What is Darwin's theory of evolution?
In his theory of natural selection, which is discussed in greater detail later, Charles Darwin suggested that “ survival of the fittest ” was the basis for organic evolution (the change of living things with time). Evolution itself is a biological phenomenon common to all living things, even though it has led to their differences. Evidence to support the theory of evolution has come primarily from the fossil record, from comparative studies of structure and function, from studies of embryological development, and from studies of DNA and RNA (ribonucleic acid).
Why is it important to understand the biology of organisms?
To better understand the physiology of organisms, researchers study the tissues and organs of which organisms are composed. Key to that work is the ability to maintain and grow cells in vitro (“in glass”), otherwise known as tissue culture.
Why did biologists use the electron microscope?
Biologists once depended on the light microscope to study the morphology of cells found in higher plants and animals. The functioning of cells in unicellular and in multicellular organisms was then postulated from observation of the structure; the discovery of the chloroplastids in the cell, for example, led to the investigation of the process of photosynthesis. With the invention of the electron microscope, the fine organization of the plastids could be used for further quantitative studies of the different parts of that process.
How many species are there in the world?
The total number of extant animal and plant species is estimated at between roughly 5 million and 10 million; about 1.5 million of those species have been described by scientists. The use of classification as a means of producing some kind of order out of the staggering number of different types of organisms appeared as early as the book of Genesis —with references to cattle, beasts, fowl, creeping things, trees, and so on. The first scientific attempt at classification, however, is attributed to the Greek philosopher Aristotle, who tried to establish a system that would indicate the relationship of all things to each other. He arranged everything along a scale, or “ladder of nature,” with nonliving things at the bottom; plants were placed below animals, and humankind was at the top. Other schemes that have been used for grouping species include large anatomical similarities, such as wings or fins, which indicate a natural relationship, and also similarities in reproductive structures.
What are some examples of advances in tissue culture?
For example, many experiments have been directed toward achieving a deeper understanding of biological differentiation, particularly of the factors that control differentiation. Crucial to those studies was the development in the late 20th century of tissue culture methods that allowed for the growth of mammalian embryonic stem cells —and ultimately human embryonic stem cells—on culture plates.
What are the three types of natural selection?
Stabilizing selection (left column) acts against phenotypes at both extremes of the distribution, favouring the multiplication of intermediate phenotypes. Directional selection (centre column) acts against only one extreme of phenotypes, causing a shift in distribution toward the other extreme. Diversifying selection (right column) acts against intermediate phenotypes, creating a split in distribution toward each extreme.
What is the basis of taxonomy?
Taxonomy has been based on two major assumptions: one is that similar body construction can be used as a criterion for a classification grouping; the other is that, in addition to structural similarities, evolutionary and molecular relationships between organisms can be used as a means for determining classification.
What is evolution biology?
Evolutionary biology is the study of the history of life and the processes that lead to its diversity. Based on principles of adaptation, chance, and history, evolutionary biology seeks to explain all the characteristics of organisms, and, therefore, occupies a central position in the biological sciences.
Why is evolution important in biology?
Evolutionary biology plays a central role in the complexity of biological systems. Evolution is the source of biocomplexity. The continued and enhanced support of this field is critical to maximizing the nation's research progress in both basic and applied arenas. In terms of societal needs for the twenty-first century, the time to make the investment in evolutionary biology is now, while there is still time either to change current trends or to better prepare us to deal with their consequences. Current and projected population levels will result in increasing environmental impacts, increasing pressure on food production, ever greater challenges to biological diversity, and enhanced opportunities for the emergence of new diseases. A healthy scientific base in evolutionary biology is an essential element in preparing us to address these issues. Evolutionary biology must be at the heart of the nation's research agenda in biology, just as it is at the heart of the field of biology.
Why is it important for evolutionary biologists to communicate scientific advances?
In so doing, the foundations are laid for better public understanding of science as well as a stronger policy base for support of science itself.
How long has evolution been around?
Evolutionary biology has unequivocally established that all organisms evolved from a common ancestor over the last 3.5 billion years ; it has documented many specific events in evolutionary history; and it has developed a well-validated theory of the genetic, developmental, and ecological mechanisms of evolutionary change. The methods, concepts, and perspectives of evolutionary biology have made and will continue to make important contributions to other biological disciplines, such as molecular and developmental biology, physiology, and ecology, as well as to other basic sciences, such as psychology, anthropology, and computer science.
How are natural products useful?
Many thousands of natural products are used in medicine, food production and processing, cosmetics, biotechnology, pest control, and industry , but millions of other potentially useful natural products have yet to be screened or even discovered. Evolutionary principles allow a targeted search by predicting adaptations to environmental selection pressures and by identifying organisms related to those that have already yielded useful natural products. Exploration of related species also has made it possible to develop natural products from more accessible relatives of rare species in which natural products have been found, as occurred when the rare and endangered Pacific yew was found to contain a substance that led to development of a drug (tamoxifen) useful in treating breast cancer.
Why are cheetahs so low in genetic diversity?
CONSERVATION GENETICS. Evolutionary analysis reveals extremely low levels of genetic diversity among living cheetah, likely due to a dramatic population decline —and associated inbreeding—thousands of years ago. This hinders the cheetah's ability to reproduce successfully, which threatens the species' survival. Such information is being used to develop management recommendations for this endangered species.
Who established the foundations of evolutionary theory?
EVOLUTION BY NATURAL SELECTION. Nineteenth-century biologists Charles Darwin and Alfred Russell Wallace established the foundations for evolutionary theory.
