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Lesson 1: The Cell Cycle and
Cell Division
Lesson 2: Levels of Organization
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2.1 The Cell Cycle and Cell Division
cell cycle
anaphase
interphase
telophase
centromere
daughter cell
mitosis
cell plate
cytokinesis
prophase
homologous
chromosome
metaphase
sister chromatid
2.1 The Cell Cycle and Cell Division
The Cell Cycle
• Life cycle of cells
• Includes phases of growth, development,
and reproduction (interphase, mitosis, and
cytokinesis)
2.1 The Cell Cycle and Cell Division
Phases of the Cell Cycle
• The phase of the cell cycle when a cell is
preparing to reproduce is called interphase.
• The phase when a eukaryotic cell
reproduces is called mitotic phase.
2.1 The Cell Cycle and Cell Division
Phases of the Cell Cycle (cont.)
2.1 The Cell Cycle and Cell Division
Length of a Cell Cycle
• Length of time for cell cycle is different for
different types of organisms and cells
• During earliest stages of animal growth,
cell cycle can repeat quickly
• Dependent on the type of organism and
type of cell
• Cell cycles repeat quickly in early stages of
animal growth
2.1 The Cell Cycle and Cell Division
Characteristics of Interphase
• Cell performs specific functions during
interphase.
– Stomach cells might produce
substances that aid in digestion.
– Plant cells might perform cellular
respiration.
2.1 The Cell Cycle and Cell Division
Characteristics of Interphase (cont.)
• During interphase, the chromosomes in a
nucleus are so thin they cannot be observed
with a light microscope.
• For each chromosome in one set of
chromosomes, there is a similar
chromosome in the other set of
chromosomes.
• Each pair of similar chromosomes is called
a pair of homologous chromosomes.
2.1 The Cell Cycle and Cell Division
Phases of Interphase
• There are three phases—G1, S, and G2.
• G1: cell grows and carries out its usual
cellular functions
– Some cells remain in G1 and do not
reproduce, such as muscle cells, red
blood cells, and some nerve cells.
2.1 The Cell Cycle and Cell Division
Phases of Interphase (cont.)
• S phase: the homologous chromosomes in
a cell’s nucleus continue growth but also
replicate
• Sister chromatid:
copy of chromosome
ensures that the new
cell is identical
2.1 The Cell Cycle and Cell Division
Phases of Interphase (cont.)
• G2 phase: continues growth and replication
but also replicates organelles
• Mitochondria and chloroplasts: have own
DNA and can duplicate themselves
2.1 The Cell Cycle and Cell Division
Mitosis
• Process in which the nucleus divides
• Cytokinesis: process in which the
cytoplasm divides
• New cells made by mitosis and cell
division will replace old worn-out dead
cells.
– Also produce most cells in a many-celled
organism.
Mitosis
2.1 The Cell Cycle and Cell Division
Mitosis
• A different type of cell division produces
sperm and egg cells.
• There are four phases of mitosis.
Mitosis
2.1 The Cell Cycle and Cell Division
Phases of Mitosis
• Prophase: first phase of mitosis in which
the DNA twists into tight coils and the
nucleus membrane breaks apart
• Replicated DNA condenses into
chromosomes.
• Nuclear membrane disappears?
2.1 The Cell Cycle and Cell Division
Phases of Mitosis (cont.)
• Metaphase: second phase of mitosis in
which the replicated chromosomes move
to middle of cell and line up end-to-end
• Chromosomes align at the
middle of the cell.
2.1 The Cell Cycle and Cell Division
Phases of Mitosis (cont.)
• Anaphase: third phase of mitosis in
which the sister chromatids separate and
the centromeres divide
• Centromeres divide.
• Sister chromatids separate.
2.1 The Cell Cycle and Cell Division
Phases of Mitosis (cont.)
• Telophase: final phase of mitosis in
which a new membrane forms around
each set of chromosomes
• Nuclear membranes form.
2.1 The Cell Cycle and Cell Division
Dividing the Cell’s Components
• During cytokinesis the final stage of cell
division, the cytoplasm and its components
divide to form two identical daughter cells.
– At the start of cytokinesis, the cell membrane
pinches inward.
• A disc, or cell plate, forms between the
two new nuclei that are dividing.
– This becomes the cell membrane, which builds
the new cell walls.
2.1 The Cell Cycle and Cell Division
Results of Cell Division
• After mitosis and cell division, the original
cell—the parent cell—no longer exists.
• The chromosomes of two daughter cells
are identical in number and type to each
other and to the parent cell.
• All the cells in the body have identical
chromosomes except sperm and egg cells.
2.1 The Cell Cycle and Cell Division
When a cell is preparing to reproduce,
what phase of the cell cycle is it in?
A S phase
B prophase
C interphase
D mitosis
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D
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C
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B
A
B
C
D
A
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2.
3.
4.
2.1 The Cell Cycle and Cell Division
In which phase does the nucleus
divide?
A G2
B mitosis
C cytokinesis
D cell division
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D
0%
C
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B
A
B
C
D
A
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2.
3.
4.
2.1 The Cell Cycle and Cell Division
In which type of cell would you
expect to see a cell plate form?
A plant cell
B animal cell
C stomach cell
D parent cell
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D
0%
C
0%
B
A
B
C
D
A
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2.
3.
4.
2.2 Levels of Organization
cell differentiation
stem cell
tissue
organ
organ system
2.2 Levels of Organization
Single-Celled Organisms
• Need to be organized
• Carry out all the functions needed for their
survival, including:
– obtaining nutrients
– waste removal
– movement
– protection
– reproduction
2.2 Levels of Organization
Prokaryotes
• Single-celled organisms that do not have
nuclei or other organelles, such as bacteria
– Still have structures with specific
functions
– Same processes that occur in
eukaryotic organelles happen along
specialized membranes in bacteria
2.2 Levels of Organization
Eukaryotes
• Protists are single-celled eukaryotes
– Include amoeba and some fungi
– Are more complex than prokaryotes
– Have a nucleus
and membranebound organelles
2.2 Levels of Organization
Eukaryotes (cont.)
• Single-celled eukaryotes are more complex
than cells in multicellular eukaryotes.
– Single-celled: exist alone and must do
everything needed for their survival
within the single cell
– Multicellular eukaryotes: rely on one
another and cannot survive alone
2.2 Levels of Organization
Multicellular Organisms
• Multicellular organisms require
organization.
• They have many cells and usually have
more than one type of cell.
How do animal and
plant cells work?
2.2 Levels of Organization
Cell Differentiation
• Process in which cells become different
types of cells
• Differentiated cells: specialized structures
and shapes for specific functions, such as
liver cells or brain cells
• Once most human cells differentiate, they
cannot become any other type of cell.
Cell
Specialization
2.2 Levels of Organization
Stem Cells
• Cells that can become different types
of cells
2.2 Levels of Organization
Tissues
• Groups of similar cells that work together
and perform a function
2.2 Levels of Organization
Tissues (cont.)
2.2 Levels of Organization
Organs
• A group of similar tissues that work together
to perform a function
2.2 Levels of Organization
Organs (cont.)
• Human organs include the heart, lungs,
brain, and muscles.
• Plant organs have organs, such as leaves,
that store nutrients, exchange gases,
transport water or nutrients, or perform
photosynthesis.
2.2 Levels of Organization
Organ Systems
• One or more organs that work together and
perform one or more functions
2.2 Levels of Organization
Organ Systems (cont.)
2.2 Levels of Organization
Organ Systems (cont.)
2.2 Levels of Organization
Organ Systems (cont.)
2.2 Levels of Organization
Organisms
• The most complex unit of living things is a
multicellular organism.
• Multicellular organisms usually have many
organ systems.
• Each organ system has its own function but
is dependent on other organ systems.
2.2 Levels of Organization
Organisms (cont.)
2.2 Levels of Organization
Where do bacteria carry out the
processes that occur in the
organelles of eukaryotes?
A nucleus
B chloroplast
C smooth ER
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D
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C
D specialized
membranes
B
A
B
C
D
A
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2.
3.
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2.2 Levels of Organization
What are undifferentiated cells
called?
A stem cells
B tissues
C prokaryotes
D liver cells
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D
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C
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B
A
B
C
D
A
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2.2 Levels of Organization
What organ system produces
hormones that control body
functions?
A skeletal
B lymphatic
C nervous
D endocrine
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D
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C
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B
A
B
C
D
A
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2.
3.
4.
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Each chromosome in one set of
chromosomes has a similar chromosome
in the other set of chromosomes. What is
a pair of similar chromosomes called?
A sister chromosomes
B homologous chromosomes
C daughter chromosomes
D parent chromosomes
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D
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C
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B
A
B
C
D
A
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2.
3.
4.
Sister chromatids are held together
at what region of the chromatids?
A the ends
B the centromere
C the cell plate
D G1
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D
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C
0%
B
A
B
C
D
A
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2.
3.
4.
When do the sister chromatids of
each replicated chromosome begin to
separate?
A prophase
B metaphase
C anaphase
D telophase
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D
0%
C
0%
B
A
B
C
D
A
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2.
3.
4.
By what process do cells become
different types of cells with
specialized structures and functions?
A cell division
B mitosis
C cell differentiation
D the cell cycle
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D
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C
0%
B
A
B
C
D
A
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4.
What does a leaf have in common
with a bicep muscle?
A both perform the
same function
B both are at the same
level of organization
C both are tissues
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0%
D
0%
C
D both are eukaryotes
B
A
B
C
D
A
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SCI 1.e
What happens during cytokinesis?
A the nucleus divides
B the cytoplasm divides
C chromosomes
are replicated
D growth and cellular
functions
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0%
D
0%
C
0%
B
A
B
C
D
A
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2.
3.
4.
SCI 1.e
What is the first phase of mitosis?
A interphase
B G1
C prophase
D cell division
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D
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C
0%
B
A
B
C
D
A
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2.
3.
4.
SCI 5.a
What is the most complex level of
organization?
A organism
B organ system
C cells in eukaryotes
D tissues
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D
0%
C
0%
B
A
B
C
D
A
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2.
3.
4.
SCI 5.a
What is a group of cells that work
together to perform a function
called?
A organ
B organ system
C organism
D tissue
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D
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C
0%
B
A
B
C
D
A
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3.
4.
SCI 1.f
What is a stem cell?
A a leaf cell
B a differentiated cell
C an undifferentiated
cell
D a fertilized egg
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0%
D
0%
C
0%
B
A
B
C
D
A
1.
2.
3.
4.
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