Topic 15-16 Flashcards
What are protostomes?
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
What is ecdysis?
process of molting the cuticle in order to grow
entire cuticle shed at once
cuticle = non-living outer layer of skin
What is the cuticle?
below cuticle is epidermis: living cells that secrete substances –> cuticle
very fine ducts run from epidermis to top of cuticle
What is morphological diversity?
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
What is the phylum arthropoda?
earliest fossil: Cambrian explosion (~500 MYA)
most species-rich phylum of any organism
most ecologically important group of animals
What are the five main groups of arthropods?
Trilobita
Chelicerata
Myriapoda
Crustacea
Hexapoda
What are the characteristics of arthropods?
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
What is tagmatization?
segmented body and jointed appendages arranged into functional units with specialized functions (diversification of labor)
increase in arthropod diversity
What is the subphylum chelicerata?
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
What is the class arachnida?
spiders, mites, scorpions, etc.
ocelli: simple eyes
fluid-feeding predators
seperate sexes
What are the characteristics of class arachnida, order araneae?
tight constriction between cephalothorax and abdomen
2 segmented chelicerae
tracheae and/or book lungs
spinnerets: abdominal appendages, spinning silk
What are the characteristics of class arachnida, order acari?
no separation between cephalothorax and abdomen (no external evidence of segmentation), more like a ball with legs
diverse ecology: predators, detritivores, herbivores, parasites
What are acari (mites)?
most economically important arachnids
crop pests, eg. spider mites
bio-control agents
medically important
What is the subphylum myriapoda?
reduced tagmata
head with ocelli, mandibles, 1 pair antennae
What is the class diplopoda?
detritivorous or herbivorous
two pairs of legs per segment
defensive coil and secretions
What is the class chilopoda?
most are carnivorous
1 pair of legs per segment
flattened body
1 pair of modified legs behind mouthparts (poison claws)
What is the subphylum crustacea?
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
What is the crustacean morphology?
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)
What are hexapods and myriapods?
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
What is the class insecta?
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
What is incomplete metamorphosis?
juveniles (nymphs) may share morphology and habitat of adult
wings develop slowly over several moults
What is complete metamorphosis?
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”
What is moulting?
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
