Difference Between Taxis and Tropism

The key difference between taxis and tropism is that the taxis refers to the directional movement of animals in response to a stimulus while tropism refers to the directional movement of plants in response to a stimulus.

Organisms show different reactions to internal and external factors. These reactions differ among the species. Plants react in a different way than the animals. Multicellular organisms react differently than unicellular organisms. Taxis and tropism are two such phenomena animals, and plants show respectively. Taxis is a motion or orientation of an animal in response to an external stimulus. On the other hand, tropism is the response of plants towards or away from a stimulus. Both taxis and tropism are directional reactions.

CONTENTS

1. Overview and Key Difference
2. What is Taxis
3. What is Tropism
4. Similarities Between Taxis and Tropism
5. Side by Side Comparison – Taxis vs Tropism in Tabular Form
6. Summary

What is Taxis?

Taxis is a process that shows directional movement or orientation of animals in response to an external stimulus. The whole body shows movements towards or away from the stimulus. Unicellular organisms, mainly protozoans show distinct taxis responses to different stimuli. Based on the type of stimulus, taxis are different types namely chemotaxis, phototaxis, etc.  Chemotaxis is the directional movement of an animal in response to a chemical. Chemotaxis can be either positive or negative. If the movement is towards the chemical, it is positive chemotaxis. The opposite is negative chemotaxis. Movement of ants toward sugar is positive chemotaxis while movement of mosquitoes away from mosquito coil smell is negative chemotaxis.

The directional movement of animals in response to light is the phototaxis. Similarly, it can be either positive or negative. As an example, movement of insects towards the light is positive phototaxis while the movement of cockroaches away from the light is negative phototaxis.

What is Tropism?

Tropism is the response of plants towards or away from a stimulus. The word ‘Tropism’ is mainly used to refer to how plants respond to external stimuli. Similar to taxis, tropism is also can be categorized based on the type of the stimulus and the direction of the response. Tropism is positive if it is towards the stimulus. If it is away from the stimulus, it is negative tropism. When the stimulus is sunlight, we call it as phototropism.

Phototropism may be positive phototropism or negative phototropism. When the stimulus is gravity, it is geotropism. It can be positive geotropism or negative geotropism. Some plant hormones involve the tropism of plants such as auxin, etc. When the stimulus is touch, it is thigmotropism.

What are the Similarities Between Taxis and Tropism?

• Taxis and tropism are two phenomena shown by organisms.
• They occur as a response to a stimulus.
• Taxis and tropism are directional responses.
• Both movements help organisms to survive in the environment successfully.

What is the Between Taxis and Tropism?

Taxis and tropism are responses shown by organisms against external stimuli. Animals show taxis while plants show tropism mainly. Both responses are directional and can be positive or negative. The below infographic presents the difference between taxis and tropism in tabular form.

Summary – Taxis vs Tropism

Taxis is the directional movements shown by animals as a response to a stimulus. Tropism is the response of plants to a stimulus. Both can be positive (towards the stimulus) or negative (away from the stimulus). Hence, they are directional responses. In taxis, the whole animal body may move. But in tropism, plants cannot move. Hence, plant parts show responses.  This is the difference between taxis and tropism.

Reference:

1.“Taxis.” Wikipedia, Wikimedia Foundation, 11 Aug. 2018. Available here  
2.Editors. “Tropism – Definition, Types and Examples.” Biology Dictionary, Biology Dictionary, 29 Apr. 2017. Available here

Image Courtesy:

1.”Chtx-AttrRep-en”By Kohlasz – Own work, (CC BY 3.0) via Commons Wikimedia  
2.”19762034863″ by Internet Archive Book Images (Public Domain) via Flickr