Changing ways of life guided reading answers

#Changing ways of life guided reading answers how to

Since there is no unequivocal definition of life, most current definitions in biology are descriptive. More simply, life is, 'matter that can reproduce itself and evolve as survival dictates'. One definition seems to be favored by NASA: 'a self-sustaining chemical system capable of Darwinian evolution'. As many as 123 definitions of life have been compiled. Legal definitions of life have also been described and debated, though these generally focus on the decision to declare a human dead, and the legal ramifications of this decision.

#Changing ways of life guided reading answers how to

Philosophical definitions of life have also been put forward, with similar difficulties on how to distinguish living things from the non-living. This is complicated by a lack of knowledge of the characteristics of living entities, if any, that may have developed outside of Earth. This is partially because life is a process, not a substance. The definition of life has long been a challenge for scientists and philosophers. Fossils are the preserved remains or traces of organisms. Extinction is the term describing the dying-out of a group or taxon, usually a species. Artificial life is a computer simulation or human-made reconstruction of any aspect of life, which is often used to examine systems related to natural life.Дeath is the permanent termination of all biological processes which sustain an organism, and as such, is the end of its life. Though currently only known on Earth, life need not be restricted to it, and many scientists speculate in the existence of extraterrestrial life. Eventually new groups and categories of life were discovered, such as cells and microorganisms, forcing significant revisions of the structure of relationships between living organisms. Later, Carl Linnaeus introduced his system of binomial nomenclature for the classification of species. Aristotle is considered to be the first person to classify organisms. In the past, there have been many attempts to define what is meant by 'life' through obsolete concepts such as Odic force, hylomorphism, spontaneous generation and vitalism, that have now been disproved by biological discoveries. Cells reproduce through a process of cell division, in which the parent cell divides into two or more daughter cells. There are two kinds of cells, prokaryotic and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many biomolecules such as proteins and nucleic acids. The cell is considered the structural and functional unit of life. Some microorganisms, called extremophiles, thrive in physically or geochemically extreme environments that are detrimental to most other life on Earth. Since its primordial beginnings, life on Earth has changed its environment on a geologic time scale, but it has also adapted to survive in most ecosystems and conditions. Complex organic molecules occur in the Solar System and in interstellar space, and these molecules may have provided starting material for the development of life on Earth. The classic 1952 MillerвЂ“Urey experiment and similar research demonstrated that most amino acids, the chemical constituents of the proteins used in all living organisms, can be synthesized from inorganic compounds under conditions intended to replicate those of the early Earth. Life on Earth is probably descended from an RNA world, although RNA-based life may not have been the first life to have existed. The earliest known life forms are microfossils of bacteria. Life on Earth first appeared as early as 4.28 billion years ago, soon after ocean formation 4.41 billion years ago, and not long after the formation of Earth 4.54 billion years ago. The prevailing scientific hypothesis is that the transition from non-living to living entities was not a single event, but a gradual process of increasing complexity.

Other definitions sometimes include non-cellular life forms such as viruses and viroids.ДЄbiogenesis is the natural process of life arising from non-living matter, such as simple organic compounds. One popular definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli, reproduce and evolve.

There is currently no consensus regarding the definition of life. Biology is the science that studies life. Various forms of life exist, such as plants, animals, fungi, protists, archaea, and bacteria. Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased (they have died) or because they never had such functions and are classified as inanimate.