Remember that natural selection doesn't act directly on characteristics that are neither advantageous or deleterious. So a vestigial structure that doesn't affect the success of a organism/species can remain part of the population.
If you understand the Hardy-Weinberg principle which states that a trait that is neither selected for or against remains in the population at the same frequency.
Most of the "higher evolved" animals I can think of have a vestigial structure or two. The most common example given is of the vestigial leg structures that can be found in the back of whales. Ostriches can't fly so i think their wings are considered vestigial. Humans have a vestigial tail bone.
It shows that the organism once had a fully functioning organ/structure, but due to some kind of environmental pressure, that organ was no longer beneficial. Because it was no longer beneficial, it was actually detrimental, because the organism required energy to grow these organs, now wasted energy. Evolution's mechanism is natural selection. This organ is now being selected against, organisms that grew smaller ones now had an advantage over ones with larger ones. So over time, the average size of that organ within the population will shrink, and it will be considered vestigial when it no longer serves its original function. There's a reason why vestigial organs do not disappear completely, and that's because when the organ is so small and the organism is not wasting as much energy to grow it, it is no longer being selected against. Or in some cases the vestigial organ does have a tiny bit of use and is now beneficial.
Simple observation. Look at the many species that have evolved to specialize to a specific environment. Let's say you have daisies growing in your yard. They will have some natural differences in them. Some may be taller than others. You mow your yard on a regular basis. Many of the taller ones can't survive long enough to go to seed. More of the naturally short ones survive to "mate" with other short ones and soon enough their genes come to dominate in that environment. Eventually you wind up with a species of short-stemmed daisies. However, that fact that this is an observable truth does not prove the idea that one species evolved from another (the theory of evolution). While it suggests that this is possible, there is a woeful lack of evidence to prove it. Even Darwin knew this and wrote about it. Those short daisies are still daisies.
There will be water shortages if too much water is removed from the ecosystem.
disruptive selection favors the extremes of a range of selection Disruptive selection refers to natural selection that favors phenotypic extremes. Example (off the top of my head, but based loosely on reality): Consider a population of seed-eating birds with beaks that range in size, so that big beaks are best adapted to eating big seeds, small beaks are best adapted to small seeds, and medium beaks are best adapted to medium seeds. Now suppose that the source of medium seeds goes extinct (perhaps because of a fungal pathogen). The bird phenotype with medium beaks looses its food source; selection favors the big and small beaks.
Vestigial structures do not harm the organism. Nature selects against only harmful traits.
Vestigial structures are remnants of features that were once functional in an organism's ancestors but are no longer needed in the current environment. Natural selection does not actively remove these structures because they do not typically have a negative impact on an organism's fitness. Since they do not hinder survival or reproduction, they are not actively selected against.
Yes, because vestigial structures can be harmful. For example, some humans are now born without an appendix which ensures they will not be killed via appendicitis. Having a smaller expression of a vestigial structure, like having a smaller appendix, saves on the energy wasted in maintaining an unneeded structure.
When they first appeared, they all had a hard shell to protect them, as they evolved and natural selection removed some of their relatives, this trait was removed and (like octopodes and squid) the shell became a vestigial structure and was removed.
They are not needed (we have enough teeth without them) and there is no room for them. Almost everyone needs to get them removed. They are more of a pain (literally) than they are worth.
The appendix is removed. The appendix is a vestigial organ found in the cecum. If it gets inflamed, it is removed and the surgery is called appendectomy.
Vestigial sideband (VSB) is a type of amplitude modulation ( AM ) technique (sometimes called VSB-AM ) that encodes data by varying the amplitude of a single carrier frequency . Portions of one of the redundant sidebands are removed to form a vestigial sideband signal - so-called because a vestige of the sideband remains.
Something that is attached to the structure that can be removed.
The large feathery structures are the gills.
Most of the "higher evolved" animals I can think of have a vestigial structure or two. The most common example given is of the vestigial leg structures that can be found in the back of whales. Ostriches can't fly so i think their wings are considered vestigial. Humans have a vestigial tail bone.
the tail
Diseases are an agent of selection. Exposed animals that survive the disease process are the ones that live to reproduce. Individuals that succumb are removed from the gene pool. The mechanism of survival could be a more robust immune system or mutation(s) that is/are inherently immune for reasons other than immune response.