Lecture 16 - Mammals

Question 1

Explain mammal evolution

Answer 1

• About 4500 species of mammals belong to the class Mammalia
• They evolved during the Mesozoic era from Therapsid, extinct mammal like reptiles.
• True mammals appeared during the Jurassic period
• Some of the early mammal groups were monotremes and marsupials
• Placentals evolved later
• Mammals have hair and mammary glands
• They are endothermic and homeothermic

Question 2

What are the four characteristics that distinguish Class: Mammalia

Answer 2

• Mammary gland
• Hair
• Specialized teeth
• Enlarged skull

Question 3

Explain mammary glands and mammals

Answer 3

Mammary gland-secretes milk, New borne suckle this fluid

Question 4

Explain hair and mammals

Answer 4

• All mammals have hair.
• Adult whales are hairless
• Hair can take on functions other than insulation
• Cats and dogs have sensory hair. In hedgehogs hairs are long stiffened and form sharp quills for defence

Question 5

Explain specialised teeth and mammals

Answer 5

Teeth are differentiated- and adapted for different types of diet.
Rodents incisor teeth grow through out life

Question 6

Explain enlarged skull and mammals

Answer 6

• The brain is enlarged
• Single lower jaw bone
• Three bones in the middle ear (reptiles have one)
• Mammals are the only animals that has horns or antlers and hooves

Question 7

Explain Class : Mammalia in more detail

Answer 7

• Diphyodont teeth (deciduous/milk teeth is replaced by permanent teeth)
• Lower jaw – dentary, contains the teeth of the lower jaw and is the strongest bone in your face. It moves to perform chewing action.
• Respiratory system consist of lungs
• Brain highly developed; 12 pairs cranial nerves
• Endothermic & ectothermic
• Heart – 4-chambered; double-looped circulatory system

Question 8

What are the three different types of mammals

Answer 8

1. Egg-laying mammals
2. Marsupial mammals
   3.Placental mammals

Question 9

Explain egg laying mammals

Answer 9

• Sub class Prototheria
• They are also called Monotremes – this name comes from the anatomy of these animals
• The urinary tract, digestive tract and reproductive tract share one single opening to the outside, called the cloaca
• Monotremes lay hard-shelled eggs
• Hatchlings drink milk seeping from modified sweat glands (platypus) or milk secreted into a pouch (spiny anteater, Echidna sp.)

Question 10

Explain placental mammals

Answer 10

• Development is regulated by placenta
• Placenta allows nutrient, oxygen, waste product exchange between mother and foetus
• Acute senses and well-developed brain

eg ) 1. Giraffa camelopardalis
Order Artiodactyla

2. Ceratotherium simum –
   rhinoceros (white)
3. Zebra
   Order Perissodactyla

Question 11

Explain Marsupial mammals

Answer 11

• Mammals with pouches
• Subclass Theria
• Young are born very immature(1-2 cm )
• After birth they crawl to the mothers pouch(marsupium)
• Babies attach to mammary glands in the pouch of the mother.

Examples: koala bears, kangaroo, Tasmanian devil (Sarcophilus harrisii)