volution is the cornerstone of modern biology. It unites all the fields of biology under one theoretical umbrella. It is not a difficult concept, but very few people — the majority of biologists included — have a satisfactory grasp of it. One common mistake is believing that species can be arranged on an evolutionary ladder from bacteria through “lower” animals, to “higher” animals and, finally, up to man. Mistakes permeate popular science expositions of evolutionary biology. Mistakes even filter into biology journals and texts.
For example, Lodish, et. al., in their cell biology text, proclaim, “It was Charles Darwin’s great insight that organisms are all related in a great chain of being…” In fact, the idea of a great chain of being, which traces to Linnaeus, was overturned by Darwin’s idea of common descent. Misunderstandings about evolution are damaging to the study of evolution and biology as a whole. People who have a general interest in science are likely to dismiss evolution as a soft science after absorbing the pop science nonsense that abounds. The impression of it being a soft science is reinforced when biologists in unrelated fields speculate publicly about evolution. This is a brief introduction to evolutionary biology.
I attempt to explain basics of the theory of evolution and correct many of the misconceptions. Evolution is a change in the gene pool of a population over time. A gene is a hereditary unit that can be passed on unaltered for many generations. The gene pool is the set of all genes in a species or population. The English moth, Biston betularia, is a frequently cited example of observed evolution. [evolution: a change in the gene pool] In this moth there are two color morphs, light and dark. H.
The Essay on The Microscope: Science’s Greatest Invention
The microscope has been one of the greatest inventions in the history of science and has had the most impact on the course of science. Ever since the first microscope was invented in 1590, they have improved our knowledge in basic biology and biomedical research, as well as many other things, all of which are important. The smallest object a human can see with the naked eye is 0.2 mm, for example, ...
B. D. Kettlewell found that dark moths constituted less than 2% of the population prior to 1848. The frequency of the dark morph increased in the years following. By 1898, the 95% of the moths in Manchester and other highly industrialized areas were of the dark type. Their frequency was less in rural areas. The moth population changed from mostly light colored moths to mostly dark colored moths.
The moths’ color was primarily determined by a single gene. [gene: a hereditary unit] So, the change in frequency of dark colored moths represented a change in the gene pool. [gene pool: the set all of genes in a population] This change was, by definition, evolution. The increase in relative abundance of the dark type was due to natural selection. The late eighteen hundreds was the time of England’s industrial revolution. Soot from factories darkened the birch trees the moths landed on. Against a sooty background, birds could see the lighter colored moths better and ate more of them. As a result, more dark moths survived until reproductive age and left offspring.
The greater number of offspring left by dark moths is what caused their increase in frequency. This is an example of natural selection. Populations evolve. [evolution: a change in the gene pool] In order to understand evolution, it is necessary to view populations as a collection of individuals, each harboring a different set of traits. A single organism is never typical of an entire population unless there is no variation within that population. Individual organisms do not evolve, they retain the same genes throughout their life. When a population is evolving, the ratio of different genetic types is changing — each individual organism within a population does not change. For example, in the previous example, the frequency of black moths increased; the moths did not turn from light to gray to dark in concert. The process of evolution can be summarized in three sentences: Genes mutate.
The Essay on Are We Evolving Evolution Change Gene
Are we evolving? And if so, into what? I most definitely think that we are evolving. "Evolution is all the change that have occurred in living things since the beginning of life." The same fundamental characteristic is shared by every and all-living things. For example, the fossil records, development, and biochemistry. Also Charles Darwin theory of education. Evolution is described as a process ...
[gene: a hereditary unit] Individuals are selected. Populations evolve. Evolution can be divided into microevolution and macroevolution. The kind of evolution documented above is microevolution. Larger changes, such as when a new species is formed, are called macroevolution. Some biologists feel the mechanisms of macroevolution are different from those of microevolutionary change. Others think the distinction between the two is arbitrary — macroevolution is cumulative microevolution. The word evolution has a variety of meanings.
The fact that all organisms are linked via descent to a common ancestor is often called evolution. The theory of how the first living organisms appeared is often called evolution. This should be called abiogenesis. And frequently, people use the word evolution when they really mean natural selection — one of the many mechanisms of evolution. Common Misconceptions about Evolution Evolution can occur without morphological change; and morphological change can occur without evolution. Humans are larger now than in the recent past, a result of better diet and medicine.
Phenotypic changes, like this, induced solely by changes in environment do not count as evolution because they are not heritable; in other words the change is not passed on to the organism’s offspring. Phenotype is the morphological, physiological, biochemical, behavioral and other properties exhibited by a living organism. An organism’s phenotype is determined by its genes and its environment. Most changes due to environment are fairly subtle, for example size differences. Large scale phenotypic changes are obviously due to genetic changes, and therefore are evolution. Evolution is not progress.
Populations simply adapt to their current surroundings. They do not necessarily become better in any absolute sense over time. A trait or strategy that is successful at one time may be unsuccessful at another. Paquin and Adams demonstrated this experimentally. They founded a yeast culture and maintained it for many generations. Occasionally, a mutation would arise that allowed its bearer to reproduce better than its contemporaries.
The Essay on Mechanistic Thinking Changing Environment
Introduction Organisations are tools to aid in achieving a set goal. Organisations same as corporations have been developing and improving with time to improve profitability through increased productivity and quality. Most organisations are run like machines 24 hour a day, 7 days a week. All complex tasks and goals have been subdivided into simple 1-step operations that can be controlled with ...
These mutant strains would crowd out the formerly dominant strains. Samples of the most successful strains from the culture were taken at a variety of times. In later competition experiments, each strain would outcompete the immediately previously dominant type in a culture. However, some earlier isolates could outcompete strains that arose late in the experiment. Competitive ability of a strain was always better than its previous type, but competitiveness in a general sense was not increasing. Any organism’s success depends on the behavior of its contemporaries.
For most traits or behaviors there is likely no optimal design or strategy, only contingent ones. Evolution can be like a game of paper/scissors/rock. Organisms are not passive targets of their environment. Each species modifies its own environment. At the least, organisms remove nutrients from and add waste to their surroundings. Often, waste products benefit other species.
Animal dung is fertilizer for plants. Conversely, the oxygen we breathe is a waste product of plants. Species do not simply change to fit their environment; they modify their environment to suit them as well. Beavers build a dam to create a pond suitable to sustain them and raise young. Alternately, when the environment changes, species can migrate to suitable climes or seek out microenvironments to which they are adapted.
