Transcript Introduction to the course

Concepts of Biology II – 03-55-101-01
Class time: 4:00 – 4:50 PM Tuesday & Thursday
Place: 1120 Erie Hall
(but you’re here, so you know that)
Professor: Mike Weis
Office: Room 202 Biology Building
Phone: 253-3000 ext.2724
Email:
[email protected]
Office hours: Tuesday & Thursday 12:00 – 2:00 PM
(or by appointment)
Exams and Grading:
2 midterms during class hours and a final.
Midterm 1
Feb.10
25% of mark
Midterm 2
March 22
25% of mark
Final
April 25 noon 50% of mark
Exams will consist of (mostly) the various forms of
short answer questions (multiple choice, fill-in-theblank, matching, etc.) with a few questions requiring
written answers of no more than 1 or 2 sentences.
Midterms cover segments; the final is
comprehensive.
Scheduling conflicts concerning exams must be
reported to me at the earliest possible date, and
under no circumstances less than two weeks prior
to the exam.
Grades are non-negotiable. Mechanical errors in
grading will be rectified (i.e. addition errors)
There will be zero tolerance for cheating. Clear
evidence of cheating will be prosecuted to the full
extent allowed by university policies.
Here is a tentative schedule of lecture subjects:
1) Introduction to the course
Evolution:
1) Brief review of MendelianGenetics
2) Evidence of evolution
3) Population genetics and microevolution
4) Macroevolution: the evolution of species
Ecology:
1) The Biosphere and the Biomes
2) Population Biology
3) Community Ecology
4) Ecosystem Ecology
5) Behavioural Ecology
6) Conservation Biology
7) Applications of Ecology
Plant Anatomy & Physiology
13) Plant structure and transport
Animal Anatomy and Physiology
14) Circulatory System
18) The Senses
15) Immunity
19) Endocrine System
16) Excretory System
20) Human Reproduction
17) Nervous System
21) Muscular System
This schedule is subject to modification (time limits
may cause one or more subjects to be dropped),
and may be adjusted to allow for guest speakers.
Biology is the study of life. To know what we’re
going to study, we’d better begin with a ‘definition’
of life (the universal properties of living things):
Living organisms:
-are highly ordered
-reproduce (life originates from life)
-grow & develop (driven by heritable programs)
-utilize energy (take in and transform energy)
-respond to their environment
-regulate their internal environment
-evolve (i.e, change in response to interactions
between organisms and environment) at the
population level
Cells are living things’ basic units of structure
& function:
- all living things have an inside/outside boundary, i.e.
membranes that regulate passage of materials
between the cell & its environment
- the cell is lowest level of structure capable of
performing all activities of life
- all organisms are composed of cells, whether
unicellular or multicellular organisms
- all cells contain DNA at some stage
The Diversity of Life is categorized into 3 domains:
Two Prokaryotic domains –
the Bacteria and the Archaea
They have in common the lack of a membranebound nucleus and the lack of organelles
within the cells. They are generally unicellular.
One Eukaryotic domain –
protists (algae, amoeba, and many others),
fungi, plantae, and animalia
They have membrane-bound nuclei & internal
organelles. Some protists are unicellular; others
& the other groups are multicellular.
The Continuity of Life is Based on Heritable
Information in the form of DNA
-Watson/Crick double stranded DNA: a linear
sequence of four nucleotides arranged in genes
-biological structure and function is encoded in
genes, the unit of inheritance
-inheritance based on complex mechanisms to:
a) copy DNA
b) distribute DNA between parent and offspring
-all life forms use essentially the same genetic
code; diversity arises from different DNA
sequences
Similarities among all living things is best
explained by EVOLUTION:
It is the one unifying theme in Biology
-species change; contemporary species arise
from a succession of ancestors through
a process of “descent with modification”
(Darwin)
-a (and likely the most important) mechanism
of evolutionary change is natural selection
- a way to understand why natural selection is
so important: “adapt or die”- adaptation
provides the potential to survive &
reproduce in a given environment
Scientists study life in two ways:
1)By observation (what the text calls “Discovery
Science”, and what is elsewhere called descriptive
science)
Conclusions can be drawn from observation only
by means of induction. If we see the same thing
enough times, we begin to believe it is true. We
draw general principles from large numbers of
specific observations.
-- Or --
2) By using the hypetheco-deductive method (which
we usually call ‘The Scientific Method”). This
method begins with an observation. The scientist
then proposes and explanation for the observation
– the hypothesis – and designs experiments to test
his/her proposed explanation.
The process uses deductive reasoning. The test
makes (draws) an inference (a prediction) from
general premises (the proposed explanation) to
specific consequences, which logically follow if the
premise is true. The process is “If…then logic”
A useful hypothesis must be testable by hypotheticodeductive method. Testable here can be taken to mean
that the hypothesis can be (potentially) falsified by
tests.
If falsified, the hypothesis can be eliminated or (at
least) modified. But it can never be completely
proved.
When scientists have tried enough tests to believe that
the hypothesis is very unlikely ever to be disproved, it
is elevated to the status of theory.
The Hypotheco-Deductive Method:
How does the method work?
A well designed experiment has a control group
(one in which nothing is changed from the norm)
and one or more experimental groups, in each of
which a single variable is modified.
Note the underlined word ‘group’. Replication is
critical in science. Results of many (probably most)
experiments are examined statistically. A
significant result (meaning the variable you
modified is important) is a difference between
experimental and control groups that would occur
by chance alone less than once in 20 tries.
It is the prediction you made from your hypothesis
that determines what variable you modify for your
experimental group.
An example should clarify this:
In the British Museum is a long history of collections
of a moth called the peppered moth. Up until around
1700, moths were predominantly ‘peppered’, i.e.
whitish with mottled dark spots. There were a few %
that were dark coloured.
By 1850, moths were predominantly dark coloured,
with only a few % of the peppered type.
Around 1850, a British entomologist named J.W. Tutt
suggested that bird predators picked off peppered
moths from trees based on the contrast between their
coloring and the color of tree bark.
Logical, but was this hypothesis scientifically
correct?
In the 1950s, Bernard Kettlewell tested the hypothesis
in a controlled experiment. He grew both peppered
moths and a dark (melanistic) morph of this species in
the lab, then released them in two forested areas.
The two areas were:
A) in areas near Birmingham polluted over more
than two centuries since the beginning of the
industrial revolution. There the bark of trees was
blackened by soot.
and
B) in unpolluted areas of Dorset. There the bark of
trees was pale.
The difference should (logically) favor dark moths
near Birmingham, and peppered moths in Dorset.
Birds are visual predators; they capture moths during
the day, while the moths rest on tree trunks.
To ensure he wasn’t confusing his released moths
with natural populations, he marked each released
moth with a spot under the wing, where birds
couldn’t see it.
He set traps to catch the moths, and could determine
the number of each morph (dark vs. peppered)
predated in each environment.
Here are the fractions he re-captured:
Near Birmingham
In Dorset
peppered
19%
12.5%
dark
40%
6%
Kettlewell went one step further. He set up blinds in
both areas and filmed birds ‘choosing’ moths to eat.
The birds chose the ones that were most clearly
visible.
The effect on the evolution of moth pigmentation
frequency is called industrial melanism.
Here are the moths against the two backgrounds:
In Dorset
Near Birmingham
Finally, let’s look at Kettlewell’s work – what are the
experiments? Were there proper controls?
There were two experiment(s), replicated in each
locale. Control groups were more cryptic (blended
with the background) moths predicted to be less
predated; experimental groups are more contrasted.
In Dorset, without heavy pollution, the peppered
morph is the control. Was the percentage recaptured
similar for control and experimental groups?
Control: 12.5%
Experimental: 6%
In Birmingham the groups are reversed. Dark morphs
are the controls.
Control: 40%
Experimental: 19%
In both places, it turned out that there were
significant differences in the percentage of released
moths recovered, and other evidence (observations
from blinds) that the reason was bird predation.