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16.1 Cell Growth and Division
Vocabulary
Mitosis:
series of continuous
steps (prophase, metaphase, anaphase and telophase) in which the cell nucleus
divides to form two identical nuclei.
Chromosome:
structures in the cell
nucleus that contain hereditary material.
Asexual reproduction:
process by which a new organism is produced that has a DNA identical to the
DNA of the parent organism.
Outline:
Why do Cell divide?
Constant Change
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All organisms are constantly
changing and new organisms are created because of cellular growth and division.
The Cell cycle
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A life cycle begins with the
organisms formation followed by growth and development and it ends in death.
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Most of the life of a cell with
a nucleus (eukaryotic), is pent in a period of growth and development called
interphase.
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In this phase a cell grows,
copies its hereditary material and prepares for division
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Cell division is a continuous
process and the cell cycle in a cell from one division to the next.
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The cycle is constantly repeated
by cells like skin and bones for repair, growth or replacement
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Cells in your body that no
longer divide (nerve cells) are always in interphase.
Mitosis
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Cells divide in two steps, the
nucleus first and then the cytoplasm.
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Each new nucleus is identical to
the original nucleus.
Animal Cell Mitosis
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Chromosomes actively duplicate
themselves during mitosis.
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When the cell is ready to divide
the duplicated chromosomes become visible and follow the steps of mitosis.
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In animal cells the cytoplasm
pinches to form the new cells.
Plant Cell Mitosis
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Plant cells form spindle fibers
during mitosis, but do not have centrioles.
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In plants the cell walls form
along the cell plate then new cell membranes develop inside the cell walls.
Results of Mitosis
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It is the division of a nucleus
and produces nuclei that are identical to one another.
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Every cell in your body has 46
chromosomes in its nucleus (except sex cells)
Asexual Reproduction
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Reproduction is the process by
which an organism produces others of the same kind
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There are two types asexual and
sexual
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Asexual reproduction of
organisms with a nucleus (eukaryotic) is done through mitosis
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Asexual reproduction of
organisms without a nucleus (prokaryotic) is done through fission
Budding and Regeneration
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During budding a new organism
grows from the body of the parent organism
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During regeneration a whole
organism grows from a piece of the organism or damaged and lost body parts.
16.2 Sexual Reproduction and Meiosis
Vocabulary
Sexual Reproduction:
process by which a new,
unique organism is created when two sex cells, an egg and a sperm, come
together.
Fertilization:
Joining of an egg and a
sperm, generally from two different organisms.
Sperm:
Sex cell produced in the reproductive organs of a male and that has only half
the number of chromosomes of a body cell; has a whip-like tail that provides
motion and a head that contains genetic information.
Egg: Sex
cell that is formed in the reproductive organs of a female and has only half
the number of chromosomes of a body cell.
Meiosis:
Process by which sex
cells are created in the reproductive organs, producing four haploid sex cells
from one diploid cell.
Zygote:
New diploid cell that
is formed when a sperm fertilizes and egg.
Outline:
Sexual Reproduction
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This is another way that a new
organism can be created
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The new organism that develops
has it’s own unique identity
Formation of Sex Cells
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The body has two types of cell –
sex cells and body cells
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Body cells outnumber the sex
cells
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Sex cells are formed only in the
reproductive organs
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Human body cells contain 23
pairs (diploid) of chromosomes (46)
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Human sex cells
contain 23 single form
versions of chromosomes
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Sex cells a produced through a
process called meiosis
The Importance of Sex Cells
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diploid means to have pairs and
Haploid means single form
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.In most organisms the haploid
version of the cell is only found in sex cells
Fertilization
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The new cell that forms through
the process of fertilization is a zygote
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The zygote is a diploid cell
which continues to undergo mitosis and an organism develops
Meiosis
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Meiosis is the division of sex
cells
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It occurs to ensure that
resulting offspring do not have twice the amount of chromosomes
Meiosis I
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This is the separation of the
originally duplicated chromosomes
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The steps are the same as
mitosis, but the chromosomes stay together as pairs
Meiosis II
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During meiosis II the cells go
through steps like mitosis, but are labeled II
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The chromosomes end up
separating the same way they do in mitosis
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The end result is four haploid
sex cells
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