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phylum Arthropoda
- There are about 10 to the 18th Arthropods alive on Earth
- By Diversity, distribution and numbers Arthropods are the most successful phylum
- Arthropod fossils date to the Cambrian Explosion (535-525 MYA)
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trilobites
- Arthropods
- Very successful and diverse
- –17,000 known species
- –Marine habitats
- lasted from the Cambrian to the Permian period
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what makes an arthropod an arthropod
- cuticle- the exoskeleton covering made of chitin and proteins
- requires molting for growth
- provides structural strength for animals on land
- sensory organs
- –Eyes
- –Smell receptors
- –Antennae for touch and smell
- open circulatory system
- hemolymph
- gas exchange is done by different organs
- –Aquatic species use gills
- –Terrestrial species use internal surfaces specialized for gas exchange
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hemolymph
is moved by the heart into spaces around tissues and organs called sinuses
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the arthropod body plan consists of?
- –segmented body
- –hard exoskeleton
- –jointed appendages
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arthropods have what genes?
- homeotic genes: sequences in the genome that provide location info
- –In plants: MADS-box genes
- –In animals: Hox (or HOM) genes
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what do hox genes do?
- control the body plan of the embryo along the anterior-posterior (head-tail) axis during development
- these genes 'tell' cells where they are
- mutations in the hox genes result in misplaced structures
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what are the patterns of hox genes
- Hox genes have increased over time
- –Multiple copies indicate gene duplication events
- –Most vertebrates have 4 Hox clusters
- –Ray-finned fish have 8
- –Echinoderms have 1
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subphylum Cheliceriformes
- Cheilos–lips; cheir–arms chelicerae- pinchers or fangs
- body composed of two parts
- cephalothorax
- abdomen
- no antennae
- earliest were water scorpions
- Most marine species extinct except for
- –Sea spiders and horseshoe crabs
- Horseshoe crabs
- –Used in medical research and testing
- –Used as bait
- –Declining populations may be affecting the Red Knot and sea turtle populations
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arachnids
- (cheliceriformes)
- –Largest group
- –Scorpions
- –Spiders
- –Ticks
- –Mites
- Cephalothorax has six pairs of appendages
- –Chelicerae
- pedipalps- used for sensing, feeding, reproducing
- –Four pairs of legs
- Spiders
- –Chelicerae used to deliver poison and secrete digestive juices
- –Drink their prey
- –Book lungs used for gas exchange
- –Silk is liquid protein used in webs and prey capture
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cheliceriformes cause many dieseases, examples?
Lyme disease–Colorado tick fever–Tularemia–Relapsing fever–Babesiosis–Q fever
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subphylum Myriapoda
- Millipedes and Centipedes
- All are terrestrial
- All have pair of antennae and three pairs of modified appendages serving as mouth parts
- Segmented with two pairs of legs per segment in millipedes and one pair in centipedes
- Millipedes are detritivores
- Centipedes are carnivores
- -have poison claws
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detritivores
feed on detritus or organic waste
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subphylum hexapoda
- More species in Hexapoda than all other forms of life combined
- Insects and springtails
- Six legs
- Terrestrial, and fresh water
- Flying species numerous
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incomplete metamorphosis
- Nymphs (young) resemble small adults
- –Series of molts making nymph look more like adult
- –Final molt produces
- Sexual maturity
- Wings
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complete metamorphosis
- –Specialized larval stage (grub, caterpillar, maggot)
- –Larval stage looks different than adult
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Coleoptera
- Coleoptera-beetles
- 350,000 species
- Complete metamorphosis
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Diptera
- flies and mosquitoes
- 151,000 species
- Complete metamorphosis
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Hymenoptera
- ants, bees, and wasps
- 125000
- social insects
- complete metamorphosis
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Orthoptera
- grasshoppers, crickets, katydids
- 20000+
- incomplete metamorphosis
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subphylum Crustacea
- Variable numbers of appendages
- Gas exchange across cuticle or by gills
- Isopods
- Decapods
- Copepods
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isopods
- wood lice and many other species
- terrestrial, marine, fresh water
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decapods
- lobsters, crabs, and shrimp
- carapace is hardened cuticle on dorsal cephalothorax
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copepods
- krill and other species
- planktonic crustaceans
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phylum Echinodermata
- Deuterostomes (like chordates)
- Bilatera
- –Larvae are bilateral
- –Adults not truly radial
- Sea stars, urchins, sea cucumbers
- Water vascular system
- –Used for movement, feeding, gas exchange
- Sexual, usually with broadcast spawning
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