Responses to Stimuli: Taxes

Question 1

what is a taxis?

Answer 1

a taxis is a simple response whose direction is determined by the direction of the stimulus

Question 2

how do motile organisms respond to environmental changes?

Answer 2

by moving its whole body either towards a favourable stimulus or away from an unfavourable stimulus

Question 3

what are the 2 ways taxes are classified by?

Answer 3

1. according to whether the movement is towards/away from the stimulus
2. the nature of the stimulus

Question 4

what is it called when the movement is towards the stimulus?

Answer 4

positive taxis

Question 5

what is it called when the movement is away from the stimulus?

Answer 5

negative taxis

Question 6

when single-celled algae move towards light (positive phototaxis), how does this increase their chances of survival?

Answer 6

as they are photosynthetic and require light to produce their food

Question 7

when earthworms move away from light (negative phototaxis), how does this increase their chances of survival?

Answer 7

as it takes them into the soil where they are better to conserve water, find food and avoid predators

Question 8

some species of bacteria will move towards a region where glucose is more highly concentrated (positive chemotaxis), how does this increase their chances of survival?

Answer 8

as they use glucose as a source of food