Biology Chapter 28

1. Biology Chapter 28 Arthropods and Echinoderms Section 1 Introduction to Arthropods

2. Section One – Introduction to Arthropods • Arthropods are insects, spiders, crabs, centipedes • Characteristics of Arthropods • Segmented body • Tough 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 antennae

3. Section One – Introduction to Arthropods • Evolution of Arthropods • Primitive arthropods - many identical segments each carrying a pair of appendages (ex. trilobite)

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

5. Section One – Introduction to Arthropods • Respiration • Most 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.

6. Section One – Introduction to Arthropods • Respiration • Other 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

7. Section One – Introduction to Arthropods • Circulation • Open Circulatory System • heart pumps blood through arteries that branch and enter the tissues • Blood leaves blood vessels and moves through sinuses or cavities – collects in a large sinus surrounding the heart & re-enters the heart

8. Section One – Introduction to Arthropods • Excretion • Most terrestrial arthropods – Malpighian tubules (saclike organs that extract wastes from blood & add them to digestive wastes - dispose of nitrogenous wastes • In aquatic arthropods - diffusion moves wastes from the body into the surrounding water.

9. Section One – Introduction to Arthropods • Response • Most 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 wings • Most arthropods have sophisticated sense organs • compound eyes – may have more than 2000 separate lenses – can detect color and motion very well

10. Section One – Introduction to Arthropods • Movement   • move 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.

11. Section One – Introduction to Arthropods • Reproduction    • 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.

12. Section One – Introduction to Arthropods • Growth and Development in Arthropods • Molting • Arthropods outgrow their exoskeletons - – shedding entire exoskeleton and manufacturing a larger one to take its place • Controlled by endocrine system; most molt several times • Vulnerable to predators post molt – shell is soft • Skin glands digest inner part of exoskeleton; other glands secrete a new skeleton • When new exoskeleton is ready, animal pulls itself out of what remains of original skeleton

13. Section 2 – Groups of Arthropods • Classifying Arthropods • Number of body segments • Structure of body segments • Number of appendages • Structure of appendages • Appendages – mouthparts in particular • Three major groups of arthropods • Crustaceans • Insects and their relatives • Spiders and their relatives

14. Section 2 – Groups of Arthropods • Crustaceans – Subphylum Crustacea • Primarily aquatic • Includes crabs, shrimp, lobsters, crayfish & barnacles • Crustacean Characteristics • Two pair of antennae • Two or three body sections • Chewing mouthparts - mandibles

15. Section 2 – Groups of Arthropods

16. Section 2 – Groups of Arthropods • Spiders and their relatives – Subphylum Chelicerate • Includes spiders, ticks, scorpions, horseshoe crabs, mites • Chelicerate Characteristics • Have mouthparts called chelicerae • Two body sections • Four pairs of walking legs (eight legs total) • Lack antennae

17. Section 2 – Groups of Arthropods • Chelicerate Anatomy • Two appendages near mouth adapted as mouthparts • Chelicerae – fangs; used to stab and paralyze prey • Pedipalps- longer than chelicerae; used to grab prey • Respire using book lungs or book gills

18. Section 2 – Groups of Arthropods Chelicerate Anatomy

19. Section 2 – Groups of Arthropods • Groups of Chelicerates – Two Classes • Merostomata – horseshoe crabs • Oldest living arthropods – 500 million years • chelicerae, • 5 pairs of walking legs • long spike-like tail

20. Section 2 – Groups of Arthropods • Groups of Chelicerates – Two Classes (Cont.) • Arachnida – spiders, mites, ticks, scorpions • Arachnid Feeding: • Capture and feed on animals ranging from other arthropods to small birds • Webs made of a strong, flexible protein (silk) used to catch flying prey • Stalk and pounce on their prey • Lie in wait & leap out to grab insects that venture too near • Spiders do not have jaws for chewing  liquefy their food to swallow it • Once spider captures prey  uses fanglike chelicerae to inject paralyzing venom into it

21. Section 2 – Groups of Arthropods • Silk Production • All 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.

22. Section 2 – Groups of Arthropods Chelicerate Anatomy

23. Section 2 – Groups of Arthropods • Mites and Ticks • Small arachnids, often parasitic • Chelicerae & pedipalps specialized for digging into host’s tissues and sucking out blood or plant fluid • Ticks can transmit bacteria that cause serious diseases

24. Section 2 – Groups of Arthropods Lyme Disease

25. Section 2 – Groups of Arthropods • Scorpions • Scorpions inhabit warm areas around the world. • Scorpions have pedipalps that are enlarged into claws • Scorpions chew their prey

26. Section 2 – Groups of Arthropods • Insects and their relatives – subphylum uniramia • jaws, one pair of antennae, and unbranched appendages. • Centipedes • from 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

27. Section 2 – Groups of Arthropods • Insects and their relatives – subphylum uniramia (continued) • Millipedes • highly segmented body • segments bear two pairs of legs • defend themselves by rolling up into a ball or secreting unpleasant or toxic chemicals • feed on dead and decaying plant material

28. Section 3 Insects • Class Insecta contains more species than any other group of animals • Insects have a body divided into three parts—head, thorax, and abdomen. Three pairs of legs are attached to the thorax.

29. Section 3 Insects

30. Section 3 Insects • Insects 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

31. What Is an Insect? • Responses to Stimuli • Compound eyes made up of many lenses detect minute changes in color and movement. • The brain assembles information from the eye and directs the insect’s 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.

32. What Is an Insect? • Adaptations for Feeding • Insects have three pairs of appendages that are used as mouthparts, including a pair of mandibles.  Mandibles used to saw and grind food

33. What Is an Insect? • Adaptations for Feeding • Insect mouthparts are specialized for feeding. • Many insects produce saliva containing digestive enzymes that help break down food. Tubelike mouthpart used to suck nectar

34. What Is an Insect? • Specialized Mouthparts Spongelike mouthpart used to lap up food

35. What Is an Insect? • Movement and Flight • Insects 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.

36. What Is an Insect? • Metamorphosis • The 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.

37. What Is an Insect? • Incomplete metamorphosis • Immature 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.

38. Incomplete Metamorphosis Nymph Nymph Nymph

39. What Is an Insect? • Complete Metamorphosis • In 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 pupa—the stage in which an insect changes from larva to adult.

40. Complete Metamorphosis

41. Insects and Humans • Insects and Humans • Many 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.

42. Insects and Humans • Insects 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.

43. Insect Communication • Insect Communication • Insects communicate using sound, visual, chemical, and other types of signals. • Much of their communication involves finding a mate.

44. Insect Communication • Visual Cues • Male 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.

45. Insect Communication • Chemical Signals • Many 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.

46. Insect Societies • Insect Societies • Ants, 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.

47. Insect Societies • Castes • Within 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 • workers • Most insect societies have only one queen.

48. Insect Societies • A tropical leaf-cutter ant colony is one example of an insect society.  • Individuals in the colony have specific tasks or roles. • Major Workers • Minor Workers • Queen • Soldiers

49. Insect Societies • Communication in Societies • Each 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.

50. Insect Societies • The round dance indicates that food is fairly close to the hive.