Arthropods

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Arthropods

• Chapter 28

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Arthropods include

• Insects, Arachnids, Crustaceans, Centipedes

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Common characteristics of all arthropods

1. Invertebrates-no backbone
2. Bilateral symmetry- divide into 2 equal sides at
   one point
3. Coelom- cavity around internal organs
4. Exoskeleton-outside body skeleton
5. Jointed appendages- structures growing out of
   body have joints
6. Open circulatory system blood pools in spaces
   (not vessels)

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Common characteristics cont

• 7. Complete digestive system -mouth, intestines,
  stomach, anus
• 8. Mandibles-a variety of jaws/
• Functions hold, chew, suck, and bite

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Appendages

• Used for 1. locomotion, 2. sensing, 3. feeding,
  4. mating

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Exoskeleton

• Hard thick covering made of protein chitin
• May be solid all over body or may be in segments
• Functions
• 1. Protect
• 2. Support internal tissues
• 3. A place of attachment for muscles, prevents
• 4. Water loss

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Exoskeleton growth

• Cant grow as the body grows
• They must shed the old skeleton grow a new
  one/process called molting
• The new skeleton will grow underneath
  eventually pop off the old one
• Most arthropods molt 4-7 times in life

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Most arthropods have 3 segments to their body

• These include
• -The head
• -The thorax (chest area)
• -The abdomen

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How do arthropods breathe (respire)?

• 1. Aquatic arthropods-use gills ex. Crayfish

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Breathing cont

• 2. Most insects use tracheal tubes
• -branching networks of hollow air passages that
  carry air through body.
• -Muscles pump air through the tubes to openings
  called spiracles.
• Ex. grasshopper

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Breathing cont

• 3. Arachnids use book lungs
• -these air chambers are stacked like books
• Ex. Spider

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Arthropods have acute (very good) senses

• Quick movement Ex. Fly
• Antennae-use to detect and communicate
• Pheromones-chemicals used to signal Ex. Ants
• Acute vision (simple and compound eyes)
• -detect motion very well
• -can see in almost all directions except
  directly behind.
• Ex. This is why it is hard to
• hit a fly!

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Reproduction in Arthropods

• Most have 1 type of sex organ on each (male or
  female)
• A few are hermaphrodites (male female organs)
• Types of fertilization
• -If it lives on land-fertilization is internal
• -If it lives in water-fertilization is external
  in water

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Arthropod classification

• Kingdom Animalia
• Phylum Arthropoda
• Classes 4 classes

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4 classes of arthropods

• Arachnids-spiders, scorpions, mites, ticks
• Crustaceans-all are aquatic-lobster, shrimp,
  crayfish

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• 3. Centipedes millipedes- they differ on the
  number of legs on each section the type of food
  they eat

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Class Insecta

• Includes millions of species
• (largest group)
• Mate only around 1 time in lifetime
• Eggs are fertilized internally and shells form
  around the eggs
• Female lays the eggs after they are fertilized
• The of eggs laid is enormous
• Purpose to increase chance of survival

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Insect cartoon
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Changes insects undergo after hatching

• Metamorphosis-series of changes controlled by
  chemical substances

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2 Types of Metamorphosis

• Complete metamorphosis-has 4 stages
• (ex. Butterfly)
• 4 stages
• a. Egg
• b. larva-free living worm-like stage
  (caterpillar)
• c. pupa-larva tissue broken down and replaced in
  a case-cocoon
• d. adult

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Complete metamorphosis
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• 2. Incomplete metamorphosis -has 3 stages
• (Ex. Grasshopper)
• 3 stages
• a. egg
• b. nymph-smaller version of adult
• (looks like adult but lacks appendages like
  wings and cannot reproduce
• c. adult

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Know Insect Structures!

• P. 752 Draw and label the grasshopper
• Write the functions under each labeled part
• Leave in notebook to study for test
• Study drawing, functions and notes for test