Transcript speciation_2015

• What is a species?
– a species is a population of organisms that
can successfully interbreed but cannot breed
with other groups.
• How do we classify species?
– By a species morphology-internal and
external structure and appearance
• Why do we have different species?
• What causes different species?
Chapter 16 & 17
population genetics and speciation
• What causes variation within a population?
– Environmental factors (amount of food)
– Heredity
– Gene pool—total genetic information available
in a population
• Hardy-Weinberg is used to predict
phenotype frequency
– Phenotype frequency = # individuals w/ trait
total individuals in population
If 2 alleles for color
A = red, or pink
a = white
We want frequency of A or a
AA – red
Aa - pink
aa – white
To be red RR
so you have 2 “R”
To be pink Rr
you have 1 “R” and 1 “r”
To be white
you have 2 “r”
Above you have 12 “R” out of 18 possible
you have 4 “r” out of 18
12/16 = 0.75
4/16 = 0.25
Probability of RR = frequency of R x frequency of R
=
0.75
x
0.75
= 0.5625
(r x r)
(0.25 x 0.25 = 0.0625
Hardy- Weinberg
P2
+
2pq
q2 = 1
+
Frequency of RR
R x R
freq of Rr
Rxr
freq of rr
rxr
0.75 x 0.75
( 0.75 x 0.25 )
0.25 x 0.25
0.5625
.5625
+
+
2(0.1875)
.375
p + q = 1
+
+
0.0625
.0625
= 1
= 1
Tall is dominant and short is recessive
What is the frequency if 50 were tall and 30 were
short?
remember p + q = 1
50 + 30 = 80 x 2 alleles = 160 letters
q = tt = 60
p = TT or Tt = 100 but don’t know
p + 60/160
= 1
p + .375
= 1
p = .625
Now plug into P2 + 2pq + q2 = 1
-to find frequency of TT, Tt, tt
• Use hardy-Weinberg to predict frequency of
alleles from generation to generation
• Genotype frequencies remain the same unless
acted upon by outside influences.
ASSUME
• Mutations don’t alter gene pool
• Mating is random
• Population is VERY large
• Individuals don’t enter or leave the population
• Natural selection doesn’t occur (no one dies 1st )
Disruption of genetic equilibrium
We know Hardy-Weinberg assumptions cannot
stand
1. Mutations occur changes gene pool
2. Gene flow individuals move in/out of
populations
–
–
Immigration= move into
Emigration = move out
3. Genetic drift – random events occur (disease,
natural disaster)
• Not really seen in large population
• Major impact in small population
4. Nonrandom mating-mating is really not
random ….based on geographic location
5. Sexual selection—males usually brightly
colored to attract females
•
shows females males have GOOD traits so
pick me!!
5. Natural Selection
• Is really ongoing so disrupts genetic
equilibrium
3 types
1. Stabilizing selection—individuals with
average trait have highest fitness
• Extreme traits have lower fitness
• Larger than average lizards “stick” out
more
• Smaller may not be able to run fast
enough to escape
2. Disruptive selection
-individuals with extreme variations have
greater fitness
-average “stick out”
3. Directional selection
- individuals with extreme variations have
greater fitness
-pull average to extreme variation
What separates these two species?
Leopard frog
Wood frog
What separates these two species?
Leopard frog breeds between beginning of April through late April.
Wood frog breeds mid March through mid April.
What is the goal of this
game?
What obstacles must the
frog overcome?
What will happen to this particular
frog population if frogger can’t
make it across the road?
Stream?
This is called geographic
isolation
Geographic Isolation
• Geographic isolation results from the
separation of population subgroups by
geographic barriers.
This could be:
-road
-Deep canyon
-body of water
-anything an organism can
not cross!!
Allopatric Speciation
Geographic isolation may lead to allopatric
speciation.
•
•
•
•
Different “homelands”
Species no longer share the same gene pool
More likely to occur in small populations
Possibly over time the species will no longer be
able to reproduce= reproductive isolation
Sympatric speciation
– Reproductive isolation within the same
geographic area
Sympatric speciation
Species adapt to different niches & no longer
mate
• One group of lizards prefers life on the ground, and
the other prefers life in the tree
• Eventually they don’t “find” each other to mate
Sympatric speciation
Species adapt to different niches & no longer
mate
The red color of Mimulus cardinalis attracts
hummingbirds but goes unnoticed by
bumblebees. Bumblebees prefer the pale pink
petals of Mimulus lewisii, which in turn are
unpopular with birds.
The monkeyflower Mimulus lewisii
• is usually pink and pollinated by bees (left). One
mutated gene, which is responsible for the
yellow-orange petals (right), causes the bees to
drop their visits and hummingbirds to pollinate
the plant.
Rates of Speciation
• In the gradual model of speciation
(gradualism), species undergo small
changes at a constant rate. (over a few
million years)
• Under punctuated equilibrium, new
species arise abruptly, differ greatly from
their ancestors, and then change little over
long periods. (over thousands of years)
What do you notice?
Look at wing color
Concept map
Natural selection
in a population
That can be subjected to
reproductive barriers
Can be separated
geographically during
Reproductive isolation
Geographic isolation
Can lead to new
species during
speciation
Chapter 17
Classification of organisms
• 17.1 Biodiversity
• Taxonomy- science of describing, naming,
and classifying organisms
– Aristotle was 1st to classify but system had
problems
• Based on where organism lived—land, water, air
Aristotle
All
All Organisms
Organisms
Animals
Air
Land
Plants
H2O
Structure
Size
All Organisms
Fish
Rabbit
Robin
Animals
Air
Land
Plants
H2O
All Organisms
Duck ??
Turtle ??
Alligator ??
Animals
Air
Land
Plants
H2O
Linnaean System
• Devised naming system using 2 names
• Binomial nomenclature
• Used hierarchy of organization
Levels of Classification
• Organisms are grouped by shared
characteristics from very broad to more
specific groups.
• The more classification levels that two
organisms share, the more characteristic they
have in common.
• Example: shoes
1. Domain
Humans
2. Kingdom
Animalia
3. Phylum
Chordata
4. Class
Mammalia
5. Order
Primata
6. Family
Hominidae
7. Genus
Homo
8. Species
sapiens
King Phillip Came Over From Gulf Shores
Systematics 17.2
• Phylogenetics—analysis of evolutionary
relationships among organisms
– This is based on several pieces of information or
evidence
• Visible similarities between living organisms and
fossils
• Compare embryonic development
• Compare similar chromosomes, macromoleculesDNA
• Use homologous NOT analogous structures
– These phylogenetic diagrams or trees are
hypothesis showing how organisms are related (can
be changed as new evidence is added
Cladistics
• Cladistics uses shared, derived
characters as the only criterion for
grouping taxa.
– Shared-all members have in common
– Derived-feature that evolved only w/I the
group
Cladogram: Major Groups of
Plants
Outgroup – want all ?’s to be NO
Phylogenetic Diagram of Mammals
Plane, car, feet, bike, motorcycle
feet
bike
motorcycle
car
plane
Cladogram
• Molecular Cladistics
– Molecular similarities (such as similar amino
acid or nucleotide sequences), as well as
chromosome comparisons, can help
determine common ancestry.
• Chromosomes
– Analyzing karyotypes can provide more
information on evolutionary relationships.
Similarities in Amino Acid Sequences
Embryonic evidence
Questions
• What is the evolutionary history of a species
called?
• Phylogeny
• What is the term for a clsassification system
based on shared, derived characteristics?
• Cladistics
• Name 2 types of info used to classify organisms.
• Visible similarities, embryonic, chromosomes,
DNA
Questions
• How could a biologist use cladistics to
determine whether the flippers of a sea
lion and a whale are homologous or
analogous?
• Study bones and fossils of both to
determine if homologous or analogous.
Modern Classification 17.3
The Tree of Life
• Revising the Tree
– The phylogenetic analysis of rRNA nucleotide
sequences by Carol Woese led to a new “tree
of life” consisting of three domains aligned
with six kingdoms.
Modern classification
17.3
• Organisms divided into domains and
Kingdoms.
• 3 Domains
– Bacteria
– Archea
– Eubacteria
Domain Bacteria
• Domain Bacteria
– Domain Bacteria aligns with Kingdom
Eubacteria, which consists of single-celled
prokaryotes that are true bacteria.
Three Domains of Life,
• Domain Archaea
– Domain Archaea aligns with Kingdom
Archaebacteria, which consists of singlecelled prokaryotes that have distinctive cell
membranes and cell walls.
Three Domains of Life,
• Domain Eukarya
– Domain Eukarya includes the kingdoms
Protista, Fungi, Plantae, and Animalia.
– All members of this domain have eukaryotic
cells.
Modern classification
6 kingdoms
Domain
Bacteria
Bacteria
Domain
Archaea
Archaea
Domain
Eukarya
Animalia
Fungi
protista
Plantae
Kingdom and Domain Characteristics
Phylogenetic Diagram of Major Groups of
Organisms