Eutheria (Placental Mammals) Flimsy Paper Notes

Giselle Ilada

Eutheria (Placental Mammals) Flimsy Paper Notes

Intro:

·  Class Mammalia contains the most familiar group of animals.

·  They are the most widespread and diverse class of organisms on land.

·  Mammals are highly adaptable and they are able to modify their behavior to changing environments.

·  They have a higher success rate because of their ability to maintain a constant internal body temperature.

·  Eutheria are placental mammals that all bear live young, which are nourished before birth by the mother’s placenta.

Habitats:

·  Placental mammals can be found all over the world and in a variety of habitats.

1.  Grasslands are too dry for trees but retain enough moisture to prevent it from being a desert. It’s an open habitat where grasses are the dominant plants.

2.  Savannas are tropical/subtropical grasslands that have scattered trees and shrubs.

3.  Deserts are dry and are always exposed to intense sunshine. Rain falls in short periods, but in torrential downpours.

4.  Semideserts are similar. They are more widespread and have modest rainfall. Plant life is more abundant in this type of desert.

5.  Tropical rainforests flourish in the tropics. Tropical forests are humid and have a stable climate. Seasonal forests have heavier rainfalls or monsoons.

6.  Other types of forests are temperate and coniferous forests: Temperate forests have a wide range of climates with deciduous plants.

Coniferous forests contain the toughest trees that form a dense, sheltered habitat. Rainfall is also heavy here.

7.  Other habitats include mountains, both temperate and tropical. These habitats have low temperature ranges and low levels of oxygen. Mountains are divided into distinct zones, each supporting various forms of plant and animal life.

8.  The Arctic and Antarctic are the coldest habitats on earth. The Arctic is the frozen shallow end of the ocean that also includes widespread tundra. The Antarctic is an ice covered continent surrounded by the world’s stormiest seas.

9.  The last type is the ocean which includes inshore and open seas. It forms the largest continuous habitat on earth. Like the mountainous habitat, life is found at all levels, from the surface to the deepest trenches.

Feeding Mechanisms:

1.  Herbivores are animals that feed on plants. Examples include elephants, rabbits, and hoofed animals.

Carnivores feed on other animals. They can sometimes be called insectivores which are animals that feed on insects. Examples of carnivores are dogs, cats, mustelids, hyenas, and whales.

Omnivores rely on both prey and plants. This group includes some bears , various forms of primates, baboons, and pigs/hogs.

2.  Teeth Comparisons:

·  Omnivores have teeth that have a multicuspid chewing surface. These animals tend to have molar teeth and strong jaw muscles.

·  Carnivores have teeth with a sharp cutting edge, such as the canines. They also have powerful jaws.

·  Herbivores have teeth with a much broader, grinding surface. Rabbits, hares, and pikas have a slightly different arrangement of teeth. They have upper and lower incisors at the front with peg teeth directly behind it. The molars are round at the back.

·  The make up of teeth is different for whales and toothed whales. Toothed whales have simple, conical, pointed teeth. Whales have two rows of baleen plates on each side of the upper jaw. Their jaws are elongated, allowing them to feed on amphipods or small crustaceans.

3.  Digestion:

·  Carnivores have a simple digestive tract because the proteins, lipids, and minerals found in meat don’t require specialized digestion.

·  Herbivores have a more complex digestive tract. Plants contain complex carbohydrates and cellulose. Their digestive tract hosts bacteria that ferment the food and aid digestion. They are found in the stomach and cecum of the animal.

·  Digestion in Hoofed Mammals: In hoofed mammals, there are two types of digestion.

a.  In ruminants, food passes slowly through their system to obtain nutrition. These herbivores thrive where food is limited but of high quality. Ex: cattle, sheep, giraffes, deer, buffalo

b.  The second type is the hindgut fermenter where food is not retained in the stomach and therefore passes through the system more quickly. They thrive where food is plentiful but of poor quality. As a result, more food must be eaten to obtain enough nutrients. Ex: horses, rhinoceroses, rabbits

Types of Reproduction:

·  The usual sequence of reproduction is: copulation, ovulation, fertilization, implantation and pregnancy, and birth.

·  Fertilization is internal and the young are nurtured by the mother’s placenta. The placenta allows nutrients and oxygen to pass.

·  Like the marsupials, placental mammals give birth to live young. The difference is that they are nurtured by their mother for a time before becoming independent. Unlike marsupials, the offspring are not raised in a special pouch.

·  The degree of development varies among Eutherian groups.

Unique Characteristics:

·  Female mammals have mammary glands that produce milk to feed their offspring.

·  They are the only animals with a covering of hair on the body.

·  Mammals have a main artery leaving the heart and curves to the left forming the aortic arch.

·  They have a diaphragm that separates the body cavity into two sections

·  The lower jaw bone, carrying the teeth, and the skull bone meet to form the joint. Also the lower jaw bone is a single bone.

·  The mammal’s middle ear contains 3 bones: stirrup, anvil, and hammer.

·  There are two knobs at the base of the skull that fit into the topmost neck vertebra.

Sources:

http://www.earthlife.net/mammals/mammal.html

http://www.life.umd.edu/classroom/bsci338m/Lectures/Reproduction.html

http://www.ucmp.berkeley.edu/mammal/eutheria/placental.html

http://www.ucmp.berkeley.edu/mammal/eutheria/eutherialh.html

http://en.wikipedia.org/wiki/Mammals

Burnie, David, and Wilson Don. Animal. New York: DK Publishing. Inc, 2001. Print.