Download 7th Grade Life Science Mid

7th Grade Life Science Mid-Term Exam
Study Sheet – The Big Ideas & Essential Questions in Life Science
1. The Microscope – Why is this an important tool for the biologist and how does it
work?
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The process of enlarging the image of a specimen is called magnification.
A microscope is an instrument that makes small objects look larger.
A compound microscope uses two or more convex lenses. Each convex lens bends
light to make the object appear larger.
The best way to carry a microscope is to hold the arm and the base.
The place where the specimen is placed for viewing is called the stage.
A light microscope uses a light source to view objects.
Resolution is the ability of a microscope to focus on two separate, very close objects
at the same time.
An electron microscope uses a beam of electrons to produce magnification.
The scientist whose name is most associated with the early use of the microscope and
the discovery of microbes, living single-celled organisms, is Anton von
Leeuwenhoek. He observed cells that were alive – living, singled-celled organisms.
2. Cells – What is the basic unit of structure and function of all living things?
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All living things are made of small units called cells.
The scientist whose name is most associated with the identification and naming of
cells is Robert Hooke. He discovered cells that were actually dead in a slice of cork.
The organelle responsible for turning food and oxygen into energy is the chloroplast.
The organelle responsible for assembling proteins is the ribosome. Ribosomes are
tiny grain-like structures.
The organelle responsible for storing food, water, wastes, and other materials is the
vacuole.
The organelle responsible for controlling the activities of the cell is the nucleus.
The organelle responsible for packaging proteins is the Golgi body.
The organelle responsible for controlling what goes in and what goes out of the cell is
the cell membrane.
The organelle responsible for transporting proteins is the endoplasmic reticulum.
The organelle responsible for releasing chemicals that break down large food
molecules and waste products in the cell into smaller molecules is the lysosome.
The organelle in which photosynthesis takes place is the chloroplast.
The organelle responsible for turning food and oxygen into energy is the
mitochondrion.
All living things are made of cells. The cell is the basic unit of structure and function
of all living things. All cells come from other living cells. These ideas make up the
cell theory.
There are two types of cells. Cells that do not have their genetic material enclosed in
a nucleus are called prokaryotic. Bacterial cells are prokaryotic. Cells that do have
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their genetic material enclosed in a nucleus are called eukaryotic. Plants, animals,
fungi, and protists are eukaryotic.
Prokaryotic cells like bacteria cells are smaller than eukaryotic cells.
Some organisms are single-celled. Other organisms are multi-celled. Multi-cellular
organisms tend to have different shapes and sizes of cells.
3. Chemistry of Life – What are the chemical compounds necessary for life?
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An element is a substance that cannot be broken down into any simpler substance
by any typical means. Carbon, hydrogen, oxygen, and nitrogen are the elements
that make up the bulk of living things. Remember: CHON.
A compound is a chemical combination of two or more elements.
Elements come together to form compounds through the process of sharing or
capturing electrons. This process is called bonding.
The chemical compounds that are associated with living things contain the
element, carbon. These compounds are called organic compounds.
The major organic compounds are carbohydrates, lipids, proteins, and nucleic
acids.
Sugars and starches are carbohydrates. Sugar molecules can be combined to form
larger molecules called starches. They provide fast energy.
Lipids are fats, waxes, and oils. They provide stored energy.
Proteins are made up building blocks called amino acids. Proteins are used by the
body for building, healing, and speeding chemical reactions.
Two types of nucleic acids are DNA and RNA. They carry the instructions for all
life activities.
4. Cell Transport – How do substances get into and out of a cell?
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The process by which molecules move from an area where they are in a higher
concentration to an area where they are in a lower concentration is called diffusion, a
form of passive transport.
Water diffuses through a selectively permeable cell membrane by a special process
called osmosis, another form of passive transport.
Both diffusion and osmosis are forms of passive transport during which a cell does
not have to use any energy.
A method of cell transport that requires a cell to use energy to move materials from
one area to another is called active transport.
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5. Cell Processes – What are the basic cell activities that support life?
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The process responsible for producing most of Earth’s oxygen is photosynthesis.
Almost all life on Earth depends on photosynthesis.
The raw materials of photosynthesis are water and carbon dioxide.
The products of photosynthesis are glucose and oxygen.
The green pigment, chlorophyll is packaged in small organelles called chloroplasts.
Chlorophyll captures light energy of the sun to power the process of photosynthesis.
Organisms that produce their own food during photosynthesis are called autotrophs.
The small holes on the undersides of leaves that allow carbon dioxide to enter are
called stomata.
Organisms that cannot produce their own food are called heterotrophs.
Cellular respiration in the process by which cells break down simple food molecules
to release the energy they contain.
Small amounts of energy are released during the respiration that takes place in the
cytoplasm of a cell. The stage of respiration that produces the greatest amount of
energy takes place in the mitochondria of cells.
The raw materials of cellular respiration are glucose and oxygen.
The products of cellular respiration are energy, carbon dioxide, and water.
Some cells are able to obtain energy from food without oxygen. This process is called
fermentation. Fermentation does not produce as much energy as respiration.
One type of fermentation takes place in the muscle cells of a human. When
respiration cannot provide enough energy to muscle cells after running fast or hard
exercise, the cells begin to use lactic acid fermentation as a source of energy. Lactic
acid fermentation does not produce much energy and the lactic acid produces painful
muscles..
The processes of photosynthesis and cellular respiration are opposite and
complementary. This means that the products of one are the raw materials of the
other.
6. The Cell Cycle and Cancer – How do cells divide and what happens when the
process goes wrong?
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The entire life of a cell from formation to division is called the cell cycle.
Entire cells divide to form exact copies of themselves during the process of cell
division.
Most of a cell’s life is spent in the stage called interphase. During the last part of
interphase, the cell’s DNA replicates in preparation for cell division.
The final stage of cell division is called cytokinesis. During cytokinesis two new,
identical daughter cells are formed.
The part of the cell cycle that involves just the division of a nucleus into two identical
nuclei is called mitosis. (The phases of mitosis are prophase, metaphase, anaphase,
and telophase.)
Mitosis is possible because DNA is a self-replicating molecule. It can zip down the
middle and produce complementary copies of each side.
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The DNA molecule is called a double helix. It looks like a twisted ladder or a spiral
staircase.
Each rung of the “ladder” is made up of pairs of nitrogen base pairs.
Prior to mitosis, all of the DNA in a cell makes copies of itself so that the two
resulting daughter cells will be identical to the parent cell. This process is called
replication.
Cancer is a group of over 100 diseases in which some body cells grow and divide
uncontrollably, damaging the parts of the body around them.
A tumor is a mass of abnormal cells that develops when cancerous cells divide and
grown uncontrollably.
Cancer can spread when cells break off a tumor and are carried through the body by
the bloodstream.
There are three main ways of treating cancer. Surgery removes the cancerous tumors;
radiation kills the cancer cells with high energy beams; chemotherapy kills cancer
cells with drugs.
Some cancers are preventable. For example, the use of tobacco is the major cause of
lung cancer.
Another factor that may lead to as many cancer deaths as tobacco is an unhealthy diet.
Note: Be sure you can identify the diagrams and use the charts you have studied
so far this year:
 plant cell vs. animal cell
 structure of DNA with A-T/C-G nitrogen bases, sugar phosphate backbone, the
double helix
 the stages and phases of the cell cycle (cell division: interphase, mitosis,
cytokinesis) and mitosis (prophase, metaphase, anaphase, telophase)
 photosynthesis equation
 osmosis and diffusion
 cell parts and organelles
 the process of respiration in a cell
 tests for starch and lipids
 production of energy during cellular respiration
Plant Cell
Animal Cell
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Interphase
The
Structure
of DNA
The Cell Cycle
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What happens during mitosis?
Diffusion
burst
stay the same
shrivel
Osmosis
Cellular Respiration
glucose
simple
molecules
cytoplasm
oxygen
Red blood
cells in water
with very
little salt
Red blood
cells in
plasma, the
liquid part
of blood
Red blood
cells in very
salty water
What happens to the red blood cells in each solution?
mitochondrion
Where is the greatest amount of energy produced?
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