Vertebrate Zoology Paper (ZooII352) 2020

QUESTION NO 1;

Explain Evolution in terms of successive lifestyle from proto-chordates to Amphibians with valid reasons?

ANSWER;

Evolution:

Evolution is the modification in traits of a population through successive generations.

All living organisms reproduce, by which they pass on their characters to their offspring.

Evolution of protochordates to amphibians:

Protochordates containing both of the subphylums, and the phylum chordates, the vertebrates, have a hollow dorsal nerve chord , gill slits and a stiff supporting rod, the notochord, the forerunner of back bone . The major differences between protochordates are though back bone Lacking. Recent protochordates are thought to be evolved from ancestral stock as that which gives rise to the vertebrates Thus they are having same ancestor.

According to a theory, the ancestor was sessile ( attached ) , perhaps like a ptero-branch bud with an unspecialized larvae. These larvae adapted to an independent pelagic life and become sexually mature. Eventually, sessile stage was lost and vertebrates evolved from this free - organism. Another theory postulates that chordates evolved from mitrates.

1- Urochordate to Cephalochordates evolution:

An advancement occurred in the species of urochordates .They sustain all chordates characters throughout life.

2- Cephalochordates to vertebrates:

Vertebrates are evolved from cephalochardates. They are also called craniates due to reason that they contain cranium or brain box. Brain development is found. Integumentary system also develops.

3 - Vertebrates to Amphibians:

Due to some seasons these fishes decided to move to land .They evolved to amphibians .They are believed to be evolved from lobed fin fishes. The land terrestrial environment was a new sort of world for them, as they adapted accordingly.

* Why the organisms undergo Advancement:

It is the principle of evolution that nature selects the best and eliminates the rest. Organisms that wanted to survive, modified themselves. Today many organisms had become extinct due to the reason that they rejected change in their lifestyle.

 

---

QUESTION NO 2;

Why few aquatic organisms store waste product in their body! Why they do so, what are reasons to adapt such lifestyle, explain with respect to Evolution?

ANSWER;

 

1.       Storing waste in body:

Some Species from elasmo- branchii, store nitrogenous waste in their body. Subclass elasmobranchi contains sharks.

2.        Mechanism:

These organisms convert nitrogenous wastes into Urea in their liver. This urea is then stored in every body tissue of sharks.

3.       Reason:

This process is done in sharks to perform hyper osmotic to sea water. As the sea water's salinity in higher, so the shark accumulate urea (Waste product) in body, in order to be hyper osmotic in relationship to water off sea, thus they tend to gain water from ocean and do not have a worry about dehydration. 

4.       Reason with respect to evolution:

Sharks have evolved 450 million years ago. In Devonian era the first shark was evolved, namely leonodus shark, and was of freshwater habitat, but as time passed new species were and moved to marine environment, so they adapted this process of storing urea to help them survive.

---

QUESTION NO 3;

Can we relate Anurans with hemichordates? If yes how, if no why? State all possible reasons?

ANSWER;

Yes, we can relate anurans with hemichordates. Reasons are as under;

Reasons:

i.   Genetical Makeup:

                Research proved that 70% of hemichordate genes are similar to anurans. This means that both are cousins.

ii.   Fertilization:

                Both, hemichordates and anurans have external fertilization. This is an important character similarity of both.

iii.  Larval Stage:

                The newly produced offspring first experience larval stage in both groups.

iv.  Tongue: (In terms of feeding)

                Acorn worm contains a tongue like structure called proboscis, which it use for feeding similar to frog, which also use its tongue to capture prey.

v.    Deuterostomes:

     Both groups, anuran and hemichordates members are deuterostomes.

Conclusion:

From all above reasons, it’s shown that we can relate Anurans & hemichordates. It is because chordates are evolved from them, so there are similarities and relationship between them.

---