Overview of Mammals: Evolution, Physiology, and Characteristics

1. Hannah Reagan 3rd period Chapter 32.1 Notes

2. Mammals • Class Mammalia • Have hair and mammary glands (produce milk to nourish the young) • Also, mammals breathe air, have four-chambered hearts, and are endotherms that generate body heat internally

3. Evolution • Though you can’t see hair nor mammary glands in fossils, some fossilized mammal characteristics include: lower jaw connected by a joint directly to the skull, teeth that are replaced once in a lifetime, and discrete features of limbs and backbone • Mammals descend from reptiles • First appeared during late Triassic period; 220 million years ago

4. Body Temperature Control • High metabolic rate • Hair • Subcutaneous fat: layer of fat located beneath the skin • Some have sweat glands and others often pant

5. Feeding • As mammals evolved, the form and function of their jaws and teeth became adapted to eat foods other than insects • Because of high metabolic rate, mammals have to eat 10 times more food as a reptile • Specialized teeth: 1. incisors 2. canines 3. molars 4. premolars • Carnivores have short intestine because digestive enzymes can quickly digest meat • Herbivores have long intestine because tough, fibrous plant tissue is hard to break down • Rumen: stomach chamber in which newly swallowed plant food is stored and processed

7. RespirationCirculation • All mammals use lungs • Diaphragm: powerful muscle that pulls the bottom of the chest cavity downward, which further increases volume when breathing in • 2 separate loops with a four chambered heart • Right ventricle and atrium pump oxygen poor blood from body to lungs. Left ventricle and atrium pump oxygen rich blood from lungs to the rest of the body.

9. Excretion • The kidneys of mammals help maintain homeostasis by filtering urea from the blood, as well as by excreting excess water or retaining needed water. • Kidneys also help retain sugars, salts, etc. • Kidneys allow mammals to live in different habitats just by being able to stabilize the amount of water in the body efficiently

10. Response • Highly developed brains: main parts include cerebrum-thinking and learning, cerebellum-muscular coordination, and medulla oblongata-involuntary body functions • The cerebrum outer layer is the cerebral cortex: center of thinking and other complex behaviors • Many have well developed sense of smell, sight, and hearing

11. Other super cool fun stuff • Endocrine glands regulate body activities by releasing chemicals called hormones that affect other organs and tissues • Immune systems help stop pathogens from infecting the mammal (includes skin barrier, and specialized cells that recognize and destroy pathogens)

12. Movement • Backbone • Shoulder and pelvic girdles • Diversity in limb bones of climbers, runners, diggers, flyers, and swimmers. Pictures of limbs on page 826!

13. Reproduction • Internal fertilization • All newborn mammals feed on their mother’s milk • Strong parental care and interaction

14. 1. What is the cerebral cortex? • Covering of the olfactory bulb • Outer layer of the cerebrum • Helps in excretion • Another name for the medulla oblongata

15. 2. What defines a mammal? • Four chambered heart • Breathe air • Generate their body heat internally • All of the above

16. 3. When and about how long ago did the first mammal appear? • Triassic Period; 220 million years ago • Jurassic Period; 206 million years ago • Permian Period; 260 million years ago • Carboniferous Period; 330 million years ago

17. 4.What system is the kidney a part of? • Nervous • Digestive • Excretory • Circulatory

18. 5. How do mammals reproduce? • Asexual reproduction • External fertilization • Internal fertilization • They don’t reproduce

19.  CORRECT!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

20.  WRONG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!