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Reptiles and Birds Life Science Reptiles Reptiles are vertebrates that have lungs, scaly skin, and a special type of egg. Reptiles are also ectotherms, or cold-blooded. Reptiles include: snakes, turtles, crocodiles, iguanas, and the now extinct dinosaurs and pterodactyls. History of Reptiles Reptiles first appeared hundreds of millions of years ago shortly after the first amphibians evolved. The first reptiles looked like a cross between a lizard and a toad. However, reptiles had several adaptations that made them land animals. Characteristics of Reptiles: Water Loss Reptiles have skin that is covered with a tough, dry layer of scales. The scales are made of dead cells and provided them with waterproof skin which keeps them from losing water. Reptiles also have special kidneys that help them to loses as little water as possible when wastes are eliminated. Characteristics of Reptiles: Anatomy Reptiles have a double-looped circulatory system. In some reptiles there oxygen rich blood and oxygen poor blood never mix. Reptiles are dependent upon their lungs for oxygen, they can’t breathe through their skin because of their scales. Reptiles have a slightly more developed brain than amphibians and better sense organs. Characteristics of Reptiles: Eggs The reptile egg is surrounded by a protective shell that prevents the insides from drying out. Most reptile eggs are tough and flexible with a leather-like covering. There are tiny holes in the shell that allow gas exchange, but prevent water from leaving the egg. Importance of the Egg The reptile egg is important because it meant that reptiles were no longer dependent on water to reproduce. Secondly, it shows that both birds and mammals evolved from reptiles. Bird eggs are very similar to reptile eggs and the tissues that protect a mammal embryo are the same as the ones that protect a reptile embryo. Reptile Reproduction Reptiles have internal fertilization. Internal fertilization is important because after the egg if fertilized, then the female’s body builds the protective shell around it. Most reptiles lay their eggs right after the shell is formed, but some carry them around until the eggs are ready to hatch. Lizards Lizards are reptiles that typically have slender bodies, movable eyelids, long tails, four legs, and clawed toes. They range from 3 cm long geckos to 4.5 m long monitor lizards. Lizards are primarily sedentary insect eaters. Some lizards have evolved adaptations such as: The chameleons' tongue and ability to change color The Gila monster’s poisonous bite Snakes Snakes are basically lizards that have lost their legs, eyelids, and ears about 80 million years ago. Snakes move by wriggling its long, thin, muscular body and using their scales to get traction. Snakes typically feed on small animals like mice. Snakes are deaf and have poor eyesight, however they have the ability to smell using their tongues and detect heat through special pits in their heads. Some snakes have also evolved poison glands that they use for hunting and protection. Turtles Turtles are reptiles whose bodies are enclosed in a shell. The shell is made of plates of bone covered by a scale like substance. Turtles do not have teeth, they have beaks similar to birds. Turtles can eat both plants and animals. Alligators and Crocodiles Alligators and crocodiles are large meateating lizard-like reptiles. They have long snouts, powerful tails, and thick, armored skin. Alligators and crocodiles spend much of their time submerged in water. They are nocturnal and hunt everything from insects to hoofed mammals to Jr. High kids. They also build nest to lay their eggs in. Birds Birds are warm blooded egg-laying vertebrates that have feathers. Feathers are the most important characteristic of birds. Feathers are made of dead cells that contain the same material that is found in your fingernails. Feathers Feathers come in all shapes, sizes, and colors. Feathers on the wings and the bird’s body are called contour feathers. Down is short, fluffy feathers that act as insulation. Feathers are used for flight, camouflage and to attract mates or communicate. Bird Nutrition Birds must expend energy to maintain their body, therefore they eat large amounts of energy. Flying also demand a lot of energy. Birds eat many foods including bacteria, fruits, seeds, insects, other birds, small mammals and dead material. A bird’s beak is adapted to the type of food it eats. Bird Flight Birds bones are hollow which makes them lighter for flight. The internal organs are also adapted for flight. The lungs are adapted with special air sacs which allow them to have a constantly moving supply of fresh air. Birds have a double-loop circulatory system that is completely separate to insure oxygen is delivered. Bird Anatomy Birds have two long, oval kidneys that produced concentrated waste products. Birds have well developed brains and some have very good eyesight. Birds have small compact reproductive systems that are only functional during breeding season. Bird eggs have the same basic structure as reptile eggs, only they have a hard shell. Bird Communication Birds sing for a variety of reasons including: To attract a mate To warn other birds To establish their territory Birds also communicate with their feathers. Bird Nests Most birds build nests to protect their eggs and their young to develop. The nest can vary from a hollow trench to elaborate materials such as spider silk. Migration Many birds migrate to new environments during different seasons of the year. Some travel over 25,000 km. Birds migrate for many reasons including: Seasonal food supplies Nesting habitats Types of Birds There are around 8700 living species of birds. They are divided into the groups: Song birds like cardinals, robins & nightingales Hunting birds like hawks, eagles & owls Waterfowl like ducks, geese & swans Flightless birds like penguins, ostrich & emus.