BSc 1st Year Lower Non-chordates Phylum Ctenophora Sample Model Practice Question Answer Papers
BSc 1st Year Lower Non-chordates Phylum Ctenophora Sample Model Practice Question Answer Papers: BSc is a three-year program in most of the universities. Some of the universities also offer BSc Honours. After getting enrolled for BSc, there are certain things you require the most to get better grades/marks in BSc. Out of those, there are BSc Study Material, BSc Sample Model Practice Mock Question Answer Papers along with BSc Previous Year Papers. At gurujistudy.com you can easily get all these study material and notes for free. Here in this post, we are happy to provide you BSc 1st Year Lower Non-chordates Phylum Ctenophora Sample Model Practice Question Answer Papers.
Index for BSc 1st year Lower Non-chordates Phylum Ctenophora
General characters of Ctenophora: Page 1
Relationship with Coelenterata: Page 2
Affinities of the phylum Ctenophora: Page 3
The affinities of Hormiphora: Page 4
BSc 1st Year Lower Non-chordates Phylum Ctenophora Question Answers
Q. 1. Classify Ctenophora giving characters and examples of each group.
Give general characters of Ctenophora and classify up to classes with suitable example.
Ans.1. General Characters
1. Exclusively marine and planktonic organisms. Body transparent with biradial symmetry and oral and aboral surfaces.
2. Body-wall consists of three layers: the outer epidermis without namatocysts, the inner gastrodermis and the middle thick mesogloea with scattered cells and muscle-fibres.
3. Body with 8 vertical rows of comb plates for locomotion.
4. Digestive system consists of a mouth, a stomodaeum and a system of gastrovascular canals.
5. Special adhesive cells, the colloblasts on the tentacles help in food capture.
6. Coelom is absent.
7 There are no special organs for excretion, respiration and circulation.
8. Skeletal system is also absent.
9. Nervous system is in the form of subepidermal plexus. There is an aboral sense organ, the statocyst for equilibrium.
10. Sexes are united. i.e., male and female gonads are found in the same organism. Gonads are endodermal in origin.
11. Development includes a cydippid larva.
The phylum Ctenophora has been divided into two classes :
Class 1. Tentaculata
It includes ctenophores with tentacles. It is divided into following four orders:
Order 1. Cydippida
1. Body cylindrical or oval.
2. Tentacles 2, retactile and branched.
Examples : Hormiphora and Pleurobranchia.
Order 2. Cestida
1. Body ribbon-like.
2. Two main tentacles reduced and lie in sheaths; numerous lateral tenacles in a groove. Examples : Cestum and Velamen.
Order 3. Lobata
1. Body ovate.
2. Two large oral lobes present.
3. Two principal tentacles reduced and without sheaths.
Example : Mnemiopsis.
Order 4. Platyctenea
1. Body greatly flattened.
2. Two sheathed tentacles present.
3. Comb-plates present only in larval stage, and absent in adult.
4. Body flattened and adapted for creeping.
Examples : Ctenoplana and Coeloplana
Class2 Nuda (without tentacles)
Order 5. Beroida
1 Mouth and pharynx are wide.
2. Body conical or ovate and laterally compressed.
3. Meridional canals are highly anastomosing.
Example : Beroe.