1. Analyze the relationship between the
intelligence of mammals, the variety of habitats and ecological niches mammals
occupy, and the relatively small number of species of mammals.
2. Summarize the evolution of the three lines
of mammals during the last half of the Mesozoic era.
3. Briefly describe mammal evolution during
the early Cenozoic, and state why this rapid adaptive radiation was able
to occur at this time.
4. Name the sense which was probably most highly
developed in early mammals, and relate this to their habitat and life style
in general.
5. Describe the following mammalian characteristics
and relate each of these to survival and adaptive values, advantages or disadvantages:
homiothermy, endothermy, hair, fat, apocrine glands, eccrine glands, mammary
glands, muscular diaphragm, non-nucleate red blood cells, four chambered
heart, uterus, placenta, scrotum.
6. Summarize the adaptive trends of the mammals.
(increase in body size, decrease in number of teeth, increase in length and
strength of legs, increased radiation into new habitats, increase in size
of brain.)
7. List the orders of mammals. State the distinguishing
characteristics of each order and give common representatives of each.
8. Define terms herbivorous, carnivorous, insectivorous
and omnivorous. Name some animals in each group.
9. Name some migrating species of mammals and
describe the extent of their migrations and reasons for migrating. State
differences between mammalian migration and bird migrations.
10. Distinguish between the so-called hibernation
of bears and true hibernation as it occurs in such animals as ground squirrels.
11. Summarize the factors which influence the
size of a home range or territory that an individual mammal may claim.
12. Outline a typical estrus cycle and describe
variations in this cycle in different species.
13. List and briefly describe the mammalian
characteristics which are superior to those of the reptiles.
14. Describe the dentition of mammals as a
classification tool.
15. Define the terms diphyodont, homodont,
and heterodont.
16. Describe the four kinds of teeth and their
functions for the animals that posses them.
17. Describe the different strategies of thermoregulation
displayed by mammals. Explain why thermoregulation on land is a much bigger
concern than for any aquatic organism.
18. Differentiate between winter sleep and
hibernation. State mammals that participate in each.
Resources: Text: Animal Diversity, Chapter
20
Internet Resources
http://www.ucmp.berkeley.edu/mammal/mammal.html
http://www.mhhe.com/hickmanad4e
PHYLUM CHORDATA: CLASS MAMMALIA
"What is man without the beasts? If
all the beasts were gone, men would die
from a great loneliness of the spirit.
For whatever happens to the beasts
soon happens to man." Chief Seattle
1854
Class Mammalia (mamma- "breasts") ~4500
species
-diverse, most successful with exception
of insects
-Human most dominant and manipulative species; naive
-Unmistakable characteristic --->
Hair, despite combo of adaptations, doubtful that
mammals would have triumphed without
hair
Class Mammalia- mammary glands;
hair, diaphragm, 3 middle-ear ossicles;
heterodont dentition; sweat, sebaceous
and scent glands; four-chambered heart;
large cerebral cortex.
SubClass Protheria (6 species)
Monotremes (refers to cloaca
which other mammals lack)
-oviparous (duck billed platypus)
SubClass Theria (wild beasts)
Infraclass Metatheria- viviparous,
young born early and carried in pouch.
Marsupials (~250 species)
Infraclass Eutheria- complex
placenta; young develop to advanced stages
prior to birth. Placentals
(~3800 species)
EXTERNAL STRUCTURE/LOCOMOTION
Hair -keratinized derivative
of epidermis of skin; uniquely mammalian
-hair follicle, invagination
of epidermis
Coat of hair called pelage
:
1. underhairs for insulation, dense
coat, smaller
2. guard hair- long, protective
against wear and provides color
Hair grows continuously, as cells
become carried away from follicle they die.
Hair must be periodically molted
-humans, molting occurs gradually,
not noticed
-in others, hair loss occurs
rapidly and may result in altered pelage
characteristics Ex. fall,
thick coat of underhair, color may change
Hair is important to sense of touch,
mechanical displacement of hair stimulates
nerve cells associated w/hair roots.
Vibrissae- roots richly innervated, "whiskers", occur around mouth, legs, nose, eyes.
Air space in hair shaft and air trapped
between hair and skin provide insulation
Arrector pili muscles- smooth
muscles running between hair follicle and lower
epidermis
-when muscle contracts --->
hair stands up increasing amt. of air trapped
-under control of autonomic
nervous system, fight or flight; increased size and
strength
Hair color- dependent on amt. of
pigment (melanin) deposited in it and quantity of
air in hair shaft.
-most animals dark above, lighter
underneath, makes animal less conspicuous
under most conditions
-warning coloration- contrasting
markings (skunk)
Modifications- porcupine; reduction
in warm and aquatic environments
Glands- develop from epidermis;
**mammals have greatest variety of integumantary
glands
1. Sweat glands (sudoriferous)
-small glands (eccrine) -->
water secretions, evaporative cooling
-large glands (apocrine
) --> mixture of salt, urea and water; converted to odorous
products by microbes on skin.
-associated w/hair follicle
-not cooling primarily --> rather
sex recognition
2. Sebaceous glands- associated
w/hair follicle
-oily, lubricate and water proof
skin and hair
-Sebum- "dressing", "polite fat", (does not turn rancid)
-humans ---> most numerous in scalp and face
3. Scent or musk glands
-face, feet, or anus of many mammals
-secrete pheromones, defensive,
species and sex recognition, territorial behavior
(cat)
4. Mammary glands- functional
in females
-secrete milk containing water,
carbos (especially lactose), fat, protein, minerals and
antibodies
-monotremes have mammary glands
that lack nipples
TEETH/FEEDING- reveal life style of animal with relation to what they eat
Diphyodont- two sets of teeth
first set ---> deciduous or milk
teeth
second set ---> premanent
In reptiles all teeth uniform
(homodont)
Mammals ---> teeth often specialized
for different functions (heterodont)
4 kinds of teeth:
1. Incisors- most anterior in
jaw, usually chisel-like and used for gnawing or nipping
2. Canines- often long, stout,
conical, usually used for catching, killing and tearing
prey. Piercing
*canines and incisors have single
root
3. Premolars- positioned next
to canines, have one or two roots and are truncated
(cusped) for shearing and tearing
4. Molars- broad chewing surfaces and two or three roots
Mammalian species have characteristic numbers of each kind of adult tooth
Dental Formula- expression
of # and kind of teeth in upper and lower jaw in this
order: Incisors, canines,
premolars, molars
Human ---> 2 . 1 . 2
. 3
2 . 1 . 2
. 3 (either right or left half)
Specialized for particular diet:
Omnivores- eat both plant and
animal
Anterior teeth with ripping piercing
surfaces
Posterior teeth with flattened,
grinding surfaces
Herbivores- eat plant material,
browsers, grazers
Posterior teeth w/flat grinding
surfaces
Incisors and sometimes canines modified
for nipping plant matter (horses, deer)
Rodents- gnawing, incisors
grow throughout lifetime
In rodents only front surfaces covered
w/ enamel, kept sharp by wearing back
surface down
Carnivores- feed on other animals
Canines and Incisors used for catching,
killing and tearing prey
Fourth upper premolars and first
lower molars form scissor like shearing
surface (order Carnivora: dogs,
coyotes, cats)
Insectivores- feed on insects
some w/ no teeth. Anteater uses
long tongue covered w/sticky saliva to capture prey
THERMOREGULATION
-mammals exposed to harsh environmental
conditions (specifically temp)
-nearly all face conditions requiring
them to dissipate excess heat at some time and
generate and conserve heat at others
-characteristic allowing them to survive
when dinos did not (+hair)
Shivering thermogenesis- muscular
activity that results in generation of large amounts
of heat, but little movement
Nonshivering thermogenesis- heat
production by cellular metabolism (homeothermy)
-fat deposits are energy sources that
help sustain high metabolic rates
-Pelage- insulation
-sweating cools
-restricting blood flow; protecting
poorly insulated appendages help conserve heat.
WINTER SLEEP/ HIBERNATION
Winter sleep- animals become less active
but are still relatively alert, easily aroused.
Body temp. and metabolic rates decrease
somewhat but they do not necessarily
remain inactive all winter (bears,
raccoons)
True hibernators- duck-billed platypus, moles, shrews, chipmunks, bats, are but a few.
HIBERNATION- period of winter
inactivity in which hypothalamus of the brain slows
metabolic, heart and respiratory
rates
-prep ---> accumulate large quantities
of fat
-upon retreat to burrow or nest, hypothalamus sets thermostat at ~2oC
Ground squirrel- respiratory
rates 100-200 breath/min down to 4/min;
heart rate 200-300 beats/min
down to 20 beats/min
-mammals may lose 1/3 to 1/2
of body weight
BEHAVIOR- complex behaviors enhance survival
*Communication
Visual- threats, tail wagging,
subordination
Pheromones- species and sex
recognition; induce sexual behavior, establish
territories; parent/young recognition
(harp seal), urine (dogs, rabbits);
skunks (defense)
Auditory/tactile
-herds ---> familiar (calm),
unfamiliar causes panic
-precopulatory "nosing"
-grooming reinforces social relationships
within groups
Territoriality
REPRODUCTION AND DEVELOPMENT
-viviparity
-mammals have definate times during the
year in which eggs mature and are capable
of being fertilized
-animals w/great control over environment
(humans) can produce anytime of year
(although still tied to physiological
cycles)
Estrous cycle- includes time when
female is behaviorally and physiologically receptive
(no bleeding or sloughing of uterine
lining usually occurs)
Hormonal control
Monoestrous- single yearly cycle, sharply seasonal; bears,sea lions, wild dogs (Africa)
Diestrous- two yearly cycles (domestic dogs)
Polyestrous- many yearly cycles (rats and mice, estrous cycles every 4 to 6 days!!)
Menstral cycle - humans, apes, monkeys
Mensus- sloughing of uterine lining
Embryonic Diapause- devel. arrested after first week or two; sea lions, marsupials
-allows young to be born when
resources favor survival
-also allows females to give birth
and mate within short interval
Gestation period- length of time young develop within female reproductive tract
Marsupials- 8-40 days (in pouch additional 60-270 days)
Eutherians- 20 days (some rodents)
to 19 months (elephant)
MIGRATION: -because most mammals
don't fly, fewer migrate; those that do migrate
shorter distances
-Barren ground
caribou 100-700 miles
-longest by seals
and whales
fur seals- So
Cal to Pribilof Island morth of Aleutian chain ~1700 miles
*similar stimuli for mammalian migrations as found in birds, Periodicity
*greater problems
because development and other obsticles can't be flown
over!