Question

1. As fishes evolved in to amniotes, fertilzation:

   		evolved from external to internal
   		remained internal
   		evolved from internal to external
   		remained external

1 points   

QUESTIO14

1. Calcified teeth originated in the first:

   		vertebrates
   		gnathostomes
   		chordates
   		animals

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QUESTION13

1. When fossil evidence is taken to account, a bony skeleton appeared first in the:

   		first osteichthyans
   		first gnathostomes
   		first chordates
   		first vertebrates

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QUESTION 22

1. In most amniotes, the main site of gas exchange is the:

   		pharynx
   		skin
   		lungs

Answer 1

1. evolved from external to internal

Explanation - The lower vertebrates anamniotes which includes fish and amphibians lay their eggs into water and the external fertilization takes place where as the higher vertebrates amniotes includes reptiles,birds and mammals either lay their fertilized egg on land or keep the fertilized egg within the female partner. Amniotes have the egg which surrounded in sac like amnion structure ,it is characteristics of the internal fertilization.

14.Vertebrates

Gnathostomes has specific hard tissue lining the cartilage known as prismatic calcified cartilage (jaw) but doesnot contain the calcified teeth.The vertebrates developed the calcified teeth first and further got more developed in the carnivores animals.The invertebrates chordates have no teeth or bones developed.

13.first osteichthyans

The first bony skeleton got appeared in the bony fish osteichthyans and it had characteristics of lobe finned and ray finned. Gnathostomes,chordates and vertebrates developed after the osteichthyans.

14.Lungs

The amniotes ,lung is the primary site for gas exchange. The cutaneous and pharyngeal respiration occurs in most of the anamniotes (fish and amphibians) .