Ch. 15 and 16 Powerpoint (Evolution and

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Transcript Ch. 15 and 16 Powerpoint (Evolution and

What is Biological Evolution?
Who first proposed that
“life changes over time”?
Not Darwin….
Charles Darwin
It was Greek philosophers
such as Anaximander,
2600 years ago!
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Before going into details, let’s cover some
basics first and clarify some confusion
that frequently exists.
In your head:
Do you believe in God
or some type of Supreme Being or Force?
Do you believe in cells…that they are the
fundament units of life?
Are these the same sort of beliefs?
As a scientist, I do NOT believe that cells are the
fundamental units of life (part of Cell Theory).
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I also DO NOT believe that the
planets orbit about our sun
(part of Heliocentric Theory).
I simply CONCLUDE (or think) that Cell
Theory and Heliocentric Theory are
powerful and very well supported
explanations of how our world works.
I also do not BELIEVE in evolution.
I simply find it to be one of the most powerful theories
in all of science…
….supported by many independent lines of
evidence…which we will review briefly.
If someone in the future proposes a theory that explains
all that evolution explains and more, science must be
willing to consider that theory instead.
Such is the TENTATIVE nature of science.
Heliocentric Theory:
That the planets orbit the sun…
is just a theory too.
Cell Theory:
All life is made of
…is just a theory too.
Theory of Inheritance:
How DNA codes for life…
…is just a theory too.
Germ Theory:
Many diseases result from viral
and bacterial infections…
…is just a theory too.
HIV - the cause of AIDS
Atomic Theory:
…the structure of the atom
…is just a theory too.
Theories are the strongest,
most well supported explanations
in all of science.
There is NO term that we use in
science with greater confidence.
that evolution occurs.
So you have to wonder…
 Can people just choose which scientific
theories to accept or reject?
In many textbooks, there is confusion
about some terminology.
Many elementary and high school
textbooks use the word “Development”
instead of “Evolution”.
These two terms mean
completely different things.
Development addresses the changes that
occur within an individual’s lifetime.
Evolution addresses the changes
that occur in species over time.
And… “What is a Species?”
For organisms that reproduce sexually…which is by far most
Dr. Ernst Mayr proposed the Biological Species Concept:
A species is:
“a group of interbreeding natural populations that
are reproductively isolated from other such groups.”
What are we speaking about, when we talk about
Fact - That evolution occurs…
•That life has changed over time,
•That life continues to change over time, and
•That all life has a common ancestry.
Course / Ancestry - Who gave rise to whom and who is
most closely related to who…are matters of ancestry and
are still greatly explored & debated. “the family tree”
Mechanism - Darwin & Wallace proposed Natural Selection
as the mechanism. Although Natural Selection clearly
occurs, it is still debated in science whether or not there are
other mechanisms of evolution working too.
Chapter 15
Jean-Baptiste Lamark-1809
15-2 pg 376
1. Organisms strive to improve themselves
2. Most used body structures develop
 “Use it or lose it”
3. Used modification is inherited by offspring
Ex: giraffe necks & muscle builders
August Weisman- 1883
 Uses mice to disprove Lamark
 Cuts tails off of mice, didn’t lead to tailless
 “cut off the tails of 901 young white mice in 19
successive generations, yet each new
generation was born with a full-length tail. The
final generation, he reported, had tails as long
as those originally measured on the first”
Now on with the story of
Charles Darwin
and his contributions to
-Entered & left medical school
-Entered & left ministry
-Cambridge-meets John Henslow
Studies geology & biology
At the age of 22, Darwin began a
5 year voyage around the world on HMS Beagle
-5 year, global voyage
-Goal was to make maps of S. America
Galapagos Islands- Darwin notices
that many groups of animals
represent variations on a theme.
Similar by DESIGN….
Similar because of shared ancestry.
Similar because of shared ancestry.
Similar because of shared ancestry
Was all of life related…and thus similar
because of shared ancestry?
Into this world Darwin offered
5 theories,
in his major work,
On the Origin of Species…
1) Evolution occurs:
The world is not
- Instead, it is
changing, and
organisms change over
2) Common Descent:
Every group of organisms is
descended from a common ancestor.
3. Natural Selection:
Evolution occurs through
1) the production of
genetic variety and
2) the subsequent advantages
that result from certain
4. Gradualism: Evolution occurs through gradual change
instead of the sudden appearance of new forms.
Gradualism as proposed by
Charles Darwin
Punctuated Equilibrium proposed by scientists
working after Darwin
5) Multiplication of species:
a) Species multiply by splitting into
daughter species or
b) by geographic isolation of a founder population.
Darwin titled his book “On the Origin of Species…”
because he saw this part of his idea as one of the most
important contributions of his ideas.
Summarizing Darwin’s main ideas: Natural Selection
1. There is variation within populations
2. Some variations are favorable
3. More offspring are produced than can
4. Favorable variations = survival
5. Change over time leads to population
Lamark vs Darwin
 Both theorized that:
 Life changed gradually over time and was still
 that living things change to be better suited
and adapted to their environments
 all organisms are related
15-3 Publication
 Alfred Russel Wallace-makes similar voyage,
but his notes were destroyed
 Wants to publish findings
 So…..Darwin publishes 1858
“On the Origin of Species”
A note about the phrase “survival of the fittest”
Darwin referred to evolution as
“Descent with Modification”
The phrase “survival of the fittest” originated with
another scientist, Herbert Spencer, after reading Darwin’s
book Origin of Species.
In the 6th Edition of Orgin of Species, Darwin Retitled Chapter IV,
“Natural Selection; or the Survival of the Fittest.”
Today we know that this phrase is circular.
To be fit includes the ability to survive.
Thus the phrase means “survival of the survivors!”.
So the phrase “survival of the fittest” is not commonly
used by scientists.
 Multiple Lines of
Evidence Increases
 http://learn.genetics.u
Anatomical Studies
1. Homologous- modified structure seen
among different groups
Similar in structure & function
Ex: forelimbs-reptiles, mammals, birds
2. Analogous- similar in
function, different structure
ex: insect vs bird wing
3. Vestigial- structure once
used but not now
ex: appendix in humans
eyes of sightless species
16.1 Populations
 All individuals of the same species that live in
the same environment & interbreed
Features of populations:
 1. Population size- # of individuals
 Small is bad- interbreeding, natural disasters
 2. Population density- # of individuals in an
 Spaced widely apart= no mating
 3. Dispersion- random, even, or clumped
Growth Rate
 Exponential or J-shaped curve
 *not true because of diseases, predators, &
Carrying Capacity (K)
 Population size that an environment can
actually hold
 Gives us a Logistic Model
Gene pools
- total genetic info in a
 Allele frequency- look at
inside (genes)
 # of A / # of all individuals
 Phenotypic frequency- look at
outside appearance
 # of curved mouth / # of all
Population studies
 Look at 1 specific population and determine
16-2 Hardy-Weinberg Principle
 P2 + 2pq + q2 = 1
 Genetic Equilibrium- frequencies of alleles in
a population don’t change unless there is
evolutionary force acting
 What are the 5 things that have to be in place
to stay in Genetic Equilibrium? Pg 401-402
 If genetic equilibrium is in place or occurring,
then there is NO EVOLUTION!
 (this does not happen in the real world)
What cancels Hardy-Weinberg?
(What causes Evolution?)
 1. Mutations- from environment (chemicals,
UV) or spontaneous (cells)
 2. Gene Flow/Migration- changes which
genes are part of the frequencies used
 3. Non-random Mating- inbreeding, self-
fertilizing (plants), choosing specific mates
 4. Genetic Drift- random change in alleles
 Usually because of small populations
 5. Natural Selection- “Survival of the Fittest”
 Affects phenotypes
3 types of Natural Selection
 A. Stabilizing- favors average
 Ex: large spiders get eaten,
small spiders can’t get enough
 B. Directional- favors 1 extreme
 Ex: Woodpeckers with longer
beaks can reach more insects
 C. Disruptive- favors both
extremes, eliminates middle
 Ex: limpets: white blend in with
sand, dark brown hide on rocks, tan
are seen and eaten
Peppered Moths
16-3 Speciation- forming new
species (Microevolution)
 What is a Species?
 The morphological species-species are determined
by looking alike
 The biological species concept- Ernst Mayer says,
"Species are groups of interbreeding natural
populations that are reproductively isolated from
other such groups."
 How does it happen?
 -when the two species can no longer interbreed.
 A. Prezygotic Isolation (mechanisms take effect
before or during fertilization)
 1. Geographic/ Habitat Isolation: when a barrier or living in different
habitats prevents breeding
 ex: different species of manzanita shrubs live at different
altitudes and habitats
 Ex: earthquake that results in separation of species, Glaciers,
 Archipelagos- island chain some distance away from a continent
The division of a population, may form two new species.
Sympatric speciation - new species evolve from a single ancestral
species while inhabiting the same geographic region
Allopatric speciation - evolution of geographically isolated
populations into distinct species
2.Reproductive Isolation
 any heritable features of body form, functioning,
or behavior that prevent interbreeding between
 Temporal (Seasonal) Isolation: different groups
may not be reproductively mature at the same
season, or month, or year
ex: mating seasons of
frogs in north vs south
3. Behavioral Isolation: patterns of courtship may be altered
 ex: albatross courtship rituals- dancing birds, separates dogs from
4. Mechanical Isolation: reproductive organs prevent successful
ex: floral arrangements in sage plants discriminate between different bee pollinators
*Note: (2,3,4 can be overcome in the lab) = Hybrids
5. Gametic Isolation: incompatibilities between egg and sperm prevent
fertilization or the sperm is killed outright by the female reproductive
B. Postzygotic Isolation
(mechanisms take effect after
1. Developmental Isolation: Fertilization may occur,
but development of the embryo is irregular and
development is not completed.
2. Hybrid Inviability: Fertilization does occur between
different species, but the hybrid embryo is weak and
3. Hybrid Sterility: In some instances the hybrids are
vigorous but sterile
ex: mule produced by a male donkey and a
female horse
Models for Other Speciation
1. Polyploidy- inheritance of three or more of each
type of chromosome due to improper separation of
chromosomes during meiosis or mitosis
 example:
2. Parapatric Speciation- reduced gene flow within
the population, interbreed with local individuals
Artificial Selection/
Selective Breeding
 Breeding animals with desired characteristics
to produce the next generation
 Different breeds of dogs
 Super Cow
17.4 Patterns of Speciation
 Branching and Unbranched Evolution
 Cladogenesis applies to populations that
become isolated from one another and
subsequently diverge in different directions.
 Anagenesis is a pattern of descent in which species
form within a single, unbranched line.
Divergent Evolution
pattern in which species that once were all
similar become more distinct, species adapt to
different environments
1. Adaptive Radiation- many related species
evolved from a single ancestral species
 ex: finch beaks based on niche are all from 1
ancestral bird
Convergent Evolutionunrelated species become more similar in
appearance as they adapt to the same type
of environment
 Ex: fish and dolphins same body shape and
Coevolutiontwo organisms adapting together
 Ex: plants and animals that pollinate them
Evolutionary Trees and Rates
of Change
1. The gradual model of speciation is represented
by tree diagrams with branches at slight angles
to each other to show slow change over time.
 Ex: support from fossil record
2. The punctuation model of speciation is drawn
with short, horizontal branches that represent
abrupt periods of speciation followed by stable
 Ex: introduction of a new predator
 the processes outlined above, but is evolution
at taxonomic levels above the species level.
 occurs when evolution creates entirely new
adaptations previously non-existent
1. Structural- changes in the
structure of body parts
ex: thorns, spines of sea
urchins, mole rat (larger teeth &
 Mimicry- copy appearance of
another species
 Ex: moth wings look like eagle
 Camouflage- blend in with
 Ex: sand snakes, walking stick
2. Physiologicalchanges in an organisms metabolic
 Ex: bacteria resistance, weeds resistant to
Hox Genes
 Master control genes- control growth as an
embryo develops