CHAPTER 26 - ARTHROPODS

Class Arachnida (Spiders & their Relatives)

 Characteristics of All Arachnids (Spiders, Scorpions, Mites, and Ticks)

• 2 Key Appendages:

 Chelicerae:

Pedipalps:

• 2 main body regions 

Cephalothorax:

Abdomen:

• _____ pairs of legs (____ legs total)

• _____ body segments

• Respiratory organs (Breathing) =  ____________________________

• Excretory Organ (Waste Elimination)  = ________________________

• Most are ______________________ (Exception = spider)

 Spiders

• 35,000 species (only _____ species have a harmful bite to humans)

• Habitat: Majority land dwellers; some freshwater

• Predators (they will eat any other animal of manageable size)

• 1^st Arthropods to colonize land

Adaptations to live on land: 

• _____________________________________ -   Efficient excretory organs; allow for excretion of wastes with little water loss 

• _____________________________________ - Respiratory organ, inside the body. Allows for gas exchange (breathing) area to remain moist without losing large amounts of water.   

Air -> _____________________ (openings) -> ____________________ -> oxygen from air is moistened -> dissolved into blood stream

• _______________________________________________ on chelicerae allows spiders to obtain prey on land (defense mechanism, feeding mechanism)

• __________________________________________ has given spiders habitat on land.

• ________________________ - Small, nozzle-like structures at the end of the spider’s abdomen used to produce silk.

Common functions of Silk include:

Courtship Rituals of Spiders

•  Most spiders have elaborate __________________________________________

• _____________ smaller than __________________

• Spiders are usually __________________ animals

• Females will sometimes ____________ and ____________ the male after mating (Black Widows)

Scorpions

•  Share land adaptation with spiders, such as __________________________ & ___________________________________________

• Instead of chelicerae (clawlike poison glands in spiders), scorpions have _________________________________

• Instead of having pedipalps (spiders), scorpions have ________________________  _________________________

• Eat insects

• Have a _____________________ at the tip of abdomen

• Feeding Mechanism: 

• Habitat: 

• Sting is painful, but not lethal to humans

• Elaborate mating rituals

Mites 

• Feeding Mechanism:

• Direct/ Indirect effects on humans:

* Punch holes in skin; cause severe itching
* Carry viruses that damage food crops
* Cause feather loss in birds; mange in dogs
* Cause decreased wool production in sheep

 Ticks

•  Feeding Mechanism:

• Transmit Disease to Humans:

Horseshoe Crabs 

• More closely related to ____________________ than __________________

• Feeding Mechanism:

Class Insecta (Insects, Millipedes, Centipedes)

 Insects (Grasshoppers, beetles, termites, fleas, ants)

_________________________ - The study of insects

•  First animals to evolve _______________

• Most live __________________ in highly organized societies of related individuals

• 3 body regions:

• ____ pairs of legs (_____ legs total)

• ________________________ - Appendages that are specialized for sensing the environment

• Have _________________________ (chewing mouthparts) instead of chelicerae. Chewing mouthparts are specialized for eating a variety foods. They have evolved into highly specialized shapes for _____________________, ____________________, ______________________ & _______________________

• Legs have evolved into a variety of shapes for:

Adaptations to live on land:

• _____________________________________ - Chief organs of respiration; Tubules that deliver oxygen directly to muscle cells 

• _____________________________________ - Allows them to retain water on land 

• _____________________________________ - Allow for excretion of wastes with little water loss

Development in Insects

 Direct Development (Spiders, scorpions, ticks) – A miniature copy of the adult form hatches from the egg.

Incomplete Metamorphosis (Grasshoppers, dragonflies, mayflies, cockroaches) –

Nymph – A smaller version of the adult, similar structure without wings or a mature reproductive system

Complete Metamorphosis (Flies, beetles, ants, wasps, bees, butterflies, moths) –

      Larva – Immature form of an insect  (ex: caterpillar)

      Pupa Stage  - Insect forms a cocoon; tissues & organs are replaced with new ones.

Insects can be Harmful:

* Eat plants
* Transmit diseases to plants and animals (sleeping sickness, malaria)
* Become resistant to pesticides

Insects can be Beneficial:

* Pollination of food crops
* Production of silk (caterpillars of silk moths), honey & beeswax (bees)
* Food source in some parts of the world (grasshopper tacos – yummy!)
* Stabilize ecosystems

 Millipedes “Thousand feet”

• ______ pairs of legs per segment

• Habitat:

• Feeding Mechanism:

Cenitpede “Hundred feet”

• ______ pair of legs per segment; 1^st pair of limbs has evolved into large clawlike structures used to ________________________________________________

• Habitat:

• Feeding Mechanism:

Class Crustacea  (Crayfish, lobsters, pillbugs, beach hoppers, barnacles, copepods)

Characteristics of Crusteans  (successful Aquatic Arthropods)

• Most have ______ pairs of legs

• ______ body regions:

• Have _____________________ for sensing the environment & detecting prey

• Habitat:

• Have _______________________ for many types of locomotion:

• Have ____________________ (chewing mouthparts; jaws)

Cannot live on Land because:

•  __________________________________________________________________ 

• __________________________________________________________________ 

• __________________________________________________________________

Decapods “10 feet”    (Lobsters, shrimp, crabs, crayfish)

• ______ pairs of thoracic legs; 1^st pair is a set of ____________ for food gathering & defense

• Lobsters, shrimp, crayfish have a __________________________________ abdomen

• Crabs have a ________________________________ abdomen

Isopods  “Equal feet”    (Pill bugs & relatives)

• ______ pairs of similar walking legs

• Habitat:

• Respire through ________________

Amphipods  “Two different kinds of feet”    (Beach hoppers)

• Habitat:

Barnacles: 

• Spend most of their lives attached to a ___________________________________

• Live inside the walls of their calcium shells, which are attached to hard surfaces

Daphnia  (Water Flea)

• Eat phytoplankton

• Preyed upon by young fish & hydra

Copepod 

• Part of the zooplankton

• An important link in the aquatic food chain