Chapter 32 �Reptiles and Birds�

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Chapter 32 �Reptiles and Birds� Powered By Docstoc
					      Chapter 32
“Reptiles and Birds”


  Charles Page High School
     Stephen L. Cotton
   Section 32-1 Reptiles

OBJECTIVES:

 –Describe several
  characteristics of reptiles.
   Section 32-1 Reptiles

OBJECTIVES:

 –Explain  reasons for the
  great adaptive radiation of
  reptiles that occurred
  during the late Triassic
  and Jurassic periods.
   Section 32-1 Reptiles

OBJECTIVES:

 –Relate the form and
  function of reptiles to their
  success in dry
  environments.
     Section 32-1 Reptiles
Class Reptilia- includes
 snakes; lizards; tortoises;
 crocodile; etc.
  –there are 4 orders surviving;
   the 4th order is represented
   by a single species- the
   tuatara, a rare lizard that
   lives in New Zealand- page
   715 picture
  Section 32-1 Reptiles
Reptiles- vertebrate
animals with lungs; scaly
skin; a special type of egg
 –these are adaptations
  that enable them to live
  their entire life out of
  water
    Section 32-1 Reptiles
The   only places on Earth that
 lack reptiles are very cold areas
in some ways, reptiles resemble
 the amphibians; but reptiles are
 better adapted to life on land
  – skin is dry and leathery, often
    with scales to protect against
    water loss
    Section 32-1 Reptiles
However,    the dry waterproof skin
 can also be a disadvantage
  – it does not grow, and thus must
    be periodically shed
Reptile eggs are surrounded by a
 shell and several membranes
 that create a protected
 environment in which to develop
   Section 32-1 Reptiles
The  egg is named an “amniotic
egg” for one of the membranes
 – Figure 32-3, page 708
 – this amniotic eggs was as
   important to the survival of land
   animals as was the
   development of seeds for the
   survival of land plants
    Section 32-1 Reptiles
Amniotic   eggs also contain a
 substantial amount of yolk- rich
 in nutrients the embryo uses until
 it hatches
the legacy of an egg adapted to
 land was passed on from early
 reptiles to their descendants-
 modern reptiles, birds, mammals
   Section 32-1 Reptiles
Another    important reason for
 success of reptiles on land is the
 more efficient respiratory system
  – amphibians exchange gases
    primarily through moist skin;
    only works as long as it is moist
  – reptiles have 2 efficient lungs,
    or some snakes have 1 lung
   Section 32-1 Reptiles
Evolution   of Reptiles- several
 fossils show characteristics of
 both amphibians and reptiles;
 thus difficult to say when they
 first appeared
  – these forms often called
    transition forms- show slow and
    steady changes
   Section 32-1 Reptiles
During  the Carboniferous Period,
 amphibians outnumbered the
 reptiles; but during the Permian
 Period (began about 285 million
 years ago), the Earth began to
 change- cooler; less humid; great
 swamps dried up
began to favor land animals like
 reptiles, and less to favor
 amphibians
    Section 32-1 Reptiles
One early reptile line
 developed into mammal-like
 reptiles, very successful at first
  –became extinct in just a few
   million years
  –were replaced by another
   group of reptiles- the
   dinosaurs
   Section 32-1 Reptiles
During   the late Triassic and
 Jurassic periods, great adaptive
 radiations of the dinosaurs, or
 “terrible lizards” took place
  –during this time, there was
   also the appearance of
   crocodiles and alligators, as
   well as the first birds
      Section 32-1 Reptiles
At the end of the Cretaceous
 Period (65 million years ago),
 something happened to cause a
 worldwide mass extinction of
 dinosaurs, as well as many other
 animals and plants
What happened is not known for
 certain- possibly climate change;
 maybe a huge meteor struck
 earth creating huge dust clouds
    Section 32-1 Reptiles
For  whatever reason, it left many
 new niches open
  – new animals appeared on both
    the land and the sea
Reptiles have many variations-
 some move on legs (crocodiles,
 etc.), others without legs at all-
 snakes and certain lizards
   Section 32-1 Reptiles
Feeding-  remarkable diversity
 – some, such as iguana, are
   herbivores; other reptiles are
   carnivores- many snakes prey
   on small animals by grabbing
   them and swallowing whole;
   may live on birds eggs-
   swallowing and then cracking
    Section 32-1 Reptiles
Some    snakes, such as the king
 cobra, eat other snakes
Crocodiles and alligators eat fish
 and land animals, if they catch
 them
  – often store the remains under
    rocks, and return later when
    they get hungry
    Section 32-1 Reptiles
Monitor  lizards kill their prey with
 sharp teeth and powerful jaws
Chameleons have sticky tongues
Iguanas tear plant material into
 shreds with their teeth
  – since herbivorous reptiles do
    not chew, they swallow large
    pieces- thus long intestines are
    necessary to digest it
   Section 32-1 Reptiles
Respiration-   lungs of reptiles are
 better developed than those of
 amphibians
  – have muscles around their ribs,
    and many can expand their
    chest cavities
  – most have 2 lungs, but some
    snakes only have 1 lung
   Section 32-1 Reptiles
The  single lung of a snake fits
neatly into their long, thin body
 –another adaptation of snakes
  is the ability to breathe at the
  same time they are swallowing
  their prey: a special tube in the
  floor of the mouth; can be
  extended out of the mouth
     Section 32-1 Reptiles
Internal  Transport- well developed
 double-loop circulatory system
  – reptile hearts contain two atria,
    and either one or two ventricles
  – crocodiles and alligators have
    the most well developed heart,
    with 2 atria and 2 ventricles
  – four chambered heart also found
    in birds and mammals
    Section 32-1 Reptiles
Most reptiles with a single
 ventricle have a partial internal
 wall that help keep oxygenated
 and deoxygenated blood
 separate
circulatory system of the
 reptiles is more well-developed
 than the amphibians
   Section 32-1 Reptiles
Since  amphibians can exchange
 gases through their skin, they do
 not need an efficient circulatory
 system to deliver gases
In reptiles, however, the
 development of efficient lungs
 necessitated the development of
 a more efficient circulatory
 system
    Section 32-1 Reptiles
Excretion-  eliminate wastes in
 the form of urine produced by the
 kidneys
  – in many, the urine is expelled
    from the cloaca; others have a
    urinary bladder for storage
  – many desert reptiles remove a
    large amount of water from the
    urine and return it to the tissues
   Section 32-1 Reptiles
The  nitrogen-containing waste is
in the form of uric acid rather
than ammonia
 – ammonia requires a large
   amount of water, and is quite
   poisonous
 – uric acid is less toxic, and
   exists as crystals that requires
   less water
  Section 32-1 Reptiles
Thus, the urine is more of
a pasty material that can
be excreted without much
water loss
–another successful
 adaptation of reptiles to a
 land environment
    Section 32-1 Reptiles
Response- same basic pattern
 as the amphibian brain,
 although the cerebrum and
 cerebellum are somewhat
 larger
the sense organs are well
 developed, although there are
 exceptions: snakes cannot
 hear
    Section 32-1 Reptiles
Reptiles  that are active in the day
 have complex eyes and
 photoreceptor cells to detect
 colors quite well
snakes have a good sense of
 smell- nostrils open near the
 mouth; organs in roof of mouth
 that aid the nose
snakes flick tongue in and out?
   Section 32-1 Reptiles
Many   reptiles, including lizards,
can hear, and have an eardrum
 – many lack the eardrum, and
   are completely deaf to sounds
   carried in the air
 – snakes are able to pick up
   vibrations in the ground
   through bones in their skull
  Section 32-1 Reptiles
Some    reptiles can gather heat
information from the environment
 – pit vipers have heat-sensitive
   pits on both sides of their head;
   using these, vipers get a picture
   of the world around them as
   mammals stand out as warm
   spots
 – this is what they strike at; a
   valuable skill at night
   Section 32-1 Reptiles
Movement-     reptilian muscle and
 skeletal system exhibit many
 advances over the amphibians
  – reptiles with legs are larger,
    stronger with well controlled
    movements
  – snakes have lost their legs
    during evolution; move in
    waves by using ventral scales
    Section 32-1 Reptiles
Snakes    are thus very quiet, and
 masters at stalking prey
Reproduction- the reptile egg is
 an important contributing factor
 to the success of these animals
 in a land environment
  – it has a leather outer shell to
    protect the delicate tissues,
    and pores that allow gases to
    pass through
    Section 32-1 Reptiles
Reptiles    lay eggs that hatch into
 animals that resemble small
 adults
  – most have internal fertilization;
    the male depositing sperm inside
    the female body
  – the reproductive systems open to
    the outside through the cloaca; it
    is difficult to tell male from female
   Section 32-1 Reptiles
Once  fertilization has occurs,
reptile species treat their eggs
very differently
 – some are oviparous, providing
   no care at all- sea turtles lay
   eggs in sand, then leave
 – others provide minimal care;
   some snakes warm in the sun,
   and then wrap around the eggs
    Section 32-1 Reptiles
Alligators build nests in which
 they lay their eggs and guard
 them until they hatch; some
 additional care is then also given,
 such as carrying them to water;
 they may stay with the mother for
 as long as 2 years after they
 hatch! Figure 32-12, page 715
    Section 32-1 Reptiles
 **Tuataras- the only surviving
 member of order Rhynchocephalia
 – resembles reptiles that lived during
   the dinosaur age
 – Figure 32-12, page 715 bottom
 – of interest to paleontologists
   because it retains features of the
   ancient reptiles from which it
   evolved
  Section 32-1 Reptiles
Tuataras  are found only
on a few small islands off
the coast of New Zealand
 –unlike many reptiles,
  they are active at night,
  hunting the small
  animals they eat
   Section 32-1 Reptiles
Lizards   and Snakes- belong to
 the order Squamata
  – most lizards have legs, clawed
    toes, external ears, and
    movable eyelids
  – lizards range in size from
    geckos a few cm long to giant
    monitor lizards that can be
    more than 3 meters in length
   Section 32-1 Reptiles
Some   lizards are high specialized
 – page 710 - the African
   chameleons live exclusively in
   trees and bushes, eating
   insects they catch with an
   incredibly long coiled tongue
 – page 713 - gila monsters (large
   and stocky) have venom in their
   jaws to paralyze small prey
    Section 32-1 Reptiles
Gila monsters do not inject
 the venom with fangs-
 instead, they bite their prey
 and hold onto it with their
 teeth while the venom flows
 into the wound
The iguana looks ferocious,
 but is actually an herbivore
   Section 32-1 Reptiles
The   world’s largest living lizards,
 the monitors, provide some idea
 of what small dinosaurs may have
 been like
  – quite intelligent and active
  – many eat birds and mammals
  – the largest monitors are the
    Komodo dragons
    Section 32-1 Reptiles
Komodo    dragons can be up to 3
 meters long and weigh 75 kg;
 they can kill and devour animals
 as large as water buffalo
Snakes are lizards that have lost
 both pairs of legs during
 evolution
  – may have allowed them to
    burrow more efficiently
    Section 32-1 Reptiles
Although being legless may
 seem to be a disadvantage,
 snakes are efficient and
 effective predators in the niches
 they occupy
  –snakes vary in size- some as
   small as earthworms, others
   approaching 10 meters
   Section 32-1 Reptiles
Many    snakes are venomous-
 inject poison into their prey
  – actually, more people in the
    United States die from bee
    stings than snake bites
Crocodilians- members of the
 order Crocodilia are alligators,
 crocodiles, caimans, and gavials
have a 4-chambered heart
    Section 32-1 Reptiles
Alligators   and crocodiles have
 changed little in the last 200
 million years
  – the crocodilians are among the
    largest living reptiles, some
    species growing up to 7 meters
    in length
  – live in the tropics and
    subtropics; warm all year long
   Section 32-1 Reptiles
Alligators and their
 relatives the caimans, live
 only in fresh water, and are
 found almost exclusively in
 the Western Hemisphere
  –have a broader snout; few
   teeth visible when mouth
   closed
    Section 32-1 Reptiles
Crocodiles, on the other
 hand, may live in either fresh
 or salt water; are native to
 Africa, India, and Southeast
 Asia
  –are more aggressive; have
   pointed snouts; a
   characteristic “toothy” grin
   Section 32-1 Reptiles
Turtles   and tortoises- members
 of the order Chelonia, have also
 changed very little
  – turtle normally refers to those
    that live in water; tortoise to
    those that live on land
  – all have some sort of shell
    covering their body; in some,
    the shell is not very bony
   Section 32-1 Reptiles
The  turtle shell consists of
 2 parts:
  –a dorsal part, or carapace
  –a ventral part, or plastron
the animal’s backbone is
 fused to the inside of the
 carapace
    Section 32-1 Reptiles
Tortoises   usually have a high,
 domed carapace, and stubby
 elephant-like legs
  – they pull into their shells to
    protect their more delicate body
    parts
Turtles are adapted to life in
 freshwater ponds and lakes; legs
 and feet developed into flippers
   Section 32-1 Reptiles
How   Reptiles Fit Into the World
 – the reptiles alive today
   represent only a few survivors
   of a group of animals that once
   ruled the land
 – important predators in many
   ecosystems- snakes eat rats;
   lizards eat insects; large lizards
   eat other small animals
   Section 32-1 Reptiles
Sea  turtles, which were once
very numerous in both the
Atlantic and Pacific oceans, are
now in danger of becoming
extinct
 – turtle soup; turtle eggs; tortoise
   shell for jewelry; destruction of
   their nesting sites for houses,
   hotels, etc.
Section 32-2 The Evolution
  of Temperature Control
OBJECTIVES:

 –Defineectothermic and
  endothermic.
Section 32-2 The Evolution
  of Temperature Control
OBJECTIVES:

 –Compare    ectothermic and
  endothermic strategies for
  surviving in different
  environments.
 Section 32-2 The Evolution
   of Temperature Control
Control of body temperature
 is important for animals,
 particularly in habitats where
 temperature varies widely with
 time of day and season
  –most animal species have a
   preferred “operating range”
 Section 32-2 The Evolution
   of Temperature Control
In terms of how they generate
 and control their body heat,
 animals can be classified into
 two basic groups:
  –ectotherms and endotherms
Turtles, snakes, and other
 modern reptiles are ectotherms
Section 32-2 The Evolution
  of Temperature Control
Ectotherms     literally means heat
 from outside- as a group, these
 animals have relatively low
 metabolic rates when resting
  – do not generate much heat
    inside their bodies; lack any
    effective insulation, so any heat
    they have is lost
Section 32-2 The Evolution
  of Temperature Control
Birds   and mammals are
 classified as endotherms, which
 literally means heat from inside
   – usually have relatively high
     metabolic rates that generate a
     significant amount of heat even
     when resting; move easily at
     night and during cool times
Section 32-2 The Evolution
  of Temperature Control
Ectothermic   animals are often
 incorrectly thought of as “cold-
 blooded”, and endothermic
 animals as “warm-blooded”
  – Cold-blooded animals may
    have a body temperature
    higher than their surroundings,
    whereas warm-blooded may be
    cooler than the surroundings
Section 32-2 The Evolution
  of Temperature Control
In  nature, lizards and
 snakes warm up when they
 need to by basking in the
 sun
  –if they get too hot, they
   duck into a cool burrow or
   under a rock to lose heat
 Section 32-2 The Evolution
   of Temperature Control
Neither endothermy nor
 ectothermy is superior to the
 other
  –for different animals in
   different environments, each
   strategy has its advantages
   and disadvantages
Section 32-2 The Evolution
  of Temperature Control
For  example, ectotherms cannot
 remain active for long periods of
 time; endotherms remain active
 for a long time
In climates that remain warm all
 the time, ectothermy is a way of
 conserving energy- the reason
 many are found in tropical areas
 Section 32-2 The Evolution
   of Temperature Control
Endotherms,    on the other hand,
 burn a lot of calories to generate
 body heat- thus they need more
 food compared to ectotherms of
 the same size
Large ectotherms run into
 problems in temperature zones
 where temperature varies a lot
Section 32-2 The Evolution
  of Temperature Control
Ittakes a long time for a
 large animal to warm up in
 the sun after a cold night
  –also difficult for a large
   animal to find shelter
   during a scorching hot
   day
 Section 32-2 The Evolution
   of Temperature Control
But  even small ectotherms
 cannot cope with long cold,
 cloudy winters
  – they either hibernate or lay
    resting eggs and die
There is little doubt that the first
 terrestrial vertebrates were
 ectotherms
    Section 32-3     Birds

OBJECTIVES:

 –Identify   characteristics of
  birds.
    Section 32-3   Birds

OBJECTIVES:

 –Describe    ways the form of
  birds shows adaptations
  for flight.
    Section 32-3   Birds

OBJECTIVES:

 –Explain how birds fit into
  the natural world.
      Section 32-3 Birds
There are many birds: about
 8700 living species, and there
 were even more kinds of birds
 in the past
  –estimates are that more than
   100,000 species of birds have
   become extinct since the
   Jurassic Period
     Section 32-3      Birds
Birds-  characteristics:
1) endothermic reptile-like animals
2) outer covering of feathers
3) two legs used for walking or
 perching
4) front limbs modified into wings
 that usually
5) do not have useful claws
       Section 32-3    Birds
The   single most important
characteristic that separates
birds from reptiles is: feathers
 – these help birds fly, and also
   keep them warm
 – there are also many different
   types of feathers, used for a
   different purpose
     Section 32-3        Birds
Contour     feathers- large feathers
 that cover a bird’s body and
 wings (general body feathers)
  – certain contour feathers, called
    flight feathers, are long and stiff
  – from both sides grow barbs,
    and then still smaller structures
    called barbules
       Section 32-3    Birds
The  hooks on a barbule catch on
the hooks of nearby barbules,
holding the barbs together in flat
vanes Figure 32-22, p.724
 – these are easily lined up if they
   separate by pulling them
   through the beak- called
   “preening”
    Section 32-3     Birds
Down   feathers- grow underneath
and between the contour
feathers
 – short, soft, and fluffy
 – insulate the bird
 – baby birds of many species are
   covered with down feathers for
   a period after they hatch
     Section 32-3        Birds
Powder     feathers- important to
 birds that live on or in water
  – they release a fine white
    powder that repels water, and
    keeps it from penetrating the
    layer of down feathers
  – birds also produce a waterproof
    oil in special glands near the tail
     Section 32-3        Birds
When     preening, this oil is rubbed
 over their feathers
  – literally makes water “roll off a
    duck’s back”
Evolution of Birds- many
 paleontologists describe birds as
 “a hot-blooded dinosaur with
 feathers”
       Section 32-3    Birds
The   first fossil ever found of an
early birdlike animal is called
Archaeopteryx, and dates from
late in the Jurassic Period
 – it had teeth in it’s beak, and
   toes and claws on it’s wings
 – except for feathers, it probably
   would be classed as a dinosaur
    Section 32-3      Birds
More  recently, another
transitional fossil- with both
dinosaur and bird features- has
been found
 – called Protoavis, is older than
   Archaeopteryx
 – seems to confirm that birds are
   related to dinosaurs
     Section 32-3       Birds
Birds  have many differences in
 their structures: such as feathers,
 wings, bones, beaks, and legs
  – thus, they are adapted to many
    ways of life in different habitats
Feeding- ever heard the phrase
 “eat like a bird”? Nothing is
 further from the truth!
    Section 32-3     Birds
Birds  have high metabolic rates
 and burn many calories just to
 keep warm
  – thus, they need to eat large
    amounts of food
  – may be captured by hawks and
    eagles in razor sharp talons,
    and slice with a beak
     Section 32-3       Birds
Insect-eating  birds may pick
 insects off leaves and branches,
 or catching them on the fly
  – may also drill into wood to pull
    out the insects that live there
  – there are also pollen and
    nectar feeders such as
    hummingbirds
     Section 32-3       Birds
Fruit-eating and seed-eating
 birds may have short, stout
 beaks or long, sharp ones
Filter feeders such as ducks and
 flamingoes have broad beaks
 with strainers built in the upper
 and side parts of the bill- may sift
 out plankton from murky waters
       Section 32-3   Birds
The  digestive system of birds,
much like reptiles, shows
specialization for herbivores and
carnivores
 – many have organs called the
   crop and gizzard
 – the crop is an enlarged
   esophagus for food storage
       Section 32-3   Birds
The  food is also moistened in the
crop before it goes to the
stomach
 – in some species, the crop
   stores food that is later
   regurgitated for feeding to a
   bird’s young; in others it
   produces food fed to the young
       Section 32-3    Birds
The   gizzard is a specialized
 muscular part of the stomach
 that often contains small bits of
 gravel swallowed by a bird
  – the muscular walls grind the
    gravel and food together
both the crop and gizzard are
 highly developed in seed-eaters
     Section 32-3        Birds
Respiration-    extremely efficient in
 taking in oxygen and eliminating
 carbon dioxide
  – the reason for this efficiency is
    that bird lungs are connected at
    both the anterior and posterior
    to large air sacs in the body
    cavity and bones
     Section 32-3 Birds
When inhaling, some air travels
 through passages that lead to
 the lungs; some remain in the
 lungs where gas exchange
 occurs
 most of it, however, goes
 through the lungs into the
 posterior air sacs
    Section 32-3       Birds
When   a bird exhales, air from the
posterior air sacs passes into the
lungs for gas exchange
 – thus, birds are able to remove
   oxygen from the air when they
   inhale as well as exhale
 – air sacs also make the bird
   more buoyant, flying easily
     Section 32-3     Birds
Internal Transport- have a four
 chambered heart; two separate
 circulatory loops
  – one half of the heart receives
    oxygen-poor blood from the
    body and pumps it to the lungs
  – one half of the heart receives
    oxygen-rich blood from the
    lungs and pumps to the body
     Section 32-3 Birds
To keep blood moving rapidly,
 a bird’s heart beats quickly-
 from 150 or more than 1,000
 beats per minute
  –a student’s heart = 85/min.
Excretion: kidneys filter the
 blood to eliminate nitrogenous
 wastes
     Section 32-3      Birds
Urine,  which contains the waste
 uric acid, flows to the cloaca
 through the ureters
  – most water reabsorbed here,
    leaving uric acid crystals in a
    white paste-like form
  – these are the familiar “bird
    droppings”
     Section 32-3       Birds
Birds  that live around salt water
 also have evolved special salt
 glands near their eyes
  – these salt glands work like an
    extra pair of kidneys, except
    they specialize in excreting salt
Response- despite the term “bird
 brain”, birds are quite intelligent
     Section 32-3      Birds
Cerebrum    is quite large (for
 flying, nest building, care of
 young, courtship, mating)
Cerebellum also well-developed
 for precise coordinated
 movement
extraordinarily well-developed
 eyes; large optic lobes; see color
 very well
     Section 32-3    Birds
Predatory   birds such as hawks
 can spot mice on the ground with
 sight far keener than ours
The senses of taste and smell,
 however, are not well-developed;
 the olfactory lobes of the brain
 are quite small
Lack external ears, just ear
 openings; hear quite well
     Section 32-3    Birds
Owls  can so accurately hear
 mice crawling through dead
 leaves that they can swoop down
 and catch them in darkness
Some migratory birds use a
 magnetic sense to navigate; this
 is located somewhere in their
 head
     Section 32-3     Birds
Movement-    able to move through
 different environments with
 wings, bodies, legs, and feet
 adapted for various types of
 locomotion
  – may soar like eagles; flap
    wings steadily like robins, or
    hover in place like
    hummingbirds
    Section 32-3      Birds
Many   of the large bones are
hollow- but not weak; they are
strengthened by internal struts
similar to tall buildings and
bridges
 – the air sacs extend into certain
   bones, making them lighter; the
   air sacs also seem to cool the
   body from heat of flight
     Section 32-3     Birds
Other    adaptations to decrease
 weight for flight?
   – Shrinking of sex organs during
     the time they are not breeding
To provide power, there are large
 chest muscles- in strong fliers
 like pigeons, the chest muscles
 may be 30% of the animal mass
     Section 32-3        Birds
Many    birds use their flying ability
 to migrate to more favorable
 living conditions
Some birds have even lost the
 ability to fly- ostriches spend their
 time walking or running; thus
 they can be quite large since
 there is no need to reduce their
 mass for flight
     Section 32-3      Birds

Other   birds have given up flight
 for swimming
  – penguins are a familiar
    example; wings, legs, and feet
    are reduced in size- but make
    them powerful flippers that
    enable them to “fly” through the
    water
    Section 32-3        Birds

Reproduction-    similar to reptiles
 – reproductive tracts open to the
   cloaca
 – in females, only one side of the
   reproductive tract develops,
   apparently to minimize body
   weight for flight
     Section 32-3       Birds
Male   birds have no external
 reproductive organs
  – mating birds press their
    cloacas close together: transfer
    sperm from male to female
  – eggs do have a shell, but the
    internal parts are similar to the
    reptiles; birds incubate the
    eggs until they hatch
       Section 32-3   Birds
The   time of incubation varies-
chickens is usually about 20-22
days
 – until they hatch, they use
   nutrients in the egg’s yolk
 – when a chick is ready to hatch,
   it uses a small “egg tooth” on
   it’s bill to make a hole in the
   shell
    Section 32-3      Birds
Some    birds, such as chickens
and ducks, are able to take care
of themselves as soon as they
hatch
 – others, such as robins and
   sparrows, are blind and totally
   helpless when they hatch- for
   days or weeks they sit with
   their mouth open, screaming
   for food: Figure 32-31, p.731
     Section 32-3        Birds
Birds   have fascinating courtship
 and mating behaviors
  – some species, such as swans,
    mate for life; others pair up only
    briefly to mate
  – in peacocks, the male uses
    brightly colored feathers to
    attract females and warn off
    other males during breeding
     Section 32-3      Birds
Male    canaries and similar
 species “sing” to attract females
 and keep other males out of their
 territory
How Birds Fit Into the World-
  – it would be pretty dull walking
    in the country without birds in
    the woods chirping and singing
    Section 32-3     Birds
– Birds  are admired for their
  beauty and powers of flight
– have an evolutionary
  relationship with flowering
  plants; hummingbirds serve as
  pollinators; fruit-eating birds
  disperse plant seeds
– birds eat extraordinary
  numbers of insects
   Section 32-3       Birds
– Humans    use down feathers for
  insulation
– birds are favorite foods; raising
  them in part of the economy
– with the low fat content, bird
  meat is a healthful source of
  protein in a balanced human
  diet; non-flying birds, like
  turkey, have tender chest meat

				
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