MammalsChapter 43

References: Holt biology text & materialshttp://www.ucmp.berkeley.edu/mammal/mammal.html

Placental mammals4000 described species, mostly rodents and bats

Marsupial mammals

Monotreme species: Only 5 living: duck-billed platypus & 4 species of echidna (spiny anteaters).

Objectives for chapter 43

• Describe the major characteristics of mammals.

• Compare the characteristics of early synapsids, early therapsids, and modern mammals.

• Explain the advantage of endothermy in mammals.

• Differentiate among the patterns of development in monotremes, marsupials, and placental mammals.

• Recognize the various orders of mammals.

All mammals have the following six major characteristics:

1. Endothermy

2. Hair

3. Completely divided heart

4. Milk/ mammary glands.

5. Single jawbone

6. Specialized teeth

– Mammalian characteristics

1. Endothermy

• All Mammals are endotherms which means they conserve and regulate body heat.

• allows mammals to remain active in cold climates.

• enables strenuous activities for extended periods.

• Requires eating LOTS of food compared to cold blooded animals.

– Mammalian characteristics

2. Hair

• All mammals have hair- even aquatic ones.• Insulates against heat loss• Made of keratin protein filaments

• 4 chambers (2 atria, 2 ventricles)• Efficient oxygen exchange- no deoxygenated

blood pumped back into body

3. Completely Divided Heart

– Mammalian characteristics

Mammalian characteristics

4. Milk/ mammary glands.-All mammals produce milk, High in protein & sugar-only Monotremes do not have mammary glands but

secrete milk like sweat.

5. Single jawbone.-lower jaw is 1 solid bone (reptiles have several bones)

6. Specialized teeth-teeth modified for different functions

History of Mammals- Synapsids & Therapsids

Synapsids – were animals that were small and looked like modern lizards.

Unlike most other reptiles, which have uniformly shaped teeth, these early

synapsids had specialized teeth.

Therapsids• A subset of synapsids, called therapsids, gave rise to

mammals.• Therapsids appeared late in the Permian period and lived

into the Jurassic period.

– History of Mammals-

History of Mammals

• Mammals and dinosaurs – appeared during the Triassic period – coexisted for more than 150 million years.

• Early mammals – about the size of mice – probably insectivores – active at night.

Phylogenetic Diagram of Vertebrates

– History of Mammals-

Mammals have highly developed & efficient body systems:

• Circulatory System

• Respiratory System

• Digestive System– note specialized teeth– Special Adaptations for Digesting Plants

• Nervous System

• Reproduction

Circulatory System

• 4 chambered heart

• 2 atria, 2 ventricles– A septum completely

separating the ventricles. – The complete septum is an

adaptation that allows mammals’ bodies to use

oxygen more efficiently.

Respiratory System- efficient gas

exchange.

–larger surface area available for gas exchange

–At rest, mammals breathe mostly with their diaphragm.

Digestive System

• TEETHTEETH: - : - size and shape of teeth reflect differences in diet in various species.– Incisors -Chisel-like cut.

– Canines Pointed grip, puncture, and tear.

– Premolars shear, shred, cut, or grind.

– Molars grind, crush, or cut.

• Carnivores have sharp incisors & long canines.

• Baleen whales have baleen instead of teeth.

Types of mammalian teeth:

Special Adaptations for Digesting Plants

• Herbivores have long digestive tracts • special organs w/ symbiotic

microorganisms, which can break down cellulose. – Some have a rumen and are called

ruminants.

– Others have a cecum.

Nervous System• Big Brains:

– A mammals brain is at least 15X heavier than a similarly sized fish, amphibian or reptile.

– Humans, other primates, and whales have the biggest brains

– due mostly to the size of the cerebrum which is folded for max surface area.

– The cerebrum evaluates input from the sense organs, controls movement, initiates and regulates behavior, and functions in memory and learning.

• Senses:– Major senses include vision, hearing, smell, touch &

taste.– Some animals are more developed in some senses:

exampleMost bats, which are active at night, use echolocation to locate prey and other objects.

There are 3 different kinds of mammals based on how they give birth:

1.Monotremes are oviparous, they lay eggs.

2. Marsupials are viviparous, they give birth to

live young that further develop within a pouch on the mother’s body.

3. Placental mammals also viviparous, but the fetus typically develops within the mother’s reproductive system for a longer time & receives

nourishment through blood-rich structure- the placenta.

Mammalian orders:• Mammals are commonly classified into:

–a single (1) order of Monotremes

–7 orders of Marsupials

–about 18 orders of Placental mammals

Phylogenetic Diagram of Mammals

Monotremes• Lay & incubate large eggs

• Mom protects & feeds newborns until able to survive on their own.

• The order Monotremata, (monotremes) is the only order in the subclass Prototheria.

• Just 3 species exist today:– The duckbill platypus is adapted to life around

rivers or streams in Australia.– Two echidna species live in dry woodlands or

deserts in Australia and New Guinea.

Marsupials• Embryo develops in the uterus, but when born,

crawls into the mother’s pouch, attaches to a nipple to feed; develops in the pouch for several months.

• Previously 1 order, but are now divided into at least 7 orders in the super order Marsupialia.

• Most of 280 species live in Australia, • Virginia opossum is only marsupial native to USA

• Theory: marsupials began to evolve in isolation when Australia drifted away from the other continents more than 40 million years ago.

Placental Mammals

• Placental mammals give birth to well-developed young after a long period of development inside the uterus.

• During this period, the placenta provides nourishment and oxygen to developing offspring

Your assignment:Read pages 868 to 874 in the textbook.Write down the following orders & give the main characteristics of each Plus at least

2 example organisms:• Monotremes• Superorder marsupialia• Placental mammals in super order Eutheria

– Xenarthra– Lagomorpha– Rodentia– Primate– Chiroptera– Insectivora– Carnivora– Artiodactyla– Perissodactyla– Cetacea– Sirenia– Probscidea– Also the 5 orders in the table 43-1

Then- Answer questions 1-5 on page 874

18 orders of Placental Mammals

Order Xenarthra• The order Xenarthra includes about 30

living species of anteaters, armadillos, and sloths living in the Americas.

Order Lagomorpha • The order Lagomorpha, the lagomorphs,

includes about 70 species of rabbits, hares, and pikas.

18 orders of Placental Mammals

Order Rodentia • The order Rodentia, the rodents, is the largest mammalian

order, which includes more than 1,800 species. • Rodents are adapted to a wide range of habitats

worldwide. • Squirrels, marmots, porcupines, chipmunks, gophers,

muskrats, mice, and rats are rodents.

Order Primates• The order Primates is made up of 235 living species,

including lemurs, tarsiers, lorises, monkeys, gibbons, apes, and humans.

• They live in a variety of terrains; most are omnivores with complex behaviors.

18 orders of Placental Mammals

Order Chiroptera• Chiroptera, the bats, are the only mammals that

truly fly.• More than 900 species live throughout the

world, except in polar environments.

Order Insectivora• The order Insectivora includes about 390

species of shrews, hedgehogs, and moles.• Most members of this order are insectivores, but

not all insectivores are members of the order Insectivora.

18 orders of Placental Mammals

Order Carnivora• The 274 living species of the order Carnivora are

distributed worldwide.• Dogs, cats, raccoons, bears, hyenas, otters,

seals, and sea lions are some well-known carnivores.

• Most members of this order eat meat. Most are skilled hunters.

• Aquatic carnivores, known as pinnipeds, include the sea lions, seals, and walruses.

Hoofed Mammals• Hoofed mammals are ungulates. • Most are herbivores that run quickly.• The two main groups of ungulates are characterized by their foot

structure and by the presence of either a rumen or a cecum.

Order Artiodactyla• Ungulates with an even number of toes are artiodactyls, in the order

Artiodactyla.• Most artiodactyls are ruminants, or animals that have a rumen. • This order includes about 210 species of deer, cattle, giraffes, pigs, and

camels.

Order Perissodactyla• Ungulates with an odd number of toes are perissodactyls, in the order

Perissodactyla.• Perissodactyls have a cecum. • This order includes about 17 living species, such as horses, zebras,

rhinoceroses, and tapirs.

Some Aquatic Mammals

Order Cetacea• Closely related to Artiodactyla is the order Cetacea, the cetaceans.• Cetaceans include about 90 species of whales, dolphins, and

porpoises worldwide.• Cetaceans are totally aquatic but evolved from land-dwelling

mammals.

Order Sirenia• Four species of manatees and dugongs make up the order Sirenia,

the sirenians.• These herbivores live in tropical seas, estuaries, and rivers.• The similarities between whales and sirenians came about through

convergent evolution.

Order Probscidea

• Members of the order Proboscidea have a nose that is modified into a long, boneless trunk, or proboscis.

• The only living species of this order are the Asian elephant and the African elephant, which is the largest living land mammal.

• Mammoths and mastodons are extinct members of this order.

• Elephants have long gestation periods, and can live to be 80 years old.

– More mammals

And other orders making up less than 1% of mammals