Natural Selection

Genetic relatedness

It is meant to indicate the Darwinian model for evolution, as opposed to for instance the Lamarckian model. It would be true that evolution occurs and has occurred even without Darwin; but until Darwin, various explanations would have been possible for why and how it happens. Darwin first formulated the thesis that evolution is directed by differential reproductive success.

Assume you have a population of people of various genetically influenced heights; they all varied in height potential. They all were raised in an environment that was deprived of basic nutrients and all were somewhat stunted in growth. A person that would have been tall in a normal environment passes on those genes for tallness in his deprived -of -nutrients environment, so his sons/daughters, if properly feed, would grow tall. So you see, natural selection must work on the genetic/individual variation and not variations that are not inherited.

Natural selection is differential reproductive success. It occurs when a population consisting of multiple variants exist in a limited environment. Some variants will be more successful - in terms of producing offspring - than other variants. The term used to indicate the measure of reproductive success of a variant is 'fitness'. The alleles (variations of a gene) of a 'fitter' variant will have a larger representation in the next generation than the alleles of a less 'fit' variant, and so the 'fit' alleles spread throughout the population at a greater rate than less 'fit' alleles. Eventually, less 'fit' alleles may even vanish from the population entirely. When an allele is so successful that it becomes the only variant for a given gene, we say that the allele has become 'fixed'.

Note that the term 'fitness' has no direct relation to the health, strength, intelligence or speed of the variant: the only measure of 'fitness' is the reproductive success of the variant.

Because in natural selection heritable traits will be passed down allowing those species to have a better chance at survival, thus making speciation a reality.

Humans are the only cause of artificial selection. Humans take organisms that they think are useful, or may become useful and they breed them true for traits they want in the organism and they cull the organisms that do not possess traits that humans find useful. not all animals can be artificially selected though.

Right from the start, the terms "strong" and "favors" should be defined. Natural selection "favors" simply in that the mechanism allows the continuation of those who are better suited to their environment. "Strong" and "fittest" are synonymous in this regard, because it's not referring to physical strength.

Natural selection only favors those who are able to survive long enough to reproduce and thus pass on their genes. That's all there really sis to it.

They are the selective agent in natural selection ;)

Notably, the phrase 'survival of the fittest' is a particularly poor choice of words for describing natural selection, in my opinion. Mainly because, in the perception of the layman, it might be taken to mean that natural selection is a black-and-white phenomenon, always favouring more able variants, and that ability (fitness) is measured in terms of health, strength, intelligence, rather than ability to produce offspring.

A far more accurate phrase would be: differential reproductive success - meaning the difference in numbers of surviving fertile offspring between variants.

That more organisms are born than the available resources can support leading to a struggle for existence. That all these organisms are variants and that some variants are better adapted to the immediate environment and will survive and reproduce better that the other organisms in that environment. That these beneficial traits that organisms posses are heritable, passed on to progeny and change the allele frequency in populations of organisms over time leading to evolution.

Dolphins, like all other life, are entirely formed by natural selection. There's not a single part of them that hasn't been touched, over the course of their evolutionary history, reaching back to the first cellular lifeforms, by natural selection: from their overall shape and colour to the metabolic pathways in their cells.

One of the most apparent adaptations of dolphins, relative to other (land-dwelling) mammals, but not unique to dolphins alone, is the adaptation of their morphology and physiology to a completely aquatic existence.

Natural selection is the nonrandom survival and reproductive success of randomly varying individual organisms.

All populations of organisms vary, more are reproduced than can survive on the resources the immediate environment provides, some have the variant traits needed to survive and reproduce more successfully than conspecifics against the immediate environment and these individuals are said to be naturally selected.

Polygenic traits occur because of genes and environment. There are usually two or more genes involved in these traits. It also takes into consideration where the organism lives, for example the fact that some hotter areas have a history of people with darker skin tones.

Darwinism is often what opponents to evolution call evolution to make it sound like some sort of Darwin cult, but it can also be used to just refer to evolution through natural selection as it was understood in the late 1800s, though that is usually called darwinian evolution rather than "darwinism".

Also social darwinism is the application of natural selection to human civilization, the idea that the poor should starve to death because they're "weaker" etc. A faulty injection of biological science into social philosophy.

Mutations allow natural selection to occur. The mutation in a species that causes it to be the most fit will survive. the others die off. So, naturally, it is called survival of the fittest, the weak die off and the fit live on, passing their good traits to offspring. This is nature's way of perfecting a species. Mutations introduce new genetic information to an organism's genetic code

Natural variation in artificial selection is used because humans choose from among the naturally occurring variation s in species. Natural selection is related to species fitness because Darwin called natural selection survival of the fittest because those that could survive would carry their species on there for being the naturally selected.

All organisms need food, water, and shelter in order to live, grow, and reproduce.

Both establish that:

1. There are limited reproductive opportunities

2. Only those organisms with "favorable" traits will be allowed to reproduce and pass the traits onto their offspring

The difference is that artificial selection involves human intervention

small changes add up over time

His law is to make DNA more efficent.

His law of natural selection states that organisms more suited to their environment will have a higher success rate, and are more likely to reproduce. Therefore their genetics are more likely to continue into the future.

It means the reproductively fittest organisms have offspring that carry the traits that made them reproductively fit. Remember, the fittest survive to reproduce, not the strongest. In some immediate environments, among humans, that could mean the richest, the funniest, the famous, or even the luckiest.

Because many people found it contary to The Bible's - and the Church's - teachings that man had been created by God. Also many people thought the concept repugnant and or impossible that man had 'descended from the apes'.

Variations within a population. Variations mean traits that only certain individuals have that give the individual a greater or lesser chance of reproducing.

Nature selects against only harmful traits

Without variation natural selection could not select among members of a population that were all the same. How would these organisms become reproductively successful if they did not vary in the traits that allowed some to survive and reproduce, while others don't while changing the allele frequency of the population, which is the definition of evolution?