class 9 characteristics of nematoda, artropoda,mollusca,echinodermata and protochordata
Nematoda is a phylum under Kingdom Animalia.
These are a group
of invertebrates without vertebrate column.
General characteristics of Nemtoda
Nematoda are bilaterally symmetrical, triploblastic parasitic worms with a cylindrical body.
Nematoda get their name from two Greek words - “nema,” which means “thread,” and “ode,” which means “like”. Nematodes can be free living or parasitic. e.g. Ascaris.
Nematodes are unsegmented round worms which are considered to be pseudocoelomate organisms.
Nematodes possess complete alimentary canal.
Sexes are separate in nematodes and they exhibit sexual dimorphism. Eggs are protected by thick walls to overcome unfavourable conditions.
e.g. Ascaris, Ancyclostoma, Dracunculus etc.
General characteristics of Nemtoda
Nematoda are bilaterally symmetrical, triploblastic parasitic worms with a cylindrical body.
Nematoda get their name from two Greek words - “nema,” which means “thread,” and “ode,” which means “like”. Nematodes can be free living or parasitic. e.g. Ascaris.
Nematodes are unsegmented round worms which are considered to be pseudocoelomate organisms.
Nematodes possess complete alimentary canal.
Sexes are separate in nematodes and they exhibit sexual dimorphism. Eggs are protected by thick walls to overcome unfavourable conditions.
e.g. Ascaris, Ancyclostoma, Dracunculus etc.
Phylum Arthropoda - Characteristics
·
EXOSKELETON In most
arthropods the body is covered with chitonous. ...
·
METAMERISM. ...
·
JOINTED APPENDAGES.
...
·
DOUBLE VENTRAL NERVE
CORD Ventral nerve cord with. ...
·
OPEN CIRCULATORY SYSTEM
A dorsal (upper) vessel directs blood. ...
·
BILATERAL SYMMETRY.
MOLLUSCA
Unsegmented soft body with bilateral symmetry.
Presence of an internal or
external shell.
A toothed tongue (made mostly of
chitin) called the radula.
A mantle which is a fold in the
body wall that lines the shell.
eg; fresh water mussel snail
pila.
- Free living exclusively marine
forms.
- Adults are radially symmetrical
while larvae are bilaterally symmetrical.
- Body is represented by a
central disc covered by ossicles with spines called pedicellaria.
- Disc may bear extensions called
arms.
- Digestive system is complete.
- A unique ambulacral or water
vascular system is present.
- Tube feet are present for
locomotion and respiration. Tube feet are extended and retracted by
variation in hydraulic pressure of the fluid in them and contraction of
their muscles.
- Nervous system has a central
nerve ring with five radiating nerves.
- Reproduction is sexual. Sexes
are separate. Development is indirect.
- Show very high power of
regeneration.
- Tube feet are for feeding as
well.
o General
characteristics of protochordata -
o
·
Elastic, solid, ensheathed rod-like structure of vacuolated
turgid cells callled notochord is present may be through out the life or only during early
embryonic development mentioned above.
·
Paired pharyngeal gill slits( pharynx is perforated by gill
slits) is present which takes part in circulation of water for respiraton and
in higher chordates , they occur only in embryonic stage.
·
Ventral heart is present and gut lies ventral to nerve cord.
·
Post-anal tail is present and if present then it's for
balancing.
·
They are bilaterally symmetrical, triploblastic, coelomate with
organ system level of organisation.
Marine habitat.
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