Evolution Explained
The most fundamental concept is that living things change as they age. These changes can help the organism to survive or reproduce, or be more adapted to its environment.
Scientists have used the new genetics research to explain how evolution operates. They have also used the science of physics to calculate how much energy is required for these changes.
Natural Selection
In order for evolution to occur for organisms to be capable of reproducing and passing their genes to the next generation. This is the process of natural selection, often described as "survival of the most fittest." However the phrase "fittest" could be misleading as it implies that only the strongest or fastest organisms can survive and reproduce. The most well-adapted organisms are ones that adapt to the environment they reside in. The environment can change rapidly and if a population isn't properly adapted to the environment, it will not be able to survive, leading to the population shrinking or disappearing.
The most fundamental component of evolutionary change is natural selection. It occurs when beneficial traits are more prevalent over time in a population which leads to the development of new species. This process is driven primarily by genetic variations that are heritable to organisms, which are a result of sexual reproduction.
Selective agents can be any element in the environment that favors or dissuades certain traits. These forces can be biological, like predators or physical, like temperature. Over time populations exposed to various selective agents can evolve so different from one another that they cannot breed together and are considered to be distinct species.
While the idea of natural selection is straightforward, it is not always easy to understand. Uncertainties about the process are widespread, even among educators and scientists. Surveys have shown that students' levels of understanding of evolution are only associated with their level of acceptance of the theory (see references).
Brandon's definition of selection is confined to differential reproduction, and does not include inheritance. But 에볼루션게이밍 of authors including Havstad (2011) and Havstad (2011), have argued that a capacious notion of selection that encapsulates the entire process of Darwin's process is adequate to explain both adaptation and speciation.
In addition there are a lot of instances where traits increase their presence in a population but does not alter the rate at which individuals who have the trait reproduce. These cases may not be classified as natural selection in the narrow sense but could still be in line with Lewontin's requirements for a mechanism to operate, such as the case where parents with a specific trait produce more offspring than parents with it.
Genetic Variation
Genetic variation is the difference in the sequences of the genes of the members of a particular species. It is the variation that allows natural selection, which is one of the primary forces that drive evolution. Variation can be caused by mutations or the normal process through which DNA is rearranged in cell division (genetic Recombination). Different gene variants may result in a variety of traits like the color of eyes, fur type or the capacity to adapt to changing environmental conditions. If a trait is characterized by an advantage it is more likely to be passed down to the next generation. This is known as a selective advantage.
A specific kind of heritable variation is phenotypic, which allows individuals to alter their appearance and behavior in response to the environment or stress. These changes could help them survive in a new habitat or make the most of an opportunity, for instance by growing longer fur to guard against the cold or changing color to blend in with a particular surface. These phenotypic changes do not necessarily affect the genotype and thus cannot be considered to have caused evolutionary change.
Heritable variation permits adapting to changing environments. It also permits natural selection to work, by making it more likely that individuals will be replaced by those with favourable characteristics for the particular environment. In certain instances however, the rate of gene transmission to the next generation may not be sufficient for natural evolution to keep pace with.
Many harmful traits, such as genetic disease persist in populations despite their negative consequences. This is due to the phenomenon of reduced penetrance, which means that certain individuals carrying the disease-related gene variant do not show any symptoms or signs of the condition. Other causes include gene-by-environment interactions and other non-genetic factors like lifestyle, diet and exposure to chemicals.
To understand why certain negative traits aren't eliminated through natural selection, we need to understand how genetic variation affects evolution. Recent studies have demonstrated that genome-wide association studies which focus on common variations don't capture the whole picture of susceptibility to disease, and that rare variants account for a significant portion of heritability. Further studies using sequencing techniques are required to identify rare variants in the globe and to determine their impact on health, as well as the influence of gene-by-environment interactions.
Environmental Changes
The environment can influence species by changing their conditions. This concept is illustrated by the famous story of the peppered mops. The white-bodied mops, that were prevalent in urban areas, where coal smoke had blackened tree barks They were easy prey for predators while their darker-bodied cousins thrived in these new conditions. The reverse is also true that environmental changes can affect species' ability to adapt to the changes they face.
Human activities are causing environmental change at a global level and the effects of these changes are largely irreversible. These changes affect biodiversity and ecosystem functions. In addition they pose significant health risks to the human population especially in low-income countries, because of pollution of water, air soil, and food.
For instance the increasing use of coal by developing countries such as India contributes to climate change, and raises levels of air pollution, which threaten the life expectancy of humans. The world's finite natural resources are being used up in a growing rate by the human population. This increases the chances that many people will suffer from nutritional deficiencies and lack of access to water that is safe for drinking.
The impacts of human-driven changes to the environment on evolutionary outcomes is a complex. Microevolutionary responses will likely alter the fitness landscape of an organism. These changes can also alter the relationship between a specific characteristic and its environment. Nomoto et. al. showed, for example that environmental factors like climate and competition, can alter the phenotype of a plant and shift its choice away from its historical optimal suitability.
It is essential to comprehend how these changes are influencing the microevolutionary responses of today and how we can use this information to determine the fate of natural populations in the Anthropocene. This is vital, since the environmental changes triggered by humans will have a direct impact on conservation efforts, as well as our own health and well-being. Therefore, it is essential to continue research on the interaction between human-driven environmental changes and evolutionary processes on an international scale.
The Big Bang
There are a myriad of theories regarding the universe's origin and expansion. But none of them are as widely accepted as the Big Bang theory, which is now a standard in the science classroom. The theory provides a wide range of observed phenomena including the number of light elements, the cosmic microwave background radiation and the large-scale structure of the Universe.
The simplest version of the Big Bang Theory describes how the universe began 13.8 billion years ago as an unimaginably hot and dense cauldron of energy that has continued to expand ever since. This expansion has shaped everything that exists today, including the Earth and all its inhabitants.
This theory is backed by a myriad of evidence. This includes the fact that we view the universe as flat as well as the kinetic and thermal energy of its particles, the variations in temperature of the cosmic microwave background radiation as well as the relative abundances and densities of lighter and heavier elements in the Universe. The Big Bang theory is also well-suited to the data gathered by astronomical telescopes, particle accelerators, and high-energy states.
In the early 20th century, scientists held an opinion that was not widely held on the Big Bang. Fred Hoyle publicly criticized it in 1949. After World War II, observations began to arrive that tipped scales in favor the Big Bang. Arno Pennzias, Robert Wilson, and others discovered the cosmic background radiation in 1964. This omnidirectional microwave signal is the result of time-dependent expansion of the Universe. The discovery of this ionized radiation, which has a spectrum consistent with a blackbody around 2.725 K, was a significant turning point for the Big Bang theory and tipped the balance in the direction of the rival Steady State model.
The Big Bang is a central part of the popular TV show, "The Big Bang Theory." The show's characters Sheldon and Leonard make use of this theory to explain a variety of phenomenons and observations, such as their research on how peanut butter and jelly get mixed together.