Cellulose and lignin are the two substances that make up the hard, permanent, and woody parts of plants these materials cannot be digested by most soil animals. They extract only the easily-assimilated substances from their food: proteins, sugars and other simple carbohydrates and fats. Primary decomposers are unable to digest the entire leaf. They spend most of their time chewing on the thick reserve of moist leaves contacting the forest floor. Inhabitants of leaf litter reside close to the surface and so must be able to experience exposure to dryer air and light for short times without damage. These cysts may endure long periods of severe freezing and sometimes temperatures of over 150 degree F. Some single-cell animals and roundworms are capable of surviving stress by encysting themselves, forming a little “seed” that preserves their genetic material and enough food to reactivate it, coming back to life when conditions improve.
So we see another reason why a thin mulch that preserves surface moisture can greatly increase the beneficial population of soil animals. When faced with desiccation they retreat deeper into the soil if there is oxygen and pore spaces large enough to move about. Soil animals consequently have not developed the ability to conserve their body moisture and are speedily killed by dry conditions. The soil environment is generally quite moist, and even when the soil seems dry the relative humidity of soil air usually approaches 100 percent. Where soil is airless due to compaction, poor drainage, or large proportions of very fine clay, soil animals are few in number. Except for a few microorganisms, soil animals breathe oxygen just like other living things and so are dependent on an adequate air supply. That’s why leaving bare earth exposed to the hot summer sun often slows plant growth and why many thoughtful composters either put down a thin mulch in summer or try to rapidly establish a cooling leaf canopy to shade raised beds. Consequently, soil animals are generally intolerant to sudden temperature changes and may not function well over a very wide range. Smith’s “The Organic Way of Life.”Ĭompared to the atmosphere, soil is a place where temperature fluctuations are small and slow. Once I saw that the parabola was running away from the vertex faster than the parabola, I’d know the answer isn’t C and go for A.Questions 1–10 are based on the following passage. In fact, it’s going 1 across, 4 up, so we know its leading coefficient is 4 (it goes up 4 steps instead of 1).īut I wouldn’t even do that math. That’s what all parabolas with leading coefficient of 1 will look like.īecause the parabola in the question goes straight from vertex (3, 1) to (4, 5), it’s running away from the vertex faster than 1 across, 1 up.
Importantly, the first integer steps from the vertex are 1 across, 1 up. Remember that your standard parabola looks like this:
To differentiate between that leading coefficient being equal to 4 or 1, you need to remember what the leading coefficient tells you: how fast the parabola runs away from the vertex. Because the vertex is (3, 1), you need to see. Is there a quick way to solve from there without plugging in values from the graph?
Could you suggest a shortcut or fast way to solve this? All the answers are written in vertex form, so we can quickly eliminate two of them, as the coordinates of the vertex, as indicated by the graph provided, must be (3,1).
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