Biology - Chapter 33

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Biology - Chapter 33Mammals

• Charles Page High School
• Stephen L. Cotton

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Section 33-1 Mammals

• OBJECTIVES
• Describe the characteristics of mammals.

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Section 33-1 Mammals

• OBJECTIVES
• Discuss the importance of endothermy in the
  evolution of mammals.

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Section 33-1 Mammals

• The animals known as mammals vary greatly in
  appearance
• from a tiny mouse to a huge elephant
• flying in the air running along the ground
  swimming in the sea
• but, Class Mammalia does have certain
  characteristics

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Section 33-1 Mammals

• Mammals are
• endothermic animals (generate body heat
  internally)
• experts at maintaining a constant body
  temperature, because of subcutaneous fat
• also have sweat glands to help cool the body as
  it evaporates

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Section 33-1 Mammals

• Most mammals are viviparous- develop inside the
  mother for a time, and are then born alive
  however, a very few primitive varieties lay eggs
  (oviparous)
• female mammals have mammary glands which produce
  milk for the young
• have hair or fur at some time

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Section 33-1 Mammals

• Mammals have several kinds of teeth that either
  bite, chew, or grind food with efficient jaws
• scientists use the teeth of a mammal to classify
  it into the different mammalian orders
• Have well-developed breathing muscles, including
  a diaphragm that separates chest abdomen

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Section 33-1 Mammals

• A 4-chambered heart, consisting of 2 atria and 2
  ventricles, and a double loop circuit
• one circuit moves blood to and from the lungs
• the other circuit moves blood to and from cells
  in the rest of the body

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Section 33-1 Mammals

• Evolution of Mammals- the first mammals were
  small and probably resembled species of the tree
  shrews alive today
• Figure 33-4, page 739
• probably nocturnal, active mainly at night
  because they were endotherms

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Section 33-1 Mammals

• By the end of the Cretaceous Period, mammals had
  split into three groups
• 1. Order Monotremata- called monotremes most
  primitive 6 species alive today examples are
  the duckbill platypus spiny anteater

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Section 33-1 Mammals

• 2. Order Marsupalia- the marsupials
• includes opossums, kangaroos, wombats, and koalas
• each of these species has a pouch (marsupium) in
  which its young live for a time to complete
  their development

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Section 33-1 Mammals

• 3. Placentals- composed of 16 orders
• includes the mammals we are most familiar with,
  such as mice cats whales elephants and humans
• hard to say exactly when each of these 3 groups
  appeared

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Section 33-1 Mammals

• We do know that the placental mammals experienced
  adaptive radiation in North America and Europe
• Marsupials experienced adaptive radiation in
  Australia, South America, and Antarctica (which
  was a good deal warmer then than it is today)

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Section 33-1 Mammals

• Feeding- carnivorous mammals, such as cats and
  dogs, developed strong, sharp incisors and
  canines that are used for biting and ripping
  flesh use an up and down motion of the jaws
• may also have sharp claws to grab prey bodies
  built for bursts of speed to chase prey

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Section 33-1 Mammals

• Herbivorous mammals, from cows to giraffes, eat
  plants that require thorough chewing
• have evolved strong lips and flat-edged incisors
  that grasp and tear this tough vegetation
• move their jaws side to side
• However, it is still difficult to digest the
  plant cellulose

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Section 33-1 Mammals

• Many grazing animals (called ruminants) have a
  chamber in their digestive tract called the
  rumen, in which newly swallowed plant food is
  stored and processed for a time
• the rumen contains thriving colonies of symbiotic
  bacteria that produce enzymes

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Section 33-1 Mammals

• After a time, the animal can then regurgitate the
  plant food from the rumen into its mouth
• described as chewing their cud
• the second time food is swallowed, it moves
  through the rest of the digestive system to
  complete digestion

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Section 33-1 Mammals

• Herbivores such as rabbits lack a rumen, but have
  a large dead-end sac called the cecum
• contains some of the same types of bacteria that
  produce the digestive enzymes
• ancestors of humans had a cecum, but is now
  shrunk into our appendix

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Section 33-1 Mammals

• Other mammals may drink blood, such as vampire
  bats
• a chemical in saliva keeps the blood from
  clotting
• Filter feeders- such as the giant blue whale- the
  teeth are modified into huge stiffened plates
  called baleen, which act like giant filters

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Section 33-1 Mammals

• Respiration- all mammals, even sea mammals, use
  lungs powered by two sets of muscles
• 1. Chest muscles move ribs
• 2. Diaphragm pulls downward to increase size of
  chest cavity and draw air in
• many mammals use exhaled air over the vocal cords
  for sound

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Section 33-1 Mammals

• Internal Transport- 4-chambered heart pumps
  deoxygenated blood to the lungs, and after
  returning to the heart it pumps oxygenated blood
  to the body tissues
• two circuits, one to lungs and the other to the
  body, efficiently transport gases and nutrients

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Section 33-1 Mammals

• Excretion- most highly developed kidneys of all
  vertebrates
• kidneys also control the composition of body
  fluids
• extract nitrogenous wastes from blood as urea
• urea water excess salts urine flows
  through the ureters to the urinary bladder to
  store

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Section 33-1 Mammals

• Response- most highly developed brains of any
  animals
• three parts of the brain
• 1. Cerebrum- thinking, learning
• 2. Cerebellum- coordination
• 3. Medulla- regulate body functions such as
  breathing and heart rate

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Section 33-1 Mammals

• Mammals depend on highly developed senses- well
  developed sight, hearing, smell
• most mammals do not see color well- except for
  apes, monkeys, and humans
• probably because the first mammals were nocturnal
• human ears not real sensitive

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Section 33-1 Mammals

• Dogs and bats hearing is great
• human taste and smell is also not highly
  developed
• Mammals depend on complex behavior for protection
• herbivores able to run horns or hooves for
  defense band together into groups for protection

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Section 33-1 Mammals

• Movement- four limbs inherited from their
  ancestors
• running mammals such as horses attain great
  speeds
• climbing mammals such as monkeys prehensile tail
• flying mammals bats
• aquatic mammals like dolphins

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Section 33-1 Mammals

• Reproduction- the 3 groups of mammals vary
  greatly in their methods of reproduction
• oviparous monotremes but still provide milk for
  nourishment
• marsupials have limited yolk sac, so they are
  born early and crawl into a pouch (marsupium) to
  obtain the milk

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Section 33-1 Mammals

• In placental embryos, the egg membranes develop
  into tissues called the umbilical cord, which
  join with the mothers tissues at the placenta
• the placenta allows the embryo to develop for a
  much longer time inside the mother
• time is called gestation period

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Section 33-2 Important Orders of Living Mammals

• OBJECTIVES
• Compare methods of mammalian reproduction.

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Section 33-2 Important Orders of Living Mammals

• OBJECTIVES
• Identify the most important orders of placental
  mammals.

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Section 33-2 Important Orders of Living Mammals

• OBJECTIVES
• Recognize the importance of mammals in the world.

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Section 33-2 Important Orders of Living Mammals

• Scientists use several traits to classify the
  mammals
• structure of teeth
• number and kinds of bones in the head
• most important characteristic is the type of
  reproduction- we already learned the 3 types

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Section 33-2 Important Orders of Living Mammals

• Order Monotremata- the monotremes are egg-laying
  mammals, and are very rare
• found in isolated parts of Australia and New
  Guinea
• examples are the duckbill platypus (p.743) and
  spiny anteater (or echidna- p.746)

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Section 33-2 Important Orders of Living Mammals

• Order Marsupalia- the pouched mammals such as
  kangaroos and koalas are found in Australia
• opossums are the only marsupials found in North
  America eat insects, birds
• newborn are about the size of a bee- crawl into
  the pouch

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Section 33-2 Important Orders of Living Mammals

• Living placental mammals are placed into 16
  orders we will study 12 of the most important
• in addition to having different reproductive
  habits, placental mammals have slightly higher
  metabolic rates
• more abundant than marsupials

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Section 33-2 Important Orders of Living Mammals

• 1. Order Insectivora- the name means
  insect-eater
• shrews, hedgehogs, moles
• extremely high metabolic rate eat almost
  constantly to stay alive
• biologists believe that the first mammals looked
  and behaved much like certain modern shrews

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Section 33-2 Important Orders of Living Mammals

• 2. Order Chiroptera- the different species of
  bats
• some eat only insects
• others eat only fruits
• some feed on blood of other mammals (vampire
  bats)
• echolocation-navigate at night

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Section 33-2 Important Orders of Living Mammals

• 3. Order Edentata- the name means without teeth
  even though some of them have teeth
• sloths (South American- slow moving, hang upside
  down), anteaters (long tongue, tapered snout
  powerful legs to rip open ant nests), and
  armadillos

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Section 33-2 Important Orders of Living Mammals

• 4. Order Rodentia- many amusing animals, and some
  quite destructive
• mice rats squirrels beavers porcupines, and
  gophers
• all have 2 long front teeth that continually
  grow, thus they wear them down by gnawing

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Section 33-2 Important Orders of Living Mammals

• Most rodents are small, and have a short
  gestation period
• rats and mice are adaptable animals that eat a
  wide variety of foods
• long ago, these rodents moved in with humans and
  have traveled with us the world over

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Trees damaged by beavers.
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Trees damaged by beavers.
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Section 33-2 Important Orders of Living Mammals

• 5. Order Lagomorpha- familiar rabbits and hares
• closely resemble rodents because they have sharp
  front teeth and eat plant material
• gestation period is short, and the number of
  offspring is high
• compete with us for food

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Section 33-2 Important Orders of Living Mammals

• 6. Order Carnivora- are meat eaters- dogs, cats,
  wolves, bears, weasels, hyenas, seals
• most are terrestrial, stalking and chasing their
  prey
• seals and walruses had at one time land
  ancestors, but have since returned to the ocean

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Section 33-2 Important Orders of Living Mammals

• 7. Order Cetacea- the truly aquatic mammals-
  whales, dolphins, and porpoises
• still breathe air- have lungs and a circulation
  designed to permit long, deep dives
• have a layer of subcutaneous fat (blubber) to
  keep warm

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Section 33-2 Important Orders of Living Mammals

• 8. Order Sirenia- strange aquatic animals related
  to elephants
• peaceful,slow-moving herbivores in rivers and
  streams of Africa, South America, and Florida
• the manatee (sea cow) is often injured by
  careless boaters

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Section 33-2 Important Orders of Living Mammals

• 9. Order Artiodactyla- large grazing animals
  cattle, sheep, goats, hippos, giraffes, pigs
• original 5 toes on each foot have been reduced to
  2
• called even-toed ungulates (hoofed mammals)

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Section 33-2 Important Orders of Living Mammals

• 10. Order Perissodactyla- horses, zebras, tapirs,
  and rhino
• these are the odd-toed ungulates
• contains many grazing animals with habits similar
  to those of the even-toed ungulates

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Section 33-2 Important Orders of Living Mammals

• 11. Order Proboscidea- mammals with trunks- the
  great elephants
• formerly included mammoths and mastodons
• today, 2 species the Indian elephant and African
  elephant, both in danger of extinction

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Section 33-2 Important Orders of Living Mammals

• 12. Order Primates- which includes our own
  species (humans), and is closely related to
  ancient insectivores
• most highly developed cerebrum, and most
  complicated behaviors

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Section 33-2 Important Orders of Living Mammals

• The most primitive living primates, the lemurs,
  are small tree dwellers two other main branches
  are monkeys and apes
• Very early in their evolutionary history,
  primates as a group were split apart by the
  moving continents

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Section 33-2 Important Orders of Living Mammals

• One branch, the New World monkeys, includes the
  squirrel monkey and spider monkey
• these live almost entirely in trees
• have long arms for swinging, and a long
  prehensile tail for grasping

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Section 33-2 Important Orders of Living Mammals

• The other branch, the Old World monkeys, include
  chimpanzees, gorillas, and the ancestors of
  humans
• many still spend much of their time in trees, but
  they all lack prehensile tails

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Section 33-2 Important Orders of Living Mammals

• How Mammals Fit Into the World
• evolved from early reptile ancestors during the
  Mesozoic Era about 200 million years ago
• herbivores are major plant consumers- grazing
  zebras, reindeer herds, oxen

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Section 33-2 Important Orders of Living Mammals

• The herbivores are food for the carnivores-
  lions leopards wild dogs wolves
• bats eat large numbers of mosquitoes
• squirrels eat nuts and seeds
• domesticated animals for work horses oxen mules

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Section 33-2 Important Orders of Living Mammals

• Many of these animals also provide food in the
  form of meat and dairy products
• dogs are used to hunt, helping humans find food
• But, some mammals have a negative impact on human
  life

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Section 33-2 Important Orders of Living Mammals

• Carnivores prey on domesticated animals
• rodents such as rats and mice damage crops, eat
  stored food
• some mammals carry diseases, such as rats that
  harbor fleas that spread the plague

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Section 33-2 Important Orders of Living Mammals

• Dogs, squirrels, other wild animals that transmit
  the virus for rabies
• elephants destroy trees as they feed
• overgrazing by cattle turns land into a dust
  bowl beavers flood areas
• Humans- good or bad influence?