FAQ: Biodiversity and Ecosystems
Question 1: What is meant by succession, and what factors are responsible for succession? Answer 1: Succession is the order in which an ecosystem becomes established. It is the process by which species within a community replace one another in a given ecosystem. Usually, the complexity of the communities increases as they are replaced. Succession is triggered by a disturbance (fire or storm) or newly created open areas (deforestation). Ecological succession has several levels including primary and secondary succession. Primary succession involves pioneer species, which are usually the first ones to colonize open areas. They are hardy species and include things like microbes, mosses, and lichens. Eventually, the pioneer species become replaced by climax species. Climax species only occur after a long period without disturbance. Climax species are usually long-lived and require a stable environment. Question 2: How can natural selection lead to the development of new species? What are the prerequisites and the limitations? Answer 2: Natural selection was first proposed by Charles Darwin in his book Origin of Species. Natural selection is the process by which certain gene combinations give an organism a certain advantage over the others in a population. This trait then becomes selected as the population continues to reproduce. For example, suppose a certain mouse can run faster than any of the other mice in a population. The mouse will have a better chance of outrunning predators and therefore will survive longer. Because this mouse can survive longer, he can reproduce longer and pass his "fast" genes to more mice. Eventually, most of the mice in the population will be faster. Speciation occurs when these selective advantages lead to an organism that can no longer reproduce with its original population. Think of how many bird species there are. They all evolved from the same ancestor over 200 million years ago, but yet they cannot interbreed. For speciation to occur, the organisms have to have reproductive isolation (either mechanically or geographically) and continued selective pressures. Question 3: Why does the introduction of a foreign species frequently have disruptive ecological results? Answer 3: Nonnative species often have disruptive effects because they have characteristics that allow them to out-compete native species. Often, introduced species are more aggressive and grow faster. Examples include kudzu ivy, zebra mussels, and African cichlid fishes. Nonnative species are sometimes introduced by accident in ballast water of ships and shipping containers. They also get introduced by the exotic pet trade. Many individuals get tired of their exotic pets and will simply let them go in their backyard or a nearby stream. Some of these discarded pets will be able to survive and reproduce creating a population in an area in which they never were present before. A current invasive species in the news is the snakehead fish that is eating up

native populations of freshwater fish in lakes along the East Coast. Question 4: What attributes influence the survival of a species? Answer 4: Survival of the fittest is the most definitive answer. This is an idea that was derived from Darwin’s work, which means that those organisms that can adapt to a changing environment will survive. An organism must change both structurally and behaviorally to adapt to rapidly changing environments. Question 5: How does loss of biodiversity undercut the ability of species, ecosystems, and agriculture to adapt to changing conditions? Answer 5: By decreasing biodiversity, the available gene pool decreases. Natural selection works on new gene combinations. If you limit the number of genes in a population, you are limiting the ability of natural selection to occur. This becomes extremely important in agriculture. For example, if you only grow one species of corn and an insect infestation wipes out all the corn plants, you are in trouble, but if you have a choice of different types of plants, you can grow several and increase your chances of having some viable crops. Question 6: What are the causes of the human population explosion? Answer 6: The most significant cause is medical advancements. Prior to the 1800s, the biggest enemy for the human population was disease. Diseases like smallpox, diphtheria, measles, and scarlet fever wiped out thousands of people and many children. Plagues such as the black plague, typhus, and cholera also killed many adults. In the 1800s, scientists figured out what caused disease and how it was spread. By the 1930s, penicillin was discovered, and the number of deaths decreased dramatically.