DISTINGUISHING FEATURES OF MAIN
PHYLA IN ANIMAL KINGDOMS
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Living organisms are grouped according to their evolutionary closeness. The science of classification is known as taxonomy. In classification the organisms are grouped into units called taxa. The largest taxon is a kingdom which is subdivided into phyla. Each phylum is made up of classes. Each class has several orders. Each order is made up of several genera (singular genus). Each genus has many species.A species is the basic unit of classification. It is group of organisms that can interbreed to produce viable offspring.The main phyla in the animal kingdom and their distinguishing features are as follows:
1. PORIFERA (Sponges)
The body has pores hence the name of the phylum Porifera.
Thepores link interconnecte chambers in the organism to the outside.
All are sessile. Skeleton is made up of calcium, silica or horny spicules.
All are marine.
Examples: Leucosolenia, Sycon.
2. COELENTERATA
Sea-like body cavity which also serves as a gut cavity and is calledenteron.
Radial symmetry.
The body wall has two layers of cells i.e., they are diploplastic, theouter layer is called ectoderm and the inner is called endoderm.
They have stinging cells called nematocysts.
Examples: Hydra, Obelia, Portuguese man of war, Coral, Sea anemone.
3. PLATYHELMINTHES (Flatworms)
The body is flattened dorso-ventrally.
The body has only one opening – the mouth but no anus.
Branched alimentary canal.
Special cells called flame cells are present for excretion and osmoregulation.
Examples: Flukes, tapeworms.
4. NEMATHELMINTHES/ASCHELMINTHES (Round Worms)
Rounded in cross-section. Have a narrow body pointed at both ends.
They have a thick elastic cuticle cover.
All are parasites.
Examples: Round worms, hookworms, filarial worms, threadworms.
5. ANNELIDA (Segmented worms)
The body is made up of a serial repetition of segments that are formed in the embryonic stage. This is called metameric segmentation.
They are triploblastic animals i.e., the body has three layers i.e.ectoderm, endoderm and a middle mesoderm. The mesoderm secretes a fluid called coelom and therefore the organisms are said tobe coelomate.
Examples: Earthworms, leeches.
6. MOLLUSCA (Soft bodied animals)
The ventral side of the body has a soft muscular foot hence the name of the phylum.
On the dorsal side is the visceral hump containing the main digestiveorgans.
The visceral hump is generally (but not always) protected by a shell.
Most have a tongue like structure used for feeding called radula.
Examples: Snails, octopus, squids, slugs.
7. ARTHROPODA (Joint-legged animals)
They have jointed appendages (projections from the body).
Exoskeleton made up of cuticle.
They shed the exoskeleton periodically – a process called moulting orecdysis.
Examples: Crustaceans, millipedes, centipedes, arachnids, insects.
8. ECHINODERMATA (Spiny skinned animals)
The skin has plate-like structures called ossicles and spines made upof calcium.
Exclusively marine.
They have bilateral symmetry as larvae but radial symmetry as adults.
They have a water-vascular system with tube feet for locomotion.
Examples: Sea urchins, brittle stars, sea cucumbers and sea star.
9. CHORDATA
All have a strengthening rod known as notochord.
They have a dorsal hollow nerve chord.
They have muscle blocks called myotomes.
A post anal tail and perivisceral clefts present.
Examples: tunicates, lancelets, jawless fishes, jawed fishes,amphibians, birds, reptiles and mammals.
Distinguishing Features of main Phyla/Divisions in the Plant Kingdom:
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1. THALLOPHYTA
The plant body is a thallus i.e. not differentiated into root, stem and leaf.
They have a wide variety of body forms and sizes, ranging from microscopic unicellular organisms to large sea weeds.
Examples: Green algae (chlorophyta) e.g. Spirogyra – blue-green algae (Cyanophyta) – brown algae (Phaeophyta) – red alga(Rhodophyta).
2. BRYOPHYTA
They show clear – cut alternation of generation.
Haploid gamete producing gametophyte alternates with diploid spore.
Gametophyte is the more prominent phase in the life cycle.
Gametophyte is anchored to ground by filaments called rhizoids.
Sporophyte is parasitic on gametophyte.
Examples: Mosses and lichens
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3. PTERIDOPHYTA
These show prominent sporophyte in the life cycle.
Sporophyte has roots, stems and leaves with vascular tissues.
Sporophyte is independent of gametophyte. They have more differentiation of tissues.
Examples: Ferns and horsetails.
4. SPERMATOPHYTA
Seed bearing plants.
They have separate male and female spores (pollen grains andembryo sac respectively).
Embryo sac is enclosed in ovule which, after fertilization, develops intoseed.
Complex vascular tissues in roots, stems and leaves present.
Examples: Gymnosperms and Angiosperms.
Gymnosperms are ‘naked seed-bearing’, not dependent on free water forfertilization e.g. cycads and conifers. Angiosperms are flowering, seed-bearing, depend on pollinating agents, do not depend on free water for fertilization e.g. monocots and dicots