Within the hierarchy of taxonomic classification, a phylum is situated between kingdom and class.
Are short, or long, or round like fritters;
They go through life with but one cell
And seem to manage very well.
Protozoa exist throughout aqueous environments and soil, occupying a range of trophic (nutritional) levels. As predators, they prey upon unicellular or filamentous algae, bacteria, and microfungi.
Protozoa play a role as both herbivores and consumers in the decomposer link of the food chain.
Protozoa also play a vital role in controlling bacteria populations and biomass and they may absorb food via their cell membranes, some; for example, amoebas, surround food and engulf it, and yet others have openings or "mouth pores" into which they sweep food.
All protozoa digest their food in stomach-like compartments called vacuoles.
We look with scorn on beasts below,
And say, "We're holier than thou."
Sponges have bodies that consist of jelly-like mesohyl (the gelatinous matrix within a sponge) sandwiched between two thin layers of cells with an endoskeleton and branching water intake canals lined by flagellated collar cells for feeding and excretion.
Water passes through these animals by way of the canals and a series of flagellated chambers (lash-like appendages used for locomotion) and exits via large channels and pores or oscula.
A hollow body doth bespeak.
These creatures jellyfishes be,
Hydras and corals of the sea,
The sea fan and anemone.
Coelenterata is an obsolete term encompassing two animal phyla, the Ctenophora (comb jellies) and the Cnidaria (coral animals, true jellies, sea anemones, sea pens, and their allies).
The name comes from the Greek koilos, "full bellied", referring to the hollow body cavity common to these two phyla. They have very simple tissue organization, with only two layers of cells, external and internal.
Gliding slowly with graceful ease,
Go the ctenophores, whose Greek name
The comb-bearers doth proclaim.
Commonly known as comb jellies, they are a phylum of animals that live in marine waters worldwide. Their most distinctive feature is the "combs", groups of cilia that they use for swimming, and they are the largest animals that swim by means of cilia.
Adults of various species range from a few millimeters to 1.5 meters (59 inches) in size. Their bodies consist of a mass of jelly with one layer of cells on the outside and another lining the internal cavity.
Or else invade some creature's liver.
All these worms are very flat:
Platyhelminth means just that.
Unlike other bilaterians (a front and a back end, as well as an upside and downside) they have no body cavity, and no specialized circulatory and respiratory organs, which restricts them to flattened shapes that allow oxygen and nutrients to pass through their bodies by diffusion.
part way up the scale are we,
From amoeba's simple features
Unto man's complexity.
Mesozoa were once thought to be evolutionary intermediate forms between Protozoans and Metazoans, but now they are thought to be degenerate or simplified metazoa.
Trace our name to Nemertes,
Lovely goddess of the seas;
And like her, as shown in art,
We're fatter in our tummy part.
Add to it ferro, or I bear,
And Rotifera will reveal
The sort of creatures that we are.
And you will have said in Greek,
"Stomach bristle", which describes
The bristle-belly's various tribes.
If this sounds a bit ill-bred,
Hairy stomach say instead.
He meant (so I've been told) "a thread";
And when he oidea did exclaim,
These thready wormlets got their name.
To the mind suggests a worm;
This again suggests another,
To wit the one which gave such bother
To the Emperor Alexander
That it raised his royal dander!
Of animals with spiny necks.
Echinodera, in the Greek,
Means this; but these specks are unique.
So very old that they're antique.
Prefixed to cephale, the head,
Makes up this name which you've just read,
This name, compounded from these terms
Is most appropriate for these worms.
Of this Greek-compounded term,
Signifying that in cleaning
Its digestive tube, this worm
Uses an internal pore
Just inside its lophophore.
And oidea means "like";
Sometimes this worm is like a club;
Again, it's like a spike.
Outstretched to feed, it's long and thin;
In fright bunched up, its tube within.
Echiuroidea, tail of a snake.
But these worms a snake's tail do seem to resemble
As much as a necktie doth look like a thimble!
Our name is derived; yet 'tis known that we oft
In shelly encasements our bodies enclose
To give us protection from ravenous foes.
Indicates the common worm;
But Annelida, some folks claim,
Is the preferable name.
Through life with clumsy steps and slow;
Yet they are highly organized,
A fact not often recognized.
Whose chief diagnostic feature
Is its jointed legs: that is,
Articulate appendages.
Arthro, joint, affixed to pod,
Makes a name correct, though odd.
Pursues its life without a squirm;
The creature is an ocean roamer,
Its title, "worm," is a misnomer.
Anatomically correct,
Is a name that's almost heinous
To the socially elect;
Yet the name means nothing more
Than outside the lophophore.
A lophophore is a circular or horseshoe-shaped structure of tentacles around the mouth of a bryozoan or brachiopod that is used for capturing food.
Someone did together put,
One who deemed himself a scholar.
(Wish I had him by the collar!)
Where the dickens they should go,
Above the lamp shells or below!
From a king they take their name,
Phoronis, of classic fame.
Was the ancient Priapus,
An old classic deity,
God of all fertility;
And we worms look like a part
Of him shown in classic art.
We are prickly without but all mushy within;
Our parts are spread out in fives, like a star;
We are called pentapartite, and that's what we are.
More than this they can't afford;
Deep within their frame it lies,
One of nature's mysteries.
And phorein means to wear the same.
In ocean's depths, unseen, unheard,
For ages lived a bearded worm;
'Twas caught, whole and alive,
And named in nineteen fifty-five.
You'll detect in Chordata a certain affinity
With chord, which refers to a rod in the back,
A specialized structure which other beasts lack.