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Flashcards in Zoology Test 3a Deck (65):

Subphylums of Arthropoda

- Trilobita
- Chilicerta
- Crustacea
- Myriapoda
- Hexapoda


classes of Chilicerta

- Merastomata
- Arachnida


types of Merastomata

horseshoe crabs


types of Arachnida

- spiders
- ticks
- mites
- scorpions


ticks and mites are from what order?



types of Crustacea

- crabs
- lobsters
- crayfish
- krill
- decapods
- isopods
- barnacles


classes of Myriapoda

- Chilopoda
- Diplopoda


what is a Chilopoda



what is a Diplopoda



classes of Hexapoda

- Insecta


what does arthropoda mean

jointed foot because of appendages


arthropod diversity

- largest phylum by far
- 75% of known animal species
- over a million recognized species


What are arthropods so successful?

- versatile exoskeleton
- segmentation and appendages for more efficient locomotion
- air piped directly to cells
- highly-developed sensory organs
- complex behavioral patterns
- limiting intraspecific competition through metamorphosis


versatile exoskeleton

- suit of armor (cuticle) with flexible joints, secreted by epidermis
- primarily chitin
- cuticle is flexible and lightweight but also affords protection, particularly against dehydration
-cuticle of crustaceans is impregnanted with calcium salts, unlike cuticle of other arthropods which makes it harder



tough, resistant, nitrogenous polysaccharide that is insoluble in water, alkalis and weak acid


disadvantages of exoskeleton

- must be molted since it not alive and does not grow
- 4 to 7 times for those that stop molting at adulthood



takes energy and leaves organism vulnerable, shedding of exoskeleton
- takes 24 to 48 hours for exoskeleton to reharden


segmentation and appendages for more efficient locomotion

- there is considerable fusion and reduction of segments especially in the adult stages of life cycle
- some segments are extensively modified for sensory functions, food handling, swift and efficient walking, and swimming
- crayfish
- jointed appendages, jointed parts consist of hollow lever moved by internal muscles>>gives them great strength


air piped directly to cells

- terrestrial arthropods have highly efficient tracheal system which delivers oxygen directly to tissues and cells and makes high metabolic rate possible
- disadvantage: limits body size, because it is difficult to get air to every part of large body


respiration in arthropods

- efficient gills
- attached to bases of walking legs in some crayfish


highly-developed sensory organs

- arthropods are keenly alert to what is happening in environment


example of complex organ system in crustaceans and insects

compound eye


example of complex organ system in grasshopper tympanum

- enables grasshoppers to hear sound
- arthropods were first group to communicate via sound
- aware of sound waves and vibrations


example of complex organ system in silkworm moth

- antennae enables males to located females by sensing presence of pheromones
- female releases pheromone downwind and male follows concentration gradient to find her for mating


complex behavioral patterns

highly organized behavior in social insects


limiting intraspecific competition through metamorphosis

- many arthropods undergo metamorphosis meaning larva and adult are not competing with each other since feed on different foods
- two kinds of metamorphosis



- type of metamorphosis
- complete metamorphosis
- butterfly



- type of metamorphosis
- incomplete metamorphosis
- beetle
- gradual change


arthropod nervous system

- basic layout similar to that of annelids
- single ventral nerve cord and dorsally-located cerebral ganglia with circumesophageal connectives
- complexity of nervous system considerably advanced over annelids


osmoregulation and excretion in crustaceans

have gills through which nitrogenous wastes are lost via diffusion and antennal glands for osmoregulation


osmoregulation and excretion in terrestrial arthropods

have malpighian tubules for osmoregulation and excretion
- this is why they can live in hot, dry climates; very efficient


circulation in aquatic forms

an open circulatory system with heart and arteries
- no veins
- no separation of blood from interstitial fluid
- hole in heart called ostia which allows blood to seep back into heart


circulation in terrestrial forms

- single dorsal vessel is only blood vessel
- dorsal vessel pumps hemolymph conisitng of plasma and amebocytes
- has little to do with oxygen transport since trachea leads oxygen straight to cell


mouthparts found among insects

-biting or chewing (grasshopper)
- sucking, piercing (mosquito)
- sponging and lapping (horse fly)
- some insects combine these


evolutionary relationship between annelids and arthropods

- shared derived characters once gave strong support to hypothesis that they are closely related
- recent molecular evidence doesn't support idea
- further research is necessary to clarify evolutionary relationships of annelids and arthropods


characteristics of Merostomata

- possess chelicerae: first pair of head appendages
- horseshoe crabs, chelicerae similar to walking legs in appearance; similarity of appendages


characteristics of Arachnida

- chelicera modified in this group
- used to kill prey and pierce food source
- possess poison fangs in spiders
- pedipalps
- sexual dimorphism
- two body parts: cephalothorax and abdomen which results from fusion of head and thorax, and fusion of abdominal segments



paired head appendages used as legs, pincers or feelers; have chewing parts at base


spider webs

- silk glands make liquid, which are then emitted as liquid by spinnerets
- hardens to stronger than steel threads of same diameter
- used to catch and wrap prey, line nests, egg sacs and many other used


spider love...

- male spins small web and deposits sperm which is then sucked into modified pedipalps
- male courts female with ritualized movements and inserts pedipalp into genital opening of female
- male gets out of way fast before he is eaten


sexual dimorphism

- physical differences between male and female
- males have specialized pedipalps used for sperm transfer
- males are relatively smaller than females, sometimes much smaller


arachnid abundance

- as many as 2 million per acre
- very important the major natural control of insect pests


spiders to watch for

- black widow
- brown recluse


black widow

- has red hourglass on underside of abdomen
- have neurotoxin which attacks nervous system


brown recluse

- has violin shaped marking on dorsal surface of cephalothorax
- are necrotic which means they eat the skin



- short cephalothorax, pre abdomen and post abdomen of 5 segments which ends in stinging telson
- small chelicerae and enlarged pincer-like pedipalps
- have elaborate mating dance
- females carry young
- most aren't harmful


characteristics of Acari

- type of Arachnida
- ticks and mites
- as many as 1 million species, incredibly numerous around world
- many parasitic during one or more stages of life cycle
- some very serious agricultural pests belong to group
- complete fusion of cephalothorax and abdomen with no sign of external metamerism
- most have four pair of legs like other arachnids


deer ticks

- cause lyme disease
- small size (pinhead), orange color
- chronic and disabling with arthritis symptoms
- most ppl get bitten recover spontaneously or don't get disease
- vaccinate dog for lumes
- cause bullseye rash


what member of order acari cause serious damage to agricultural crops including fruit trees, cotton, clover and other plants?

spider mites


other mite conditions

- chiggers are mite larvae that cause dermatitis and transmit disease
- most species of mites are entirely free-living, such as dust mites


body plan of chilopoda

- centipedes have similar segments, with one pair of legs per segment, with first pair modified into maxillipeds with poison fangs
- segments flattened
- fast-moving predators


body plan of diplopoda

- head bears pair of antennae, mandibles and maxillae
- two pairs of short legs per segment, slow moving
- herbivores which prefer dark, moist places
- protect themselves by curling up and secreting toxic fluids from glands


types of Crustacea

- crabs
- lobsters
- crayfish
- krill
- copepod
- decapods
- isopods
- branacles


how ecologically important are crustaceans....

most abundant animals in world are probably copepods of genus Calanus
- present in many ecosystems


characteristics of krill

foundation of food web that includes great whales and many other marine creatures


body plan of crustacean

- are only arthropods with two pairs of antennae
- cephalothorax and segmented abdomen
- one pair of appendages per segment, but highly modified to serve different functions


digestion in crustacean

- crushing mandibles to esophagus to cardiac stomach (with gastric mill) to pyloric stomach to intestine


development in crustacean

- indirect development with true larval stage
- most primitive and widely occurring larvae among crustaceans is nauplius



- include: crabs, lobsters and crayfish
- 18,000 species
- three pairs of maxillipeds
- five pairs of walking legs
- contain major pincers (chelae)


diversity of decapods

- very diverse, range in size from few mm to 12 ft
- very important to marine ecosystem, many ppl relish them as food
- camouflage using materials from surroundings


characteristics of isopods

- pill bugs
- lack cuticle that prevents dehydration, so must live in moist locations


characteristics of barnacles

- sessile
- monoecious
- filter feeders
- attach to just about anything
- have jointed appendages


body plan of Hexapoda

- contain head, thorax and abdomen
- three pairs of legs
- some have wings


characteristics of Hexapoda

- all feeding types: herbivores, predators, parasites and detritivores
- live in all terrestrial and freshwater habitats
- important to humans
- they are dominant terrestrial animals in terms of adaptive radiation and ecological success
- 1.1 million species
- for every one human: 200,000,000 insects


insect flight

- primitive insects have direct flight muscles where each wing stroke is initiated by nervous impulse- this is called synchronous
- indirect flight muscles are caused by asynchronous nervous control where many wing strokes are initiated by one nervous impulse; makes possible vary rapid wing beats
- make a figure eight pattern in air to generate forward thrust