1. Section 2: Groups of Mammals
Preview
Bellringer
Key Ideas
Monotremes
Marsupials
Placental Mammals
Summary

2. Bellringer
Copy the following categories on a sheet of paper: Terrestrial, Marine, Carnivorous, and Herbivorous. Make a list of mammals that fit into each category.

3. Key Ideas
What key characteristic sets monotremes apart from all other mammals?
What are the key characteristics of marsupials?
How common are placental mammals, and how does their development differ from the development of monotremes and marsupials?

4. Monotremes
Monotremes are a small group of mammals found only in Australia and New Guinea.
Monotremes share more traits with reptiles than with other mammals.
Monotremes are also the only living mammals that lay eggs.

5. Monotremes, continued
Like reptiles, monotremes have legs that sprawl to the side instead of being under the body.
Also like reptiles, monotremes are the only mammals that have a cloaca, a common passageway for the digestive, reproductive, and urinary systems.
Finally, adult monotremes do not have teeth.

6. Monotremes, continued Monotremes are mammals because they have hair.
They produce milk to feed young. However, female monotremes do not have nipples.
Instead of nursing, the young lap up milk that oozes from glands located on their mother’s belly.
The only living monotremes are the duckbill platypus and echidnas.

7. Marsupials
Marsupials include kangaroos, wombats, koalas, and opossums.
The females of most marsupials have a pouch, and their young spend most of their time developing inside this pouch while they nurse and grow.
Marsupials are the most diverse group of mammals in Australia.

8. Marsupials, continued Marsupials are also found in South America.
Only one marsupial, the Virginia opossum, is native to North America.
Scientists believe that marsupials probably moved into Australia from South America before the breakup of Pangaea.

9. Marsupials, continued
At that time, South America and Australia were connected via Antarctica.
After the continents separated, marsupials evolved and diversified in isolation from placental mammals.
The habitats and lifestyles of marsupials in Australia, New Zealand, and nearby islands are similar to those of placental mammals.

10. Marsupials, continued
Kangaroos and wallabies often live in large groups and, like deer, are herbivores.
Much like monkeys, tree kangaroos are able to climb trees and jump from limb to limb.
Gliders and possums are similar in habits to squirrels.

11. Marsupials, continued
Some marsupial predators are similar to small cats.
Tasmanian devils are similar to badgers in some ways.
The Tasmanian tiger, a marsupial wolf, was hunted to extinction by European settlers.

12. Placental Mammals Placental mammals are the most familiar mammals.
Cats, dogs, cows, horses, and humans are placental mammals.
Placental mammals make up nearly 95% of all mammal species.

13. Visual Concept: Types of Terrestrial Placental Mammals
Click the button below to watch the Visual Concept.

14. Placental Mammals, continued
The young of placental mammals develop inside the female’s uterus, where they are nourished by nutrients from her blood.
Placental mammals have a longer period of internal development than marsupials do.
The young of most placentals are more developed at birth than the young of marsupials are.

15. Placental Mammals, continued
There are many types of placental mammals, which vary greatly in size, shape, diet, and habits.
The orders of placental animals and their relationships to each other and the other mammal groups are shown on the following slide.
The characteristics of each major group of placental mammals are also listed on the following slides.

16. Phylogenetic Diagram of Mammals

17. Placental Mammals, continued
Artiodactyla
Includes pigs, camel, deer, antelopes, and cattle
Have an even number of toes within their hooves
Also called ungulates

18. Placental Mammals, continued
Perissodactyla
Includes horses, zebras, tapirs, and rhinos
Have an odd number of toes within their hooves
Like artiodactyls, also called ungulates

19. Placental Mammals, continued
Cetacea
Includes whales and dolphins
Have a streamlined body and move through water with a powerful fluke
Have a layer of blubber to keep them warm

20. Visual Concept: Types of Placental Marine Mammals
Click the button below to watch the Visual Concept.

21. Placental Mammals, continued
Rodentia
Includes rats, mice, and beavers
Have teeth that are specialized for gnawing
More than 40% of all placental mammals are rodents

22. Placental Mammals, continued
Primates
Includes humans, apes, lemurs, and monkeys
Most are tree dwellers
Have grasping hands and feet and long arms and legs that aid in climbing
Have excellent eyesight and depth perception

23. Placental Mammals, continued
Chiroptera
Includes all bats
Only mammal capable of flight
Most bats are carnivorous and use echolocation to find insects
Other bats eat fruit or nectar from night-blooming flowers

24. Placental Mammals, continued
Xenarthra
Includes anteaters, sloths, and armadillos
Anteaters use long, sticky tongues to capture insects
Sloths eat mostly leaves
Armadillos have simple teeth and are omnivorous

25. Placental Mammals, continued
Lagomorpha
Includes rabbits, hares, and pikas
Rabbits and hares have long hind legs and are specialized for hopping
Pikas have short limbs and live in mountainous regions of North America and central Asia

26. Placental Mammals, continued
Sirenia
Includes manatees and dugongs
Relatives of elephants
Have front flippers and a flattened tail for swimming
Sometimes called sea cows, sirenians graze on aquatic plants

27. Placental Mammals, continued
Insectivora
Includes shrews, hedgehogs, and moles
Mainly eat insects
Moles have adaptations for burrowing, including short, powerful forelimbs with long claws

28. Placental Mammals, continued
Proboscidea
The order of elephants, the largest land animals alive today
Trunk is an elongated nose
Upper lip can be used for picking up food, water, and objects
An elephant’s tusks are modified upper incisors

29. Placental Mammals, continued
Carnivora
Cats, dogs, foxes, bears, raccoons, pandas, and hyenas are carnivores
Long canine teeth are specialized for capturing prey and tearing flesh
Some carnivores eat more than meat. Raccoons and bears are omnivores, pandas are herbivores

30. Placental Mammals, continued
Domestic Mammals
Domestic animals are animals that have been kept and bred by people for special purposes.
Domestic animals may provide work, food, clothing, or companionship.
Most domestic animals are placental mammals whose association with humans dates back at least 2,000 years.

31. Placental Mammals, continued
Domestic animals include dogs, cats, cattle, horses, donkeys, mules, rabbits, sheep, goats, pigs, camels, llamas, and alpacas.
Various breeds of domestic mammals have been developed through selective breeding.
For example, some breeds of goats produce more milk than others.

32. Placental Mammals, continued
Other goats, such as angora goats, are bred for their fine hair, which is spun into yarn.
Some domestic mammals are hybrids of two species.
Mules, for example, are the offspring of a female horse and a male donkey.

33. Summary
Monotremes share more traits with reptiles than with other mammals. Monotremes are the only living mammals that lay eggs.
The females of most marsupials have a pouch, and their young spend most of their time developing inside the pouch while they nurse and grow

34. Summary, continued
Placental mammals make up nearly 95% of all mammalian species. The young of placental mammals develop inside the female’s uterus, where they are nourished by nutrients from her blood.