Flashcards in Lecture 3 Deck (23):
What are the ecological features of the ctenophora?
They are all marine with some being deep water
Most are free swimming but a few are sessile
What are the evolutionary features of the ctenophora?
There is low diversity with only about 100 living species and also suggestions they might be most basal known lineage of animals
What do the ctenophora have in common with the cnidaria?
They both have tissue level of organisation are diploblastic and contain biradial symmetry
What are the differences between the ctenophora and cnidaria?
Ctenophora have a separate mouth and anus and swim through the use of comb rows which consist of comb plates allowing forward or reverse movement as opposed to cnidaria which swim through contraction of the bell
They have different methods of prey capture as while cnidaria use cnidocytes, ctenophora use colloblasts which secrete sticky adhesive granules to trap prey
What are the key features of the bilateria?
Organ-level of organisation
What does cephalisation mean?
There is a clustering of sense organs in the head which form a cerebral ganglion and directional conduction in longitudinal nerve cords
What does the third germ layer in bilateria allow for?
Specialisation of tissues with ectoderm providing protection the endoderm providing nutrition and mesoderm which contains dedicated organs and muscles
What are the two key groups in the bilateria?
Protosomia and deuterostomia
What are the two key groups in the protosomia?
Lophotrochozoa and Ecdysozoa
What are the key features of the lophotrochozoa?
There are no particular features that define the group instead it is an evolutionary related group with diverse characteristics (the groups were not believed to be related until more recent molecular techniques were used)
What are the evolutionary features of the platyhelminthes?
A diverse group of 20,000 species which may have evolved directly from cnidaria type ancestors potentially making them very old bilaterians this is suggested by their structural simplicity
Analysis of DNA sequences suggests that they are more related to complex phyla and have infact become more simple from a complex ancestor
What are the ecological features of the platyhelminthes?
They are diverse with species existing in marine, freshwater and damp terrestrial environments
They may be free living or parasitic with many having complex life cycles which have both free living and parasitic stages
What is the body form of Platyhelminthes?
They are flat and elongate have bilateral symmetry, triploblastic and are acoelomate
What are the functional systems of Platyhelminthes?
Unlike radiata flatworms have some specialized organ systems including a nervous system
A digestive system, excretion system and a reproduction system
What are the features of a nervous system in a platyhelminthe?
eyespots, lateral flaps a brain in an encephalised head as well as ventral nerve cords joined by transverse connecting nerves
What are the features of a digestive system in a platyhelminthe?
digestive system which is blind ending and contains a mouth and muscular pharynx midway down the body (so the body is freed for prey capture)
What are the features of a excretion system in a platyhelminthe?
excretion system involves nitrogenous waste diffuse directly out of the body as well as protonephria which are branching internal tubules used to excrete excess water where cilia on flame bulb flame cells move the water into a tubule where it is excreted via the nephridopore
What are the features of the reproductive system in a platyhelminthe?
It is both sexual requiring complex male and female sexual organs and asexual reproduction where the organism constricts in the middle to form two individuals
What are the four classes of Platyhelminthes?
Turbellaria, Trematoda, Monogeneans and cestodea
What are the features of the turbellaria class of Platyhelminthes?
Nearly all are free living, most are marine (though planaria live in freshwater), most are predators
What are the features of the trematoda class of Platyhelminthes?
Almost all have an adult form which is an endoparasites of vertebrates, they feed by grazing on host cells, cellular debris and bodily fluids
What are the features of the monogeans class of Platyhelminthes?
Structure and function is similar to that of trematodes and turbellarians
Most are ectoparasites living on the surface of gills, though a few live in the bladders of frogs and turtles and one lives in hippo eyes