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34 Cards in this Set

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  • Back
The line that leads to Mammals
-split off from reptiles more than 300 million years ago.

-The earliest fossils that are definitely mammals are 170 million years old.
Some scientist say the earliest
-mammals existed 220 million years ago.

-Others say this type of mammal was really just a protomammal and that true mammals existed 170 million years ago.
The time when the first mammal existed is
-disputed because there is no evidence of hair or mammary glands on fossils.
The first mammals were
-small and shrew like. The demise of the dinosaurs provided an opportunity for mammals to quickly diversify as new lifestyles and opportunities became available.
The number of mammals alive today
All mammals have two main
-characteristics: hair and mammary glands.
Whales and Armadillos have
A thick coat of hair
-called fur or pelage, is used as insulation and can be used as camoflauge.
Mammals use the patterns of their fur
-to recognize members of their species.

-certain patterns may also allow mammals to recognize specific individuals (Zebra Stripes.
Mammary Glands
-produce milk

-the mammery glands are derived from a skin gland found in mammals called the sweat gland.
The mammalian skin has two types of glands
-the sweat gland and sebacious (oil) gland associated with the hair.
Other mammalian characteristics include
-a muscular diaphram below the rib cage that assists in breathing

-and specialized teeth
Fossil Mammals are
-seperated from other mammals by studying bones, especially teeth and skull structure.

-this is because hair and mammary glands are usually lost in the fossil record, but bone structures remain as fossils.
Bony Structures
-include three tiny middle ear bones, a lower jaw made from one bone, and a special type of joint that connects the lower jaw of a mammal to its upper jaw.
Mammals are divided into three types based on their
-method of reproduction: egg laying monotremes, marsupials with pouches, and placental mammals
-are mammals which lay shelled eggs

-Monotremes have hair and mammary glands, though their mammary glands lack well developed nipples.

-so,offspring of Monotremes lap milk off of mother's fur as it oozes from mammary glands.
-are pouched mammals.

-marsupials evolved about 100 years ago, probably somewhere in North or South America.
Most Modern Marsupials
-live in Australia, though there are some isolated clusters in South America, and the North American Opossom.

-other than the Red Kangaroo, and Virginia Opossom, Marsupials don't compete well with Placental mammals.
Placental Mammals
-are characterized by the prescence of a placenta, a vascular organ that connects the developing fetus with the female uterus.
Placental Mammals
-are much more developed at birth.

-evolved around the same time as marsupials.

17 of 19 modern mammals are placental mammals
Tree shrews are placed in the group

-Tree Shrews resemble the first mammals that evolved 80 million years ago.

-Tree shrews are small mammals that have big eyes, live in trees, and catch insects.
Insectivores are
-small mammals with pointy teeth.

-their diet consists mainly of insects.

-Insectivores include moles, shrews, and hedgehogs.
Anteaters are also called
Endentates include
-anteaters and armadillos

-many Endentates lack teeth; others have a few remnant peglike teeth.

-Edentates are adapted to eat mostly ants and termites.
All bats are grouped together as

-Chiropterans are flying mammals that have evolved wings.
-include whales, dolphins, and porpoises
Cetacans are adapted to
-a marine lifestyle, which is reflected in their streamlined bodies.

-Cetacans front limbs have evolved into fins, and their back legs are gone completely.
Toothed Whales
-are whales that have teeth and actively pursue prey.

-Toothed whales include the orca and killer whale
Baleen Whales
-have sheets of whale bone, known as baleen, that hang down from their upper jaw.
The baleen acts
-as a strainer to seperate small fishes or crustaceans (krill) from the water.

-the tongue then licks the food off the baleen and the whale swallows the food.

-Baleen whales include the blue whale, humpback whale, and right whale
Cetacans are most closely related to

-artiodactyls include pigs and hippos.
Fossils of whales with
-legs have been found

-recent fossil evidence shows that whales with legs had artiodactyl ankles.

-artiodactyl ankles are unique among mammals.
-rabbits, hares, and pikas
-mice, praire dogs, capybaras, beavers, porcupines, rats, and squirrels