18A Endotherms and
Ectotherms
 18A.1 Endotherms
 Mammals and birds are the only endothermic animals
 This means that they have the ability to maintain a
relatively constant body temperature
 Endothermic animals have various ways of keeping
their body temperatures from falling below proper
range
 Some have heavy fur or thick layers of feathers to
insulate their bodies
 Others have small ears to prevent heat from escaping
18A Endotherms and
Ectotherms
 18A.1 Endotherms
 When endotherms become too hot, blood vessels in
their skin expand. This allows warm blood to flow near
the surface of the skin where it is cooled
 Some mammals secrete sweat, and as it evaporates, it
cools the skin and the blood
 Others have large ears (like rabbits) where large
amounts of blood can be pumped for cooling
 Lining of dog’s mouth and throat contain many blood
vessels to help cool the blood – hence the reason dog’s
pant – to keep them cool!
18A Endotherms and
Ectotherms
 18A.2 Ectotherms
 Ectotherms include fish, amphibians, reptiles, worms,
arthropods, and several other groups
 Ectotherms cannot control their own body
temperatures; it is often the same as their
surroundings
 They must adjust their activities when their bodies get
too hot or too cold
 The advantage of being endothermic: the animal can
be active regardless of temperature of the
environment
18A Endotherms and
Ectotherms
 18A.2 Ectotherms
 However, they must eat more food to supply the
energy required to maintain their temperature
 For example, snakes are often sluggish after a cool
night and during the hot summer, will hide under rocks
to stay cool
 Learning about how snakes and other ectotherms
function allows people to help others in specific ways.
 Some medicine companies chill poisonous snakes in
large refrigerators in order to make snakes sluggish so
that they can extract venom used to make substances
for treating snakebites that might otherwise be fatal
18A Endotherms and
Ectotherms
 18A.2 Ectotherms
 Butterflies “warm up” their wings in order to warm
their bodies enough to fly (in the morning)
 Earthworms only come out of burrows in the cool of
the evening and at night
 Ponds in the morning, have you ever noticed a large
number of frogs (or at night), but wonder where they
went during the day – its too hot during the day for
them!
18A Endotherms and
Ectotherms
 Answer Section review questions 18A on the left
hand side of your notebook
 Then work on Ideas 18A
18B Birds
 Birds are endothermic vertebrates that have wings and
feathers
 They are found on every continent
 Their ability to survive in extreme environments is
largely due to God’s provision of giving them the ability
to fly
 Birds eat a variety of foods including: nectar, seeds,
fruit, worms, insects, fish, mice, and even other birds
 Birds DO NOT have teeth
 They have beaks and feet designed to help them catch
and eat their food
18B Birds
 Meat-eating birds have sharp, hooked beaks used to
tear meat
 Seed-eating birds have short, thick beaks that easily
crack hard seeds
 Turn to page 322. Look at Figure 18B-1 – Take a
moment to match the beak with the foot it belongs to
 Birds benefit man by helping to control rodent and
insect pests and providing meat and eggs
18B Birds
 18B.1 Designed for Flight
 It takes more than wings and feathers for birds to fly
 God did make some birds that CANNOT fly
 Penguins, for example, use their wings as fins to help
them swim; Ostriches use their wings for balance when
they run
 Ostriches have powerful legs, making them the one of the
fastest animals on earth
 Low body weight is essential in flying
 Bird bones are relatively lightweight; they also have air
spaces in them and are reinforced by a crisscross
structure inside them
18B Birds
 18B.2 Fuel for Flight
 Since birds are endothermic, they need more food than
other ectotherms their size
 Flight muscles require lots of energy
 During flight, much oxygen and many food molecules
must be made quickly
 Birds store energy rich molecules in their flight muscles,
so it is available for immediate use when they need it
 Birds get the energy they need by eating large amounts of
food; in fact many can eat more than their body weight!
 What does this mean? It would be like a 100lb middle
school student eating 48 large pepperoni pizzas daily!!
18B Birds
 18B.2 Fuel for Flight
 Birds in flight also require additional oxygen to support
cellular respiration of their flight muscles
 Air sacs connected to their lungs help supply additional
oxygen
 A bird’s lungs are supplied with oxygen-rich air even when
it is exhaling as a result of the movement of oxygen
 Air sacs are also the chief means a bird has of cooling its
body
 They allow more cool air to enter the body and more
warm air to leave than the lungs would permit
 The harder we work, the more oxygen we need; same is
true for birds
18B Birds
 18B.3 Nests and Eggs
 A characteristic of all birds – they lay eggs
 A fertile bird egg consists of an embryo, a yolk (food
supply), albumen (egg white – liquid environment), a shell
membrane, and a brittle shell
 An egg provides the food and environment necessary for
the embryo to develop
 Also, gases involved in cellular respiration (oxygen and
carbon) can pass through the brittle shell and shell
membrane
18B Birds
 18B.3 Nests and Eggs
 Birds care for their eggs by building a nest and incubating
the eggs
 Nests may be made of twigs, grass, spider webs, stones,
or various other materials built just about anywhere
 Parent birds warm their eggs by sitting on them, but that
is not all there is to incubation
 The contents of the egg, especially the yolk, must remain
free of any permanent contact with the eggshell
 Yolk floats on top of the albumen (white)
 If the egg is not moved, the embryo will not develop
normally
 Parents must regularly turn their eggs to ensure normal
development
18B Birds
 18B.3 Nests and Eggs
 Some birds, such as turkeys, chickens, geese, and quail
hatch fully-feathered and are able to walk and peck for
their own food
 Many of these birds nest on the ground
 Most though, are blind, nearly naked, and helpless at
birth
 These birds usually hatch in nests or tree cavities where
the parents can protect them
18C Mammals
 Mammals are the most familiar vertebrates to us
 They provide food, labor, companionship, and even
entertainment
 Mammals show remarkable diversity in size, form, and
behavior
 18C.1 Characteristics of Mammals
 Mammals are endothermic vertebrates that have hair and
produce milk
 The amount of hair ranges from a little to a lot
 Those that have a lot of hair, is typically thick, which is
called fur
 Some hair is sensitive to touch – example, a cat’s whiskers
18C Mammals
 18C.1 Characteristics of Mammals
 Mammals also have mammary glands – which produce
milk in the mother mammal, for their young
 Milk provides the fat, protein, carbohydrates, vitamins,
minerals, and water that an infant mammal needs
 Some infants only drink their mother’s milk for a few
weeks, while others continue for several months
 As offspring grow, they receive nourishment from their
mother as well as learn survival skills
 As mammals mature, they begin to eat the same foods as
their parents
 They develop teeth to help them eat their food
18C Mammals
 18C.1 Characteristics of Mammals
 Mammals have four kinds of teeth:
 Incisors – used for cuttung
 Canines – long and pointed, used for tearing
 Premolars and molars are used for grinding
 However, some may be lacking one or more types of
teeth depending on their diet
18C Mammals
 18C.2 Groups of Mammals
 Mammals can be divided into three groups based on
how they reproduce:
 Placental, Monotremes, and marsupials
 Placental Mammals –
 Mammals such as dogs, horses, deer, and whales are
examples
 Placenta – the structure through which mammals receive
oxygen and food and have wastes removed while they are
growing inside their mothers
 Developing mammals are connected to the placenta by an
umbilical cord.
18C Mammals
 18C.2 Groups of Mammals
 The umbilical cord contains blood vessels that transport oxygen,
food, and wastes between the placenta and the developing
mammal
 The cord attaches to the mammal and leaves a mark called an
umbilicus, or bellybutton.
 Placental mammals are born alive; they do not hatch from eggs
or develop in pouches
 Monotremes – mammals that lay eggs
 Duckbilled platypus and echidna are the only montremes
18C Mammals
 18C.2 Groups of Mammals
 Marsupials – they have a pouch in which they
rear their young, but they are not born in the
pouch
 Newborn marsupials, which are not well
developed, crawl from the birth canal into
their mother’s pouch immediately after birth
 Once in the pouch, they complete their
development
 Examples: Kangaroo, opossums
 In Australia and surrounding regions, are the
habitat of a wide range of marsupials –
marsupial versions of mice, moles, rabbits,
flying squirrels, weasels, and more.
18C Mammals
 Go to page 329 and Using Table 18C-4, decide which order each of
these placental mammals belongs to and write their order name
under the picture