Transcript Arthropods - Green Local Schools

Arthropods
Chapter 36
Chapter 36
Phylum Arthropoda
Section 36.1
Arthropods
• Examples: lobsters, crabs, spiders,
millipedes, centipedes, insects
• Arthropod means “jointed foot”
▫ Appendages: body segments with jointed
extensions
 Used in feeding, moving, & mating
Characteristics:
• Exoskeleton
▫ Protection, support, prevents desiccation
▫ 3 layers excreted by epidermis
▫ Made of chitin
• Compound eye
▫ Optic nerves send impulse to the ventral nerve
cord
• Open circulatory system
Molting:
• Periodic shedding of the exoskeleton to
allow growth
• Few day process to develop hard
exoskeleton – extremely vulnerable times!
• Hormone, pressure, and enzyme induced
▫ enzymes digest old exoskeleton while
synthesizing new one
Evolution:
• 545 million years ago
▫ All from a common ancestor
• Tagmata: fused segments that perform a
specialized function of modern arthropods
• 5 subphlya
Classification: 5 Subphyla
1. Trilobita:
▫ (trilobites)
• Extinct!
2. Crustacea:
▫
(shrimp, lobster, crayfish, pill bugs,
barnacles)
3. Chelicerata:
▫
(spiders, scorpions, ticks, horseshoe crab)
4. Myriapoda:
▫
(centipedes, millipedes)
5. Hexapoda:
▫
(insects, springtails)
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Subphylum Crustacea
Section 36.2
General Information:
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“Crusta” means shell
Most are aquatic
Defining characteristic = 2 pairs of antennae
Exoskeleton:
▫ Made up of chitin (protein) or CaCO3
▫ Carapace has waxy coating
▫ 16 to 20 body segments that fuse to form
tagmatas
General Information:
• Many have mandibles
▫ jawlike mouthparts
• Usually each segment has at least 1 pair of
appendages
• Open circulatory system
• Many respire with gills (aquatic only)
• Nauplius
▫ Free swimming larvae
Crustacean Diversity
• Aquatic:
▫ Plankton – collection of small animals that
drift near the surface of the water
 Copepods (crustaceans) are a part of plankton
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Water flea
Barnacles
Shrimp
Lobster
Crabs
Crayfish
• Terrestrial: Isopods
▫ Pill and sow bugs
▫ Lose water quickly
Crayfish
• Decapods – “ten feet,” five pairs of legs
THIS IS WHAT WE
WILL BE DISSECTING
– WEAR CORRECT SHOES!
External Structure
• Two major sections:
▫ Cephalothorax: two tagmata
 Head – 5 segments
 Thorax – 8 segments posterior to head
 Carapace – dorsal exoskeleton
▫ Abdomen:
 7 segments
 Telson – 7th segment,
 flat paddle at posterior
Appendages:
• Antennules – touch, taste, equilibrium
• Antennae – touch, taste
• Mandible – chewing
• Maxilla – manipulate food, draw water over
gills
• Maxilliped – touch, taste, manipulate food
• Cheliped (claws) – capture food, defense
• Walking legs – locomotion over solid
surfaces
• Swimmeret – create water currents, transfer
sperm (male), carry eggs and young
(female)
• Uropod – propulsion during tailflips
Digestion:
• Digestive System: mouth  esophagus 
stomach  enzymes secreted by digestive
gland  intestine & digestive gland  anus
Respiration:
• Respiratory System:
▫ gills
 Base of each walking leg under carapace
 Diffusion of gases
Excretion:
• Excretory System: green glands
▫ Acts like a kidney
▫ Eliminate excess water due to hypotonic
environment
Circulation:
• Circulatory System:
▫ open system baths organs in hemolymph
▫ Pumping organ: heart (dorsal)
Neural Control:
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Brain = pair of ganglia above esophagus
Ventral nerve cord
Sensory hairs on exoskeleton
2,000 light sensitive units on each eye
Statocyte at base of antennae for balance
Reproduction:
Sexual: mate in fall
▫ Male’s first 2 hollow legs transfer sperm
▫ Female holds sperm until eggs laid, then
fertilize; mated previous fall
▫ Eggs laid in spring (100)
▫ carried by female on swimmerets 6-8
weeks; “berried”
• regenerate missing parts
Female
Male