Ch12 Study Guide: Birds and Mammals

Concepts to Know

All kinds of birds and all kinds of mammals are endotherms.

The difference in air pressure above and below a wing causes lift.

Placental mammals are divided into groups based on adaptations such as how they eat.

A gestation period is the length of time between fertilization and birth.

Birds usually sit on their eggs to keep the eggs warm.

All kinds of birds lay eggs.

All mammals feed their young with milk.

Mammals are classified as monotremes, marsupials, or placental mammals according to how their young develop.

Both a mammal’s fur and a bird’s feathers function to help the animal keep warm.

No mammal has a three-chambered heart.

Down feathers trap air next to a bird’s body, keeping the bird warm.

The placenta in an organ through which some mammals receive food and oxygen from their mothers during gestation.

Mammals are assisted in breathing by a large muscle located under the lungs called the diaphragm.

Birds can store food in an organ called a crop before the food goes to the stomach.

Koalas, kangaroos, and opossums belong to the marsupial group of mammals.

All mammals are invertebrates (f; vertebrates).

They young of marsupials are more developed at birth than the young of placental mammals (f; less).

Contour feathers help a bird keep its balance during flight (true).

Monotremes are mammals that lay eggs (true).

The angle and shape of a bird’s feet provide lift (f; wings). Essay

Compare and contrast the shape and function of the four kinds of mammal teeth. Incisors have a sharp edge. They are used to cut and bite off food. Canines are pointed and are used for stabbing and tearing. Premolars and molars have a broad, flattened surface for grinding food.

What is a placenta and what I its function? The placenta is an internal organ in pregnant females that one group of mammals has. Food and oxygen pass from the mother to her young through the placenta, and wastes pass from the young through the placenta to the mother, where they are eliminated by her body.

Discuss the similarities and differences in the development from birth of a marsupial with that of a placental mammal. Both are born alive and both are fed milk. Newborn marsupials are very small. They stay in a pouch and nurse until they develop enough to come out. Newborn placental mammals are relatively more developed then new born marsupials. Newborn placental mammals do not live in a pouch.

What advantages does a bird circulatory system provide over the other circulatory systems in animals? The bird circulatory system has two loops and a four-chambered heart. The advantage of a four-chambered heart is that there is no mixing of oxygen-rich and oxygen-poor blood between the two loops. Therefore, blood that arrives in the body’s tissues has plenty of oxygen.

Compare and contrast the three kinds of bird flight – flapping, soaring, and gliding, and diving. Include information on which kind or kinds use a lot of energy and which use a little. In flapping flight, the bird continuously flips its wings and uses a lot of energy. Gliding and soaring use much less energy. A gliding bird keeps its wings outstretched as it flies downward. A soaring bird keeps its wings outstretched and flies upward as the air surrounding it moves upward. A diving bird tucks its wings and lets gravity take over. Diving does not use lift at all.

Describe what happens to a seed from the time it is eaten by a sparrow until it leaves the stomach. The seed is picked up by the bill but can’t be chewed. From the mouth the seed passes into the crop where it is stored. Next, it passes to the stomach where digestive juices are added. It is crushed by the muscular gizzard before passing out of the stomach.

Explain how reproduction in birds and reptiles is similar. Like reptiles, birds have internal fertilization and lay eggs. Bird eggs are similar to reptile eggs, except that their shells are harder. In most bird species, the female lays the eggs in a nest that has been prepared by one or both parents. Most reptiles do not care for their eggs after laying them, whereas most birds do.

In addition to wings and feathers, birds have other adaptations that help them fly. Describe at least two of these adaptations. Other adaptations are hollow bones, which help make the birds lighter; air sacs, which enable birds to extract much more oxygen from each breath than other animals can; and large chest muscles, which move the wings.