Question

Give scientific reasons.
a. Though tortoise lives on land as well as in water, it cannot be included in class- Amphibia.
b. Our body irritates if it comes in contact with jelly fish.
c. All vertebrates are chordates but all chordates are not vertebrates.
d. Balanoglossus is connecting link between non-chordates & chordates.
e. Body temperature of reptiles in not constant.

Answer 1

a. Tortoise belongs to the class reptilia and does not show any characteristic which is similar to the class amphibia except that it can live in both land and water. There are certain characteristics which are common to the amphibians which are not applicable for reptiles. For example: amphibians have moist skin, neck is absent, external ear is in the form of tympanum whereas reptiles have dry and scaly skin, neck is present and external ear is absent. So, we can say that tortoise is a reptile and not an amphibian based on the above characteristics.

b. Jelly fish has special cells on its tentacles called cnidoblasts. These cnidoblasts contain toxins which is a protective mechanism shown by organisms belonging to the phylum Cnidaria.
On touching the jelly fish, this toxin is released which results in irritating of the body.

c. The members of Vertebrata possess notochord during embryonic development. Thus, all vertebrates are chordates. However, the notochord gets replaced by a cartilaginous or bony vertebral column in the adult. Thus, all chordates are not vertebrates.

d. Balanoglossus is considered a connecting link between chordates and non chordates because it shows characteristics which are present in both the phylums. For example, Balanoglossus shows the presence of notochord and pharyngeal gill slits which is a characteristic feature of chordates. It also shows the presence of heart which is dorsal just like non chordates.

e. Reptiles are cold blooded organisms or poikilotherms which means they are not able to regulate their body temperatures. Their body temperatures change with the change in the temperature of the environment. For example, if the outer temperature rises their body temperature also rises and vice or versa. This can be explained from the observation that when the temperatures drops, these reptiles bask themselves in the sun whereas when the temperatures are high, they would hide under the shades.