Theory question 106
Nutrient Cycling(For candidates in Nigeria only)
(a) Complete the table below by naming the nutrient cycle that involves each of the given processes and give three other processes involved in the nutrient cycle.
Process | Nutrient cycle | Three other processes involved in the named nutrient cycle
Combustion | ________ | ________
Precipitation | ________ | ________
Lightning | ________ | ________
(b)(i) What is irritability?
(ii) Complete the table below by stating the type of response elicited by each of the given actions.
Action | Type of response
Euglena moving towards source of light | ________
Opening and closing of Mimosa plant leaves | ________
Mosquitoes avoiding repellants | ________
Earthworm moving away from light | ________
Sperm cell moving towards chemical substances of an ovum | ________
Four o'clock plant opening at 4.00 p.m. | ________
Shoot of bean seedling growing towards sunlight | ________
(c) Name three animals each that exhibit: (i) territoriality; (ii) seasonal migration; (iii) display.
Show the model answer
(a) Combustion — carbon cycle — photosynthesis, respiration, decay/decomposition (also feeding, fossilisation).
Precipitation — water cycle — evaporation, transpiration, condensation (also run-off, infiltration).
Lightning — nitrogen cycle — nitrogen fixation by bacteria, nitrification, denitrification (also putrefaction/ammonification, absorption by plants).
(b)(i) Irritability is the ability of a living organism to detect and respond to changes (stimuli) in its environment.
(ii) Euglena towards light — positive phototaxis; Mimosa leaves closing — nastic movement (thigmonasty/seismonasty); mosquitoes avoiding repellents — negative chemotaxis; earthworm away from light — negative phototaxis; sperm towards ovum's chemicals — positive chemotaxis; four o'clock flower opening at 4 p.m. — nastic movement (photonasty/nyctinasty); bean shoot towards sunlight — positive phototropism.
(c)(i) Territoriality: agama lizard, dog, lion, robin, cock, fish such as tilapia. (ii) Seasonal migration: swallows/cattle egrets/storks, wildebeest, salmon, locusts, eels. (iii) Display: peacock, agama lizard, cock/turkey, birds of paradise, frogs.
Taxis is movement of a whole organism; tropism is a growth response; nastic responses do not depend on stimulus direction.