Difference Between Sessile and Motile

Key Difference – Sessile vs Motile
 

The key difference between sessile and motile is that the Sessile organisms are not capable of moving from one place to another while Motile organisms are capable of moving from one place to another. Sessile and Motile are two different terms that describe certain morphological features of organisms living on earth. All living organisms can be grouped into these two categories based on their motility. This type of grouping is very primitive and categorizing organisms into these two groups is somewhat problematic. For example, some sessile organisms have immature stages that are motile and vise-versa. Therefore, this criterion is not considered when classifying the organisms into different taxonomical stages. However, this demarcation of organisms is important as a first approximation. In this article, the differences between sessile and motile will be further discussed.

What is Sessile?

Sessile is the term used to explain the organisms that cannot move from one place to another place. Plants are considered as sessile organisms. In general, sessile organisms respond to the environmental changes mainly by changing their forms. For example, the tree, being a sessile organism responds to light by exposing its foliage towards the sunlight. Moreover, the plant growth occurs towards the light, and the leaves are oriented at correct angles to receive the maximum amount of light. Thus, the environmental factor; the light can change the form of the tree by changing its growth.

Most of the earliest organisms are sessile and have simple techniques to obtain nutrients. Sessile organisms have to develop effective methods to protect themselves from predators. For this purpose, most sessile organisms have developed structural changes with the help of various chemicals like calcium carbonate (in corals), silica, lignin (in plants), etc

What is Motile?

Motile is the term used to explain the organisms that can move from one place to another. Most of the organisms including animals, humans, etc., are motile. However, some sessile animals like corals, sponges, some worms, etc., have motile larval stages. Unlike the sessile organisms, motile organisms respond to environmental changes by changing their behavior. A good example is the migration of animals like fishes, wildebeests, zebras, etc., due to the unfavorable climatic conditions. Most motile animals have active feeding methods.

What is the Difference Sessile and Motile?

Definition of  Sessile and Motile

Sessile Organisms: Sessile organisms cannot move, and they live in one place.

Motile Organisms: Motile organisms can move from one place to another place.

Characteristics of Sessile and Motile

Way of responding to environmental changes

Sessile Organisms: Sessile organisms respond by changing their body form.

Motile Organisms: Motile species respond by changing the behavior.

Feeding Methods

Sessile Organisms: Many sessile organisms show passive feeding methods.

Motile Organisms: Many motile organisms show active feeding methods.

Nutrient Requirement

Motile Organisms: Most of the motile organisms have a greater number of ways to obtain food, but at the same time their nutrient requirement is high when compared to sessile organisms.

Sessile Organisms: Sessile organisms have few ways to obtain food that includes photosynthesis

Examples of Sessile and Motile Organisms 

Sessile Organisms: Examples for Sessile organisms are plants, corals, barnacles etc.

Motile organisms: Examples for Motile organisms are Humans, animals, etc.

 

Image Courtesy:

“Meandrina meandrites (Maze Coral)” by Nhobgood Nick Hobgood – Own work.  (CC BY-SA 3.0) via Wikimedia Commons 

“Connochaetes taurinus -Wildebeest crossing river -East Africa” by Eric Inafuku – originally posted to Flickr as Wildebeest Crossing

(CC BY 2.0) via Wikimedia Commons