Some people have suggested that Tardigrades (water bears) come from another plan

Question

Some people have suggested that Tardigrades (water bears) come from another planet. Look at the phylogenetic tree, which has been constructed based on DNA and morphological data, to A) explain whether the alien origin of Tardigrades is supported. B) How would the phylogenetic tree look like if Tardigrades were indeed alien?

Pseudocoelomates Segmented Eumetazoa Protostomes Deutero- stomes Spiralia Acoelo- morpha Ecdysozoa Platyzoa Lophotrochozoa Bilateria Metazoa Phylogenetic tree of animal phyla. The red circles depict animal groups that present a trait known as pseudocoelom, while the blue circles depict animal groups that show a pattern of segmentation

Explanation / Answer

A)

Tardigrades are often called water bears. These are microscopic and aquatic creatures found in different places on earth. They have four pair of legs that end with 4-8 claws and are close relatives of Arthropoda. These are able to withstand and tolerate extreme climatic conditions, which includes temperature below zero degrees and above boiling temperature by a process called anhydrobiosis. These organisms can tolerate extreme temperatures only for specific period.

If the tardigrades have come from space then they require vehicle like meteors to cross earth’s atmosphere. The meteors can be hot as 15000C but these animals are unable to tolerate temperatures above 1100C. Thus, the tardigrade cannot be considered as aliens.

B)

If the tardigrades have come from space and are aliens then they will have ability to tolerate very high temperatures. They do not have any genetic relation with animals on earth.

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