Plants and animals carry out cellular respiration, but only plants conduct photosynthesis.
Scientists have named and cataloged 1.3 million species and researchers estimated that there are, in total, 390,900 known plant species in the world.
The figures above is just an attempt to compare and contrast the number of organisms that respire to those that photosynthesize as knowing the number of species on Earth is one of the most basic yet elusive questions in science.
This is an inexact science as counting the number of organisms and their species is virtually immeasurable. Obtaining an accurate number is constrained by the fact that most species remain to be described and because indirect attempts to answer this question have been highly controversial.
How many more species there are left to discover is a question that has hovered like a cloud over the heads of taxonomists for two centuries.
Boris Worm, a marine biologist at Dalhousie University in Nova Scotia, Dr. Mora and their colleagues estimate that there are 8.7 million species on the planet, plus or minus 1.3 million.
For now, we can probably settle by stating that most organisms respire but animals and humans do not photosynthesize.
Photosynthesis and cellular respiration are connected through an important relationship. This relationship enables life to survive as we know it. The products of one process are the reactants of the other.
Learn more about photosynthesis and cellular respiration at CK12.org.