Biology Chapter 28 Arthropods

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Biology - Chapter 28Arthropods

• Charles Page High School
• Stephen L. Cotton

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Section 28-1Introduction to Arthropods

• OBJECTIVES
• Describe the four subphyla of arthropods.

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Section 28-1Introduction to Arthropods

• OBJECTIVES
• Explain how arthropods perform their essential
  life functions.

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Section 28-1Introduction to Arthropods

• OBJECTIVES
• Discuss metamorphosis in arthropods.

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Section 28-1Introduction to Arthropods

• Phylum Arthropoda - vary enormously in size,
  shape, and habits
  
• More than a million arthropod species have been
  described, and scientists are certain many more
  have not yet been found (such as in the tropics)

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Section 28-1Introduction to Arthropods

• Phylum Arthropoda is subdivided into four
  subphyla
  
• 1. Subphylum Trilobita
• trilobites are thought to be the oldest
  subphylum
  
• these were dwellers in ancient seas they are now
  all extinct

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Section 28-1Introduction to Arthropods

• Phylum Arthropods is subdivided into four
  subphyla
  
• 2. Subphylum Chelicerata
• chelicerates include spiders, ticks, mites,
  scorpions, and horseshoe crabs

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Section 28-1Introduction to Arthropods

• Phylum Arthropods is subdivided into four
  subphyla
  
• 3. Subphylum Crustacea
• crustaceans include such familiar (and edible)
  organisms as crabs, shrimp, crayfish

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Section 28-1Introduction to Arthropods

• Phylum Arthropods is subdivided into four
  subphyla
  
• 4. Subphylum Uniramia
• includes most arthropods centipedes, millipedes,
  and all insects (bees, moths, flies,
  grasshoppers, beetles)

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Section 28-1Introduction to Arthropods

• Why are there so many?
• Been evolving on Earth for a long time the first
  appeared in the sea more than 600 million years
  ago
  
• colonized all parts of the sea and most
  freshwater habitats, as well as the land

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Section 28-1Introduction to Arthropods

• The ancestors of the arthropods were soft-bodied
  animals that left few fossils
  
• early forms are thought to be similar to that of
  the trilobites
  
• a thick, tough outer covering, and composed of
  many segments with appendages

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Section 28-1Introduction to Arthropods

• The appendages were branched into one walking leg
  and one gill
  
• Figure 28-3, page 608
• Most today exhibit two trends away from
  trilobites
  
• 1. Fewer body segments
• 2. Appendages more specialized

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Section 28-1Introduction to Arthropods

• Although there are many different types of
  arthropods, they all have three important
  arthropod features
  
• 1. Tough exoskeleton
• 2. Series of jointed appendages
• 3. Segmented body

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Section 28-1Introduction to Arthropods

• Also have
• brain, located in dorsal part of head
• ventral nerve cord
• open circulatory system, powered by a single heart

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Section 28-1Introduction to Arthropods

• The exoskeleton is made of chitin (a protein)
• some are leathery and flexible
• others are extremely hard
• exoskeleton provides protection from physical
  damage and also support many are waterproof

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Section 28-1Introduction to Arthropods

• Although the exoskeleton acts like a suit of
  armor, it has some disadvantages
  
• cannot grow as the animal grows
• movement only at the joints
• very heavy if the animal was to grow large

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Section 28-1Introduction to Arthropods

• All arthropods have jointed appendages (arthro-
  means joint -pod means foot) that enable them to
  move
  
• remaining appendages evolved into adaptations for
  different environments antennae claws walking
  legs wings flippers
  

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Section 28-1Introduction to Arthropods

• All arthropods have segmented bodies
• some have worm-like bodies, such as centipedes
  and millipedes
  
• others have lost some of the body segments, or
  have fused them together, such as insects

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Section 28-1Introduction to Arthropods

• 1. Feeding- almost any type of food we can
  imagine
  
• herbivores carnivores parasites filter
  feeders detritus feeders (Figure 28-6, p.610)
  
• some herbivores are selective, and others will
  eat just about anything green

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Section 28-1Introduction to Arthropods

• 2. Respiration- 3 basic types of respiratory
  structures
  
• a) gills b) book gills and book lungs and c)
  tracheal tubes
  
• many aquatic varieties, such as crabs and shrimp,
  have gills that look like a row of feathers under
  cover of their exoskeleton

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Section 28-1Introduction to Arthropods

• The gills are formed from the same structures as
  the mouthparts and legs
  
• movement of the mouthparts and legs keeps a
  steady stream of water moving over the gills

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Section 28-1Introduction to Arthropods

• Book gills (found in the horseshoe crabs) and
  book lungs (found in spiders and relatives) are
  unique to these arthropods
  
• several sheets of tissue are layered like pages
  of a book this increases the surface area for
  gas exchange

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Section 28-1Introduction to Arthropods

• An opening called the spiracle connects the sac
  containing the book lungs with the fresh air
  outside
  
• Most terrestrial arthropods (insects for example)
  have another unique structure- long branching
  tracheal tubes

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Section 28-1Introduction to Arthropods

• From spiracles, long branching tracheal tubes
  reach deep into the animals tissues
  
• supplies oxygen by diffusion
• as they move, body muscles cause the tracheae to
  shrink and expand thus filling with air works
  well in small animals

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Section 28-1Introduction to Arthropods

• 3. Internal transport- a well developed heart
  pumps blood through an open circulatory system
  
• blood leaves the vessels, and moves through
  spaces in the tissue called sinuses

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Section 28-1Introduction to Arthropods

• 4. Excretion- solid waste leaves through the
  anus
  
• nitrogen-containing wastes from cellular
  metabolism are removed in a variety of ways
  
• a) insects and spiders have Malpighian tubules
  that filter the blood

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Section 28-1Introduction to Arthropods

• b) aquatic arthropods have wastes diffuse into
  the surrounding water at unarmored places, such
  as gills
  
• c) some, such as lobster, have a green gland
  located near the base of the antennae emptied
  through openings on head

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Section 28-1Introduction to Arthropods

• 5. Response- many have well developed nervous
  systems
  
• all have a brain, consisting of a pair of ganglia
  in the head this is the central switchboard for
  incoming information and outgoing instructions

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Section 28-1Introduction to Arthropods

• Nerve cord runs on ventral side of the body
  along this nerve cord are additional ganglia that
  serve as local command centers
  
• these coordinate legs and wings this is why they
  might still move even though the head has been
  cut off!

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Section 28-1Introduction to Arthropods

• Simple sense organs such as statocysts and
  chemical receptors
  
• also have compound eyes more than 2000 separate
  lenses can detect color and movement very well
  
• may see ultraviolet light

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Section 28-1Introduction to Arthropods

• May have well-developed sense of taste, although
  the receptors are located in strange places
  
• not only on the mouthparts, but also on antennae
  and legs

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Section 28-1Introduction to Arthropods

• Many insects have well-developed ears that hear
  sounds above the human range, but the ears are in
  odd places
  
• eardrums in grasshoppers, for example, are behind
  their legs
  
• spiders are sensitive to vibrations in their webs

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Section 28-1Introduction to Arthropods

• The arthropods well-developed sense organs allow
  it to detect and escape predators
  
• this is in combination with their protective
  exoskeleton
  
• but, there are also additional methods of
  protection

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Section 28-1Introduction to Arthropods

• Venomous stings- bees, ants
• powerful claws- lobsters, crabs
• nasty chemicals- millipedes
• creating a diversion- drop claw
• visual trickery- matching color and texture of
  surroundings
  
• imitate other dangerous species- called mimicry
  (p.614)

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Section 28-1Introduction to Arthropods

• 6. Movement- well-developed muscle systems
  coordinated by nervous system (Figure 28-13,
  p.614)
  
• the pull of muscles on the exoskeleton allows
  them to beat wings to fly push legs to walk or
  jump or beat flippers against water to swim

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Section 28-1Introduction to Arthropods

• 7. Reproduction- usually very simple
• male produces sperm female produces egg
• fertilization usually takes place inside the body
  of the female
  
• Stop Day 1

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Section 28-1Introduction to Arthropods

• Growth and Development- the exoskeleton (as
  useful as they are), present a problem in growth
  
• it does not grow as the animal does thus must be
  replaced
  
• arthropods will molt, or shed their exoskeleton
  controlled by several hormones

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Section 28-1Introduction to Arthropods

• Steps in molting
• 1. Produce molting hormone
• 2. Digest inner parts of exoskeleton to recycle
  chemicals
  
• 3. Form new exoskeleton shed old exoskeleton
• 4. Harden new exoskeleton

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Section 28-1Introduction to Arthropods

• The animal must wait for the new exoskeleton to
  harden may only be a few hours or a few days
  
• quite vulnerable during this time thus they
  might need to hide from predators

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Section 28-1Introduction to Arthropods

• This molting may take place several times
• in most cases, it will involve metamorphosis- a
  change in form
  
• there are two forms of metamorphosis

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Section 28-1Introduction to Arthropods

• Metamorphosis
• 1. Incomplete metamorphosis hatches eggs into
  young animals that look like small adults lack
  functioning sexual organs and wings
  
• Figure 28-15, page 615 for the grasshopper on the
  left

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Section 28-1Introduction to Arthropods

• Metamorphosis
• 2. Complete metamorphosis involves four stages
• a) the egg
• b) larvae (a wormlike stage that does not look
  like the adults)
  
• c) pupa (an inactive stage that totally
  rearranges the body)
  
• d) the adult

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Section 28-1Introduction to Arthropods

• Hormone interaction
• high levels of juvenile hormone keep an insect in
  the larval form when it drops below a certain
  point- it becomes pupa
  
• molting hormone controls the molting process

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Section 28-1Introduction to Arthropods

• Because of the balance of juvenile hormone,
  molting hormone, and others- it is possible to
  combat insects by tampering with their hormone
  levels
• can prevent molting thus no adults, and no
  reproduction!

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Section 28-2Spiders and their Relatives

• OBJECTIVES
• Discuss the distinguishing characteristics of
  chelicerates.

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Section 28-2Spiders and their Relatives

• OBJECTIVES
• Describe and give examples of members of the two
  main groups of animals in the subphylum
  Chelicerata.

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Section 28-2Spiders and their Relatives

• OBJECTIVES
• Explain how arachnids obtain food.

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Section 28-2Spiders and their Relatives

• Subphylum Chelicerata- called chelicerates,
  includes spiders and their relatives- horseshoe
  crabs, ticks, and scorpions
  
• characterized by a two-part body and mouthparts
  called chelicerae
  

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Section 28-2Spiders and their Relatives

• also lack sensory feelers found on the heads of
  most other arthropods
  
• the two-part body is
• 1. Cephalothorax
• 2. Abdomen

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Section 28-2Spiders and their Relatives

• Cephalothorax- contains the brain, eyes, mouth
  and mouthparts, and esophagus
  
• posterior end is the first part of the digestive
  system, and several pairs of walking legs
  
• Abdomen- contains most of the internal organs
  (Fig. 28-17, p.617)

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Section 28-2Spiders and their Relatives

• All chelicerates have two pairs of appendages
  attached near the mouth that are adapted as
  mouthparts
  
• first pair are chelicerae
• second pair is longer, and called pedipalps
• both serve different feeding job

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Section 28-2Spiders and their Relatives

• Among the oldest chelicerates are the horseshoe
  crabs
  
• somewhat misleading name, because they are not
  true crabs
  
• have not changed much in the last 430 million
  years
  
• heavily armor plated (p.618)

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Section 28-2Spiders and their Relatives

• Have 5 pairs of walking legs
• long spike-like tails
• can grow up to 60 cm long, about the size and
  shape of a frying pan
  
• newly hatched are called trilobite larvae because
  they look so much like them

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Section 28-2Spiders and their Relatives

• Class Arachnida- includes spiders, ticks,
  scorpions, and mites
  
• have 4 pairs of walking legs
• pedipalps capture and hold prey chelicerae
  adapted for biting and sucking out soft parts

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Section 28-2Spiders and their Relatives

• Spiders- predators that usually feed on insects
• capture prey in a variety of ways
• ensnare in a web
• stalk, and then pounce
• ambush under camouflage, then leap out and grab

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Section 28-2Spiders and their Relatives

• Once captured
• 1. Hollow fanglike chelicerae inject paralyzing
  venom
  
• 2. Mouth introduces enzymes
• 3. Enzymes break down tissue
• 4. Spider sucks up the liquefied tissues with
  esophagus and specialized pumping stomach

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Section 28-2Spiders and their Relatives

• Whether or not they spin webs, all spiders
  produce a strong, flexible protein called silk
  
• produced in special glands in the abdomen
• is 5 times stronger than steel
• makes webs, cocoons for eggs, or wrappings for
  prey

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Section 28-2Spiders and their Relatives

• Forces the liquid silk through organs called
  spinnerets
  
• it then hardens into a single strand
• do not have to learn how to spin the intricate
  webs it is programmed into their brain as soon
  as they hatch

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Section 28-2Spiders and their Relatives

• Mites and Ticks- small arachnids, many of which
  are parasites
  
• the chelicerae are needlelike structures that are
  used to pierce the skin of their hosts
  
• the chelicerae also have large teeth to help the
  parasite hold on to the host

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Section 28-2Spiders and their Relatives

• Some, such as spider mites,are major agricultural
  pests
  
• others, such as chiggers, mange and scabies
  mites,cause painful itching rashes in humans
  
• tick bites are not just annoying they may also
  spread Rocky Mountain spotted fever and Lyme
  disease

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Section 28-2Spiders and their Relatives

• Scorpions- carnivores that prey on other
  invertebrates, usually insects
  
• pedipalps are enormously enlarged into a pair of
  claws
  
• abdomen is long and segmented ends in a venomous
  barb to sting prey

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Section 28-2Spiders and their Relatives

• Scorpion grabs the prey with its pedipalps then
  whips the abdomen over its head to sting the
  prey- thus killing or paralyzing it
  
• they like to crawl in moist, dark places- good
  idea to check your shoes when putting them on!

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Section 28-3Crustaceans

• OBJECTIVES
• Discuss the distinguishing characteristics of
  crustaceans.

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Section 28-3Crustaceans

• OBJECTIVES
• Describe the anatomy of a typical crustacean.

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Section 28-3Crustaceans

• Subphylum Crustacea- over 35,000 species, mainly
  aquatic
  
• tiny as a water flea (0.25 mm) to Japanese spider
  crabs (6 meter)
  
• characterized by a hard exoskeleton 2 pairs of
  antennae mouthparts called mandibles

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Section 28-3Crustaceans

• Main body parts are the head, thorax, and
  abdomen
  
• in many, the head and thorax have fused
  cephalothorax, covered by a tough shell called
  the carapace
  
• many (crabs, lobsters) have calcium carbonate
  that makes their exoskeleton very hard

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Section 28-3Crustaceans

• In crustaceans, the first two pairs of appendages
  are feelers called antennae, which bear many
  sensory hairs
  
• third pair of appendages are mouthparts called
  mandibles
  
• might bite and grind filter feeding pick up
  detritus

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Section 28-3Crustaceans

• Appendages can vary greatly
• barnacles have delicate, feathery appendages for
  filter feeding
  
• others have legs for walking or swimming
• some modified for fertilization, carrying eggs,
  spearing prey

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Section 28-3Crustaceans

• Appendages are adapted for
• the large claws catch prey pick up, crush, and
  cut food- these are on the thorax
  
• 4 pairs of walking legs, also on the thorax
• Flipper-like swimmerets for swimming on the
  abdomen

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Section 28-3Crustaceans

• The paddle-like appendages and the final
  abdominal segment form a large, flat tail
  
• very powerful a crayfish can snap forward, thus
  rapidly pulling the animal backwards
  
• roly-poly in Figure 28-22, page 620- pill bug
  (a crustacean)

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Section 28-4Insects and their Relatives

• OBJECTIVES
• Describe and give examples of three classes in
  the subphylum Uniramia.

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Section 28-4Insects and their Relatives

• OBJECTIVES
• Discuss the anatomy of a typical insect.

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Section 28-4Insects and their Relatives

• OBJECTIVES
• Explain how insects communicate.

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Section 28-4Insects and their Relatives

• Subphylum Uniramia- more species than all other
  groups of animals alive today!
  
• includes insects, centipedes, and millipedes
• characterized by one pair of antennae appendages
  that do not branch (Uni- means one ramus means
  branch)

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Section 28-4Insects and their Relatives

• These arthropods, which display a multitude of
  forms and habits, are thought to have evolved on
  land about 400 million years ago, during the
  Devonian Period
• long before dinosaurs!
• they inhabit almost every terrestrial habitat on
  Earth

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Section 28-4Insects and their Relatives

• Centipedes and Millipedes- these are the
  many-legged animals
  
• characterized by a long, wormlike body composed
  of many leg-bearing segments
  
• Figure 28-25, page 622

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Section 28-4Insects and their Relatives

• They lack closable spiracles and a waterproof
  coating on their exoskeleton
  
• thus they lose water easily
• therefore, they tend to live beneath rocks, in
  soil, or in other relatively moist areas

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Section 28-4Insects and their Relatives

• Class Chilopoda- centipedes
• these are carnivores that have in addition to
  their mouthparts, a pair of poison claws in their
  head region
  
• used to catch and stun or kill prey- other
  arthropods, earthworms, toads, small snakes, and
  even mice

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Section 28-4Insects and their Relatives

• Most centipedes in North America are 3-6 cm long
  but some tropical species are brightly colored,
  and up to 26 cm
  
• Despite the name (which means 100 legs), they can
  have a variable number, depending upon how long
  they are

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Section 28-4Insects and their Relatives

• There is only one pair of legs per body segment
• except the mouth, which has the poison claws, and
  the last three segments (which are legless)

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Section 28-4Insects and their Relatives

• Class Diplopoda- these are the millipedes, and
  they do not have a thousand legs like the name
  implies
  
• they have 2 pairs of legs per body segment
• these are timid creatures, and are detritus
  feeders

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Section 28-4Insects and their Relatives

• Class Insecta- the insects have more than 900,000
  species new ones are being discovered in the
  tropics all the time
  
• 3 out of every 4 animals!
• three part body head, thorax, and abdomen.
  There are 3 pairs of legs on the thorax

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Section 28-4Insects and their Relatives

• A typical insect has one pair of antennae, one
  pair of compound eyes on the head, two pairs of
  wings on the thorax, and uses a system of
  tracheal tubes for respiration
• Figure 28-26, page 623

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Section 28-4Insects and their Relatives

• Insects get their name from the Latin word
  insectum, meaning notched- refers to the division
  of their body into the three parts
  
• many insects, such as ants, have clear cut
  divisions- others such as grasshopper may not
  have body parts sharply defined

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Section 28-4Insects and their Relatives

• Feeding- insects have 3 pairs of appendages that
  are used as mouthparts, including a pair of
  mandibles (jaws)
  
• many shapes and varieties
• grasshopper cut / chew plants
• mosquito tube pierces skin to suck blood
  (females only)

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Section 28-4Insects and their Relatives

• butterfly long tube for sipping nectar
• bee chewing and gathering nectar
• fly spongy mouthpart used to soak up food

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Section 28-4Insects and their Relatives

• The saliva of female mosquitoes, which is
  injected when the mosquito bites, contains
  chemicals that prevent blood from clotting- also
  has chemicals that cause the itching
• bee body covered with many hairs that collect
  pollen

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Section 28-4Insects and their Relatives

• Chemicals in bee saliva help change nectar into a
  more digestible form- honey
  
• glands on the bee abdomen secrete wax, which is
  used to build storage chambers for food and
  others structures within a beehive

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Section 28-4Insects and their Relatives

• Movement- insects have 3 pairs of walking legs
• often equipped with spines or hooks for holding
  on, or used for defense
  
• may be used for jumping (fleas), or holding prey
  (praying mantis)

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Section 28-4Insects and their Relatives

• Movement- along with birds and bats, insects are
  the only living organisms capable of unassisted
  flight
  
• flight ability varies greatly from slow
  butterflies to fast flies, bees, and dragonflies
  
• requires enormous energy, thus have oversized
  mitochondria

91
Section 28-4Insects and their Relatives

• Insect societies- many animals form colonies,
  collections of individuals of the same species
  
• several types of insects for a special colony
  called a society
  
• separate individuals are dependent upon one
  another for survival

92
Section 28-4Insects and their Relatives

• Insect societies- examples are termites, wasps,
  bees, and ants
  
• all called social insects
• they have a division of labor
• 1) reproductive females
• 2) reproductive males
• 3) workers

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Section 28-4Insects and their Relatives

• Reproductive females queen, typically there is
  only one, and usually the largest individual in
  the colony- page 625
  
• termite queen may be 14 cm long, 10 times normal
• can produce more than 30,000 eggs a day!

94
Section 28-4Insects and their Relatives

• The reproductive males function only to fertilize
  the queens eggs
  
• queen bee mates only once
• the successful males die after mating, and the
  unsuccessful males are ejected from the colony
  and soon perish (since they are no longer needed!)

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Section 28-4Insects and their Relatives

• The workers perform all colony tasks except
  reproduction
  
• care for queen and eggs gather and store food
  build and maintain the colonys home
  
• in bees, the workers are sterile females in
  termites, the workers consist of males and females

96
Section 28-4Insects and their Relatives

• Insect communication- may use sounds, visual,
  chemical, or other methods
  
• may be necessary to find mate
• male crickets chirp by rubbing their forewings
  together
  
• male cicadas buzz special membranes on their
  abdomen

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Section 28-4Insects and their Relatives

• Male fireflies turn a light producing organ in
  their abdomen on and off
  
• many insects can release chemicals that attract
  the opposite sex- called pheromones
  
• communication in non-social insects not near as
  complex

98
Section 28-4Insects and their Relatives

• Queen bee produces a pheromone, called queen
  substance, that prevents the development of rival
  queens
  
• this substance makes the worker bees unable to
  lay eggs
  
• need a new queen? Feed the larvae a special diet

99
Section 28-4Insects and their Relatives

• Honeybees communicate with sound and movement, as
  well as with pheromones
  
• worker bees are able to convey information about
  the type, quality, direction, and distance of
  food by dancing
  
• Austrian biologist Karl von Frisch

100
Section 28-4Insects and their Relatives

• 1. Round dance- bee that has found food will
  circle first one way, then the other, over and
  over again (Fig. 28-32, p.627)
  
• tells others that food is within 50 meters, but
  not direction
  
• frequency of dance conveys quality of the food

101
Section 28-4Insects and their Relatives

• 2. Waggle dance- the bee that has found food runs
  forward in a straight line while wiggling her
  abdomen, then circles around much like a figure
  eight
• food is more then 50 m away
• the direction of the dance tells the direction of
  the food source

102
Section 28-5 How Arthropods Fit Into the World

• OBJECTIVES
• Describe how arthropods interact with other
  organisms in nature.

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Section 28-5 How Arthropods Fit Into the World

• OBJECTIVES
• Discuss how arthropods affect humans.

104
Section 28-5 How Arthropods Fit Into the World

• Such a large diverse group will play many roles
  in the natural world
  
• can be a direct source of food for many
  organisms
  
• either eating others or being eaten by them

105
Section 28-5 How Arthropods Fit Into the World

• Involved in symbiotic relationships Fig. 28-34,
  p.629
  
• pores of our skin are home to thousands of
  harmless microscopic mites no matter how much we
  clean our home, even our beds, there are millions
  of these dust mites

106
Section 28-5 How Arthropods Fit Into the World

• Agriculture would be impossible if not for bees,
  butterflies, wasps, moths, and flies that
  pollinate
  
• honey from bees silk from silkworm moths
• shrimp, crab, crayfish, lobster used as a food
  source for humans

107
Section 28-5 How Arthropods Fit Into the World

• Grasshoppers and termites can also be eaten they
  can also do considerable damage to crops and wood
  materials
  
• many insects and spiders are predators on other
  harmful species

108
Section 28-5 How Arthropods Fit Into the World

• Chemicals from arthropods
• extract of horseshoe crab blood is used to test
  purity of medications
  
• chitin from exoskeletons used to dress wounds and
  make thread for surgical stitches

109
Section 28-5 How Arthropods Fit Into the World

• The chitin may also be sprayed on fruit and
  frozen food to prevent spoilage
  
• the adhesive that barnacles use to attach
  themselves to rocks under water could be used in
  dentistry or underwater construction

110
Section 28-5 How Arthropods Fit Into the World

• Spider venom is being tested as a pesticide
• spider silk that could be used in making
  aircraft, helmets, bulletproof vests, and
  surgical thread

111
Section 28-5 How Arthropods Fit Into the World

• However good they are, they can also do
  considerable damage
  
• parasites damage livestock and crops
• mosquitoes annoying bites and the spread of
  malaria and yellow fever

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Section 28-5 How Arthropods Fit Into the World

• Biting flies carry diseases such as sleeping
  sickness and river blindness
  
• fleas carrying bubonic plague
• termites damaging wood
• locusts (grasshoppers) destroying crops