Dan, a renowned pedologist, visited two farms near his home town. Grape farm had depleted soils and a low crop production, while Fruit farm, having parcels with depleted soils in the past, established an agroforestry system starting a decade ago which helped stabilize soil and increase production. Which farm used more groundcover plants? Hint: Depleted soils can be protected from soil erosion by groundcover plants such as naturally growing grasses in agroforestry systems. These help to stabilise the soil as they increase cover compared to short-cycle cropping systems. Soil cover is a crucial factor in preventing erosion. Cleaner water through reduced nutrient and soil surface runoff can be a further advantage of agroforestry. The runoff can be reduced by decreasing its velocity and increasing infiltration into the soil. Compared to row-cropped fields nutrient uptake can be higher and reduce nutrient loss into streams.Further advantages concerning plant growth:
Ans: Fruit

Two friends had unprotected sex with their respective dates on the same night. Everything went fine for both of them. They later found out the bad news. Mike had been infected with HIV. Luckily enough Pete was healthy, he didn't get any diseases. Which friend had a virus that is transmitted by sexual contact? Hint: The Human Immunodeficiency Virus ( HIV ) is the virus that causes Acquired Immunodeficiency Syndrome ( AIDS ). Most researchers believe that the HIV originated in sub-Saharan Africa during the 20th century. HIV is transmitted by sexual contact and by contact with infected bodily fluids, such as blood, semen, breast milk, and vaginal secretions. It is also passed from mother to fetus. HIV is now a pandemic , with an estimated (as of 2008) 38.6 million people now living with the disease worldwide. It is estimated that AIDS has killed more than 25 million people since it was first recognized in 1981. For further information about HIV/AIDS, see the CDC (Centers for Disease Control and Prevention) web site at http://www.cdc.gov/hiv/resources/factsheets/ .
Ans: Mike

John is trying to figure out how the shape of an object affects how it reacts with other elements. For that, he chose two objects, both made of the same element - object A and object B. Object A has a larger surface area, but object B has smaller surface area. He let these objects to react with other reactants to see how the processes work. Would object B be more or less exposed to the reactants than object A? Hint: When a solid substance is involved in a chemical reaction, only the matter at the surface of the solid is exposed to other reactants. If a solid has more surface area, more of it is exposed and able to react. Therefore, increasing the surface area of solid reactants increases the reaction rate. Look at the hammer and nails pictured in the Figure below . Both are made of iron and will rust when the iron combines with oxygen in the air. However, the nails have a greater surface area, so they will rust faster.
Ans: less

Two politicians are proposing ideas they have about how to better serve the planet. Greg remarks that for too long the ozone layer has been a hindrance to progress and that scientists need to work to eliminate it. Mark scoffs at his opponent and says that the only real way to make progress is to make the ozone layer even stronger, not hurt it. Whose proposal will allow more ultraviolet light through the atmosphere? Hint: Above the troposphere, the atmosphere is usually divided into the stratosphere, mesosphere, and thermosphere. Each layer has a different lapse rate, defining the rate of change in temperature with height. Beyond these, the exosphere thins out into the magnetosphere, where the geomagnetic fields interact with the solar wind. Within the stratosphere is the ozone layer, a component that partially shields the surface from ultraviolet light and thus is important for life on Earth. The Karman line, defined as 100 km above Earth's surface, is a working definition for the boundary between the atmosphere and outer space.Thermal energy causes some of the molecules at the outer edge of the atmosphere to increase their velocity to the point where they can escape from Earth's gravity. This causes a slow but steady loss of the atmosphere into space. Because unfixed hydrogen has a low molecular mass, it can achieve escape velocity more readily, and it leaks into outer space at a greater rate than other gases. The leakage of hydrogen into space contributes to the shifting of Earth's atmosphere and surface from an initially reducing state to its current oxidizing one. Photosynthesis provided a source of free oxygen, but the loss of reducing agents such as hydrogen is thought to have been a necessary precondition for the widespread accumulation of oxygen in the atmosphere. Hence the ability of hydrogen to escape from the atmosphere may have influenced the nature of life that developed on Earth. In the current, oxygen-rich atmosphere most hydrogen is converted into water before it has an opportunity to escape. Instead, most of the hydrogen loss comes from the destruction of methane in the upper atmosphere.
Ans: Greg