Chapter 36 Arthropods 1

Arthropods

Chapter 36

722-735

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Objectives 36.1

• Describe the distinguishing characteristics of arthropods

• Explain the process of molting in an arthropod

• List the five major subphyla of the phylum arthropoda

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P. Arthropoda- “ jointed-foot”

Two-thirds of all animal species belong to the phylum Arthropoda. This phylum contains a variety of bilaterally symmetrical coelomates, including lobsters crabs, spiders, and insects. These animals have adapted to almost every environment on Earth

Holt cd- 2 segments

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characteristics

Appendages- legs, antennae, jointed extensions

Exoskeleton- protection and support

Made up of 3 layers secreted by the epidermis

1. Waxy outer layer- repels water, keeps from drying out

2. Middle layer- primary protection made up chitin (tough polysaccharide)

3. Inner layer- allows to move freely, flexible, muscles are attached

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characteristics

• Cephalization• Segmented antennae• Mouth parts• Compound eyes- many light detectors,

each has own lens• Open circulatory system• Molting- sheds exoskeleton and makes

new one – to grow (takes time to harden, soft shelled crabs)

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Evolution and classification

• 545 million yrs ago• Exoskeleton• True coelom• Jointed appendages• Evolved from common ancestor, convergent

evolution (Trilobites)• Tagma- fused into larger parts

Holt cd-

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5 subphyla

• based on appendages development• Mouth parts- mandibles (jaw like) and

chelicerae (pincher like)1. Trilobita2. Crustacea3. Chelicerata4. Myriapoda5. Hexopoda

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Objectives 36.2

• Describe the characteristics of crustaceans

• Compare aquatic crustaceans with terrestrial crustaceans

• Explain the function of the appendages on a crayfish

• Summarize digestion, respiration, circulation, excretion, and neural control in crayfish

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Subphylum Crustacea

The subphylum crustacea contains about 38000 known species. Crustaceans are abundant in oceans, lakes, and rivers, and a few species live on land. Some crustaceans are sessile, whiles others move by walking on legs, swimming with paddle-like appendages, or drifting with the currents.

Holt cd

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characteristics

• Diverse• 2 pair of antennae• Pair of jawlike chewing mouth parts- mandibles• Each body segment has pair of appendages• Some have 60 or more body segment• Most have 16-20 segments• Some breath by body, some have gills• Nauplius- free-swimming larva• Diverse in size, most small

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Types crustaceans

AquaticMarine environments (plankton, Copepods)• Fresh water- (water fleas, daphnia)• Barnacles- sessile as adults, free-

swimming as larva (cirri, feeding parts)Terrestrial isopods- (sow bugs, pill bugs)No waxy coat

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Crayfish-Order Decapods “ten feet”

• Have five pairs of legs – locomotion1. External structure-a. two major sections- 1. abdomen- 6 segments2. cephalothorax-head(5)thorax(8)Tagmata- segments fused together to make one

larger structureb. antennae- 2 pairs, feelers, tastec. chelipeds- back legs with pinchersd. swimmerets- create water currents and function

in reproductione. telson/uropods- posterior end is paddle like tail

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Crayfish-2. digestion- esophagus to stomach where teeth grind food

into paste and the digestive glands secret enzymes for digestion and absorption extra exits anus

3. respiration- feather like gills, as it walks legs circulate water across gills

4. circulation- open circulatory system5. Excretion- water is removed by excretory organs called

the green glandsdilute fluids are excreted by a pore at the base of the antennae

6. Neural control/ sensory organs- similar to annelidsHolt cdHave pair of ganglia, sense vibration and chemical in water

by sensory hairs, compound eye

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36.3 objectives

• List the characteristics of arachnids, as represented by spiders

• Explain the adaptations that spiders have for predatory life on land

• Identify the unique characteristics of scorpions, mites, and ticks

• Compare the characteristics of millipedes and centipedes

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Subphyla Chelicerata

• Nearly all members are terrestrial

- chelicerates, spider, scorpions, mites, sea spiders, and horseshoe crabs

• Lack antennae

• 6 pair of appendages

• Chelicerae- pinchers or fangs

• Major class is the arachnidae 70,000 species

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C. Arachnida

• Arachnids- spiders, scorpions, mites, and ticks

• Cephalothorax and abdomen• 6pairs of jointed appendages• One pair of chelicearae• One pair of pedipalps (hold food)• Four pair of walking legsHolt cd

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Anatomy of a spider• Range in length 0.5 mm to 9 cm • Narrow body• Fangs for venom• Poison glands• Simple eye/ single lens• Spinnerets- found at the tip of the

abdomen (3pairs), silk glands• Nervous, digestive, circulatory system

similar to most crustaceans

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Anatomy of a spider

• Book lungs- paired sacs in the abd w/ folds (look like a book)

• Tracheae- system of tubes carry air directly to the tissues from openings in the exoskeleton (spiracles)

• Some have both• Malpighian tubules- hollow projections of the

digestive tract that collect body fluids and wastes and carry them to the intestine

• Also help to conserve water (water gets reabsorbed)

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Life of spider

• Feed on insects• Some will catch fish, frogs and even birds• Some chase prey• Some hide and wait• Wait till get trapped in web• Immobilize prey by wrapping them in silk• Most not dangerous to human• 2 are: brown recluse, black widow

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scorpions

Differ from spiders in 2 ways1. Large pincer like pedipalps2. Segmented abdomen with large stinger on the

last segment

Hide during the day, hunt at nightInject venomOnly some fatal to humanTropical and semitropical regions, dry temperate or

desert regions

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Mites and ticks

• Most abundant specialized arachnids• 30000 species – of known species• Completely fused cephalothorax and abdomen• Small• Freshwater, marine, terrestrial • Chiggers- human host• Transfer disease- rocky mountain spotted fever

and lyme disease

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Sub phylum Myriapodamany feet

• Nearly all members are terrestrial

Class Diplopoda- millipeds

-2 pairs of legs on each body segment, except the last two

-Up too 100 body segments (200 legs)

-Short antennae

-Two groups of simple eyes (poor vision)

-Maxillas and mandibles to eat plants (good sense of smell)

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Sub phylum Myriapodamany feet

• Class chilopoda- centipedes• Few as 15 or 175 pairs of legs• 12 inches long• Poison claws• Long antennae• Two clusters of simple eyes• Eat earthworms, insects• Most not harmful to humans

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http://www.youtube.com/watch?v=-frk3pL620M&feature=related

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http://bioweb.uwlax.edu/zoolab/Table_of_Contents/Lab-7b/Crayfish_Sexes/crayfish_sexes.htm

                                                       

  

                              

       

 1. Gonopods

 2.  Opening of the vas deferens

 3.  Opening of the oviduct

 4.  Seminal receptacle

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Dissection of Crayfish

External

• http://www.youtube.com/watch?v=DRULKv9W6DM&feature=related

Internal

• http://www.youtube.com/watch?v=rpkiNLhCBMU

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Grasshopper Dissections

• http://www.ent.iastate.edu/ref/anatomy/ihop/

• http://wwwbio200.nsm.buffalo.edu/labs/tutor/Grasshopper/

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