Mammals Chapter 43 The best mammals Origin Evolution

Mammals Chapter 43

The best mammals!

Origin & Evolution of Mammals Section 43. 1

Key Characteristics: 1. Endothermy 2. Hair 3. Completely divided heart – 4 chambers 4. Milk – mammary glands 5. Single jawbone 6. Specialized teeth

Ancestors of Mammals 300 million years ago Mammals are the only surviving synapsids Distinquished by structure of the skull First resembled modern lizard Evolved into therapsids which evolved into early mammals Origin of specialized teeth, endothermy, & hair

Early Mammals Size of mice Arose around the time of the dinosaurs Not much diversity or abundance due to reign of the dinosaurs Nocturnal

Diversification of Mammals Once dinosaurs went extinct mammals took over as reigning animal group Three main types: 1. Monotremes: oviparous (lay eggs) 2. Marsupials: viviparous (live undeveloped young) 3. Placental mammals: viviparous (live developed young)

Characteristics of Mammals Section 43. 2

Endothermy Generate heat internally by breaking down food Sustain activity for extended periods of time Hair & fat help keep heat within the body blubber

Circulatory System 4 chambered heart: 2 atria 2 ventricles Septum separates right from left sides Oxygenated & deoxygenated blood never mix More efficient system

Respiratory System Adapted for efficient gas exchange Lungs have millions of alveoli Diaphragm: sheet of muscle below rib cage that helps draw air into the lungs

Feeding & Digestion Types of teeth: Incisors: Canines: Premolars: Molars: Baleen: Adaptations for digesting plants: Rumen: Cecum:

Nervous System Enlarged brain (15 X) mostly in cerebrum Thinking & processing center 5 major senses: smell, touch, sight, taste, & hearing Some use echolocation to navigate High-frequency sound waves bounce off objects

Development video Monotremes: Lays 1 to 2 leathery shelled eggs Undeveloped young hatches, feeds of mother’s milk to fully develop Marsupials: Inside mother’s womb short period of time Newborn crawls into pouch and attaches to nipple to continue growth

Placental mammals: Nutrients and oxygen to fetus via placenta Newborns are nourished via mom’s milk Dependent upon parent for food and care

Mammalian Classification Section 43. 3

Mammalian Orders Monotremes: 1 order Marsupials: 7 orders Placental: 18 orders

Order Monotremata Examples: platypus, spiny anteater Only egg laying mammals Oldest order of mammals Only live in Australia & New Guinea

Super Order Marsupialia Examples: Kangaroo, opossum 280 different species in Australia Only one in the US- Virginia opossum Many species became extinct Herbivores

Placental Mammals 12 Orders will be in these notes!

Order Xenarthra Examples: anteater, armadillo, & sloth No prominent teeth Some with a long sticky tongues to catch prey

Order Lagomorpha Examples: rabbits, hares, & pikas Double row of incisor teeth Two large front teeth, two small back teeth Continuously growing Herbivores

Order Rodentia Examples: squirrels, chipmunks, gophers, mice, & rats Largest mammalian order Sharp incisors to gnaw seeds, twigs, roots & bark Continuously growing

Order Primates Examples: lemurs, monkeys, gibbons, apes, & humans Most are omnivores Brain with large cortex allowing complex behaviors Forward facing eyes allowing depth perception Grasping hands and feet

I picked a good one!

Order Chiroptera Examples: bats Only truly flying mammals Wing = modified forelimb with membrane of skin that stretches between long finger bones Small eyes Large ears for echolocation Most are nocturnal

Order Insectivora Examples: shrews, hedgehogs, & moles Meaning “animals that eat insects” Small with high metabolic rate Long, pointed noses to probe for prey Sharp teeth Video

Order Carnivora Examples: dogs, cats, raccoons, & bears Meaning “ animals that eat meat” Strong jaw, canine teeth, claws, and sense of smell Pinnipeds: aquatic carnivores Sea lions, seals, & walruses

Order Artiodactyla Examples: deer, cattle, giraffe, & pigs Ungulates: mammals with hoofs Even number of toes Most are herbivores Large flat molars to grind plants Have rumen

Order Perissodactyla Examples: horses, zebras, rhinos, & tapirs Ungulates with odd number of toes Herbivores with a cecum

Order Cetacea Examples: whales, dolphins, and porpoises Fish-shaped bodies with flippers Breathe through modified nostrils blowholes Use echolocation Little hair except around snout Keep warm with blubber

Order Sirenia Examples: manatees & dugongs Large, torpedo-shaped herbivores Live in tropical seas, estuaries, & rivers Closely related to elephants

Order Proboscidea Examples: elephants Proboscis: long, boneless trunk Largest living land mammals Tusks: modified incisors Long gestational period (20 -22 months) Can have children up to 70 years of age!

Primates & Human Origins Section 43. 4

Primate Characteristics: Prehensile appendages Large cerebrum Acute color vision Generalist teeth Communication Infant care Social organization

Anthropoids Primate group that includes old & new world monkeys, apes, and humans Adaptations: Opposable thumb & toe (nonhuman) Rotating shoulder & elbow joints Great apes: Orangutans, chimpanzees, bonobos, & humans

Modern Humans Only species to have bipedalism Tendency to walk upright on two legs Adaptations for walking: Bowl-shaped pelvis S-shaped spine Shape of foot

Hominids Include humans and extinct humanlike anthropoid species All hominids were bipedial All other anthropoids are quadrupedal (walking on four limbs) Becoming Human Video

Fossil Hominids Humanlike species less than 10 myo Much debate still between paleontologists & anthropologists

Hominid Species Human evolution was NOT through a single pathway! Earliest hominids (7 -4. 5 mya) Slender australopithecines (4. 5 -2 mya) Large-bodied australopithecines (2. 5 -1 mya) Early humans (2. 5 -0. 5 mya) Recent humans (0. 5 -today)

Homo habilis “handy human” Fossils age between 1. 6 to 2. 5 million Used tools Larger brain capacity Short Stayed in Africa

Homo erectus “upright human” Larger brain capacity (2/3 of modern human) Thicker skull, large brow ridges, larger teeth Cooked food Traveled out of Africa

Homo neanderthalensis Lived in Europe & Asia 230, 000 years ago Lived in caves Stone tools Heavy bones, protruding jaw, same size brain as modern human May have interacted with Homo sapiens in some places

Homo sapiens Fossils found all over the world 1 st found in Cro-Magnon cave in France Oldest fossils in Africa 160, 000 years ago

Modern Humans How did we get all over the Earth? Multiregional hypothesis H. sapien evolved from H. erectus in local populations all over the world Out-of-Africa hypothesis H. sapien evolved from H. erectus ONLY in Africa and then migrated out Supported by DNA evidence