Mammals!

1. Mammals! Ch 32 Turboblastin’

2. What is a mammal? • All mammals are endothermic (maintain a constant body temp) • Can live in almost every possible environment on Earth • Four-chambered heart • Hair covering much/all of body • Produces milk to nurse young • Diaphragms (expand/contract to bring air into lungs) • Specialized teeth • Modified limbs • Highly developed brains

3. All that hair… • Maintaining constant body heat takes energy • Having bodies covered in hair minimizes that expense, retain that heat • If body becomes too warm, internal feedback mechanisms help mammals cool off • (panting, sweating, wet noses/mouths) • Sweat glands help regulate body temp by secreting moisture, which evaporates & transfers heat to the surrounding air • Hair – modified into different lengths/textures • Provide camouflage, signaling, protection

4. Mammals nurse their young • Mammals (Gr: mamma = “breast”) secrete milk from glands (a group of cells that secrete fluids) • Also have glands that produce oil, saliva, digestive enzymes, hormones, scent, milk, etc. • Mammary glands (possibly modified sweat glands) secrete liquid rich in fats, proteins, sugars, minerals & vitamins • Mothers nurse young until babies can digest & absorb nutrients from solid foods • Nursing time varies among species

5. Respiration & Circulation • Mammals need a high level of energy to maintain their endothermic metabolism • Diaphragm involuntarily controls lung expansion in chest cavity • 4-chambered heart • Remove metabolic wastes with kidneys efficiently

6. Specialized teeth • Mammals have teeth with different functions • Adapted to the types/variety of foods they eat • (like having multiple tools in a toolbox for different tasks) • Incisors – grasping, chiseling • Canines – puncturing, tearing • Premolars & molars – slicing, shearing, crushing, grinding Teeth are first step in mechanical digestion (breaking down food into smaller parts for chemical digestion)

7. Modified limbs • Limbs adapted for variety of food gathering, protection, & locomotion functions

8. Mammals can LEARN • Fiercely guard young, teach them survival skills • One reason mammals are very successful • Primates & cetaceans among the most intelligent animals • Use tools, communicate culture to offspring, communication • Complex nervous systems, highly developed brains, varied & specialized sensory organs to learn about/interact with surrounding environment

9. Mammal Diversity • Monotremes – egg-laying mammals (platypus, echidna) have cloaca & milk-secreting pores • Marsupials – pouched mammals, young develop somewhat in mother’s body, then complete development/nurse in pouch of skin • Placental mammals – give birth to young that have developed inside uterus • Nourishment from placenta • This development time is called gestation • Most successful group of mammals (90% of all mammals)

10. Origins • Placental mammals appeared in fossil record 125 mya • Mammalian characteristics shared by reptilian ancestors called therapsids • Mass extinction of the dinosaurs along w/ breaking apart of Pangaea and changes in climate led to new niches for mammals to fill • Dramatically increased in # and diversity during the Cenozoic Era (present era)