8. Write the characters of the following
phylum. a) Vertebrates c) Porifera b)
Arthropoda d) Echinodermata (4 Marks)
Answers
On a pleasant evening, you decide to go to a park. However, you end up having painful itchy eruptions on the skin. Clearly, you were bitten by an insect. After all, insects are everywhere. They belong to a group of animals called the Phylum Arthropoda, which form the largest percentage of the world’s organisms. They make up about 80 percent of the known species of animals! It is quite hard to escape them.
Phylum Arthropoda
Arthropods are joint-legged animals and you must have come across a few of these animals. Some prominent ones include insects, spiders, ants, bees, crabs, shrimps, millipedes, centipedes etc. Scientifically speaking, they all come under the Animal Kingdom under phylum Arthropoda.
The success of the arthropods can mainly be attributed to the presence of exoskeleton, which makes them versatile, is protective in nature and also allows flexibility and mobility. You can see arthropods living on land and in water.
Phylum Porifera
Have you seen SpongeBob Square Pants? How weird would it sound if it was called Porifera Bob Square Pants? The creator of this series was a marine biologist who was fascinated with the ocean and used many marine animals, including the Sponges in his animated cartoon series. Read along to find more interesting bits of scientific information about Porifera.
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Study Material»Biology for AIPMT»Animal Kingdom»Phylum- Annelida Arthropoda Mollusca and Echinodermata
Phylum- Annelida, Arthropoda, Mollusca and Echinodermata
PHYLUM - ANNELIDA
Lamarck coined the term Annelida.Free living found in moist soil, fresh water, sea or few are parasite.Body is soft elongated, cylindrical or flattened divided into segments or metamers by ring like, groves called Annuli.
Symmetry - Bilateral, Germ layer - Triploblastic, Level of organisation - Organ-system level having tube within tube plan.Anterior end forms a distinct head with sense organ in few annelids.Appendages are simple, unjointed, and locomotory having Chitinous Setae and ParapodiaBody wall consist of
(1) Cuticle - Thin moist albuminoid cutical allow free exchange of gas.
(2) Epidermis - Single layered epidermis made up of supporting cell, sensory and glandular cell.
(3) Muscle layer - (a) Circular layer, (b) Longitudinal layer. Muscle are smooth/unstraited.
Body wall may have minute chitinous setae.
First Protostomi eucoelomate animals.Body cavity is true coelom lined by mesodermal coelomic epithelium. Schizocoel.It is divided by transverse septa into compartment.It is filled with coelomic fluid that contains cells.As such there is no skeleton. Fluid filled coelom serves as a hydrostatic skeleton.
Digestive tract is complete, straight and extends through entire body. The gut has both circular and longitudinal muscles. Few annelids are sanguivorous. Digestive gland are developed for the first time in Annelida.
Respiration is through skin i.e. Cutaneous respiration. Some have gills (branchial respiration).
Circulatory system is closed. Some blood vessels enlarge to act as pumping heart. (Heart appear first time in annelids)
The blood is red with haemoglobin dissolved in plasma (Erythrocruorin). It has amoeboid corpuscles only. Few Annelids like Seballa have Chlorocruorin as a respiratory pigment also. Hirudinaria has circulatory system with haemocoelic system.
Excretory organ is Nephridia. Coiled tubules also helps in osmoregulation.
Excretory matter
(1) Ammonia in aquatic form
(2) Urea in land form
Nervous system consist of –
A circumenteric nerve ring, Double, midventral nerve cord with ganglia. Sence organ chemoreceptor, photoreceptor & tentacle, palp, eyes may be present.
Sexes may be separate or united. Asexual reproduction by budding' or fission in some cases also. Atoke (asexual), Epitoke (sexual) Phenomenon also found (Nereis).
Cleavage is spiral and determinate unqual & holoblastic.
Regeneration is usually found. Life history induds a trochophore larva in few Annelids.
Nereis: Inhabits in sea - shore between tide mark, burrows, Nocturnal, Carnivorous, Gregarious, Fertilization - in sea.
Parapodia in each segment except first & last.
During breeding body divides in two parts anterior asexual part - Atoke and posterior sexual portion Epitoke. This change is known as epitoky.