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Welcome to
Biology 521!
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Introduction to Biology
What exactly are we studying?
Define Biology
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"Biology is...
the study of living things." This sounds simple, but biology is a very broad field. It is closely related to other branches of science. Concepts from chemistry and physics are important to the study of biology. For example, all living things use energy, a topic studied in physics. An understanding of how molecules are formed and how atoms interact is vital to understanding the processes that occur in cells...in other words, chemistry.
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Brainstorm some professions where a knowledge of biology would be helpful. Try to come up with as many as possible.
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So biology is the study of living things...
...but what do we mean by "living"?
In other words, what separates thing that are "alive" from
those that are "not alive"?*
*We won't include things like dead bodies of organisms...
even though they aren't alive, they once were.
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Take a few minutes and brainstorm...come up with as
many characteristics as you can that separate living things
from non­living things.
Look at the objects on the following page as you think...
which ones are organisms, and which are not?
What separates the two categories? Title: Sep 7­10:06 AM (6 of 65)
Are there any exceptions?
For example, can any of the non­living things do some of
the same things as living
organisms?
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What were the characteristics that define living things?
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How to Effectively Take Notes From
the Biology Textbook
The ability to take meaning from written text and internalize it is one of the most important skills you should master as you prepare for continuing your education beyond high school. Following the guidelines below will help you develop this ability. We will be practicing it throughout the semester; completion of assigned readings with appropriate notes will form the bulk of your homework check marks
View Hints Online
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Chapter 1: The Micro­Universe of the Cell
Group practice: beginning with the introduction and the first page of Section 1.1, go through the process described for taking notes.
Work first individually, then compare results as a group.
Discuss any questions that anyone might have.
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Chapter 1 The Micro­Universe of the Cell
SECTION 1.1The Development of Cell Theory
State the 4 points of Cell Theory
1) All organisms are made up of one or more cells and the products
of those cells.
2) Cells are the basic unit of structure and function in all living
things.
3) New cells are from other living cells by cell division.
4) The activity of multicellular organisms is the result of the combined actions of all the cells which make it up.
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What is spontaneous generation? How is it related to abiogenesis?
spontaneous generation *the idea that life comes from non­living or once living things
*this concept was around for close to 2000 years
*renamed abiogenesis by Thomas Huxley
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What evidence was there to support abiogenesis?
*maggots appear on rotting meat
*frogs and salamanders appear suddenly in mud
*mixing a dirty shirt and wheat grains produce mice
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What is biogenesis?
The idea that life can only come from pre­existing living things.
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Four of the scientists whose experiments advanced the argument between abiogenesis and biogenesis:
1) Francesco Redi (1668)
2) John Needham (1748)
3) Lazzaro Spallanzani (1765)
4) Louis Pasteur (1860)
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Francesco Redi
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John Needham & Lazzaro Spallanzani
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Louis Pasteur
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In Class Activity and Homework Assignment
To examine the science which lead to the support of biogenesis over abiogenesis, perform the Thinking Lab Activity on page 7. Complete questions1, 2, 3* and 5.
*In Question 3, create a timeline, showing scientific developments in green; societal reactions in blue; and technological advancements in red.
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Sample partial timeline...
Aristotle classifies all
organisms as plants or animals;
writes that living things can form
from non­living matter
334 BC
Knowledge of nature
passed orally between
generations
Up to 5,000
years ago
Roger Bacon makes
first recorded reference
to eyeglasses
1268
European scholars regard
knowledge as unchangeable;
rely on Aristotle
1500
700
1400
Islamic scholars advance knowledge of
mathematics, medicine, astronomy, optics
500 BC
Ancient Greece supports
full­time scholars. They use
observation and thought rather
than experimentation
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1590s
Dutch eyeglass makers
invent first compound microscope
Be prepared to discuss the answers to questions 1­3 and 5 from page 7 during class.
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Homework Check!
(Cell Theory Timeline)
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Answers to Question 5, page 7
(a) When were cells first observed?
1665, by English scientist Robert Hooke
When were they next observed?
1666 or 1667, by Dutch scientist Antony van Leeuwenhoek
When were they recognized as the basic unit
of life?
1845 by German botanist Alexander Carl Henrich
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(b) Reexamine the four hypotheses that make up
the cell theory. Are any of these based on an
event that is not shown in your organizer?
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(c) What technological tools helped scientists
develop the cell theory?
(d) What techniques and methods helped
scientists develop the cell theory?
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(e) Which public and scientific reactions hindered
development of the cell theory?
Which reactions helped?
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(f) The Internet was originally designed to enable scientists all over the world to communicate quickly and easily. What earlier inventions or processes had a similar effect?
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(g) In 1953, water, methane, hydrogen, and ammonia were mixed and exposed to electrical discharges. This resulted in the production of chemicals that are found in components of all living cells. How do these results affect the abiogenesis/biogenesis debate?
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(h) So far, no scientists have been able to produce living cells from non­living matter. If this did happen, what might three possible responses from the public and scientific community be?
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Read the following definition of "paradigm":
One that serves as a pattern or model. A set of assumptions, concepts, values, and practices that constitutes a way of viewing reality for the community that shares them, especially in an intellectual discipline.
What do you think would be meant by a "paradigm shift"?
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Do you agree or disagree with the following statement:
"The cell theory represented a paradigm shift in our understanding of nature and life."
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Section 1.3: Structures in the Cell
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Read pages 23­26
Skip the diagram on page 25 for now
(stop at the top of page 26 when you reach the subsection heading "Cell Organelles")
Use the guidelines given in class to take your own notes on these subsections.
View Guidelines
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What are the seven tasks that living cells have to perform to maintain life? (see Section 1.3, page 23­33)
1)
2)
3)
4)
5)
6)
7)
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Compare prokaryotic and eukaryotic cells
Prokaryotic Cells
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Eukaryotic Cells
Compare prokaryotic and eukaryotic cells
Prokaryotic Cells
• do not have a nucleus
• are the smallest of cell types
• lack internal membrane­bound
organelles
e.g. bacteria
Eukaryotic Cells
• have a nucleus
• are 10 to 1000 times larger than
prokaryotic cells
• have many kinds of organelles,
many of which are membrane bound
e.g. all other cells, which make up
animals, plants, fungi, protists
Types of Bacteria
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Cell Size
Read the rest of Section 1.3, pages 26­33
Take your own notes on the various organelles found in typical cells. Be sure you include:
• The structure and function of each organelle
• The differences between animal and plant cells
• The specialized regions within prokaryotic cells
You may find it helpful to organize these notes in a table.
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Eukaryotic Organelles: Structure and Function
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Cell Membrane
The cell membrane separates the contents of the cell from the surrounding environment. It is composed of a double layer of phospholipid, forming a flexible barrier. The structure of the cell membrane will be studied in detail during Chapter 2.
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Nucleus
nucleolus
nucleoplasm/crhomatin
nuclear envelope
nuclear pore
Largest organelle, and the control center of cell. Surrounded by a double membrane (the nuclear envelope) with nuclear pores allowing transport of materials into and out of the nucleus. Contains fluid nucleoplasm, and chromatin (strands of DNA). The nucleolus is responsible for producing ribosomes.
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Ribosomes
Every cell contains thousands of ribosomes, either floating in the cytoplasm or attached to the rough endoplasmic reticulum. Each ribosome is composed protein and RNA, and consists of a large and a small subunit. They are the site of protein synthesis.
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Endoplasmic Reticulum
ribosomes
smooth ER
rough ER
A network of folded membranes throughout the cytoplasm. The ER provides a large surface area for cell reactions to occur on, and a transport system for materials to be moved throughout the cell while being kept isolated. The ER can be rough (with attached ribosomes) or smooth (no ribosomes). Smooth ER can pinch off bubbles, or vesicles, to transport molecules to the cell membrane or the Golgi.
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Golgi Apparatus
The Golgi apparatus appears as a stack of membrane sacs. It completes the processing of molecules synthesized on the ER, and packages them into membrane bubbles called vesicles for transport, either throughout the cell or to the cell membrane where they are secreted.
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Mitochondria
cristae
inner membrane
outer membrane
matrix
Mitochondria are the powerplants of the cell. Glucose breakdown begins in the cytoplasm, and is completed in the mitochondria. The energy released is used to form ATP (adenosine triphosphate), which the cell can use to run its chemical reactions. Each mitochondria has an outer membrane, and an inner membrane with many folds called cristae. The fluid inside the mitochondria is called the matrix. Mitochondria are more numerous in cells which use a great deal of energy, such as muscle or liver cells. They contain their own ribosomes and DNA, and can divide on their own. *mitochondria are thought to have formed from symbiotic bacteria
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Lysosomes
Lysosomes appear to be bubbles floating in the cytoplasm. They are composed of a single membrane layer containing a fluid of water and digestive enzymes. When a lysosome attaches to a food vacuole, it releases the enzymes, breaking down the structure of the food into simpler molecules. Lysosome enzymes are also used to defend the cell against invading viruses or bacteria, and to remove and break down worn out cell organelles.
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cell membrane
Golgi apparatus
lysosome
mitochondria
nucleus
nucleolus
ribosome
rough endoplasmic
reticulum
smooth endoplasmic
reticulum
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Virtual Cell at "Cells Alive"
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Homework:
Finish reading Section 1.3, pages 29­33
Complete notes on this section, being sure to include information on the structure and function of all eukaryotic cell organelles, and the specialized structures of prokaryotic cells.
*Review your notes, and list the typical structural differences between plant cells and animal cells. (In other words, what structures are found in plants that are not in animal cells, and what do animal cells have that are not found in most plant cells?)
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Peroxisome
Peroxisomes are similar in appearance to lysosomes. They have a single membrane, surrounding strong enzyme contents. Formed in the cytoplasm, peroxisomes are most common in liver, kidney, and brain cells. They function to rid the cell of toxic substances, such as hydrogen peroxide that is formed during cell metabolism. In the liver, peroxisomes detoxify alcohol.
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Peroxisome
The cytoskeleton provides support and shape to the cell, and allows movement of parts within the cell. There are three main strands that form the cytoskeleton: microfilaments (made of the protein actin, a major structural protein in muscle cells which can contract); intermediate filaments (which act as anchor points); and microtubules (composed of the protein tubulin).
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Centrosome
The centrosome is composed of a pair of cylindrical centrioles. Each is made up of nine sets of three microtubules, arranged in a ring. During cell division, the centrioles move to opposite ends of the cell, and use microfilaments to pull the cell contents apart. Centrioles are normally found only in animal cells.
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Cilia and Flagella
Cilia and flagella are used by several unicellular organisms for the same purpose: movement. They also have a similar structure, a ring of nine microtubule pairs forming a ring surrounding a tenth pair. The difference has to do with how long and numerous they are. One or two long "tails" are called flagella; shorter "hairs" covering the cell are called cilia. Cilia are also used to move fluid past the cell, and are found on the cells in structures of complex organisms (for example, in the trachea to remove particles from the lungs.)
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Cell Wall
The cell wall provides strength and support for plant cells. It is composed of a tough, fibrous carbohydrate called cellulose. The cell wall lies outside of the cell membrane. The plant cells that form support structures, such as stems, have a secondary inner cell wall containing lignin, a complex chemical that acts as a binding agent (like glue) to add even more strength while remaining flexible.
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Central Vacuole
central vacuole
The central vacuole in plant cells stores water and other dissolved substances. This provides pressure (called turgor pressure) inside the cell, forcing the cytoplasm against the cell wall and giving the plant strength. (Think of what happens to a plant if it doesn't get enough water.) The central vacuole may also contain toxins produced by the plant making it taste bad to animals.
*Animal cells also contain vacuoles; however, these are smaller, and appear as membrane bubbles in the cell, similar to lysosomes or peroxisomes. These animal cell vacuoles may contain food, wastes, etc.
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Chloroplast
outer membrane
inner membrane
thylakoid
granum
stroma
Plastids are specialized organelles found only in plants. Chloroplasts are the most familiar. They contain the pigment chlorophyll, which gives plants their green color and is responsible for photosynthesis. Another plastid, leucoplasts, are colorless and are used to store starches and other nutrients in plant cells. Like mitochondria, chloroplasts have a double membrane. They contain numerous stacks of membrane sacs called thylakoids (stacks of thylakoids are grana, singular granum ), and are filled with a fluid called the stroma. Title: Sep 12­7:39 PM (55 of 65)
Prokaryotic Structure
nucleoid
capsule
intercellular fluid
plasma membrane
ribosomes
Prokaryotic cells are the bacteria. With no distinct organelles, they are simpler in structure than eukaryotic cells. Still, bacteria are successful, and can survive in extremely hostile environments. They are surrounded by a plasma membrane, often surrounded by a slime layer called the capsule. Bacteria contain DNA which forms a nucleoid region, and may contain plasmids , circular fragments of self­replicating DNA. Ribosomes which are responsible for protein synthesis, float throughout the intercellular fluid filling the bacteria. Some may have flagella and pilli, which allow bacteria to exchange plasmids, and some form protective cell walls. Title: Sep 12­7:39 PM (56 of 65)
What are the structural differences between plant cells and animal cells?
Animal Cells
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Plant Cells
Homework
Review Section 1.3, pages 23­33
Complete Questions #1, 4, 6, 8, 9, and 12 on page 34
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Homework
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Virtual Cell at "Cells Alive"
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Label the following cell.
Is this an animal cell or a plant cell? How do you know?
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Label the following cell.
Is this an animal cell or a plant cell? How do you know?
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Section 1.2: Using a Microscope to Explore the Cell
*Read pages 12­13 and 20­21, and take notes on the sections.
*Label the parts of the microscope (handout sheet) using the diagram on page 16.
*Read Investigation 1.A: Caring for and Using a Microscope. *Complete the pre­lab questions on page 15.
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Compound Light Microscope
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Compound Light Microscope
condenser lens
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