Classification: birds Chong yee ting 6s (3)

Introduction Class:Aves Homoiotherm vertebrates There are around 10,000 living species Most birds can fly, walk and run, many can swim and dive Size of the birds can vary from the tiny flowerpeckers & hummingbirds have a keen eyesight and good hearing but sense of taste and smell is poor (e.g ostrich鴕鳥,penguin,robin知更鳥,pigeon鴿,owl) Most birds can fly, walk and run, many can swim and dive(seabird:e.g.Gannet). (but some larger birds like Penguins, Ostrich and Kiwi are flightless. ) Birds are terrestrial animals but the majority of species also explore the aerial environment by flying (in size from the 5 cm Bee Hummingbird to the 2.75 m.)

Body structures (diagram) birds have their eyes positioned on the side of their head. This means that at certain distances each eye will see a different image. Some birds can alter this typical patter though.

General features Have feathers covering the body legs are covered with dry scales hollow bones have a beak for feeding forelimbs have been modified to become wings have lungs for breathing

Wings

Different shapes of wings correspond to beneficial characteristics: speed low energy use types of wings: elliptical wings high speed wings high aspect ratio wings soaring wings with slots.

Flight Hollow bones reduce weight Bird’s flight muscles work continuously, pushing the air down to produce lift that balances the weight. Birds have lightweighted bones with internal spaces filled with air. These bones are called pneumatic bones. This feature reduces the corporal density of the animal facilitating the flight. The power required to fly is highest when the air speed is zero (hovering), and decreases at medium and high speeds. However, additional power is required to overcome the air drag, and this increases with speed.

The actual available power dwindles as the size of the bird increases large birds : have just enough power to fly near the minimum power speed OR flightless There is a clear speed range at which the power required to fly is lower than at either slower or faster speeds. thus reaching an upper limit to the mass (about 16 kg) of viable flight-capable birds. swans, such as Ostriches and Emus, are flightless.

Feathers Feathers have evolved to serve a variety of functions : flight heat conservation waterproofing camouflage display three main types filoplumes (sensory feathers) contour feathers down feathers (insulation). Bird feathers are amazingly complex. Each feather is made from the protein Keratin. While keratin also makes up snake and lizard scales, it is a slightly different compound in birds. The contour(e.g chicken) feathers overlap each other, its seems like they are all one continuous covering.

Feathers for different functions Examples: Owls : velvet-like projections fly silently Sand-Grouse: feathers with highly curled barbs hold water Some birds have modified this arrangement. Owls for instance have velvet-like projections that extend from their feathers that allow them to fly silently. Sand-Grouse that live in desert locations have feathers with highly curled barbs. These barbs will hold water when a bird dips into an oasis

Reproduction Sexual,internal fecundation on land lay eggs with chalky shells Males have two testes and females have one ovary (with lots of yolk which is a source of nutirents) (Birds reproduce by laying eggs which are fertilised internally before laying. The eggs have a hard shell and a food store in the form of yolk and albumen. The number of eggs laid depends on the species, and varies from 1 to about 20. )

Male Female The testes of birds are not much different than that of other vertebrate animals. For copulation, the male has to get his cloaca close to the tip of the cloaca of a female bird. The male mounts the female, applies his reproductive openings to hers and passes sperm into her oviduct, thus enabling the eggs to be fertilized internally.

Courtship Examples: Pairing: |A sequence of behavioural activities Nest building: One of the pair or both birds construct a nest e.g. courtship display, leads to pair formation; a male and female bird pairing at least for the duration of the breeding season. which may be an elaborate structure woven from grass, leaves, feathers, etc., or little more than a hollow scraped in the ground.

Respiratory system Importance do not have a diaphram push the sternum in and out 75% of the fresh air into bones and fills them with air. 25% of the air goes directly Importance for flying need high metabolic rate -The avian respiratory system differs from mammals in many ways. Bird respiration is much more efficient. Birds do not have a diaphram. In mammals this muscle moves up and down to increase and decrease the chest cavity. Birds push the sternum in and out to the same effect -Birds have one of the most complex respiratory systems of all animal groups.Upon inhalation, 75% of the fresh air bypasses the lungs and flows directly into a posterior air sac which extends from the lungs and connects with air spaces in the bones and fills them with air. The other 25% of the air goes directly into the lungs. Due to having the high metabolic rate required for flying, birds have a high oxygen demand. They meet this by having a respiratory system more efficient than that of a mammal or a reptile. Birds ventilate their lungs by means of posterior and anterior air sacs (seven or nine) which act like bellows, but do not play a direct role in gas exchange. The air sacs of birds extend into the humerus (the bone between the shoulder and elbow), the femur (the thigh bone) and the vertebrae.

Evolution birds evolved from theropod dinosaurs around 150–200 million years ago Evidence Bird-like respiratory systems in dinosaurs hollow bones The fossil record indicates that birds evolved from theropod dinosaurs during the Jurassic period, around 150–200 Ma (million years ago)

Evolution--beak birds' beaks have evolved to suit the ecological niche they fill diet are varied (e.g fruit,seeds) On some birds, the tip of the beak is hard, dead tissue On other birds, (e.g ducks) The beak grows throughout the bird's life. Birds' diets are varied and often include nectar, fruit, plants, seeds, carrion, and various small animals obtain food or feed on a variety of food items are called generalists, while others that concentrate time and effort on specific food items or have a single strategy to obtain food . On some birds, the tip of the beak is hard, dead tissue used for heavy-duty tasks such as cracking nuts or killing prey. On other birds, such as ducks, the tip of the bill is sensitive and contains nerves, for locating things by touch. The beak is worn down by use, so it grows continually throughout the bird's life.

Gannets Gannets hunt fish by diving from a height into the sea and pursuing their prey underwater. adaptations which enable them to do this: they have no external nostrils they have air sacs in their face and chest under their skin their eyes are positioned far enough forward on their face they have air sacs in their face and chest under their skin (which act like bubble wrapping, cushioning the impact with the water) ( to give them binocular vision, allowing them to judge distances accurately.) (Gannets can dive from a height of 30 m, achieving speeds of 100 km/h as they strike the water, enabling them to catch fish much deeper than most airborne birds.)

Additional information Chromosome(Z,W) male:ZZ female:WZ Sex determination determined at fertilization determined at temperature Red blood cells have a nucleus. In nearly all species of birds, an individual's sex is determined at fertilization. However, one recent study demonstrated temperature-dependent sex determination among Australian Brush-turkeys, for which higher temperatures during incubation resulted in a higher female-to-male sex ratio.

Sources End 1.http://en.wikipedia.org/wiki/Bird 2.http://www.birding.in/ornithology/bird_flight.htm 3. http://www.birding.in/bird_topography.htm 4. http://www.biology-questions-and-answers.com/birds.html 5. http://www.birding.in/birds.htm 6. http://www.thewildclassroom.com/biodiversity/birds.html 7. http://en.wikipedia.org/wiki/File:Bird_Diversity_2011.png End