Basal Metzoans Flashcards
(17 cards)
What are the features of basal metazoans?
Non bilateral animals
Either asymmetrical or radially symmetrical
Two layers of cells (interior and exterior)
No organs, some differentiation of tissues to perform a function
What groups fall under the basal metazoans?
Cnidaria
Ctenophora
Placozoa
Porifera
What are the porifera?
Sponges
Two layers of cells
No tissues or organs- no nervous system, no circulatory system etc
No symmetry
5500 to 9000 species
Appeared 540 mya
What are the features of respiration and feeding in porifera?
Aquiferous system
Brings water through sponge in between the cells
Water pulled in through ostia
Driven across choanoderm by beating of choanocyte flagella
Choanocytes pump large volumes of water through the body at low pressures which establishes a water current through the ostia and out through the osculum
Water flows close to cells responsible for food gathering and gas exchange
Excretory and digestive wastes and reproductive products expelled via the osculum
What are the features of reproduction in porifera?
Sexual:
-hermaphrodites- produces eggs and sperm at different times
-eggs and sperm usually produced by the choanocytes and released via the aquiferous system
-there are oviparous (egg laying species) and viviparous (release larval forms directly, larval ecology split by habitat) species
Asexual:
-reproduce by fragmentation- bits of the individual break off and are used to feed new colonies
-my also reproduce by budding- produce a colonial organism
-can produce larvae directly- not product of egg and sperm but are cells which are released
What are the features of the calcarea (a class of the porifera)?
Calcareous sponges
Found in shallow water
Rayed spicules (1,3 or 4) composed of calcium carbonate
What are the features of the hexactinellida (a class of the porifera)?
Glass sponges
Found in deep water
Spicules are six-rayed and siliceous (made of silica)
What are the features of the Demospongiae (a class of the porifera)?
Demosponges
95% of living species
Present in all depths
Spicules are siliceous
What are the 3 classes of the porifera?
calcarea
hexactinellida
demospongiae
What are the features of the placozoa?
Simplest structure of all animals
Two layers of cells
Lower surface engulfs small particles of organic detritus
Reproduce via asexual budding
What falls under the sub group coelenterates?
Cnidaria
Ctenophora
However now recognised as paraphyletic
What are the features of the ctenophora?
Comb jellies
Radial symmetry
Two layers of cells
Unique colloblast cells found on tenticles
-sticky, used in prey capture (their prey is mostly jellyfish)
-sequester stinging cells from jellyfish prey
Swing using cilia
Many are bioluminescent (glow to attract prey
100 to 150 species
What are the features of the Cnidaria?
Diverse group
Includes the corals and jellyfish
Sessile (organisms that are rooted to the spot and cannot move), sedentary (organisms that tend to remain in same position but can move if necessary) or pelagic (organisms floating free in the water column)
9000 to 11000 species
Occur at all depths
Entirely aquatic, mostly marine
Some are bioluminescent
Some are Symbiotic
-anemones, clownfish, crabs, corals, green algae
Characteristics not shared across all species:
Radially symmetrical
Diploblastic (two cell layers)
Possess cnidae
Single body cavity
No nervous system but have a nervous net/nerve cells
Alternation of generations- asexual polypoid and sexual medusoid stages
Cilliate planula larvae- small organism covered in cillia
Cnidae are found in Cnidaria, what are they?
Unique to cnidarians
Three types
-penetrant (pierces and envenoms))
-glutinant (sticks to prey)
-volvent (coils around prey)
Single use, once discharged they are metabolised by the animal and replaced
Primarily used in feeding, secondary use in defence
Alternation of generations is found in Cnidaria, what is this?
Polypoid phase
-found in all classes
-sessile phase
-can reproduce asexually but can also bud off medusi (little jellyfish stacked on each other, which flip up and form the medusoid phase)
Medusoid phase
-medusozoa only
-free swimming
-reproduce sexually, usually by dioecious (have both male and female)
What are the two sub phylum of the Cnidaria?
Medusozoa
Anthozoa
What are the classes of the sub phylum anthozoa, which is a sub phylum of cnidaria
Alcyonaria- sea pens, sea fans, soft corals
Zoantharia- sea anemones, hard corals
