Theories and Laws of Science

What do mean by Theories and Laws of Science?

Observations and conclusions in science either develop or support existing information. A theory is an explanation of things or events based on many observations. A theory is not someone's opinion, nor is a theory a vague idea. Hypotheses that have been tested over and over again and cannot be shown to be false support theories. You have already read about the theory of spontaneous generation. Theories can be changed as new data uncover new information. Large amounts of data in science often show a trend. A scientific law based on these repeating data tells us how nature works. A law is a reliable description of nature based on many observations. In life science, you will learn about the laws of heredity. Laws may change as more information becomes known. Scientific methods help answer questions. Your questions may be as simple as "Where did I leave my house key?" or as complex as "What can we do about air pollution?" Will these methods guarantee that you will get an answer? Not always. Often they just lead you to more questions, but that is the work of science. 

How are the Scientists Developing Theorie?

Scientists use the word theory in two main ways. A "theory" is a proposed explanation for some natural phenomenon, often based on some general principle. Thus we speak of the principle first proposed by Newton as the "theory of gravity." Such theories often bring together concepts that were previously thought to be unrelated, and offer unified explanations of different phenomena. Newton's theory of gravity provided a single explanation for objects falling to the ground and the orbits of planets around the sun. "Theory" is also used to mean the body of interconnected concepts, supported by scientific reasoning and experimental evidence, that explains the facts in some area of study. Such a theory provides an indispensable framework for organizing a body of knowledge. For example, quantum theory in physics brings together a set of ideas about the nature of the universe, explains experimental facts, and serves as a guide to further questions and experiments. To a scientist, theories are the solid ground of science, that of which we are most certain. In contrast, to the general public, "theory" implies just the opposite—a lack of knowledge, or a guess. Not surprisingly, this difference often results in confusion. In this text, theory will always be used in its scientific sense, in reference to an accepted general principle or body of knowledge. To suggest, as many critics outside of science do, that evolution is "just a theory" is misleading. The hypothesis that evolution has occurred is an accepted scientific fact; it is supported by overwhelming evidence. Modern evolutionary theory is a complex body of ideas whose importance spreads far beyond explaining evolution; its ramifications permeate all areas of biology, and it provides the conceptual framework that unifies biology as a science.

Darwin's theory of evolution illustrates how science works.

Charles Darwin

Darwin's theory of evolution explains and describes how organisms on earth have changed over time and acquired a diversity of new forms. This famous theory provides a good example of how a scientist develops a hypothesis and how a scientific theory grows and wins acceptance. 

 Charles Robert Darwin (1809-1882) was an English naturalist who, after 30 years of study and observation, wrote one of the most famous and influential books of all time. This book, On the Origin of Species by Means of Natural Selection, or The Preservation of Favored Races in the Struggle for Life, created a sensation when it was published, and the ideas Darwin expressed in it have played a central role in the development of human thought ever since. 

 In Darwin's time, most people believed that the various kinds of organisms and their individual structures resulted from direct actions of the Creator (and to this day many people still believe this). Species were thought to be specially created and unchangeable, or immutable, over the course of time. In contrast to these views, a number of earlier philosophers had presented the view that living things must have changed during the history of life on earth. Darwin pro-posed a concept he called natural selection as a coherent, logical explanation for this process, and he brought his ideas to wide public attention. 

 Darwin's book, as its title indicates, presented a conclusion that differed sharply from conventional wisdom. Al-though his theory did not directly challenge the existence of a Divine Creator, Darwin argued that the operation of natural laws produced change over time, or evolution. These views put Darwin at odds with most people of his day, who believed in a literal interpretation of the Bible and thus accepted the idea of a fixed and constant world, largely unchanged since it was created by God. 

 The story of Darwin and his theory begins in 1831, when he was 22 years old. On the recommendation of one of his professors at Cambridge University, he was selected to serve as naturalist on a five-year navigational mapping expedition around the coasts of South America, aboard H.M.S. Beagle. During this long voyage, Darwin had the chance to study a wide variety of plants and animals on continents and islands and in distant seas. He was able to explore the biological richness of the tropical forests, examine the extraordinary fossils of huge extinct mammals in Patagonia at the southern tip of South America, and observe the remark-able series of related but distinct forms of life on the Galapagos Islands, off the west coast of South America. Such an opportunity clearly played an important role in the development of his thoughts about the nature of life on earth. 

 When Darwin returned from the voyage at the age of 27, he began a long period of study and contemplation. During the next 10 years, he published important books on several different subjects, including the formation of oceanic islands from coral reefs and the geology of South America. He also devoted eight years of study to barnacles, a group of small marine animals with shells that in-habit rocks and pilings, eventually writing a four-volume work on their classification and natural history. In 1842, Darwin and his family moved out of London to a country home at Down, in the county of Kent. In these pleasant surroundings, Darwin lived, studied, and wrote for the next 40 years.


Darwin was the first to propose natural selection as an explanation for the mechanism of evolution that produced the diversity of life on earth. His hypothesis grew from his observations on a five-year voyage around the world.

Darwin's Evidence

 One of the obstacles that had blocked the acceptance of any theory of evolution in Darwin's day was the incorrect notion, widely believed at that time, that the earth was only a few thousand years old. Evidence discovered during Darwin's time made this assertion seem less and less likely. The great geologist Charles Lyell (1797-1875), whose Principles of Geology (1830) Darwin read eagerly as he sailed on the Beagle, outlined for the first time the story of an ancient world of plants and animals in flux. In this world, species were constantly becoming extinct while others were emerging. It was this world that Darwin sought to explain. 

What does Darwin saw for the evidence 

When the Beagle set sail, Darwin was fully convinced that species were immutable. Indeed, it was not until two or three years after his return that he began to consider seriously the possibility that they could change. Nevertheless, during his five years on the ship, Darwin observed a number of phenomena that were of central importance to him in reaching his ultimate conclusion. For example, in the rich fossil beds of southern South America, he observed fossils of extinct armadillos similar to the armadillos that still lived in the same area. Why would similar living and fossil organisms be in the same area unless the earlier form had given rise to the other? Repeatedly, Darwin saw that the characteristics of similar species varied somewhat from place to place. These geographical patterns suggested to him that organism lineages change gradually as species migrate from one area to another. On the Galapagos Islands, 900 kilometers (540 miles) off the coast of Ecuador, Darwin encountered a variety of different finches on the various islands. The 14 species, although related, differed slightly in appearance, particularly in their beaks. Darwin felt it most reasonable to assume all these birds had descended from a common ancestor blown by winds from the South American mainland several million years ago. 

 Eating different foods on different islands, the species had changed during their descent-"descent with modification," or evolution. These finches are discussed in more detail on pages 454 and 483. In a more general sense, Darwin was struck by the fact that the plants and animals on these relatively young volcanic islands resembled those on the nearby coast of South America. If each one of these plants and animals had been created independently and simply placed on the Galapagos Islands, why didn't they resemble the plants and animals of islands with similar climates, such as those off the coast of Africa, for example? Why did they resemble those of the adjacent South American coast instead?

The fossils and patterns of life that Darwin observed on the voyage of the Beagle eventually convinced him that evolution had taken place.

How did Darwin Inventing the Hypothesis of Natural Selection

It is one thing to observe the results of evolution, but quite another to understand how it happens. Darwin's great achievement lies in his formulation of the hypothesis that evolution occurs because of natural selection.
 
Darwin and Malthus 

Of key importance to the development of Darwin's in-sight was his study of Thomas Malthus's Essay on the Principle of Population (1798). In his book, Malthus pointed out that populations of plants and animals (including human beings) tend to increase geometrically, while humans are able to increase their food supply only arithmetically. A geometric progression is one in which the elements increase by a constant factor; for example, in the progression 2, 6, 18, 54, . . . , each number is three times the preceding one. An arithmetic progression, in contrast, is one in which the elements increase by a constant difference; in the progression 2, 4, 6, 8, . . each number is two greater than the preceding one

Because populations increase geometrically, virtually any kind of animal or plant, if it could reproduce unchecked, would cover the entire surface of the world within a surprisingly short time. Instead, populations of species remain fairly constant year after year, because death limits population numbers. Malthus's conclusion provided the key ingredient that was necessary for Darwin to develop the hypothesis that evolution occurs by natural selection. Sparked by Malthus's ideas, Darwin saw that although every organism has the potential to produce more offspring than can survive, only a limited number actually do survive and produce further offspring. Combining this observation with what he had seen on the voyage of the Beagle, as well as with his own experiences in breeding domestic animals, Darwin made an important association: Those individuals that possess superior physical, behavioral, or other attributes are more likely to survive than those that are not so well endowed. By surviving, they gain the opportunity to pass on their favorable characteristics to their off-spring. As the frequency of these characteristics increases in the population, the nature of the population as a whole will gradually change. Darwin called this process selection. The driving force he identified has often been referred to as survival of the fittest.

Darwin's Natural Selection

Darwin was thoroughly familiar with variation in domesticated animals and began On the Origin of Species with a detailed discussion of pigeon breeding. He knew that breeders selected certain varieties of pigeons and other animals, such as dogs, to produce certain characteristics, a process Darwin called artificial selection. Once this had been done, the animals would breed true for the characteristics that had been selected. Darwin had also observed that the differences purposely developed between domesticated races or breeds were often greater than those that separated wild species. Domestic pigeon breeds, for example, show much greater variety than all of the hundreds of wild species of pigeons found throughout the world. Such relationships suggested to Darwin that evolutionary change could occur in nature too. Surely if pigeon breeders could foster such variation by artificial selection, nature could do the same, playing the breeder's role in selecting the next generation—a process Darwin called natural selection.

why important the brain science

In fact, it has spawned a whole new industry. Three hot neurotech areas that promise major changes in brain research in the near future are neuroimaging, neuropharmacology, and neurodevices such as brain implants. And they are thriving. The Neurotechnology Industry Report for 2008 shows 2 billion people worldwide suffering from a brain-related illness, with an annual economic burden of more than $2 trillion. Globally, in 2008, more than 550 public and private companies participated in a neurotech industry where revenues rose 9 percent to $144.5 billion overall, with neuropharmaceuticals reporting earnings of $121.6 billion, neurodevices revenues of $6.1 billion, and neurodiagnostics revenues of $16.8 billion.

 The military has a hefty investment in this as well. Neurotechnology and research will help the thousands of soldiers returning from wars with severe brain injuries or missing limbs. Advances will also perfect the toolbox for warfare. Neuroenhancers will keep soldiers and fighter pilots awake and alert for days, and will fine-tune and juice up mental focus and reflexes. Brain-machine interfaces could create new weapons and allow exploration into deep space and other hostile territory. And neuroimaging could allow us to see into brains to predict and possibly control behavior and thoughts.

How your brain works the short version

A refresher on brain basics will help set the context for the detailed chapters that follow. Your brain is three pounds of flesh, nerves, and fluid that looks like a big walnut but is much softer. Its billion or so specialized cells called neurons communicate and form networks through chemicals (especially those called neurotransmitters) and minuscule electrical charges that pass over the tiny gaps, or synapses, between them. The overall brain is often described in three parts: the primitive brain, the emotional brain, and the thinking brain.

  The primitive brain

 the brain stem or hindbrainsits at the top of the spine and takes care of the automated basics, such as breathing, heartbeat, digestion, reflexive actions, sleeping, and arousal. It includes the spinal cord, which sends messages from the brain to the rest of the body, and the cerebellum, which coordinates balance and rote motions, like riding a bike and catching a ball. Above this, your brain is divided into two similar, but not identical, hemispheres connected by a thick band of fibers and nerves called the corpus callosum. Each side functions slightly differently than the other does, and for reasons not yet understood, the messages between the hemispheres and the rest of our body crisscross, so that the right brain controls our left side and vice versa.

 The emotional brain

The emotional brain, or limbic system, is tucked deep inside the bulk of the mid brain and acts as the gatekeeper between the spinal cord and the thinking brain in the cerebrum above. It regulates survival mechanisms such as sex hormones; sleep cycles; hunger; emotions; and, most important, fear, sensory input, and pleasure. The amygdala is our sentry, the hippo campus is the gateway to short-term memory, and the hypothalamus controls your biological clock and hormones, while the thalamus passes along sensory information to the thinking centers in the cortex above. The basal ganglia surround the thalamus, and are responsible for voluntary movement. The so-called pleasure center, or reward circuit, is also based in the limbic system, involving the nucleus accumbens and ventral tegmental area.

 the thinking brain

The thinking brain the part we usually see when we picture a brain and what is sometimes called the crown jewel of the body—sits on the top, where it controls thoughts, reasoning, language, planning, and imagination. Vision, hearing, speech, and judgment reside here as well. But let's be honest. In spite of enormous research advances, scientists still have a pretty rudimentary understanding of brain function and how it relates to your thoughts, feelings, and actions. There are frequent announcements about how the sources of some emotions and functions have been "mapped" in the brain, but most of these should be qualified: brain researchers are still trying to figure out much of what goes on between your ears. But they're gaining on it.