Phyla Cnidaria and Ctenophora, Basic Animal Development ...

Phyla Cnidaria and Ctenophora, Basic Animal Development &
Introduction to Nervous Systems 5.3
Lab #5 - Biological Sciences 102 – Animal Biology
Basic Animal Life Cycles & Development (Embryology)
On the chalkboard, your instructor will diagram a basic, generalized animal lifecycle to
introduce the following terms related to animal life cycles and development. Your instructor
will then review with you the basic life cycle of the cnidarians, Obelia sp. and Aurelia aurita as
specific examples.
EARLY ANIMAL DEVELOPMENT (see diagrams from board)
sperm = the male gamete (haploid = N)
ovum (egg) = the female gamete (haploid = N)
fertilization = the species specific binding of the sperm to the egg and fusion of the
sperm cell nucleus with the egg cell nucleus to create a diploid zygote
zygote = fertilized egg (diploid = 2N)
cleavage = the mitotic cell divisions of an animal zygote; the first cell divisions that
occur to create a morula from the zygote
morula = a solid ball of cells that froms from the mitotic divisions of the zygote
blastula = the next embryonic stage that marks the end of early cell division during
animal development; an embryo that look like a hollow ball of cells
gastrula = the next embryonic stage resulting from the division of the early cells into
three major tissue types during early animal development. The gastrula may have two
(endoderm & ectoderm only) or three tissue layers (ectoderm, mesoderm, & endoderm)
gastrulation = the process that leads to the formation of a gastrula
ectoderm = the outer layer of three embryonic cell layers in a gastrula; forms the skin
of the gastrula and gives rise to the epidermis and nervous system of the adult
mesoderm = the middle layer of the three embryonic cell layers in a gastrula; gives rise
to muscles, bones, the dermis of the skin, and many other organs in the adult
endoderm = the innermost of three embryonic cell layers in a gastrula; forms the gut of
the gastrula and gives rise to the innermost linings of the digestive tract and other
hollow organs (e.g. lungs) in the adult
larvae = an immature animal life stage that is significantly different from the adult and
usually incapable of sexual reproduction
metamorphosis = a drastic change in form during postembryonic development from
the larval stage to another form, usually the adult
adult = the sexually mature form of an animal
Cleavage, the earliest stage in embryonic development, consists of a succession of regular
mitotic cell divisions that partition the egg into a multitude of small cells clustered together. In
lower animals, cleavage is so rapid that hundreds, sometimes thousands, of cells are produced
in a matter of hours.