1. Hemichordates constitute a phylum of marine, worm-like deuterostome animals. The animals of this phylum have a unique characteristic of bilateral symmetry and triploblasticity.

As their name suggests, hemichordates are half-chordates. They share several distinguishing as well as homogenous features with chordates. Some underlying differences between hemichordates and chordates are:

Hemichordates	Chordates
They have an epidermal nervous system.	They have a central nervous system.
They never develop a notochord	They develop a notochord at some stage of development
They have a trunk, no tail.	They have a post-anal tail
Their feeding mode primarily involve cilia	They have a diverse range of feeding modes, apart from cilia.
They inhabit only marine surroundings	They can inhabit the air, water, and land.
They are considered primitive.	they are considered advanced than hemichordates.
These are invertebrates.	These include vertebrates

Some unique similarities between hemichordates and chordates:

They share a common ancestry and hence are evolutionarily related.

Both are deuterostomes, that is they have bilateral symmetry.

Both are triploblastic.

They both contain slits in the pharyngeal gill.

Both are coelomates.

Both of them contain organ-level differentiation.

2. There are several distinguishing features between lampreys and hagfishes, these are tabulated as follows:

Hagfish	Lamprey
Their development is rather direct, no larva is formed in its development.	Their development is indirect and is facilitated via ammocoete larva.
No metamorphosis is present.	Metamorphosis is present.
They are hermaphrodite (bisexual)	They are unisexual.
They have only one pair of external gill slits.	They have seven pairs of external gill slits.
They have smaller teeth and a fully developed tongue.	They have larger teeth with primitive development of tongue.
Their skin is comparatively slimy.	Their skin is less slimy
They are exclusively marine animals. They never enter freshwater.	They can be found in marine as well as freshwater bodies.
They constitute only parasitic species.	They constitute both parasitic as well as nonparasitic species.

3. Different kinds of fish scales can be enumerated and described as follows:

I. Placoid Scales: These types of scales have structural similarity to teeth. These are embedded in the skin of the fish and are developed on a rectangular plate base. The interior of these scales receives blood from the vascular system. These scales are commonly found in sharks and rays.

II. Cosmoid Scales: These types of scales are developed on two base plates and their inner layer is made of lamellar bone. These scales develop with the growth of the fish. these are evolved from the fusion of two placoid scales. These scales were prominently found in extinct species Crossopterygians, and found today in lungfish.

III. Ganoid Scales: These are flat and basal structured scales. These never overlap but fit together and are also considered modified cosmoid scales. Their outer layer is made of an inorganic bone salt, called ganoine. They grow in length, breadth, and thickness with the growth of the fish. These types of scales are found in gars and bichirs.

IV. Leptoid Scales: These are thinner as well as translucent scales. These lack dentine or hard-enamel layers. They develop in concentric forms with the growth of the fish. They overlap in a head to tail configuration. These types of scales are found in higher-order bony fishes.

4. Different types of feathers are listed as follows:

I. Flight Feathers: These are long feathers that give the birds the strength to fly. These can be found in the wings and the tail.

II. Contour Feathers: These feathers give the color and shape to the bird. These feathers help insulate the birds and can be found everywhere except legs and feet.

III. Down Feathers: These are soft fluffy feathers that can trap air to insulate the birds. These have little or no shaft.

IV. Bristle Feathers: These are very stiff feathers with few barbs at the end. These can be found around the eyes and the mouth.

V. Semiplume Feathers: Found below contour feathers, these provide insulation to the birds. They do not have a well-structured shaft.

5. Different types of mammalian horns are listed as follows:

I. Bovine Horns: These horns protrude from the skull and are covered by the protein keratin. These curve and curl, and do, not branch. Found in cows, goats, and sheep.

II.Rhino Horns: These horns do not constitute a bony horn core. These are wholly made up of keratin protein. They have calcium and melanin for the provision of strength.

III. Giraffe Horns: They are permanent horns that do not branch. They are covered not by keratin but by skin and hair.

IV. Pronghorn Horns: These horns branch having two prongs. These horns are shed annually and their bony core is covered by keratin.

V. Antlers: Not traditionally considered as horns, but are similar to horns. These are only found in the male of the species of deers. These are made only of bony cores and no keratin protein. Antlers are also shed once a year, like pronghorn horns.

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