Which of the following is not a way that the government and citizens of Brazil is attempting to deal with the issue of deforestation?

O limits on the amount of land that can be cleared each year

O banning the clearing of land by companies based outside of Brazil

O research into how to maximize production of cleared land

O high fines on those who ignore limits land clearing

Animals, for the most part, ingest their food as large, complex molecules that must be broken down into smaller molecules (monomers) that can then be distributed throughout the body of every cell. This vital function is accpomplished by a series of specialized organs that comprise the digestive system. Representative digestive systems are shown in Figure 1.

Digestive System | Back to Top

Single-celled organisms can directly take in nutrients from their outside environment. Multicellular animals, with most of their cells removed from contact directly with the outside environment, have developed specialized structures for obtaining and breaking down their food. Animals depend on two processes: feeding and digestion.

Animals are heterotrophs, they must absorb nutrients or ingest food sources. Ingestive eaters, the majority of animals, use a mouth to ingest food. Absorptive feeders, such as tapeworms, live in a digestive system of another animal and absorb nutrients from that animal directly through their body wall. Filter feeders, such as oysters and mussels, collect small organisms and particles from the surrounding water. Substrate feeders, such as earthworms and termites, eat the material (dirt or wood) they burrow through. Fluid feeders, such as aphids, pierce the body of a plant or animal and withdraw fluids.

Figure 1. The digestive systems of representative animals. Images from Purves et al., Life: The Science of Biology, 4th Edition, by Sinauer Associates (www.sinauer.com) and WH Freeman (www.whfreeman.com), used with permission.