Download Topic 13: Evolution

Topic 13: Evolution
1. What is Evolution?
2. Lamarck, Darwin & Wallace
3. Survival of the “Good Enough”
4. Population Genetics & Hardy-Weinberg Law
5. The Power of Natural Selection
6. Microevolution in Large & Small Populations
7. Evidence Supporting Evolution
8. Speciation & Extinction
9. Systematics
Topic 12: Lesson 1
Resources:
1. Read Chapter 12.1 pp. 238
2. Does Evolution Really Matter?
3. Zaption – It’s Okay To Be Smart – 12 Days of Evolution
WHAT IS EVOLUTION?
What Is Evolution?
Why does this giraffe have a long
neck? Why do these bleeding heart
flowers have such a strange shape?
Evolution explains the features of all
organisms, from microbes to humans.
Descendants are Modified Versions of
Their Ancestors
Evolution is descent with modification—changes in heritable traits
from generation to generation.
Evolution’s Misconceptions
Human Evolution
Topic 13: Lesson 2
Resources:
1. Read Chapter 12.2 pp. 238-243
2. Skit – A Conversation between Darwin & Lamarck
3. Worksheet – Darwinian & Lamarckian Thinking
LAMARCK, DARWIN & WALLACE
Timeline of Evolutionary Thought
Lamarck’s Hypotheses
• Proposed the first scientifically
testable explanation for the
change that occurs in species
1. A change in the environment
produces a need for change in
animals
2. Acquired characteristics will be
passed on to offspring
3. If an animal uses a body part
often, it will grow in strength
and size and vice versa
Evolutionary Thought Over the
Centuries
Charles Lyell
• Geologist – Theory of Uniformitarianism
– geological features of Earth have changed, and will
continue to change
– Earth is older than 6000 years
– Law of Superposition – new rock layers are above
older rock layers
Darwin’s Puzzle
Chiru
Yak
Darwin’s Voyage on the HMS Beagle
(1831-1836)
Darwin the Naturalist
• At each port, Darwin would collect samples
and analyze them when back onboard
Thomas Malthus
The Logic of Natural Selection
Observations Of Nature
• Genetic variation exists
within a species
Inferences From Observations
• Descent with modification
• The amount of resources in
a given ecosystem limits the
population
• Struggle for existence
• More offspring are born
than can survive
• Unequal reproductive success
On the Origin of Species (1859)
• Darwin published his work that summarizes
his arguments in support of natural selection
• He described dozens of species in support for
his ideas
Topic 13: Lesson 3
Resources:
1. Read Chapter 12.3 pp. 244-7
2. Lab – Evolution & Natural Selection
3. Lab – Coevolution of Flowers and Pollinators
4. PBS – Surviving AIDS: Delta32
SURVIVAL OF THE FITTEST “GOOD ENOUGH”
Nature Selects the Best Suited Individuals
This seahorse blends almost
perfectly into its habitat. How
could an organism like this arise?
Each generation, the best
camouflaged individuals survive to
reproduce. The alleles conferring
camouflage become more
common in each generation.
But natural selection does not
create camouflage alleles.
Instead, it strongly selects for
camouflage alleles that arise by
chance.
Types of Fitness
Ability to attract a mate
Ability to catch prey (food)
Ability to outrun predators
Ability to camouflage for safety
Natural Selection Molds Evolution
Natural selection operates on the variation present in a
population. Since more individuals are born than resources can
support, the struggle to survive is inevitable.
Some individuals in
a population are
better than others
at surviving and
reproducing.
Adaptations Provide an Advantage
• Heritable traits that provide a selective
advantage because they improve an
organism’s ability to survive and reproduce
Example: Grey Owl – silent
flight, neck with large
turning radius, sharp talons,
great vision/depth
perception
Natural Selection Does NOT Create
Bacteria that are resistant to antibiotics have an adaptive trait
that non-resistant bacteria lack. When antibiotics are
administered, resistant bacteria are strongly selected for survival.
Antibiotics cannot create a resistance allele. The variation in
resistance was already present in the population; the presence of
antibiotics caused the resistance allele frequency to shift.
Evolution Never Stops
As environmental conditions change, the phenotypes that natural
selection favors will also change. Adaptations that seem “perfect”
in one environment would be completely wrong in another.
Co-Evolution
This orchid and its wasp pollinator
have evolved alongside one
another for long enough that no
other animal can pollinate the
flower.
But the orchid does not evolve
in order to be better-pollinated
by the wasp. Neither the
orchid nor natural selection
has foresight.
Topic 13: Lesson 4
Resources:
1. Read Chapter 12.4 pp. 248-9
2. Crash Course – Population Genetics
3. Bozeman Science – Hardy-Weinberg Equation
4. The Penguin Prof – Watch Your P’s and Q’s
5. Bleier Biology – Hardy-Weinberg Practice Problems
6. The Biology Place Lab Bench – Hardy-Weinberg Law of Genetic Equilibrium
7. Hardy-Weinberg Practice Problems
POPULATION GENETICS & HARDYWEINBERG LAW
Populations Change, Not Individuals
Recall that a population is a group of interbreeding organisms of
the same species that experience the same environmental
changes and the same pressures of natural selection.
Gene Pools Are Acted on By
Natural Selection
Evolution is detectable by
examining the
population’s gene pool—
the entire collection of
genes and alleles.
Evolution occurs in a population
when allele frequencies change
from one generation to the next.
Percentage of Alleles in a Population
An allele frequency is calculated
by the following equation:
# of copies of an allele
Total # of alleles for the same
gene in the population
Microevolution
Even for the same species,
gene pools differ from
population to population. The
gene pool for a population of
Swedes differs from that of a
population of Asians.
If Swedes migrate to Asia and
interbreed with locals, then
allele frequencies in the gene
pool will change. Evolution,
more specifically,
microevolution has occurred!
What Is Evolution?
MICROEVOLUTION
MACROEVOLUTION
• Change in allele frequencies • Change within organisms
over long periods of time
in a gene pool
(millions of years)
• Change within organisms that
happens over a short period • Leads to the evolution of
new species
of time (a few generations)
Hardy-Weinberg Equations
• Used to predict allele frequency in gamete
pool and genotypic frequencies in the next
generation
p+q=1
(p + q)2 = p2 + 2pq + q2 = 1
Hardy-Weinberg Assumptions
1.
2.
3.
4.
5.
6.
7.
8.
Organisms are diploid
Generations are non-overlapping
Population is infinitely large
Mutation does not occur
Sexual reproduction
Random fertilization
Migration does not occur
Natural selection does not operate
Hardy-Weinberg Equilibrium
• A population in Hardy-Weinberg equilibrium is
“not evolving”
• If the allele frequencies change from one
generation to the next the population is
evolving
Topic 13: Lesson 5
Resources:
1. Read Chapter 12.5-6 pp. 250-2
2. Three Modes of Natural Selection
3. Lab – Sickle-cell Disease
4. Crash Course – Natural Selection
THE POWER OF NATURAL SELECTION
Three Modes of Natural Selection
Stabilizing, Directional
& Disruptive modes of
natural selection are
distinguished by their
effects on
the phenotypes in a
population.
Directional Selection
One phenotype is
favored over
another
Disruptive Selection
• Extreme phenotypes are favored over an
intermediate phenotype
Stabilizing Selection
• An intermediate phenotype is favored over
the extreme phenotypes.
Natural Selection Can Shape
Populations in Many Ways
Natural Selection Can Shape
Populations in Many Ways
However, these three
models do not explain
why natural selection
maintains some harmful
alleles in the population.
Heterozygote Advantage
• Some harmful alleles still exist in the population
because they give the heterozygous person an
advantage
– Examples: Sickle-cell anemia, hereditary
deafness/thickened epidermis, thalassemia/heart
attacks
Topic 13: Lesson 6
Resources:
1. Read Chapter 12.7 pp. 253-5
2. Worksheet – Microevolution & Hardy-Weinberg
3. Video - Rock Pocket Mice
MICROEVOLUTION IN DIFFERENT
SIZED POPULATIONS
Microevolution in Large Populations
• English peppered moth (Biston betularia)
5 Mechanisms that affect gene pools
1. Natural selection – allele frequency is
dependent upon reproductive success
2. Mutation – one allele changing to another
spontaneously and randomly
3. Genetic drift – random change in allele
frequency
4. Gene flow – allele movement caused by
migration
5. Nonrandom mating – individuals choose who
to mate with
Natural Selection & Mutation
Genetic Drift
• In each generation, some individuals may,
just by chance, leave behind a few more
descendants than other individuals
16.5 Microevolution in Small
Populations
Population Bottleneck
• When a drastic event occurs and the population is
reduced for a few generations
Example: American bison
1492 population 60,000,000
1890 population 750
2000 population 360,000
Inbreeding Occurs in Small Populations
• Inbreeding – increase of homozygosity of alleles
caused by genetic drift
– Example: California condor
– 22 birds were captured and bred at the San Diego Zoo
– 384 condors are now living
Inbreeding Depression
• Inbreeding depression – decreased fertility
and survival rate (vigor) caused by inbreeding
– Problem in zoos, endangered species, isolated
populations, bred animals (dogs, livestock),
Gene Flow
• Allele frequencies of populations can change
due to permanent migration
Founder Effect
• New populations can be started by migrants so
that the genetic makeup or allele frequency
differs from the original population
– Extreme case: the founding of a new colony by one
pregnant animal or one plant seed
Founder Effect in the Real World
• 1814, 15 people founded a
British colony on Tristan da
Cunha
• One of the colonists carried the
allele for retinitis pigmentosa
• 1960, 240 descendents, 4 had
retinitis pigmentosa, 9 were
carriers
Nonrandom Mating/Sexual Selection
• Individuals choose their mate
Showing Off = Reproductive Success
At face value, flashing showy plumage, and butting heads with rival
males all appear to waste energy. How can natural selection allow
for traits that apparently reduce survival?
Intersexual Selection
Intrasexual Selection
Sexual Selection Directly Influences
Reproductive Success (Inter vs. Intra)
Intersexual
Intersexual
Intrasexual
Choosy Females Effect Allele
Frequency &/or Behavior
Generations of choosy females have selected for males with
nest-building traits or elaborate ornamentation.
Finding a Mate > Spending Energy
Although the yellow weaver bird uses time and energy making
nests for females, this behavior might secure a mating opportunity.
Topic 13: Lesson 7
Resources:
1. Read Chapter 13.1-3
2. Worksheet – Comparing Amino Acid Sequences
3. POGIL-Evidence for Evolution
4. Blenny Fish Evolution
5. Crash Course – Evidence for Evolution
EVIDENCE SUPPORTING EVOLUTION
Fossil Record
The physical proof of fossils (eggs, body
parts, foot prints, etc.) helps us to
understand the sequence of events over
time in respect to which organisms were
alive, where they lived, what they looked
like and so forth
Biogeography
• The study of the distribution of organisms
through time and space
• Where Life Lives
Convergent Evolution
• Two or more unrelated species become more
and more alike due to common environmental
NORTH
pressures, not due to ancestry
AMERICA
Sugar gliders are marsupials (more
closely related to a kangaroo than a
squirrel); both creatures live in an
environment where gliding quickly
from tree to tree is a helpful trait.
Sugar
glider
AUSTRALIA
Flying
squirrel
Divergent Evolution
Hyracoidea
(Hyraxes)
• Adaptive Radiation –
two or more related
species become less
and less related over
time
Sirenia
(Manatees
and relatives)
Moeritherium
Barytherium
Deinotherium
Mammut
Platybelodon
Stegodon
Mammuthus
Elephas maximus
(Asia)
Loxodonta africana
(Africa)
Loxodonta cyclotis
(Africa)
34
24
5.5
Millions of years ago
2
104
0
Years ago
Comparative Anatomy
• Scientists use similarities and differences
between organisms to determine evolutionary
relatedness
Homologous Structures
• Organisms that are descended from a common
ancestor share common ancestral traits (structural
resemblances) that may have developed to perform
different functions
Humerus
Radius
Ulna
Carpals
Metacarpals
Phalanges
Human
Cat
Whale
Bat
Analogous Structures
• Unrelated (or distantly related) species of
animals or plants develop similar traits when
exposed to similar environmental pressures
• These are seen in convergent evolution and
NOT a reflection of shared ancestry
Example: the wings of butterflies, birds and bats
Vestigial Structures
• A Structure that is a remnant of an organism’s
evolutionary past and has no current function
• Useful indication of common ancestry where
one species maintained the use of the
structure
Embryology
• The branch of biology that deals with the
formation, early growth, and development of
living organisms
• The high degree of similarity of these early
developmental forms supports that species
have arisen from common ancestors
Example: the embryonic development of humans and turtles
Biochemical
• Comparing DNA nucleotide sequences or
amino acids sequences in a protein helps
reveal evolutionary relationships
Topic 13: Lesson 8
Resources:
1. Read Chapter 14.1-5 pp. 282-294
2. Speciation – Mosquitoes
3. Worksheet – Types of Reproductive Barriers
4. Examining the Fossil Record
5. The London Underground Mosquito
6. Crash Course – Speciation
SPECIATION & EXTINCTION
Speciation
• Changes in isolated populations that lead to
the formation of new species
• At what point are two populations considered
separate species?
– When they become reproductively isolated from
one another (meaning they cannot interbreed and
produce fertile offspring)
Gradualism & Punctuated Equilibrium
Reproductive Barriers Cause
Species to Diverge
Prezygotic Barriers
Do not allow zygote to be formed
• Habitat isolation
• Temporal isolation
• Behavioral isolation
• Mechanical isolation
• Gametic isolation
Postzygotic Barriers
Reduce fitness of hybrid
• Hybrid inviability
• Hybrid infertility
• Hybrid breakdown
Note- isolation alone isn’t what causes the speciation; once isolated, each
population can evolve separately and become different enough from one another
that they can no longer mate successfully
Geographic Isolation
• Habitat isolation – species live in different
habitats
Temporal Isolation
• Species are active or fertile at different times
Behavioral Isolation
• Different courtship rituals
Mechanical Isolation
• Mating organs or pollinators are incompatible
Gametic Isolation
• Gametes cannot unite
Hybrid Inviability
• Hybrid offspring develops but either dies
before birth, or dies before sexual maturity
Hybrid Infertility
• Sterility – Hybrid offspring are not able to
reproduce
Hybrid Breakdown
• When hybrids reproduce but their offspring cannot
Topic 13: Lesson 9
1. Read Chapter 14.6 pp. 294-295
2. The IS: Clad Method of Cladistics
3. POGIL: Biological Classification
4. Organism Classification Project
5. What Did a T-Rex Taste Like?
6. The Evolution of Flight in Birds
7. iTOL
8. Crash Course: Taxonomy: Life’s Filing System
SYSTEMATICS: TAXONOMY &
PHYLOGENETICS
Taxonomy
• Describing, classifying, and naming species
•
•
•
•
•
•
•
•
Domain
Kingdom
Phylum
Class
Order
Family
Genus
species
Used as the scientific name;
binomial nomenclature
Phylogenetics
• Phylogenetics – studying the evolutionary
relationships between organisms
Homologous structures and DNA sequences can be used to
create evolutionary trees (cladogram, phylogenetic tree)
Branch point
(common ancestor)
Lungfishes
Amphibians
1
Tetrapod limbs
Mammals
2
Lizards
and snakes
3
Amnion
(membrane that
surrounds and
protects embryo)
4
Crocodiles
Homologous
characteristic
Feathers
Ostriches
6
Birds
5
Hawks and
other birds
Note- crocodiles & birds share a common ancestor; birds did not evolve from crocodiles.
Tree of Life