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Biologia y geologia (2) (3.Earthworms, leeches and many sea worms are…
Biologia y geologia (2)
1.Sponges:live fixed to the substrate. Their bodies are pierced with hundreds of tiny pores that are interconnected by channels. Their skeletons are made up of tiny spines of spongina.Other kinds of sponges have skeletons made from silica or calcium carbonate.
1.Feed by filtering water through their pores.The central cavity that collects water are called spongocoel.that capture oxygen and nutrients are called choanocytes. The water and waste leave through the osculum.
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2.Cnidarians:Polyps. These take the form of a bag. There is a suction cup at one end that fixes to the substrate.There is a single opening that is ringed by tentacles. The opening acts as both a mouth and anus.
2.Jellyfish.Form of an umbrella. They look like squashed, upside-down polyps. They live free, floating through the water.Are carnivorous,capture their preys trough the tentacles, that have a paralysing toxine
3.Earthworms, leeches and many sea worms are annelids. Most annelids are aquatic, but the ones that are most familiar to us, such as the earthworm, live in soil that is moist. Characteristics:
It is soft, long and split into rings or segments with fine bristles called setae, which help the worm move.
In the central part of the body, there is a group of thicker rings, the clitellum, where the reproductive organs are located.
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4.Characteristics of molluscs:Are three groups:Gastropods,bivalves and cephalopod.
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They have a fold, called a mantle, in the dorsal part of the body. This fold contains the respiratory organs. In many cases, it also produces an outer protective shell made of a hard calcareous material.
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5.Garden snails are one of the few land snails. They are gastropods. They have the following physical characteristics:
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A foot, which is a large mass of muscle that supports the snail's body.
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Physical characteristics of arthropods:
are invertebrates with articulated appendages. An arthropod’s body has the following characteristics:
It is segmented but the segments are not the same. They have a head, a thorax and an abdomen.In some cases we can't distinguished the head and the torax.
It has articulated appendages. The appendages used for moving about are called legs.
It has a hard covering, which makes up its exoskeleton.
Aquatic arthropods breathe through gills; terrestrial ones, through tracheae.
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Arachnids:
Cephalothorax. This is formed by the head and the thorax. There are a pair of appendages at the rear, the chelicerae, and another pair, the pedipalps, used to handle prey. They have four pairs of legs.
Abdomen. It is balloon-like and is not segmented. At one end, there are the spinnerets.
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Crustaceans:
Cephalothorax. This has two pairs of sensory antennae and five pairs of legs; the first of these in the form of large pincers.
Abdomen. This is segmented and has appendages that are not used for moving about.
