Arthropods

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Arthropods
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Arthropods

• Arthropods are the most diverse and numerous
  animals on earth
• More than 1 million different species have been
  identified
• They thrive in almost every habitat
• There worldwide population is estimated at a
  billion billion, or 1018 individuals

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General Characteristics of the Phylum Arthropoda
(Arthropods)

• Arthropods are characterized by there segmented
  bodies, jointed appendages and hard exoskeletons
• The exoskeleton is composed of chitin
• In most arthropods the segments are called the
  head, thorax and abdomen
• The head contains the antennae and mouth pieces,
  the thorax supports the legs and wings and the
  reproductive organs are found in the abdomen

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General Characteristics of the Phylum Arthropoda
(Arthropods)

• As arthropods grow, they will outgrown the
  chitinous exoskeleton. They will shed the
  exoskeleton in a process called molting

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General Characteristics of the Phylum Arthropoda
(Arthropods)

• All arthropods have an open circulatory system in
  which blood is pumped from a tube-like heart to
  bath the internal organs
• All arthropods have a ventral nerve cord and
  brain
• Along the nerve cord are specialized nerve cells
  called ganglia
• Most arthropods have compound eyes

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General Characteristics of the Phylum Arthropoda
(Arthropods)

• Aquatic arthropods have gills used for
  respiration
• Terrestrial arthropods have tracheae, which are
  chitin lined tubes that lead from the internal
  organs to the outside of the body where they end
  in little holes called spiracles that are used
  for breathing

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Overview of Arthropod Diversity

• Arthropods first evolved in the sea about 560
  million years ago
• A good example of an early extinct arthropod is
  called a trilobite

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Overview of Arthropod Diversity

• One ancient living arthropod is the horseshoe
  crab, which have been living virtually unchanged
  for over 300 million years

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Overview of Arthropod Diversity

• Modern arthropods include the crustaceans,
  arachnids, insects and myriapods

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Crustaceans

• The crustaceans include the lobsters, crabs,
  shrimp and barnacles
• Crustaceans have specialized appendages (claws or
  chelipeds) often used for fighting

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Terrestrial Arthropods

• The three groups of terrestrial arthropods
  include the arachnids, insects and myriapods
• The arachnids include the spiders, ticks,
  scorpions and mites
• The insects include beetles, ants, grasshoppers,
  butterflies and dragonflies
• The myriapods include centipedes and millipedes

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Metamorphosis

• Insects undergo metamorphosis a process by which
  the body changes from a sexually immature phase
  to the mature adult phase
• Once metamorphosis is complete the adult no
  longer grows
• Both molting and metamorphosis are controlled by
  hormones

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Metamorphosis

• Incomplete metamorphosis (grasshoppers) the
  immature young look like the adults but lack
  wings and sexual organs
• Complete metamorphosis (butterflies) the larval
  stage looks and functions much differently from
  the adult stage