The Importance of Reproduction and Development

1. REPRODUCTION
AND DEVELOPMENT
LESSON 1

2. Development
is the process by which a
multicellular organism, beginning
with a single cell, goes through a
series of changes, taking on the
successive forms that characterize
its life cycle.

4. FOUR KEY PROCESSES UNDERLIE
DEVELOPMENT
Determination sets the developmental fate of a
cell—what type of cell it will become—even
before any characteristics of that cell type are
observable. For example, in a developing
mammalian embryo, as well as in some adult
organs, there are mesenchymal stem cells that
look unspecialized. But their fate to become
muscle, fat, tendon, or other connective tissue
cells has already been determined.

5. Differentiation is the process
by which different types of
cells arise from less specialized
cells, leading to cells with
specific structures and
functions. For example,
mesenchymal stem cells
differentiate to become the
cells listed above.

6. Morphogenesis (Greek for <origin
of form=) is the organization and
spatial distribution of
differentiated cells into the
multicellular body and its organs.
Morphogenesis can occur by cell
division, cell expansion
(especially in plants), cell
movements, and apoptosis
(programmed cell death).

7. Growth is the increase in size of
the body and its organs by cell
division and cell expansion.
Growth can occur by an increase
in the number of cells or by the
enlargement of existing cells.
Growth continues throughout the
individual’s life in some
organisms, but reaches a more or
less stable end point in others.

8. HUMAN REPRODUCTIVE SYSTEM
Organ system by which humans
reproduce and bear live offspring.
Provided all organs are present,
normally constructed, and
functioning properly, the essential
features of human reproduction
are:

9. 1. liberation of an ovum, or egg, at
a specific time in the reproductive
cycle
2. internal fertilization of the
ovum by spermatozoa, or sperm
cells
3. transport of the fertilized ovum
to the uterus, or womb

10. 4. implantation of the blastocyst, the
early embryo developed from the
fertilized ovum, in the wall of the uterus,
5. formation of a placenta and
maintenance of the unborn child during
the entire period of gestation,
6. birth of the child and expulsion of the
placenta, and
7. suckling and care of the child, with an
eventual return of the maternal organs to
virtually their original state.