Groups of Mammals

Classification of Mammals

• Mammals range in size from a tiny shrew (1.5 grams) to a blue whale (150 tons)

• Mammals inhabit more environment than any other vertebrates

• Modern mammals are classified into three groups– Monotremes– Marsupials– Placental Mammals

Monotremes

• Monotremes are a small group of organisms found only in Australia and New Guinea

• Monotremes share more traits with reptiles than with other mammals.

• Monotremes are the only living mammals that lay eggs

Monotremes are similar to reptiles because…

• Monotremes have legs that sprawl to the side instead of being under the body

• Monotremes are the only mammals to have a cloaca – A common passage way for the digestive,

reproductive and urinary systems

• Adult monotremes DO NOT have teeth

Monotremes are like other mammals because…

• Monotremes have hair• Monotremes produce milk to feed their

young– However, female monotremes DO NOT have

nipples– Young drink milk that oozes from glands that are

located on their mother’s belly

Marsupials

• Marsupials include: Wombats, Koalas, and opossums

• Females of most marsupials have a pouch, and their young spend most of their time developing inside the pouch while they nurse and grow

Marsupials

• Marsupials are the most diverse mammals in Australia – Marsupials are also found in South America and

North America

Marsupials

• The habitats and lifestyles of marsupials in Australia, New Zealand, and nearby islands are similar to those of placental mammals

• Examples:– Kangaroos and Wallabies often live in large groups

like deer (a placental mammal)– Tree kangaroos are similar to monkeys because

both can climb– Gliders and possums are similar in habits to

squirrels

Placental Mammals

• Cats, dogs, cows, horses, and humans are placental mammals

• Placental mammals make up nearly 95% of all mammal species

• The young of placental mammals develop inside the female’s uterus– Here they are nourished by nutrients from her

blood

Placental Mammals

• Placental Mammals have a longer period of internal development than marsupials

• Placental Mammals are more developed at birth than the young of marsupials

• There are many types of placental mammals, which vary greatly in size, shape, diet and habits

Domestic Mammals

• Domestic Mammals are animals that have been kept and bred by people for special purposes

• Domestic Mammals may provide work, food, clothing, or companionship

• Most Domestic Mammals are placental mammals whose association with humans dates back up to 15,000 years

Domestic Mammals

• Domestic Mammals include: dogs, cats, cattle, horses, donkeys, mules, rabbits, sheep, goats, pigs, camels, llamas, and alpacas

How Domestic Mammals are Made

• Various breeds of domestic mammals have been developed through selective breeding – Example: Some breeds of goat produce more milk than

others

• Some domestic mammals are hybrids of two species– Example: Mules are formed from a female horse and

male donkey