Biology Chapter 28

Biology Chapter 28Arthropods and Echinoderms

Section 1 Introduction to ArthropodsSection One Introduction to ArthropodsArthropods are insects, spiders, crabs, centipedesCharacteristics of ArthropodsSegmented bodyTough exoskeleton external covering, made of chitin differ b/t animals (hard like crabs, waxy, water retaining)Jointed appendages structures that extend from body wall, such as legs and antennaeSection One Introduction to ArthropodsEvolution of ArthropodsPrimitive arthropods - many identical segments each carrying a pair of appendages

(ex. trilobite)

Section One Introduction to ArthropodsEvolution of ArthropodsTodays Arthropodsfewer body segments most have 2-3 segmentshighly specialized appendages feeding, movement & other functions (ex. antennae, flippers, wings, legs, claws, tails, etc.)Form and Function in ArthropodsArthropods include herbivores, carnivores, and omnivores; filter feeders, detritivores, and parasites.mouthparts of arthropods are adapted to the type of food the arthropod eats.

Section One Introduction to ArthropodsRespirationMost terrestrial arthropods tracheal tubes branching network extends throughout the body. Air enters and leaves tubes through spiracles - small openings located along the side of the body.

Section One Introduction to ArthropodsRespirationOther terrestrial arthropods book lungs organs that have layers of stacked respiratory tissue (ex. spiders)Most aquatic arthropods gills ex. lobsters and crabs featherlike gills & horseshoe crabs book gills

Section One Introduction to ArthropodsCirculationOpen Circulatory Systemheart pumps blood through arteries that branch and enter the tissuesBlood leaves blood vessels and moves through sinuses or cavities collects in a large sinus surrounding the heart & re-enters the heart

Section One Introduction to ArthropodsExcretionMost terrestrial arthropods Malpighian tubules (saclike organs that extract wastes from blood & add them to digestive wastes - dispose of nitrogenous wastesIn aquatic arthropods - diffusion moves wastes from the body into the surrounding water.

Section One Introduction to ArthropodsResponseMost arthropods have a well-developed nervous system. All arthropods have a brain. Two nerves connect the brain to a ventral nerve cord along nerve cord are several ganglia (groups of nerve cells) ganglia coordinate movements of individual legs and wingsMost arthropods have sophisticated sense organs compound eyes may have more than 2000 separate lenses can detect color and motion very well

Section One Introduction to ArthropodsMovementmove using well-developed groups of muscles - coordinated and controlled by the nervous system.muscles generate force by contracting and then pulling on the exoskeleton.At each body joint, different muscles either flex (bend) or extend (straighten) the joint.

Section One Introduction to ArthropodsReproduction Terrestrial arthropods have internal fertilization. Two ways - males deposit sperm inside females. males deposit a sperm packet that is picked up by the females. Aquatic arthropods may have internal or external fertilization.

Section One Introduction to ArthropodsGrowth and Development in ArthropodsMoltingArthropods outgrow their exoskeletons - shedding entire exoskeleton and manufacturing a larger one to take its placeControlled by endocrine system; most molt several timesVulnerable to predators post molt shell is softSkin glands digest inner part of exoskeleton; other glands secrete a new skeletonWhen new exoskeleton is ready, animal pulls itself out of what remains of original skeleton

Section 2 Groups of ArthropodsClassifying Arthropods Number of body segmentsStructure of body segmentsNumber of appendagesStructure of appendagesAppendages mouthparts in particular

Three major groups of arthropodsCrustaceansInsects and their relativesSpiders and their relativesSection 2 Groups of ArthropodsCrustaceans Subphylum CrustaceaPrimarily aquaticIncludes crabs, shrimp, lobsters, crayfish & barnaclesCrustacean CharacteristicsTwo pair of antennaeTwo or three body sectionsChewing mouthparts - mandiblesSection 2 Groups of Arthropods

Section 2 Groups of ArthropodsSpiders and their relatives Subphylum ChelicerateIncludes spiders, ticks, scorpions, horseshoe crabs, mitesChelicerate CharacteristicsHave mouthparts called cheliceraeTwo body sectionsFour pairs of walking legs (eight legs total)Lack antennae

Section 2 Groups of ArthropodsChelicerate AnatomyTwo appendages near mouth adapted as mouthpartsChelicerae fangs; used to stab and paralyze preyPedipalps- longer than chelicerae; used to grab preyRespire using book lungs or book gillsSection 2 Groups of ArthropodsChelicerate Anatomy

Section 2 Groups of ArthropodsGroups of Chelicerates Two ClassesMerostomata horseshoe crabsOldest living arthropods 500 million yearschelicerae, 5 pairs of walking legs long spike-like tail

Section 2 Groups of ArthropodsGroups of Chelicerates Two Classes (Cont.)Arachnida spiders, mites, ticks, scorpionsArachnid Feeding:Capture and feed on animals ranging from other arthropods to small birdsWebs made of a strong, flexible protein (silk) used to catch flying preyStalk and pounce on their preyLie in wait & leap out to grab insects that venture too nearSpiders do not have jaws for chewing liquefy their food to swallow itOnce spider captures prey uses fanglike chelicerae to inject paralyzing venom into it

Section 2 Groups of ArthropodsSilk ProductionAll spiders produce silk. Spiders spin silk into webs, cocoons for eggs, and wrappings for prey. They do this by forcing liquid silk through spinnerets, which are organs that contain silk glands.

Section 2 Groups of ArthropodsChelicerate Anatomy

Section 2 Groups of ArthropodsMites and TicksSmall arachnids, often parasiticChelicerae & pedipalps specialized for digging into hosts tissues and sucking out blood or plant fluidTicks can transmit bacteria that cause serious diseases

Section 2 Groups of ArthropodsLyme Disease

Section 2 Groups of ArthropodsScorpionsScorpions inhabit warm areas around the world.Scorpions have pedipalps that are enlarged into clawsScorpions chew their prey

Section 2 Groups of ArthropodsInsects and their relatives subphylum uniramiajaws, one pair of antennae, and unbranched appendages.Centipedesfrom a few to more than 100 pairs of legs.most body segments bear one pair of legs each.carnivores; mouthparts contain venomous claws that they use to catch and stun or kill their prey

Section 2 Groups of ArthropodsInsects and their relatives subphylum uniramia (continued)Millipedeshighly segmented bodysegments bear two pairs of legsdefend themselves by rolling up into a ball or secreting unpleasant or toxic chemicalsfeed on dead and decaying plant material

Section 3 InsectsClass Insecta contains more species than any other group of animalsInsects have a body divided into three partshead, thorax, and abdomen. Three pairs of legs are attached to the thorax.

Section 3 Insects

Section 3 InsectsInsects have a segmented body, an exoskeleton, and jointed appendages.A typical insect also has: a pair of antennae a pair of compound eyes two pairs of wings on the thorax tracheal tubes that are used for respiration

What Is an Insect?Responses to StimuliCompound eyes made up of many lenses detect minute changes in color and movement. The brain assembles information from the eye and directs the insects response. Insects have chemical receptors for taste and smell on their mouthparts, antennae, and legs.Insects have sensory hairs that detect movements in the surrounding air or water.Many insects also have well-developed ears.

31What Is an Insect?Adaptations for FeedingInsects have three pairs of appendages that are used as mouthparts, including a pair of mandibles.

Mandibles used to saw and grind food

32What Is an Insect?Adaptations for FeedingInsect mouthparts are specialized for feeding.Many insects produce saliva containing digestive enzymes that help break down food.

Tubelike mouthpart used to suck nectar33What Is an Insect?

Specialized Mouthparts

Spongelike mouthpart used to lap up food34Insect mouthparts are specialized for a variety of functions. Flies have a spongy mouthpart that is used to stir saliva into food and then lap up the food. What Is an Insect?Movement and FlightInsects have three pairs of legs, which are used for walking, jumping, or capturing and holding prey.The legs of many insects have spines and hooks that are used for grasping and defense.Flying insects typically have two pairs of wings made of chitin.Flight has allowed insects to disperse long distances and to colonize a wide variety of habitats.

35What Is an Insect?MetamorphosisThe growth and development of insects usually involve metamorphosis, which is a process of changing shape and form. Insects undergo either incomplete metamorphosis or complete metamorphosis.36What Is an Insect?Incomplete metamorphosisImmature insects that undergo incomplete metamorphosis look very much like the adults. These immature forms are called nymphs. Nymphs lack functional sexual organs and other adult structures, such as wings. Nymphs gradually acquire adult structures as they molt and grow.37Incomplete Metamorphosis

Nymph Nymph Nymph 38What Is an Insect?Complete MetamorphosisIn complete metamorphosis, animals hatch into larvae that look and act nothing like their parents.They feed and grow rapidly and molt a few times.They undergo a final molt and change into a pupathe stage in which an insect changes from larva to adult.39Complete Metamorphosis

40Insects and HumansInsects and HumansMany insects are known for their negative effects.Termites destroy wood structures. Desert locusts cause billions of dollars in damage to livestock and crops.Mosquitoes can infect humans with microorganisms that cause disease.

41Insects and HumansInsects also contribute to the richness of human life.One third of the food you eat depends on plants pollinated by animals and insects. Insects produce silk, wax, and honey. They are considered a food delicacy in certain countries of Africa and Asia.42Insect CommunicationInsect CommunicationInsects communicate using sound, visual, chemical, and other types of signals. Much of their communication involves finding a mate.

43Insect CommunicationVisual CuesMale fireflies use visual cues to communicate with potential mates.A light-producing organ in the abdomen is used to produce a distinct series of flashes. When female fireflies see the signal, they flash back a signal of their own, inducing the males to fly to them.

44Insect CommunicationChemical SignalsMany insects communicate using chemical signals. The chemicals are called pheromones.Pheromones are specific chemical messengers that affect the behavior or development of other individuals of the same species. Some pheromones function to signal alarm or alert other insects to the death of a member of the colony.Other pheromones enable males and females to communicate during courtship and mating.

45Insect SocietiesInsect SocietiesAnts, bees, termites, and some of their relatives form complex associations called societies.A society is a group of closely related animals of the same species that work together for the benefit of the whole group.

46Insect SocietiesCastesWithin an insect society, individuals may be specialized to perform particular tasks, or roles. These are performed by groups of individuals called castes. Each caste has a body form specialized for its role. The basic castes are: reproductive females (queens) reproductive males workersMost insect societies have only one queen.

47Insect SocietiesA tropical leaf-cutter ant colony is one example of an insect society.Individuals in the colony have specific tasks or roles.Major WorkersMinor WorkersQueenSoldiers

48Insect SocietiesCommunication in SocietiesEach species of social insect use visual, touch, sound, and chemical signals to communicate information among members of the colony.Honeybees communicate information about food through a series of complex movements.

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Insect SocietiesThe round dance indicates that food is fairly close to the hive.50Bees use dances to communicate information about food sources. The round dance indicates that food is fairly close to the hive. Insect SocietiesThe waggle dance indicates that food is farther away from the hive. It also indicates the direction of the food.

51Bees use dances to communicate information about food sources. The waggle dance indicates that food is farther away. It also indicates the direction of the food.