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Joint-Legged Animals 465/8

Joint-Legged Animals 465/8. By: Amina Nur. Animals With Exoskeletons (Phylum Arthropoda ). In terms of numbers, Arthropods dominate animal life 9 000 000 arthropods are estimated to be undiscovered All have segmented bodies, suggesting evolution from segmented Annelid Worms

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Joint-Legged Animals 465/8

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  1. Joint-Legged Animals 465/8 By: Amina Nur

  2. Animals With Exoskeletons(Phylum Arthropoda) • In terms of numbers, Arthropods dominate animal life • 9 000 000 arthropods are estimated to be undiscovered • All have segmented bodies, suggesting evolution from segmented Annelid Worms • Segments become more specialized in higher Arthropods, nearly all segments differ in function • They developed exoskeletons, joint legs and a hemocoel(blood cavity) • Exoskeleton is a thick external covering composed of strong waterproof carbohydrate molecules called Chitin • Protects animal, resists desiccation (drying out) in non aquatic environments, allowing them on land • Rigidity prevents efficient locomotion • Evolved appendages and groups of muscles which evolved into joints increasing mobility • No longer needed coelom to provide body shape • Reduced ability for gas exchanged. Aquatic arthropods developed gills that took in O2 and expelled CO2 • Many arthropods evolved Tracheae to carry O2 to body • Rigidity hindered growth, they shed exoskeleton when they grew and replaced them with a bigger one (adapted by moulting) • Circulatory system has a hemocoel • Over time their bodies replaced body fluid with bloodwhich travelled through vessels and emitted into hemocoel • It bathed organs directly in an arrangement called Open Circulatory system • Developed sensory receptors: eyes and antennae

  3. Segments of exoskeleton modified in different arthropod groups. Specialized regions, modified, joint appendages, and groups of muscles improved arthropod function and mobility.

  4. Class Arachnida • Includes: Scorpions, spiders, mites and ticks • Body has 2 parts: head fusing to body segments forming cephalothorax • Posterior body segments (abdomen) contain most organs • Arachnids have 6 pairs of appendages – each for different functions: • To feed • Sense environment • The last 4 are used to walk Reproduction: • Male inserts sperm into small sac in the female called the seminal receptacle where fertilization occurs Life cycle: • Miniature adults hatch from eggs and live independently from the time they hatch • Gas exchanges through book lungs (highly folded membranes) in abdomen • Silk glands in spiders’ abdomen produce protein threads for spinning webs • Many spiders build webs with their silk, but some use their long threads to mate or protect young

  5. Class Crustacea • 40, 000 species • 3 Regions make up body: • Head • Thorax • Abdomen • Exoskeleton forms thick carapace (covers head + other segments) • 2 appendages, antennae, followed by the mandibles • Mandibles crush food and feed it to the mouth • Behind mandibles, a pair of millipedes – sense environment, search for food • Behind that, large claw like Chelipeds grab food and protect themselves from predators • Four legs follow the Chelipeds • On the abdomen, 6 pairs of swimmerets help crustacean swim • Pair of flat appendages (Uropod) lie on tail (Telson) behind posterior end of abdomen • These act as paddles, moving the animal backwards • They have many gills, connected to walking legs, which is protected by Carapace • Gils are feathered to increase gas exchange surface area • Gases in water diffuse into and out of the gills and travel through the circulatory system to body tissues • To increase diffusion through blood vessels of gills, swimmerets on telson beat and sweep water forward, under carapace and over the gills. • Males and females come together to copulate

  6. Class Insecta • Numerous of all animals species • + 1.5 million species • Insect bodies are like those of a crustacean • On their heads one antenna senses the environment • On the thorax, there are 3 pairs of legs • Gas exchanged carried out through air sacs and tubes (trachea) • Adults of flying insects, usually have two pairs of stiff membranous wings attached to the thorax • Flies have only one. In beetles, front wings form hardened wing covers • Separate sexes to produce egg and sperm • Some insects undergo simple development, hatching like miniature adults • Winged insect undergo complex developments • Body structure changes radically in process of metamorphosis – change of shape and diet • Transform from worm-like larva maturing through each instar, or early stages into adults • Diet change minimizes the competition for food between larvae and adults • This increase species’ chances for survival

  7. Class Diplopods and Chilopods • Diploids  millipedes • Millipede suggest the insect has thousands of feet • Members of this class only have about a hundred pair of legs • Number of segments in the body range from 10 – 100 • Each segment has 2 pairs of feet (Diplopod means ‘double footed’) • Chilopods are known as centipedes • Like Diplopods, Chilopods only have about 10 – 100 pairs of legs • Each segment contains only one pair • Chilopods: • Diplopods:

  8. Joint-Legged Animals By: Amina Nur  Biology sucks…we all know nobody was really listening…

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