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Ctenophores are free-swimming, transparent, 
jelly-like, soft-bodied, marine animals having 
biradial symmetry, comb-like ciliary plates for 
locomotion, the lasso cells but nematocytes are 
wanting. They are also known as sea walnuts or 
comb jellies
Page 4


Ctenophores are free-swimming, transparent, 
jelly-like, soft-bodied, marine animals having 
biradial symmetry, comb-like ciliary plates for 
locomotion, the lasso cells but nematocytes are 
wanting. They are also known as sea walnuts or 
comb jellies
Phylum Ctenophora Characteristics
• They are free-swimming, marine, solitary, pelagic 
animals. No polymorphism and no attached stages 
were found.
• The body is transparent, gelatinous, pear-shaped, 
cylindrical, or flat or ribbon-shaped.
• They have a biradially symmetrical body along an oral-
aboral axis.
• They have an external surface with comb-like 8 ciliary 
plates for locomotion. Hence name as comb jellies
Page 5


Ctenophores are free-swimming, transparent, 
jelly-like, soft-bodied, marine animals having 
biradial symmetry, comb-like ciliary plates for 
locomotion, the lasso cells but nematocytes are 
wanting. They are also known as sea walnuts or 
comb jellies
Phylum Ctenophora Characteristics
• They are free-swimming, marine, solitary, pelagic 
animals. No polymorphism and no attached stages 
were found.
• The body is transparent, gelatinous, pear-shaped, 
cylindrical, or flat or ribbon-shaped.
• They have a biradially symmetrical body along an oral-
aboral axis.
• They have an external surface with comb-like 8 ciliary 
plates for locomotion. Hence name as comb jellies
• They have a pair of long, solid, retractile 
tentacles.
• Their body organization is cell- tissue grade.
• Their body is acoelomate and triploblastic, with 
the outer epidermis, inner gastrodermis, middle 
jelly-like mesoglea with scattered cells, and 
muscle fibers.
• Their digestive system contains the mouth, 
stomodaeum, complex gastrovascular canals, 
and 2 aboral anal pores.
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FAQs on PPT: Phylum Ctenophora - Zoology Optional Notes for UPSC

1. What are the defining characteristics of Phylum Ctenophora?
Ans. Phylum Ctenophora, commonly known as comb jellies, is characterized by their gelatinous bodies, radial symmetry, and the presence of specialized structures called ctenes or combs, which are rows of tiny, hair-like structures used for locomotion. They also possess two main cell layers (diploblastic) and exhibit a unique mode of reproduction that can include both sexual and asexual methods.
2. How do organisms in the Ctenophora phylum reproduce?
Ans. Ctenophores primarily reproduce sexually, releasing eggs and sperm into the water where fertilization occurs. Some species are hermaphroditic, meaning they possess both male and female reproductive organs. Additionally, Ctenophores can reproduce asexually through a process called fission, where the organism splits into two or more parts, each developing into a new individual.
3. What is the ecological role of Ctenophores in marine environments?
Ans. Ctenophores play a significant role in marine ecosystems as both predators and prey. They primarily feed on small zooplankton and fish larvae, thus helping to regulate these populations. In turn, they are also a food source for larger marine animals, contributing to the food web dynamics in their habitats.
4. How do Ctenophores differ from other marine invertebrates?
Ans. Ctenophores differ from other marine invertebrates, such as cnidarians (jellyfish and corals), in their body structure and locomotion. Unlike cnidarians, Ctenophores lack stinging cells (nematocysts) and instead use cilia for movement. Additionally, their body composition is more gelatinous, and they have a unique method of capturing prey using sticky cells called colloblasts.
5. What are some examples of species within Phylum Ctenophora?
Ans. Some notable species within Phylum Ctenophora include Pleurobrachia pileus, commonly known as the sea gooseberry, and Mnemiopsis leidyi, also known as the warty comb jelly. These species are often studied for their ecological impact and unique biological features, such as bioluminescence in some cases.
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