Lecture 27 Flashcards
What are the characteristics of the phylum Mollusca?
-more than 100 000 species -mostly marine, some freshwater and damp terrestrial -bilateral symmetry -triploblastic -coelomate -protostome -not segmented (except Neopilina) -up to 8 classes (neopilina= at least 200 m under water, the foot is segmented, suggests that molluscs used to be segmented
What is the body structure of the Mollusca like?
-variations on the same basics -mantle= dorsal body wall which often forms shell -mantle cavity= space between mantle and main body where gills or lungs are found -muscular foot= used for moving, feeding and manipulation -head with specialised mouthparts= radula -radula= almost like a tongue herbivore= like sand paper scrape the plant predator= tears the pray
What are the characteristics of the Mollusca class Polyplacophora?
-chitons, (coat of mail shells) -exclusively marine -bilaterally symmetrical -shell consists of 8 large plates surrounded by a girdle of smaller spicules -mostly feed on algae or encrusting organisms bit some are predators -reproduce sexually, some brood their young in their mantle -overlapping shell plates predatory ones= they are sit and wait predator just slap and eat it -some protect the young in their mantle -gonopore= where eggs and sperm come through -nephridicopore= waste hole, in some also reporductive
What are the characteristics of the Mollusca class Bivalva?
-clams, mussels. oysters -marine and freshwater -characterised bytwo shells; no distinct head -lost radula; filter feed (sometimes through foot) -often live buried in the sand -gills function for gas exchange and food collection -reproduction is usually sexual and external -trocophore larvae typical -releasing sperm and eggs out -free swimming larvae -can filter some viruses etc from water -abductor muscles= holed the shells closed
What are the characteristics of the Mollusca class Gastropoda?
-slugs and snails -marine (eg whelks and sea slugs), freshwater and terrestrial -spiral shell (lost in slugs) -produce slime= aids movements -well-developed head with eyes and tentacles -larvae= bilaterally symmetrical -adult snails= body twisted= torsion (180 degrees)
What is torsion in snails?
-as snails develop their body twists (torsion) -result= 180 degree turn in body inside shell -advantage= mantle cavity anterior (allows withdrawal into shell) -disadvantage -anus empties mouth
What is different in slugs?
-lost shell -mantle is massively reduced -mantle cavity disappeared -detorsion= body twisting is lost -may allow slugs to forage in soil or sandy substrate –very different lifestyle so adapted, in soil, the cavity could have sand etc in (the marine one)
What are the characteristics of the Mollusca class Cephalopoda?
caphalopoda= head-foot -squid, octopus, cuttlefish, Nautilus -marine, free-swimming -shell reduced to internal support(except Nautilus) -mantle used for propulsion -foot converted into tentacles -cephalopods= one of the most intelligent among the invertebrates, use tools -excellent vision -pigment cells= chromatophores -visual signals= mate attraction, camouflage -similar eyes to vertebrates use visual signals in communication as well, male pretending to be female so it avoid fights and then tries to sneak in to sex can use coconut shell as protection= one of the first examples of non-vertebrate using “tools”
What is special about Nautilus?
-has a shell=buoyancy aid -as Nautilus grows larger need greater buoyancy -shell grows and nautilus seals off gas filled chambers -as it grows larger= shell heavier so grows chambers so maintains the buoyancy
What are the characteristics of the phylum Echinodermata?
-entirely marine -5 main classes -sea stars (Asteroidea) -brittle stars (Ophiuridea) -sea urchins (Echinoidea) -sea lilies (crinoidea) -sea cucumbers (holothuroidea) -pentaradial symmetry as adults and bilateral symmeztry as larvae(indicate bilaterally symmetrical ancestry) -triplobastic -coelomate -DEUTEROSOME -no segmentation -spiny epidermis -have a water vascular system in the coelom (madreporite is teh opening of the water vascular system) -water system= different to nervous system moves in at the top and comes out in the feet tube feet connected to water vasular system can move independently aid in movement, just water pulling through= movement
What are the ways the Echinodermata defend themselves?
-pedicellariae (some Asteroidea species=sea stars) =modifies spines with claws and capable of movement =used to remove encrusting organisms -ejection of intestines (some Holothurians=sea cucumbers) =when startles some will expel sticky tubules to entangle predators =may also discharge a deadly toxin -can move but not very fast need extra protection from predators
What is the variation on Echinodermata body plans?
What are the characteristics of the phylum Chordata?
-marine, freshwater, terrestrial, aerial, subterranean -bilateral symmetry -triploblastic -coelomate -deuterostome -partial segmentation -reproduction- largely sexual and internal
What are the subphyla of the phylum Chordata?
-big diversity in sub-phyla -encrusting marine sea squirts -marine acorn worms -fish like lanceletes -amphibians, reptiles, fish, birds, mammals
What is the notochord?
-defining feature of the chordates -stiff rod of mesoderm found next to the nerve chord in all chordate embryos (and some adults) -functions as an endoskeleton (like a backbone) -nerve chord- located dorsally -notochord that’s why they’re close to us genetically eat their brain as adults and lose notochord as well even humans= partly segmented
How do you get from notochord to vertebrae?
subphylum Vertebrata -notochord- present in the embryo but vertebrae (the spine)grow around the notochord and replace it -vertebrae-surround and protect the nerve chord(spinal chord) -around 8 weeks get cartilage and bone growing and then notochord replaced by bone
