Invertebrates Flashcards
Sponge Structure
asymmetric, no fixed shape. skeleton of fibers called spicules. no tissues or organs. groups of cells not surrounded by membranes. cells relatively unspecialized. cell differentiation is fully and easily reversible
Sponge Feeding
suspension feeders. water drawn through body pores. algal symbionts to provide fixed carbon (common among invertebrates)
Sponge Defense and attack
toxins, bright warning colouration, spicules. some sponge toxins work against other sponges for space competition. self-nonself recognition, memory
Sponge reproduction
asexual-fragmentation, budding
sexual-sequential hermaphrodites, prevents self fertilization
Cnidarian body forms
polyp-attached to substrate
medusa-bell-shaped, free-floating
Cnidarian structure
nerve net, chemical and mechnical sensors, some have eyes
contractile cells provide motility but no true muscle, originates in epiderm, gastrodermis extends into mesoglea (some species have contractile cells originating in mesoglea)
Cnidarian feeding
predatory and algal symbionic life style
nematocyst-injects painful, paralytic toxin
Cnidarian reproduction
asexual-budding
sexual-larva is small ciliated planula
Flatworms
triploblastic, protostomate, acoelomatous, flattened body for gas exchange
Planarians
mainly carnivores
mouth leads to gastrovascular cavity
cephalization/rudimentary brain, eye spots for orientation (negatively phototatic)
asexual reproduction by transverse fission and regeneration
sexual-hermaphroditic individuals, gonopore receives semen, echange is reciprocal. penis fencing
Tapeworms
endoparasitic, nutrients pass directly across body wall of worm. conver food to eggs and sperm (10 000-100 000 fertilized eggs/day)
Metameric segmentation
Serial repetition of segments
Tagmatization
modification and specialization of segments
Annelids
segmented worms
oligochaetes-metameric segmentation and polychaetes-differentiated segments
Oligochaetes
earthworms and some freshwater and marine relatives
Oligochaetes locomotion
alternating contraction of circular and longitudinal muscles, working against the coelomic fluid isolated in each segment
Oligochaetes circulation
closed, oxygen absorbed across the skin, highly vascularized for this function, carried by hemoglobin and oxygen-binding proteins, pseuohearts, contractile vessel walls
Oligochaetes feeding
deposit feeder, ingest soil, extract nutrients and leave behind castings
Oligochaetes reproduction
sexual (simultaneous hermaphroditism)
asexual (fragmentation, parthenogenesis)
parthenogenesis
embryo development without fertilization
Mollusc body structure
coelomatous, unsegmented
Generalized mollusc
muscular foot-locomotion attachment burrowing
visceral mass-internal organs, gill and anus open to mantle cavity.
mantle-secretes the shell, calcium carbonate in a protein matrix.
radula-toothed scraping tool
Mollusc circulation
closed in cephalopods, open in others
Chitons (polyplacophorans)
grazyers in intertidal region, oval bodies, 8 dorsal plate
Gastropods
snails, slugs, 60 000-75 000 species consituting 80% of all molluscs. Dr Louise Page. only molluscs on land. Mantle cavity modified to a lung.
grazers, predators. torsion
Torsion
180 degree twisting of visceral mass, assymetric growth and muscle contraction on one side of embryo. mass redistribution?
Bivalves
clams, scallops, mussels. dorsal hinge, shells left-right. adductor muscles hold shells together. gills collect o2 and food particles, trapped in mucus. usually sedentary, burrowing.
scallops more active
cephalopods
octopi, squids, nautiluses. eject water through siphon to produce rapid directed movements, allows vertical movement, 3D. Predators with complicated brains and sense organs. most intelligent invertebrates
Nematode
commonly called roundworm, unsegmented and pseudocoelomatous with complete digestive tract, cryptospecies
Nematode lifestyle
free-living, parasitic.
Trichniella spiralis
causes trichinosis, from undercooked pork and game meat
Guinea worm
recently almost eradicated
Diversity of nematode
25 000 known, 500 000 undescribed
Cryptosepcies
look similar, diff in genital anatomy and game recognition factors
Interesting facts on nematodes
about 80% individual animals are nematodes. 1 000 000 in 1cubic m of soil.
chromosome diminution-fragment and lose embryonic cell dna 20% genome remains in differentiated cells
cyrptobiosis-suspended animation, stopped metabolic processes
anhydrobiosis-extreme dessication tolerance, trehalose replaces water
Caenorhabditis elegans
best understood animal, model organism for developmental genetics. 959 somatic cells, completel cell lineage known “theworm”
Arthropods
most successful of all animal phyla in terms of diveristy (2/3 animal species are arthropods)
Arthropod clades
chelicerates
myriapoda
hexapoda
crustacea
Chelicerates
spiders, mites, ticks, scorpions, cephalothorax, cherlicerae (fangs), no sensory antennae, simple eyes iwth 1 lens
Myriapoda
centipedes, millipedes. mandibles, pair of sensory antennae, uniramous appendages, compound eyes
Hexapoda
insects, uniramous appendages, 3 pairs of legs on thorax, 1 pair of sensory antennae, flight, metamorphosis
Crustacea
crabs, lobsters, barnacles, 2 pairs sensory antennae, mandibles, biramous appendages
General arthropod features
segmentation, jointed appendages, exoskeleton- chitin and protein, extensive cephalization, receptors for sight taste smell touch
