Development
Links - Biology
Components of Development
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Growth- The process of a multicellular
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Differentiation- The process of cells in
increasing its number of cells, becoming
larger. (i.e. zygote to an adult)
a multicellular organism (initially all alike)
becoming different from each other
generating the various tissues (i.e. nerve,
muscle, skin and bone, etc.) necessary to
be a functional adult .
Thoughts on development:
Growth
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Cells generating more cells (Mitosis and
Cytokinesis)
A single cell has size limits, therefore for
organisms to become larger they must be
multicellular.
All cells of an organism have a complete set of
DNA to make the entire organism.
Cell death, as well as cell growth must occur for
proper development
Connected to the cell cycle.
Mitosis and Cytokinesis
Cell cycle
Phases of Mitosis
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Interphase
Prophase
Metaphase
Anaphase
Telophase
Animation link(s)
http://science.nhmccd.edu/biol/mitosis/pmitosis.html
http://www.lewport.wnyric.org/jwanamaker/animations/mitosis
.html
http://www.sci.sdsu.edu/multimedia/mitosis/mitosis_qt1.html
Interphase
Prophase
Metaphase
Anaphase
Telophase
Thoughts on development:
Differentiation
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What if your entire body was made of only
stem cells? Muscle cells? Nerve cells?
Do different types of cells (tissue) perform
different jobs in a multicellular organism?
If all of the organisms cells are genetically
Identical, how do they become different
types of cells (tissue)?
Epithelial and Connective
Nerve
and
Muscle
OKAY???????
But how does an
organism get all of
these cell (tissue)
types?
Historical perspective
The “Homunculus” Theory =
A fully formed person,
just very tiny, exists in
the head of a sperm cell.
The egg makes no
contribution except to
function as an incubator.
No differentiation
necessary!!!!!!!!!!
We now know better.
Embryonic differentiation:
Zygotes
Early embryonic development
Blastula
Gastrulation
It is not birth, marriage, or
death, but gastrulation,
which is truly the most
important time in your life."
Lewis Wolpert (1986)
Embryonic cell (tissue) types
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As embryo’s
develop to the
gastrulation stage
they form three
basic types of
tissue which
differentiate into
all other tissues:
Endoderm
Mesoderm
Ectoderm
These basic tissues become:
OKAY ??
But how do we get to become
these tissues from embryonic
stem cells?
Influences on differentiation
(switching genes on and off)
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Environmental influences both inside the cell and outside
the cell can cause certain genes to switch on or off at
appropriate or inappropriate times.
Inside the cell- differential distribution of materials
during cell division can cause cells to develop differently.
Outside the cell- chemical communication with nearby
cells may influence development based on strength of
signal.
Induction- is a special type of outside influence. (Leads
to Cell Differentiation)
??????????? (good field for a career)
Induction!!!
Apoptosis (cell death) at the appropriate
time is also very vital to development.
What next?
Development sometimes messes up!
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Cancer- one’s own cells fail to
stop reproducing when they
should.
Birth defects- environmental
factors + genetics cause
misinformation during
development.
Key Development terms
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Zygote
Blastula
Gastrulation
Growth
Cytokinesis
Mitosis
interphase
prophase
metaphase
anaphase
telophase
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Differentiation
Senescence
Cell cycle
DNA
Induction
Cancer
Metastasis
Birth defects
Mutation
Final thoughts
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Development must occur at the correct times and correct
places in the embryo.
Animal development occurs in consistent patterns.
Plants go through similar development.
Cell deaths must also occur at appropriate times.
Development is a zygote to death process.
Developmental errors often cause spontaneous abortions
(miscarriage)
Environmental factors can greatly influence development
(especially during very early development).
Development = growth + differentiation.
We still have a lot to learn about development.