What is an ecosystem ?

An ecosystem is a natural area containing living organisms that react to each other and to their environment and plants,

it is a biological environment consisting of all the organisms living in a particular area, as well as all the nonliving, physical components of the environment with which the organisms interact, such as air, soil, water and sunlight. It is all the organisms in a given area, along with the nonliving (abiotic factors with which they interact; a biological community and its physical environment.

Within each ecosystem, there are habitats which may also vary in size. A habitat is the place where a population lives. A population is a group of living organisms of the same kind living in the same place at the same time. All of the populations interact and form a community. The community of living things interacts with the non-living world around it to form the ecosystem. The habitat must supply the needs of organisms, such as food, water, temperature, oxygen, and minerals. If the population's needs are not met, it will move to a better habitat. Two different populations can not occupy the same niche at the same time, however. So the processes ofcompetition, predation, cooperation, and symbiosis occur.

BIOLOGY

Biology

Biology, the science of life. The term was introduced in Germany in 1800 and popularized by the French naturalist Jean-Baptiste de Lamarck as a means of encompassing the growing number of disciplines involved with the study of living forms. The unifying concept of biology received its greatest stimulus from the English zoologist Thomas Henry Huxley, who was also an important educator. Huxley insisted that the conventional segregation of zoology and botany was intellectually meaningless and that all living things should be studied in an integrated way. Huxley’s approach to the study of biology is even more cogent today, because scientists now realize that many lower organisms are neither plants nor animals (see Prokaryote; Protista). The limits of the science, however, have always been difficult to determine, and as the scope of biology has shifted over the years, its subject areas have been changed and reorganized. Today biology is subdivided into hierarchies based on the molecule, the cell, the organism, and the population.

Molecular biology, which spans biophysics and biochemistry, has made the most fundamental contributions to modern biology. Much is now known about the structure and action of nucleic acids and protein, the key molecules of all living matter. The discovery of the mechanism of heredity was a major breakthrough in modern science. Another important advance was in understanding how molecules conduct metabolism, that is, how they process the energy needed to sustain life.

Cellular biology is closely linked with molecular biology. To understand the functions of the cell—the basic structural unit of living matter—cell biologists study its components on the molecular level. Organismal biology, in turn, is related to cellular biology, because the life functions of multicellular organisms are governed by the activities and interactions of their cellular components. The study of organisms includes their growth and development (developmental biology) and how they function (physiology). Particularly important are investigations of the brain and nervous system (neurophysiology) and animal behavior (ethology).

Population biology became firmly established as a major subdivision of biological studies in the 1970s. Central to this field is evolutionary biology, in which the contributions of Charles Darwin have been fully appreciated after a long period of neglect. Population genetics, the study of gene changes in populations, and ecology, the study of populations in their natural habitats, have been established subject areas since the 1930s. These two fields were combined in the 1960s to form a rapidly developing new discipline often called, simply, population biology. Closely associated is a new development in animal-behavior studies called sociobiology, which focuses on the genetic contribution to social interactions among animal populations.

Biology also includes the study of humans at the molecular, cellular, and organismal levels. If the focus of investigation is the application of biological knowledge to human health, the study is often termed biomedicine. Human populations are by convention not considered within the province of biology; instead, they are the subject of anthropology and the various social sciences. The boundaries and subdivisions of biology, however, are as fluid today as they have always been, and further shifts may be expected.

See Animal; Animal Behavior; Botany; Cell; Classification; Development; Ecology; Evolution; Genetics; Heredity; Life; Medicine; Metabolism; Plant; Reproduction; Respiration; Zoology.

Contributed By:

John Tyler Bonner

Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.

What is Biology?

Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy.^[1] Biology is a vast subject containing many subdivisions, topics, and disciplines

Branches of the study of life(BIOLOGY)

Aerobiology — the study of airborne organic particles

Agriculture — the study of producing crops from the land, with an emphasis on practical applications

Anatomy — the study of form and function, in plants, animals, and other organisms, or specifically in humans

Astrobiology — the study of evolution, distribution, and future of life in the universe—also known as exobiology, exopaleontology, and bioastronomy

Biochemistry — the study of the chemical reactions required for life to exist and function, usually a focus on the cellular level

Bioengineering — the study of biology through the means of engineering with an emphasis on applied knowledge and especially related to biotechnology

Bioinformatics — the use of information technology for the study, collection, and storage of genomic and other biological data

Biomathematics or Mathematical Biology — the quantitative or mathematical study of biological processes, with an emphasis on modeling

Biomechanics — often considered a branch of medicine, the study of the mechanics of living beings, with an emphasis on applied use through prosthetics or orthotics

Biomedical research — the study of the human body in health and disease

Biophysics — the study of biological processes through physics, by applying the theories and methods traditionally used in the physical sciences

Biotechnology — a new and sometimes controversial branch of biology that studies the manipulation of living matter, including genetic modification and synthetic biology

Building biology — the study of the indoor living environment

Botany — the study of plants

Cell biology — the study of the cell as a complete unit, and the molecular and chemical interactions that occur within a living cell

Conservation Biology — the study of the preservation, protection, or restoration of the natural environment, natural ecosystems, vegetation, and wildlife

Cryobiology — the study of the effects of lower than normally preferred temperatures on living beings.

Developmental biology — the study of the processes through which an organism forms, from zygote to full structure

Ecology — the study of the interactions of living organisms with one another and with the non-living elements of their environment

Embryology — the study of the development of embryo (from fecundation to birth). See also topobiology.

Entomology — the study of insects

Environmental Biology — the study of the natural world, as a whole or in a particular area, especially as affected by human activity

Epidemiology — a major component of public health research, studying factors affecting the health of populations

Ethology — the study of animal behavior

Evolutionary Biology — the study of the origin and descent of species over time

Genetics — the study of genes and heredity

Herpetology — the study of reptiles and amphibians

Histology — the study of cells and tissues, a microscopic branch of anatomy

Ichthyology — the study of fish

Integrative biology — the study of whole organisms

Limnology — the study of inland waters

Mammalogy — the study of mammals

Marine Biology — the study of ocean ecosystems, plants, animals, and other living beings

Microbiology — the study of microscopic organisms (microorganisms) and their interactions with other living things

Molecular Biology — the study of biology and biological functions at the molecular level, some cross over with biochemistry

Mycology — the study of fungi

Neurobiology — the study of the nervous system, including anatomy, physiology and pathology

Oceanography — the study of the ocean, including ocean life, environment, geography, weather, and other aspects influencing the ocean

Oncology — the study of cancer processes, including virus or mutation oncogenesis, angiogenesis and tissues remoldings

Ornithology — the study of birds

Population biology — the study of groups of conspecific organisms, including

• Population ecology — the study of how population dynamics and extinction
• Population genetics — the study of changes in gene frequencies in populations of organisms

Paleontology — the study of fossils and sometimes geographic evidence of prehistoric life

Pathobiology or pathology — the study of diseases, and the causes, processes, nature, and development of disease

Parasitology — the study of parasites and parasitism

Pharmacology — the study and practical application of preparation, use, and effects of drugs and synthetic medicines

Physiology — the study of the functioning of living organisms and the organs and parts of living organisms

Phytopathology — the study of plant diseases (also called Plant Pathology)

Psychobiology — the study of the biological bases of psychology

Sociobiology — the study of the biological bases of sociology

Structural biology — a branch of molecular biology, biochemistry, and biophysics concerned with the molecular structure of biological macromolecules

Virology — the study of viruses and some other virus-like agents

Zoology — the study of animals, including classification, physiology, development, and behavior (See also Entomology, Ethology, Herpetology, Ichthyology, Mammalogy, and Ornithology)

Its Early Beginnings

The Greek philosophers, voracious in their curiosity, look with interest at the range of living creatures, from the humblest plant to man himself. A Greek name is coined by a German naturalist in the early 19th century for this study of all physical aspects of natural life - biology, from bios(life) and logos(word or discourse). It is a subject with clear subdivisions, such as botany, zoology or anatomy. But all are concerned with living organisms.The earliest humans must have had and passed on knowledge about plants and animals to increase their chances of survival. This may have included knowledge of human and animal anatomy and aspects of animal behavior (such as migration patterns). However, the first major turning point in biological knowledge came with the Neolithic Revolution about 10,000 years ago. Humans first domesticated plants for farming, then livestock animals to accompany the resulting sedentary societies.^{The ancient cultures of Mesopotamia, Egypt, the Indian subcontinent, and China, among others, produced renowned surgeons and students of the natural sciences such as Susruta and Zhang Zhongjing, reflecting independent sophisticated systems of natural philosophy. However, the roots of modern biology are usually traced back to the secular tradition of ancient Greek philosophy.One of the oldest organised systems of medicine is known from Indian subcontinent in form of Ayurveda which originated around 1500 BC from Atharvaveda(one of the four most ancient books of Indian knowledge, wisdom and culture). Other ancient medical texts were produced by the Egyptian tradition, such as the Edwin Smith Papyrus. It is also known for developing the process of embalming, which was used for mummification, in order to preserve human remains and forestall decomposition. In ancient China, biological topics can be found dispersed across several different disciplines, including the work of herbologists, physicians, alchemists and philosophers. The Taoist tradition of Chinese alchemy, for example, can be considered part of the life sciences due to its emphasis on health (with the ultimate goal being the elixir of life). The system of classical Chinese medicine usually revolved around the theory of yin and yang, and the five phases. Taoist philosophers, such as Zhuangzi in the 4th century BC, also expressed ideas related to evolution, such as denying the fixity of biological species and speculating that species had developed differing attributes in response to differing environments.The ancient Indian Ayurveda tradition independently developed the concept of three humours, resembling that of the four humours of ancient Greek medicine, though the Ayurvedic system included further complications, such as the body being composed of five elements and seven basic tissues. Ayurvedic writers also classified living things into four categories based on the method of birth (from the womb, eggs, heat & moisture, and seeds) and explained the conception of a fetus in detail. They also made considerable advances in the field of surgery, often without the use of human dissection or animal vivisection. One of the earliest Ayurvedic treatises was the Sushruta Samhita, attributed to Sushruta in the 6th century BC. It was also an early materia medica, describing 700 medicinal plants, 64 preparations from mineral sources, and 57 preparations based on animal sources. The pre-Socratic philosophers asked many questions about life but produced little systematic knowledge of specifically biological interest—though the attempts of the atomists to explain life in purely physical terms would recur periodically through the history of biology. However, the medical theories ofHippocrates and his followers, especially humorism, had a lasting impact.The philosopher Aristotle was the most influential scholar of the living world from classical antiquity. Though his early work in natural philosophy was speculative, Aristotle's later biological writings were more empirical, focusing on biological causation and the diversity of life. He made countless observations of nature, especially the habits and attributes of plants and animals in the world around him, which he devoted considerable attention tocategorizing. In all, Aristotle classified 540 animal species, and dissected at least 50. He believed that intellectual purposes, formal causes, guided all natural processes.Aristotle, and nearly all Western scholars after him until the 18th century, believed that creatures were arranged in a graded scale of perfection rising from plants on up to humans: the scala naturae or Great Chain of Being. Aristotle's successor at the Lyceum, Theophrastus, wrote a series of books on botany—the History of Plants—which survived as the most important contribution of antiquity to botany, even into the Middle Ages. Many of Theophrastus' names survive into modern times, such as carpos for fruit, and pericarpion for seed vessel. Pliny the Elder was also known for his knowledge of plants and nature, and was the most prolific compiler of zoological descriptions.A few scholars in the Hellenistic period under the Ptolemies—particularly Herophilus of Chalcedon and Erasistratus of Chios—amended Aristotle's physiological work, even performing experimental dissections and vivisections. Claudius Galen became the most important authority on medicine and anatomy. Though a few ancient atomists such as Lucretius challenged the teleological Aristotelian viewpoint that all aspects of life are the result of design or purpose, teleology (and after the rise of Christianity, natural theology) would remain central to biological thought essentially until the 18th and 19th centuries. Ernst W. Mayrargued that "Nothing of any real consequence happened in biology after Lucretius and Galen until the Renaissance. The ideas of the Greek traditions of natural history and medicine survived, but they were generally taken unquestioningly in medieval Europe.}