Question

Choose the correct difference from the following.

| Pristis| Catla
---|---|---
1.| 3-chambered heart| 2-chambered heart
2.| Small placoid scales| Large placoid scales
3.| Ventral mouth| Terminal mouth
4.| Swim bladder is present| Swim bladder is absent

A. 1
B. 2
C. 3
D. 4

Answer 1

All fishes have 2 chambered hearts, consisting of an atrium and a ventricle. The Placoid scales are the thin, rough, scales. Pristis is a shark type fish, with small structures like teeth called placoid scales, also known as dermal denticles.

Complete Answer:
- A fish body is divided into a head, a trunk and a tail, but there is not always a visible outward distinction among the three. The cartilage or bone is the backbone comprising the supporting structure inside the fish.
- The key feature of this skeleton is the spine, which consists of light but solid articulating vertebrae. There are no legs or limb girdles. The ribs bind to the backbone. The fish's principal external characteristics, fines, are either bony or soft spines called "rays'' and are not directly related to the spine, aside from the caudal fins.
- The muscles that comprise the principal part of the trunk are supported. The heart has 2 chambers and the blood flows through the gill surfaces, then in a single circulatory loop across the body. The eyes are ideal for underwater viewing and only provide local vision. An inner ear remains, but there is no outer or middle ear.
- All fishes have 2 chambered hearts, consisting of an atrium and a ventricle. The Placoid scales are the thin, rough, scales. Pristis is a shark type, with small structures like teeth termed placoid scales, also named as dermal denticles. In bony fish such as Catla, placoid scales are absent.
- On the ventral portion the mouth and nostrils are present in Pristis. The comparatively tiny or pointed head and terminal mouth will easily be found in Catla. The swimming bladder is an internal gas organ that lets certain bony fish like Catla but not cartilage fish like Pristis regulate their booming and thus remain at the current water level without having to expend energy in swimming.

Thus, the correct answer is C. i.e., 3.

Note: The fish's principal external characteristics, fines, are either bony or soft spines called "rays" and are not directly related to the spine, aside from the caudal fins. On the ventral portion the mouth and nostrils are present in Pristis. The comparatively tiny or pointed head and terminal mouth will easily be found in Catla.