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Phylum Arthropoda. General Characteristics. Arthropod = jointed feet Largest group of animals 80% of described species 30-50 million species Most varied. General Characteristics Con’t. Metamerism (body divided into segments) Head, abdomen, thorax Paired, jointed appendages - PowerPoint PPT Presentation
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Phylum Arthropoda
General Characteristics
• Arthropod = jointed feet• Largest group of animals
–80% of described species–30-50 million species
• Most varied
General Characteristics Con’t• Metamerism (body divided into segments)
–Head, abdomen, thorax• Paired, jointed appendages• Ecdysis-molting (growth)• Open Circulatory System (means no vessels)• Complete digestion tract
Metamerism (Body Segments)
3 Segments 2 Segments
General Characteristics Con’t• Ventral Nervous System• True exoskeleton• Metamorphosis• 5 Subphylum
–Trilobitomorpha, Myriapoda, Chelicerata, Crustacea, Hexapoda
Exoskeleton
• Functions of exoskeleton–protection–Gas exchange–Minimize H2O loss–Muscle attachment
Exoskeleton Structure
• Composed of chitin – a carbohydrate
• Epicuticle: outer layer –Water proof
• Procuticle: inner layer–Made of chitin
Ecdysis (molting)
• 3 step process–1. Enzymes digest old exoskeleton–2. New exoskeleton secreted
New exoskeleton is soft–3. Scleratization (hardening)
Ecdysis (molting)• Molting is important for arthropod
growth–Can’t grow in a suit of armor
• Is also a dangerous time for arthropods–Typically animals about to molt, will
go into hiding just before the process begins
Metamorphosis
• Changes in body form from larval to adult–Ex. Butterfly, Dragonfly
• Reduces competition for food and living space (*)
Subphylum Trilobitomorpha
• MOST PRIMITIVE!• All extinct and marine• Body with 3 sections
Subphylum Myriapoda
• Myriapoda- “many legs”• Millipedes, centipedes• Paired legs• Terrestrial
Millipedes vs. Centipedes
• Millipedes:–Herbivorous–Appear to have 2 legs per
segment–Slow–Non-venomous
Centipedes
–Carnivorous–Have only 1 pair of legs per
segment–Faster–Venomous
Subphylum Chelicerata
• Spiders, mites, ticks, scorpions, horseshoe crabs,
• Have chelicera - fangs• 2 Segments
–Cephalothorax (head-chest)
–Abdomen
Feeding
• Appendages:–1st pair- chelicera: feeding
(often fang-like)–2nd pair- Pedipalps: feeding,
locomotion, reproduction
Subphylum HexapodaINSECTS
General Characteristics
• Hexapoda = “six legs”• Includes the class Insecta
–30 million species–27 Major orders
•We will only learn 8
General Characteristics Con’t
• 3 pairs of legs–6 total
• 1 pair of antennae• Most have 2 pairs of wings• Compound eyes (2) and Oscelli (3
in middle)• 3 part body plan
–Head, Thorax, Abdomen
Insect Flight
• Is a unique trait to the insects• Different insects have wing
modifications for specific functions
Economic Importance Parasites
Ticks, fleas Are considered agricultural pests.
1949-European corn borer caused $349 million in damage to the US corn crop
Economic Importance Con’t
• Provide goods–Honey–Beeswax–Yummy (to certain cultures)–Silk–Dyes
Economic Importance Con’t
• Also are vectors for many diseases–Bubonic plague (flea)–Malaria (mosquito)–West Nile Virus(mosquito)–African Sleeping Sickness (Tsetse
fly)
Subphylum Crustacea
General Characteristics Includes crabs, lobsters, crayfish,
shrimp, and barnacles
Carapace – “shell” that protects organs (like a turtle)
Biramous Appendage: branched Y-shaped appendages
General Characteristics Con’t
HabitatMarine and Freshwater
2 or 3 body segmentsHead, Thorax, and Abdomen
ORCephalothorax and Abdomen
Reproduction• Sexual reproduction (most
external, some internal)• Few monoecious
(hermaphroditic)
Females retain eggs until hatching
Economic Importance
• Tasty—people like to consume them
Ecological Importance
• Scavengers-eat dead material• Basis of food chain(shrimps, barnacles)• Keystone species