Class AVES
Birds
ECOLOGICAL ROLE
Birds play an important role in the control of insects and in the pollination and dispersal of flowering plants.
Birds play an important role in the control of insects and in the pollination and dispersal of flowering plants.
MOVEMENT STRUCTURES/ TYPE
Aves have various adaptations for flight, such as a lightweight skeleton, two large flight muscles, the pectoralis, the supracoracoideus, as well as a forelimb (wing) that is used as an aerofoil (propeller). Feathers also help facilitate flight. Most birds can fly, which is their primary means of locomotion and transportation. Their flight is used for feeding, breeding, and escaping from predators. Avians have two appendages or legs that aid in walking or hobbling. Some birds cannot fly and instead get around by walking, running, or swimming. In avians that can fly, many of their large bones are fused together and form a sturdy frame that anchors the muscles used for flight. Birds also have large chest muscles that power the upward and downward wing strokes necessary for flight. The muscles attach to a long keel that runs down the front of an enlarged breastbone or sternum.
Aves have various adaptations for flight, such as a lightweight skeleton, two large flight muscles, the pectoralis, the supracoracoideus, as well as a forelimb (wing) that is used as an aerofoil (propeller). Feathers also help facilitate flight. Most birds can fly, which is their primary means of locomotion and transportation. Their flight is used for feeding, breeding, and escaping from predators. Avians have two appendages or legs that aid in walking or hobbling. Some birds cannot fly and instead get around by walking, running, or swimming. In avians that can fly, many of their large bones are fused together and form a sturdy frame that anchors the muscles used for flight. Birds also have large chest muscles that power the upward and downward wing strokes necessary for flight. The muscles attach to a long keel that runs down the front of an enlarged breastbone or sternum.
BODY COVERING; CELL LAYERS; LEVEL OF ORGANIZATION; PROTECTION
Aves are characterized by having feathers, being toothless, bipedal (walk on two legs), beaked jaws, laying hard-shelled eggs, a high metabolic rate, a four chambered heart and a strong skeleton. Feathers are epidermal growths attached to the skin and only arise in specific places of the skin called pterylae. The arrangement and appearance of feathers on the body may vary within species by age, social status and sex. Aves plumage (feather layers) are regularly moulted. Aves feathers also help camouflage when hiding from predators or being hidden from prey.
Aves are characterized by having feathers, being toothless, bipedal (walk on two legs), beaked jaws, laying hard-shelled eggs, a high metabolic rate, a four chambered heart and a strong skeleton. Feathers are epidermal growths attached to the skin and only arise in specific places of the skin called pterylae. The arrangement and appearance of feathers on the body may vary within species by age, social status and sex. Aves plumage (feather layers) are regularly moulted. Aves feathers also help camouflage when hiding from predators or being hidden from prey.
SUPPORT
Their skeleton consists of very lightweight bones. The skull bones in adults are fused and do not show cranial sutures. Their eye sockets are large and separated by a bony septum (wall). Their spine has cervical, thoracic, lumbar and caudal regions with a number of neck vertebrae that are very flexible.
Their skeleton consists of very lightweight bones. The skull bones in adults are fused and do not show cranial sutures. Their eye sockets are large and separated by a bony septum (wall). Their spine has cervical, thoracic, lumbar and caudal regions with a number of neck vertebrae that are very flexible.
OBTAINING NUTRIENTS
Aves diets vary depending on the environment they belong to. Most aves diet include fruits, plants, seeds, insects, decaying flesh of an animal, and small animals including other birds. Aves digestive system is adapted to whole food items, since avians have no teeth to chew food. However, many birds have a specialized structure called the crop (located at the lower end of the esophagus) in which the food is stored and is moistened in, before it moves into the digestive tract. Most avians obtain water by scooping it into their beaks and raising their head to let water run down the throat.
Aves diets vary depending on the environment they belong to. Most aves diet include fruits, plants, seeds, insects, decaying flesh of an animal, and small animals including other birds. Aves digestive system is adapted to whole food items, since avians have no teeth to chew food. However, many birds have a specialized structure called the crop (located at the lower end of the esophagus) in which the food is stored and is moistened in, before it moves into the digestive tract. Most avians obtain water by scooping it into their beaks and raising their head to let water run down the throat.
RESPIRATION
When birds inhale, more than half of the oxygen flows past the lungs and directly to the posterior air sac, which extends from the lungs and connects with the air spaces in the bones, filling them with oxygen. The other amount of oxygen goes directly into the lungs. When the bird exhales, the carbon dioxide flows out of the lungs and the stored oxygen from the posterior air sac then goes into the lungs. This results in the bird's lungs constantly receiving fresh air during both inhalation and exhalation.
When birds inhale, more than half of the oxygen flows past the lungs and directly to the posterior air sac, which extends from the lungs and connects with the air spaces in the bones, filling them with oxygen. The other amount of oxygen goes directly into the lungs. When the bird exhales, the carbon dioxide flows out of the lungs and the stored oxygen from the posterior air sac then goes into the lungs. This results in the bird's lungs constantly receiving fresh air during both inhalation and exhalation.
CIRCULATION
The avian circulatory system consists of a four-chambered heart contained in a fibrous pericardial sac. The heart is divided into a right side and a left side, each having an atrium and a ventricle. Blood moves through the arteries that become narrow due to contraction, and into the arterioles that act as a transportation system that distributes oxygen and other nutrients to the tissues of the body. Travelling through the arterioles, blood moves into the capillaries where gas exchange can occur. Once the blood has become deoxygenated, it travels through venules, to the veins and the blood is brought back to the heart. When the blood reaches the heart it moves into the right atrium and then the right ventricle to be pumped through the lungs for further gas exchange of carbon dioxide waste. Oxygenated blood then flows from the lungs through the left atrium to the left ventricle where it is pumped out of the body. Birds have two separate circulatory loops, so that there is complete separation of oxygen-rich and oxygen-poor blood. One half of the heart receives oxygen-poor blood from the body and pumps this blood into the lungs. Oxygen-rich blood returns to the other side of the heart to be pumped to the rest of the body.
The avian circulatory system consists of a four-chambered heart contained in a fibrous pericardial sac. The heart is divided into a right side and a left side, each having an atrium and a ventricle. Blood moves through the arteries that become narrow due to contraction, and into the arterioles that act as a transportation system that distributes oxygen and other nutrients to the tissues of the body. Travelling through the arterioles, blood moves into the capillaries where gas exchange can occur. Once the blood has become deoxygenated, it travels through venules, to the veins and the blood is brought back to the heart. When the blood reaches the heart it moves into the right atrium and then the right ventricle to be pumped through the lungs for further gas exchange of carbon dioxide waste. Oxygenated blood then flows from the lungs through the left atrium to the left ventricle where it is pumped out of the body. Birds have two separate circulatory loops, so that there is complete separation of oxygen-rich and oxygen-poor blood. One half of the heart receives oxygen-poor blood from the body and pumps this blood into the lungs. Oxygen-rich blood returns to the other side of the heart to be pumped to the rest of the body.
EXCRETION
Aves kidneys extract nitrogenous waste from their bloodstream, converted to uric acid, and deposited in the cloaca. In the cloaca is where most of the water is reabsorbed leaving the uric acid in a white pasty form. Birds do not have a urinary bladder or external urethral opening, and the uric acid is excreted along with the feces as a partially solid waste.
Aves kidneys extract nitrogenous waste from their bloodstream, converted to uric acid, and deposited in the cloaca. In the cloaca is where most of the water is reabsorbed leaving the uric acid in a white pasty form. Birds do not have a urinary bladder or external urethral opening, and the uric acid is excreted along with the feces as a partially solid waste.
RESPONSE
Aves have a well developed brain, capable of flight related functions, movement, behavioural patterns, navigation, mating and nest building. Avians also have a highly developed visual system. Most birds cannot move their eyes. Birds with eyes on the sides of their heads, have a wide visual field while birds with eyes at the front of their heads have binocular vision. Most avians have a poor sense of smell. They have specialised light sensing cells in their brains that respond to light without using their eyes or other sensory neurons. Birds communicate using primarily visual and auditory signals.
Aves have a well developed brain, capable of flight related functions, movement, behavioural patterns, navigation, mating and nest building. Avians also have a highly developed visual system. Most birds cannot move their eyes. Birds with eyes on the sides of their heads, have a wide visual field while birds with eyes at the front of their heads have binocular vision. Most avians have a poor sense of smell. They have specialised light sensing cells in their brains that respond to light without using their eyes or other sensory neurons. Birds communicate using primarily visual and auditory signals.
REPRODUCTION
Aves are either male or female, and reproduce sexually through internal fertilization. Sperm is transferred to the female during copulation by direct contact of the two cloacas. The male briefly stands on the back of the female, and the cloacas are pressed together. The sperm reaches the female's ovaries and the egg is fertilized. The fertilized egg develops inside a hard-shelled egg case. The hard-shelled eggs have a fluid filled amnion, a thin membrane forming a closed sac around the embryo. When the eggs have developed enough inside the female, they are then laid in a nest and and incubated until ready to hatch. Almost all avian species remain together for breeding and take care of their young for an extended period of time. The parents usually take turns incubating the eggs, and feeding the hatched young.
Aves are either male or female, and reproduce sexually through internal fertilization. Sperm is transferred to the female during copulation by direct contact of the two cloacas. The male briefly stands on the back of the female, and the cloacas are pressed together. The sperm reaches the female's ovaries and the egg is fertilized. The fertilized egg develops inside a hard-shelled egg case. The hard-shelled eggs have a fluid filled amnion, a thin membrane forming a closed sac around the embryo. When the eggs have developed enough inside the female, they are then laid in a nest and and incubated until ready to hatch. Almost all avian species remain together for breeding and take care of their young for an extended period of time. The parents usually take turns incubating the eggs, and feeding the hatched young.