NATURAL SELECTION
When you take look at the environment related with the species that are living on that specific environment and you know that some organisms tend to live at certain regions, but not in other regions of the world or some organisms like microorganisms, they grow in certain regions of your body but not in the other parts because of the PH of that environment, temperature of that environment and moisture of that environment. It totally depends. So there are different types of environments and depending on those environments, there is a certain type of flora or fauna in that environment that we can see, when we take a look at the environment or watch the documentaries on TV or so.
For example; there are cactuses and they have some type of adaptations related with living in drought conditions or hot temperatures, like they lose their leaves but instead of that, they have fur-like structures in order to reflect the light. So they can decrease the body temperatures for themselves and also, in order to decrease the surface to volume ratio they have that huge stem structures and as a result, they adapt their environment and they survive in that conditions and in that certain environment. So when we talk about the adaptation, we’re talking about a characteristics which enhances the survival and also reproduction of that organism comparing to the alternative states. There may be alternative states but those alternative states wont be able to live in that environment and they wont be able to survive or wont give new generations in that environment otherwise they don’t have adaptations. In nature there are a lot of structural adaptations like that, depending on the feeding system, depending on the temperature of the environment,depending on the predators so it totally depends.
Snake that swallowed an Alligator There are different types of skeletal features, so that they have the ability to open their mouth or jaw bones, that lead themselves to swallow the whole animal. The human jaw bones are impossible to get the whole organism inside their mouth. But with the adaptations of snakes, they have the ability to do that. Depending on the genus or the species of those snakes, some of them are poisonous and they give that poison with ther fangs. Fangs are the teeth like structures of snakes. Whenever they close their mouth the fangs are rotating inside the mouth so that, it doesn’t bite itself. Or they just suffocate their prey by sequeezing them. So they have different types of adaptations in order to survive and give new generations to that environment.
In the case of plants, they have different types of adaptations; either they are pollinated by beetles (böcek) , they are pollinated with birds and they have special features on their flower patterns or the color is that they have depending on how attractive to be seen by this types of pollinators. And depending of that, the birds or the beetles/ insects have specific types of features in order to get the nectar from those types of flower patterns. In order to get the nectar they need to have certain type of beaks (gaga) for the birds. If the nectar is inside of the flower they need to have longer beaks, so they can reach the nectar inside of that plant. Otherwise, if they’re pollinated by beetles then these flowers may have a surface on themselves so that insects can land on those regions. So that they can stand there, and then get the pollen and nectar from there. On both sides, depending on the fauna and flora it shapes the populations that are living in that certain area.
Definition: That is, preadaptation refers to the possibility of a characteristic to adopt a new biological function without evolutionary modification. The idea that the function of a trait might shift during its evolutionary history was initially developed by Darwin (1859). On the other side, there are Alcids that is kind of a seagull (martı). They have the ability to fly under the sea water. These are examples of preadaptations or time to time it is called EXAPTATION. Definition: Exaptation is the process of adaptation of a trait for a purpose other than what the trait was evolved for. For instance, an exaptation could be the use of feathers for mating displays or flight in birds which evolved feathers originally to keep warm. Ex: ALCIDS There are different types of adaptations related with the environment that are helping these organisms to stay alive in that certain environment and give their alleles to the next generations. Futuyma: A preadaptation is a feature that fortuitously serves a new function. For instance, parrots have strong, sharp beaks, used for feeding on fruits and seeds. when domesticated sheep were introduced into New Zealand, some were attacked by an indigenous parrot, the kea (Nestor Notabilis), which pierced the skin and fed on sheep's fat. The kea's beak was fortuitously suitable for a new function and may be viewed as a preadaptation for slicing skin. Preadaptations that have actually been co-opted to serve a new function have been termed exaptations. For example, the wings of alcid birds such as guillemots may be considered exaptations for swimming: these birds "fly" under water as well as in air. An exaptation may be further modified by selection so that the modifications are adaptations for the feature's new function: the wings of penguins have been modified into flippers and cannot support flight in air.
Explanation of Evolution by Natural Selection By Darwin: Depending on him, in the battle of life the ones that have a best chance of surviving and creating their kinds are in some way selected. Depending on him, the nature of populations are as follows;
- The individuals within a population differ from one another
- The differences are, at least in part, passed from parents to offspring
- Some individuals are more successful at surviving and reproducing than others
- The successful individuals are not merely lucky, instead, they succeed of variant traits they have inherited and will pass to their offspring. The individuals with the most favorable variations, those who are better at surviving and reproducing are naturally selected. If all four postulates are true then the composition of the population changes from one generation to the next.
Its about adaptation to the environment. If you adapt to that environment you survive. If you don’t however lucky you’re, you won’t live in that environment.
For example; in CHERNOBYL because of the radiation, a lot of species have died. But there are some bacteria that are tolerated the radioactivity and also cockroaches (hamam böcekleri) can survive in that environment. So if they have the certain types of adaptations that is related with their alleles (related with their genes) and if they can eliminate the effects of this negative environmental conditions, they stay alive.
Depending on the Darwin’s postulates, the individuals which are fitting to the environment means that their offsprings will fit to the environment and they’re going to increase their allele frequencies in that environment because they’re fitting to that environmental conditions.
In Daily basis, the mean and usage of fitness is a little bit different than that. When we think about the fitness it means; individuals’ ability to survive and reproduce in its environment. But on the other side when we think about fitness diet, exercise comes to people’s minds bu that is not the case for the jargon in evolution for fitness.
Characteristics of Natural Selection
While we’re talking about evolution we always talk about populations eventhough they have variations or so.
- Natural selection acts on individuals but its consequences ocur in populations
- Natural selection acts on phenotypes, but evolution consists of changes in allele frequencies and these chances are seen in phenotypes.
- Natural selection is not forward looking, we’re adapting right now’s conditions not the future.
- New traits can evolve eventhough natural selection acts on existing traits, there is a gradual change depending on the environmental conditions certain alleles are selected, stay alive and the others are eliminated from the environment
- Natural selection doesn’t lead to perfection and actually it doesn’t have a purpose this is something that is occuring and it just occurs.
- Natural selection is random, but it is not progressive
- Fitnesss is not circular, so it leds us to have variations which leads a favorable state for that time.
- Selection acts on individuals not for good of the species, because at that time, that is happening for that individual to stay alive. It occurs when the spontaneous mutation rates or DNA polymerase that adds wrong nucleotides to sequence while during the replication and it is skipped from the DNA repair mechanisms and so have that variation in our genome.
Depending on all of these characteristics and information that is taken from the developments in science Modern Synthesis occurs on the Darwin’s postulates ;
Modern Synthesis
- Individuals vary as a result of mutation creating new alleles, and segregation and independent assortment shuffling of alleles into new combinations. - Individuals past are alleles onto their offspring intact - In every generation some individuals are more successful at surviving and reproducing than others - The individuals most successful at surviving and reproducing are those with the alleles and allelic combinations that best adapt them to their environment The outcome is that alleles associated with higher fitness increasing in frequency from one generation to the next. These are the stuff that are related with the natural selection.
What is natural selection natural selection is one of several key concepts contained within the theory of evolution. To understand exactly what natural selection is and why it's so important let's first first take a quick look at two other evolutionary concepts: Descent with modification and the overarching idea of Common descent. Descent with modification is the observable fact that when parents have children,
those children often look and behave slightly different than their parents and slightly different than each other. They descent from their parents with modifications. The difference is found in offspring are partially due to random genetic mutations. Common descent is the idea that all life is on Earth is related.We descended from a common ancestor. Through the gradual process of descent with modification over many many generations, a single original species is thought to have given rise to all the life we see. The common descent of all life on Earth is not a directly observable fact. We have no way of going back in time to watch it happen.Inatead common descent is a conclusion based on a massive collection of observable facts. Facts found independently in the study of fossils, genetics, comparative anatomy, mathematics, biochemistry and species distribution. Descent with modification simply produces random variation.
Random descent with modification alone could never do a variation among related species. Because of the selective breeding there can be different forms of the same vegetable or animal. Random descent with modification create new traits. Darwin proposed that nature itself It's also capable of selection When parents produce a variety of offspring, Nature simply by being difficult to surviving decides which of those variations get to live and reproduce and which do not. Over multiple generations creatures became more and more fit for survival and reproduction within their specific environments. Darwin called this process Natural Selection.
What exactly is natural selection ?
Natural selection is the process by which random evolutionary changes are selected for by nature in a consistent, orderly, non-random way. Through the process of descent with modification new traits are randomly produced. Nature then carefully decides which of those new traits to keep. Positive changes add up over multiple generations, negative traits are quickly discarded. Trough this simple ongoing process Nature, even though it may not have a thinking mind, Is capable of producing incredibly complex creations.
