Transcript Biol 100: Lecture 1 - Tacoma Community College

Lecture 1: Intro to Plants, Intro
to Science
Why do we love plants? What makes them so special?
Plants are:
 Beautiful
Unusual
Complex
Diverse
They feed us!
They are the lungs of the earth
They have charted the course
of human settlement on earth
(grasses).
They put a roof over our heads
Many have greatly impacted
history
Pyrola asarifolia
http://www.pbase.com/rodg/western_wa
shington_native_plants
People and Plants
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We affect each other. – how?
»We can’t live without them!
»They exchange CO2 for O2 – mitigates greenhouse
effect.
»We destroy, pollute their habitat, causing extinction
»They can destroy habitat, harming our economy –
invasive plants!!
»We can alter the course of their evolution, through:
–Gm crops, conservation genetics, selective
breeding
Plants are sources
 of
food
 of paper
 of fibers
 of medicines
Life without
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chocolate
sugar
vanilla
cinnamon
pepper
wood
cotton
linen
roses
paper
oxygen
THE PROCESS OF SCIENCE
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The word science is derived from a Latin verb
meaning “to know”
» Science is a way of knowing
» Science developed from our curiosity about
ourselves and the world around us
The Process of Science:
"The Scientific Method"
Observe the Natural
World
Ask Q uestions about what you see
Develop on e or more testable hypotheses
Test the hypothesis
Communicate results
What’s a Scientific Question?
 Scientific
Questions are….
» Testable
» Definable
» Measurable
What’s a Hypothesis?
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Tentative, but untested explanations
» Ex. Tree height is limited by N availability
Make predictions that can be tested
» Predictions written as “If [hypothesis], then……”
statements
» Ex. If tree height is limited by N availability, then
adding N to the soil should cause the tree to grow
taller
How do you test a Hypothesis?
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Via controlled experiments or pertinent observations
» All variables must be controlled
Kinds of variables:
» Independent variable - the thing (variable)
studied, manipulated or tested
» Dependent variable - the thing(s) affected by the
independent variable. What you measure!
» Controlled Variables - All other things
(variables) that you try to hold constant
Experiments of classical design
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Individuals studied divided into two groups
» Experimental group
– exposed to the independent variable
» Control group
– exposed to the identical conditions as the
experimental group, but not be exposed to the
independent variable
The Process of Science in Action
•
Biology in the news: From npr.org
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Harvard scientists found people who ate bacon at
least five times a week were 59% more likely to
develop bladder cancer than those who never did.
Chemicals called nitrosamines and heterocyclic
amines may be to blame. The study appears in the
American Journal of Clinical Nutrition. The
Harvard team studied data on nearly 136,000
people. The participants were followed for up to 22
years, during which time 808 developed bladder
cancer.
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However, the research is far from definitive. The
researchers also found people who ate bacon and other
processed meats frequently were also more likely to smoke
and to take in more fat and fewer vitamins. They were also
less likely to exercise. Dr Emma Knight, science information
manager at Cancer Research UK, said: "The link between
diet and cancer is complex and difficult to unravel but we
know that eating lots of red and processed meat can
increase our risk of some types of cancer. "More research
is needed before we can say for sure whether or not eating
bacon in particular affects bladder cancer risk. "For now,
our advice remains to eat a balanced diet that is low in fat,
processed and red meat, and rich in vegetables, fruit and
fibre." More than 10,000 people a year are diagnosed with
bladder cancer in the UK
How does science really work in
today’s world?
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Exhaustive literature search + observations 
 hypothesis
Prediction
Write a proposal, design experiment
Get money $$$$$
Revise proposal based on $$$
Experiment/collect data
Statistics
Write manuscript of results
Publish or perish
Hypothesis vs. Theory vs. Law?
A
fact leads to a law, eventually.
 What is a law?
 Phenomenon that is invariable – is
always true
 Based entirely on observations, no need
for testing
 Example of a law?
ice floats
gravity
What happens if all of our experiments fail to
negate our hypothesis?
 What if workers in other parts of the
community, county, state, country, or world
also fail to negate your hypothesis?

Theory
A well-tested explanation of the observations
(never been proven false.)
 We arrive at theories by scientific method
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To Prove or Not to Prove
Experimentation can either support or reject a
hypothesis.
 Experimentation can never prove a hypothesis
100% correct. – why?
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After each each experiment we need to reevaluate our results and observations to either
make changes in our hypothesis or more likely
design a new experiment.
Which end of a plant is up?
Cells
Muscle cell
Tissues
Muscle tissue
Organs
Heart
Systems
Circulatory
system
Parenchyma cell
Dermal tissue
Leaves
Shoot
system
Three organs: Roots, stems, leaves
1.
Roots–
• Collect water & minerals from soil
• Anchor plant
• Store food (carbos from photosynthesis)
to be used for flowering & fruiting
• Covered with root hairs – increased
surface area for absorption
Sweet Potato –
storage root
Modified
Aerial strangler roots
Roots –
Prop roots
Buttress roots
Pneumatophores
2. Stems/shoots
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Support, transport
Some photosynthesis
Two types of shoots
1. Vegetative – leaves only
2. Reproductive – produces flowers
Two parts of stem:
1. Node – point of leaf attachment
2. Internode – stem segments between
nodes
Two types of buds
1.
2.
Terminal bud – contains a shoot apical
meristem; shoot growth is concentrated
here
Axillary buds – in angle (axil) between leaf
& branch, contain meristem with potential to
become a vegetative shoot. Mostly
dormant.
Apical dominance = the presence of an apical
bud inhibits the growth of axillary buds.
-remove or depress apical bud, axillary buds
begin to grow.
Modified Shoots (stems):
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Stolons – above-ground
runners
Rhizomes – below-ground
runners
Bulbs – swollen
underground shoots
Tubers – swollen rhizomes
Asexual,
vegetative
propagation
Stores food
for later
growth
3. Leaves – main photosynthesis organs
•Petiole
•Blade
http://www.knotweed.co.uk/japknot_Inf
Modified
leaves
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Compound, doubly
compound – why??
Tendrils
Modified
leaves
Spines
Succulents
Leaf types:
Simple leaf = undivided but may be lobed,
serrated, cleft, etc.
Compound leaf = divided into distinct units called
leaflets
Four types of leaf arrangement:
1. Acaulescent – leaves arranged in a basal
rosette, not attached to a stem.
2. Alternate – leaves borne single at each node
along the stem
3. Opposite – leaves borne across from each
other at the same node
4. Whorled – 3 or more leaves arising from the
same node.