Download Evolution - Angelfire

Evolution
The quick view (which is opposite
of how evolution works, so it’s
kind of ironic eh?
Science vs. Religion
What is science based on?
 Science is based on OBSERVABE evidence.
 What is religion based on?
 Religion is based on FAITH.

– By definition, faith is something that is not
observable.

Since they are 2 different “fields,” they
aren’t really competing with each other
Religious Scientists?

My religion consists of a humble admiration of the
illimitable superior spirit who reveals himself in the slight
details we are able to perceive with our frail and feeble
mind.
– Albert Einstein (1879 - 1955)

Science without religion is lame, religion without science
is blind.
– Albert Einstein (1879 - 1955), "Science, Philosophy and Religion:
a Symposium", 1941

Not only does God play dice, but... he sometimes throws
them where they cannot be seen.
– Stephen Hawking
Evolution is a Theory

To paraphrase Carl Sagan:
– Creationists think that a theory is something
that you made up while drunk one night.
 Theory Defined: “scientific principle to explain
phenomena: a set of facts, propositions, or
principles analyzed in their relation to one
another and used, especially in science, to
explain phenomena”
– MSN Encarta, http://encarta.msn.com/dictionary_/theory.html

Evolution is as much a theory as gravity is
A Final Quote
In
the immortal
words, of “The
Gru:”
–“Be opinionated,
just not
ignorant.”
Dating

Geologic Record
– Hypothetical library of all the known geological
processes on Earth
– Determined through inference and dating methods

Relative Dating (hee hee)
– Sediments are constantly being laid down.
– Over time, many layers form
– If a fossil is in a layer below a different fossil, it is
older than that fossil
Dating

Radiometric Dating
– Radioactive isotopes decay
and form new isotopes - the
rate this happens is called the
isotope’s half life
– Ex: Potassium-40 decays to
argon-40 and has a half life of
1.3 billion years
 Half a sample will decay to
argon-40 in 1.3 billion years
 So if there are equal amounts
of potassium-40 and argon40 in an area, the sample has
been in place 1.3 billion years
– Carbon 14 has a half life of
only 70,000 years for more
recent sample dating
Review
1.
2.
3.
4.
How does the geologic record help us?
What use is relative dating?
What is radiometric dating?
Why are different isotopes used in
radiometric dating?
Charles Darwin


English naturalist (scientist)
1809-1882
1831, Darwin took a job as a
naturalist on the HMS Beagle
– Went on a 5-year scientific
journey around the world

He collected many biological
and fossil speciments
– Combined with his previous
and subsequent observations

Published On the Origin of
Species by Natural Selection
in 1859
– These ideas are a basic
unifying theme of biology today
– Without evolution, biology
doesn’t make as much sense
Selection

Artificial selection
– Breeding organisms with specific
traits in order to produce
offspring with identical traits

Natural selection
– A mechanism for change in
populations
– Occurs when organisms with
favorable traits survive,
reproduce and pass their traits on
to the next generation
 Organisms with these traits are
said to be more “fit”
 Organisms without these traits
are less likely to survive and
reproduce
Darwin awards
Adaptations

Adaptation
– Evolution of a structure,
behavior, or internal process
that enables an organism to
respond to environmental
factors and live to produce
offspring
– Can also be the structure
itself
Structural adaptations take
a long time
 Physiological adaptations
can happen faster

– Bacteria strains develop
resistances to antibiotics
fairly quickly
Evidence for Evolution

Fossil Record
– A hypothetical “library”
of all the fossils
collected around the
world

Fossils show changes
throughout time
– 99 percent of all
animals are now
extinct
– Fossil record shows
ancestors with similar
characteristics
Evidence For Evolution


Anatomy
Homologous Structures are
structural features with a
common evolutionary origin
– Ex: whale forelimb, crocodile
forelimb, bird wing, human
forelimb all look the same (p.
401)
– Can you think of other examples?

Analogous Structures are body
parts or organisms that do not
have a common evolutionary
origin but are similar in function
– Bird, bat and butterfly wings
– Show how organisms adapt to
different ways of life and
different conditions
Evidence for Evolution

Vestigial Structures
are body structures
that no longer serve
their original purpose,
but was probably
useful to an ancestor
– Ex: human appendix,
pelvic bone in baleen
whale, “tail” in
humans, some
human’s ability to
wiggle their ears
Evidence for Evolution
Embryology – study
of embryos of
different species
 Many species share
features in the young
embryos

– Ex: Mammals, reptiles,
birds and fish all have
a tail and pharyngeal
pouches (develop into
different respiratory
systems)
Evidence for Evolution
Biochemistry
 Nearly all organisms
share DNA, ATP, and
many enzymes
among their
biochemical molecules
 Organisms that share
more similar
enzymes, DNA
sequences, etc. are
more closely related

Review
1.
2.
3.
4.
5.
6.
How did Darwin come up with his ides for natural
selection?
Some snakes have vestigial legs. Why is this
considered evidence for evolution?
Explain how adaptations such as camouflage help
species survive.
How do homologous structures provide evidence for
evolution?
Why did birds and bats both get wings?
A parasite that lives in red blood cells causes the
disease called malaria. In recent years, new strains of
the parasite have appeared that are resistant to the
drugs used to treat the disease. Explain how this could
be an example of natural selection occurring.
Population Genetics
Populations evolve,
not individuals
 Natural selection acts
on a range of
phenotypes in a
population
 Evolution is often
defined as a change
in the frequency of an
allele in a population
over time

Population Genetics
All of the population’s
genes are in a theoretical
“gene pool”
 The percentage a specific
allele in the gene pool is
called the allelic frequency
 A population in which the
frequency of alleles
remains relatively the
same over generations is
in genetic equilibrium
 Any change in this genetic
equilibrium results in
evolution

Hardy-Weinberg Principle

1.
2.
3.
4.
5.
How to Stop Evolution – must meet all five
requirements
Population is so large, chance alone cannot
change relative frequency (genetic drift doesn’t
occur)
Mutations do not occur
All genotypes have equal fitness (no natural
selection)
No organisms leave or enter a population
Mating occurs at random
Mutations

Mutation provides the
raw material for
evolution to act upon
– Poor mutations are
selected against, good
mutations are selected
for
– Change the frequency
of alleles
– Examples:
Genetic Drift
Genetic drift is the
alteration of allelic
frequencies by chance
events
 Genetic drift can greatly
affect small populations

– Ex: The Amish
community carries an
allele that results in short
arms and legs and extra
fingers and toes (1/14
vs. 1/1000)
Natural Selection
Still the most significant
factor that causes changes in
established gene pools
 Stabilizing Selection

– Natural selection that favors
average individuals (on a
normal curve) in a population
– Reduces variation in a
population
– Ex: With spiders, larger ones
are found easier and eaten and
small spiders can’t find food as
easily
Natural Selection

Directional Selection
– Natural selection favors one of
the extreme variations of a trait
– Can lead to rapid evolution
– Ex: The food supply in an area
is limited to hard nuts. Birds
with short, strong beaks will
survive

Disruptive Selection
– Natural selection favors
individuals with either extreme
of a trait’s variation
– Can lead to evolution of 2 new
species
– Ex: A shelled, marine organism
called a limpet has white, tan,
and dark shells. The white and
dark shells blend in on different
colored rocks. Tan gets eaten.
Species
A species is a group of
organisms that look
alike and can interbreed
to produce fertile
offspring in nature
 Speciation is the
evolution of new species

– Occurs when members of
similar populations no
longer interbreed to
produce fertile offspring
within their natural
environment
Causes of Speciation

Physical barriers
– Volcanic eruptions,
sea-level changes,
new islands forming
These prevent
interbreeding
 Called geographic
isolation
 Over time, may have
to adapt to new types
of environments

Causes of Speciation
Reproductive Isolation
 Two types

– One occurs because of
geographical reasons
(migrate away)
– One occurs because of
behavioral reasons
 Some mate in fall, some
in spring
Polyploidy
Individual with a
multiple of a normal
set of chromosomes
 How does this
happen?
 New zygotes may not
develop the same way
as parents due to
different number of
chromosomes
 May result in
speciation

Gradualism
James Hutton &
Charles Lyell
 Theory that processes
are moving at the
same speed today as
in the past
 Suggests that the
Earth is very old –
4.55 billion years
 Also suggests that
evolution occurs
constantly, but slowly

Punctuated Equilibrium
Remember first day of
class?
 Niles Eldredge and
Steven J. Gould
 Theory that speciation
occurs relatively, in rapid
bursts, with long periods
of genetic equilibrium
inbetween
 Might occur due to
drastic environmental
changes resulting in
quick adaptations

Adaptive Radiation


When an ancestral species
evolves into an array of
species to fit a number of
diverse habitats
Hawaiian Island
honeycreepers
– Similar in body size and shape,
but different sharply in color and
beak shape
– Adapted to occupy different
niches (what’s a niche)
Divergent Evolution

Adaptive radiation is a
type of divergent
evolution
– The pattern of evolution in
which species that once
were similar to an ancestral
species diverge, or become
increasingly distinct

Galapagos Finches
– Similar changes for finches
that ended up on different
small islands
Convergent Evolution


A pattern of evolution in
which distantly related
organisms evolve similar
traits
Occurs when different
organisms occupy similar
environments
– Adapt similar traits

Example:
– Organ pipe cactus in N.
and S. American vs.
Euphorbiaceae in African
deserts both look very
similar
Review
1.
2.
3.
4.
5.
6.
Explain and illustrate why the evolution of resistance
to antibiotics in bacteria is an example of directional
natural selection.
How can geographic isolation change a population’s
gene pool?
Why is rapid evolutionary change more likely to occur
in small populations?
How do gradualism and punctuated equilibrium differ?
How are they similar?
Hummingbird moths are night-flying insects whose
behavior and appearance are similar to those of
hummingbirds. Explain how these two organisms
demonstrate convergent evolution.
What is divergent evolution? How does it compare to
adaptive radiation?
Quick Tour of Ch 17



Classification – the grouping
of objects or information
based on similarities
Taxonomy – the branch of
biology that groups and
names organism based on
studies of their different
characteristics
Aristotle was the first on
record
– Classified organisms into
two groups: plants and
animals, each with
subgroups
Carolus Linnaeus
Developed taxonomic system
still used today
 Based on physical and structural
similarities of organisms
 Grouped life into 7 taxa (groups)
– What are they?
 Kingdom, phylum, class, order,
family, genus, species
 Five Kingdoms: animals, plants,
fungi, protists, monerans
 A six Kingdom system is
becoming more and more
common: monera split into
eubacteria and archaebacteria

Binomial Nomenclature
All organisms have a two-word name
 Consists of their genus and their species

– Always italicized in type and underlined in
writing

Genus is capitalized, species is lower case
– Homo sapiens (human)
– Passer domesticus (sparrow)
Classification Key
Sometimes called a
dichotomous key
 “Guide” for identifying
different species
based on observable
traits
 Useful for
distinguishing
between types of
organisms

Modern Classification
Generally based on
evolutionary
relationships vs.
physical characteristics
 Used structural
similarities, breeding
behavior, geographical
distribution,
chromosome
comparisons,
biochemistry to figure
out relationships

Phylogenetic Diagram

Monerans evolved first
(often broken up into
archaebacteria and
eubacteria)
– prokaryotes

Protists then evolved
– Single celled eukaryotes
– Three general kinds of
protists: fungus like,
animal like and plant like

Fungi, Plants and
Animals evolved from
the types of protists
Review
1.
2.
3.
4.
5.
Why does your book use the
classification system of six kingdoms
instead of five?
What two taxa does binomial
nomenclature consist of?
Why is classification hard to do?
What are the 7 Linnaean taxa?
How might you use taxonomic key to
figure out the name of an organism?