Phytoplankton are often small in size and irregular in shape. (i) Define the term ‘phytoplankton’. (ii) Identify and briefly explain TWO advantages that phytoplankton obtain by being small in size and irregular in shape.

Question 1

What is meant by the term phytoplankton?

Answer 1

Phytoplankton = photosynthetic plankton (includes prokaryotes and eukaryotes)

Question 2

What are the two advantages of being small in shape and irregular in shape?

Answer 2

• High surface to volume ratio
• Movement through the water
o Viscosity- stickiness of the water leads to impede movement
o Inertial forces: tendency of a moving object to continue moving
o Implications of small size: movement is strongly influenced by viscosity of water, which means that they sink relatively slowly
o Also means that the SA:VOL ratio is high compared to larger objects, which may further reduce the sinking rate and may also assist with the assimilation of nutrients.

Question 3

What are the implications of irregular shape?

Answer 3

(1) retardation of sinking meaning less energy to maintain a position in the euphotic zone
(2) Aid in the assimilation of nutrients (nutrient availability may limit primary productivity in marine systems)