A taxis and a tropism are both different types of responses which are determined to due a (directional) stimulus to enhance chances of survival and be in more favourable conditions for itself.
A ‘taxis’ is present in motile organisms in which they respond directly to environmental changes by moving its whole body either towards a favourable stimulus or away from an unfavourable stimulus. There are a couple of ways to classify taxes depending on the effect of the stimuli. If the movement is towards the stimulus then it is known as photo taxis and if the movement is swaying away from the stimulus then it is known as negative photo taxis. Single-celled algae move towards light which increases their chance of survival as they are photosynthetic and need light to manufacture their food, this is an example of a positive photo taxis. Earthworms move way from light which increases their chances of survival because it takes them into the soil where they can conserve water, find food and avoid predators, this Is an example of a negative photo taxis. The prefix photo is dependent on the type of stimuli. When they are moving towards light it will be photo taxis, but if they are moving towards a certain area due to favourable conditions in terms of a chemical it is known as chemo taxis. A couple other types of taxis are thigmo taxis (a type of response due to touch) and thermo taxis (a type of response due to the change in the temperature)
A ‘tropism’ is a directional growth response which occurs only in plants due to a directional stimulus. It is controlled by a plant hormone called auxin produced in the stem tips and roots, which controls the direction of growth. Tropisms are named based on the different types of stimuli. Photo tropism is they way a plant grows or bends in response to light, geo tropism is the way a plant grows or bends in response to gravity. Other examples of tropism are chemo tropism (chemical) related, hydro tropism (water related) and thigmo tropism (touch related). Pollen from male flowers are positive and female flowers are negative so the two are mutually attractive. The airborne (male) pollen grains will attract and stick onto the receptive female flowers which results in a seed; this is a short example of electro-tropism.
There are multiple similarities that are concurrent in both taxis and tropism. They are both directional, which means they both directly move or grow in response to the stimulus. For example, bacteria moves towards areas with highly concentrated glucose and a plant will bend towards an area which has more light. Another similarity with taxes and tropisms is that they have a positive or negative response to the stimuli. This means that they either move/grow towards the stimuli (positive) or they move/grow away from the stimuli (negative). This could be a plant growing towards water or a certain organism moving way from light. An additional similarity is that their responses are both induced to help gain a competitive advantage and increase survival. Woodlice moving into the darkness avoiding predators are a perfect example of responding to increase rate of survival. One other similarity is that they are both innate behavioural responses. This means that these types of responses aren’t learn or taught by other organisms or plants. They automatically can respond from birth, as if it is hard-wired into its brain/nervous system the day they are born.
There are a few differences that are observable in taxes and tropisms. First of all taxes are only present in some motile organisms. This means that in any immotile organisms taxis cannot be present, such as in plants. Tropisms are only present in plants which help it grow and increase its chance of survival; however tropism isn’t restricted in only plants. Another difference is that in a taxis the motile organism can move to or away from a location to increase their chance or survival. They can completely relocate to avoid predators or move away from light to benefit them. However in tropism the plant can only stay in one place but slightly move or grow towards a stimuli or away a stimuli. If the conditions of the area that the plant is in happens to become suboptimal they can’t exactly just relocate, but can try to grow closer to the more favourable conditions.
In conclusion, taxes and tropisms are both very effective responses for motile organisms and plants in terms of helping increase their chance of survival every day by moving or growing towards more favourable conditions. They are both very similar and are only classified as different responses because of the fact that they occur in different things (motile organisms and plants) and the fact that they either move or grow. Otherwise, they should have the same name for the process that is occurring.
