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Zoology Chapter 36

Page history last edited by Shelly Turner 10 years ago

Chapter 36:  Mammals

 

 

Using your vocabulary words, make notecards/flashcards that you can use outside of class to study. 

  

 

Work on your Directed Reading in class every chance you get.  Remember that I will assist you on the harder questions.  This assignment is due the day we take the test on this chapter.  Use the information in this assignment as a study guide for your test. 

 

This study guide is to help you study for your test.  It should not be the only item you use to study w hen preparing for the test.  Remember to complete your Directed Reading for every chapter along with writing your vocabulary words on notecards to help you remember them.  And always remember to listen carefully in lecture because all of the information in this study guide will be covered.testing 

 

Section 1  The Mammalian Body

 

Key Characteristics of Mammals

         Almost all of today’s large, land-dwelling vertebrates are mammals. 

         Mammals are well-adapted for terrestrial living. They are able to retain water more efficiently than reptiles.

 

Characteristics of Mammals

 

 


 

Hair 

         Of all animal species, only mammals have hair. A hair is a filament composed mainly of dead cells filled with the protein keratin. 

         The primary function of hair is insulation. The hair of some mammals helps them blend in with their surroundings.  In some mammals, specialized hairs serve a sensory function.

 

         

 

Mammalian Teeth

 

         Mammals have only two sets of teeth throughout their lives: baby teeth or milk teeth, then permanent teeth. 

         Mammals have four kinds of teeth: incisors, canines, premolars, and molars. 

         A mammal’s teeth are specialized for the food it eats.

 

 

 

Body Temperature

 

Like birds, mammals are endotherms, generating heat internally through the rapid metabolism of food. Because a mammal’s body temperature remains relatively constant regardless of the temperature of its surroundings, mammals can be active at any time of day or night. They also can live in very cold climates, where most ectothermic amphibians and reptiles cannot. In addition, endothermic metabolism permits mammals to sustain activities that require high levels of energy, such as running or flying long distances.

 

 

 

To maintain the high metabolic rate required by an endotherm, a mammal must eat about 10 times as much food as an ectotherm of similar size. Metabolizing this food requires a considerable amount of oxygen. Mammals, like birds, have respiratory and circulatory systems that are very efficient at acquiring and distributing oxygen.

 

         Like birds, mammals are endotherms. They can be active at any time of day or night. They can also live in cold climates. 

         A mammal must eat about 10 times as much food as an ectotherm of similar size. Mammals have a high metabolic rate and require considerable amounts of oxygen.

 

Respiratory System

 

Mammalian lungs have a large internal surface area that aids the exchange of oxygen and carbon dioxide. Thus, mammalian lungs are much more efficient at obtaining oxygen from the air than are reptilian and amphibian lungs. Respiration in mammals is aided by the diaphragm, a sheet of muscle that separates the chest cavity from the abdominal cavity. When the diaphragm contracts, the chest cavity enlarges, drawing air into the lungs.  The lungs of mammals contain small, grape-shaped chambers called alveoli (al VEE uh lie), (singular, alveolus). Alveoli provide a very large respiratory surface area. In more active mammals, the alveoli are smaller and more numerous, further increasing the surface area for diffusion.

 

         Mammalian lungs are more efficient at obtaining oxygen than are reptilian and amphibian lungs.

         Mammalian lungs contain alveoli, small chambers that provide a very large surface area.

 

Mammalian Lungs

 

 

Heart and Circulatory System

 

Like crocodiles and birds, mammals have a four-chambered heart with a septum that completely divides the ventricle. The division of the ventricle creates two pumping chambers, one for each loop of the mammal’s double-loop circulatory system. One chamber pumps oxygen-rich blood to the body, while the other pumps oxygen-poor blood to the lungs. Because the two do not mix, only oxygen-rich blood is delivered to the tissues, a condition vital for meeting the oxygen needs of endotherms.

 

         Mammals have a four-chambered heart. A septum completely divides the ventricle into two pumping chambers.

         One chamber pumps oxygen-rich blood to the body. The other chamber pumps oxygen-poor blood to the lungs. The two kinds of blood do not mix.

 

External Structures of a Grizzly Bear

Internal Structures of a Grizzly Bear

 

Parental Care 

         Mammals nourish their young with milk. Milk is produced by mammary glands located on the female’s chest or abdomen.

         Young mammals are nourished on milk from birth until weaning, the time when the mother stops nursing them.

 

         

 

Section 2 Today’s Mammals

 

Mammalian Diversity

         Mammals are more diverse in size, anatomy, and habitat than all other vertebrate groups.

 

Comparison of Bats and Whales

 

 

 

 

Types of Mammals

 


 

Reproduction 

         All mammals reproduce by internal fertilization.

         Mammals are divided into three groups based on differences in how and where the fertilized egg develops.

 

Comparing Reproduction in Mammals

 


  

Monotremes

         The monotremes (order Monotremata) are the most primitive of all mammals. Among living mammals, only monotremes reproduce by laying eggs.

         There are three living monotreme species: the duckbill platypus and two species of echidnas.

 

Marsupials

         The marsupials (order Marsupialia) include kangaroos, koalas, and opossums.

         In marsupial mammals, the young are born incompletely developed. They crawl to their mother’s nipples located in a pouch on her abdomen, then continue their development for several months.

 

         

 

Placental Mammals

         The young of placental mammals develop within the female’s uterus. The placenta enables the diffusion of nutrients and oxygen from the mother to the fetus. The period of time between fertilization and birth is called the gestation period.

         Most domestic animals (such horses, cattle, dogs, and cats) are placental mammals.

 

Function of a Placenta

 


 

Types of Terrestrial Placental Mammals

 


 

Modern Placental Mammals 

         There are 19 orders of placental mammals, which include more than 90 percent of all mammal species.

         The vast majority of mammal species are found within 12 orders.

 

Order 1: Order Rodentia

         About 40 percent of all mammal species are rodents. Rodents have teeth that are specialized for gnawing.

         Most rodents are small in size. Rodents have a rapid rate of reproduction.

 

Order 2: Order Chiroptera

         This order is composed of bats, the only mammals capable of true flight. Most bats live in groups and are active only at night.

         Most bats eat insects, using echolocation to catch insects while in flight.

 

Echolocation

Consider also the differences between a bat and a whale. These two mammals are adapted to live in very different environments. Bats fly and are active primarily at night, while whales are permanently aquatic. However, both groups face a similar challenge—how to navigate in an environment where visibility is often limited. Bats and some whales have a similar solution to this problem: they use echolocation, which works something like the sonar of a ship. In echolocation, animals emit high-frequency sound waves. As the waves travel, they strike objects in the environment, and a portion of each wave is reflected back to the animal. The brain interprets the reflected wave, or echo, revealing the object’s size and location.

 


  

Order 3: Order Insectivora

         This order consists of small mammals, such as the shrew, that eat mainly insects.

         Insectivores are the mammals most similar to the ancestors of the placental mammals.

 

Order 4: Order Carnivora

         Most species in this order are flesh-eating hunters.

         Carnivores consist of two subgroups: the cat family and the dog family.

         Carnivores have excellent senses of smell, vision, and hearing.

 

Anatomy of a Tiger

 


 

Order 5: Order Pinnipedia

         This order of marine carnivores includes seals and sea lions.

         All four limbs of pinnipeds are modified as flippers for swimming. Their bodies are streamlined for rapid movement through the water.

 

Order 6: Order Primates

         Humans belong to the order Primates.

         Other members of this order include the prosimians, monkeys, and apes.

 

        Most nonhuman primates are tree-dwellers.

 

Order 7: Order Artiodactyla

         Mammals belonging to this order and the following order, Perissodactyla, are ungulates, mammals with hooves. Artiodactyls have an even number of toes.

         Many artiodactyls have a stomach with a storage chamber called a rumen. Mammals with a rumen regurgitate partially digested food, called cud, rechew it, and swallow it again for further digestion.

 

Order 8: Order Perissodactyla

         Ungulates with an odd number of toes within their hooves are classified as perissodactyls. This order includes horses, zebras, and rhinoceroses.

         Perissodactyls lack a rumen and do not chew their cud.

 

Adaptations for Plant Eating

 


 

Order 9: Order Cetacea

         Cetaceans are divided into two groups: the predatory toothed whales, dolphins, and porpoises, and the filter-feeding baleen whales.

 

 

Baleen

 

 

 

Order 10: Order Lagomorpha

        This order is composed of rabbits and hares. Like rodents, lagomorphs have long, continually growing incisors. They also have another pair of incisors

  that grow behind the first pair.

         Rabbits and hares have long hind legs and are specialized for hopping.

 

Order 11: Order Sirenia

         Sirenians include dugongs and manatees, barrel-shaped marine animals that eat aquatic plants. They have front limbs modified as flippers.

         Sirenians are closely related to elephants and are often called sea cows.

 

Types of Placental Marine Mammals

 


 

 

Order 12: Order Proboscidea

         There are two living species in this order, the African elephant and the Indian elephant. These animals are the largest land animals alive today.

         An elephant’s upper incisor teeth are modified into long ivory tusks. 

 

 

 

 

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