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 MammalsOnce 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 (15X) mostly in cerebrum

Thinking & processing center

5 major senses: smell, touch, sight, taste, & hearing

Some use echolocation to navigateHigh-frequency sound waves bounce off objects

Development

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 ClassificationSection 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 teethTwo 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

Order Carnivora

Examples: dogs, cats, raccoons,& bears

Meaning “ animals that eat meat”

Strong jaw, canine teeth, claws, and sense of smell

Pinnipeds: aquatic carnivoresSea lions, seals, & walruses

Order Artiodactyla

Examples: deer, cattle, giraffe, & pigs

Ungulates: mammals with hoofsEven number of toes

Most are herbivoresLarge 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 nostrilsblowholes

Use echolocation

Little hair except around snoutKeep 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 bipedalismTendency to walk upright on two legs

Adaptations for walking:Bowl-shaped pelvisS-shaped spineShape of foot

Hominids

Include humans and extinct humanlike anthropoid species

All hominids were bipedialAll other anthropoids are quadrupedal (walking on four limbs)

Becoming Human Video

Fossil HominidsHumanlike 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 230,000-30,000 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 1st found in Cro-Magnon cave in France

Oldest fossils in Africa160,000 years ago

Modern Humans

How did we get all over the Earth?

Multiregional hypothesisH. sapien evolved from H. erectus in local populations all over the world

Out-of-Africa hypothesisH. sapien evolved from H. erectus ONLY in Africa and then migrated out

Supported by DNA evidence