FEEDBACK to BioTopics Next Unit?


Birds and mammals are two classes of vertebrates that are said to be warm blooded. They possess various mechanisms to ensure that their body temperature is fairly constant, (unaffected by, and usually warmer than, their surroundings), so that they can function more efficiently and reliably.


1) Body covered with feathers . Functions: PROTECTION of body, COLOURATION (either camouflage or flamboyant), INSULATION (very important in small birds) and sometimes for FLIGHT.

2) Females lay fairly large EGGS with a CHALKY external SHELL. FERTILISATION is INTERNAL, and shell is added later. Eggs are normally laid in a nest, and the eggs are looked after by male or female, or both birds. Eggs are incubated, i.e. kept at correct temperature and tended, e.g. turned at intervals. n.b. Flight would be difficult if females retained the heavy eggs inside the body.


- front limbs form wings

- breast bone has " keel " to which wing muscles are attached.

- bones are very light, having AIR SPACES

- lungs have extra air sacs (near main muscles) to increase capacity (maybe also cooling).

- STREAMLINED body shape - no external ears - some have bony plates in eyes to resist wind pressure

- FEATHERS are light yet form large surface area

4) Birds have no teeth, but a tough beak for pecking food, and a gizzard containing stones to grind up food. Beaks show modifications according to function.


6) Legs covered with scales ( a link with reptiles?). Usually each foot has 4 toes with claws, but flightless birds may have 3. Much adaptation according to lifestyle.

7) CLOACA - common opening of urinogenital and digestive tract, no external sexual organs.

8) COURTSHIP displays may be complex, Male is usually brightly coloured ( a risk which has evolutionary advantages?).

9) PARENTAL CARE of young is a notable feature, but much of BEHAVIOUR is instinctive .

By way of exceptions that prove the rule, list some examples of species of birds that are (naturally) unable to fly.

Use an encyclopedia or other reference book to find some examples of birds that have beaks and feet that are specially modified to suit their lifestyle. You should be easily able to find 4 examples of each. For each, give the name of the species of bird, and either write a sentence describing the beak, or feet, and how it is adapted, or draw a simple line diagram of these parts of the body. Fantastic art is not expected!


1. Body covered with hairto greater or lesser extent.

Functions: physical protection of body, insulation to reduce heat loss, provide coloration - usually camouflage.

2. Young are nourished by milk secreted by special MAMMARY GLANDS of female.

3. Skin has SWEAT GLANDS to cool body if required.

4. Sheet of muscle called DIAPHRAGM separates cavity of thorax (chest) from abdomen.

5. TEETH SPECIALISED for various functions , e.g. gripping, tearing, chewing.

6. EARS often have EXTERNAL FLAPS (pinnae) to direct sound waves to inner ear.

7. Brain and NERVOUS SYSTEM well developed, especially forebrain.

8. "Warm blooded" - CONSTANT BODY TEMPERATURE. General body functions more efficient than lower classes, e.g. better maintenance of body conditions.

A variety of HOMEOSTATIC MECHANISMS keep internal body conditions stable, e.g. concentration and pH of blood, which supplies all organs of the body (see later)

9. PARENTAL CARE is highly developed, and young depend on parents for a considerable time.

There are 3 main groups of mammals, which show a pattern of evolutionary development and increasing adaptability which may account for their success in COLONISING much of the Earth.

- the most primitive mammals - only 3 species:
duck-billed platypus, and 2 types of echidna (spiny anteater).

a) LAY EGGS (with LEATHERY, not chalky SHELLS). Platypus builds nest, and echidna develops pouch.

b) No specific mammary glands - NO TEAT - milk exuded from skin surface.

c) Adults have NO TRUE TEETH, but specialised feeding structures.

d) DISTRIBUTION: Australia, Tasmania, New Guinea.

- Kangaroos, wallabies, koalas, wombats, opossums, etc.

a) Give birth to very SMALL and POORLY DEVELOPED live young.

b) Young are protected inside a POUCH in the female's lap, containing a teat providing MILK for nourishment.

c) Have only one set of teeth.

d) DISTRIBUTION: Australasia, S. America, and 1 species in the U.S.A.
DISPLACED by the more efficient (?) true mammals, but have diversified along similar lines.

- most well-known and widespread mammals, common and exotic

a) Young are born fairly WELL DEVELOPED after quite a LONG PERIOD inside the female's body (gestation period). The developing young are nourished by the PLACENTA which enables them to use the FEMALE'S BLOOD system:

- to provide food and oxygen

- to remove waste products

- to keep constant internal conditions.

b) Young continue to be suckled after birth by mammary glands.

c) Have 2 sets of teeth (see later).

d) Placental mammals have been SUCCESSFUL in EXPLOITING many ENVIRONMENTS on Earth, and have DIVERSIFIED into many types, widely DISTRIBUTED. MAN is a placental mammal.

Explain in your own words the meaning of each of the terms written in capitals in the paragraph above.