Download 6 II. Science and Evolution A. Characteristics of a good scientific

II.
Science and Evolution
A.
Characteristics of a good scientific theory
1.
TESTABLE: Must make predictions; must be falsifiable
a.
Karl Popper: One cannot prove something is true, but can prove
that something is false
b.
Methodology
(1)
Null hypothesis
(a)
What is tested/rejected
(b)
Example: APenicillin has no effect upon bacterial
infections@
(2)
Control
(a)
Standard of comparison
(b)
Experimental treatment omitted
(c)
Placebo: Inactive substance
(d)
Placebo Effect: Response to act of being treated
(3)
Variables
(a)
Independent
i)
Affects something
ii)
X-axis
(b)
Dependent
i)
Affected by independent variable
ii)
Y-axis
Picture Slide #1: (A) Growth of the larval stage of a tapeworm in an intermediate host (mice) (B)
Growth of infected and uninfected hosts (mice). Fig. 1-3 in handout Smith (1994)
2.
Repeatable
a.
Others get similar results
b.
Data are reliable, not faked
3.
Stable: Theory unchanged after repeated testing
4.
Simple
a.
Parsimony
b.
Ockham=s Razor: If 2 hypotheses explain the facts, choose the
most simple
c.
Doubt hypotheses with many exceptions
5.
Non-authoritarian
a.
Authoritarian: The world is round because . . .
(1)
My parents told me
(2)
My teacher told me
(3)
My textbook says so
b.
Rational (= non-authoritarian): The world is round because . . .
(1)
The earth=s shadow on the moon is round
(2)
The last structure seen as a ship sails below the horizon is
the tallest mast.
6.
No retro-fitting
a.
Technique used by Apsychics@
6
APsychic@ makes a general statement
(1)
ASomeone you care about is ill@
(2)
AYou are thinking about making a change in you life.@
c.
Victim supplies the specific answer.
(1)
Almost everyone knows somebody ill
(a)
Uncle Bob broke his leg
(b)
Aunt Betty has cancer
(c)
My parasitology teacher should lower his
cholesterol.
(2)
People constantly daydream about . . .
(a)
Taking a neat vacation
(b)
Getting a better job
(c)
Breaking up with his/her significant other
d.
APsychic@ police investigation Aclues@
(1)
Information offered before criminal does not facilitate
solving the crime
(a)
AI see the color red.@
(b)
AI see the number 7"
(c)
AThere is water@
(2)
After crime solved by traditional methods, Apsychic@ claims
his/her clues were accurate descriptions
(a)
The criminal was wearing a red shirt, driving a red
car, lived in an apartment with a red door when
caught
(b)
The criminal lived near a 7/11, near Highway 73,
was caught on the 17th day of the month, had a
birthday in July.
(c)
It was raining the day of the arrest, there was a lake
or stream nearby, someone was watering their lawn,
the criminal was taking a shower.
Supported by convergence of independent evidence
a.
Murder investigation
(1)
Suspect threatened victim in a letter
(2)
Murder weapon found in suspect=s home
(3)
DNA testing: Blood on suspect=s clothes matches that of
victim
(4)
Footprints at crime scene match those of suspect
(5)
Witnesses saw suspect=s car at crime scene
b.
Evolution supported by information not known in Darwin=s
lifetime
(1)
Fossil record records changes
(2)
Radio-isotope dating confirms age of earth
(3)
Nuclear physics/theory of relativity/constant speed of
light/astronomical observations confirm that universe/solar
b.
7.
7
system is old enough for evolution to have occurred
(4)
Continental drift
(5)
Mendelian genetics explains variation in populations
(6)
Molecular biology
(7)
Cladistic analysis
B.
Basic Concepts of Evolution
1.
Individuals within populations have different traits = variation
a.
Mutation creates new genes
b.
Crossing over and independent assortment during meiosis create
new associations/combinations of different genes
2.
Genes enabling bearers to have more offspring become common in gene
pool.
a.
Less than 1% of all organisms that are born ever reproduce
b.
Maladaptive genes are REMOVED from gene pool of population
Picture Slide #2: Far Side Cartoon
3.
Reproductively isolated groups eventually split into new sibling species
4.
Mechanisms
a.
NATURAL SELECTION
(1)
Genes removed from population
(2)
Death before reproduction
b.
SEXUAL SELECTION
(1)
Females often choose male mate
(2)
May lead to exaggerated traits (= bright plumage) that
increase risk of predation for male.
C.
Misconceptions about evolution
1.
ASurvival of the fittest@
a.
Inexact and trite
b.
Viable offspring much more important that simply Asurviving@
2.
Modern species are more Aadvanced@ or Abetter adapted@ than extinct
species
Picture Slide #3: Far Side Cartoon
a.
Many large scale extinctions were caused by extraordinary events
to which organisms had no chance to adapt
(1)
Asteroid impacts
(2)
Sudden drastic changes climate due to continental drift
influencing oceanic currents
b.
Dinosaurs were well-adapted to their environment
3.
Over evolutionary time, species tend to increase in complexity
a.
Jettisoning a trait may increase energy available for reproduction
b.
Comparisons between parasites and their free-living relatives
indicate that many parasites have lost some structures (=
Tapeworms are without a gut.)
c.
Traits are continually being gained AND lost over evolutionary
time
8
4.
Parasites are degenerate organisms that are significantly less complex than
their free-living relatives
a.
Parasites acquire traits different from free-living relatives which
enable them to complete their life-cycles.
(1)
Infect new hosts
(2)
Avoid host=s immune system
b.
In many traits, parasites are more complex than their free-living
relatives.
(1)
A typical trematode life-cycle can involve living in a
vertebrate, a mollusk, and an arthropod
Picture Slide #4: Life-cycle of a typical trematode worm.
(2)
Tapeworm integument is covered with microvilli that
absorb nutrients
D.
Non-scientific hypotheses
1.
Intelligent design (= ID)
a.
Argument for
(1)
Metabolic pathways, organisms, life-cycles are intricate
and complicated
(2)
Therefore, they MUST have been designed or created by a
powerful superior being.
Picture Slide #5: Life-cycle of a butterfly; an example often used by creationists to support
Intelligent Design Theory.
b.
Arguments against
(1)
Too many Apoorly@ designed structures
(a)
Connection between respiratory & digestive tracts
of vertebrates
(b)
Neurons of vertebrate eye lie between incoming
light and sensors
(c)
Human head does not pass easily through birth
canal
(2)
Is ID a blasphemous concept?
(a)
Most (2/3s) organisms are parasites
(b)
Parasites are Awell-designed@ to infect hosts
(c)
Parasites have been Awell-designed@ to live inside
hosts
(d)
Suffering induced by Aintelligently designed@
presents a moral dilemma
Picture Slide #9: Human Schistosomiasis caused by a “well-adapted” trematode
TELEOLOGY
2.
a.
Defined: Attributing purpose to descriptions of natural events
b.
Not testable
c.
Examples
(1)
Divine punishment for immoral life-style
(a)
Hurricanes hit Florida/Gulf Coast because voters
9
3.
legalized gambling
(b)
Diseases such as AIDS and STDs
(2)
Giraffes have long necks in order to eat leaves at the top of
trees
(3)
Since large snails are more likely to be seen and eaten by
predators, it is beneficial for the snail population to produce
a supply of large snails for this purpose in order that the
small snails (= next generation) are not eaten
ANTHROPOMORPHISM
a.
Defined: Attributing human emotions to animal activities and
behaviors
b.
Examples
(1)
Mother lion loves her offspring so much that she will risk
her life to defend them
(2)
Porpoises like humans
(3)
Female snail wants to lay her eggs in the best location for
survival of her offspring.
10