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Arthropods. What are ARTHROPODS?. Coelomate Segmented Bilateral Symmetry Exoskeleton – made of protein and chitin Jointed appendages – any structure (leg or antennae) that grows out of the body. What are Arthropods ?. earliest invertebrates to exhibit jointed appendages

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what are arthropods
What are ARTHROPODS?
  • Coelomate
  • Segmented
  • Bilateral Symmetry
  • Exoskeleton – made of protein and chitin
  • Jointed appendages – any structure (leg or antennae) that grows out of the body
what are arthropods3
What are Arthropods?
  • earliest invertebrates to exhibit jointed appendages
    • Jointed appendages are an advantage because they allow more flexibility for animals with hard, rigid exoskeletons
    • Joints allow powerful movements and allow appendages to be used in many ways
what are arthropods4
What are Arthropods?

Appendages

Jointed Appendages

exoskeletons provide protection
Exoskeletons Provide Protection
  • made up of protein and CHITIN
  • can be a continuous

covering over most

of body OR

made of plates

that are held

together by hinges

Continuous

Hinged

exoskeleton advantages
Exoskeleton Advantages
  • Protects, supports internal tissues
  • Provides place for muscle attachment
  • Aquatic arthropods have exoskeleton reinforced with calcium carbonate
exoskeleton disadvantages
Exoskeleton Disadvantages
  • Heavy
    • the larger the animal, the thicker and heavier the exoskeleton
  • Exoskeletons don’t grow
    • animals must molt when they get too large for exoskeleton
molting
Molting
  • Animal contracts muscles and takes in air or water
  • Body swells and causes exoskeleton to split open, usually along the back
  • Most arthropods will molt 4-7 times before becoming an adult.
before the new exoskeleton hardens
Before the new exoskeleton hardens...
  • increased circulation to all parts of the body cause the animal to puff up and new exoskeleton hardens leaving some “growing room”
  • animal can’t protect itself, can’t move
question 1
Question 1

Which of the following organisms would be most likely to have an exoskeleton reinforced with calcium carbonate?

  • Spider
  • Beetle
  • Crab
  • Dragonfly

Correct!

question 2
Question 2
  • Exoskeletons are heavy. Why can aquatic arthropods grow so much larger than terrestrial arthropods?

The buoyancy of the water helps support the weight of the exoskeleton

question 3
Question 3
  • What is one advantage and one disadvantage of flying arthropods having a thinner, lighter weight exoskeleton?

Disadvantage: less protection

Advantage: greater freedom to fly and jump

question 4
Question 4
  • What is one advantage and one disadvantage of having a cephalothorax?

Disadvantage: less flexibility, mobility

Advantage: more protection

segmentation
Segmentation
  • 3 segments
    • abdomen
    • thorax
    • head
segmentation15
Segmentation
  • Sometimes these segments can be fused together
    • some have head and fused thorax and abdomen
    • some have abdomen

and fused head and

thorax (cephalothorax)

respiration
Respiration
  • Efficient respiratory systems to meet large O2 demands
  • Large O2 demand needed to sustain high metabolism for fast movements
  • 3 types of respiratory structures
    • gills (aquatic arthropods)
    • tracheal tubes (terrestrial arthropods)
    • book lungs (terrestrial arthropods)
respiration17
Respiration
  • Gills
    • water moves over gills
    • O2 from water diffuses

into gills and into

bloodstream

    • CO2 from body diffuses out through gills into surrounding water
respiration18
Respiration
  • Tracheal tubes
    • branching network of hollow air passages that take air throughout the body

Muscle movement brings air in/out through SPIRACLES (openings in abdomen and thorax)

respiration19
Respiration
  • Book lungs
    • spiders and relatives
    • air filled chambers with leaf-like plates
    • stacked plates

are arranged

like pages

of a book

antennae
Antennae
  • Acute sensing by antennae
    • stalk like structure that can detect changes in the environment
      • movement
      • sound
      • chemicals

Used for sound and odor communication

slide21
Eyes
  • Compound Eyes
    • visual structure with

many lenses

  • Simple Eyes
    • visual structure with one lens for detecting light

one pair of compound eyes and 3-8 simple eyes

nervous system
Nervous System
  • Double ventral nerve cord
  • Anterior brain
  • Several fused ganglia that control the body section they are located in
circulatory system
Circulatory System
  • Open circulatory system
    • blood flows away from the heart in vessels
    • blood flows out of vessels into tissues
    • blood returns to the heart through open spaces
digestive system
Digestive System
  • Complete digestive system with mouth, intestine, and anus
  • Mouth has 1 pair of jaws called MANDIBLES
    • adapted for holding, chewing, sucking, or biting
reproduction sexual and asexual
Reproduction – Sexual and Asexual
  • Sexual reproduction
    • separate sexes
    • internal fertilization for terrestrial species
    • external fertilization for aquatic species
reproduction sexual and asexual26
Reproduction – Sexual and Asexual
  • Asexual reproduction
    • PARTHENOGENISIS
      • a new individual develops from an unfertilized egg
      • seen with ants, aphids and bees
arachnids
Arachnids
  • spiders (largest group), ticks, mites, and scorpions
  • 2 body regions: cephalothorax and abdomen
  • 6 pairs of jointed appendages – 12 total appendages!
arachnids28
Arachnids
  • 1st pair - chelicerae, are near the mouth
  • modified into pincers (hold food) or fangs (inject poison)

chelicerae

arachnids29
Arachnids
  • 2nd pair – pedipalps, for handling food and sensing

pedipalps

arachnids30
Arachnids
  • Silk, for webs, is secreted by silk glands in the abdomen
  • as it is secreted, it is spun into thread by SPINNERETTES
  • spiders are predatory and feed almost exclusively on other animals
arachnids31
Arachnids
  • Ticks and mites have only 1 body section
  • Head, thorax and abdomen are completely fused
  • Ticks feed on blood of other animals
arachnids32
Arachnids
  • Mites feed on fungi, plants, and animals
  • small – not usually visible
  • can transmit diseases

Dust mites

arachnids33
Arachnids
  • Scorpions have many abdominal body segments
  • Enlarged pincers
  • Long tail with

venomous stinger

at the tip

crustaceans
Crustaceans
  • crabs, lobster, shrimp, crayfish, barnacles
  • Only arthropods with 2 pairs of antennae
  • mandibles – move

from side to side

  • 2 compound

eyes

crustaceans35
Crustaceans
  • 5 pairs of walking legs
  • 1st pair are claws for defense

claw

legs

crustaceans36
Crustaceans
  • Most are aquatic and use gills
  • pill bugs (roly-polies) live on land, but must have moisture to aid in gas exchange

Yes! This is a crustacean!

centipedes and millipedes
Centipedes and Millipedes
  • Centipedes are carnivorous – eat soil arthropods, snails, slugs,

and worms

  • Bites can be painful
  • Millipedes – eats plants and dead material on damp forest floors
  • Does not bite, but does

spray foul-smelling fluid

horseshoe crabs
Horseshoe Crabs
  • Class Merostomata
  • “Living Fossils”- unchanged for 220 million years (Triassic period)
  • Extensive exoskeleton
  • Live in deep coastal waters
  • forage bottoms for algae,

annelids and molluscs

insecta
Insecta
  • Flies, grasshoppers, lice, butterflies, beetles
  • 3 body segments
  • 6 legs
  • Very diverse - more insects than all other classes of animals combined
insecta40
Insecta
  • mate once in lifetime
  • internal fertilization
  • some exhibit

parthenogenesis

  • large number of eggs

to increase survival rate

insecta41
Insecta
  • insect embryos develop inside eggs, eggs hatch
  • some look like miniature adults
    • will molt several times until adult size

Molt

Nymph

Eggs

Nymph

Molt

Adult

insecta42
Insecta
  • INCOMPLETE METAMORPHOSIS
    • 3 stages: egg, nymph, adult
  • Nymphs can’t reproduce
  • Nymph gradually becomes an adult
insecta43
Insecta
  • Some undergo COMPLETE METAMORPHOSIS
    • 4 stages: egg, larva, pupa, adult
  • Metamorphosis is controlled by chemical substances in the insect

Egg

Adult

Larva

Pupa

insecta44
Insecta
  • Incomplete metamorphosis: grasshoppers and cockroaches
  • Complete metamorphosis: ants, beetles, flies, wasps
origins of arthropods
Origins of Arthropods
  • Successful because of
    • varied life styles
    • high reproductive output
    • structural adaptations
    • hard exoskeletons
    • jointed appendages
origins of arthropods46
Origins of Arthropods
  • Hard exoskeletons fossilize – a lot is known about evolutionary history
  • Evolved from ANNELIDS (segmented worms)
  • Arthropods have more complex segments, more developed nervous systems
  • circular muscles in annelids do not exist in arthropods
question 5
Question 5

Spiders are:

  • predators
  • scavengers
  • decomposers
  • parasites

Predators!

question 6
Question 6

Having 2 pairs of antennae distinguish _________ from other arthropods.

  • centipedes
  • millipedes
  • crustaceans
  • horseshoe crabs

Crustaceans!

question 7
Question 7
  • Why are horseshoe crabs called “living fossils?”

They remain unchanged after 220 million years!