1.8 - PRIMARY PRODUCTIVITY

Question 1

Productivity in marine ecosystems is relatively low in comparison to terrestrial ecosystems.

Which of the following addresses how plants have adapted to the lack of visible light in marine ecosystems?

a) The phytoplankton have evolved to absorb ultraviolet light.
b) The phyoplankton have evolved to absorb red light.
c) The phytoplankton have evolved to reflect red light.
d) The phytoplankton have evolved to absorb red, blue, and green light.

Answer 1

Choice D is the correct answer.

In plants, the pigment that gives them the green color is called chlorophyll. Typically, this pigment wll absorb red and blue light and reflect off the green in the process of photosynthesis.

This available light (red and blue) can only reach so far into the depths of the ocean. Over time, to continue to carry out photosynthesis at greater depths of the ocean, the phytoplankton have evolved the ability to absorb green light as well.

Question 2

Sugar beets are among the most photosynthetically efficient plants in the world.

The average photosynthetic efficiency of sugar beets is

a) 1%
b) 5%
c) 10%
d) 40%

Answer 2

Choice A is correct.

Photosynthesis is around 1% efficient on average.