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The Biosphere The Zone of Life Getting the terms right Getting the terms right 2 The Zone of Life • The biosphere is that part of the Earth that can support life. It is, relatively, thinner than the shell of an egg. • Is, first of all, very narrow about five miles from top to bottom. • It is made up of several component parts—all of which host life forms of some sort: the atmosphere, the hydrosphere, the lithosphere and, the terrasphere. • Air, water, rock and land. The Component Parts • The Biosphere is made up of many distinct parts called Ecosystems • They each represent the most stable and efficient use of energy in that particular place on the globe. • They have evolved into this balance over a long time, and are capable of adjusting if the circumstances of energy adjust. But… • It is the interaction of all the elements that makes up the Biosphere, not just the total. • Which is one reason most religions stress harmony not adversity. Ecosystems • As we said, the world is divided into broad, stable zones of distinctive fauna and flora called Ecosystems. The Three Characteristics • We normally evaluate any ecosystem by three different parameters 1. Productivity 2. Diversity 3. Resilience Productivity • Any measure of productivity is always a measure of output versus input. • We measure the productivity of an ecosystem by the weight of biological (living) material it supports. • However, we often distort this by asking what weight of useful material does it support? But… • As I said, we tend to measure productivity in terms of useful energy, ie how much food can this place produce. • In that context, the temperate areas do better, but at the cost of diversity. • This has been achieved by massive modification of the natural systems. 2. Diversity • Nature builds diversity into everything. • Every plant, even of the same species, is genetically slightly different from its neighbors. • This is a survival mechanism • If they were all the same, and there was a virus, they would all die • Indeed, lack of diversity is rare—think of identical twins 2. Diversity • In fact, when you think about it, it is remarkable that, given there are six billion people on earth, and we all have two eyes, one nose etc., we can pick out someone in a crowd we have not seen for years • And avoid them. 2. Diversity • Since we discovered agriculture 10,000 years ago, we have been waging war on natural diversity. • We plant miles of the same crop • And now we clone them, so there is no diversity at all. Diversity • Biologists are not completely sure how many different species live on the Earth. Estimates of how many species exist on the Earth range from low of 2 million to high of about 100 million. To date, about 2.1 million species have been classified, primarily in the habitats of the middle latitudes. Most of the unclassified species on this planet are invertebrates. This group of organisms includes insects, spiders, mollusks, sponges, flatworms, starfish, urchins, earthworms, and crustaceans. These species are often difficult to find and identify because of their small size and the fact that they live in habitats that are difficult to explore. In the tropical rain forest, the cataloging of species has been quite limited because of this later reason. Scientists estimate that this single biome may contain 50 to 90 % of the Earth's biodiversity. Diversity • The more species there are, then the better Nature is able to cope with change • But Diversity is also associated with competition as species may evolve to the point where they are struggling to fill the same space. Which led to the Survival of the Fittest, not strongest. 3.Resilience • Which means ability to withstand abuse and bounce back. • Over the millennia evolution has allowed Nature to reach a point where it copes with occasional extreme events • But we throw things at Nature that it has never seen before, and in quantities, and at a speed, the cycles cannot handle. 3.Resilience • • So, keep up with the reading assignments that you are Think, for instance, if you grow so only familiar with the terms. You cloned, or genetically-modified crops, need to spend a lot of time the going website because I and they fail, where arewith you to find the original strains?consider that part of the teaching and not just They will have become “homework.” extinct.