Transcript 1.1 What IS Science??

1.1 What IS Science??
Science is NOT:
•a static, unchanging group of facts or beliefs.
Science IS:
•a process of inquiry about how nature works.
•a body of expanding knowledge about nature
•a way of observing, thinking and knowing the
workings of nature
•Most importantly, a PROCESS
What is the GOAL of Science??
• provide explanations about how nature works
Ex: why do monarch butterflies only eat milkweed?
how do our cells “know” to express some of its DNA
and not all of it?
why can a virus only get into one type of cell?
• scientific knowledge:
1.Cure disease, place satellites in orbit, clean toxic waste, etc
2.Raises more questions than answers
3.Is a never-ending inquiry
What is involved in the PROCESS of science?
method of scientific inquiry = a logical way to solve a problem/answer a question
1. Observe/ask questions (“Why is this happening?”)
2. Infer answer/make a guess (hypothesis) (“Maybe because of…”)
3. Design a controlled experiment to test your hypothesis
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Independent variable: the deliberate change in the experimental group
(aka the manipulated variable) X AXIS
•
Dependent variable: what is observed/measured/changed in response
to the independent variable (aka resulting variable) Y AXIS
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Control group – exposed to all the conditions as experiments EXCEPT
the one independent (manipulated ) variable
4. Collect/Analyze Data
* Quantitative – measured numbers
* Qualitative – descriptive observations
5. Make conclusion: to support, revise, or refute original hypothesis
Theory = many related hypotheses tied together, backed by many studies and data
Ex: theory of relativity or theory of evolution
The Dominant Theory is the most widely accepted theory (explanation)
Science/Society/Technology/Ethics
Ex: thalidomide, DDT, super bugs and bio weapons, cloning of tissues or animals
1.3 Biology is the Study of Living Things
Q: What defines a living thing? What must it do?
A: Must have all 8 of the following characteristics of living things:
1. made of at LEAST one cell
ex: a bacterium is one single cell
* a cell is the smallest unit that is considered living
2. have a genetic code written in the language of DNA
ex: every living thing has DNA as its genetic blueprint
3. can obtain and use materials and energy
ex: materials and energy are used to grow and reproduce
ex: all the chemical reactions in the cell = metabolism
4. can grow and develop (growth = size; develop = change)
ex: fertilized egg  9 months to a trillion cells, specialized
ex: cell differentiation is the KEY to correct development
* cells specialize their traits and abilities (muscle, nerve, eye)
* certain cells must also DIE on time to make new structures
8 Living Characteristics cont’d
5.
Can reproduce
ex: sexual: union of 2 DIFFERENT sets of DNA from 2 parents
(most plants and animals)
ex: asexual: one organism produces offspring which are genetically
identical to itself (ex: aphids, bees)
6.
Can respond to its environment
ex: detect and react to stimuli (through senses)
7.
Can maintain a stable internal environment (homeostasis)
ex: need an optimal temperature, pH, water and salt balance
for metabolic functions to continue
8.
Can change over time (the species evolves)
ex: collection of changes in the gene pool of the
species in response to environmental factors
Scientific Measurement
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Metric system is used in data collection
SI : International System of Units
Based on multiples of 10, easy to use
Metric Units:
– Length = meter (m)
– Volume = liter (L)
– Mass = gram (g)
– Temperature = Celsius (°C)
Microscopes
The Compound Light Microscope
Most commonly used microscope
Can be used to see living specimens
Magnifies up to 2000X
Limits of Resolution
The point at which objects get blurry
and detail is lost
Limits to what we can see with a
compound light microscope
Using a Compound Light Microscope
Some specimens can be seen without
any special preparation
Some specimens blend in with their
environment so they have to be
stained to see them (stain will kill
them)
Electron Microscopes
Transmission electron microscopes (TEMs)
– shines a beam of electrons through a
sample and then magnifies the image of
the CROSS SECTION of the object, must be
sliced THIN (= death)
Scanning electron microscopes (SEMs) – a
pencil-like beam of electrons scans back
and forth across the surface of a
specimen, the electrons that bounce off
the specimen are picked up by detectors
that provide the information to form an
image of the SURFACE of the object; can
magnify up to 250,000X
Limitations of Electron Microscopes
Living cells cannot be observed in the electron
microscope
Techniques of a Biologist
Fractionation - first the cells are broken apart using a
blender, then the broken bits of cells are placed in
a tube in a centrifuge
Centrifugation – the tube is then spun up to 20,000
times per minute, separating the cell parts, heavier
parts settle in the bottom of the tube, while the
lighter parts float on top
Micromanipulation
Another way to remove parts of a cell
Microscopic instruments are used to dissect, remove,
insert, or manipulate specific parts of a cell
Cell Cultures
Used to study a particular kind of cell
An entire population of cells is grown from a single
cell in a controlled environment so that many
copies of the same type of cell can be studied
EX/Hela cell line – cell culture obtained from
Henrietta Lacks in 1951, first “immortal” cell line