III. Short answer. Your answers will be graded based upon whether they are factually correct and complete. (worth 5 points each, unless otherwise specified)

1. 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 talked about four potential reasons on the first day of class:

· Context- we are mammals, helps us to better understand ourselves

· Practical- we get disease from mammals, we use them to study our diseases (biomedical research), they protect us, work for us, eat our crops etc.

· Scientific- mammals are good models for the study of general scientific principals (eg. evolution, molecular genetics, etc.)

· Conservation- mammals are important part of many ecosystems, many are endangered. understanding the context of human evolution, practical considerations, conservation-related reasons and the value of studying mammals in basic scientific inquiry.

To get full credit you needed to touch upon at least two of these categories and provide supporting evidence (specific examples and details).

You received 3 points for the importance of studying mammalogy and 2 points for stating how the knowledge of mammalogy is relevant to non-scientists (either as a separate statement, or clearly imbedded in the reasons you listed).

2. Compare and contrast the dentition and digestive system of an herbivorous mammal with that of a terrestrial carnivore. What accounts for the similarities and differences?

For herbivory (2 pts total), the following were worth 1/2 pt each:

· incisors robust or lacking (I accepted either or both)

· lack of canines (resulting in a diastema)

· enlarged cheek teeth

· complex stomach

· long intestinal tract

· large cecum

For terrestrial carnivory (2 points total), the following were worth 1/2 pt each:

· Carnassial pair

· Elongated canine teeth

· Crushing molars

· Simple stomach

· Short intestinal tract

· Small cecum

Because plant material is harder to digest! (1 point)

3. Give three functions of hair that are related to its structure and two functions of hair related to its color.  For each function, give one example (common name of animal and a description of how the hair serves the stated function).  Use appropriate terminology for hair structure in your answer.

1 point for each (1/2 point for function, ½ point for example)

STRUCTURE (some possible examples)

Insulation – sheep’s wool has angora growth, fine curly texture that traps air

Protection – pocupine has spines that are long, stiff and have barbs on their tips

Sensory reception – sea lion has long, stiff hairs that have many nerve endings near the root of the hair (e.g., vibrissae)

Protection - human hair covers head, which has greatest exposure to UV solar rays

Waterproofing – otter has thick hair that is covered in oil produced in sebaceous glands associated with the hair follicle

Protection – guard hairs on a dog are relatively stiff and long, protecting the shorter, finer underhairs below them.

Protection – the bristles on a lion’s mane may help protect it’s neck from injury during fights with other males

COLOR (some possible examples)

Warning coloration – stripes on a skunk warn of noxious chemicals produced by skunk when disturbed

Crypsis – color of mouse matches the background substrate (blonde on beach, dark in woods)

Disruptive coloration – stripes on antelopes face (or mask on a raccoon) make it hard to distinguish where eyes are located

Disruptive coloration – stripes on a zebra make it hard for a predator to distibguish on individual from another

Protection from UV rays – dark hairs absorb UV rays from sun and protect skin cells

Heat reflection – white hairs of a desert antelope reflect solar radiation

Other examples are also possible.

4. What is homeothermy? What kinds of evidence do we have that the first mammals were homeothermic?

Homeothermy is the ability to maintain a constant body temperature (1/2 point) independent of environmental temperature (1/2 point).

Evidence could come from the following:

· hair for insulation

· traces of turbinal bones that warm and moisten air

· secondary palate that allows simultaneous breathing and chewing

· more efficient food processing (heterodont dentition, mandible composed of a single bone=the dentary, denatry/squamosal jaw articulation, changes in jaw muscle attachment)

· more efficient food gathering ability due to specializations of the atlas/axis, loss of cervical and lumbar ribs, more accute senses because of turbinal bones and/or 3 ossicles, etc.

· nocturnal, based upon reliance on smell and hearing (evidence=expanded olfactory and auditory portions of the brain, turbinal bones in rostrum, 3 ossicles)

Simply describing the first mammals with no explanation of how that characteristic related to homeothermy (e.g., small body size, insectivorous) was not sufficient. Describing a characteristic that was inferred without mentioning the evidence that it is inferred from (e.g., nocturnal) was also insufficient. 


5. Describe the changes in jaw structure and hearing apparatus that accompanied the evolutionary transition from reptiles to mammals.

Reptiles had a mandible composed of several bones including the dentary bone and the articulation with the cranium was between the atricular and quadrate bones. There was a single ossicle involved in sound transmittance, the stapes. In mammal-like reptiles, the dentary bone expanded and the postdentary bones became smaller. The law articulation varied, but a new articulation point formed between the dentary bone and the squamosal bone. The aricular and quadrate bones became involved in transmitting sound. In mammals, the dentary bone is the sole bone in the mandible and articulates with the squamosal bone. The bones formerly involve in jaw articulation (articular and quadrate) joined the stapes to form the 3 ossicles of the mammalian middle ear, which serve to transmit sound, resulting in increased auditory acuity. 



Points were awarded as follows:
Explanation of changes in dentary bone (1 point)
Explanation of changes in jaw articulation (including naming the bones involved in reptiles and mammals) (2 points)
Explaining the derivation of the 3 ossicles and their impact on hearing (2 points)

6. In 1693 John Ray proposed that mammals included those animals that (1) had blood, (2) breathed with lungs, (3) had 2 ventricles in their heart and (4) were viviparous. Evaluate this definition based on your knowledge of mammalian characteristics. Is this definition effective in differentiating mammals from other vertebrates? Which (if any) parts of Ray's chosen characteristics are diagnostic of mammals? Which current mammalian orders would be excluded from his definition?

Each component of the definition considered alone is not effective in differentiating mammals from other vertebrates.  None of the listed characteristics taken by itself is diagnostic. (2 points) All vertebrates have blood, all terrestrial forms breathe with lungs, birds and crocodilians have two ventricles, some other vertebrates give birth to live young.  (1 point)

However, taken as a whole the definition successfully excludes all non-mammals because the ones with 2 ventricles all lay eggs. (1 point)

This definition excludes the monotremes because they lay eggs and are not viviparous. (1 point)

7. Compare the morphology of the limbs and tails of amphibious, aquatic and marine mammals.

	Forelimbs	Hindlimbs	Tail
Amphibious	(often) webbed	webbed	flattened to form a paddle for propulsion
Aquatic	modified into flippers	modified into flippers	not externally visible
Marine	modified into flippers	highly reduced; not externally visible	flattened dorsoventrally for propulsion

The information contained in each cell was worth 1/2 point.