2a. The diagram below represents a current hypothesis for the vertebrate animal

Question

2a. The diagram below represents a current hypothesis for the vertebrate animal phylogeny. Fill in the table to indicate when the following traits evolved in the phylogenetic tree. The numbers in the tree may be used in the table once or not at all. [7 pts; 1 pt each] Evolutionary Feature Lobe fins Number (1-7)- Leave blank if not applicable Amniotic e Jaws Mineralized skeleton Cranium Terrestrial limbs Hair Mammary glands Bilateral symmetr Hagtishes Jawless tishes Lampreys 2 Ray-fined fshes 3 Bony ??aw mouths"} 4 5 7

Explanation / Answer

The ddvelopment of lobe fins occured at stage 4. It first appeared in the coelacanths.

Amniotic egg is characteristic of reptiles. It first evolved in reptiles. This type of eggs contain amniotic fluid which provides a constant suutable surrounding to the developing embryo. So stage 7 will be correct.

Jaws first appeared in the chondrochythes. The jawless fishes are also said to be sucker fishes. After the evolution of jaw, it became easier to feed on the prey.

Here the stage will be 2.

Mineralized bones are the characteristics of bony fishes. It first appeared Ray finned fishes. So the stage wil be 3.

Cranium is present in hag fishes and onwards organisms. So herethe stage stated in the question dies not apply here.

Terrestrial limbs first appeared in the amphibians which helped it to survive both in water and land. So the stage will be 6.

Hair, mammary glands are charecteristic features of birds and mammals respectively. These organisms evolved after the evolution of reptiles. So the stages stated in questions are not applicable.

Lungs first appeared in the lung fishes. The development of lungs or the transition from gills to lungs paved the evolution of organisms suitable for survival in terrestrial condition.

So here the stage will be 5.

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