1. Introduction to Mammals
And Diversity of Mammals

2. Introduction to Mammals
Endothermic animals (generate their body heat internally = an example of homeostasis), most viviparous (live-bearing, the exception being monotremes), all have mammary glands and hair, breathe air, and have four-chambered hearts

3. Mammal Evolution and Diversity
First true mammals appeared about 200 million years ago
Most mammals are terrestrial, although dolphins, porpoises, and whales are totally aquatic.
3 major groups of mammals:
Monotremes
Marsupials
Placentals (aka eutherians)

4. Monotremes Egg-laying mammals
Six species found in Australia and New Guinea – duck-billed platypus, spiny anteaters
Both the reproductive system and the urinary system open into a cloaca that is similar to the cloaca of reptiles

5. Marsupials
Mammals bearing live young that complete their development in an external pouch. Once inside the marsupium (pouch), the embryo locates a nipple, attaches, and spends several months there
Mostly found in Australia
Opposum only North American marsupial
Kangaroo, koala, wallabies

6. Placentals (aka Eutherians)
Mammals in which egg implants in the uterus
In placental mammals, nutrients, oxygen, carbon dioxide, and wastes are exchanged between the embryo and mother through the placenta
Eutherian placentas provide more intimate and long-lasting association between the mother and her developing young than do marsupial placentas
Most widespread – dogs, cats, humans

7. Feeding in Mammals
Teeth tell the tale – lots of incisors and canines = predator, lots of molars = herbivore, both = omnivore (humans, bears)
CARNIVORE
HERBIVORE
Molars crush and grind food. The ridged shape of the wolf’s molars and premolars
allows them to interlock during chewing, like the blades of scissors. The broad,
flattened molars and premolars of horses are adapted for grinding tough plants.
Chisel-like incisors are used for
cutting, gnawing, and grooming.
Canines are pointed teeth. Carnivores
use them for piercing, gripping, and tearing.
In herbivores, they are reduced or absent.
Jaw joint
Jaw joint
Horse
Wolf

8. Feeding in Mammals (continued)
Most consume a lot to maintain metabolism
Rumen – specialized stomach allows some herbivores to digest cellulose (cows)
Cecum – large, dead-end sack off intestine; acts like rumen and in humans is the appendix
Blood feeders – vampire bats
Filter feeders – baleen whales

9. Respiration
Lungs powered by two sets of muscles – chest and diaphragm (diaphragm increases volume in chest cavity)

10. Circulation in Mammals
Four chambered heart with double loop system – lungs and body loops

11. Excretion in Mammals
Kidneys filter urea from blood and recycle other compounds (sugars and salts)
Best kidney of all animals

12. Response in Mammals Most highly developed brain of all animals
Cerebrum – controls thinking and learning – large in mammals
Cerebellum – coordinates movement
Medulla – regulates body functions
Well-developed sense of sight, hearing, and smell

13. Movement in Mammals
Have a variety of adaptations – shoulders and pelvic girdles
4 limbs – hooves, hands, wings, flippers

14. Reproduction in Mammals
Internal fertilization
Most are viviparous
Pouch – marsupial
Placenta – nutrients, oxygen and wastes exchanged through this sac-like organ
Gestation period – length of time spent developing in uterus – can range from a few weeks (mice) to almost two years (elephants) – larger the young, longer the gestation period

15. Reproduction in Mammals (continued)
Young spend a long time developing with mother after birth – important reason for evolutionary success
Advantages?
More likely to survive and reproduce with great success
Disadvantages?
Takes a lot of energy and prevents parents from reproducing until young are on their own

16. Orders of Mammals Insectivora – shrews and moles – eat insects
Chiroptera – bats – eat insects, frogs, fish, fruit
Edentata – sloths, anteaters, and armadillos
Rodentia – mice, rats, squirrels, beavers – incisors constantly grow during entire lifetime
Lagomorpha – rabbits and hares – herbivores
Carnivora – cats, dogs, wolves, bears, weasles, seals, hyenas
Cetacea – whales, dolphins, porpoises
Sirenia – manatees and sea cows
Artiodactyla – cattle, sheep, goats, hippo, giraffe, pigs – even number of toes
Perissodactyla – horses, zebras, tapirs, rhinos – odd number of toes
Proboscidea – elephant (African and Asian)
Primates – humans, monkeys, apes