Question

Planaria, insects, octopus and vertebrates all have eyes. Can we group of these animals together to establish a common evolutionary origin? Justify your answer.

Answer 1

Hint: Phylogenetics is defined as the evolutionary relationship between the organisms. Different characters are used to find the evolutionary relationship between the organisms. DNA alignment between the different organisms is the best mode of finding the evolutionary origin or their relationship.

Complete answer:
It is given that planaria, insects, octopus and vertebrates have eyes. The eye trait can be used to study the evolutionary history of development of eyes.

The brief description of development of eye is given as:
- Planaria belongs to the phylum Platyhelminthes. Planaria has the least advanced eyes as compared to the other organisms. Planaria shows the early design of rudimentary eyes. There are found random changes which lead to a depression in light sensitive areas. This helps the planaria to see sharper.
- Insects belong to the phylum Arthropoda. The ommatidia are developed in the eyes of insects. This ommatidia provides a better vision as compared to the planaria.
- Then octopus and vertebrates develop lenses in their eyes which act as a pin-hole camera. Octopus belongs to the phylum Mollusca. Vertebrates belong to the phylum chordata. Over time, nerve fibres are passed through the retina which transmit the signal to the brain.

Hence the presence of different kinds of eyes in these organisms depicts a separate evolutionary origin.

We can’t say that planaria, insects, octopus and vertebrates are found in a group which have the same evolutionary origin. We have to look for other characteristics of classification to determine their relationship such as symmetry, body plan, mode of organization, mode of nutrition etc.

Note: Look for the other characters of classification for determining the common evolutionary origin of different organisms. Because when we look for a single character, then it will give false results. Other characters include extraction of genomes of the organisms and then classify the organisms on the basis of their similarities.