Fall 2004 - Sonoma State University
Exam 2 key
1. Define the following terms. Make your definitions brief and to the
point. (5 pts each)
1a. parthenogenesis- production of offspring without
fertilizing the egg. Can
happen with meiosis, as in male production in wasps, or without meiosis, as in
female offspring production during summer in aphids.
1b. tympanum- one of several hearing
organs found in insects. Consists of aggregations of other hearing organs (i.e. chordotonal and/or subgenual
organs). Can be
found on abdomen or on legs.
1c. spermatophore- a sac in which sperm are stored in the male
and passed to the female at mating.
1d. sexual selection- opposes natural selection. If a trait confers an advantage in mating, at
a cost with respect to other components of fitness, it may be under sexual
selection.
2. Name and briefly describe three different mechanical position receptors found in insects. (6 pts)
3.
a. Why do some insect receptors for sound often tend
to be similar to those for tactile reception?
b. Briefly describe an example of such a receptor. (6 pts)
Sound consists of pressure waves in a
fluid medium. Vibrations are detected by
the same receptors that would pick up other kinds of vibrations. An example of this is a trichoid
sensillum.
4. Briefly describe how the Malpighian tubules are connected to the digestive system
and how they function in excretion. (8 pts).
Malpighian tubules are
connected to the digestive system at the location where the midgut
connects to the hind gut. They sway
around in the hemolymph and are highly absorbtive.
Substances in the hemolymph are transported
into the lumen of the tubule, and then brought down the tubule to the gut. In the gut, wastes are sorted from useful
substances such as amino acids, salts, or water.
5. Name two (of four) substances that Malpighian tubules collect and describe what happens to those substances when they enter the hind gut. (8 pts).
6. Briefly describe two ways that a trichoid sensillum may be
modified for chemical reception. (6 pts).
The sensillum
contains many pores that allow entry of compounds into its interior. Dendrites
extend up into the sensillum to maximize contact with
chemicals.
7. Name and briefly describe two kinds
of chemical reception, indicate the medium through which the chemicals are
received, and name an appendage on which receptors may be located. (9 pts).
|
Kind of reception |
medium |
appendage |
|
Olfactory |
air |
antennae |
|
Gustatory |
water |
maxillary palps |
Olfactory reception tends to occur from
short to longer distances (up to a mile).
Gustatory reception occurs on contact with the solution that has a
particular ‘taste.’
9. Compare the function of ocelli and compound eyes in insects (6 pts.)
Ocelli are used to
detect changes in day length or to orient the insect. Compound eyes are used in navigation, prey
location, and predator avoidance.
10.
Name and briefly describe sexual selection that operates within one sex versus
sexual selection that operates between sexes. (6 pts).
Male-male competition- males compete
with one another for access to females, or male sperm compete for
fertilizations.
Female choice- Females select males
with certain traits (often with exaggerated versions such as the long stalks in
stalk eyed flies) to mate with.
11. How do females use nuptial gifts in
mate choice? (5 pts).
They use them directly as nutritional
resources. The quality of the resource
determines the attractiveness of the male as a mating partner. Often, this means that the size or mass of
the nuptial gift becomes an index of attractiveness, but it may also represent
an index of male quality, as males that can obtain higher quality gifts may
also possess ‘good’ genes.
12. How does storage of sperm in female
spermatheca offer an opportunity for sexual
selection? (6 pts)
Opportunities
exist for male competition among sperm cells- a race to be first to fertilize
eggs, or for males to attempt to place their spermatophores
in the most advantageous location, vis
a vis the sperm of other males.
13. Briefly
describe larval paedogenesis and explain why the
mother shouldn't be too upset about it (5 pts)
In larval paedogenesis, the eggs are activated and mature inside the
female larva, without fertilization.
They eventually consume her from the inside and emerge from her. Since these eggs are exact clones of the
female, her reproductive success may well be enhanced by ‘splitting’ into
several individuals rather than remaining a single individual.
14. Compare
the three main life history patterns found in insects with respect to kinds of
growth and kinds of life stages present.
Then provide a common name or order name of an insect that represents
that pattern. (9 pts)
ametaboly- these have indeterminate
growth, without a fixed number of molts before adulthood and with molts after
adulthood. There are eggs, immatures, and adults. An
example would be a silverfish (Thysanura).
hemimetabolous-
These have determinate growth, with a fixed number of immature molts before
adulthood. Eggs, nymphs, and adults
are found. An example would be a praying
mantis, an earwig, or a true bug (Dictyoptera, Dermaptera, or Hemiptera, respectively).
holometabolous- These also have
determinate growth, with a fixed number of immature molts before adulthood.
Eggs, larvae, PUPAE, and adults exist.
The pupa is a resting stage that does not eat while major internal
structural changes occur. An example would be a caddisfly,
butterfly, bee, beetle or fly (you know the names of these orders).
November 2, 2004 NER