Mammals

Chapter 45

Cenezoic EraAge of mammals (70 mya)

Mesozoic EraAge of reptiles (200 mya)

Rise of mammals

• Climate changes favored survival of mammals– Mammals are endothermic “warm-blooded”– Abrupt change

• Colder• Fewer swamps and veggitation

1. Eohippus (Hyracotherium) -Eocene epoch (65 mya) - 4 toed -size of a small dog

2. Mesohippus -Oligocene epoch (38 mya) - 3 toed -size of a sheep

3. Equus -pliestocene epoch (2.5 mya) - one toed -size varies from miniature to draft horse

Origin of Horses and camels

• First appeared in N. America

• Migrated to Europe, Asia and Africa via land bridges

• Became extinct in N. America

• Reintroduced to N. America by Europeans

Extinction

• Death of an entire species– Examples: Wooly Rhino, Wooly Mammoth,

Saber toothed tiger, Hump-less Camel, Straight Horned Bison

– Natural process: can be hurried by man– Has occurred in the past, is ocuring NOW and

will continue in the future!

Extinct species

Characteristics of Mammals• mammary glands to feed

young • body covered with hair or fur • live birth • lung breathing • endothermic • diaphragm breathing muscle • four chambered heart • seven cervical vertebrae • pectoral and pelvic girdles-

two pairs of limbs • highly developed brain

cerebrum (emotions) cerebellum (equilibrium and movement)

Organ Systems

• Most highly developed of vertebrates– Thermoregulation- maintain constant body temperature– Hypothalamus- part of the brain that controls thermoregulation– Metabolic rate- respiration, heart rate chemical processes– Endothermic- internal control of body temp (Exothermic- external

control of body temp)– Surface to volume ratio!- keeps exothermic organisms small,

optimize surface area in comparison to body volume

Endothermy- Internal regulation of body temperature

Respiratory System

A. Air Flow1. Nasal passage- warms, moistens and cleans

2. Sinuses- warm and moisten

3. Pharynx- back of throat

4. Larynx – voice box with vocal cords

5. Trachea – windpipe allows air to go to the lungs (cartilage rings)

6. Right/Left Bronchi- Branches of windpipe that enter lungs

7. Right/Left Bronchail Tree- bonchioles enter lung tissue

8. Right/Left Lunga. Alveoli – Respiration takes place here

b. Arterioles/venules

c. O2/CO2 gas exchange

Respiratory System

Mammalian Heart

• Compare hearts of – fish (2 chamber)– Reptile (3 chamber)– Amphibian (3 chamber)– Mammal (4 chamber)

Heart comparison

Fish

Frog

Mammal

Mammalian Heart

1. Chambers- four with a septum dividing

2. Most efficient- there is no mixing of O+ and O- blood

3. Steps of circulation in the bodya. Body send blood without O2 to the

i. Superior (above the heart) and inferior vena cava

ii. Right atrium

iii. Tricuspid Balve

iv. Right Ventricle

v. Pulmonary Arterey

i. Lung1. Pulmonary Vein

ii. Left Atrium1. Bicuspid valve

2. Left ventricle

iii. Aorta1. Carotid – to head

2. Brachiocephalic- to neck / chest

3. Subclavian – body

(color code the order above as red (O+) or blue (O-) by highlight or underline)

Circulatory System

Mammalian Nervous System

a. Largest

b. Cerebrum: controls voluntary movements, thought, emotion, memory

c. Cerebellum: controls involuntary movements, muscle coordination, equilibrium

d. Medulla oblongota: controls vital body functions, internal organs

Nervous System

Mammal Brain

Mammalian Reproductive system and parental care

a. Grouped by increased efficiency of reproduction

1. Monotremes

2. Marsupials

3. Placentals

26

Mammal OrdersThere are 19 orders of mammals in the class Mammalia in which 17 nourish unborn young in the placenta, egg laying mammals and marsupials

Monotremes: egg layers

1. Order monotremata- oviparous2. Examples

a. Duck- billed platypus

b. Spiny echnida