Transcript Diversity of Arthropods

Diversity of
Arthropods
4 Subphyla
 Trilobita- Extinct Trilobites
 Chelicerata- Spiders, Scorpions, and
Ticks
 Crustacea- Shrimp, lobster, crayfish, and
barnacles
 Uniramia- Insects, Centipedes, and
Millipedes
Subphyla Trilobita
 EXTINCT
 Marine
 Head and
Segmented trunk
with one pair of legs
per segment
 Single pair Antennae
 Gills
Subphyla Chelicerata
 2 classes
 Xiphosura- Horseshoe Crab
 Arachnida- Spiders, Scorpions, Ticks and
Mites
Chelicarata
Characteristics
 Two Segments
 Cephalothorax
 Abdomen
 No Antenna
 Simple Eyes called Ocelli
 Six pairs of Jointed Appendages
 Chelicerae- Claws or Fangs (1 pair)
 Pedipalps- Feeding, Walking, Sensing (1pair)
 Walking Legs- Movement (4 pair)
Chelicerata Cont…
 Phylum Arthropoda
 Subphyla Chelicerata
 Class Xiphosura
 Class Arachnida
 Order Aranaea
 Order Scorpionida
 Order Acari
Horseshoe Crabs
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Class Xiphosura
NOT TRUE CRABS
Marine
Book Gills for breathing
Class Arachnida
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Terrestrial
8 Legs
Chelicerae or Fangs with Venom
Ocelli
No Antenna
Breathe through Book Lungs
 (Some species may have tracheal tubes)
Spiders
Order Aranaea
 8 simple eyes (ocelli)- Detect light, do not form
images
 6 pairs of appendages
 1st pair: Chelicerae, modified pincers to hold/handle
food or fangs to inject venom
 2nd pair: Pedipalps- handle/sense food, some males
use to deliver sperm during reproduction
 3rd-6th pair: legs used for locomotion, located on
cephalothorax
Spiders Cont…
 Fangs pierce prey, inject poison, & suck out
body fluids (feed primarily on insects, a few
species feed on small vertebrates)
 Have silk glands to make silk & spinnerets to
release silk for webs
 Lay eggs in silken sacs, young resemble adults
and are often cannibalistic
 Most spiders are solitary except at mating
Ticks and Mites
Order Acari
 Most abundant Arachnid
 Only 1 body section-Head, thorax, and
abdomen are completely fused
 Ticks are external parasites
 Can be found on reptiles, birds and mammals
 Mites are small and often invisible to naked
eye
 Parasitic while some adults can be free-living
Scorpions
Order Scorpionida
 Multiple body segments
 Cephalothorax and long segmented abdomen
 Pedipalps modified into Enlarged Pincers
 Up-Curved tail ends with a poisonous stinger
 Common in southern and southwestern United
States
 Nocturnal, feed mostly on insects and spiders
 Breathe through Book Lungs
 Give birth to live young
Subphyla Uniramia
 3 Classes
 Chilopoda- centipedes
 Diplopoda- millipedes
 Insecta- insects
Centipedes
Class Chilopoda
 Are carnivores, also eat soil arthropods,
snails, worms, and slugs
 They bite
 Have 1 pair of legs per segment; have 15
to 181 segments (always odd numbers);
1st segment has a pair of poison claws
  Have tracheal tubes w/ 1 pair of
spiracles on each segment
  Most lay eggs
Millipedes
Class Diplopoda
  Eat plants and dead materials
  Have 2 legs per segment; can have 100+
segments;
  Have tracheal tubes; each segment has 2
spiracles
  do not bite
  spray obnoxious smelling fluid as defense
mechanism
  lay eggs in a nest and guard them
Insects
Class Insecta
 Entomology – study of insects
 Largest group of arthropods
 Generally have 3 pair legs, usually 2 pair of
wings, 1 pair antennae and 3 body regions
 Mate once or only a few times
 Internal fertilization, shell forms around them,
then female lays eggs (large number increases
chance of survival)
Metamorphosis
 Most go through a metamorphosis – series of changes,
controlled by hormones.
 Usual 4 stages of development
1.egg
2.larva - free-living, wormlike stage
3.pupa – period of reorganization; larva organs and
tissues breakdown and are replaced w/adult tissues
4.adult
 Complete metamorphosis is an advantage because
young do not
compete w/adults for food.
Example – caterpillar to butterfly
Caterpillar > Butterfly
 In pupal stage, larval tissues break down & cells
called imaginal disk develops into tissues of the
adult
 Cocoon or chrysalis is a protective case formed
around the pupa
 Metamorphosis controlled by hormones
 Different stages have different functions
(caterpillar/growth & adult/reproduction)
Insects Cont…
 Many other insects go through 3 stages – gradual or
incomplete metamorphosis
 1. egg
2.nymph – looks like adult but smaller, lacks certain
appendages and cannot reproduce.
3.adult
Example – grasshoppers or cockroaches
 Respiratory system is a tracheal system with spiracles
 Have both compound and simple eyes, most adults
have just 2 compound eyes that may cover much of the
head
Success of Insects
 Found everywhere except in deep part
of ocean
 Very short life span & rapidly adapt to
new environments
 Small size helps minimize competition
in habitats
 Flight helps escape predators & move
into other environments
Defense Mechanisms
 Wasps & bees can sting
 Some insects use camouflage to
blend into their environments
 Some insects taste bad & have
warning colorations
 Some insects spray noxious chemicals.
Environmental Impact
 Pollinate almost 2/3's of all plants
 Serve as food for fish, birds, & mammals
 Help recycle materials (termites recycle
wood)
 Make useful byproducts such as silk &
honey
 Some spread disease
 Agricultural pests
Crabs, Lobsters, Crayfish, &
Shrimp
Subphyla Crustacea
 Most are aquatic, w/gills
 Have mandibles for crushing food; move side to side
instead of up and down
 5 pair walking legs used for walking, for seizing prey,
and for cleaning other appendages
 1 pair antennae and 1 pair antennules
 2 compound eyes which are usually on movable stalks
 Swimmerets, located on abdomen, create water
currents, which enhance aeration of gills; some
females use them to hold eggs until hatching, males
use it as a copulatory structure