Athropods Flashcards
What is arthropoda
A phylum found within the superphylum Ecdysozoa
Panarthropoda additionally encompass..?
Tardigrada and Onychopohora
How many species of water bears are there
And what conditions can they survive in
1250
Water-dwellers, found nearly everywhere
Can survive, extreme temp, pressure, space vacuum, radiation, lack of water.- cryptobiosis
What are onychopohora
Velvet worms
How many species of onychophora are there
200
Convergent similarities to annelids
Shoot slime from appendages on the head
Most give birth to live young viviparous
What are the four extant subphyla that arthropods can be split into
Hexapoda
Crustacea
Myriapoda
Chelicerata
Hexapods include what?
Winged insects and other wingless arthropod groups
What are the major orders of insects?
Beetles, butterflies and moths, ants, wasps and bees, flies
Could be 30 million species of insects in total
Some undergo metamorphosis
What do crustacea include
Lobsters, crabs, crayfish, shrimp, krill, barnacles, and woodlice
Mainly marine, some fresh water and terrestrial
Key trophic link in marine ecosystems between primary producers and higher level consumers
Huge morphological diversity
What do myriapods include
Centipedes and millipedes
Centipedes always have odd number of leg pairs, poison fanged nocturnal active hunters
Millipedes eat rotting gveg and wood, secret noxious chemicals as a defence mechanism
What are chelicerata
Ticks and mites, scorpions, and spiders
Called chelicerata due to chelicerae appendages (pincers)
Important pests, parasites, and predators
Independent invasion and radiation in dry land habitats compared to insects
What are trilobites
Extinct subphylum - existed for 300 million years.
Abundant, widely distributed in the sea
had 10 orders and over 17000 species
Fossils date back to 520mya
Extinction due to competition with crustaceans, and predation pressure from early fish
Crustacea are …?
Paraphyletic
Hexapods have evolved from who?
Crustacean ancestor
Placement of myriapods are..?
Not resolved
How many years ago did arthropods emerge
540mya
What are the defining features of arthropods
They have segmentation, joined appendages, and exoskeleton
What is segmentation
The common ancestor of all arthropods had a series of similar segments - homonomous
Segments in extant derived taxa are often fused/lost, specialised.. heteronomous
Segmentation is still apparent during embryonic development
What is tagmosis
Tagmosis was independent between insects, crustaceans+ chelicerates
The grouping of segments with similar functions/structures
All arthropod grouped segments to form a head - specialised region for feeding, sensing, and neural integration
Most divide the rest of the body into a thorax and abdomen
Chelicerates fused head with thorax region to form a cephalothorax
Segmentation:appendages
Ancestor had appendage on each segment
Arthropods have evolved a wide range f specialised paired appendages
Appendages themselves are segmented - called articles
Appendages on head specialised for feeding and sensing
Others for locomotion, reproduction, respiration, food manipulation etc…
Jointed appendages
Joints allow articulation between appendage articles despite hard exoskeleton
Flexible cuticle at the joint that allows bending
Antagonistic muscles control joint movement
Flexor and extensor muscles allow movement of articles relative to each other
Protractor and retractor muscles allow appendage extension/retraction
What does the cuticle do
Provides support, maintains shape, joint articulation, protection against pathogens and mechanical forces
Made from chitin
Properties range from hard carapace shells to stretchy tendons
Controlled by sclerotisation - where tanning leads to cross-linking and stronger propoerties
Moulting
Takes place to permit growth. Ecdysis - cuticle periodically moulted to permit growth
Pre moult, moult, post moult, inter moult
Intermoult period can only be 10% of the arhtropod’s life
Arthropods are major vectors for what
Disease. 700million people a year get a mosquito borne illness
Vectors include ticks, fleas, lice, bugs and other flies
What are parasitic form of arthropoda
Ticks, mites, flies, fleas, lice and various crustaceans inc. tongue worms and copepods
Mainly ectoparasites some are endoparasites
Some wasps and flies are parasitoids
What useful tasks arthropods do for humans
Pollination of crops, recycling, pest control
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