- Describe at least three reasons why it is worthwhile to study Mammalogy (your answer can, but does not have to be, be drawn from our discussion the first day of class). How is knowledge of mammalogy relevant to everyday life for someone who is not a scientist?
We gave you a lot of latitude in answering this question. We awarded 1 point for each of the three required reasons and 2 points for making clear how any of this knowledge might be relevant to everyday life.
- What is the role of the following structures in the development of homeothermy?
One point for each answer.
- Attachment of jaw muscles to zygomatic arch, rather than inside of temporal shield: allows for bigger cheing muscles without leaving less room for the brain. This in turn allows for more efficient processing of food.
- Four-chambered heart: A high-pressure system that delivers well-oxygenated blood efficiently to the tissues of the body, which is necessary to support a migh metabolic rate.
- Hair: Insulates against heat loss.
- Heterodont dentition: Allows more efficient processing of food and the ability to eat more different types of food.
- Muscular diaphragm: Allows more efficient respiration (brings in more oxygen to the circulatory to support a high metabolic rate).
- Enucleate erythrocytes: Can carry more oxygen inside them than a red blood cell with a nucleus because losing the nucleus makes more room for more hemoglobin molecules. This is necessary to carry higher concentrations of oxygen to the tissues to support the high metabolic rate.
- Sebaceous glands: Produce oil to lubricate hairs, which preserves them (and their abilityy to insulate). Also, in amphibious mammals, the oil makes hair waterproof which makes it capable of insulating even when the animal is submerged.
- Secondary palate: Separates the nasal and oral cavities, allowing mammals to breathe and chew at the same time. This allows the mammal to bring in more oxygen and more food in support of their high metabolic rate.
- Sweat glands: Produce a watery secretion which, through its evaporation from the surface of the skin, cools the body when wnvironmwntal temperatures are high.
- Two occipital condyles: provides more flexibility of head and neck, giving mammals increased agility, and making them better at capturing prey
- What were the earliest mammals like, in terms of size, diet, behavior and physical characteristics? How do we know?
They were small (we know from fossil evidence), insectivorous (inferred from the shape of their teeth), nocturnal (inferred from fossil evidence of enhanced senses of smell and hearing, and diminished sense of vision), had good hearing (because of three ossicles in middle ear), had a good sense of smell (lots of brain space devoted to it and long rostrum for additional sensory epithelium), laid eggs (like reptiles and monotremes; an ancestral trait), had mammary glands and hair (universal mammalian traits assumed to be ancestral; also fossil evidence of hair in dinosaur feces).
You received 1/2 point for each description and another 1/2 point for indicating how we know. If you had at least 5 complete characteritics, you received full credit.
- Describe the origins of the three bones in the mammalian middle ear. What are the homologous bones in the reptilian ancestors of mammals? What were their functions in mammal-like reptiles and what are their functions now in modern mammals?
The three ossicles (malleus, incus and stapes) originate from the reptilian articular, quadrate and stapes bones (3 points). In reptiles, the articular and quadrate bones were the jaw articulation point and the stapes was the sole ossicle, used for hearing (1 point). In mammals, all three bones function in transmitting sound from the tympanic membrane (ear drum) to the inner ear, so that mammals have very accute hearing (1 point).
- Compare and contrast the dentition and digestive system of a myrmecophagous mammal with that of a sanguinivorous mammal. What accounts for the similarities and differences?
| Mode of foraging
| Teeth
| Tongue
| Stomach
| Intestines
| Cecum
|
| Myrmecophagy
| absent or reduced in numbers, peg-like
| extremely long and sticky with saliva
| often roughened
| short
| small or lacking
|
| Sanguinivory
| very sharp upper incisors; reduced cheek teeth
| grooved
| tubular, highly extensible
| long
| lacking
|
Similarities are reduced teeth (because there is little processing of food in the mouth), and lack of a cecum (because animal matter is easy to digest).
Differences include the stomach (roughened in myrmecophagous species for crushing expskeletons; tubular and distensible in sanguinivorous mammals for holding large volumes of blood), presence of sharp incisor teeth in sanguinivorous mammals for blood-letting, differences in tongue length based upon thier different roles in ffood gathering (long and sticky for myrmecophagous mammals for sticking into ant nests and termite mounds, shorter and grooved for slurping blood in sanguinivorous mammals).
I gave you 1 point for describing teeth, 1 for tongue, 1 for stomach and 1 for intestines/cecum. The final point was for your answer to what accounts for the similarities and differences.
- What pigments are responsible for the colors and coloration patterns we see in living mammals? How do they create the colors that we observe?
Eumelanin produces black coloration (in high concentrations) to brown coloration (in low concentrations) (1 and 1/2 pt). Pheomelanin produces red coloration (in high concentrations) to yellow concentrations (in low concentrations)(1 and 1/2 point). The absence of either pigment produces white hair (1 point). Many "brown" mammals actually have agouti coloration, alternating stripes of eumelanin and pheomelanin on a single hair shaft (1 point).
- Name and describe three mechanisms of dispersal (the general ways that mammals can colonize new habitats). Give an example of dispersal across each type. Your example can be real or hypothetical, and should consist of a description of the type of barrier and how your chosen
- Corridor route: Little or no barrier to disperal; most mammals can get across (e.g., horses going across the Bering land bridge)
- Filter route: Some barrier to dispersal so that only some mammals can cross it (e.g., tectonic shifts cause a mountain range to spring up where there had once been an open plain, creating a barrier to dispersal for small mammals)
- Sweepstakes route: a dispersal path that is due to chance, so that only a very tiny percentage of mammals can get across (e.g., rafting, where a small mammal gets swept across a large body of water by clinging to floating debris)
You received 1 point for naming and describing each type of route and another 2 points for giving plausible examples. Any example was okay as long as it was well justified and appropriate (and thank you for the fanciful ones - those make a long night of grading a lot more enjoyable!). I also gave pretty liberal extra credit in cases where it appeared the meaning of the question wasn't clear but you gave me good factual information about dispersal in general.
