Phylum Arthropoda

Front 1

Phylum Arthropoda

Back 1

"jointed-foot" animals; trilobites, crustaceans, chelicerates, myriapods, insects; largest phylum of animals; found in all major environments

Front 2

Characteristics shared with other phyla not unique to arthropods

Back 2

bilateral symmetry, coelomates, triploblastic, prostomate

Front 3

Clade Panarthropoda

Back 3

phylum arthropoda, phylum onychophora, phylum tardigrada

Front 4

Phylum Onychophora

Back 4

"velvet worms", not an arthropod, possible closest living relatives of arthropods; terrestrial, mostly tropical species (live in leaf litter);numerous paired, unjointed legs that end in claws on each segment; soft outer cuticle that is molted (ecdysozoan); metameric, nephridia, open circulatory system with blood bathing organs within a hemocoel (true coelom is reduced); anterior brain; respiratory trachael system of tubes leading to surface pores for air; dioecious

Front 5

Phylum Tardigrada

Back 5

"water bears"; don't have a lot of information on them because they're so tiny and hard to study; maybe have a true coelom, but it's reduced; have primarily a hemocoel; if coelomate, enterocoelic; molecular evidence suggests affinity to arthropods; all habitats but mostly live in lichens and mosses; eutely; outer cuticle is molted; dioecious (lay eggs); 4 pairs of unjointed legs ending in claws; nervous sytem (brain, ventral nerve cord, metameric ganglia); have an excretory system and complete digestive system; complex pharynx to pierce & suck small prey & plants; no respiratory organs

Front 6

cryptobiosis

Back 6

"hidden life"; a state in which the sign's of life of an organism have weakened to the point where they are barely measurable or no longer measurable; tardigrades are capable of surviving extremes this way

Front 7

tun

Back 7

a cyst-like capsule that tardigrades exhibit during cryptobiosis; when dessicated, animal shrivels into a "tun" until water returns

Front 8

traditional (non-molecular) view of arthropod descent

Back 8

arthropods evolved from polychaete-like (metameric) annelid ancestor that developed appendages on every segment, followed by segments fusing together for specialized functions (tagmosis)

Front 9

tagmosis

Back 9

fusion of segments/metameres into distinct body regions; defines the different arthropod classes;

Front 10

Unique shared characteristics linking polychaetes & arthropods

Back 10

1. metameric segmentation & how segments develop (posterior budding zone)
2. paired appendages on segments
3. double ventral nerve cord with metameric ganglia
4. a cuticle secreted by hypodermis tissue

Front 11

"Arthropodization"

Back 11

hard outer exoskeleton; jointed appendages moved by antagonistic muscle pairs; major body cavity is a hemocoel (persistent blastocoel, true coelom is reduced); tagmosis; open circulatory system

Front 12

Coelom formation

Back 12

locomotion becomes associated with the exoskeleton and its attached muscles and the coelom becomes greatly reduced

Front 13

open circulatory system in arthropods

Back 13

blood empties from the vessels into sinuses to bathe organs and tissues and returns directly from the hemocoel to the pumping heart through ostia

Front 14

General characteristics of arthropods

Back 14

bilateral, metameric, tagmosis; paired, jointed appendages(one pair per segment); exoskeleton; most exhibit metamorphosis; reduced "true" coelom & persistent blastocoel (hemocoel); complete digestive system (mouth, anus); open circulatory system; paired excretory organs; mostly dioecious; nervous system with ventral double nerve chain of ganglia; respiration by various specialized structures

Front 15

exoskeleton

Back 15

hard, chitinous cuticle secreted by epidermal cells that periodically molts; provides skeletal support (allowing reduction of hydrostatic coelom) & sites for muscle attachment; covers all epidermal surfaces except inner gut lining; cuticle has three layers formed of chitin (a polysaccharide), wax, tanned proteins, and minerals

Front 16

metamorphosis

Back 16

a series of distinct post-embryonic changes in body form (larva to adult)

Front 17

three layers of cuticle

Back 17

epicuticle, exocuticle, endocuticle; exocuticle & endocuticle make up the procuticle

Front 18

Challenges imposed by exoskeletal cuticle

Back 18

restricts growth, movement, gas exchange, exchange of solutes & water, sensation

Front 19

Solution to exoskeletal restriction of growth

Back 19

Molting or ecdysis

Front 20

Ecdysis

Back 20

molting; allows an animal to grow by replacing the old cuticle with a larger one; a new soft cuticle is deposited below the old one, the arthropod inflates with water or air, the old cuticle splits and is cast off in one piece, another inflation of the body expands the new cuticle before it hardens; only the epi- & exocuticle are shed, old endocuticle gets dissolved; controlled by hormones (molt-inhibiting/molt-promoting hormones)

Front 21

Solution to exoskeletal restriction of movement

Back 21

jointed exoskeleton & arthrodial membranes (movement only occurs at the joints which move in one plane only)

Front 22

arthrodial membranes

Back 22

thin, flexible membranes at joints

Front 23

apodemes

Back 23

broad (high surface area) sites for muscle attachment

Front 24

solution to exoskeletal restriction of gas exchange

Back 24

gills, book lungs, & tracheal systems

Front 25

trachea

Back 25

air tubes

Front 26

tracheal system of insect

Back 26

a system of air tubes extending from surface spiracles (openings) that carry air to inner tissues

Front 27

solution to exoskeletal restriction of exchange of nitrogenous solutes and water with environment

Back 27

excretory malpighian tubules, coxal glands, maxillary glands or antennal glands

Front 28

solution of exoskeletal restriction of sensation

Back 28

elaborate sensory receptors; "insensitivity" is overcome by either thinning the cuticle (allowing photo and acoustic reception) or using sensory bristles; most bristles are sensitive of bending (mechanoreceptors), some act as chemoreceptors

Front 29

tagmata

Back 29

functional groups formed when metameres are combined; a head tagma, thoracic tagma, and abdominal tagma; appendages also become specialized for walking, eating, swimming, breathing

Front 30

Remipedia

Back 30

a "primitive" crustacean class with little tagmosis

Front 31

serial homology

Back 31

repetitive ("serial") structures on the same organism; as evolution proceeds undifferentiated serial appendages may become specialized for various tasks

Front 32

uniramous

Back 32

1 terminal branch; in these types of limbs the 2nd exopod branch is "lost" (ex: walking legs of insects)

Front 33

endopod

Back 33

the internal or principal branch of locomotive appendages of crustacea

Front 34

exopod

Back 34

the external branch of the appendages of crustacea

Front 35

biramous

Back 35

2 branches

Front 36

phyllopodous

Back 36

flattened limbs (can be used for swimming)

Front 37

stenopodous

Back 37

tubular limbs (can be used for walking)

Front 38

Classification of Arthropoda

Back 38

Subphylum Trilobita
Subphylum Chelicerata
Subphylum Crustacea
Subphylum Myriapoda
Subphylum Hexapoda