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Invertebrates are animals that have no backbone. An arthropod is an invertebrate with an exoskeleton, a segmented body, and jointed legs. Some arthropods – such as insects, centipedes, and millipedes are thought to have evolved from ancestors of annelid worms. Other arthropods, such as crustaceans, spiders, and trilobites (which are extinct), are thought to have evolved from ancient and distantly related ancestors. There are more than 1 million kinds of arthropods on Earth. An exoskeleton is a hard, outer covering. Exoskeleton - Made of Chitin - May be Flexible or very hard - Usually waterproof in terrestrial arthropods - Serves as protection - Cannot grow as the arthropod grows Molting is to leave an exoskeleton and grow a new one. Segmented Bodies Some arthropods have appendages on every segment Other arthropods have lost segments as they have fused together; some appendages are lost as a result. Jointed Appendages Antennae Claws Walking legs Wings Flippers Etc. They also have… A brain (in dorsal portion of head) A ventral nerve cord An Open Circulatory system Internal Transport: They have an open circulatory system – the heart contracts; blood is pumped through arteries to vessels, and then enters sinuses in the tissue. Respiration: The three basic respiratory structures found in arthropods are: 1. Gills: movement of mouthparts and appendages keep water moving over gills; most look like a row of feathers under the exoskeleton 2. Book gills and book lungs: Layered sheets of tissue increases surface area (SA) for gas exchange; in spiders, spiracles connect book lungs with outside air 3. Tracheal Tubes: lead from spiracles into tissues of the arthropod; movements of body cause tracheal tubes to expand and contract, moving air in and out through the spiracles. Response: Arthropods have a well-developed nervous system: Brain with a pair of ganglia Pair of nerves connect brain to ventral nerve cord Ganglia along the length of the ventral nerve cord (coordinate movement of legs and wings) Statocysts (involved in balance) Chemical receptors - crustaceans and insects have a well-developed sense of taste - chemical receptors are found in mouthparts, antennae and legs Response continued: Most arthropods have compound eyes (which detect color and motion very well) Crustaceans and insects have sensory hairs that detect movement (of water or air) Most insects have well developed ears/hearing (oval tympanum) Excretion: Terrestrial arthropods: Malpighian tubules remove nitrogenous wastes from blood, concentrates the wastes, and adds them to solid wastes prior to elimination (through the anus); some also have excretory glands at the bases of legs Aquatic arthropods: Metabolic wastes diffuse out of the body at the gills; some have a gland called a green gland (in the head) that empties metabolic wastes out of the body Reproduction: Arthropods reproduce sexually Internal fertilization (within the female) Spiders and some crustaceans: male deposits a sperm packet that the female picks up Most insects and crustaceans: males deposit sperm inside the female via a specialized reproductive organ Movement: Muscle systems coordinated by the nervous system Muscles allow the movement of appendages by generating a force agains the exoskeleton Subphylum Trilobita – all forms believed to be extinct – could be some of the earliest arthropods Subphylum Chelicerata – First pair of appendages form ‘Chelicera’ or pincher-like structures used for feeding. 4 pairs of walking legs, no antennae. The ‘Arachnida’ is the only important parasitic group. Subphylum Crustacea = mostly aquatic, most have gills, two pair of antennae. Biramous appendages, meaning limbs have more than one branch. Also have mandibles. Some are parasitic, but we will not cover them. Subphylum Uriramia – single branch or ‘Uriramous’ appendages, mandibles, one pair of anntennae. Diplopoda – Millipedes – two pairs of legs per body segment Chilopoda – Centipedes – one pair of legs per body segment Insecta – 3 pairs of legs on adults, many with wings. Most important group. A crustacean is an arthropod that has a hard exoskeleton, two pairs of antennae, and a mouth for crunching and grinding. Crustaceans can ________ certain parts of their body. A ___________ can re-grow its claws. Most crustaceans live in ______ and get oxygen from the water through _________. Gills are Crustaceans live in a wide range of habitats, from marine, to fresh water, and even terrestrial – they were the first animals to colonize land. * Centipedes and millipedes are arthropods that have many legs. * Have _______ pair of legs in each segment. * Are carnivores and eat _________. * To capture its prey, a centipede puts _______ into the prey’s body with its_______. * Centipedes are found in ___________ like under rocks and in the soil. * Have ___ pairs of legs on each segment. * Eat _________ and are shy animals. * When scared, it _________________ to protect itself. * Do not have ________. * Are found in __________like under rocks and in the soil. * All have __________ legs. * Have a body divided into two parts: •______________________________ •________________________________ * Spiders usually eat __________, but some spiders eat small _______________ like hummingbirds. * Many spiders make webs out of _________. * Silk is _________________________________. * Spiders catch their prey in many different ways. * Some spiders catch their prey in ____. * Some spiders ________ from their prey and then ________________. * When spiders catch their prey, they _______ it and _________ it. * Spiders breathe oxygen with __________. * Scorpions usually live in __________ areas. * Most scorpions are __________________. ** Nocturnal means ____________________ * During the day, scorpions hide __________ ______________________________. * When scorpions capture prey, they _______ ___________________________________. * Ticks and mites live on _______________. * Some ticks and mites suck juices from ____________________. * Other ticks and mites are very tiny and live on __________. * Many ticks suck the blood from _________. * Ticks can spread ________. *There are more kinds of insects than there are all other animal species all together. * There could be _______________ times as many insects as humans on Earth. * Insects have a body that is divided into ____ parts. * An insect’s body is divided into a ________, a _____________, and a ___________ area. * Insects have _____ legs connected to the chest part. * Some insects’ legs are all the same size. Some insects have one pair of legs larger than the other two pairs. * A grasshopper has one pair of legs larger than the other two pairs. These larger legs are used for ____________. Longer back legs * Insects eat a lot, so they grow very fast. As they grow, insects may molt and grow new ___________, or they may change completely. * A huge change in appearance is called ________. * There are two kinds of metamorphosis: ______________ and ______________. * In complete metamorphosis, insects like butterflies and moths have _______ stages of development. * The first stage makes an ________. * During the second stage, the egg hatches and a _________ comes out. * A caterpillar is the larva of an insect that will become a butterfly or a moth. * During the third stage, a ___________ is made. * A pupa is sometimes wrapped in a _____________ or in a _______________. * A cocoon is the pupa of a _____________. * A cocoon is made of ________. * A chrysalis is the pupa of a ___________. * In the last stage, the insect is finally an adult. * Incomplete metamorphosis happens in grasshoppers, termites, and dragonflies. * In incomplete metamorphosis, young animals that look like the ___________ hatch from eggs. * As the young animals grow, they keep _________, shedding their exoskeletons, and getting larger. Metamorphosis Simple or gradual -Three Changes - Egg - Nymph - 3 – 5 instars - Adult - Adults and nymphs eat the same food. * Most insects live alone. But, some insects are ___________ and cannot survive alone. * These insects live in ______________ or hives. * A colony is _____________________________ _______________________________________ * An amazing example of a colony is a __________. * A beehive is ___________________________. * All insects must protect themselves. * Bees and wasps have _______________ to protect themselves. * Many other insects use ______________. * Camouflage allows an insect to hide by ___ _______________________________.