Transcript Evolution

Standard 5
Unit 12 –
Evolution
& Biodiversity
Objective
B5.1A: Summarize the major concepts of natural
selection (differential survival and reproduction
of chance inherited variants, depending on
environmental conditions).
 B5.1c: Summarize the relationships between
present-day organisms and those that inhabited
the Earth in the past (e.g., use fossil record,
embryonic stages, homologous structures,
chemical basis).

Theory of Evolution
A.
Idea supported by scientific evidence (but no concrete
experiments) over a long period of time
B.
Change in a species due to mutation of the DNA code that
occurs over a long time.
Evolution is the result of genetic changes that occur in
constantly changing environments.
Evolution is all the changes that have transformed life from
its earliest forms to what we see today.
Working definition = Evolution is the progressive change in
organisms over time.
C.
D.
E.
Evolution of Air Breathing:
Evolution of Brains:
Charles Darwin
Natural Selection:
 “Survival
of fit”
 Fit reproduce
 Competition
for resources
 Best adapted
species survive
Introduction to Charles Darwin's Theory
of Evolution (00:54)
HMS Beagle Voyage 1835
Darwin’s Voyage of Discovery
A reconstruction
of the HMS
Beagle sailing off
Patagonia.
The 5 Year Voyage of the Beagle
Darwin’s key ideas:
A. REPRODUCTION: Organisms produce
more offspring than can survive
 B. VARIATION:Variety in traits exist
 C. SURVIVAL OF THE FIT: Some traits allow
survival & are passed on
 D. Over time certain variations make up most
of a population & they may be different from
their ancestors

Darwin’s Ideas Did Not Develop in a Vacuum

Contributor’s to Darwin’s thinking
included:
– Charles Lyell – uniformatarianism
– Georges Cuvier – species extinction
– Thomas Malthus – struggle for existence
– Jean Baptiste de Lamarck – evolution by acquired
characteristics.
– Alfred Russel Wallace Independently Drew the
Same Conclusions as Darwin
Malthus’s contribution:
 Populations
grow to a
maximum level
 Environmental
limitations
 Fit animals out
compete the
less fit
P
O
P
U
L
A
T
I
O
N
50%
30%
Carrying
Capacity
10%
10 yr 20 yr 40 yr 60 yr 80
-10%
Darwin’s Observations & Inferences
Observation 1: Left unchecked, the number of organisms of
each species will increase exponentially, generation to
generation.
 Observation 2: In nature, populations tend to remain stable
in size
 Observation 3: Environmental resources are limited.
 Observation 4: Individuals of a population vary extensively in
their characteristics with no two individuals being exactly alike.
 Observation 5: Much of this variation between individuals is
heritable.

Darwin’s Observations & Inferences

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
Inference 1: Production of more individuals than can be
supported by the environment leads to a struggle for existence
among individuals, with only a fraction of offspring surviving in
each generation.
Inference 2: Survival in the struggle for existence is not
random, but depends in part on the heritable characteristics of
individuals. Individuals who inherit characteristics most fit for
their environment are likely to leave more offspring than less fit
individuals.
Inference 3: The unequal ability of individuals to survive and
reproduce leads to a gradual change in a population, with
favorable characteristics accumulating over generations
(natural selection).
Taken together, these three inferences are a statement of
Darwin’s Theory of Evolution.
Evolution Evidence:
1. Adaptations
2. Fossils
3. Comparative anatomy
4. Comparative embryology
5. Comparative Biochemistry
6. Plate Techtonics
1. Adaptations: features
suited to a particular environment
that allow organisms to survive
Inuit people, who live
in the extreme cold
of the Arctic, have
short, stout bodies
that conserve heat.
Adaptations
Masai people,
who live in the
arid lands of
eastern Africa,
have tall, lean
bodies that
disperse heat
well.
Plant Adaptations:
Help!!!
Venus Fly Trap
 Captures
Animals
 Acquires
Minerals
 For Photosynthesis
Leaf Adaptations:
Succulents
Thick
Store
Water
Prevent
Drying out
Leaf Adapatations:
Pine Needles
 Shed snow
 Less water
loss
 Reduced
surface area
 Tolerate
wind
Flower Adaptations:
Fly pollination:
Hair along
petals
Putrid smell
Bee pollination:
Smooth petal
Sweet smell
2. Fossil Evidence:
The Evidence for
the Theory of
Evolution
(02:04)


1.
2.
3.
Once living remains
of organisms
Limited to:
Type of material
preserved (bone,
shell, impressions,
amber)
Incomplete record
Easily disrupted
Plant Fossil Evidence:
3. Comparative Anatomy:
Structural similarities link
related species
Comparative Anatomy
Structures:
Analogous:
1. Different ancestors
2. “analogy”=like
3. Different underlying
structures
4. Same Function
5. Similar Environments
Homologous:
1. Same ancestor
2. “homo”=same
3. Same underlying
structures
4. Different Functions
5. Different
Environments
Analogous Structures
Different underlying structures
(different ancestors)
 Same function, similar environments

Homologous Structures:
Same underlying structures, different functions,
different environments & common ancestor
4. Comparative embryology:
Similar embryo development in closely
related species
5.Comparative Biochemistry
Similar DNA
sequences=
 Similar Gene
segments of the
DNA
 Code for similar
traits
 In closely related
species

Kinship

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

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There is a degree of kinship between organisms or species that
can be estimated from the similarity of their DNA and protein
sequences.
Chimpanzees are so closely related to humans that they should
properly be considered as members of the human family,
according to new genetic research.
Scientists from the Wayne State University, School of Medicine,
Detroit, US, examined key genes in humans and several ape
species and found our "life code" to be 99.4% the same as
chimps.
They propose moving common chimps and another very closely
related ape, bonobos, into the genus, Homo, the taxonomic
grouping researchers use to classify people in the animal
kingdom.
Humans, or Homo sapiens to give the species its scientific name,
are the only living organism in the genus at the moment although some extinct creatures such as Neanderthals (Homo
Neanderthalis) also occupy the same grouping.
Dr Wildman said: "You could say that humans
and chimps are as similar to one another as
say horses and donkeys.
Evidence of
Evolution –
Conservation and
Diversification at
the Molecular Level
Why should different
organism possess
related genes?
Why does the degree
of relationship of genes
match their degree of
relationship established
by other methods?
Evidence for
Evolution –
Evolution
Observed
Evolution of pesticide
resistance in response to
selection.
Evidence for Evolution –Evolution Observed
Evolution of drug-resistance in HIV
6. Plate Techtonics
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

Geological theory:
Continental masses were one land mass that explains
Closely related species have common ancestors on
now separated continents
What Darwin Never
Knew
http://video.pbs.org/video/137207
3556/
Movie

Trace the relationship between environmental
changes in the gene pool, such as genetic drift
and isolation of subpopulations.
Biomes: Islands and Evolution (56:00)
Early Theories of Evolution:
Darwin:
 Current theory
 Natural Selection
 “Survival of fit”
 Reproduction of the
best adapted species
Lamark:
 “Use & Disuse”
 Abandoned
 No knowledge of
genetic traits or
mutations in sex
cells
Lamark’s Theory
“Use
and Disuse”
 Use of
structure
results in
evolution
 Does not take
into account
DNA or sex cell
mutations
I. What is evolution?
A change in the genetic makeup of a
population with time.
 It is a two-step process

– Development of genetic variability in the
population.
– Natural selection of those variations which are
favorable for survival.
Example

Let’s say a population
of black spotted
cattle--BB-- eventually
turn into a population
of white spotted
cattle--bb-- over a
period of years.
II. Genetic variability

Assuming that a population starts out with
the same genetic makeup, all new genetic
material in that population will arise by
mutation.
– A mutation is a random inheritable event.
– Let’s take our black spotted cattle as an
example; for some reason the chromosomes
that code for black spots are mutated.
Variability

This mutation Changes the BB to Bb. Now
with the b gene in the herd, White spotted
cattle can arise.
Variation

Variation in the chromosomes occurs
when an egg and a sperm unite. Both
carry unique traits from the parents into
one individual, forming an individual which
varies from the parents.
– This variation is normally a random event.
– In our example, let’s say two mutated animals
mate with one another. Let’s look at their
offspring.
B
B
BB
(black)
b
Bb
(black)
b
Bb
(black)
bb
(white)
A Scenario to demonstrate natural
selection
It has been 50 years since the first mating of
our mutated cattle. Over the years the once
all Black spotted (BB) herd is now about
75% black spotted and about 25% white
spotted (bb).
 A new disease has mutated during this time
period. A disease known as Bovine Black
Spotitis. The disease is not fatal, but any
black spotted (BB or Bb) bull or cow is
sterile.

Question?
The disease spreads quickly through the
herd and within six months time all black
spotted cattle are sterile.
 What will eventually happen to the herd?

Answer

Only the white cattle will be able to
reproduce, eventually producing a
completely herd of white spotted cattle.
(bb)
Natural Selection
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As long as the environment does not again change then
these individuals will become the “normal” population.
The sequence of events that leads to a certain characteristic
being “selected” in the environment is called natural
selection.
Populations change in response to their environment.
Acts on phenotype of an organism.
(Not genotype)
Determines the
differential survival of
groups of organisms
Evolution’s
Core Principles
Natural selection
Evolution’s
Core Principles
Common descent
with modification
Macroevolution: Long time
scale events that create and
eliminate species
Variations:
 Differences
in traits
 Come about by mutations in
genes
 Random
 Occur in sex cells
 Passed on to future
generations
Bird Beak Adaptations:
Genetic Drift
Changes in the gene pool due to:
1.
2.
3.
4.
5.
Random mating
Over a long time period
No immigration of males
No emigration of females
Sufficient resources that
match the adaptations
Same Species Must:
Show similar
characteristics
 Successfully
interbreed
 Producing fertile
offspring

Donkey + Horse=
Mule (infertile)
Speciation
 Evolution
 New
Species
 Over time
 By Isolation
 Natural
Barriers
Speciation
Formation of a new
species
Geographic Isolation


Separation of organisms
by geographic features.
A physical barrier divides
a population:
– Mountains
– Lakes, oceans, rivers
– Desserts
These two groups are not able
to mate
=> may lead to new species
Reproductive Isolation
When two different species can
not mate and have successful
offspring


– Geographic barriers
– Anatomy or physiology
– Social behaviors
Prevention of mating between formerly interbreeding
groups.
or
The inability of these groups to produce fertile
offspring
Reproductive Isolation:
Two organisms cannot mate
Separated by geographic
boundaries
Anatomical differences
Physiological differences
Social behaviors
Gradualism
“gradual”
 Small changes
 Over a long time

Gradualism

Model of evolution
involving slow,
gradual changes
to a species over
time.
Punctuated Equilibrium
“punctuation!”
 Large changes
 Happen rapidly
 Periods of no
change

Punctuated Equilibrium

Evolutionary
model

Rapid changes to
a species in a
short time,
followed by
periods of little
change.
Gradualism vs. Punctuated Equilibrium
 Gradualism:
#
S
P
E
C
I
E
S
Time
 Punctuated
Equilibrium
Gradualism vs. Punctuated Equilibrium
Adaptive Radiation:
“radiation”=
branching from
one source
“adaptive”= survival of fit
Evolution of many branches
of organisms from a single
source
Adaptive Radiation
Divergence

“diverge”=
branch off
 Homologous
structures
 Same origin
 Same underlying
structure
 Difference
functions
Human arm
Bat wing
Cat limb
Whale
flipper
Original Species:
Mammal
Convergence
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Bird wing
“converge”=come
together”
Analogous features
From different
origins
Organisms that fly
Similar
environments=
Similar functions
Different structures
* Homework – 43-1 Butterfly wing
Bat wing
Convergent Evolution
Placental mammals
Marsupial mammals
Convergent Evolution
Although marsupial mammals once populated all
land masses, they remain diversified only on the
isolated Australian continent, where they have
evolved to fill the same ecological niches that
placental mammals occupy elsewhere. The
Tasmanian wolf, for example, closely resembles
the doglike carnivores of other continents. More
specialized parallel adaptations include those of
the marsupial and placental anteaters, the
marsupial sugar glider and placental flying
squirrels, and the burrowing marsupial wombat
and placental ground hog. In this illustration,
placental mammals are in the top row, and their
marsupial equivalents are in the bottom row.
Genetic Variation

* Homework – Give examples of ways in
which genetic variation and environmental
factors are causes of evolution and the
diversity of organisms.