- Differentiate between CF and FM types of echolocation in bats. How do
these vocalizations change as the bats approaches an insect it is trying
catch? Why do the calls change as the bat approaches the insect?
(1 point) CF stands for constant frequency. The calls tend to be long in
duration and have the same pitch for most of the call.
(1 point) FM calls are frequency modulated. They are shorter in duration
that CF calls and the pitch changes dramatically from beginning to end of
the call (usually going from high to low).
(2 points) No matter which type of call the species typically makes, the
calls get shorter, closer together (higher calling rate), and more frequency
modulated as the bat approaches the insect it is trying to catch.
(1 point) The calls change because FM calls provide more detailed
information about the size and shape of the insect and because short, rapid
calls are better at providing information on something that is close and
rapidly getting closer.
- What role do the hormones Estrogen (E), Progesterone(P), Growth Hormone
(GH) and Prolactin (Pr) play in lactation? Compare the levels of these
hormones in the following three situations: (1) during pregnancy, (2) after
birth, when offspring survive and (3) after birth when no offspring survive.
(2 points) During pregnancy, E and P are produced in high concentrations by
the ovary. They stimulate the mammary gland to become larger and stimulate
the pituitary to release GH, which also makes the mammary gland grow.
(2 points) After birth, the ovary stops secreting E and P, which allows the
pituitary to secrete Pr. Pr and GH act on the mammary gland to induce it to
produce milk. Suckling by offspring creates positive feedback to the
pituitary (through the hormone oxytocin) that stimulates more release of GH
and Pr to maintain milk production.
(1 point) After birth, if no offspring survive, there is no suckling
stimulus to provide positive feedback to the pituitary, so Gh and Pr
secretion go down and milk stop being produced.
- Why would a fetus need some sort of protection from the motherÕs immune
system? How does this affect mode of reproduction and length of gestation in
(a) monotremes, (b) marsupials and (c) placental mammals?
(2 points) The fetus gets half its genome from its father, so it is not
genetically identical to the mother. The mother's immune system is highly
developed to distinguish self from not-self and attack anything not-self, so
the fetus would be vulnerable to attack by the mother's immune system.
(1 points) Monotremes lay eggs, so there is complete physical separation of
the fetus from the mother's immune system.
(1 point) Marsupials have a shell membrane that provides physical separation
of the fetal and maternal tissues for about 2/3 of gestation, but after the
developing embryo cracks through the shell membrane, it is vulnerable to
attack. This limits the length the length of gestation in marsupials,
because birth follows soon after the shell membrane disappears.
(1 point) Placental mammals have a trophoblast (part of the placenta) that
provides some physical separation and also produces substances that disrupt
the functioning of the maternal immune system, preventing it from attacking
the fetus. This allows a much longer gestation length.
- Which two orders have venomous representatives? How do they differ in the
location of the venom glands and the function of the venom? WeÕve discussed
the function of venom in one of these orders in class; the other you will
have to speculate on.
(1 point) Soricomorpha (shrews) and Monotremata (the platypus) have venomous
representatives.
(1 point) Shrews make venom in submaxillary glands (modified salivary
glands) at the base of their lower incisors.
(1 point) The platypus makes venom in a gland located on their thigh. (NOT in
the spur!)
(1 point) The venom of shrews is used to immobilize prey that are bigger in
body size than the shrew.
(1 point) The venom of the platypus is used in male-male fighting.
- Give your opinion as to whether marsupials are inferior to placental
mammals. Be sure to support your opinion with factual evidence.
To get full credit, you needed to give at least 2 reasons and support them well with reasoning,
evidence or examples.
For yes:
- Less diversity of habitat types (Their mode of reproduction limits the
environments in which they can live.)
- Less diversity of locomotion
- Less diversity of foraging
- No really big marsupials
- Social organization is less complex (related to smaller cerebral cortex,
less able to learn, less flexible behaviorally)
- Not as speciose
- Most diverse and numerous in Australia, where there is negligible
competition with eutherians
For no:
- Low energy requirements, spread out of a long period of time
- Can quickly replace lost young
- How do choriovitelline and chorioallantoic placentas differ? How do
these differences affect nutrient transfer and gas exchange?
(2 points) Choriovitelline placentas have fusion and vascularization of the
chorionic and vitelline membranes. The surface of the membranes are
convoluted for greater surface area, but there is limited diffusion of
nutrients and gases across the placental membranes. The yolk sac is very
large and contains most of the nutrients needed for the growth and
development of the fetus.
(2 points) Chorioallantoic placentas have fusion af the chorionic and
allantoic membranes. The allantois is highly vascularized and the fused
membranes have villi (small projections that work their way deep into the
uterine lining). This allows closer proximity between the maternal and fetal
circulatory systems, so there is more diffusion of nutrients and gases
across the placenta. The yolk sac is still present during early development,
but most of the nutrients needed for growth and development come from the
maternal circulation.
(1 point) Basically the choriovitelline polacenta is not as efficient as the
chorioallantoic placenta for gas and nutrient exchange.
- A phylogenetic analysis can result in groups that are monophyletic, paraphyletic or polyphyletic groups. Provided a definition for each of these terms. You can include a diagram if it helps you clarify your verbal definition. Based upon recent molecular data, which of these terms best describes the Order Chiroptera? Based upon recent molecular data, which of these terms best describes the group we formerly called the Order Insectivora? (10 points)
Monophylectic groups are those that include the most recent common ancestor of all the species in the group and every descendent species of that common ancestor (with no descendents excluded). (2 points, but partial credit if you got one piece of it but did not include all parts of the answer).
Paraphyletic groups are those that include the most recent common ancestor of all the species in the group and some, but not all, of the species descending from that common ancestor. (2 points)
Polyphyletic groups consist of a collection of species that may share traits but the most recent common ancestor is not included in the grouping. (2 points)
Excellent definitions can be found at
http://www.ucmp.berkeley.edu/glossary/gloss1/phyly.html
Based upon recent molecular data (e.g., Murphy et al 2001), the Chirpotera appear to be monophyletic (2 points). The former Insectivora are probably polyphyletic because recent genetic analyses split them up into two very distantly related groups, one that clusters with the Afrotheria and one that clusters with groups that evolved in the Northern hemisphere. (2 point).
NOTE: You lost points if any of your description led me to believe that you didn't fully understand these concepts. Common problems were confusing traits with species (e.g., "a monphyletic group cosists of homologous traits"), confusion over the most recent common ancestor (e.g., "a polyphylectic group is a collection of organisms that don't share a common ancestor", confusing evolution of traits with the evolution of species (e.g., "the species had independent origins"), and confusing "most recent" with "recent" (e.g., "monophyletic groups are those that share a recent common ancestor"). Also, while the use of convergent traits may lead you to a polyphyletic grouping, it is possible to get polyphyletic groups in other ways (e.g., by too much reliance on shared ancestral characteristics, as in the former Insectivora).