Characteristics of Mammals

Major Characteristics Endotherms: ability to maintain a fairly constant body temp. –Enables them to live in almost every place on Earth Hair: made of keratin like feathers & scales –Insulation & waterproofing

Major Characteristics Nurse their young –Gland = organ that secretes substances inside or outside the body –Mammary glands = secretes milk a liquid rich in fats, sugars, proteins, minerals, and vitamins. Respiration & Circulation: –Diaphragm: sheet of muscle located beneath lungs; aids in breathing –4-chambered heart –Lungs

Mammal teeth Mammals teeth are differentiate for the type of food they eat Types: –Incisors: chisel-like modified for gnawing –Canines: puncture & tear flesh –Premolars & molars: used for slicing or shearing, crushing, and grinding Cud-chewing enables them to break down cellulose of plant cell walls into nutrients that they can use and absorb

Mammals can learn Primates are perhaps the most intelligent animals. –The result of complex nervous system and highly developed brains –Outer layer of brain is folded forming ridges (gyrus) and grooves (sulcus) these increase surface area for brain’s activity

Diversity of Mammals Placental Mammals: –Uterus: hollow, muscular organ in which offspring develop –Nourishment of young inside the uterus occurs through an organ called placenta; which develops during pregnancy –Gestation: time during which embryo develops inside uterus

Diversity of Mammals Marsupial: mammal in which young have a short period of development within mother’s body, followed by second period of development inside a pouch made of skin & hair found on the outside of the mother’s body Monotremes: mammal that reporduces by laying eggs –Platypus and anteater

Mammalian Orders Order Rodentia: –largest mammalian order –Rodents are found everywhere in the world besides Antarctica –Includes: squirrels, chipmunks, gophers, mice, rats, & porcupines –Have 2 pairs of incisors that continuously grow as the rodent lives so it must continuously gnaw on something.

Order Edentata Includes: anteaters, armadillos, & sloths Name of the order means “toothless” but only anteaters are completely toothless

Order Lagomorpha Includes: rabbits, hares, and pikas These animals are found worldwide Differ from rodents in that have double row of upper incisors, with 2 large front teeth backed by smaller ones. Herbivores

Order Insectivora Includes: shrews, moles, hedgehogs. Found in North America, Africa, Europe, & Asia Most have long pointed noses that enable them to probe in the soil for insects, worms, & other inverbebrates Have stout limbs for digging, small eyes, and no external ears

Order Primates Include: lemurs, tarsiers, and anthropoids (humans, monkeys, and apes) Most primates are omnivores and have teeth suited for varied diet Larger brains, two-forward facing eyes w/ depth perception, grasping hands, some have grasping tails Live in a variety of environments

Order Chiroptera Include: bats and the only mammals to fly Modified front limbs w/ skin stretched between extremely long finger bones to hind limb. Use echolocation for navigation and most have small eyes and large ears

Order Carnivora 274 species including: dogs, cats, raccoons, bears, hyenas, otters, seals, and sea lions Generally have long canine teeth, strong jaws, & clawed toes Subphylum Pinnipedia: aquatic carnivores such as sea lions, seals, and walruses, have streamline bodies for efficient swimming

Order Artiodactyla Ungulates = mammals w/ hooves; those with even numbers of toes make up the order Artiodactyla Include: deer, elk, bison, moose, cows, sheep, goats, pigs, and camels They are fast runners and use speed as a major defense Usually herbivores their molars tend to be large and flat, for grinding materials Have a chamber in stomach called rumen in which bacteria and microorganisms break down cellulose

Order Perissodactyla Ungulates with odd number of toes make up order Perissodactyla Includes: horses, zebras, rhinoceroses, and tapirs Also have an adaptation to break down cellulose but instead of a rumen they have a cecum with microorganisms the break down cellulose releasing nutrients for the perissodactyl to absorb

Order Cetacea 90 species of whales, dolphins, & porpoises Have modified forelimbs = flippers Breathe through blowholes located on the top of the head Completely hairless except a few bristles on the snout Thick blubber for insulation Use echolocation for navigation and communication Two groups of whales: toothed and baleen (filter feeders) whales

Order Sirenia 4 species: manatees and dugongs Inhabit tropical seas, estuaries, & rivers Modified forelimbs for swimming - flippers Lack hindlimbs but have a flattened tail for propulsion Look like whales but are more closely related to elephants

Order Proboscidea Characterized by boneless, trunked nose, or proboscis Includes: Asian and African Elephant Modified incisors called tusks for digging up roots and stripping bark from branches Large jagged molars for grinding up plant material Elephants have the longest gestation period of all animals (can take up to 22 months)