Topic 15-16

Question 1

What are protostomes?

Answer 1

monophyletic with two major lineages

fossils indicate lineages originated in the ocean, protostomes made the transition from water to land multiple times as they diversified

challenges: avoid drying out, gas exchange, hold up bodies

Question 2

What is ecdysis?

Answer 2

process of molting the cuticle in order to grow

entire cuticle shed at once

cuticle = non-living outer layer of skin

Question 3

What is the cuticle?

Answer 3

below cuticle is epidermis: living cells that secrete substances –> cuticle

very fine ducts run from epidermis to top of cuticle

Question 4

What is morphological diversity?

Answer 4

multicellular animals have a common tool kit of genes that establish the animal body plan during development

expressing the genes in the tool kit at different times and places during development can lead to dramatic differences

diversification of animal body plans can occur by the generation of new genes over time

however, changing the expression pattern of existing genes likely had an even larger impact on animal body plan diversification

Question 5

What is the phylum arthropoda?

Answer 5

earliest fossil: Cambrian explosion (~500 MYA)

most species-rich phylum of any organism

most ecologically important group of animals

Question 6

What are the five main groups of arthropods?

Answer 6

Trilobita

Chelicerata

Myriapoda

Crustacea

Hexapoda

Question 7

What are the characteristics of arthropods?

Answer 7

cephalization: nervous tissue becomes concentrated toward head during course of evolution, head region composed of several segments specialized for feeding and sensing

open circulatory system

jointed appendages: specialized functions

segmented body: changes to regulation of Hox genes

sclerotized cuticle made of chitin: acts as an exoskeleton, must moult to grow, provides support and a rigid surface for muscles attachment

Question 8

What is tagmatization?

Answer 8

segmented body and jointed appendages arranged into functional units with specialized functions (diversification of labor)

increase in arthropod diversity

Question 9

What is the subphylum chelicerata?

Answer 9

lack antennae

chelicerae as main mouthparts

cephalothorax: wholly or partially covered by carapace, 6 pairs of limbs, eyes, if present, are located here
abdomen: may or may not bear appendages, contains guts and reproductive organs

Question 10

What is the class arachnida?

Answer 10

spiders, mites, scorpions, etc.

ocelli: simple eyes

fluid-feeding predators

seperate sexes

Question 11

What are the characteristics of class arachnida, order araneae?

Answer 11

tight constriction between cephalothorax and abdomen

2 segmented chelicerae

tracheae and/or book lungs

spinnerets: abdominal appendages, spinning silk

Question 12

What are the characteristics of class arachnida, order acari?

Answer 12

no separation between cephalothorax and abdomen (no external evidence of segmentation), more like a ball with legs

diverse ecology: predators, detritivores, herbivores, parasites

Question 13

What are acari (mites)?

Answer 13

most economically important arachnids

crop pests, eg. spider mites

bio-control agents

medically important

Question 14

What is the subphylum myriapoda?

Answer 14

reduced tagmata

head with ocelli, mandibles, 1 pair antennae

Question 15

What is the class diplopoda?

Answer 15

detritivorous or herbivorous

two pairs of legs per segment

defensive coil and secretions

Question 16

What is the class chilopoda?

Answer 16

most are carnivorous

1 pair of legs per segment

flattened body

1 pair of modified legs behind mouthparts (poison claws)

Question 17

What is the subphylum crustacea?

Answer 17

crabs, lobsters, shrimp and their relatives

mostly marine, but many freshwater and some terrestrial species

separate sexes (except barnacles)

huge size range

highly variable morphology

Question 18

What is the crustacean morphology?

Answer 18

basic crustacean body plan, 2 pairs of antennae, compound eyes (often on stalks)

head and thorax usually merged as cephalothorax

cephalothorax usually covered by a carapace (shield that covers dorsal and lateral sides, carapace sometimes also covers abdomen)

Question 19

What are hexapods and myriapods?

Answer 19

hexapods: insects, springtails, and a few others
myriapods: centipedes, millipedes and a few others

shared features: only one antennae, mandibles for main mouthparts, tracheae (respiratory tubes) for gas exchange

Question 20

What is the class insecta?

Answer 20

cerci (singular, cerus): pair of segmented terminal appendages

compound eyes

many have ocelli (singular = ocellus)
“simple eye”
collect and focus light through a single lens

Question 21

What is incomplete metamorphosis?

Answer 21

juveniles (nymphs) may share morphology and habitat of adult

wings develop slowly over several moults

Question 22

What is complete metamorphosis?

Answer 22

wings develop all at once in a special stage called a pupa

juvenile always has different morphology and ecology than adult

juvenile properly termed “larva”

Question 23

What is moulting?

Answer 23

shedding all ectodermally-derived cuticle (including the linings of foregut, hindgut and traceae)

new cuticle is produced before moult is soft and wrinkled

after moult, animal swallows air or water to expand new skin