The Sahel stretches across Africa, about 15 degrees north of the equator. Satellite measurements of vegetation reveal it as a transition zone between the sands of the Sahara and the jungles of the Congo. This map shows vegetation in the final two weeks of June 2005, near the end of the dry season in the Sahel. Dark green indicates dense vegetation, while light green and beige indicate sparse vegetation and barren land.
When we think of desertification, we first think about prolonged drought conditions. Desertification can also be the result of degradation of the soil in an area as the most recent definition includes the permanent loss of fertility in an area. All of the choices below result in soil degradation leading to desertification EXCEPT
A) The buildup of salts in irrigated soils due to evaporation.
B) The presence of rocky fields that have been tilled but not planted.
C) Overfarming or drought can change the soil so that rain no longer penetrates.
D) Deforestation results in erosion: nutrient-rich top soil blows or washes away.

Scientific thinking: what clues about biology might road kill provide?

Ryan rears sheep for their wool. recently the quantity of wool that ryan gets has diminished. this is because the new sheep are not that wooly. ryan should add which nutrient to their feed so that the sheep becomes more wooly? a. cornb. ironc. cottonseedd. vitamin a

Rease is an enzyme used by plants to break down urea (a nitrogen-containing compound) into carbon dioxide and ammonia. urease urea > > > carbon dioxide and ammonia ammonia is broken down by plants into a nitrogen source plants need to grow. thus, plants could not use urea as a nitrogen source unless it was first converted to ammonia. in soybean plants there are two different kinds of urease, one produced in the seeds and the other produced in the leaves of the plant. three types of soybean plants were used in a set of experiments: normal soybeans and two mutant strains, one lacking the urease in the seeds only (strain 1) and one lacking urease in the leaves only (strain 2). experiment 1 separate areas in a field were planted with normal, strain 1, and strain 2 soybeans. all types of soybeans appeared to grow, flower, and produce seeds equally well. there were no externally detectable differences among the strains. experiment 2 small pieces of plant leaves of equal weight were obtained from each type of soybean plant and separately placed on media in culture dishes. tissue growing in this way will become an unorganized clump of cells referred to as callus. to provide a controlled nitrogen source, half the tissue samples of each type were placed on media containing urea, and the other half of the samples were placed on media containing ammonia. after 30 days, the weight gain for each of the callus samples was determined. results are shown in the table below.