Arthropods

Question 1

Largest living phylum

Answer 1

Arthropods

Question 2

Arhropods

Answer 2

Largest living phylum. About 75% of all described species.
+external skeleton
+Exoskeleton periodically shed to allow growth
+segmented
+metameric
+jointed apendages

Question 3

Major groups of arthropods.

Answer 3

Crustacea (crabs, shrimp barnacles)
chelicerate (spiders, scorpions, horsehow crabs.)
Hexapodas (insects)
Trilobita (trilobites)

Question 4

Fossil Record of Trilobites

Answer 4

Early Cambrian-Permian. About 75% of all cambrian species are trilobites. Carbiniferous-Permean they are pretty much all gone. Completely exctinct during the end of the Permean.

Question 5

Class Trilobita

Answer 5

Mostly benthic mobile deposit feeders or predators. Some are filter feeders, and there are a few pelagic. Calcitic exoskeleton. 3 lobe division laterally.

Question 6

Pydigium

Answer 6

Tail section (segments that fuse together)

Question 7

Thorax

Answer 7

Body section

Question 8

Cephalon

Answer 8

Head sections (segments that fuse together)

Question 9

Librigena

Answer 9

“free cheeks”

Question 10

Glabella

Answer 10

Internal organs of trilobites are found here.

Question 11

Biramous apendages

Answer 11

2 branches (ex-trilobites)

Question 12

Trilobite eyes

Answer 12

The lenses are part of the skeleton-pure calcite. Most have compound (many lensed) eyes, some are blind

Question 13

Holochroal

Answer 13

Fewer, larger separated lenses in eyes.

Question 14

Protapsid

Answer 14

Larval stage of trilobite. Composed of unarticulated exoskeleton yields

Question 15

Meraspid

Answer 15

Body with 2 or more articulated segments usually one or two articulated thoractic segments added to the body of the growing trilobite during each molt.

Question 16

Holapsid

Answer 16

Stage in trilobite growth. Number of thoracic segments reaches no further. They just grow bigger.

Question 17

Trilobite lifestyles

Answer 17

mostly epifaunal, some infaunal ,some pelagic

Question 18

Pelagic trilobites

Answer 18

Much smaller with much bigger eyes

Question 19

chelicerata

Answer 19

Includes modern arachnids (spiders, scorpions) and horseshoe crabs, extince eurypterids (sea scorpions). Nearly all are predators. Aquatic and terrestrial. Have small grasping apendages instead of antennae. Cuticle is not mineralized.

Question 20

Ziphosura

Answer 20

Horseshoe crab and extinct relatives. Benthic. Can burrow and swim. Eurytopic. Relatively rare as a fossil. “a living fossil”

Question 21

Eurytopic

Answer 21

Wide environmental tolerance (ex-horseshoe crab)

Question 22

Eurypterida

Answer 22

sea scorpion. Ordovician-permean. Diviersity peak in Silurian. Presumed to be predatory

Question 23

Arachnicds

Answer 23

Spiders, scorpions, mites, ticks. Usually refers to terrestrial chelicerates. May be polyphyletic.

Question 24

Crustacea

Answer 24

Crabs, lobsters, shrimps, pill bugs. Most common and diverse marine arthropod group. Mostly marine, some may be freshwater (Crayfish) or terrestrial (pillbugs). Tremendous diversity among body forms and life habits.

Question 25

General morphology of Arthropods

Answer 25

Chitinous cuticle (may be reinforced with calcite or other material). Body broken into regions comprised of multiple segments. Two pairs of antannae. Three pairs of limbs function as mouth parts. Wide variety of limb morphology.

Question 26

Cirripedia

Answer 26

Barnacles. Sedentary epifauna. Filter feeders and some parasites. Body protected by calcareous plates (not molted) Chitinous part of body is molted. Highly modified body plan.

Question 27

Malacostraca

Answer 27

Shrimp, lobsters, crabs. Earliest probably crustacean is a cambrain malacostracan.

Question 28

Hexapoda

Answer 28

Single branched (uniramous limb) 3/4 of all animal species on the planet. terrestrial and freshwater. 6 legged arthropods.

Question 29

Insect

Answer 29

Hexapoda with body divided into head, thorax and abdomen with 11 segments on the abdomen, 3 pairs of appendages on the thorax. Many described species. Major extinction of orders at the end of the permian and then diversity increased steadily.

Question 30

Myriapoda

Answer 30

Single unbranched limb. Centipedes. Terrestrial predator, poisonous jaw.

Question 31

Millipides

Answer 31

calcified skeleton. 2 legs/body segment.