Photosynthesis Photosynthetic Organisms 5

Question 1

Which photosynthetic organisms form the base of hydrothermal vent ecosystems where sunlight cannot reach?

Accepted Answer

Chemolithotrophic bacteria using chemosynthesis

Answer

Chemosynthetic bacteria near hydrothermal vents use chemical energy from hydrogen sulfide instead of sunlight to fix carbon.

Question 2

Sphagnum moss is ecologically important in peat bogs primarily because it:

Accepted Answer

Accumulates incompletely decomposed organic matter storing vast amounts of carbon

Answer

Sphagnum peat bogs store enormous amounts of carbon in slowly decomposing organic matter, making them critical carbon sinks.

Question 3

Which ancient photosynthetic organisms are preserved as stromatolites found in rocks over 3.5 billion years old?

Accepted Answer

Cyanobacteria

Answer

Stromatolites are layered structures formed by cyanobacterial mats, representing some of the oldest evidence of life on Earth.

Question 4

A mixotroph differs from a strict autotroph in that it:

Accepted Answer

Can use both photosynthesis and organic carbon consumption for energy

Answer

Mixotrophs like Euglena and some dinoflagellates can switch between photosynthesis and heterotrophic feeding depending on light availability.

Question 5

Cryptomonads are unique photosynthetic protists because their chloroplasts contain remnants of:

Accepted Answer

A previously engulfed red alga (secondary endosymbiosis)

Answer

Cryptomonad chloroplasts arose through secondary endosymbiosis — a eukaryote engulfed a red alga, whose reduced nucleus (nucleomorph) persists inside the plastid.

Photosynthesis Practice Test

Photosynthesis Practice Test

Photosynthesis Photosynthetic Organisms 5