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==How do they move?== | ==How do they move?== | ||
Flight is obviously one key of mowing that an arthropod, more exactly an insect, can make. An animal that can fly that can escape many predators, find food and mates, and disperse to new habitats much faster that an animal that must crawl about on the ground. Because their wings are extensions of the eskoleton and not true appendages, insects can fly without sacrificing any walking legs. Unlike the flying vertebrates, like birds and bats, have one of their two pairs of walking legs modified for wings, which explains why these vertebrates aren't generalley very swift on the ground. | Flight is obviously one key of mowing that an arthropod, more exactly an '''insect''', can make. An animal that can fly that can escape many predators, find food and mates, and disperse to new habitats much faster that an animal that must crawl about on the ground. Because their wings are extensions of the eskoleton and not true appendages, insects can fly without sacrificing any walking legs. Unlike the flying vertebrates, like birds and bats, have one of their two pairs of walking legs modified for wings, which explains why these vertebrates aren't generalley very swift on the ground. | ||
Since their joints haven't exocuticule, Arthropods can | Since their joints haven't exocuticule, Arthropods can move their members and fold a segment over the other one. Their movements are produced by the contraction and the slackening of the fibers of striated muscles. The majority of Arthropods use their members as locomotive means to move, for example the aquatic species use it as paddle and the species ground as legs, to settle, by means of hooks or of flattened lobes serving as suction cups and for "fouisser" (presence of peaks). | ||
Version du 22 janvier 2011 à 17:50
What is an Arthropod?
Arthropods are eukaryotic multicellular heterotrophic organisms that obtain nutrients by ingestion. Arthropods are members of the most diverse phylum in the animal kingdom. They are named for their jointed appendages, which enable these animals to move despite their hard outer covering, the exoskeleton and have a segment body.
PICTURE needed. Head-Thorax-Abdoden
What is Arthropod's jointed appendages?
Limbs are a prominent feature of species in many phyla. They are particularly important in two major lineages: the ecdysozoans and the vertebrates. Some members of the Ecdysozoa, such as arthropods, have more complex, jointed limbs, which make fast, precise walking, running, jumping movements possible and are a prominent limb type in vertebrates and arthropods. Arthropod's appendages of different segments are variously adapted for walking, feeding, sensory reception, reproduction, swimming and defense. Thanks to the evolutionary flexibility of their segments and appendages, it contributes to the great diversification of arthropods.
PICTURE of appendages needed
What is the diversification of Arthropods?
The estimation about the total arthropod population numbers is a billion billion individuals, but only a million species has identified, mostly insects. They must be regarded as the most successful animal phylum. The major groups of Arthropods are Arachnids, Crustaceans, Millipedes, Centipedes, and Insects.
What are the differences between these five groups?
Arachnids usually have four pairs of walking legs and specialized pair of feeding appendages.
Crustaceans are almost all marine organisns but some live in fresh water or in a terrestrial environment. They all have a crustacean hallmark of multiple pairs of specialized appendages.
Millipeds eat decaying plantmatter.
Centripeds are carnivores are the only arhtropods without atenna . They have a pair of poison claws and a single pair of long legs. Both (millipeds and centripeds)have segmented body and jointed legs.
Insects have six legs and mostly have two pairs of wings.
Maybe you could mention the main characteristics of each group by using a TABLE?.
What are the main characteristics of animals?
Where do they live?
Arthropods can live almost everywhere: on earth, in water, at high height, in deep caves, in deserts and even in glaciers.
How do they feed?
Arthropods feed on different way: of alive or dead organic matter, sometimes live as a parasite on other dead animals. According to their way of food, the structure of the digestive tract changes.Only the central part of the digestive tract is used for the extreme digestion, the extrem parts are covered with cuticle.
Arachnids
Arachnids paralyze them predators thanks to their poison. They can store the food in a cavity.
Crustaceans
crustaceans use their appendix to create a current which brings them the food to the mouth. They are filtreurs (zooplankton) or détritivores (crawfish, lobster).
How do they reproduce?
Arachnids
The male weaves a web on which it is going to deposit its sperm. It leaves then in search of a partner. After the coupling, the female eats generally its partner (source of food).
Crustaceans
Females spawn. Larvas ( called nauplius ) moult several times before reaching the adult stage. This process occurs most of the times, but some crustaceans are however hermaphrodits.
Millipedes, Centipedes, and Insects
Millipedes, centipedes and insects spawn, with extern fertilization. As crustaceans, insects pass by several embryonic stages before reaching the adult stage. In certain species, larvas look like the adults (ametaboles insects). Others undergo a metamorphosis. The metamorphosis is incomplete by hemimétaboles (3 stages: egg, larva, adult. The larva looks like the adult but has no wings) and complete by holometaboles (4 stages: egg, larva, nymph, adult. The larva is completely different from the adult).
How do they move?
Flight is obviously one key of mowing that an arthropod, more exactly an insect, can make. An animal that can fly that can escape many predators, find food and mates, and disperse to new habitats much faster that an animal that must crawl about on the ground. Because their wings are extensions of the eskoleton and not true appendages, insects can fly without sacrificing any walking legs. Unlike the flying vertebrates, like birds and bats, have one of their two pairs of walking legs modified for wings, which explains why these vertebrates aren't generalley very swift on the ground.
Since their joints haven't exocuticule, Arthropods can move their members and fold a segment over the other one. Their movements are produced by the contraction and the slackening of the fibers of striated muscles. The majority of Arthropods use their members as locomotive means to move, for example the aquatic species use it as paddle and the species ground as legs, to settle, by means of hooks or of flattened lobes serving as suction cups and for "fouisser" (presence of peaks).
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