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Arthropods

Arthropods. Chapter 2 Section 2. Arthropods. What are some examples of common arthropods? Insects Spiders Crabs Lobsters Centipedes Scorpions. Arthropods. Earth has more species of Arthropods than all of the other animals combined

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Arthropods

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  1. Arthropods Chapter 2 Section 2

  2. Arthropods • What are some examples of common arthropods? • Insects • Spiders • Crabs • Lobsters • Centipedes • Scorpions

  3. Arthropods • Earth has more species of Arthropods than all of the other animals combined • Today scientists have identified 875,000 different arthropod species • There are most likely more that we have not yet identified!

  4. Characteristics of Arthropods • Phylum Arthropoda • Invertebrate • External Skeleton • Segmented Body • Jointed attachments • Appendages

  5. Characteristics of Arthropods • Phylum Arthropoda • Arthros means “joint” in Greek • podos means “foot” or “leg” • Jointed legs are a distinct characteristic

  6. Characteristics of Arthropods • Phylum Arthropoda • Open circulatory system • Blood leaves the blood vessels and bathes the internal organs • Most reproduce sexually • Most are either male or female • Most have internal fertilization

  7. Skeleton • What is an exoskeleton? • Outer skeleton that protects the animal • Helps prevent the evaporation of water • Waterproof shell • Why do they need to have a shell that keeps them wet? • Keep from drying out!

  8. Skeleton • 1st animals to move out of water and onto land • What permitted the arthropods to move onto land? • Exoskeleton

  9. Skeleton • What is the material that the exoskeleton is made of? • Chitin • Chitin: • Long molecules which are built from many smaller building block – like links in a chain • This is a polymer • These molecules make chitin tough and flexible

  10. What happens to the exoskeleton as the animal grows larger? They shed their exoskeleton They grow a new, larger one in its place What is the process of shedding called? Molting After an arthropod molts it is soft for awhile and has less protection from danger Skeleton

  11. Segmented Bodies • What are the three segments called? • Thorax • Abdomen • Head

  12. Segmented Bodies • This body plan is easiest to see in centipedes and millipedes because they have identical segments • Where else can we see segments? • Tails of shrimp and lobster

  13. Appendages • Why do arthropods have appendages? • Give the animal flexibility • Enable it to move • What are some common appendages? • Wings • Mouthparts • Legs

  14. Appendages • Tend to be highly specialized tools • Ex: The mouthpart of a crayfish is used to crush food • Antenna: • Appendage on the head that contains sense organs • A crayfish antenna is used for smelling, tasting, touching, and keeping balance

  15. Appendages • Other appendages • Legs: • Walking • Crayfish use their 1st pair of legs which have claws for catching prey and defense • Wings: • Used for flying / movement

  16. Origin • Segmented worms and arthropods – what do they have in common? • Both have segmented bodies • Have appendages attached to some segments • Due to these similarities scientists infer that these two groups have a common ancestor • DNA shows that they are not as close as we thought

  17. Origin • Have been on Earth for 540 million years • 1st arose from the oceans • Today they live everywhere • Some are adapted to fresh or salt water • Crayfish • Crabs

  18. Crustaceans • Major groups • Crustaceans • Arachnids • Centipedes • Millipedes • Insects

  19. Crustacean • Crustacean: • Arthropod that has 2 or 3 body sections • Usually 3 pairs of appendages for chewing • 5 or more pairs of legs • Each body segment has a pair of legs or modified legs attached to it • Only arthropod to have 2 pairs of antennae

  20. Crustaceans • Most begin their life as microscopic, swimming larvae • Example: crabs, barnacles, and shrimp • The larvae form does not resemble the adult form • Metamorphosis: • Process in which an animal’s body undergoes dramatic changes in form during its life cycle • Develop from a larvae into an adult

  21. Crustaceans • Live in nearly any watery environment • Obtain oxygen through their gills • Thrive in freshwater, lakes, rivers, and even puddles

  22. Crustaceans • What and how do they eat? • Eat dead plants and animals • Eat animals they prey on • Some have appendages to stun their prey • Ex: pistol shrimp • Eat plantlike microorganisms • Krill

  23. Spiders & Their Relatives • Arachnid: • Arthropod with only 2 body sections • Cephalothorax • Abdomen • Abdomen: • Contains the reproductive organs • Part of its digestive tract

  24. Spiders & Their Relatives • Have 8 legs • No antennae • Use book lungs to breathe • Tiny network of tubes that lead to the openings of the exoskeleton

  25. Spiders • All spiders are predators • Most eat insects • Some run their prey down others catch them in their web • Have hollow fangs with venom • Turns the tissue into mush • Most bites do not harm humans

  26. Mites • Parasites • Examples: • Chiggers • Ear mites (dogs and cats) • Dust mites • Allergic to the exoskeleton • Mites are everywhere • Even in fresh water and the ocean

  27. Ticks • Parasites • Live on the outside of a host • Nearly every kind of land animal has a species of tick that sucks its blood • Some carry disease • Lyme Disease is spread by deer tick

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