Biology 102 Study Test Questions
with 100% Correct Answers
Define a membrane potential and a resting potential - Answer- Membrane potential- due
to the different concentration of ions on the inside and outside of a cell. The plasma
membrane is electrically polarized with more negative charge inside the cell. Resting
potential- usually -70mV in an un-stimulated neuron
Distinguish between gated and ungated ion channels - Answer- Ungated channels are
open at all times. Gated channels open and close in response to stimuli, either chemical
(e.g., neurotransmitter release) or changes in membrane potential. These highly
selective channels allow only one kind of ion to pass through it
Describe the functions of the rod cells and cone cells of the vertebrate eye - Answer-
Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in
less intense light than can the other type of visual photoreceptor, cone cells. Named for
their cylindrical shape, rods are concentrated at the outer edges of the retina and are
used in peripheral vision. More sensitive than cone cells, rod cells are almost entirely
responsible for night vision.
Cone cells, or cones, are photoreceptor cells in the retina of the eye that are
responsible for color vision; they function best in relatively bright light, as opposed to rod
cells that work better in dim light. Cone cells are densely packed in the fovea, but
gradually become sparser towards the periphery of the retina.
Define the refractory period - Answer- The refractory period is the period when a neuron
is insensitive to depolarization. This sets the limit on the maximum frequency with which
action potentials can be generated.
Explain how an action potential is propagated along an axon - Answer- The
depolarization is regenerated all along the membrane. The refractory period prevents
re-excitation behind the action potential so that the action potential only moves in a
forward direction.
Explain why the action potential cannot travel back toward the cell body - Answer-
Because the inflow of K+ after action potentials deactivate the NA+ ion channel.
Distinguish between an electrical synapse and a chemical synapse - Answer- a.
Electrical synapse - allows action potential to spread directly from the presynaptic cells
to the postsynaptic cells.
, b. Chemical synapse - presynaptic and postsynaptic cells are separated by a synaptic
cleft. The action potential of the presynaptic cell is converted into a chemical signal that
travels across the cleft and is then converted back into an electrical signal in the
postsynaptic cell.
Distinguish between asexual and sexual reproduction - Answer- Normal cell division is
the basis for asexual reproduction. Only one type of cell is involved, with no input from
another individual. Because no new genetic material is involved, the offspring is a clone
of the parent. Example: Hydra. Fertilization is a random process involved in sexual
reproduction. Nuclei fuse and the resulting egg (zygote) has individual genetic makeup.
Variation is the key to the offspring. Example: Humans
Explain how hermaphroditism may be advantageous to animals that have difficulty
encountering a member of the opposite sex - Answer- An individual has both male and
female reproductive systems. It donates and receives sperm, which results in twice as
many offspring
Describe mechanisms that increase the probability of successful fertilization in
organisms that use external fertilization - Answer- In external fertilization, eggs are
released by the female into a wet environment, where they are fertilized by the male. In
species with external fertilization, timing is crucial to ensure that mature sperm
encounter ripe eggs. Environmental cues such as temperature or day length may cause
gamete release by the whole population. Individuals may engage in courtship behavior
that leads to fertilization of the eggs of one female by one male
Describe the basic structure of the male reproductive systems - Answer- Penis -The
penis is the male organ for sexual intercourse. It has three parts: the root, which
attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the
cone-shaped end of the penis.
Scrotum -The scrotum is the loose pouch-like sac of skin that hangs behind the penis. It
contains the testicles (also called testes), as well as many nerves and blood vessels.
The scrotum has a protective function and acts as a climate control system for the
testes.
Testicles (testes)- The testes are oval organs about the size of large olives that lie in the
scrotum, secured at either end by a structure called the spermatic cord. Most men have
two testes. The testes are responsible for making testosterone, the primary male sex
hormone, and for generating sperm.
Epididymis -The epididymis is a long, coiled tube that rests on the backside of each
testicle. It functions in the transport and storage of the sperm cells that are produced in
the testes.
Vas deferens - The vas deferens is a long, muscular tube that travels from the
epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports
mature sperm to the urethra in preparation for ejaculation.
Ejaculatory ducts - These are formed by the fusion of the vas deferens and the seminal
vesicles. The ejaculatory ducts empty into the urethra.
with 100% Correct Answers
Define a membrane potential and a resting potential - Answer- Membrane potential- due
to the different concentration of ions on the inside and outside of a cell. The plasma
membrane is electrically polarized with more negative charge inside the cell. Resting
potential- usually -70mV in an un-stimulated neuron
Distinguish between gated and ungated ion channels - Answer- Ungated channels are
open at all times. Gated channels open and close in response to stimuli, either chemical
(e.g., neurotransmitter release) or changes in membrane potential. These highly
selective channels allow only one kind of ion to pass through it
Describe the functions of the rod cells and cone cells of the vertebrate eye - Answer-
Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in
less intense light than can the other type of visual photoreceptor, cone cells. Named for
their cylindrical shape, rods are concentrated at the outer edges of the retina and are
used in peripheral vision. More sensitive than cone cells, rod cells are almost entirely
responsible for night vision.
Cone cells, or cones, are photoreceptor cells in the retina of the eye that are
responsible for color vision; they function best in relatively bright light, as opposed to rod
cells that work better in dim light. Cone cells are densely packed in the fovea, but
gradually become sparser towards the periphery of the retina.
Define the refractory period - Answer- The refractory period is the period when a neuron
is insensitive to depolarization. This sets the limit on the maximum frequency with which
action potentials can be generated.
Explain how an action potential is propagated along an axon - Answer- The
depolarization is regenerated all along the membrane. The refractory period prevents
re-excitation behind the action potential so that the action potential only moves in a
forward direction.
Explain why the action potential cannot travel back toward the cell body - Answer-
Because the inflow of K+ after action potentials deactivate the NA+ ion channel.
Distinguish between an electrical synapse and a chemical synapse - Answer- a.
Electrical synapse - allows action potential to spread directly from the presynaptic cells
to the postsynaptic cells.
, b. Chemical synapse - presynaptic and postsynaptic cells are separated by a synaptic
cleft. The action potential of the presynaptic cell is converted into a chemical signal that
travels across the cleft and is then converted back into an electrical signal in the
postsynaptic cell.
Distinguish between asexual and sexual reproduction - Answer- Normal cell division is
the basis for asexual reproduction. Only one type of cell is involved, with no input from
another individual. Because no new genetic material is involved, the offspring is a clone
of the parent. Example: Hydra. Fertilization is a random process involved in sexual
reproduction. Nuclei fuse and the resulting egg (zygote) has individual genetic makeup.
Variation is the key to the offspring. Example: Humans
Explain how hermaphroditism may be advantageous to animals that have difficulty
encountering a member of the opposite sex - Answer- An individual has both male and
female reproductive systems. It donates and receives sperm, which results in twice as
many offspring
Describe mechanisms that increase the probability of successful fertilization in
organisms that use external fertilization - Answer- In external fertilization, eggs are
released by the female into a wet environment, where they are fertilized by the male. In
species with external fertilization, timing is crucial to ensure that mature sperm
encounter ripe eggs. Environmental cues such as temperature or day length may cause
gamete release by the whole population. Individuals may engage in courtship behavior
that leads to fertilization of the eggs of one female by one male
Describe the basic structure of the male reproductive systems - Answer- Penis -The
penis is the male organ for sexual intercourse. It has three parts: the root, which
attaches to the wall of the abdomen; the body, or shaft; and the glans, which is the
cone-shaped end of the penis.
Scrotum -The scrotum is the loose pouch-like sac of skin that hangs behind the penis. It
contains the testicles (also called testes), as well as many nerves and blood vessels.
The scrotum has a protective function and acts as a climate control system for the
testes.
Testicles (testes)- The testes are oval organs about the size of large olives that lie in the
scrotum, secured at either end by a structure called the spermatic cord. Most men have
two testes. The testes are responsible for making testosterone, the primary male sex
hormone, and for generating sperm.
Epididymis -The epididymis is a long, coiled tube that rests on the backside of each
testicle. It functions in the transport and storage of the sperm cells that are produced in
the testes.
Vas deferens - The vas deferens is a long, muscular tube that travels from the
epididymis into the pelvic cavity, to just behind the bladder. The vas deferens transports
mature sperm to the urethra in preparation for ejaculation.
Ejaculatory ducts - These are formed by the fusion of the vas deferens and the seminal
vesicles. The ejaculatory ducts empty into the urethra.
