Transcript Evolution-Speciation and Reproduction Barriers PPT

Evolution and
Speciation (Part 4)
Ms. Gaynor
AP Biology
Chapter 24: The Origin of
Life
Practice Problem #1
Red color (R) is dominant to yellow
color (r) in flowers.
 In a population of 241 turtles, 34 are
yellow.
 What are the allele frequencies?
 What percentage of each genotype are
in this population?

ANSWER KEY
R= Red
r = yellow
 34/241= 0.14 = white = rr= q2
 √0.14=√q2
 q = 0.37 then p = 0.63
 RR = p2 = (0.63)2 = 0.3969 = 39.69%
 Rr = 2pq = 2(0.63)(0.37) = 0.4662= 46.62%
 rr = q2 = (0.37)2 = 0.1369 = 13.69%

Practice Problem #2
Red color (R) is dominant to yellow
color (r) in flowers.
 In a population of 241 turtles, 14 are rr,
200 are Rr and 27 are RR.
 What are the allele frequencies?
 What percentage of each genotype are
in this population?

ANSWER KEY







R= Red
r = yellow
gene pool= 482 alleles (241 flowers x 2)
R = p = 27 + 27 + 200 = 254
AA
Aa  p = 254/482 or 0.53
r = q = 14 + 14 + 200 = 228
aa
Aa  q = 228/482 or 0.47
RR = p2 = (0.53)2 = 0.2809 = 28.09%
Rr = 2pq = 2(0.53)(0.47) = 0.4982= 49.82%
rr = q2 = (0.47)2 = 0.2209 = 22.09%
What is Natural Selection?

The process by which individuals leave
more offspring on average than do other
individuals in the same population.
HOW?

An organism’s environment (habitat)
favors certain adaptations
(characteristics or behaviors) that allows
the organism to better survive and
reproduce
Types of Adaptations

Protective Coloring
– Camouflage and Mimicry
 Physiological Adaptations
– Reproductive/Hormonal Changes
– Color changes
 Behavioral Adaptations
– Courtship dances/ songs
– “Fighting” tactics
 Also arise in response to environmental
pressures
– Temperature, Antibiotic/pesticide
resistance
RECALL: Evidence for
Evolution
Fossil record
 Comparative Anatomy

– Homologous structures
– Analogous structures
Comparative Embryology
 Vestigial structures
 Molecular biology (DNA/RNA/protein
amino acid differences)
 Biogeography
 Field studies

REVIEW:
What is a Population?
Populations evolve over
MANY generations,
individuals do NOT evolve
 Populations are groups of
interbreeding individuals
that live in the same place
at the same time
 Individuals in a population
compete for resources
with each other

How Does Evolution Work?

Populations produce more offspring
than the environment can support
– Carrying capacity sets the “limit”

The unequal ability of individuals to
survive and reproduce (i.e.-an
organism’s fitness) leads to the
gradual change in a population over
many generations
– Allele frequencies (p and q) to change
Mechanism for change in
a population of organisms
Animals who have greater fitness
survive in environment and live to
reproduce
 Random changes in DNA (mutations)
can lead to greater or less fitness

– Produced by Sexual Reproduction
– Allow for DIVERSITY in a Population

Adaptations allow an organism to
survive better in their environment
RECALL: 3 Types of
Natural Selection
 Directional
–Extreme form favored by
natural selection
 Stabilizing
–Middle form most successful
 Disruptive
–Two extreme forms successful
in separate environments
Types of Evolution
1. Convergent evolution

organisms that are NOT closely related
independently evolve similar traits as a
result of having to adapt to similar
environments.
Ex: Dolphins & fishes
Ex: Wings of bees & bats
2. Divergent evolution

2 species gradually become different
 Often occurs when closely related
species diversify to new habitats
 responsible for the creation of the
current diversity of life on earth from the
first living cells
Ex: Darwin’s finches
Type: Adaptive radiation
Adaptive Radiation
Example of divergent evolution
 Adapted
species from a common
ancestor when they are
introduced to new environmental
opportunities
 Typically occurs when a few
organisms make their way to new,
usually distant areas OR mass
extinctions occur, which open up
new niches
Hawaiian archipelago  Example of
adaptive radiation
Dubautia laxa
KAUAI
5.1
million
years
1.3
million
MOLOKAI years
MAUI
OAHU
3.7 LANAI
million
years
Argyroxiphium sandwicense
HAWAII
0.4
million
years
Dubautia waialealae
Dubautia scabra
Dubautia linearis
3. Coevolution
2 organisms evolve (change) in
response to each other
 Insects and the flowers (ex: orchids)
they pollinate

4. Parallel Evolution
2 species evolve independently of each
other, maintaining similar traits
 Usually occurs between unrelated
species that do NOT occupy the same or
similar habitats

– Ex: Eutherians (placental) and Marsupial
mammals
Review
Two Basic Patterns of
Evolutionary Change
 Anagenesis
(phyletic evolution)
–transforms one species into
another
 Cladogenesis (branching evolution)
– the splitting of a gene pool,
giving rise to one or more new
species
LE 24-2
Anagenesis
Cladogenesis
How fast does evolution
occur?
 Gradualism
–Species change slowly
(gradually) over time
 Punctuated Equilibrium
–Species can make rapid
“leaps” in evolution
Time
Gradualism model
Punctuated equilibrium model
What is a Species?
 Species
is a Latin word meaning
“kind” or “appearance”
–A population of organisms that
produces viable fertile
offspring in nature.
–They can NOT interbreed with
other populations
Similarity between different species  different behaviors and songs
Diversity within a species  defined by capacity to interbreed.
Speciation

Speciation = the origin of new
species
– Must explain how new species originate
and how populations evolve

Microevolution (genotype evolution)
– adaptations that evolve within a
population’s gene pool

Macroevolution (phenotype evolution)
– refers to evolutionary change at the
population level
– Major biological changes evident in the
fossil record