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①American remove dams
There are a lot of dams all over America.These dams have taken very crucial roles.Some dams divert the flow of river water into a pipeline, canal, or channel. Others raise the level of inland waterways to make them navigable by ships and barges.The Americans build dams over streams,rivers and estuaries.They are used to prevent flood,create electricity or store for daily life and irrigate.Dams are built kind of for the same reasons why reservoirs are built.They can provide water for surrounding people and offer water for irrigation.The gap between terrains can make dams provide electricity.This is also an important device for preventing flood.This is a necessary part of canal system.Those are the reasons why the Americans build so many dams.In America,gaps between terrains are big so that they build a lot of dams in order to make electricity.
Despite the various benefits dams could offer to mankind, their potential harms cannot be ignored.For the following reasons,the Americans remove a lot of dams.Building a dam changes the ecology of the surrounding area and destructs the natural habitat of many animals, the most affected of which are fish that depend on free-flowing water to live. Dams also alter the water temperatures and microhabitats downstream. Water-released from behind dams usually comes from water close to the bottom of the reservoirs, where little sunlight penetrates. This frigid water significantly lowers the temperatures of sun-warmed shallows downstream, rendering them unfit for certain kinds of fish and other wildlife.Tominimize the adverse influence of dams, the U.S. government launched a series of measures to protect salmon and other migratory fish species.Some dams began to incorporate a fish pass to allow fish a chance to swim around the dam and reach upstream spawning grounds.Fish passes called fish ladders comprise a series of small pools arranged like stair steps. Each pool is slightly higher than the previous one.In order to protect the ecosystem,the US government decided to remove a lot of dams.
The Americans build dams to take the edge of resources,but finally give up because of the harm to environment.This is a thing that worths deep thought.
②Coral reefs
Generally, there exists competition among animals, maintaining the quantity as well as survival of these animals. And it is well acknowledged that the living environment in the sea is more complex than that on land, so the relationship of organisms' competition in the sea certainly possesses more complication. The huge number of coral reefs can even influence the environment surrounding them, and normally, in both the shallow level and the deep level, there all exist coral reefs. Owing to the fact that the kinds of coral reefs are distinguished and various, the competitive relationship in the sea is complicated and unpredictable, including the competition among the same coral reef and the competition among the individuals from different coral reefs, usually between the shallow ones and the deep ones.
Initially, the composition of coral reefs, which always consists of coral bones accumulated for more than several hundred years or even thousand years during the process of development, and all of these coral reefs need to depend on the other organisms to survive in the fierce environment. The coral reefs, considered as the animals with weak adaptability, usually have the high standard for the living environment. The temperature and the salinity cannot be too high or low. With the consideration of being difficult to obtain affluent food in the sea, the survival of coral reefs is intractable.
We all know that if the sunshine wants to reach the bottom of the sea, it should penetrate those plants living in the shallow level of the sea and be obtained by coral reefs in deep levels. So from some degree, the coral reefs growing up in the shallow ones can be considered as the obstacle and competitors for those in the deep levels. And due to the fact that the sunshine is the basic energy for plants, not only for coral reefs but also for predators or food for the coral reefs. The number of units in a certain coral reef is also numerous, the individuals among them also compete with each other for food as well as suitable living environment.
Every phenomenon in ecosystem possesses its reason, the competition among these organisms can be utilized to control the dimensions of all coral reefs. It is not difficult for us to imagine that when the number of individuals in a group decline to a minimum number, the competition among individuals will be weak in order to let the quantity return to normal level, which can be called as express lift. In the other hand, if the total number of individuals in a coral reefs exceeds a maximum number, the speed of expanding the dimension will be slow, and sometimes it also has the decrease.
③Social and Solitary animal
Sociality refers to the extent of organization of their social behavior. The levels of sociality include eusocial, pre-social (solitary but social), subsocial, and par-asocial (including communal, quasi-social, and semi-social).
Animal social behavior and organization is studied in comparative psychology, ethology, sociobiology, behavioral ecology and computer science (artificial intelligence).
Solitary animals are those that spend a majority of their lives without others of their species, with possible exceptions for mating and raising their young. The antonym to a solitary animal is a social animal.
Animals that are solitary are often territorial and do not like the company of another animal in their territory and especially an animal of their own kind. This could be due to competition between rivals for the opportunity to mate or over territory, or it could be a more suitable way to live in the environment. When two of the same species meet they often show aggressive displays to try to chase off the other, but if neither of the two backs down a brawl can escalate. In some species these fights can end in the death of one or both animals.
The few times a solitary animal is with another of its kind is when it is caring for its offspring or when it is ready to mate. Nevertheless, when an offspring becomes independent the youngster will either leave on its own or be rejected by its parent.
This trait could be because the parent no longer tolerates the presence of another of its kind or it is ready to mate again and cannot care for both its first offspring and a newborn. During a time of mating, a solitary animal tries to find a mate, and once the act is completed, the animal may repeat the mating process several times and then resume its solitary lifestyle.
Tasmanian Devils are actually quite timid creatures when they come across a person. But when two Tasmanian Devils are introduced they become very aggressive and hostile towards each other.They live alone to avoid competition against its own species.
On the other hand, not all the animals choose to like alone.The antonym to a social animal is a solitary animal. Social animals are those animals which interact highly with other animals, usually of their own species (conspecifics), to the point of having a recognizable and distinct society. Many animals are social to the extent that mothers and offspring bond, and males and females interact to mate, but the term "social animal" is usually only applied when there is a level of social organization that goes beyond this, with permanent groups of adults living together, and relationships between individuals that endure from one encounter to another. The most commonly known example of a social animal is a domestic dog. In the case of social animals, it can be detrimental to their development to not have those social interactions, as they are crucial. These interactions and socializing will help to develop emotional stability and flexibility for the span of the animal's life.
