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Chpt 28 – Arthropods - - - - Phylum Arthropoda o Arthro = jointed o Poda = feet They are animals with jointed appendages They also have an exoskeleton Have segmented bodies o There is a great amount of diversity They have been around for over 600 million years Habitat o Aquatic – fresh and marine o Terrestrial o Air??? Do not live in water, nor the ground therefore air Body Plan o Have an exoskeleton Outside of their body Mostly make up of chitin (a carbohydrate) May be leathery and flexible • Ex) a caterpillar May be hard and ridged • Ex) crab or beetles Its function is to provide protection and for terrestrial and aerial arthropods, it also protects against water loss o Have jointed appendages Mostly for movement • With an exoskeleton, without joints, the animals could not move • Ex) antenna, claws, legs, wings, flippers o Has segmentation with cephalization Some of the animals have some segments that are fused together • Gives them a 2 part body plan instead of a 3 part body plan • Ex)the head and thorax of a crayfish is fused together therefore it is called a cephalothorax Feeding o There are all types of feeders Detritus – crabs and crayfish Filter feeders – barnacles - - - Carnivores – spiders, praying mantises Herbivores – most insects Parasitic – ticks, mites, lice o Some may have a very selective diet Ex) the monarch butterfly larva eats only milkweed o Some have general diets Ex) locusts and grasshoppers will eat all types of plants Digestion o Have a tube digestive system Mouth to anus Some specialized organs in between Also have specialized mouth parts depending on their feeding style and diet Respiration o There are 3 major types of respiratory structures 1 – gills – aquatic – ex) crabs • Are feather-like appendages under the exoskeleton • Form from parts of the mouth or legs o Movement of the mouth or legs keeps water flowing over the gills 2 – book gills or book lungs – • aquatic or terrestrial • Ex) horseshoe crab (aquatic) • Ex) some spiders (terrestrial) • Consist of several sheets of tissue layered like pages in a book • Found ventrally on the animal • There are openings called spiracles to allow air flow 3 – tracheal tubes – terrestrial only • Ex) all insects and some spiders • Openings (spiracles) on the abdomen lead to long branching tracheal tubes that reach into the animals body tissue • Movement of the body’s tissue cause the tracheal tubes to shrink and expand allowing for air to flow Internal transport o Have a very well developed heart o Have an open circulatory system o Some insects have cyanoglobin instead of hemoglobin Makes their blood green - - Excretion o Aquatic Generally done by diffusion Some aquatic arthropods have a green gland near the base of their antennae where metabolic waste is emptied o Terrestrial Have structures called malpighien tubes that concentrate and excrete the waste into the intestine Metabolic waste is removed along with undigested waste Responses o Have a very well developed nervous system All have a brain (anterior) • The brain also has 2 ganglia From the brain a long nerve cord runs ventrally along the body There are more ganglia along this nerve cord • The ganglia coordinates movement of the wings and legs o They have well developed sensory organs Statocysts Chemoreceptors • On or near the mouth, antennae or legs Receptors to detect vibrations • To detect sounds and movement They have a compound eye • An eye with 2000 or more separate lenses • Can detect movement • Can detect colours (including UV) Many have the ability to communicate • Ex) Crickets rub wings (sounds) o Moths use pheromones to attract a mate (chemicals) o Bees do a wiggle dance to indicate where flowers can be found (physical) Protection • Venom – bite or sting o Other chemical o Have bright colours • Powerful claws • Camouflage - Reproduction o Mostly separate sexes Some hermaphrodites o Internal fertilization o Some asexual reproduction Some can regenerate as well o There are very complicated life cycles As they grow, exoskeletons become too small • Molt – shedding of the exoskeleton • The new exoskeleton is softer and lacks pigments (for a while) There are 2 types of life cycles • 1 – incomplete metamorphosis – o Metamorphosis = to change o Has 3 stages Egg Nymph = small looking adult Adult • Ex) stick bugs, crickets, • 2 – complete metamorphosis – o Has 4 stages Egg Larva Pupa Adult • Ex) butterflies, beetles