Biol 303: Lecture 1 Study Questions
1. Define the following terms (use your own words): development, growth, differentiation,
histogenesis, organogenesis, morphogenesis, reproduction, tissue, organ, organ system, and
Development: is the growth of an individual organism from a simple to a more complex or
mature level. A slow process of progressive change
Growth: process of an organism growing organically. Cells divide
Differentiation: a process by which a less specialized cell become a more specialized cell type,
becomes different during development. Cellular diversity. The generation of specialized cell
Histogenesis: is the formation of different tissues from undifferentiated cells. Constituents of
the endoderm, ectoderm, and mesoderm. The development of tissue cells from an embryonic
Organogenesis: is the process by which the endoderm, ectoderm, and mesoderm develop into
internal organs of the organism
Morphogenesis: differentiation and growth of the structure/shape of an organism
Reproduction: the process of generating an offspring
Tissue: part of an organism consisting of aggregate cells having a similar structure and
Organ: a fully differentiated structural and functional unit that is specialized for a specific
Organ system: is a group of organism that work together to perform a certain task, such as the
circulatory system, respiratory system, the nervous system
Organisms: a living thing that has the ability to act or function independently
2. Distinguish between growth and differentiation. Give an example where each occurs
independently of the other.
3. Explain the following statement: "The entire life history of animals is cyclical."
The entire life history of animals is cyclical refers to the fact the life is a cycle with a continuous
repetitive process. Fertilization→ Cleavage →Gastrulation →Organogenesis →Larval
Stages→ Maturity →Gametogenesis →Fertilization…
4. What are the (two) major questions that are addressed by the discipline of developmental
• How does adult organism develop from one cell?
• How does adult organism produce another organism?
5. Define (explain what it is) the following terms: chemotaxis, resact, agglutination (of sperm to
jelly coat), capacitation, acrosome, bindin, acrosomal filament (process), activation (of the Biol 303: Lecture 1 Study Questions
egg), cortex (of an egg), cortical granules, vitelline envelope or membrane, fertilization
envelope or membrane, zona pellucid
Chemotaxis: is when an organism directs their movement according to certain chemicals in the
environment. i.e. the attraction of the sperm towards the egg. It happens as a result of a
chemical gradient which is secreted by the egg which the sperm follows.
Resact: is a 14amino acid peptide isolated from the egg jelly of the sea urchin which provides
the sperm with direction towards the egg. Sperm has receptors for resact, which is why they
swim up the gradient. Binding of resact causes the sperm to activate Calcium Channels which
is activated by cGMP, made by the sperm. Calcium enters the sperm cell from the seawater,
which provides a directional cue to the sperm.
The egg releases chemicals for which the sperm follows to get to the egg, known as
chemotaxis. Resact, an amino acid peptide binds to the sperm which regulates calcium
channels, which increases the concentration of calcium in the sperm cell that are responsible
for regulating direction. The fusion of the acrosomal vesicle with the sperm cell and then the
extension of the acrosmal process and finally, the digestion of the jelly layer.
Agglutination (of sperm to jelly coat): Species-specific binding of acrosomal process to egg
surface in sea urchins.
Capacitation: maturation of sperm, newly ejaculated sperm cell cannot undergo acrosomal
reaction or fertilize an egg. The sperm undergoes a set of physiological changes or molecular
events mostly involving sperm cell membrane to which the sperm becomes competent to
fertilize the egg. The sperm cell membrane is altered by the removal of cholesterol on the
sperm surface are lost. The membrane potential of the sperm cell membrane becomes more
negative as potassium ions leave the sperm. This may allow calcium channels to open and let
calcium enter the sperm cell. Finally, the outer acrosomal membrane changes and comes into
contact with the sperm cell in a way that it prepares it for fusion.
Acrosome: is derived the cell’s Golgi apparatus and contains enzymes that digest proteins and
complex sugars. Can be considered a modified secretory vesicle. The enzymes stored in the
acrosome are used to digest a path through the outer coverings of the egg. G actin proteins lie
in between the sperm nucleus and the acrosomal vesicle.
Bindin: a protein in the acrosomal process which is responsible for recognizing the egg, since it
has receptors on the egg cell membrane. They are species specific.
Acrosomal filament: the interaction between the sperm and the egg jelly results in the
acrosome reaction. 2 components of acrosomal reaction: 1) the fusion of the acrosomal vesicle
with the sperm cell membrane, the release of contents of the acrosomal vesicle (exocytosis).
2) the extension of the acrosomal process. The portion of the acrosomal membrane lying
directly beneath the sperm cell fuses with the cell membrane to release the acrosomal vesicle
contents. The actin molecules assemble to produce microfilaments, extending the acrosomal
Activation (of egg): The egg jelly is a glycoprotein matrix (a mesh) that is involved in the sperm
attraction and activation. Biol 303: Lecture 1 Study Questions
Cortex (of an egg): a thin layer of gel-like cytoplasm beneath the cell membrane. Contains high
concentrations of globular actin molecules. During fertilization these actin molecules
polymerize to form long cables of microfilaments.
Cortical Granule: is within the cortex. Are membrane bound, golgi-derived structu