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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
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