Selection generally refers to the pressures on crops and organisms to evolve.
sexually, sexual selection. Certain phenotypic traits (characteristics of an
organism)—or, on a genetic level, alleles of genes—segregate within a population,
where individuals with aadaptive advantages or traits tend to succeeded more than
their peers when they reproduce, and so contribute more ooffspring to the succeeding
generation. When these traits have a genetic basis, selection can increase the
prevalence of those traits, because offspring inherit them from their parents. When
selection is intense and persistent, adaptive traits become universal to the population
or species, which may then be said to have evolved.
Whether or not selection takes place depends on the conditions in which the
individuals of a species find themselves. Adults, juveniles, embryos, and gamete eggs
and sperm all undergo selection. Factors fostering selection include sexual selection,
primarily caused by mate choice in the mating phase of sexual reproduction, limits on
resources (nourishment, habitat space, mates) and the existence of threats (predators,
disease, adverse weather). Biologists often refer to such factors as selective or
Natural selection has, since the 1930s, included sexual selection because
biologists at the time did not think it was of great importance though it has become to
be seen as more important in the 21st Century.Other subcategories of natural
selection include ecological selection, stabilizing selection, disruptive selection and
selection. Selective can be seen in the breeding of dogs, and the domestication of
farm animals and crops, now commonly known as selective breeding.
Selection is hierarchically classified into natural and artificial selection. Natural
Selection occurs only when the individuals of a population are diverse in their
characteristics—or more specifically when the traits of individuals differ with respect
to how well they equip them to survive or exploit a particular pressure. In the absence
of individual variation, or when variations are selectively neutral, selection does not
become prevalent within a population. Another process of gene frequency alteration
in a population is called genetic drift, which acts over genes that are not under
selection. But, this drift can't overcome natural selection itself, as it is a 'random
sampling' process and Natural Selection is actually an evaluative force. In the face of
selection, even a so-called deleterious allele may become universal to the members of
a species. This is a risk primarily in the case of "weak" selection (e.g., an infectious
disease with only a low mortality rate) or small populations.
Though deleterious alleles may sometimes become established, selection may
act "negatively" as well as positively. Negative selection or purifying selection
decreases the prevalence of traits that diminish individuals' capacity to succeed
reproductively (i.e., their fitness), while positive selection increases the prevalence of
Charles Darwin's theory of evolution builds on three principles: natural
selection, heredity, and variation. At the time that Darwin wrote, the principles
underlying heredity and variation were poorly understood. In the 1940s, however,
biologists incorporated Gregor Mendel's principles of genetics to explain both,
resulting in the modern synthesis. It was not until the 1980s and 1990s, however,
when more comparative molecular sequence data between different kinds of
organisms was amassed and detailed, that an understanding of the molecular basis of
the developmental mechanisms began to form.
Currently, it is well understood how genetic mutation occurs. However,
developmental mechanisms are not understood sufficiently to explain which kinds of
phenotypic variation can arise in each generation from variation at the genetic level.
Evolutionary developmental biology studies how the dynamics of development
determine the phenotypic variation arising from genetic variation and how that affects
phenotypic evolution (especially its direction). At the same time evolutionary
developmental biology also studies how development itself evolves.
Thus the origins of evolutionary developmental biology come both from an
improvement in molecular biology techniques as applied to development, and from
the full appreciation of the limitations of classic neo-Darwinism as applied to
phenotypic evolution. Some evo-devo researchers see themselves as extending and
enhancing the modern synthesis by incorporating the findings of molecular genetics
and developmental biology into an extended evolutionary synthesis.
Evolutionary developmental biology can be distinguished from earlier
approaches to evolutionary theory by its focus on a few crucial ideas. One of these is
modularity: as has been long recognized, plants and animal bodies are modular: they
are organized into developmentally and anatomically distinct parts. Often these parts
are repeated, such as fingers, ribs, and body segments. Evo-devo seeks the genetic
and evolutionary basis for the division of the embryo into distinct modules, and for
the partly independent development of such modules.
The statistician Ronald Fisher (1890 – 1962) helped to form the modern
evolutionary synthesis of Mendelian genetics and natural selection.
J. B. S. Haldane (1892 – 1964) helped to create the field of population genetics.
Microbiology has recently developed into an evolutionary discipline. It was
originally ignored due to the paucity of morphological traits and the lack of a species
concept in microbiology. Now, evolutionary researchers are taking advantage of a
more extensive understanding of microbial physiology, the ease of microbial
genomics, and the quick generation time of some microbes to answer evolutionary
questions. Similar features have led to progress in viral evolution, particularly for
Many biologists have contributed to our current understanding of evolution.
Although the term had been used sporadically starting at the turn of the century,
evolutionary biology in a disciplinary sense gained currency during the period of "the
evolutionary synthesis" (Smocovitis, 1996). Theodosius Dobzhansky and E. B. Ford
were important in the establishment of an empirical research programmer for
evolutionary biology as were theorists Ronald Fisher, Sewall Wright and J. S.
Haldane. Ernst Mayr, George Gaylord Simpson and G. Ledyard Stebbins were also
important discipline-builders during the modern synthesis, in the fields of
systematics, palaeontology and botany, respectively. Through training many future
evolutionary biologists, James Crow,
Richard Lewontin, Dan Hartl, Marcus
the discipline of evolutionary biology.
Organismes and environment
State of ecosystems, habitats and species
The expansion of humans activities into the natural environment, manifested
uniformity in landscapes and consequential reduction, disappearance, fragmentation
or isolation of habitats and landscapes.
It is evident that the increasing exploitation of land for human use greatly
reduces the area of each wildlife habitat as well as the total area surface throughout
Europe. The consequences are:
A decreased species diversity, due to reduced habitable surface area which
corresponds to a reduced "species carrying capacity".
The reduction of the size of habitats also reduces the genetic diversity of the
species living there. Smaller habitats can only accommodate smaller populations, this
results in an impoverished gene pool.
The reduction of genetic resources of a species diminishes its flexibility and
evolutionary adaptability to changing situations. This has significant negative impacts
on its survival.
The conditions under which the reduction of habitats often occur prevent living
organisms making use of their normal ways to flee their threatened habitat. Those
escape routes include migration to other habitats, adaption to the changing
environment, or genetic interchange with populations in nearby habitats. Particular
The abrupt nature of human intervention; human projects are planned and
implemented on a much shorter time scale than natural processes;
Furthermore human intervention, such as the construction of buildings,
motorways or railways results in the fragmentation of habitats, which strongly limits
the possibility for contact or migration among them;
In extreme cases, even the smallest, narrowest connections between habitats
are broken off. Such isolation is catastrophic for life in the habitat fragments.
Although relatively few species of Europe's fauna and flora have actually
become extinct during this century, the continent's biodiversity is affected by
decreasing species numbers and the loss of habitats in many regions. Approximately
30 % of the vertebrates and 20 % of the higher plants are classified as "threatened".
Threats are directly linked to the loss of habitats due to destruction, modification and
fragmentation of ecosystems as well as from overuse of pesticides and herbicides,
intensive farming methods, hunting and general human disturbance. The overall
deterioration of Europe's air and water quality add to the detrimental influence.
Europe's natural environment is inextricably linked with agriculture and
forestry. Since agriculture traditionally depends on sound environmental conditions,
farmers have a special interest in the maintenance of natural resources and for
centuries maintained a mosaic of landscapes which protected and enriched the natural
As a result of needs for food production since the 1940s, policies have
encouraged increased pro- diction through a variety of mechanisms, including price
support, other subsidies and support for research and development. The success
achieved in agricultural production has however entailed increased impact on the
Modern agriculture is responsible for the loss of much wildlife and their
habitats in Europe, through reduction and fragmentation of habitats and wildlife
populations. The drainage of wetlands, the destruction of hedgerows and the intensive
use of fertilizers and pesticides can all pose a threat to wildlife. Highly specialized
monoculture are causing significant loss in species abundance and diversity. On the
other hand, increased production per hectare in intensive areas, raising of livestock
volume, and lower prices for agricultural products also caused marginalization of
agricultural land, changing the diversity of European landscapes into the direction of
two main types: Intensive Agriculture and Abandoned land.
Abandonment can be positive for nature, but this is not necessarily so. Land
of small-scale landscape diversity and can cause decrease in species diversity.
All energy types have potential impacts on the natural environment to varying
degrees at all stages of use, from extraction through processing to end use.
Generating energy from any source involves making the choices between impacts and
how far those impacts can be tolerated at the local and global scale. This is especially
of importance for nuclear power, where there are significant risks of radioactive
pollution such as at Chernobyl.
Shell Oil Company and IUCN have jointly drafted environmental regulations
for oil-exploitation in Arctic areas of Siberia. Other oil companies are aware of this
and use these environmental regulations voluntarily for developing oil fields.
Into the future, the sustainability of the natural environment will be improved
as trends away from damaging energy uses, extractive methods reduce, and whilst
real cost market forces and the polluter pays principle take effect.
The principle of the fisheries sector is towards sustainable catches of wild
aquatic fauna. The principle environmental impact associated with fisheries activities
is the unsustainable har- vesting of fish stocks and shellfish and has consequences for
the ecological balance of the aquatic environment. The sector is in a state of "crisis",
with over capacity of the fleet, overexploitation of stocks, debt, and marketing
Growing aquaculture industry may increase water pollution in Western Europe,
and is appearing to be a rising trend in the Mediterranean and Central/East Europe.
Fishing activities have an impact on cetaceans and there is concern that large
numbers of dolphins, and even the globally endangered Monk seal, are being killed.
Compared to other land uses, forest management has the longest tradition in
following sustainable principles due to which over 30% of Europe is still covered
with trees. Without such an organized approach, forests are likely to have already
disappeared from Europe's lowlands. However, as an economic sector, forestry has
also impacted severely on the naturalness of Europe's forests: soils have been drained,
pesticides and fertilizers applied, and exotic species planted. In many areas
monocultures have replaced the original diverse forest composition. Monocultures
are extremely sensitive to insect infestations, fires or wind, and so can lead to
financial losses as well as biological decline. The inadequate afforestation practices
characterize new trends in impacting on the sustainability of the natural environment.
Almost all forms of industry have an impact on the natural environment and its
sustainability. The impact varies at different stages in the life cycle of a product,
depending upon the raw materials used through to the final end use of the product for
waste residue, re-use or recycling. Industrial accidents and war damage to industrial
plants can also endanger the natural environment.
Transport and Infrastructure
Transport is perhaps the major contributor to pollution in the world today,
particularly global envy- ronmental issues such as the greenhouse effect. The key
impacts of transportation include frag- mentation of habitats and species and genetic
populations, disruption of migration and traffic mortalities to wildlife. Since the
1970s transport has become a major consumer of non-renewable resources, 80% of
oil consumption coming from road transport.
Human Impact On The Natural Environment
The environmental impact of agriculture varies based on the wide variety of
agricultural practices employed around the world. Ultimately, the environmental
impact depends on the production practices of the system used by farmers. The
connection between emissions into the environment and the farming system is
indirect, as it also depends on other climate variables such as rainfall and
There are two types of indicators of environmental impact: "means-based",
which is based on the farmer's production methods, and "effect-based", which is the
impact that farming methods have on the farming system or on emissions to the
environment. An example of a means-based indicator would be the quality of
groundwater, that is effected by the amount of nitrogen applied to the soil. An
indicator reflecting the loss of nitrate to groundwater would be effect-based.
The environmental impact of agriculture involves a variety of factors from the
soil, to water, the air, animal and soil diversity, plants, and the food itself. Some of
the environmental issues that are related to agriculture are climate change,
deforestation, genetic engineering, irrigation problems, pollutants, soil degradation,
Natural environment is of crucial importance for social and economic life. We
use the living world as
a resource for food supply
an energy source
a source for recreation
a major source of medicines
natural resources for industrial products
In this respect the diversity of nature not only offers man a vast power of
choice for his current needs and desires. It also enhances the role of nature as a source
of solutions for the future needs and challenges of mankind.
What is the difference between biochemistry, molecular biology, and genetics?
Genetics is the most distinct of the three. It studies genes, genomics, and
heredity. This can include molecular genetics, which deals directly with the DNA and
it includes population genetics, which has more to do with how different alleles
spread in a population.
I have yet to see a definition of molecular biology that does not overlap with
biochemistry. The two are nearly identical sciences. The closest I have found to a
meaningful distinction is that molecular biologists are biologists and biochemists are
chemists. Molecular biologists concern themselves with the biological processes; the
cells, the tissues, the organisms. Biochemists are more about the chemicals, which
just happen to be in a living thing; reaction mechanisms, thermodynamics, bond
angles and the like. Not that what I am saying here is universally agreed upon.
At the end of the day, the amount of overlap is massive and we are splitting
hairs by saying somebody is absolutely one and not the other. One can have a degree
in molecular biology, be a member of a genetics department, and look at the
structural biochemistry of how a protein binds to DNA.
Biochemistry has to do with chemical properties and interactions of biological
molecules. So for example we can take an isolated enzyme add substrate and measure
the kinetics of a reaction in a test tube. The experiments try to isolate specific
chemical properties, not necessarily mimicking cellular environment (which is most
often the case).
Molecular biology has to do with biological effects of specific molecules - we
add X to cell culture - do the cells die? Do they become cancerous?
Genetics looks at heritability of traits and tries to find what are the molecules
that have to do with that trait. How much of susceptibility to X can be attributed to
genetics? What is the gene that makes eyes blue?
In current research these disciplines closely intertwine, and it is almost
impossible to publish a good paper in only one of them, without having some
evidence from others. So genetics identifies the players, biochemistry says how they
likely function, and molecular biology asks how this function influences biological
properties of an organism.
Biochemistry focuses on the protein part of life functions. It studies the
components independent of the organism.
Genetics focuses on the gene part. Usually mutants are used. So, it is organism
without the component.
Molecular Biology integrates those two, as can be quite well ascertained from
the "central dogma" i.e., genes-> proteins.
So, for e.g., if one is interested in studying what imparts red color to a fruit
fly’s eyes, this is probably how the three would work:
A biochemist would make a puree of the fruit fly, isolate the component
responsible for the eye color and characterize it.
A geneticist would look for flies that have different eye colors, and compare
each of them, breed them in various combinations, observe how the traits are
inherited. So essentially, one can be blissfully unaware of the chemical nature of the
said component (gene/ protein) but still figure out how the trait is passed on/ affect a
A molecular biologist would isolate the gene, study it, and arrive at the protein
Biochemistry is the study of chemical processes within and relating to living
organisms. By controlling information flow through biochemical signaling and the
flow of chemical energy through metabolism, biochemical processes give rise to the
complexity of life. Molecular biology is a branch of science concerning biological
activity at the molecular level. The field of molecular biology overlaps with biology
and chemistry and in particular, genetics and biochemistry. and, Genetics is the study
of genes, heredity, and genetic variation in living organisms. It is generally
considered a field of biology, but it intersects frequently with many of the life
sciences and is strongly linked with the study of information systems.