Arthropods Flashcards
what are the subphyla of the phylum arthropoda
1) crustacea
2) hexapoda
3) myriapoda
4) cheliceriformes
what percentage of all animals are arthropods
75%-80%
outline some characteristics of arthropods in regards to their body plan
1) bilaterally symmertric
2) each body segment has a pair of segmented, ventrally attached appendages
3) head has compound eyes
4) cuticle exoskeleton of plates
what are sclerites
plates which make up the exoskeleton made up from a cuticle
how do arthropoda differ from annelids
- no hydrostatic skeleton
- no repeating organs in each segment
- no cilia
- usually seperate sexes
what is arthropodization
organisms which are taxomically joined together by a single body plan
what are the consequences sclerotisation
aka tanning which hardens the arthropods cuticle
- protection
- allow movement
- restricts growth
- restricts respiration and excretion
outline the components of each body segment
1) large dorsal sclerite = tergite
2) large ventral sclerite = sternite
3) side regions are unsclerotised= pleura
what is the cuticle divided into in arthropods
1) epicuticle
2) procuticle
- exocuticle and endocuticle
what odes the cement and waxy layer of the cuticle allow
cement= lipoprotein protects against bacteria
waxy = prevents water loss
what are articular membranes
articulation points joining sclerites which are thin and flexible cuticle allowing movement
what are projections of sclerites called
apodemes
what are condyles
points of contact or bearing surfaces between sclerites called condyles which help to take the weight away from muscles
what hormone controlls the growth of arthropods
ecdysone
outline the process of moulting
-enzymes digest the old endo cuticle
-the epidermis secretes new, soft cuticle beneath existing exoskeleton
- old cuticle splits along predetermined lines
- takes in water and body swells enlarging new cuticle
- new cuticle hardens by sclerotisation
what are the dangers of moulting
- sometimes hard to withdraw from old cuticle
- prone to predation before new cuticle hardens
what are the two methods of excreting waste in arthropods
1) nephridia = takes waster from coelom and excrete via special glands
2) malphigian tubes= attached to the stomach and lie inside the body cavity
what is an ocelli
the simplest type of eye which is composed of a single lens and has no retina
outline the characteristics of crustacea subphylum
- 70,000 species
- 3 tagmata = head, thorax and abdomen
- 5 pairs of cephalic appendanges
what is a malostraca
a class from the subphylum crustacea with a basic body plan consisting off 5-8-6 body segments split into 3 subclasses
1) phyllocarida
2) hoplocardia
3) eumalostraca
what are the three superorders from the subclass eumalostraca
1) syncarida
2) eucarida
3) peracardia
outline the characteristics of the superorder eucarida from the subclass eumalostraca
- suspension feeders which form huge swarms
- major food source for whales, squid fish and birds
-external gills
outline the characteristics of the superorder decapoda from the subclass eumalostraca
- well developed carapace
- 3 pairs of maxilipeds used in feeding
- 5 pairs of peraeopods with one pair usually clawed
what are the 4 infraorders of the suborder reptantia from the subclass eumalostraca
1) astacidae-
2) plainura- crawfish and spiny lobsters
3) anomura- 5th leg reduced on turned inwards
4) brachyura- true crabs
outline characteristics of the subphylum myriapoda
11,500 species
- terrestrial athropods with 2 tagmata, cephalon and segmented trunk
- exoskeleton rarley has a wax layer
- gas exchange by tracheae and spiracles
what are the two minor classes from the subphylum myriapoda
1) symphala- live in soil and lead mould similar to centipeded
2) pauropoda - microscopic inhabiting leaf mould and soil similar to milipedes
what are the two main classes of the subphylum myriapoda
chilopoda = centipedes
diplopoda = millipedes
outline the characteristics of chilopoda/centipedes
- numerous segmented unfused trunk sgements each with one pair of leggs
- ## first pair modified as clawed containing venom
outline locomotion in centipedes
legs either side of the body are out of phase so as speed increases fewer legs on the ground which increase speed but gives weak forward motion
outline the characteristics of diplopoda/millipedes
trunk segments fused into pairs each baring 2 pairs of legs
lack claws or venom glands
outline locomotion in millipedes
legs positioned ventrally with body close to ground
legs in phase and majority in contact with ground producing slow but powerful forward movement
