Overall structure is similar to humans, but again there are differences. Some features that are unique to mammals: Found in eutherian mammals.

Transcription

1 Mammalian anatomy and physiology (part II): Nervous system: Brain: Sensory input: Overall structure is similar to humans, but again there are differences. Some features that are unique to mammals: Smell: Hearing: Increased cerebellum Note that surface area (cerebral cortex) is tied to intelligence, not overall weight/mass of cerebrum. Corpus callosum Method to communicate information between the right and left sides of the brain. Found in eutherian mammals. Overall, mammals rely more on learning and intelligence than other groups Brain can be responsible for a large amount of the energy needed by an animal. For most mammals (and in general for most animals), smell is probably the most important sense. Huge part of the brain is utilized to interpret olfactory information. Strangely, even mammals that don't have a good sense of smell have roughly the same number of different type of receptors, just not as many of each. Primates generally don't have a good sense of smell. Porpoises and dolphins don't have an olfactory system. Ear structure is essentially similar to that in humans. Outer ear/middle ear/inner ear

2 Vision: Vibrissae: Associated with the ear are the semi-circular canals (detect motion) and the utricle and saccule (detect direction). Bats can hear sounds at very high frequencies - used for echolocation. More on this later in the semester. Also used by dolphins and whales. Elephants and giraffes hear sounds at very low frequencies. Can use these frequencies to communicate. Basic eye structure is similar. Tapetum - reflective layer on choroid that improves night vision. In nocturnal mammals (strictly diurnal mammals don't have this). Reflects light back through retina. Rods and cones are found in all groups: Rods - b & w, more sensitive to light (night vision). Cones - color, less sensitive to light. Extent of cones (and types) varies widely among mammals. Primates have excellent color vision Nocturnal mammals generally poor color vision (but it varies). Some groups (e.g., moles, some rodents) have greatly reduced eyes. Whiskers by any other name... Sense obstructions/provide tactile feedback. Generally on the face, but also found elsewhere (legs). Not found in all mammals

3 Skeletal system: Provides for support and movement (often discussed in tandem with nervous system). Again, if you know the human skeleton, you probably know most of what you need. Skull: Teeth: Some bones are obviously highly modified based on the type of animal: Wing bones in bats made up of fingers. Leg and arm bones in many ungulates fused. Know the names of the bones (see figure 2-15, p. 30 of text). (Note clavicle is almost missing in dogs). The skull is diagnostic in mammals (allows identification of species). Oddly, the text doesn't mention one of the most diagnostic features of the mammalian skull: Two occipital condyles - articulation joint of skull on vertebral column. Most other vertebrates have only one (with the exception of a few odd amphibians). Made up of a number of bones that have fused (or better, fuse as the animal grows up). Notice figure Guess what - yes, you need to know these bones (consider it part of lab). They really are used a lot in various keys. Obviously very important for most mammal groups. Mammal dentition is mostly heterodont, meaning that the teeth are different (and function differently):

4 Incisors - usually used to grab food (e.g., grasses, etc.) Canines - used to grab and kill, but also for displays. Premolars & molars - grind or cut food. Deciduous dentition: Milk teeth are first teeth. These are shed and replace by adult teeth. Molars are (usually) only found in adults. Adult and juvenile dentition is sometimes quite different. Teeth (particularly molars and premolars) are highly adapted to the type of diet: Broad grinding surfaces in herbivorous animals (e.g., horses or elephants). Sharp cutting surfaces in carnivorous animals (best seen in cats) Intermediate surfaces in omnivores (e.g., humans, pigs, bears). See below for specific names of tooth types. Text has considerably more details on the structure of cones and cusps. Feel free to read through it on your own, but it's way more than we probably need. Dental formulas: All mammals can be described by their dental formula. This is a way of describing all the teeth present in a particular species (usually a family (or sometimes order) will have identical dental formulas: Example: 3/3 1/1 4/4 2/3 Ursidae Shows: 3 incisors, upper and lower jaw 1 canine, upper and lower jaw 4 premolars, upper and lower jaw 2 molars, upper jaw, 3 molars lower jaw

5 This is only for half the jaw (the other half is obviously the same) 0/3 0/1 3/3 3/3 Most ruminants (suborder ruminantia) Note that some teeth may be missing all together (how many deer really need canines?? You will be given dental formulas for all families discussed - you'll need to memorize these. Other terms associated with teeth: diastema - gap between incisors and cheek teeth (rodents, ungulates) hypsodont - high crowned tooth - found in many herbivores bunodont - tooth separated into hilly cusps (e.g., primates, pigs, etc.) lophodont - cusps are straight (more or less) across the top of the tooth selenodont - cusps similar to lophodont, but more curvy and crescent shaped. carnassial - text mentions this is a subset of sectorial, but many people use this terms instead of: sectorial - slicing teeth found in bats, carnivores, etc. Comment: if you think this is a lot of stuff on teeth, see your text!