18B- Class Mammalia

Class Mammalia The class mammalia is one of the smallest vertebrate classes, but it encompasses animals of great variety that inhabit virtually every habitat imaginable.

Common Characteristics Air breathing Endothermic 4 chambered heart Specialized teeth Produce milk for young Hair 3 middle ear bones

Reproduction Monotremes: egg-laying mammals Have a single perforation or hole for the digestive, excretory and reproductive systems (like cloaca). They are the only egg-laying mammals. They lay and incubate eggs like a bird, but when hatched, the young nurse on milk that empties onto the skin. Duck-billed platypus—one of the few known venomous mammals. Males hind legs have sharp spurs that can inject poison. 2 species of echidnas or spiny anteaters. They have a small pouch where the egg hatches and nurses

Reproduction Marsupials: pouched mammals Kangaroos, koalas, wallaby, wombat, sugar glider, Tasmanian devil… No placenta, no shelled egg Babies are very altricial (Red Kangaroo, largest living marsupial, 33 day gestation, 7 months in pouch) Young nourished by a small yolk sac; when depleted the immature offspring crawls out of the uterus and onto the mother’s fur, instinctually moves towards the mother’s marsupium (pouch) where it is sustained by the mother’s milk while it completes its development.

Reproduction Placentals Most mammals have young that develop internally; nurtured by a placenta—the interface between mother and the developing offspring through which gases, nutrients, and wastes are exchanged. Blood supplies do not mix. Umbilical cord- blood vessels and surrounding membranes that connect the placenta and the embryo Uterus- muscular chamber where the young develops Estrus- period where ovum (egg) is ready to be fertilized. Female releases chemical odors to attract males Internal fertilization- fertilization is a uniting of the male gamete (sperm) and the female gamete (egg). This produces a zygote. Zygote begins to divide and is implanted into the uterine wall Placenta forms which is composed of a portion of the uterine wall and tissues of the embryo Gestation = period of pregnancy, the embryo develops

Reproduction Mammary glands- produce milk rich in nutrients and antibodies

Hair All mammals have hair which is a collection of nonliving cells filled with filaments of the protein keratin Produced by hair follicles Two types Underhair- soft, insulating fur layer next to the animal’s skin Guard hair- coarser, longer, found over the underhair, gives animal color Functions Insulating ability Camouflage Sensory (whiskers are innervated, enlarged hairs) Repelling attackers (porcupine)

Limbs Very diverse Forelimbs of the bat have elongated webbed fingers used as wings Moles have short stout limbs with wide paws and large claws that they use as a shovel Whale has forelimbs fused into swimming paddles Primates have opposable thumbs for climbing and grasping items Ungulates have hooves to protect phalanges Lions have needle-sharp retractable claws used for tearing into prey

Digestion Most mammals have a variety of specialized teeth arranged in jaws Types of teeth usually match a particular diet Incisors- flat, thin teeth in the front of the mouth, used in gnawing or biting Canines- rounded, pointed teeth toward the front of the mouth, used for tearing Molars- thick, squat teeth in the back of the mouth, used for grinding and chewing

Digestion Carnivores have enlarged canine teeth Gnawing animals, like rats and beavers, have large incisors and no canines Herbivores have sharp incisors and flat molars to cut and grind foliage Omnivores have well-formed teeth of each kind

Digestion Digestive organs vary in mammals with different diets; however, no vertebrate can digest cellulose without help

Complex Carbohydrates Cellulose- plants, structural Starch- plants, storage Chitin- arthropods, fungi, structural Glycogen- animals, storage

Starch OH O CH2OH CH2

Chitin

Glycogen

Digestion Rumen- (cows, camels, giraffes, deer are ruminants) a special section of the multi-chambered stomach of certain mammals. Bacteria maintained within the rumen produce enzymes that digest cellulose. Cud— partially digested food that ruminants regurgitate and re-chew for improved digestion. Mixes enzymes with food Ruminants and other herbivores have long digestive tracts which allows for more digestion and absorption

Order Artiodactyls Suborder Suiformes Family Suidae - swine (pigs, hogs) Family Tayassuidae - peccaries (javelina) Family Hippopotamidae - hippopotamus, pygmy hippopotamus Suborder Tylopoda Family Camelidae - camels, llamas, alpacas Suborder Ruminantia (ruminants - having a 3- or 4-part stomach) Family Tragulidae - chevrotains (mouse deer) Family Giraffidae - giraffe, okapi Family Cervidae - deer, including musk deer, moose, muntjacs, brockets, roe deer, pudu, caribou, elk, etc. Family Antilocapridae - pronghorn Family Bovidae - antelope, cattle, goats, sheep

Digestion Cecum—a pouch-like extension between the large intestine and the small intestine containing bacteria for digestion of cellulose for some mammals that don’t chew their cud. (horses, elephants, manatees)

Digestion Carnivores (seals, wolves) eat primarily protein which is easier to digest; therefore, they have a shorter digestive tract & don’t require specialized stomach or digestive bacteria. Unsegmented stomach similar to humans.

Respiration and Circulation Oblong spongy lungs in upper chest cavity Lungs separated from abdominal organs by muscular diaphragm- air is drawn into lungs by the contraction of the dome-shaped diaphragm Larynx- voice box, cartilaginous organ containing vocal cords which vibrate to produce sound. 4 chambered heart Contraction flattens the diaphragm Diaphragm is up when it relaxes Elastin proteins around the alveoli are like rubberbands, drives the exhaling process, elastic potential energy

Diaphragm contracts and flattens Intercostal muscles contract Ideal Gas Law PV=nRT P is pressure V is volume N is the number of moles R is the universal gas constant T is temperature (K) Atmospheric pressure = 760 mmHg Inhaling Diaphragm contracts and flattens Intercostal muscles contract Volume of lungs goes up Pressure goes down. At this point pressure in lungs is less than atmospheric pressure, so air moves in to equalize the pressure Exhaling Diaphragm relaxes into arched orientation Stretchy protein called elastin which surrounds alveoli recoils Volume of lungs goes down Pressure goes up. At this point pressure in lungs is more than atmospheric pressure, so air moves out Atmospheric pressure 760mmHg Volume and pressure Train car http://www.youtube.com/watch?v=Zz95_VvTxZM Barrel http://www.youtube.com/watch?v=n-3cu_Q119s

Nervous System Olfac Cerebrum- controls voluntary muscle activity Optic Lobes Cerebellum- coordinates muscle activity and some involuntary activities Medulla Oblongata

Nervous System Nervous system contains: Brain Spinal cord Cranial nerves (branch from the brain) Spinal nerves (branch from the spinal cord) Sensory organs( eyes, ears, taste buds) Divisions of the Five major lobes of the brain, from anterior to posterior: Olfactory lobes ~ receive impulses from the smell receptors of the nostrils Cerebrum ~ controls voluntary muscle activity Optic lobes ~ Receives impulses from the eyes Cerebellum ~ coordinates muscle activity and some involuntary activities Medulla oblongata ~ transports impulses to and from the spinal cord, including some reflexes. Nervous System

Nervous System Mammalian brains are relatively very large. 2X as large as bird of the same size. 10X as large as a reptile of the same size. Cerebrum = brain Cerebral cortex is the outermost layered structure of the brain important for receiving and processing information. It has many more layers in mammals (6 layers) than other vertebrates (neocortex or isocortex). Telencephalon = cerebrum or brain