1. Arthropods

2. What are ARTHROPODS? Coelomate Segmented Bilateral Symmetry
Exoskeleton – made of protein and chitin
Jointed appendages – any structure (leg or antennae) that grows out of the body

3. What are Arthropods?
earliest invertebrates to exhibit jointed appendages
Jointed appendages are an advantage because they allow more flexibility for animals with hard, rigid exoskeletons
Joints allow powerful movements and allow appendages to be used in many ways

4. What are Arthropods?
Appendages
Jointed Appendages

5. Exoskeletons Provide Protection
made up of protein and CHITIN
can be a continuous
covering over most
of body OR
made of plates
that are held
together by hinges
Continuous
Hinged

6. Exoskeleton Advantages
Protects, supports internal tissues
Provides place for muscle attachment
Aquatic arthropods have exoskeleton reinforced with calcium carbonate

7. Exoskeleton Disadvantages
Heavy
the larger the animal, the thicker and heavier the exoskeleton
Exoskeletons don’t grow
animals must molt when they get too large for exoskeleton

8. Molting Animal contracts muscles and takes in air or water
Body swells and causes exoskeleton to split open, usually along the back
Most arthropods will molt 4-7 times before becoming an adult.

9. Before the new exoskeleton hardens...
increased circulation to all parts of the body cause the animal to puff up and new exoskeleton hardens leaving some “growing room”
animal can’t protect itself, can’t move

10. Question 1
Which of the following organisms would be most likely to have an exoskeleton reinforced with calcium carbonate?
Spider
Beetle
Crab
Dragonfly
Correct!

11. Question 2
Exoskeletons are heavy. Why can aquatic arthropods grow so much larger than terrestrial arthropods?
The buoyancy of the water helps support the weight of the exoskeleton

12. Question 3
What is one advantage and one disadvantage of flying arthropods having a thinner, lighter weight exoskeleton?
Disadvantage: less protection
Advantage: greater freedom to fly and jump

13. Question 4
What is one advantage and one disadvantage of having a cephalothorax?
Disadvantage: less flexibility, mobility
Advantage: more protection

14. Segmentation
3 segments
abdomen
thorax
head

15. Segmentation Sometimes these segments can be fused together
some have head and fused thorax and abdomen
some have abdomen
and fused head and
thorax (cephalothorax)

16. Respiration Efficient respiratory systems to meet large O2 demands
Large O2 demand needed to sustain high metabolism for fast movements
3 types of respiratory structures
gills (aquatic arthropods)
tracheal tubes (terrestrial arthropods)
book lungs (terrestrial arthropods)

17. Respiration Gills water moves over gills O2 from water diffuses
into gills and into
bloodstream
CO2 from body diffuses out through gills into surrounding water

18. Respiration Tracheal tubes
branching network of hollow air passages that take air throughout the body
Muscle movement brings air in/out through SPIRACLES (openings in abdomen and thorax)

19. Respiration Book lungs spiders and relatives
air filled chambers with leaf-like plates
stacked plates
are arranged
like pages
of a book

20. Antennae Acute sensing by antennae
stalk like structure that can detect changes in the environment
movement
sound
chemicals
Used for sound and odor communication

21. one pair of compound eyes and 3-8 simple eyes
visual structure with
many lenses
Simple Eyes
visual structure with one lens for detecting light
one pair of compound eyes and 3-8 simple eyes

22. Nervous System Double ventral nerve cord Anterior brain
Several fused ganglia that control the body section they are located in

23. Circulatory System Open circulatory system
blood flows away from the heart in vessels
blood flows out of vessels into tissues
blood returns to the heart through open spaces

24. Digestive System
Complete digestive system with mouth, intestine, and anus
Mouth has 1 pair of jaws called MANDIBLES
adapted for holding, chewing, sucking, or biting

25. Reproduction – Sexual and Asexual
Sexual reproduction
separate sexes
internal fertilization for terrestrial species
external fertilization for aquatic species

26. Reproduction – Sexual and Asexual
Asexual reproduction
PARTHENOGENISIS
a new individual develops from an unfertilized egg
seen with ants, aphids and bees

27. Arachnids spiders (largest group), ticks, mites, and scorpions
2 body regions: cephalothorax and abdomen
6 pairs of jointed appendages – 12 total appendages!

28. Arachnids 1st pair - chelicerae, are near the mouth
modified into pincers (hold food) or fangs (inject poison)
chelicerae

29. Arachnids 2nd pair – pedipalps, for handling food and sensing

30. Arachnids Silk, for webs, is secreted by silk glands in the abdomen
as it is secreted, it is spun into thread by SPINNERETTES
spiders are predatory and feed almost exclusively on other animals

31. Arachnids Ticks and mites have only 1 body section
Head, thorax and abdomen are completely fused
Ticks feed on blood of other animals

32. Arachnids Mites feed on fungi, plants, and animals
small – not usually visible
can transmit diseases
Dust mites

33. Arachnids Scorpions have many abdominal body segments Enlarged pincers
Long tail with
venomous stinger
at the tip

34. Crustaceans crabs, lobster, shrimp, crayfish, barnacles
Only arthropods with 2 pairs of antennae
mandibles – move
from side to side
2 compound
eyes

35. Crustaceans 5 pairs of walking legs 1st pair are claws for defense

36. Crustaceans Most are aquatic and use gills
pill bugs (roly-polies) live on land, but must have moisture to aid in gas exchange
Yes! This is a crustacean!

37. Centipedes and Millipedes
Centipedes are carnivorous – eat soil arthropods, snails, slugs,
and worms
Bites can be painful
Millipedes – eats plants and dead material on damp forest floors
Does not bite, but does
spray foul-smelling fluid

38. Horseshoe Crabs Class Merostomata
“Living Fossils”- unchanged for 220 million years (Triassic period)
Extensive exoskeleton
Live in deep coastal waters
forage bottoms for algae,
annelids and molluscs

39. Insecta Flies, grasshoppers, lice, butterflies, beetles
3 body segments
6 legs
Very diverse - more insects than all other classes of animals combined

40. Insecta mate once in lifetime internal fertilization some exhibit
parthenogenesis
large number of eggs
to increase survival rate

41. Insecta insect embryos develop inside eggs, eggs hatch
some look like miniature adults
will molt several times until adult size
Molt
Nymph
Eggs
Nymph
Molt
Adult

42. Insecta INCOMPLETE METAMORPHOSIS Nymphs can’t reproduce
3 stages: egg, nymph, adult
Nymphs can’t reproduce
Nymph gradually becomes an adult

43. Insecta Some undergo COMPLETE METAMORPHOSIS
4 stages: egg, larva, pupa, adult
Metamorphosis is controlled by chemical substances in the insect
Egg
Adult
Larva
Pupa

44. Insecta Incomplete metamorphosis: grasshoppers and cockroaches
Complete metamorphosis: ants, beetles, flies, wasps

45. Origins of Arthropods Successful because of varied life styles
high reproductive output
structural adaptations
hard exoskeletons
jointed appendages

46. Origins of Arthropods
Hard exoskeletons fossilize – a lot is known about evolutionary history
Evolved from ANNELIDS (segmented worms)
Arthropods have more complex segments, more developed nervous systems
circular muscles in annelids do not exist in arthropods

47. Question 5 Spiders are: Predators! predators scavengers decomposers
parasites
Predators!

48. Question 6
Having 2 pairs of antennae distinguish _________ from other arthropods.
centipedes
millipedes
crustaceans
horseshoe crabs
Crustaceans!

49. Question 7 Why are horseshoe crabs called “living fossils?”
They remain unchanged after 220 million years!