Animals

Animals

1. Vertebrates

   • Fish
     • Animals which have scales, and fins on the thorax, stomach, back and tail and they are tube-shaped. The characteristics of fish are: They are aquatic and breathe through gills, can be carnivorous, omnivorous and herbivorous and that they are oviparous animals. We distinguish two types of fish: cartilaginous fish and bony fish. Cartilaginous fish, include sharks, rays and skates, 750 species, have jaws, a soft skeleton, and breath through gills. Bony fish, include trout, salmon, tuna and goldfish, 30,000 species, have jaws, a hard, bony skeleton, scales, and breathe through gills.
   • Amphibians
     • Many Amphibians lead two lives. The first is a life in water. The second is a life on land. Amphibians change a lot during their lives. The set of changes that amphibians undergo is known as metamorphosis. They need a lot of humidity to survive. All amphibians are carnivores and oviparous. Frogs begin their lives as legless tadpoles. Tadpoles have tails and breathe through gills. Over a period of days, the tadpoles grow legs, lose their tails, and develop lungs. Adult frogs fill the air with croaks and hop from place to place on land in search of insects. The young amphibians breathe through gills and the adult through lungs.
       • Curiosity: The name amphibian gives us a clue about the lifestyle of these vertebrates. This name comes from Greek. It means "both lives".
   • Reptiles
     • All reptiles have: lungs and breathe air, they also have hard scales that are waterproof. Most reptiles have eggs on land, (They are oviparous). The eggs have shells that are soft and leathery. The eggs of amphibians and fish do not have shells. An eggshell keeps the egg from drying out on land. Fish and amphibians lay their eggs either in water or in moist places. This is why their eggs do not need eggshells but, eggshells are of great advantage to reptiles. All reptiles are cold-blooded. This means that a reptile cannot automatically keep its body temperature steady. The blood of a cold-blooded animal can be cold or warm, depending on its surroundings. Dinosaurs are reptiles that became extinct about 65 million years ago. Important
   • Birds
     • Birds and reptiles share some characteristics, such as skin covered with hardBird scales and eggs covered with a shell. Today's birds have feathers. They do not have teeth in their mouth as dinosaurs did. They do not have claws on their front legs as some dinosaurs did. Classifying modern birds is much easier. They all have feathers, wings and very lightweight bones. This makes it easier for birds to lift off the ground and stay in flight for a long time. Birds do not have teeth. But they do have beaks. Birds' eggs are covered with a hard shell. Birds are warm-blooded. They can be carnivorous, omnivorous and herbivorous.
   • Mammals
     • The first mammals lived among the dinosaurs 220 million years ago. About 65 millions years ago, dinosaurs became extinct. Mammals became the dominant animals on Earth. Motther mammals feed milk to their young. This milk has proteins, fats, sugars, minerals, and vitamins and it is made in organs called mammary glands. Mammals live in all the different ecosystems both on land and in the sea. Some, such as bats, can even fly. Mammals are warm-blooded. Most of them are covered with hair or fur. This keep them warm in cold weather. Mammals have sweat glands. This help them keep cool in hot weather. The part of mammal's brain responsible for intelligence is more developed than that of other vertebrates.

2. Invertebrates

   • Not have a backbone or an internal skeleton. They are divided into 12 phyla or smalls groups.
   • Porifera
     • Are sponges, 9,000 species. Are the simplest invertebrates.They are quatic creatures full of pores and channels through which water can circulate. Adult sponges find a place (a rock) to attach themselves and live the rest of their lives there and without moving. They move around only when they are very young.
   • Cnidaria
     • They are hydras, jellyfish, corals and sea anemones, 10,000 species., Most have arm-like structures called tentacles around their mouths. Cells on the tentacles capture prey. Some attach themselves to rocks.
   • Molluscs
     • Found on land or in fresh water. Soft bodies covered by a thin tissue called a mantle. This mantle produces a hard shell in many molluscs to protect their bodies. Organ systems underneath it. Molluscs get food by moving around. The best-known are : gastropods (snails), bivalves (clams) and cephalopodes (squids)
   • Echinoderms
     • Very different from molluscs. One main difference is a kind of water-pumping system. Water-filled vessels extend from the mouth into the arms of the animal, water is pumped to the tube feet where are structures that help the animal grasp and move . They only live in marine ecosystem. Echinoderms have a hard covering made up of hard skins and spines.
   • Arthropods
     • There are 1,000,000 species. Arthropods live in water and on land. Many can fly. They have a hard outer body covering and jointed legs. They are divided into four groups:
       • Crustaceans , for example, (lobsters, crabs and shrimp): aquatic animals. Myriapoda, for example, (centipedes, millipedes): land creatures shaped like worms with a lot of legs. Arachnids , for example, (spiders, scorpions): land animals with eight legs. Insects, for example, (butterflies, ants): land animals, however some of them live in fresh water. They have six legs and two antennae.
   • Annelids
     • The best known worms, (segmented worms, have a tube-shaped digestive system with two openings, a circulatory system with hearts and blood vessels and nerves in each segment are connected to a main nerve cord. Bristles on the body help the worm dig into the soil.) that includes earthworms and leeches. There are 15,000 species. They live in water or damp soil. Their bodies are long, rounded, and divided into ring-like segments. Segmented worms

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