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  1. 1. By: Michelle A. Salvador
  2. 2. Etymology - From the Greek Arthron a joint and Pous for foot
  3. 3. Arthropod, animal with a hard, outer skeleton and a jointed body and limbs. Arthropods make up a phylum of invertebrates that includes insects, such as ants, beetles, and butterflies; crustaceans, such as lobsters, shrimps, and crabs; and arachnids, including scorpions, spiders, and ticks. In terms of sheer numbers and the variety of niches they fill, arthropods are the most successful animals on Earth. More than one million arthropod species have been identified—more than 20 times the number of known fish, amphibian, reptile, bird, and mammal species combined. This figure is considered a low estimate of the phylum's actual size because many arthropod species have yet to be discovered and documented. Some scientists suggest the number of arthropod species in tropical forests alone may approach six million to nine million.
  4. 4. Arthropods: A success story •Almost any way you look at them, arthropods are successful: They have been around for more than 500 million years and are still evolving. •They live on Earth in overwhelming numbers. •There have come in all shapes and sizes. •They have evolved to fill a variety of ecological niches — from tiny internal parasite to giant bird-eating predator. But what is it about arthropods that has made them so successful? Let's begin our investigation by reviewing what an arthropod is.
  5. 5. Bilateral (left/right) symmetry Two Matching Sides Many animals have a body form that is symmetrical, meaning that it could be divided into matching halves by drawing a line down the center. In this respect, arthropods are built like humans are; the right half of an arthropod is a mirror image of its left half — this is called bilateral symmetry (bi = two, latus = side). Other animals have symmetry like a snowflake’s — there are many different ways to carve it into matching halves, and all of these lines meet in the middle, dividing it up like a birthday cake. That is called radial symmetry. Other animals are not symmetrical at all — their bodies cannot be divided into similar halves with a straight line.
  6. 6. Segmented body Like Cars in a Train At some point in their lives, all arthropods have bodies that are internally and externally segmented. These segments piggyback on one another, like a series of cars in a train. Each body segment tends to repeat the same suite of structures (for example, a pair of legs, a set of breathing organs, and a set of nerves), often with slight variations down the length of the animal. Usually, sets of segments are grouped into a larger unit, such as the abdomen.
  7. 7. Hard exoskeleton Arthropod Armor The bodies of arthropods are supported, not by internal bones, but by a hardened exoskeleton made of chitin, a substance produced by many non-arthropods as well. In arthropods, the nonliving exoskeleton is like a form- fitting suit of armor. It is produced by the "skin" and then hardens into a protective outer-covering. This exoskeleton is handy in some ways (it provides protection and prevents water loss), but is limiting in others. In order to grow, all arthropods must shed the exoskeleton and produce a new, larger one.
  8. 8. •Jointed legs •Many pairs of limbs
  9. 9. Other characteristic •Body cavity a true coelom. •Most possesses a through straight gut with an anus (in most cases). •Body possesses an external skeleton (in most cases). •Nevous system includes a brain and ganglia. •Possesses a respiratory system in the form of tracheae and spiracles (in most cases). •Possesses an open circulatory system with a heart (in most cases). •Feed on everything. •Live everywhere. •Body are divided into three, head, thorax, and abdomen
  10. 10. The five branches of the arthropod tree Modern arthropods include insects, spiders, centipedes, shrimp, and crayfish. All arthropods are the descendents of a single common ancestor. Just as you and your biological cousins can trace your ancestry back to a common set of grandparents, all arthropods can trace their ancestry back to a common arthropod ancestor. Any species descended from that ancestor is an arthropod. And any species not descended from that ancestor is not an arthropod.
  11. 11. Life Cycle and Reproduction In most instances, both sexes of arthropods occur separately. Males commonly pass sperm to females in sealed packets called spermatophores. The males lay these packets on the ground, and the females later pick them up, or the male deposits them into the female's genital opening. Among crustaceans, millipedes, spiders, mites and some insects, males transfer sperm directly to females.
  12. 12. Fertilized arthropod eggs hatch after days, weeks, months, and even years. Most species deposit their eggs externally, but some species hatch their eggs internally, bearing live young. In many species, such as spiders, the hatchlings look like miniature adults. The larvae of other arthropod species have little or no physical resemblance to adults. For example, caterpillars are quite distinct from the butterflies that they become as adults. These larvae, in the process of metamorphosis, pass through a series of distinct phases to become adults. Larvae may also inhabit different environments and eat different foods than their parents. The life spans of arthropods range from a few weeks to several decades.
  13. 13. Arthropods Evolution The evolutionary origins of modern arthropods are unclear and complex. It is generally accepted that the phylum is polyphyletic—that is, derived from several separate ancestral lines. The ancestors of arthropods were ancient aquatic segmented worms, similar to present-day annelids, although the fossil evidence is sketchy. The ancient seas of the Cambrian and Ordovician periods (570 million to 435 million years ago) were teeming with aquatic arthropods, especially trilobites.
  14. 14. During the Silurian and Devonian periods (435 million to 360 million years ago), the arthropods were among the first animals to leave the water and colonize the land. When they emerged from the water, they had few, if any, competitors. They swiftly adapted to the demands of terrestrial life, occupying new niches as predators, plant eaters, parasites, and decomposers. The earliest terrestrial arthropod fossil is of a scorpion-like arachnid. The earliest insect fossils come from a few million years later. These early terrestrial arthropods sometimes reached great size, much larger than any land arthropods known today.
  15. 15. Scientists have found evidence that Earth’s atmosphere had more oxygen (perhaps as high as 40 percent compared to 21 percent in our modern world). Higher oxygen pressure would have enabled animals with relatively primitive breathing systems, such as those found in land arthropods, to be active even in very large animals. By the end of the Carboniferous period (360 million to 290 million years), four-legged vertebrates (amphibians and reptiles) dominated the land and used arthropods as a major source of food.
  16. 16. Crustaceans
  17. 17. Crustacean, common name for any of a group of mainly aquatic arthropod invertebrates, including the crab, lobster, and shrimp. They are among the most successful animals, abundant in the sea much as insects are on land. The majority of animals in the world are marine crustaceans that belong to the copepod subclass of the crustacean subphylum. Crustaceans are also successful in fresh water, and a few, such as sow bugs, are common in moist land environments. Although most crustaceans are small, they vary widely in form and include such large members as lobsters up to 60 cm (24 in) long and a spider crab with a leg span of 3.6 m (12 ft). The subphylum contains about 26,000 known species.
  18. 18. Some Characteristics of Crustaceans: •A hard exoskeleton made of calcium - no internal skeleton. •The head has two compound eyes, two pairs of antennae, and three pairs of mouthparts. •A pair of green glands excrete wastes near the base of antennae. •The abdominal segments have swimmerets (swimming legs) •The sexes are separate. Eggs are attached to the swimmerets (swimming legs) of the female. The first pair is enlarged in the male (it is used to pass sperm to the female). •The tail is fan-shaped, and ends in uropods and a telson. •The circulatory system is open; there is no heart and the "blood" is pumped by vessels into sinuses, and does not flow in a closed loop). •The nervous system consists of a primitive ventral nerve cord and ganglia system (similar to those of an earthworm).
  19. 19. Generalized Anatomy of a Crustacean Crustacean anatomy is characterized by an external skeleton and a segmented body. In different crustacean species these segments and the accompanying limbs have evolved into specialized appendages for respiration, swimming, crawling, and feeding. The extended inner cavity contains the digestive and nervous systems.
  20. 20. Reproduction Sexual Reproduction Usually the sexes are separate, but some parasites and most barnacles, which have difficulty obtaining mates, are simultaneous hermaphrodites (male and female at the same time). This increases the number of possible partners and may allow self- fertilization as a last resort. Some crustaceans switch sex as they get older. Many crustaceans exhibit elaborate courtship behavior, and the males may fight for the chance to mate.
  21. 21. The young of marine crustaceans generally pass through one or more larval stages that are quite unlike the adult form. Often the larvae swim in open water to find a place to live. Freshwater and terrestrial crustaceans skip the larval stage, except for those that return to the sea to spawn. After fertilization, the developing eggs are generally cared for by the mother until they have reached the larval or postlarval condition. Otherwise, little parental care exists among crustaceans. Some live in male-female pairs or are gregarious, but they do not form well-organized societies. The smallest crustaceans live for just a few days, but the largest ones may live for decades.
  23. 23. KRILL Krill, common name for small, shrimplike crustaceans that swarm in dense shoals, especially in Antarctic waters. Most of the approximately 90 species range in length from 8 to 70 mm (0.3 to 2.8 in) and use their feathery legs for straining out the tiny diatoms on which they live; many emit a strong blue-green light that probably helps them congregate and spawn. Krill inhabit open seas and are an important link in the food web. They are eaten by fish, birds, and especially baleen whales, which consume as much as 2000 kg (4400 lb) of krill in one feeding. Shoals of the crustaceans have densities of 20 kg per cu m (35 lb per cu yd); some species remain near the surface and others are found as deep as 2000 m (6500 ft).
  24. 24. SHRIMPS AND PRAWNS Shrimp, any of about 2,000 species of small, aquatic animals related to crabs, lobsters, and crayfish. Shrimp range in size from animals not much bigger than a fingernail to ones over 20 cm (8 in) long. Larger species are often known as prawns, although many people interchange the two names for all species.
  25. 25. Body of a Shrimp A shrimp has a long, thin, semitransparent body. Five pairs of jointed legs on the abdomen are used like paddles to swim. Rapid flicks of a fanlike tail help the animal move quickly to avoid predators.
  26. 26. REPRODUCTION In shrimp reproduction, the male deposits sperm into a gelatinous mass produced by the female and located between her fourth pair of walking legs. The female then lays eggs, in batches of up to 15,000 at a time. The sperm fertilizes the eggs. Females usually care for the fertilized eggs in a brood chamber found on the underside of her tail. In some species, the eggs are scattered in the water and left to develop on their own. As with crabs and lobsters, the eggs hatch to produce drifting larvae. The larvae change shape as they grow, developing an adult body after molting their skin several times (see Metamorphosis). Once the change in shape is complete (from 30 to 160 days, depending on the species), the young shrimp are sexually mature and able to breed. The life spans of shrimp vary among species--some die once they have bred, but others live for six or seven years.
  27. 27. Cleaner shrimp Cleaner shrimp Imperial shrimp Fairy shrimp
  28. 28. Lobster Lobster, common name for marine decapod (that is, with five pairs of appendages on the thorax) crustaceans closely related to the freshwater crayfishes.
  29. 29. CRAB Common name for any of a group of crustaceans characterized by a reduced abdomen and an enlarged and broadened anterior portion of the body. Although most common as bottom dwellers in the sea, crabs also occur in fresh water, and some venture onto land. Crabs are divided into two groups: true crabs (about 4500 species) and hermit crabs and their allies (about 1400 species).
  30. 30. REPRODUCTION AND LIFE CYCLE All crab species have separate sexes. In many species, mating occurs only when the female has just molted and her new shell is not yet hard. (So-called soft-shell crabs, a delicacy, are simply crabs in this transitional molting stage.) The eggs are held in a brood pouch and pass through two larval stages before they hatch into tiny larvae, which swim about in the water. In some species the larva first appears in a form called a zoea, which does not resemble the adult, and then in a more crablike stage called a megalops, in which the abdomen is still prominent. Each time the young crab molts, it increases its size considerably, but it is exposed to danger while it is still in its unprotected, soft state. Lost legs and chelae can be replaced when molting takes place. Crabs may live from 3 to 12 years.
  31. 31. Spider crab Coconut tree crab Sally lightfoot crab Hermit crab
  32. 32. CRAYFISH Crayfish, also crawfish, common name for any crustacean resembling but smaller than their relatives the lobsters, ranging in length from 2 to 40 cm (0.8 to 16 in); the first of their five pairs of walking legs is equipped with strong claws. Crayfish live in freshwater rivers and streams in temperate climates; one family is confined to the northern hemisphere, another to the southern hemisphere, and a third to the Australian region..
  33. 33. Crayfish usually burrow into the banks of streams or ponds and feed upon live or decaying animal or vegetable matter. The male inserts sperm into a receptacle in the female's thorax in the fall; the eggs, laid in the spring, are then fertilized and hatch in eight weeks or less. The young remain with the mother for a short while; after several molts, they reach adult size. The animals can live for three years or longer. The white-clawed crayfish is particularly prized for food despite its small size. Some cave-dwelling crayfish species are blind, such as those of Kentucky's Mammoth Cave. Like other crustaceans, crayfish are capable of regenerating lost limbs during molting.
  34. 34. BARNACLES Barnacle, popular name for members of a subclass of sessile crustaceans. The name was originally applied to the barnacle goose of northern Europe, and its transfer to these crustaceans was due to the fable that the bird develops from the stalked, or goose, barnacle.
  35. 35. Most barnacles are hermaphrodites . All inhabit salt water. The larvae are free-swimming, but the adults are always permanently attached to foreign objects, such as ship bottoms, wharf piles, rocks, floating timbers, whales, large fish, and shellfish. The subclass is divided into five orders, four of which are minute forms parasitic on other shellfish. The other order includes the acorn barnacles, common to temperate and cold waters, and the stalked barnacles, which are usually found in warm waters, but, because they attach themselves to ships, they are distributed throughout the world.
  36. 36. Arachnids
  37. 37. Arachnid, term for animals in the class including the scorpions, spiders, daddy longlegs, mites, and ticks, and certain other eight-legged land invertebrates. Fossils suggest that arachnids were among the first animals to live on land, perhaps in the early Devonian Period, nearly 400 million years ago. About 60,000 species are known, although many, especially mites, remain undiscovered or undescribed. Arachnids are found throughout the world in nearly every habitat, but they reach their greatest size and diversity in warm arid and tropical regions.
  38. 38. CHARACTERISTICS The arachnid body is divided into two parts: anterior and posterior. The anterior part, called the cephalothorax, contains sense organs, mouthparts, and limbs in pairs. The first pair of limbs—the chelicerae—may form pincers or poison fangs, and the second pair—the pedipalps—may serve as pincers, feelers, or legs. The other limb pairs, generally four, are used for walking. The posterior part of the body, the abdomen, bears the genital opening and other structures. It is usually equipped with modified gills called book lungs. Most arachnids are solitary except at the time of mating, when a variety of complex behavior patterns may be observed. Females may guard eggs or young, which are often born live.
  39. 39. Scorpions Ticks Daddy longlegs Spiders Mites
  40. 40. SCORPIONS Scorpion, common name for arachnid having a flat, narrow body, two lobsterlike claws, eight legs, and a segmented abdominal tail. Terminating in a venomous stinger supplied by a pair of poison glands, the tail is usually curved upward and forward over the back. About 1400 species of scorpion exist; about 40 of them occur in the United States. Scorpions are usually brown in color and range from about 2.5 to 20 cm (about 1 to 8 in) in length.
  41. 41. SPIDERS Spider(arthropod), any of a large group of invertebrates (animals without backbones) that have spinning glands used to produce silken threads and webs. There are about 40,000 species of spiders. Spiders are found worldwide, except for in the oceans, and they live in all habitats and at most elevations.
  42. 42. Spiders have 8 appendages. The first pair are used for holding the prey and feeding. The second pair may also be used for holding and killing their prey. The others are used as legs for walking. Most spiders also have 8 eyes. Spiders have fangs that are used to inject poison to paralyze or kill their prey. Many spiders can produce silk threads to spin webs for catching prey, and for building cocoons for their eggs.
  43. 43. Let’s watch a video about spiders
  44. 44. Spider Fangs The fang-bearing appendages, or chelicerae, of most spiders swing inward from the side to grasp prey. In some larger spiders, however, the chelicerae swing downwards, pinning the prey underneath.
  45. 45. LIFE CYCLE The life cycle of the spider consists of four stages: egg, larva, young spider, known as a nymph or spiderling, and adult. Like insects, spiders grow only by molting, a process that involves periodically shedding their exoskeleton. In each molting stage, young spiderlings resemble tiny adults, a process known as incomplete metamorphosis.
  46. 46. COURTSHIP AND MATING Spiders become sexually mature after their last molt, at which time females have developed functional ovaries and males have mature testes. In most spider species the male courts the female before mating occurs. After a male spider has filled its palps with sperm cells, he begins searching for a female. A male begins by identifying himself to a female so that she does not mistake him for potential prey. In some spiders, such as American tarantulas, this identification process involves the male repeatedly touching the female. More often, a male courting a female communicates with her over larger distances using vibrations. For instance, a male wolf spider uses its legs to drum on the ground. In some web spiders, the male attaches a special signal thread to the female’s web. The male then drums or plucks the thread in a rhythm that indicates the vibration is caused by another spider of the same species and not by an ensnared insect. If a female is ready to accept a courting male, she may send signals back to him.
  47. 47. Locating the right female can be tricky for a male spider. Fortunately, female spiders produce certain chemical substances known as pheromones that aid spider courtship. A female may release these pheromones through the air (like a perfume) or she may deposit them on her silk threads. When a male spider encounters pheromones from a female of the same species, he becomes excited, even if the female is not present.
  48. 48. Spiders with better eyesight may rely mostly on visual signals during courtship. When a male notices a female, he starts a zigzag dance in front of her in which he raises his front legs, vibrates his palps, and twitches his abdomen. Each species uses a different courtship dance with unique movements. A female will only accept a male who performs a dance with movements specific to that species.
  49. 49. When a male finds an interested female, he inserts his sperm-containing palp into the female’s genital opening. The process of mating can be very brief (a matter of seconds), or it can last several hours, depending on the species. In most species both sexes separate peacefully after mating. Contrary to popular belief, the female black widow spider does not kill her partner after mating. Depending on the species, a female may mate only once or she may mate with several males during her lifetime.
  50. 50. Typically the female lays her fertilized eggs in a silky case called a cocoon, which provides a protective and insulating environment for the developing spiders. Many females abandon their cocoons right after they deposit their eggs, although they may camouflage them or hang them in hidden locations. Other spiders guard and defend their cocoon until the eggs hatch.
  51. 51. Young Garden Spiders Hatching All spiders lay eggs in some sort of silk-wrapped cocoon. The female may then abandon the cocoon or guard it from predators. In some species of spiders, the female carries the cocoon with her until the eggs hatch.
  52. 52. TYPES OF WEB Orb Web The orb web has a circular shape. This type of web is used to catch large flying insects, like the butterfly pictured here.
  53. 53. Net Web Netcasting spiders like this Australian species manipulate a small web between their front legs. To catch its prey, the spider uses the web as a net, stretching it over a doomed insect.
  54. 54. Funnel Web The web of the funnel spider is built above the ground and oriented so it will intercept flying insects. Funnel spiders design their webs with a small opening, or funnel, at the bottom, in which the spider lies in wait.
  56. 56. Trap-Door Spider This trap-door spider emerges from its burrow through a doorway surrounded by leaves. Trap-door spiders are various species of large tropical spiders that live in self- constructed underground lairs with carefully hidden entrances. These spiders come out of their homes to eat ants and insects, and are harmless to humans.
  59. 59. TICKS Tick, common name for members of a group of large mitelike arachnids parasitic on mammals, birds, and reptiles. All ticks are bloodsucking parasites. Ticks are found in most parts of the world but are generally limited to those habitats frequented by their hosts—namely, woods, tall grass, and shrubby vegetation—where they climb onto plants and wait to jump on a passing host.
  60. 60. MITES Mite, common name for some 30,000 species of minute, usually oval-bodied arachnids. They are worldwide in distribution. Mites resemble ticks in having the head, thorax, and abdomen fused into one unsegmented body, but they are usually much smaller. They often have three pairs of legs in the larval stage and four pairs of legs in the nymph and adult stages. The mouthparts are adapted for piercing. Like most arachnids, mites breathe by means of tracheae (small tubes opening on the surface of the body), and they live in both aquatic and terrestrial habitats. Many are animal parasites; some, which subsist on vegetation, produce galls on plants. They are economically and medically injurious, because they carry diseases affecting livestock and humans.
  62. 62. DADDY LONGLEGS Daddy Longlegs, common name for any of a group of spiderlike arachnids, also called harvestmen or harvest spiders. Daddy longlegs resemble true spiders but have oval, segmented abdomens, only two eyes, and exceptionally long, slender legs. They feed on small insects, dead animals, or plant juices. They have very small mouthparts and do not harm humans. Daddy longlegs often congregate in large numbers in caves or other sheltered places. The name is also applied to crane flies.
  63. 63. CENTIPEDES
  64. 64. Centipede, common name for the members of a class of the arthropod phylum. The centipedes are long, segmented animals with jointed appendages and a poisonous “bite” that in some species is dangerous to humans. Centipedes are often confused with millipedes, which constitute a separate class.
  65. 65. The centipede body is divided into well-marked segments, the number of which varies from 12 to more than 100. The head, which is covered by a flat shield above, bears a pair of antennae, usually of considerable length and consisting of from 12 to more than 100 joints; a pair of small, strong, toothed, and bristly mandibles; and a pair of underjaws, usually with palps. The next, limblike appendages are followed by a modified pair of legs with strong joints, terminating in a sharp claw into which a poison gland opens. These appendages are used for seizing and killing prey. The two legs on each other segment are usually seven-jointed, sometimes bearing spurs and glands, and are generally clawed.
  66. 66. Centipedes are nocturnal and remain under stones or wood during the day. They are all carnivorous. One genus bears live young; the others lay eggs..
  67. 67. Peruvian Centipede
  68. 68. MILLIPEDES
  69. 69. Millipede, any of about 1000 species of cylindrical, many- legged arthropods . Found worldwide, millipedes have segmented bodies with two pairs of legs on each of the 9 to 100 or more abdominal segments, depending on the species, and one pair on three of the four thoracic segments. Because of their numerous legs, the animals walk slowly, with a wavelike motion of the legs down the body. In length they range from about 0.2 to 23 cm (about 0.1 to 9 in). Millipedes have a hard protective layer of calcium-containing chitin (except in some small species), two simple eyes, one pair of mandibles, two short antennae, and (in most species) stink glands with secretions that repel or kill insect predators. Another protective strategy is to curl into a spiral or a ball when threatened. The animals live in dark, damp places and feed on decaying plant life, sometimes damaging crops but also enriching the soil. They grow by molting and may live for one to seven years.
  70. 70. INSECTS
  71. 71. Insect, small, air-breathing animal characterized by a segmented body with three main parts—head, thorax, and abdomen. In their adult forms, insects typically have three pairs of legs, one pair of antennae, and in most instances, two pairs of wings. Insect means "segmented" in Latin. There are about a million different types of insects and many more that have not been discovered yet.
  72. 72. REPRODUCTION AND METAMORPHOSIS A small number of insects give birth to live young, but for most insects, life starts inside an egg. Insect eggs are protected by hard shells, and although they are tiny and inconspicuous, they are often laid in vast numbers. A female house fly, for example, may lay more than 1,000 eggs in a two-week period. As with all insects, only a small proportion of her young are likely to survive, but when conditions are unusually favorable, the proportion of survivors shoots up, and insect numbers can explode. In the 1870s, one of these population explosions produced the biggest mass of insects ever recorded: a swarm of locusts in Nebraska estimated to be over 10 trillion strong.
  73. 73. Most insects undergo one of two varieties of metamorphosis: incomplete or complete. Dragonflies, grasshoppers, and crickets are among the insects that experience incomplete metamorphosis. In these insects, the differences between the adults and the young are the least marked. The young, which are known as nymphs (or naiads in the case of dragonflies), gradually develop the adult body shape by changing each time they molt, or shed their exoskeleton. A nymph's wings form in buds outside its body, and they become fully functional once the final molt is complete.
  74. 74. Insects that undergo complete metamorphosis include butterflies, moths, beetles, bees, and flies. Among these species the young, which are called larvae, look completely different from their parents, and they usually eat different food and live in different environments. After the larvae grow to their full size, they enter a stage called the pupa, in which they undergo a drastic change in shape. The body of a pupating insect is confined within a protective structure. In butterflies, this structure is called a chrysalis, and in some other insects the structure is called a chamber or a cocoon. The larva's body is broken down, and an adult one is assembled in its place. The adult then breaks out of the protective structure, pumps blood into its newly formed wings, and flies away..