Download Evolution - West Ada

Evolution
• Bottom line : Evolution is descent with
modification. The environment selects
who is fittest, which allows them to have
more offspring. Over time these
inherited traits become more common in
a population (remember populations?).
Charles Darwin was one of the first to
describe it. It is a theory because it has
massive scientific support with None
disproving it. It has nothing to do with
religion.
I. Charles Darwin – 1809 – 1882
A. See WOTD for early life
***Had a wicked beard.
B. Many observations leading to Evolution
theory from 1831 Journey on the Beagle
(naturalist voyage)
1. Many observations from Galapagos
Islands.
2. Difference in finch
beak shape suggested
evolution to suite
different islands.
a. Similarities
between finches
suggested common
ancestor.
C. Didn’t publish his book “On the Origin of
Species” until 1859.
1. Proposed the theory of Natural Selection (a
driving force of evolution) = Those best
adapted to an environment, live and pass on
inherited traits.
a. These “traits” can be physical or behavioral.
b. This Natural selection causes species to
change over time.
c. Natural selection causes an “arms race”
between competitors or predator/prey
relationships….Antelopes and Lions are an
example.
d. Natural selection requires Natural Genetic
Variation to work.
2. Fitness is the ability to survive and pass on
ones genes. Yellow toothpicks more fit than
blue toothpicks in our particular environment.
a. Fitness determined by the Environment.
3. This all means that Darwin’s theory depends
on more offspring being born in a population
than can survive (Some must die).
D. Evidence for Evolution.
1. Fossil record – Using geologic dating one
can observe changes to a population over
time.
2. Geographic Distribution of living Species
1. Organisms in similar climates (on
different continents) have similar
adaptations)
3. Homologous Body Structures – Structures
from same origin with different function =
wings and arms.
4. Similarities in early development. See Pic.
II. Evolution in
Populations
A. Genes and
Variation.
1. Gene Pool
a. Remember
members of a
population
are all of
members of
the same
species.
2. Sources of genetic variations.
a. Mutations – change in DNA due to a “mistake” in
DNA.
b. Gene Shuffling – Each human can produce 8.4
million combinations of genes in sex cells.
i. That means the chances of having an Identical
non-twin is Ridiculously Low (almost infinitely
low.
c. Single-gene and polygenic traits.
1. Single-gene traits are simple. Ex. Widow’s
peak.
2. One gene determines trait
3. Polygenic traits –
many genes for 1
trait.
a. Phenotypes (the
way the traits look)
in a population best
shown as a bellshaped curve.
B. Evolution as Genetic Change –Evolution acts
on Physical traits, but those traits have genetic
origins = NATURAL SELECTION
1. Natural selection of Polygenic traits= three
general effects.
Or……………………
Or………………….
a. Directional selection- individuals at only
one end of a bell curve of phenotype
(traits) frequencies have high fitness.
i. Result = population becomes more
like that extreme.
b. Stabilizing selection – When individuals with
and average form of a trait have the highest
fitness.
i. Result = population becomes more
“average” less diverse.
c. Disruptive Selection – When individuals at
upper end and lower end of curve have
highest fitness (ie. Average is least fit).
i. Result= Speciation …population evolves in
two different directions = finches with short
parrot-like beak and others with long, narrow
beak.
2. Genetic drift – another evolutionary force
apart from Natural selection.
a. When an individual leaves more offspring
in a population due to simple Chance.
b. Happens only in populations with small
numbers.
c. Founder effect- genetic drift in which a new
habitat is colonized by a few individuals. Their
genes will be dominant regardless of fitness.
C (capitol C). The process of Speciation
1. Isolating mechanisms- how populations
become reproductively isolated (essential
factor for forming new species) from each
other. 3 types
a. Behavioral Isolation (courtship)– 2
populations capable of mating but do not due
to behavioral (eg. Courtship) differences.
b. Geographic Isolation (space)– populations
become separated by mountains, rivers bodies
of water etc.
c. Temporal Isolation (time)– populations that
begin to reproduce at different times.
i. if some flowers begin to open at midday and
other flowers at night, they will not breed.
2. Speciation of Darwin’s Finches – How it
happened in order.
a. Founders arrive – Some finches blown in
from mainland = Founder Effect
b. Separation of populations by Geographic
Isolation (different islands)
c. Changes in gene pool due to natural selection
= Directional Selection dependent on
environmental pressures unique to each island
(beak shape for different foods).
d. Reproductive Isolation – immigrating birds
now have different courtship behaviors
(Behavioral Isolation) = no interbreeding.
e. Ecological Competition – These new separate
populations (even on same island) have
different niches = differences broaden
f. Continued Evolution – finally led to 13
different species of Galapagos Finches.
i. Darwin’s finches are an excellent example of
speciation.
III. Classifying organisms (Taxonomy)
A. Linnaeus’s system of classification
1. Carolus Linnaeus (1707-1778) developed
the universally accepted method of
Binomial Nomenclatue.
a. The seven categories used by
Linnaeus from most exclusive to
most general are…..
1. Species
2. Genus
3. Family
4. Order
5. Class
6. Phylum
7. Kingdom
b. In his binomial nomenclature one includes
both the genus and species in the name.
i. The name is in italics
ii. Genus is capitalized while species is lower
case.
Homo sapein
iii. Example, you are a Homo sapien
(homo=genus and sapien is species).
iv. Any genus has multiple species
a. example: Homo sapiens = humans, Homo
neanderthalensis = neanderthal man, Homo
erectus = First upright ancestor of man etc.
Meet the
Homos
2. Example of classification = Brown bear
STOP – Draw Fig 18-5 here pp.450 (it’s on the
test).
B. Examples from the taxonomic categories.
1. Domain (even more general than kingdom)
there are three. **Oh, one thing all domains
have in common (All living things) is they
have DNA and RNA to pass on information.
** Three domain system based on how long
each has been evolving independently
** Domain was added after Carolus Linnaeus
developed his binomial system.
a. Bacteria – are bacteria ;-)
i. The Domain Bacteria contains only
one kingdom which is Eubacteria.
ii. All bacteria are unicellular (one cell)
iii. Bacteria are single celled prokaryotes
(have no nucleus)
iv. Peptidoglycan in cell walls (just know it).
b. Archaea – extremeophiles – live in Really
extreme (salty, hot, low oxygen etc.)
environments.
i. all are unicellular (one celled)
ii. Archaea are Prokaryotes (have no nucleus).
iii. NO peptidoglycan in cell walls (how they
differ from bacteria)
c. Eukaryotes – everything else (Plant kingdom,
Fungi kingdom Protista kingdom, and Animal
kingdom. (gagillions of different species)
• i. All eukaryotes have a nucleus within each
cell.
2. Kingdom –The next most general taxonomic
category
a. Eukaryote Domain includes the Kingdoms: ,
Fungi (mushrooms molds), Animalia (us),
Plantae (green stuff), and Protista (ameoba).
(billions of different species)
**Random stuff you must know about
Eukaryotic kingdoms
i. Organisms in Fungi have cell walls made of
chitin and are heterotrophs (must
consume food) ((random fact you must
know)).
ii. Animals are heterotrophs.
iii. Plants are autotrophs (photosynthesize).
** Plant cell walls made of cellulose.
3. Phylum – each kingdom contains several
phylum.
a. Within kingdom Animalia we are in the
phylum Chordata (have spinal cord)
(millions of different species)
4. Class – Each phylum contains several classes
a. We belong to the class Mammalia (Warm
blooded, have body hair, produce milk for
young).
(hundreds of thousands of different species)
5. Order – Each class has many orders
a. we are in order primates (with all monkeys
and apes)
(thousands of species)
6. We are in the family Hominadae (with gorillas,
chimps, orangutans and our dead ancestors).
7. We are in genus Homo (we are the only living
Homos…..stop laughing) Eg. Homo erectus
8.Our species is Homo sapein (we are the only
one)
C (capital C) Dichotomous Key
1. Dichotomous Keys are used to classify
organisms beginning at the very general
taxonomic catagories (example: Kingdom) to
the most specific (species).
2. Each step asks an either or question.
Example:
a. Does the organism have a nucleus?
-If no, continue to question b. If yes, it is a
Eukaryote continue to question c.
b. Does it have peptidoglycen in it’s cell walls?
- If no continue to Archae
-If yes continue to Bacteria
Eukaryotes
c. Is it a single celled organism?
-if yes, it is a Prokaryote continue to question …….
-if no, proceed to question…………..
•The End- but not really
because evolution
continues. ;-)