Answer:
The one of best example would be appendix in humans.
Explanation:
In the past, the appendix may have helped in the digestion of the plants by producing mucus and prevent any type of infection. Plants with a high content of cellulose are digested with the help of the appendix as reported.
It is not a part of the human digestive system and considers as a vestigial organ. Vestigial organs are the organs that are present in an organism with no particular function and their removal will not lead to any harm. Humans do not need it because our digestive system is more efficient and works better in the first stages of digestion than they used to.
Thus, the correct answer is - appendix in humans.
A model organism is a species that has been widely studied to understand a particular biological phenomena, normally used because they are easy to breed and maintain in a laboratory setting and has certain experimental advantage.
The criteria that Thomas hunt Morgan was looking for include; the model organism should be small in size, easy to keep in the laboratory and also able to produce large number of off springs in a short time.
A holdfast is a root-like structure that anchors aquatic sessile organisms, such as seaweed, other sessile algae, stalked crinoids, benthic cnidarians, and sponges, to the substrate.
