There are countless plants, animals and microorganisms on land and sea. They make the world perfect: they transform sunlight into energy and supply it to other living things, and transform carbon and nitrogen between inorganic and organic forms, changing the landscape of the earth.
In some places and communities, there are hundreds of species, while in others, only a few species exist. For example, compared with high latitudes, the tropics are a paradise for species. Biologists try to explain why. The interaction between environment and organisms and the relationship between organisms play a key role in increasing or decreasing biodiversity. Human interference, predation and other food chain relationships also played a role. However, how do these factors and other forces work together to form diversity? This is still a mystery.
This is a challenge because we lack the most basic data. For example, we still don't know how many plants and animals there are on the earth. Researchers can't even begin to predict the types and numbers of microorganisms. Scientists who study evolution also lack a standard time scale, because evolution will last for several days to millions of years. Moreover, the changes within the same species will be almost the same as those between two similar species. We don't know what kind of genetic changes will lead to the emergence of a new species, and what is the real impact of genes on speciation.
Revealing the causes of diversity requires comprehensive interdisciplinary cooperation, including paleontological tips, field trips, laboratory work, genome comparison and effective data analysis. Some large-scale projects, such as the United Nations Millennium Project and the global genetic identification of marine microorganisms, will increase the basic data, but these are far from enough. This will help to predict how one species will split into two species. A new discipline, Evolutionary Developmental Biology (evo-devo), has emerged to study the role of genes in development and evolution. All these efforts still have a long way to go in clarifying the history of life.
Paleontologists have made some achievements in tracking the distribution and aggregation of many species in the past 1000 years. They found that geographical distribution plays an important role in speciation. Further research will continue to reveal a wide range of species distribution patterns, which may bring hope for clarifying the causes of mass extinction and studying the role of these disasters in the evolution of new species.
Through the field investigation of plants and animals, researchers have known that habitats can affect phenotypes and behaviors, especially sexual selection, by accelerating or slowing down speciation. Evolutionary biologists have also found that speciation can be interrupted, for example, when separated populations recombine, the genome will be homogenized (otherwise it will differentiate). Molecular forces, such as low mutation rate or meiosis drive, in which specific alleles are more likely to be passed from parents to offspring, affecting the speed of speciation.
In some cases, the diversity within the ecosystem will change: the species diversity at the edge of the ecosystem is sometimes lower than that in the middle.
How do these factors interact in different ways for different biological groups? The research of evolutionary biologists has just begun. The task is grim: it is very important to clarify the reasons for the formation of diversity for understanding the nature of species extinction that is happening on the earth and finding ways to alleviate it.