Chapter 43 Mammals

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Chapter 43Mammals

• Section 1
• Origin and Evolution of Mammals

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Characteristics

• Endothermy- regulate own body temperature-
  metabolism
• Hair- all mammals have some hair- made of keratin
• Completely divided heart- four-chambered heart-
  no mixing of blood

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Characteristics

• Milk- females produce milk to feed offspring-
  made of fats, proteins, and sugars
• Produced by mammary glands- modified sweat glands
  located on thorax or abdomen
• Single jawbone- fossils identified by bones
• Specialized teeth- for eating

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Ancestors of Mammals

• Synapsids- gave rise to mammals
• Single opening in a bone behind eye socket
• Looked like modern lizards
• Specialized teeth

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Therapsid

• Also gave rise to mammals
• Rich fossil record of transitional forms between
  therapsids and mammals exists

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Early Mammals

• Dinosaurs co-existed with mammals
• Early mammals were about the size of a mouse
• Large eye sockets suggests that early mammals
  were active at night

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Diversification of Mammals

• Monotremes- oviparous- lay eggs
• Marsupials- viviparous- give birth to live young-
  young develop in pouch
• Placental mammals- viviparous- develop in
  mothers uterus- nutrition from placenta

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Monotremes
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Marsupials
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Placental Mammals
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REVIEW!!!

• What is the function of hair in mammals?
• Differentiate between monotremes, marsupials, and
  placental mammals.