Flashcards in Lecture 2 Deck (20):
What is the difference between the eumetazoa and the parazoa?
The eumetazoa have true tissues?
What is the definition of a true tissue?
A groups of cells that have a common structure and function and are integrated (act in coordination)
Why do sponges (porifera) lack true tissues?
Things like the choanoderm have a common structure and function but lack the intergration required of true tissues
What are the defining common features of the radiata?
Symmetry is radial or biradial and they are diploblastic
What is the difference between radial and biradial symmetry?
Radial symmetry is where any slice through the middle would divide the organism into equal halves while biradial symmetry there is at least one set of paired structures so there are only two planes of symmetry
What does diploblastic mean?
The organism develops from two embryonic tissue layers the outer ectoderm and inner endoderm which are separated by a non cellular mesoglea layer
What are the two phyla in radiata?
Cnidaria and Ctenphora
What types of organisms belong to the Cnidaria phyla?
Hydras, Jellyfish, Anemones and Corals
What are the evolutionary features of the Cnidaria?
They are ancient having developed from spinges approximately 700 million years ago and they are diverse with over 100,000 living species
What are the ecological features of cnidaria?
They are mostly marine with most preferring shallow tropical water (though a few fresh water species exist)
All are carnivorous
May be free living of colonial
Sessile, floating or moving which can alternate during different stages in live cycles
The corals are ecologically important due to their secreted hard exoskeletons
What is the basic body shape of cnidaria?
The main part of the body is a body stalk
There is a hollow which contains the gastrovascular cavity
A single opening to serve as the mouth and anus which is surrounded by the hypostome which has a whorl of tentacles attached to it
What are the cells and the function of the epidermis?
This is the outer layer which contacts the environment, and is a true epithelium with cells tightly packed and anchored to a basement membrane allowing for regulation of what can pass through the body wall
It contains epitheliomuscular cells which are contractile and serve as a protective layer, Nerve cells which from contractile bundles and neurosecretory cells, Sensory cells, Gland cells, Cnidocytes and interstitial cells
What are the cells and functions of the gastrodermis?
This is the inner layer of epithelium containing nutritive muscle cells which have cilia to regulate water flow, Gland cells which secrete enzymes for digestion and mucus for lubrication, sometimes nerve cells are present interstitial cells
What are the functions and contents of the mesoglea?
This is a acellular, gelatinous layer between the epidermis and gastrodermis
In some Cnideria cells from the other body lares migrate into the mesoglea
Provides skeletal support and buoyancy
What is the variation in body forms seen in cnidaria?
The polyp form typically seen when the organism is sessile
The medusa form which resembles an inverted polyp and is mobile, swimming through contraction of the bell and with a thick mesoglea for buoyancy
What are the classes of cnidaria?
Hydrozoa, Scyphozoa, cubozoa, anthozoa
What are the features of the hydrazoa (hydras) class of cnidaria?
They are mostly marine, and colonial and have a life cycle which alternates between the polyp which is the most conspicuous phase and reproduces by asexual budding and the medusa which reproduces sexually
What are the features of the scyphozoa (jellyfish) class of cnidaria?
These are all marine with the medusa being the main lifecycle
Coastal species often have a brief sessile polyp stage but open ocean species generally lackthis phase entirely
What are the features of the cubozoa (box jellyfish) class of cnidaria?
Have a box shaped medusa phase with complex eyes around the medusa fringe
Group contains the sea wasp which is one of the deadliest organisms causing excruciating pain and often death