Concept:Ruminants and the bacteria in their digestive tract share a close, mutually beneficial relationship.
Explanation:Ruminants such as cattle and sheep cannot digest cellulose by themselves.
Bacteria in the rumen produce cellulase, an enzyme that breaks down cellulose into simple sugars.
The ruminant then absorbs these sugars for energy.
In return, the bacteria receive a warm, moist habitat and a constant food supply.
When some bacteria die, the ruminant digests them and gains protein.
Because both organisms benefit, the relationship is mutualistic.
Mutualism is a type of symbiosis, meaning a close living relationship between two species.
The relationship is not saprophytic, because saprophytes feed only on dead organic matter.
It is not parasitic, because the bacteria do not harm the ruminant.
It is not heterotrophic, since heterotrophy describes a mode of nutrition, not a species interaction.
Answer:C. symbiotic