Mammals! Ch 32 Turboblastin’

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

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

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

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

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)

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

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

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)

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)