Chptr 32 Part 2

Legumes, such as beans or peas _.

• Form mutualistic associations with nitrogen-fixing bacteria.

• Form mycorrhizal associations to increase nitrogen fixation in the soil.

• Form parasitic relationships with other photosynthetic plants.

• Fix N2 from the atmosphere in their leaves.

Legumes are frequently grown in rotation with primary field crops. What is the benefit of this practice?

• A greater amount of the primary crop can be harvested each year.

• The legumes' symbiotic nitrogen-fixing bacteria add nitrogen to the soil.

• Soil erosion is reduced by frequent plowing.

• Legumes decrease the amount of organic material in the soil.

Much research is being done to increase the nitrogen-fixing ability of plants with root nodules. Why is this an important goal for agricultural researchers?

• Decreasing the size of nodules will allow plants to fix more nitrogen into their own molecules.

• Nitrogen is an essential component of the amino acids used to form protein.

• Increasing the nitrogen-fixing ability of plants will allow them to make better use of nitrogen fertilizers.

• Removing the bacteria from the root nodules will allow more fixed nitrogen to be available to the plants.

Carnivorous plants are more likely to be found in acid bogs because _.

• Organic matter decays so slowly there.

• Acid soil inhibits growth of plant roots.

• Acid rain damages leaves and stems.

• Mycorrhizal growth is inhibited.

Carnivory in plants is primarily an adaptation for _.

• Growing in soil poor in organic material.

• Growing in soil poor in usable nitrogen.

• Obtaining supplemental carbon for photosynthesis.

• Discouraging herbivorous insects.

An example of an organism that parasitizes a host plant is _.

• A mycorrhizal fungus.

• Nitrogen-fixing bacteria in root nodules.

• A Venus flytrap.

• Mistletoe.

What is most likely to be an epiphyte?

• A plant growing on the branches of another plant.

• A plant that captures insects.

• A plant with a very deep root system.

• A plant that parasitizes another plant.

A peanut farmer decides that she can make more money growing cotton and so plants her fields with cotton. The terrific yield of her fields is so encouraging that she continues to plant cotton for several more years, but each year her cotton yield decreases. What advice could you give her to increase her yield?

• Use a little less fertilizer each year since the soil is becoming overfertilized.

• Plant peanuts in alternate years since this crop rotation will provide extra nitrogen to the soil.

• Leave fields unplanted in alternate years so soil can recover.

• Plant a different crop every year since different crops deplete different soil nutrients.

A small seed may grow into a very large tree. As the tree grows, it adds a great deal of mass. Where does most of this mass come from?

• Air.

• Soil.

• Water.

• Sunlight.

The term carnivorous as applied to carnivorous plants is not considered accurate by some biologists because _.

• Carnivorous plants use insects for nitrogen and minerals; an organism would have to use insects as a source of energy and matter as well to be a carnivore.

• Carnivorous plants only use insects as pollinators and do not gain any nutrients from them.

• Carnivorous plants do not digest whole insects; an organism would have to digest whole insects to be considered a carnivore.

• Carnivorous plants do not move around; an organism must be able to move to be considered a carnivore.