MAMMAL NOTES. There are 4600 species of mammals known and 300 of these are considered endangered, mainly due to habitat destruction. General characteristics : 1. Mammals are endothermic ( mostly homeothermic )
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There are 4600 species of mammals known and 300 of these are considered endangered, mainly due to habitat destruction.
1. Mammals are endothermic ( mostly homeothermic)
2. Have hair or fur, if the coat of hair is thick, it is called pelage and species with
sparse hair usually have very
thick skin or a layer of blubber
to insulate against
4. All mammals are dioecious with
All mammals are heterogametic
which means that the sex of the
offspring is determined by the male.
Most mammalian embryos are
are nourished by a placenta.
5. All mammals breathe with lungs.
6. Have a four-chambered heart and a closed circulatory system.
7. Most are terrestrial but a few are marine and one Order has developed true flight.
8. Mammals have the most
advanced nervous system of any group.
10. All mammals have excellent hearing
and external ears called pinnae.
There are 21 orders of Mammals classified into two subclasses
1. Subclass Prototheria (egg-laying mammals)
ex. Duck-billed Platypus, echidna ( one order)
2. Subclass Theria-( Placental mammals)
a. infraclass Metatheria-marsupials
b. infraclass Eutheria- true placental
mammals ( 19 orders)
A. Most mammals are both
endothermic and homeothermic.
B. Internal body heat results from camel is example of non- homeothermic animal
1. a typical resting mammal has a metabolic rate 10 X higher than a reptile
2. Mammals eat more calories and process them more efficiently than reptiles in order to maintain a higher body heat.
3. the smaller the mammal, the greater its body size to surface ratio and the more it must eat to maintain life
ex. A 3 g. mouse eats 5X more than a 10Kg. Dog and 30X more than a 50,000 Kg. elephant.
*per gram of body weight
II. Sources of heating the body of a mammal
B. brown fat
C. changing the pelage with the seasons
D. Arrectorpilli muscles to erect hairs and trap
E. Insulating blubber accounts for 45% of body weight of seals and whales
III. Sources of cooling the body in mammals.
C. remaining inactive during the hottest part of
D. spreading out and exposing skin where hair is
IV. Additional forms of temperature adaptation
A. hibernation- winter dormancy
B. aestivation-summer dormancy sparse
V. Mammalian integument ( outer covering of skin)
1. Skin Glands produce various pheromones
2. hair is formed of fine scales of the protein keratin.
a. Various types of mammalian hairs include: soft
undercoats, guard hairs, bristles and quills. Hair of
sheep and humans grow continuously, also the
manes and tails of horses, most other mammal hair
growth is determinate.
b. Molts are periodic sheds of hair in most mammals. Fox and
seals shed once a year in summer, most mammals shed twice a
year, in spring and fall. Some mammals change
color with the seasons, the white winter coat
of Artic mammals is called leukenism.
c. Whiskers or Vibrissae are sensory hairs,
they provide a tactile extra sense.
V. Mammalian integument
2. glands- sweat, scent, sebaceous, mammary
a. Eccrine sweat glands secrete a watery fluid that draws heat away
from the body surface…found in hairless regions of the body
b. Apocrine sweat glands are larger and open into a hair follicle. They are unrelated to heat and tied to reproductive cycles. In humans, they develop during puberty and are restricted to armpits, ear canals, and pubic areas.
c. Scent glands used to communicate with members of same
species for breeding, territory marking, and defense
d. Sebaceous glands which serve as a dressing to keep skin
moist, fur glossy or waterproof.
e. Mammary glands occur on all female mammals. Some
mammals develop only during nursing, humans develop at
puberty with additional fat deposits.
Scent glands- marking territory!
3. Horns and antlers
a. true horns-found in ruminants
(sheep and cattle family)
1. hollow sheaths of keratin over bone
2. they embrace a core of bone arising
from the skull
3. they are not normally shed and are not
4. are found on both sexes within a
species but are usually longer in males
b. Antlers-found in the deer family
1. composed of solid bone when mature
2. grow under a covering of vascular skin called velvet.
3. when growth is complete, the blood vessels constrict and the stag removes the velvety by rubbing it against trees.
4. antlers are shed after breeding season
5. each year the antlers are bigger than the year before
6. only Caribou females have antlers
7. in Moose and Elk, males must acquire over 50 lbs. of calcium each year to grow their antlers
1. hair like keratinized filaments are cemented
2. Are not attached to the skull
1. Incisors have sharp edges for biting
2. Canines are specialized for piercing
3. Premolars have compressed crowns for shearing
4. Molars have larger, flatter tops for Grinding
5. Generally, mammals have one deciduous set and
one Permanent set.
1. Insectivores include shrews, moles, and most bats
2. Herbivores include 3 sub-groups
a. Gnawers include rodents, rabbits
b. Browsers and grazers include horses, deer, cattle, sheep-all hoofed animals are called Ungulates, one sub group of ungulates are called ruminants which have a huge 3-4 chambered stomach. The chambers of the stomach are called the rumen, the reticulum, the omasum, and the abomasum
3. Omnivores include raccoons, bears, pigs, rats and most primates
4. Carnivores include members of the dog, cat, and seal family.
(ear flaps) to aid in capturing sound and locating
B. Senses of smell, sight, and hearing are more or less intense in each species.
C. Echolocation is the ability to use sound waves to locate and identify objects.
Two orders, Cetacea and Chiroptera
have this ability, but it is used in very different environments.
and there is a cloaca for fertilization in
the female and the male’s testes are
housed inside the abdominal cavity
B. Marsupials have a primitive
placenta that doesn’t allow
for many nutrients to pass
from mother to offspring, so
the embryo is expelled and crawls
to the marsupium which is a pouch
with a teat inside that the young
animal attaches and completes development.B
housed outside the abdominal
cavity in a sac-like extension
called the scrotum. Most
placental males also have
a scrotum, except for the
aquatic mammals and elephants.
D. Placental mammals carry their
Young in the uterus for the entire fetal period and
The fetus is fed and cared for by the placenta.
E. Mammary glands are made up of clusters of milk-secreting glands. Milk is made up of the sugar lactose. Various proteins, fats, salts, vitamins and antibodies from the mother’s immune system. Immediately after birth, there is a special milk produced called Colostrum which is made up
of large amounts of white cells
and antibodies to protect
the infant from infection
until its own immune
A. Estrus is the condition of a female mammal being receptive to the male during certain intervals in an ovarian hormonal cycle.
ex. Mice and Rats
ex. Buffalo and Deer
Cats-56 days mice-16 days guinea pigs-77 days
Dogs-63 days bats-154 days humans-280 days
Spiny anteaters (echidna)
Spiny anteater or Echidna
1. identified by the presence of a marsupium which acts as a brood pouch
for the developing embryo after it has left the womb.
2. only one marsupial species in North America, the opposum
3. 250 species of Marsupials, found mainly in Australia, and Central and So. America
4. Australia has been marsupial heaven because of its remote locale
a. the dominate herbivore is the Kangaroo
b. the dominate carnivores were the Tasmanian
Wolf and the Tasmanian Tiger and the Tasmanian Devil
c. other Distinctive Australian marsupials include the
Wombat, Bandicoot, Koala, and Wallaby
True placental mammals made up of 18 orders
a. small, terrestrial or semi-aquatic mammals
with long tapered snouts, tiny eyes and short fur.
b. most are carnivorous, feeding on insects and
c. some have poisonous saliva
EX. Hedgehogs, shrews, moles
About 1000 species of bats (second largest order)
a. most new-world bats are insectivores and
most old-world bats are fruit and flower
b. there are also bird,fish, frog and bat eating
bats. Three species of new-world bats are
c. Bats are the only mammals to have evolved true flight.
The fore-limbs are modified with the 2nd to 5th digit
elongated to support thin membraneous wings, thumb
d. Bats are mainly nocturnal in order to avoid direct
competiton with birds for food.
e. Bats that are carnivorous have developed Echolocation to
175 species (including humans)
About 240 species
A. terrestrial carnivores include the dog, cat, weasel, hyenas, racoon, bear, badger, coyotes
B. aquatic carnivores include seals, otters, walrus
C. not all carnivores are truly carnivores, bears and racoons are omnivores and the Panda eats only bamboo.
D. Most other carnivores have a well developed sense of smell, and have limbs adapted for running down prey.
Odd-toed animals (ex. Horses, rhinos, and tapirs)
Even-toed animals (ex. Swine, camel, deer, giraffes, cattle,sheep, and hippos)
Collectively called the Ungulates
“ Eyes on the side, likes to hide
Eyes in the front, likes to hunt!”
“odd-toed” hoofed mammals
“Even-toed” hooved mammals
Order Sirena( ex. Manatees, dugongs)
Order hyracoidea( ex. Hyraxes)
These three orders are referred to as the
Because they have a caecumand some have vestigial hooves
Hyraxes-closest living relative to the elephant
(ex. Anteaters, sloths,armadillos)
(Whales, dolphins and porpoises)
(Ex. Beavers, rats and mice, squirrels)
bottom of the food chain!
ex. Jackrabbits, snowshoe hares
ex. Cottontails-easter bunnies