract pollinators such as
birds, bees and insects

Behavioral Adaptations
Adaptations to get food
– Plants lean or grow towards the sun.
– Roots grow down into soil.
– Vines climb up trees to catch sunlight.
– Plants like the Venus fly trap, trap insects for food.

Structural Adaptations
• Adaptations for defense
– Spines and thorns protect plants from predators
– Poison Ivy and Poison oak have toxins that give predators a
painful itchy rash.

5.2 U.4 Species tend to produce more offspring
than the environment can support.
http://evolutionbyfl.weebly.com/uploads/3/9/7/9/39791607/5832564_orig.jpg
• Prey populations tend to
produce more offspring than
the environment could
support as a survival strategy.
For example, fish produce
thousands of eggs but only
few make it to adulthood.
• Because of a limited amount
of resources creates
competition within a
population for food, water,
space and a mate. For
example: Male Peacocks grow
long tails to attract a mate,
even at the expense of a lose
of speed, making them much
easier prey for a loin.

For example: Male Peacocks grow long tails to attract a
mate, even at the expense of a lose of speed, making them
much easier prey for a loin. *

5.2 U.4 Species tend to produce more offspring
than the environment can support.

5.2 U.5 Individuals that are better adapted tend to survive
and produce more offspring while the less well adapted tend
to die or produce fewer offspring.
• Within a population, there is
genetic variation between the
individuals in the population.
• The organisms with the
beneficial characteristics will
be able to out-compete the
other individuals with the less
beneficial or harmful genetic
traits for limited resources and
mates.
• These individuals will survive
and reproduce and pass these
genetic traits onto the next
generation of offspring.
• Organisms with less desirable
traits will die or produce less
offspring

LaMarck
• Organisms adapted to their
environments by acquiring traits
– change in their life time
• Disuse
organisms lost parts because they did not use them — like the
missing eyes & digestive system of the tapeworm
• Perfection with Use & Need
the constant use of an organ leads that organ to increase in size —
like the muscles of a blacksmith or the large ears of a night-flying
bat
– transmit acquired characteristics to next generation
Modern Theory: Mechanism for Evolution
[Students should be clear that characteristics acquired during the lifetime
of an individual are not heritable. The term Lamarckism is not required.]

[Students should be clear that characteristics acquired during the lifetime
of an individual are not heritable. The term Lamarckism is not required.]

Distribution of genes (population genetics)
•is the study of genetic variability in a population
*Extension of Mendelian genetics
•Populations are individuals of the same species that live in
the same locations
Exhibit variation in traits
•Examination of the assemblage of traits reveals genetic
information and shows the kind and proportion of alleles in a
population
5.2 U.7 Natural selection increases the frequency of characteristics
that make individuals better adapted and decreases the frequency of
other characteristics leading to changes within the species.

Changing Allele Frequencies
1. Mutation – introduces new alleles into population
2. Natural Selection – specific alleles are more likely to be
passed down because they are somehow advantageous
3. Random Mating – individuals of one genotype mating with
individuals of a different genotype
– Think of an example of this happening?
4. Migration – individuals with specific genotypes move in or
out of a population
5. Genetic Drift – random changes in allele frequencies
– Caused by random sampling of specific genotypes
– Often seen in small, isolated populations
Can you think of why?
– Nothing to do with natural selection

Alleles and Population Genetics
• Although individuals are affected by the process of natural
selection, it is the makeup of the population that is critical for
determining the subsequent generations
• Changes in the gene pool refer to changes in the frequency of
the alleles
• If the allele frequencies in a population do not undergo change
over time, we say that the population is in genetic equilibrium
5.2 U.7 Natural selection increases the frequency of characteristics
that make individuals better adapted and decreases the frequency of
other characteristics leading to changes within the species.

Finch? Sparrow?
Woodpecker? Warbler?
Darwin collected 13
different types of
birds on the
Galapagos Islands,
thinking they were
unrelated species.
But after closer study…

Darwin was amazed
to find out:
All 13 species of
birds were finches…
But there is only one
species of finch on
the mainland?
Why?
Different food
sources without
competition
Large Ground
Finch
Small Ground
Finch
Warbler Finch Veg. Tree Finch

Correlation of species to food source

Correlation of species to food source
Seed
eaters
Flower
eaters
Insect
eaters

Changes on the island story *
https://whyevolutionistrue.files.wordpress.com/2014/08/05jpessa1-master675.jpg

Medium ground finch (to the right in the previous diagram) : Evolution in action
• endemic to the Galapagos Islands
• habitats are arid lowland forests and shrubland.
• generally feeds on seeds, but will also feed on insects and the fruit of cacti.

Deduce the results
from the graphs
1st Environmental change:
1974 to 1977 drought (La
Niña) conditions were
experienced on Daphne Major
as a consequence there was a
shortage in smaller sized seeds
2nd Environmental change:
1983 heavy and frequent rains
(El Niño event) were
experienced on Daphne Major as
a consequence there was an
abundance of smaller sized seeds

• Antibiotics kill bacteria directly or weaken the
bacteria by interfering with there metabolic
process, so your immune system can fight and
destroy the invading pathogen.
• Some bacteria might not die because of
changes within their DNA. These changes could
be caused by mutations within their genome or
the transfer of an antibiotic resistant gene from
another bacterium.
• Resistance is more likely to occur if the proper
amounts of antibiotics aren’t taken or if a
patient doesn’t finish the prescription.
• These resistant bacteria will survive and
reproduce, creating more identical resistant
bacteria.
• These resistant bacteria will make the person
sick again in the future.
• However if given the same antibiotic, these
bacteria will no longer be destroyed.
• Another antibiotic can be prescribed to kill these
new resistant bacteria.
• Resistance can be passed onto other pathogenic
bacteria, creating more species of resistant
bacteria.

Antibiotic resistance story*

5.3 Classification of biodiversity
• Essential idea: Species are named and classified using an
internationally agreed system.

Understandings
Statement Guidance
5.3 U.1 The binomial system of names for species is universal
among biologists and has been agreed and developed
at a series of congresses.
5.3 U.2 When species are discovered they are given scientific
names using the binomial system.
5.3 U.3 Taxonomists classify species using a hierarchy of taxa.
5.3 U.4 All organisms are classified into three domains. Archaea, eubacteria and eukaryote should be used
for the three domains. Members of these domains
should be referred to as archaeans, bacteria and
eukaryotes. Viruses are not classified as living
organisms.
5.3 U.5 The principal taxa for classifying eukaryotes are
kingdom, phylum, class, order, family, genus and
species.
5.3 U.6 In a natural classification, the genus and accompanying
higher taxa consist of all the species that have evolved
from one common ancestral species.
5.3 U.7 Taxonomists sometimes reclassify groups of species
when new evidence shows that a previous taxon
contains species that have evolved from different
ancestral species.
5.3 U.8 Natural classifications help in identification of species
and allow the prediction of characteristics shared by
species within a group.

Statement Guidance
5.3 A.1 Classification of one plant and one animal
species from domain to species level.
5.3 A.2 Recognition features of bryophyta, filicinophyta,
coniferophyta and angiospermophyta.
Students should know which plant phyla
have vascular tissue, but other internal
details are not required.
5.3 A.3 Recognition features of porifera, cnidaria,
platylhelmintha, annelida, mollusca, arthropoda
and chordata.
Recognition features expected for the
selected animal phyla are those that are
most useful in distinguishing the groups
from each other and full descriptions of the
characteristics of each phylum are not
needed.
5.3 A.4 Recognition of features of birds, mammals,
amphibians, reptiles and fish.
5.3 S.1 Construction of dichotomous keys for use in
identifying specimens.

• Formal two naming system of classifying
species.
• Originally developed by Swedish naturalist
Carolus Linnaeus considered the father of
taxonomy.
• Currently, many scientists and specialists
meet in a series of International
Congresses of Zoology which meet in
different cities every 4 years
• They meet to discuss their findings
regarding genetics, animal behavior and
classification
• A new species is considered one that can
interbred and produce offspring.
• A main topic is the binomial nomenclature
system and decisions regarding the
classification of new organisms or the
reclassification of old ones because of new
evidence regarding ancestry.
5.3 U.1 The binomial system of names for species is universal among
biologists and has been agreed and developed at a series of congresses.
http://iszscon2012.haifa.ac.il/
http://www.ibc2017.cn/index.html

The main objectives with regards to using the binomial nomenclature system
developed are to
1. Make sure each organism has a unique name that cannot be confused
with another organism (Example below)
2. The name can be universally understood regardless of the nationality or
culture that is using the name
3. Stability exists within the system by not allowing people to change the
name without valid scientific reasons
5.3 U.2 When species are discovered they are given scientific names using the
binomial system.

: the genus and species
2 Named Naming System
Rules:
1. Genus name begins
with the first letter of
the name capitalized.
2. Species name is lower
case.
3. Both names are Italics
4. Genus name may be
abbreviated once it has
been used in an article:
Example: A.maculatum
5.3 U.2 When species are discovered they are given scientific names using the
binomial system.
Binomial Nomenclature

5.3 U.3 Taxonomists classify species using a hierarchy of taxa 5.3

Dear
King
Philip
Come
Over
For
Good
Spaghetti
5.3 U.3 Taxonomists classify species using a hierarchy of taxa 5.3

5.3 U.4 All organisms are classified into three domains.
Domain
broadest category
of classification

Hierarchical
level
ACRONYM PLANT
Example:
ANIMAL
Example:
Most
diverse
Domain Dear Eukaryota Eukaryota
Kingdom King Plantae Animalia
Phylum Phillip Magnoliophyta Chordata
Class Came Magnoliopsida Mammalia
Order Over Malvales Primate
Family For Malvaceae Hominidae
Most
Specific
Genus Good Hibiscus. L Homo
species Spaghetti rosa sapiens
5.3 U.5 The principal taxa for classifying eukaryotes are kingdom,
phylum, class, order, family, genus and species.

http://commons.wikimedia.org/wiki/File:Masai_Woman.jpg
Domain Does Eukaryota Eukaryota
Kingdom Kennard Animalia Plantae
Phylum Play Chordata Magnoliophyta
Class Classical Mammalia Magnoliopsida
Order Or Primates Malvales
Family Folk Hominid Malvaceae
Genus Guitar Homo Hibiscus. L
Species Songs? Sapiens rosa
5.3 A.1 Classification of one plant and one animal species from domain to species level.
Learn a mnemonic, one animal example and one plant example:
http://commons.wikimedia.org/wiki/File:Ranunculus_macro.jpg
Dear
King
Philip
Come
Over
For
Good
Spaghetti

Plant Kingdom Diversity
The plant kingdom has within it 4 major groups:
• Bryophytes (mosses & liverworts)
• Filicinophytes (Ferns)
• Coniferophytes (Conifers & Pines)
• Angiospermophytes ( Flowering Plants)
5.3 A.2 Recognition features of bryophyta, filicinophyta, coniferophyta
and angiospermophyta.

1. Bryophytes 3. Coniferophytes
4. Angiosperms
2. Filicinophytes

Leaves, roots and stems Vascular
tissue
Reproductive structures
Bryophytes
(mosses, hornworts
and liverworts)
• No roots, but structures similar to
root hairs called rhizoids
• Mosses have simple leaves and
stems
• Liverworts have a flattened thallus
None Spores produced in
capsules, which develop
at the end of a stalk
Filicinophytes
(ferns)
• Roots present
• Short non-woody stems.
• Leaves usually divided into pairs of
leaflets
Yes Spores produced in
sporangia on the
underside of the leaves
Coniferophytes
(conifer shrubs and
trees)
• Roots, present
• Woody stems
• Leaves usually narrow with a thick
waxy cuticle
Yes Seeds develop from
ovules in female cones.
Male cones produce
pollen.
Angiospermophytes
(flowering plants)
• Leaves and roots variable in
structure
• Stems maybe woody (shrubs and
trees)
Yes Seeds develop from
ovules in ovaries, inside
flowers. Seeds are
dispersed by fruits which
develop from the
ovaries.

5.3 A.4 Recognition of features of birds, mammals, amphibians, reptiles
and fish.
The Vertebrata

5.3 A.4 Recognition of features of birds, mammals, amphibians, reptiles and fish.
Limbs Gas Exchange Reproduction Other features
Mammals 4 Pentadactyl
limbs
Lungs with
alveoli
• Internal fertilization
• Give birth to live young
• Mammary glands secrete
milk
• Hairs growing from the skin
• Teeth including living tissue
Birds 4 Pentadactyl
limbs, 2 limbs
modified as
wings
Lungs with
parabronchial
tubes
• Hard shells around the
eggs
• Feathers growing from skin
• Beak but no teeth
Reptiles 4 Pentadactyl
limbs
Lungs with
extensive
folding
• Soft shells around eggs
• Dry scaly impermeable skin
• Simple teeth – no living
tissue
Amphibians 4 Pentadactyl
limbs
Simple lungs
with small
internal folds
and moist
surfaces
• External fertilization in
water
• Protective jelly around
eggs
• Larval stage lives in water
• Soft moist permeable skin
Fish Fins Gills • External fertilization in
most species
• Scales grow from the skin
• with a single gill slit
• Swim bladder for buoyancy
A summary of key features that can be used to distinguish between the vertebrate
classes

5.3 A.3 Recognition features of porifera, cnidaria, platylhelmintha,
annelida, mollusca, arthropoda and chordata.
chordata
porifera
cnidaria platylhelmintha
annelida mollusca
arthropoda
http://commons.wikimedia.org/
What about other phyla? Can
you match the names with the
images?

Can you match the phyla with
the images?
chordata porifera
cnidaria
platylhelmintha
annelida
mollusca
arthropoda

The Invertebrates Phylum: Porifera (sponges)
https://bioelevenncuevas.wordpress.com/phylum-porifera/

The Invertebrates Phylum: Cnidaria

The Invertebrates Phylum:
Platyhelminthes (flatworms)

The Invertebrates Phylum: Annelida
(segment worms)

The Invertebrates Phylum: Mollusca
(Snails, slugs and octopus)

Phylum: Arthropoda (Insects, Crustaceans,
Spiders, Scorpions, Millipedes)
http://animals-pics.com/bird-eating-tarantula-size/33/go-back-gallery-for-goliath-bird-eating-spider-size-comparison/

Phylum: Chordata
https://animalterritory.wordpress.com/tag/wildlife/

5.3 A.3 Recognition features of porifera, cnidaria, platylhelmintha, annelida, mollusca, arthropoda
and chordata.
Symmetry Segmentation Digestive tract Other features
porifera
(sponges)
None None No mouth or anus • No body plan
• attached to rocks
• Filter feeder
cnidaria
(corals, jellyfish)
Radial None Mouth but no anus • Two layer body plan
• Stinging cells
• Tentacles
platylhelmintha
(flatworms)
Bilateral None Mouth but no anus • Three layer body plan
• Flattened body
annelida
(earthworms,
leeches)
Bilateral Very
segmented
Mouth and anus • Three layer body plan
• bristles often present
Mollusca
(oyster, snails,
octopus)
Bilateral Non-visible
segmentation
Mouth and anus • Three layer body plan
• Most have shell made of
CaCO3
Arthropoda
(ant, scorpion,
crab)
Bilateral Segmented Mouth and anus • Three layer body plan
• Exoskeleton
• jointed appendages
Chordata
(fish, birds,
mammals)
Bilateral Segmented Mouth and anus • Three layer body plan
• notochord
• hollow dorsal nerve cord
• (some have ) pharyngeal slits
A summary of key features that can be used to distinguish between animal phyla

5.3 U.8 Natural classifications help in identification of species and allow the
prediction of characteristics shared by species within a group.
If a new species of Ant is discovered
then scientists would predict that the
species should possess amongst other
characteristics six jointed legs, a head,
thorax, abdomen, elbowed antennae,
‘antibiotic’ secretory glands. If the species
does not match the expected set of
characteristics this brings into question
either the classification of the species or of
Ants as a family.
Natural classification groups together species that share a common
ancestor from which they evolved. This is called the Darwinian principle of
common descent
Dichotomous keys: can be used to help
identify the species. The keys can place a
specimen with the most closely related
species, genus, family or phyla using
natural classification. To what level of
classification a specimen can be placed
depends on how unique it is.

Natural classification is very helpful when dealing with
new species:
5.3 U.8 Natural classifications help in identification of species and allow the
prediction of characteristics shared by species within a group.

Chordata (animals with a
backbone) should be easy.
Try using the key to help
identify the rest of the
phyla.

5.3 U.6 In a natural classification, the genus and accompanying higher taxa consist of all
the species that have evolved from one common ancestral species.
.
• Homologous traits
are traits that are similar to
one another due to shared
ancestry. As species adapt to
their environments and evolve
over time, these traits may
change in appearance and in
function, but ultimately they
still share the structure,
genetics, or embryonic
structure of their common
ancestor
• Divergent evolution of structures
Show an evolutionary
relationship

5.3 U.7 Taxonomists sometimes reclassify groups of species when new evidence shows that a
previous taxon contains species that have evolved from different ancestral species.
• As new was to look at individual species
emerge re-classification of species continue
to occur.
Example: Sequencing of Modern humans
and Neanderthals mtDNA found a difference
in 202 bases. In contrast, the difference
between chimpanzees and modern humans is
approximately 1,462 mtDNA base pairs. In
addition, the genome of the modern human and
Neanderthal genomes are 99.7% are identical,
humans sharing around 98.8% of base pairs with
the chimpanzee. Neanderthals have contributed at
least 20 percent of their genomes to anatomically
modern humans.
Neanderthal

5.3 U.7 Taxonomists sometimes reclassify groups of species when new evidence shows that a
previous taxon contains species that have evolved from different ancestral species.
Example: In the 1980’s microbial Biologist Carl Woese proposed a radical
reorganization of the five kingdoms into three domains. It is now the standard
paradigm. This shift was based on new evidence (mitochondrial DNA).

5.4 Cladistics
Essential idea: The ancestry of groups of species can be
deduced by comparing their base or amino acid sequences.

Understandings
Statement Guidance
5.4 U.1 A clade is a group of organisms that have evolved from a common
ancestor.
5.4 U.2 Evidence for which species are part of a clade can be obtained from
the base sequences of a gene or the corresponding amino acid
sequence of a protein.
5.4 U.3 Sequence differences accumulate gradually so there is a positive
correlation between the number of differences between two species
and the time since they diverged from a common ancestor.
5.4 U.4 Traits can be analogous or homologous.
5.4 U.5 Cladograms are tree diagrams that show the most probable sequence
of divergence in clades.
5.4 U.6 Evidence from cladistics has shown that classifications of some groups
based on structure did not correspond with the evolutionary origins
of a group or species.

Statement Guidance
5.4 A.1 Cladograms including humans and other primates.
5.4 A.2 Reclassification of the figwort family using evidence from
cladistics.
5.4 S.1 Analysis of cladograms to deduce evolutionary relationships.

5.4 U.1 A Clade is a group of organisms that have evolved from a
common ancestor
• Cladistics (From the ancient
Greek for "branch") is a
method of classifying species
of organisms into groups
called clades, which consist
of an ancestor organism and
all its descendants (and
nothing else).

5.4 S.1 Analyze cladograms to deduce evolutionary relationships.
1
2
3
DCBA • Which two species are most
closely-related by evolution?
• Which node represents the earliest
speciation / divergence?
• Which species is D more closely
related to; A or B?
• The assumption is that these
changes occur at a regular rate.
(which may not always be the
case)
• Therefore if species A had 5
differences from species B and 10
differences from species C, then
the lineages for A and C must
have split twice as long ago as for
A and B

5.4 U.5 Cladograms are tree diagrams that show the most
probable sequence of divergence in clades.
• These two cladograms are identical (although they don’t look it)
• The shape and the order of the terminal nodes does not matter.
• The only information to be gathered from the cladograms below is the order of
nesting of sister clades and the relative relatedness of species
http://commons.wikimedia.org/wiki/File:Identical_cladograms.svg

common ancestor
http://upload.wikimedia.org/wikipedia/commons/6/6b/Lutjanus_kasmira_school.jpg

http://upload.wikimedia.org/wikipedia/commons/2/2b/Tiktaalik_roseae_life_restor.jpg
common ancestor
Tiktaalik
• Represents the evolutionary transition
from fish to amphibians. And as such the
common ancestor to every animal in the
Clade after the fish.

common ancestor
http://upload.wikimedia.org/wikipedia/commons/1/19/Caerulea3_crop.jpg

common ancestor
http://upload.wikimedia.org/wikipedia/commons/d/dc/Furcifer_pardalis_-Z%C3%BCrich_Zoo-8a.jpg

Archaeopteryx is a famous example transitional fossils – it gives evidence for the evolution of
birds from reptiles like dinosaurs. (Hyperlink: The Origin of Birds)
http://commons.wikimedia.org/wiki/File:Archaeopteryx_lithographica_%28Berlin_specimen%29.jpg
http://commons.wikimedia.org/wiki/File:Archaeopteryx_NT.jpg
Bird features:
• feathers
Dinosaur features include:
• jaws with sharp teeth
• three fingers with claws
• long bony tail
common ancestor

common ancestor
http://upload.wikimedia.org/wikipedia/commons/0/03/Mountain_Bluebird.jpg
Likewise, birds share the
common characteristics of
feathers
They too form a clade

Mammals have the unique homologous
characteristic of producing milk
They form a clade
common ancestor
http://images.nationalgeographic.com/wpf/media-
live/photos/000/334/cache/freshwater-mammals-hippo_33402_600x450.jpg

For example, Fish,
Amphibians, Reptiles,
Birds, Mammals, and
all descendants from
a common ancestor to
form a clade
common ancestor

Convergent Evolution Analogous structures
http://batslive.pwnet.org/
5.3 U.7 Taxonomists sometimes reclassify groups of species when new evidence shows
that a previous taxon contains species that have evolved from different ancestral
species. U.4 Traits can be analogous or homologous

Analogous structures
• Separate evolution of
structures
similar functions
similar external form
different internal
structure &
development
different origin
no evolutionary
relationship
Solving a similar problem with a similar solution
http://upload.wikimedia.org/wikipedia/commons/5/5c/Male_-
_black_phase_-_short_tail_hawk.JPG
http://www.redorbit.com/media/uploads/2004/1
0/40_03aa91083d476b07bcc9228e134d6c56.jpg
Convergent evolution

• Flight evolved in 3 separate
animal groups
– evolved similar “solution”
to similar “problems”
– analogous structures
http://upload.wikimedia.org/wikipedia/commons
/7/77/Big-eared-townsend-fledermaus.jpg

• Fish: aquatic vertebrates
• Humpback Whale: aquatic mammals
similar adaptations to life in the sea
not closely related

Morphology (or there outward appearance) is only
one part of the story in cladistics. DNA and the
amino acids they code for are the primary basis for
grouping organisms into clades and determining
likely paths of evolutionary descent
Ex: Crocodiles are more closely related to birds than lizards…
5.4 U.2 Evidence for which species are part of a clade can be
obtained from the base sequences of a gene or the
corresponding amino acid sequence of a protein.

All known organisms use
DNA as genetic material
The genetic code is
universal. Gene
sequences inserted in
different organisms
express the same proteins
5.4 U.2 Evidence for which species are part of a clade can be obtained
from the base sequences of a gene or the corresponding amino acid

The same 20 amino
acids are used to make
all proteins
http://commons.wikimedia.org/wiki/File:Protein_primary_structure.svg

Taking the example of the protein cytochrome c.
It is not identical in all species because single
point mutations in the DNA that codes for it can
lead to different amino acids making up the
protein.
When sequence the proteins of Mammals the
protein haemoglobin or cytochrome C are used.
Both humans and chimpanzees have identical
cytochrome c molecules, while rhesus monkeys
share all but one of the amino acids.
This suggests that humans and chimpanzees are
more closely related to each other than to rhesus
monkeys.
http://www.flickr.com/photos/stuffinhergoose/571672799
5.4 U.2 Evidence for which species are part of a clade can be obtained
from the base sequences of a gene or the corresponding amino acid
I didn’t want to be
closely related to
stinking humans
anyway!

Molecular biology
Protein and DNA Structures Reveal Associations Between
Organisms
• Nuclear DNA code is highly conserved across phyla – although there
are variations, there are no alternate codes
• Nuclear DNA can be used to show associations between organisms
when comparing very long suspected evolutionary times
• Ribosomal RNA and mitochondrial DNA & RNA more useful when
comparing shorter evolutionary times… they are inherently more
variable over time because they are subjected to fewer selection
pressures.
• Small changes are seen in the DNA code between closely related
species.
• Monkeys, apes, and humans clearly have common ancestry

Base Sequence Comparisons
• Divergence (difference) in
nucleotide base sequence
allows us to draw
relationships between
different organisms.
• Here, differences in
nucleotide base sequence
of humans and other
primates compared
• Chimps closest, spider
monkeys most dissimilar

Molecular Clocks
• DNA undergoes relatively
steady rates of mutation
over time
• More divergence in structure
is assumed to mean more
time has passed
• Changes in homologous DNA
from different species allows
biologists to construct
molecular clocks based on
the rates of change in known
and homologous DNA
• This can aid in the dating of
branching points in the
evolutionary record

http://www.studentsoftheworld.info/infopays/photos/PER/orig/lamas.jpg
5.4 U.6 Evidence from cladistics has shown that classification of some
groups based on structure did not correspond with the evolutionary
origins of a group or species.

http://www.scratchwireless.com/pad/wp-content/uploads/2015/02/SheepFlock.jpg

http://ianadamsphotography.com/news/wp-content/uploads/2014/12/Bactrian-Camels-the-Wilds.jpg

Evolutionary Links
Classification allows us to see evolutionary relationships. Organisms
that are grouped together share a lot of similar features (homologous
structures). These shared characteristics help us see how organisms
have evolved from a common ancestor. HOWEVER, morphology (or
there outward appearance) has its limitations in terms of evolutionary
classification and DNA/ Amino Acid evidence is now far more accurate
and trustworthy…
http://www.flickr.com/photos/doug88888/3458057235/http://www.flickr.com/photos/mrapplegate/2423991076/
e.g. Llamas were
originally compared to
sheep but a study of
their genetics later
placed them in the
camel family

• Morphology was used to classify
the Figworts. Until recently,
Figworts were the 8th largest
family of angiosperms (flowering
plants). It grew from 16 genera
in 1789 to 275 genera
• Flowers of plants in Figworts
tend to be pretty uniform in
their appearance, typically
having corollas with bilateral
symmetry
• Taxonomists recently examined
chloroplast genes and found the
5000 figwort species should be
split into 5 different clades
rather than just one.
5.4 A.1 Discuss reclassification of the figwort family using
evidence from cladistics.
http://www.jardinexotiqueroscoff.com/site/uploads/pictures/plante
/800x800/scrophulariaceae-diascia-rigescens-13.jpg

5.4 A.1 Discuss reclassification of the figwort family
using evidence from cladistics.
http://upload.wikimedia.org/wikipedia/commons/2/2e/2007_Hippuris_vulgaris.jpg
Hippuris vulgaris (out)

http://upload.wikimedia.org/wikipedia/commons/4/40/Castilleja_angustifolia_1.jpg
Applegate Indian paintbrush (out)

Snapdragon (out)

• Botanists in the 18th and 19th
centuries used plant taxonomy to
separate out groups.
• Now with the use of modern
techniques, less than half of the
original species remain in the
Figwort family; now only the 36th
largest among angiosperms
• Reclassification was helpful since
old Figwort family was too large
and dissimilar to be a helpful
grouping
• We should consider ourselves
fortunate to be a part of what is
one of the eras of greatest
advancement in the field it is a
tremendous age of discovery
No longer a
Figwort. Sad

5.4 U.7 Analyze cladograms including humans and other primates.
Gibbons
16.8 million years ago

Orangutan 13 million years ago

Gorilla 10 million
years ago

Bonobo 5 million years ago

Chimpanzee 5 Million years ago

https://en.wikipedia.org/wiki/Ape

This is part of a molecular phylogeny of all of the
living primates. It clearly shows chimpanzees (Pan)
as more closely related to humans than to gorillas.
It was made by comparing 34,927 base pairs
sequenced from 54 genes taken from each
of a single species in each genus.

Characters Sponge Jellyfish Flatworm Earth-
worm
Snail Fruit fly Starfish Human
Cells with flagella X X X X X X X X
Symmetry X X X X X X X
Bilateral symmetry X X X X X X
Mesoderm X X X X X
Head develops first X X X
Anus develops first X X
Segmented body X X
Calcified shell X
Chitinous Exoskeleton X
Water Vascular system X
Vertebrae X
Another Example:

Flagella
Mesoderm
Bilateral symmetry
Symmetry
Vertebrae
Anus develops first
Chitinous
shell
Head develops
first
Sponge StarfishFruit flySnail
Flat-
worm EarthwormJellyfish Human
Water
vascular
system
Calcified
shell
Segmented body

10.3 Gene Pools and Speciation
Essential idea: Gene pools change over time.

Understandings
Statement Guidance
10.3 U.1 A gene pool consists of all the genes
and their different alleles, present in
an interbreeding population.
10.3 U.2 Evolution requires that allele
frequencies change with time in
populations.
Punctuated equilibrium implies long
periods without appreciable change and
short periods of rapid evolution.
10.3 U.3 Reproductive isolation of populations
can be temporal, behavioral or
geographic.
10.3 U.4 Speciation due to divergence of
isolated populations can be gradual.
10.3 U.5 Speciation can occur abruptly.

Statement Utilization
10.3 A.1 Identifying examples of directional,
stabilizing and disruptive selection.
10.3 A.2 Speciation in the genus Alliumby
polyploidy.
Many crop species have been created to be
polyploid. Polyploidy increases allelic
diversity and permits novel phenotypes to
be generated. It also leads to hybrid vigor.
10.3 S.1 Comparison of allele frequencies of
geographically isolated
populations.

10.3 U.1 A gene pool consists of all the genes and their different
alleles, present in an interbreeding population
Speciation
• A species a group of individuals
who produce offspring after
mating. This make individual of
that species reproductively
isolated from other species.
• A gene pool is the set of all
genes, in an interbreeding
population.
http://data1.whicdn.com/images/63849/large.jpghttp://arkansasagnews.uark.edu/monarchs95.jpg

10.3 U.2 Evolution requires that allele frequencies change with
time in populations.
Changes in allele frequency: If the allele frequencies of a population
are not in equilibrium then the frequencies are changing or evolving. The
following processes facilitate evolution by either adding or removing
genetic variation from a population in response to changing conditions in
an area:
• Mutation
• Migration (Gene Flow)
• Genetic Drift
• Unequal Mating and/or Fertilization Success (Sexual Selection)
• Unequal Viability (Natural Selection)
Gene pool: The collection of genes in a population
Because diploids have only two versions of each gene, each has only a small
fraction of possible alleles in a population
Genotype: The genetic makeup of an individual at a given locus, taking into
account the two possible alleles
Genotype frequency is the proportion of a given genotype in the population
Allele frequency refers to the proportion of a particular allele, as an example
A or a
Phenotype: the traits of an individual
Phenotype frequency is the proportion of a given phenotype in the population
Phenotype frequency is influenced by the dominance characteristic of an allele

Frequencies add up to 1.0
e.g. — a population has two alleles, A and a with A is dominant over a
The allele frequencies must sum to 1.0
(frequency of A) + (frequency of a) = 1.0
The genotype frequencies must sum to 1.0
(frequency of AA) + (frequency of Aa) + (frequency of aa) = 1.0
The phenotype frequencies must sum to 1.0
(frequency of AA and Aa phenotype) + (frequency of aa phenotype) = 1.0
Imagine 2 alleles, A and a
p is the frequency of A q the frequency of a
So, p + q = 1
The mathematical equivalent of a random mating can be given by multiplying this
relationship by itself
Therefore, (p + q)2 = 1 = p2 + 2pq + q2
p2 = frequency of AA 2pq = frequency of Aa q2 = frequency of aa
Given this condition, we can always work out the frequencies of each allele in a sexual
population.

10.3 S.1 Comparison of allele frequencies of geographically
isolated populations
• Cod fish have a gene that codes for an
integral membrane protein called
pantophysin.
• Two alleles of the gene, PanIA and PanIB,
code for versions of pantophysin, that
differ by four amino acids in one region of
the protein.
• Samples were collected from 23 locations
in the North Atlantic (numbered 1–23 in
each pie chart), on the map to the right.
• The frequency of an allele can vary from
0.0 to 1.0.
PanIA light grey sectors of the pie charts show
the allele frequency for the PanIA gene
PanIB black sectors show the allele frequency
for the PanIB gene.
• The biggest difference in allele frequency
occurs in the Cod fish isolated at the two
extremes of the map.

10.3 U.3 Reproductive isolation of populations can be temporal,
behavioral or geographic.
• Reproductive isolation of populations occurs when barriers or
mechanisms prevent two populations from interbreeding, keeping
their gene pools isolated from each other.
• There are different types of reproductive isolation including temporal,
behavioral, and geographic

How and why do new species originate?
• Species are created by a series of
evolutionary processes
– populations become isolated
• geographically isolated
• reproductively isolated
– isolated populations
evolve independently
• Isolation
– allopatric
• geographic separation
– sympatric
• still live in same area

Temporal isolation
• Species that breed during different
times of day, different seasons, or
different years cannot mix gametes
– reproductive isolation
– sympatric speciation
• “same country”
Eastern Spotted Skunk (Top Right)
& Western Spotted Skunk (Bottom
Right) overlap in range but Eastern
mates in late winter & Western
mates in late summer
http://upload.wikimedia.org/wikipedia/
commons/f/f2/Spilogale_putorius_(2).jp
g
http://upload.wikimedia.org/wikipe
dia/commons/9/98/Spilogale_gracil
is_amphiala.jpg

Behavioral Isolation
• In most animal species, members of the two sexes must first search for each other
and come together.
• Unique behavioral patterns & rituals isolate species
 identifies members of species attract mates of same species
 courtship rituals, mating calls
 reproductive isolation
Blue footed boobies mate
only after a courtship display
unique to their specieshttp://upload.wikimedia.org/wikipedia/commo
ns/a/aa/Bluefooted_Booby_Comparison.jpg

So…what is a species?
Western MeadowlarkEastern Meadowlark
Distinct species:
songs & behaviors are different
enough to prevent interbreeding

Geographic Isolation
Species occur in different areas
– physical barrier
– allopatric speciation
• “other country”
Harris’s Antelope
Squirrel inhabits the
canyon’s south rim
(L). Just a few miles
away on the north
rim (R) lives the
closely related
White-tailed
Antelope Squirrel

10.3 A.1 Identifying examples of directional, stabilizing and disruptive
selection.
• If no selection occurs to a population (for
whatever means), population doesn’t
change with succeeding generations.
• If selection pressure is applied then those
not receiving selection pressure tend to
predominate…
 Stabilizing: the extremes are selected
against; center stays same and grows
in numbers
 Directional: one tail of the distribution
is selected against and the opposite
tail grows in numbers
 Disruptive: a mid-group is selected
against; the tails are allowed to
predominate and grow compared to
middle
As an example: in Humans we have
selected for a babies birth weight. This
protects the mother and the babies
health.

10.3 A.1 Identifying examples of directional, stabilizing and
disruptive selection.
Directional Selection:
• bird predation is the selective
pressure that removes
individuals from one end of a
phenotypic distribution and
thus causes a shift in the
distribution towards the other
end (in the cause of the
pepper moth a change in
dominate color).
• Over time, the favored
extreme will become more
common and the other
extreme will be less
common or lost.
Example: the Pepper Moth

Stabilizing Selection:
A type of selection pressure that
removes individuals from both ends of
a phenotypic distribution, thus
maintaining the same distribution
mean (selective pressure being the
mortally of birth mother and/or
baby). This occurs when natural
selection favors
the intermediate phenotypes. Over
time, the intermediate states become
more common and each extreme
variation will become less common or
lost. Same mouse example where
medium colored fur is favored over
dark or light fur color.
Example: Birth weight for new born
human average 7 pounds

Disruptive Selection:
• Removes individuals from the center
of a phenotype. This occurs when
natural selection favors both ends of
the phenotypic variation (Selective
pressure can be caused by a change
in precipitation/drought).
• Over time, the two extreme
variations will become more
common and the intermediate
states will be less common or lost.
• This can lead to two new species.
Example: The shift in beak shape in
Finches the Grant’s study on the
Galapagos islands

10.4 U.4 Speciation due to divergence of isolated populations can
be gradual.
• Speciation can occur gradually over long periods of time, with several
intermediate forms in between species leading to today’s current species.
This can be seen in some of the more complete fossil records, like the whale
or the horse.
• In some species, large gaps were evident for certain species in the fossil
record. This imperfections in the fossil record, maybe the result of
transitional species have not been discovered yet or abrupt speciation. Hyperlink
http://www.sivatherium.narod.ru/library/Dixon/pics_01/p0010_e.gif

Gradualism
• Gradual divergence over long
spans of time
– assume that big changes occur
as the accumulation of many
small ones
10.4 U.4 Speciation due to divergence of isolated populations can
be gradual.
http://cnx.org/resources/22b17901c8ce6510b03e2f89df0bc072/graphics1.png

Abrupt (Punctuated Equilibrium)
Species remain stable for long
periods of time (several million
years) interrupted by periods of
significant change, during which
time a new species may evolve.
 rapid bursts of change
 long periods of little or no
change
 species undergo rapid
change when they 1st bud
from parent population

http://static.skynetblogs.be/media/130852/12.11.jpg
Over 75% of all life on Earth was lost during the late
Devonian mass extinction which took place about 375-359
million years ago

https://evolutionliteracy.files.wordpress.com/2014/09/t
rilobites-evolution-literacy-g-paz-y-mino-c-photo.jpg
Over 97% of all life on Earth was lost during the
End-Permian mass extinction which took place 252
million years ago

http://www.gohobby.com/wp-
content/uploads/2012/11/Velociraptor-
Jurassic-Park.jpeg
Over 50% of all life on Earth was lost during the Triassic
mass extinction which took place 201 million years ago

https://evolutionliteracy.files.wordpress.com/2014/09/t
rilobites-evolution-literacy-g-paz-y-mino-c-photo.jpg
Over 80% of all life on Earth was lost during the end
Cretaceous. The mass extinction took place 65 million
years ago

Gradualism
Punctuated Equilibrium
If the rate of speciation in a group is equal to or greater than the rate of
extinction, the group will continue to exist. If the rate of extinction in a clade
is greater than the rate of speciation, the entire clade will eventually become
extinct.

10.3 A.2 Speciation in the genus Alliumby polyploidy.
• Polyploidy organisms contain more
than two pairs of the same
chromosomes.
• A likely advantage is it allows
for additional raw materials (i.e.
DNA, genes) for evolution. Every
gene is theoretically free to
evolve without substantial negative
effect.
• Polyploidy plants tend to be
larger. The reproductive organs and
fruit, in particular, are usually
enlarged in polyploidy. The likely
mechanism for this is simple: more
DNA results in a larger nucleus,
which results in larger cells,
especially in the reproductive
organs. http://www.vims.edu/newsandevents/top
stories/_images/diploid_triploid_250.jpg
Oysters

Normally different species cannot interbreed because they have different chromosome numbers
and cannot form diploid pairs (Polyploidy is more common in plants than in animals because
in animals sex determination mechanism involves number and type sex chromosomes) . Offspring
produced by such unions are typically sterile due to this uneven chromosome pairing
Example Species A:
• The centromere of the chromosome failed to separate (nondisjunction). The gametes of the
hybrid offspring will have paired chromosomes from that parent species.
• Species A’s gamete fuses with the gamete of a closely related species (Species B), think of
Loin/Tiger pairing to produce a Liger, a hybrid is created.
• If the hybrid interbreeds with a member of the other parent species (Species B), all
chromosomes from both parent species will be paired, the resulting offspring will now be
fertile and have the combined chromosome composition of both parental species
• Polypoid created.

• The genus Allium comprises monocot
flowering plants and includes the onion,
garlic, chives, scallion, shallot, and the leek.
• In many of these species of plants,
chromosome doubling has created a large
number of different phenotypes.
• This results is a number of reproductively
isolated but similar populations.
Examples: of this are seen in 5 natural
population
Diploid (2n) = ~ 16 chromosomes (e.g. Allium
cepa – garden onion)
Triploid (3n) = ~ 24 chromosomes
(e.g. Allium carinatum – keeled garlic)
Tetraploid (4n) = ~ 32 chromosomes
(e.g. Allium tuberosum – chinese chives)
Pentaploid (5n) = ~ 40 chromosomes
(e.g. Allium oleraceum – field garlic)
Octoploid (8n) = ~ 66 chromosomes
(e.g. Allium nutans – blue chives)
http://i.dailymail.co.uk/i/pix/2008/09/12/article-1054890-
029CF17900000578-854_233x364.jpg

Allium grayi tetraploid (2n=32)
tetraploid (2n=32)

pentaploid (2n=40)

http://upload.wikimedia.org/wikipedia/commons/7/79/Allium_tulipifolium_(inflorescence).jpg
hexaploid (2n=48)

Bibliography /
Acknowledgments
Jason de Nys

Topic 6: Evolution

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