Information

Why are there still useless traits/mutations in our body


Why is it that through decades of evolution , some seemingly useless body traits such as earlobes and pubic/chest hair still remains while other traits are generally replaced through evolution?


Natural selection "selects" the trait that is less advantageous and removes/ reduces its frequency. It is like a filter paper. All solids are filtered out of mixture while clear liquid is collected. So if there is a difference in fitness of organisms by variations in traits, then only they are SELECTIVELY removed. Now, if a person without an earlobe would have had an increase in fitness, it would have had eliminated over time. And it might (I said might) be that there IS some pressure but it might be so slow that we can not realise it. But in case of earlobes, evolution will be evident in the case of elephants and Jackrabbits.


Humans are still evolving: 3 examples of recent adaptations

Evolution is an ongoing process, although many don’t realize people are still evolving. It’s true that Homo sapiens look very different than Australopithecus afarensis, an early hominin that lived around 2.9 million years ago. But it is also true that we are very different compared to members of our same species, Homo sapiens, who lived 10,000 years ago — and we will very likely be different from the humans of the future.

What we eat, how we use our bodies, and who we choose to have kids with are just some of the many factors that can cause the human body to change. Genetic mutations lead to new traits — and with the world population now above 7 billion and rising, the chances of genetic mutations that natural selection can potentially act on is only increasing.

Don't believe us? Inverse presents three examples of recent changes to the human body.

Recent, that is, in evolutionary terms. After all, Homo sapiens have only been around for about 200,000 years — and Earth is nearly 4.5 billion years old.

3. We are cooling down

In 1868, a German physician published a medical manual that established 98.6 degrees Fahrenheit as the "normal" human temperature. Since then, 98.6 degrees has generally been accepted as the average temperature. Above that, and you have a fever. Below that, and you have hypothermia.

But this Goldilocks temperature is swiftly becoming obsolete. In January, scientists discovered that we are actually way cooler than we think.

According to their study, published this January in the journal eLife, the average temperature is much more likely to be 97.9 degrees.

The team analyzed medical records from the past 200 years, which included temperature measurements. They found that, averaged together, the records indicate that there has been a gradual decrease in body temperature of 0.05 degrees Fahrenheit every decade.

Julie Parsonnet, the study’s senior author and professor of medicine at Stanford University, tells Inverse that this cooling trend is likely linked to a population-wide decline in inflammation, and improved standards of living.

Many of the infectious diseases that were common in the 19th century would have caused chronic inflammation, which in turn burns calories and increases a person’s metabolic rate — upping their internal temperature, she says. Because people aren’t battling these diseases at the same rate anymore, that change would be reflected in body temperature, she theorizes.

Living comfortably indoors may also have profoundly impacted humans. Unlike our ancestors, “we don’t have to work terribly hard to be at physiologically neutral temperatures that don’t tax our metabolism," Parsonnet says.

While healthier living likely drove this cooling trend, it’s unclear whether having a lower temperature necessarily also improves our health. The shift appears to mean that we need about 150 calories fewer per day to maintain our basic metabolic needs than we did in the past, she says. But any other consequences still need to be figured out — and though we may need fewer calories, we don’t seem to be eating any less.

“We are so much healthier than 19th-century humans,” Parsonnet says. And yet. “We’ve gotten fatter, taller, and we’ve gotten cooler. Can we get cooler still? I expect so but I’m not sure how much.”

2. Our genes are constantly changing

Humans are not immune to the effects of natural selection, Joshua Akey, professor at Princeton University, tells Inverse. Many of the same pressures that we have faced throughout the history of the human race, like pathogens, still exist and threaten our health today. But our environment has changed dramatically — and that has to have an impact, he says.

“Our environment is certainly different than it was even a century ago, and it is not hard to imagine things like gene-culture evolution playing an even more prominent role in the future of human evolution,” Akey says.

His favorite example of recent positive selection is FADS2, which is thought to be an important dietary gene. Different versions of this gene are adaptive in different populations — depending on whether or not they have more meat or plant-based diets, Akey says. For example: In 2016, scientists discovered that, over generations, eating vegetarian diets caused a population in Pune, India, to display a higher frequency of a specific mutation on the FADS2 gene. The mutation allowed them to efficiently process omega-3 and omega-6 fatty acids from non-meat sources and convert them into compounds essential for brain health — something people who follow omnivorous diets are not necessarily adapted for.

At the same time, the genes that control lactose tolerance are also increasing. As of several thousand years ago, the enzyme that helps people drink milk without getting sick turned off when people reached adulthood. But later gene mutations that sprung up around the world during a time period of between 2,000 to 20,000 years ago have helped people tolerate dairy well into their dotage. Researchers estimate that, in East Africa, that genetic change happened as recently as 3,000 years ago, as raising cattle became a larger part of human life.

Transitions in how we live our lives — like going from nomadic herder to farmer, then farmer to industrial worker — often drive these genetic adaptations. Another example of this is an apparent link between urban living and being better adapted to fight off tuberculosis. In 2010, scientists found a statistically significant association between populations that have a deep history of urbanization and a gene that’s associated with resistance to tuberculosis. That evolutionary innovation likely happened within the last 8,000 years.

Mark Thomas, professor at University College London, is one of the researchers who discovered that link. He tells Inverse that, before becoming settled farmers, human populations were exposed to a different set of infectious diseases compared to the ones that we are concerned with today. These diseases were more “opportunistic and chronic” — like worms, he says. When human society shifted to large urban settlements, diseases also shifted.

“For the last 10,000 years we have been evolving in response to the kinds of diseases that we are exposed to,” Thomas says. “Resistance to pathogens is largely genetic, so that means that natural selection does occur. It’s one of the major types of ongoing natural selection in all spaces.”

1. Our bones are becoming lighter

Compared to other hominins, human bones are weaker and less dense. In a 2015 study, scientists hypothesized that Homo sapiens bones started to weaken around 12,000 years ago — around the time that people started farming more. With settled farming, our diets changed, physical activity changed, and, in turn, our skeletons became lighter — and more fragile.

The study found that trabecular bone tissue — the porous, spongy tissue found at the end of long bones like your femur — decreased in thickness and in volume. Less nomadic hunting and more settled livestock-raising meant that the need for heavier, more durable bones decreased. This change in bone density persists in modern humans today.

“Our study shows that modern humans have less bone density than seen in related species, and it doesn’t matter if we look at bones from people who lived in an industrial society or agriculturalist populations that had a more active life,” explained lead author Habiba Chirchir, a biological anthropologist.

In a 2014 paper, scientists also determined that our skeletons have become much lighter since the rise of agriculture. They argue that reductions in physical activity, rather than a change of diet, is the root cause of degradation in human bone strength. The trend is likely to continue — people are moving less now than ever, the researchers said.

“It’s only in the last say 50 to 100 years that we’ve been so sedentary — dangerously so,” explained co-author Colin Shaw, a researcher at the University of Cambridge. “Sitting in a car or in front of a desk is not what we have evolved to do.”

Humans have the capacity to be as strong as an orangutan, Shaw and his team say. But we are not because we don’t challenge our bones. Only time will tell if our bones will change once more to enable us to challenge them in strength in the future.

We will also see if further changes happen to the body — and whether or not we can give ourselves a helping hand with new technologies, like gene editing. Some scientists hypothesize that humans will leapfrog the pace of evolution with our own inventions. Regardless of whether or not that happens, one thing is certain: Our biology will never stand still.


Dna And Mutations Webquest - DNA Webquest Name___________________ Visit the following

Dna And Mutations Webquest

A mutation is a change in dna, the hereditary material of life. These alterations can be caused by random deletion is one last type of frameshift mutation and occurs when a nitrogen base is taken out of the sequence. (conservative/nonconservative) mutations are when the new amino acid that is produced via a missense mutation has similar chemical properties to the original amino acid. Dna mutations are permanent changes in the dna sequence of a gene. As discussed in the animation, this damage may create most mutations are corrected by dna repair processes in the cell. Without mutation, evolution could not occur. So, all types of dna mutations are heritable.

Dna replication dna discovery of the dna double helix a. However, useless and less harmful ones can persist in the progeny. Mtdna mutations arising in oocytes are inherited, and depending on the number of affected molecules, may end up manifesting in the relationship of mitochondrial dna mutations to aging is still debated. Point mutations are the most common type of mutation and there are two types. Learn vocabulary, terms and more with flashcards, games and other study tools. What is gene therapy and what is its goal? This pdf book provide pogil mutations for ap biology answer key. Mutations are essential to evolution There are multiple copies per cell and.

Figure 3 from Mitochondrial DNA mutations in human disease . from ai2-s2-public.s3.amazonaws.com Change a codon to one that encodes the same amino acid and causes no change in the protein produced. Dna error in replication date: X and y linked traits. What causes sickle cell anemia? All dna mutations are copied during dna replication and transmitted from parent to descendant cells. How do dna and proteins work together to affect the metabolism of energy in cells? So, all types of dna mutations are heritable. Without mutation, evolution could not occur. Dna coloring worksheet answers x biology corner.

In a real cell, what does the dna molecule click upzip.4.

Learn and reinforce your understanding of dna mutations through video. Ultimately whether or not a particular mutation causes a detrimental effect is due to the location of the mutation within a gene (or genes) as well as the significance of that gene's function. Dna replication dna discovery of the dna double helix a. Genetic mutations may be closer than you think. What is gene therapy and what is its goal? These are known as silent mutations. Dna supplies the instructions for amino acids to form specific proteins like enzymes, which speed up. Dna error in replication date: Every living thing needs a set of instructions that are necessary to live and grow. Learn vocabulary, terms and more with flashcards, games and other study tools. Viral genomes contain either dna or rna. Alternatively, of course, you could well get a code for a different amino acid or even a stop codon. Mtdna mutations arising in oocytes are inherited, and depending on the number of affected molecules, may end up manifesting in the relationship of mitochondrial dna mutations to aging is still debated. Again, this causes the entire reading.

Without mutation, evolution could not occur. All dna mutations are copied during dna replication and transmitted from parent to descendant cells. What is gene therapy and what is its goal? Dna replication dna discovery of the dna double helix a. This pdf book provide pogil mutations for ap biology answer key. Any type of dna mutation is a permanent change in the genetic material. Students will link genetic diseases to mutations in dna.

TILLING: Not Just For the Field Anymore | Colorado Wheat from coloradowheat.org Dna and mutations webquest worksheet answer key. Mutations can also be inherited, particularly if they have a positive effect. Change a codon to one that encodes the same amino acid and causes no change in the protein produced. In biology, a mutation is an alteration in the nucleotide sequence of the genome of an organism, virus, or extrachromosomal dna. These alterations can be caused by random deletion is one last type of frameshift mutation and occurs when a nitrogen base is taken out of the sequence. A mutation is a change that occurs in our dna sequence, either due to mistakes when the dna is copied or as the result of environmental factors such as uv light and mutations contribute to genetic variation within species. Dna mutations occur when there are changes in the nucleotide sequence that makes up a strand of dna.

Description a substitution is a mutation that exchanges one base for another.

Click:dna replication (upper left) and then click unzip read the script, answer the questions below, and then, click ok.1. Since all cells in our body contain dna, there are lots of places for mutations to occur However, useless and less harmful ones can persist in the progeny. Genetic mutations may be closer than you think. What is gene therapy and what is its goal? Here is the access download page of dna and mutations webquest answer key pdf, click this link to download or read online A mutation is a change that occurs in our dna sequence, either due to mistakes when the dna is copied or as the result of environmental factors. This pdf book provide pogil mutations for ap biology answer key. Dna mutations practice worksheets answer key. Without mutations, what would not occur? Today we are going to take a look at what happens if a mistake occurs in the formation of dna. Most mtdna mutations are recessive: If one thinks of the information in dna as a series of sentences, mutations are errors in spelling the words that make up those sentences. Genomes, chromosomes, and dna web quest. They can cause diseases and conditions, but they are also tools in evolution.

Mutations are essential to evolution Click on what is dna? 1. X and y linked traits. Genomes, chromosomes, and dna web quest. Mutations and types of inherited diseases.

'Arrival of the fittest': Fragile DNA 'hot spots' play key . from geneticliteracyproject.org Change a codon to one that encodes the same amino acid and causes no change in the protein produced. Today we are going to take a look at what happens if a mistake occurs in the formation of dna. Mtdna mutations arising in oocytes are inherited, and depending on the number of affected molecules, may end up manifesting in the relationship of mitochondrial dna mutations to aging is still debated. They can cause diseases and conditions, but they are also tools in evolution. Genetic mutations may be closer than you think. Dna and mutations webquest evolution.berkeley.edu/evolibrarv/article/mutations 01 dna and mutations. Description a substitution is a mutation that exchanges one base for another. They are the raw material of genetic variation. However, useless and less harmful ones can persist in the progeny. A mutation is a change that occurs in our dna sequence, either due to mistakes when the dna is copied or as the result of environmental factors. Viral genomes contain either dna or rna. To get started finding dna and mutations webquest answer key, you are right to find our website which has a comprehensive collection of manuals listed.

Mutations are alterations to a dna sequence.

Most mtdna mutations are recessive: What is gene therapy and what is its goal? Copying errors when dna replicates or is transcribed into rna can cause changes in the sequence of bases which makes up the genetic code. In your modern biology textbook, turn to page 202. Dna replication dna discovery of the dna double helix a. Mutations range in their severity. Again, this causes the entire reading. Any type of dna mutation is a permanent change in the genetic material. Deoxyribonucleic acid is a molecule composed of two polynucleotide chains that coil around each other to form a double helix carrying genetic instructions for the development, functioning. Dna mutations are permanent changes in the dna sequence of a gene. Mutations are alterations to a dna sequence. Alternatively, of course, you could well get a code for a different amino acid or even a stop codon. However, some mutations cannot be passed on to offspring and do not matter for evolution.

So, all types of dna mutations are heritable.

They are the raw material of genetic variation.

The molecular basis of mutations 1.

In a real cell, what does the dna molecule click upzip.4.

Dna coloring worksheet answers x biology corner.

Without mutation, evolution could not occur.

Start studying dna and mutation.

Dna and mutations by the understanding evolution team.

This review outlines the basic types of dna damage caused by exogenous and endogenous factors, analyses the possible consequences of each type of damage and discusses the need for different types of dna repair.

Copying errors when dna replicates or is transcribed into rna can cause changes in the sequence of bases which makes up the genetic code.

This pdf book provide dna technology webquest answers guide.

As discussed in the animation, this damage may create most mutations are corrected by dna repair processes in the cell.

A mutation is a change in dna, the hereditary material of life.

Where are these instructions 18.

Most mtdna mutations are recessive:

Start studying dna and mutation.

How do dna and proteins work together to affect the metabolism of energy in cells?

This webquest was designed to help students understand be sure to mutate the original dna sequence since mutations occur in the dna.

Where are these instructions 18.

However, useless and less harmful ones can persist in the progeny.

Where are these instructions 18.

Dna mutations occur when there are changes in the nucleotide sequence that makes up a strand of dna.

This webquest was designed to help students understand be sure to mutate the original dna sequence since mutations occur in the dna.

In this tutorial, we'll explore

Click:dna replication (upper left) and then click unzip read the script, answer the questions below, and then, click ok.1.

Today we are going to take a look at what happens if a mistake occurs in the formation of dna.

Without mutation, evolution could not occur.

Mutations range in their severity.

Mutations, for the most part, are harmless except when they lead to cell death or tumor formation.

These alterations can be caused by random deletion is one last type of frameshift mutation and occurs when a nitrogen base is taken out of the sequence.


TAS2R38 and the supertaster variant.

About a quarter of the population tastes food way more intensely than the rest of us.

These "super tasters" are more likely to put milk and sugar in bitter coffee, or avoid fatty foods. The reason for their reaction, scientists think, is programmed into their genes, specifically one called TAS2R38 , the bitter-taste receptor gene.

The variant responsible for super tasting is known as PAV, while the variant responsible for below-average tasting abilities is known as AVI.


3. We're resisting infectious diseases.

In 2007, a group of researchers looking for signs of recent evolution identified 1800 genes that have only become prevalent in humans in the last 40,000 years, many of which are devoted to fighting infectious diseases like malaria. More than a dozen new genetic variants for fighting malaria are spreading rapidly among Africans. Another study found that natural selection has favored city-dwellers. Living in cities has produced a genetic variant that allows us to be more resistant to diseases like tuberculosis and leprosy. "This seems to be an elegant example of evolution in action," says Dr. Ian Barnes, an evolutionary biologist at London's Natural History Museum, said in 2010 statement. "It flags up the importance of a very recent aspect of our evolution as a species, the development of cities as a selective force."


Auricular muscles control the visible part of the ear, but humans have lost the ability to use them. Other mammals use these muscles to detect prey and predators.

The auricular muscles of the ear help other mammals localize sound and express emotion, according to Britannica. Unlike humans, animals such as cats have to move their ears to hear well. But Amir said that since we have flexible necks, we no longer have the need to move our ears toward sounds.

Some humans can wiggle their ears, but that's the best we can do.


What are viruses

A virus essentially is genetic information in a capsule. That’s the blandest explanation I could come up with, but it works. Are viruses alive? The current consensus is that they are somewhere in between. They are not alive because they lack several properties of life, such as cellular organelles or metabolism, yet viruses are not non-living either, as they do share some life-like properties. For example, replication and evolution.

Evolution has lead to a large diversity of viruses around us. Don’t be alarmed, though. We tend to think about viruses as something bad, yet, the majority of them are harmless to us. For example, most viruses of other animals can’t hurt us. We can’t catch FIV (the cat equivalent of HIV) and we are completely out of reach of viruses that infect plants. But there is more. There are also viruses that infect bacteria, and, hell yeah, there are viruses that infect other viruses.

Evolution has lead to a large diversity in the viral world. Illustration by iimages.

In our immediate interest, of course, are viruses that infect humans. Equally interesting are also ones that infect other animals but potentially could evolve an ability to infect us.

You probably have heard that current coronavirus SARS-CoV-2 originally comes from bats after an evolutionary change that allowed it to infect us, as well. Evolution is also the reason why flu comes to us in a new shape each season or why HIV is now becoming resistant to previously established treatments. So, the question is how this happens.


6. The ear muscles surrounding the auricle

They were formerly actively used by our ancestors, but now, they do not perform any useful function for modern humans, so we add them to the list of useless human body parts.

Other animals use these muscles to determine the danger or when catching prey. In addition, some animals use the movement of ears for the expression of emotions.

Cats, due to their ability to move their ears, have excellent hearing

Some people can still move their ears a little, but this doesn’t compare with what our ancestors were capable of.


The evolutionary effect of the mutation

Without mutations, evolution would not be possible. Without the concept of mutation, life would probably be reduced to the first organism that ever existed, the ancestor of all living beings, which would not have changed at all throughout the ages.

The mutation is a source of diseases and disorders, but also is a necessary factor for living species to evolve. If there are no genetic differences between individuals, theoretically they are all equally sensitive or resistant to different environmental factors. A strong environmental change may wipe out a population with little genetic diversity, but wide variability allows part of the species to adapt more easily.

This adaptive capacity that derives from DNA mutations is a mechanism deliberately used by living organisms in some cases. One example is the “SOS response” of bacteria, whereby they deliberately induce random changes to their DNA in a desperate attempt to adapt to a life-threatening environmental change.

Another curious example of adaptive mutagenesis (production of mutations) would be the one seen in tumors. As they grow and develop, some tumors favor a certain chaos and uncontrolled genetic material. This increased mutagenesis is related to increased survival, aggressiveness and adaptability of the tumor population.


20 Useless Body Parts (Why Do / Did We Need Them?)

This list was found on the net and was originally drafted by Jocelyn Selim.

VOMERONASAL ORGAN
A tiny pit on each side of the septum is lined with nonfunctioning chemoreceptors. They may be all that remains of a once extensive pheromone-detecting ability.

EXTRINSIC EAR MUSCLES
This trio of muscles most likely made it possible for prehominids to move their ears independently of their heads, as rabbits and dogs do. We still have them, which is why most people can learn to wiggle their ears.

WISDOM TEETH
Early humans had to chew a lot of plants to get enough calories to survive, making another row of molars helpful. Only about 5 percent of the population has a healthy set of these third molars.

NECK RIB
A set of cervical ribs&mdashpossibly leftovers from the age of reptiles&mdashstill appear in less than 1 percent of the population. They often cause nerve and artery problems.

THIRD EYELID
A common ancestor of birds and mammals may have had a membrane for protecting the eye and sweeping out debris. Humans retain only a tiny fold in the inner corner of the eye.

DARWIN&rsquoS POINT
A small folded point of skin toward the top of each ear is occasionally found in modern humans. It may be a remnant of a larger shape that helped focus distant sounds.

SUBCLAVIUS MUSCLE
This small muscle stretching under the shoulder from the first rib to the collarbone would be useful if humans still walked on all fours. Some people have one, some have none, and a few have two.

PALMARIS MUSCLE
This long, narrow muscle runs from the elbow to the wrist and is missing in 11 percent of modern humans. It may once have been important for hanging and climbing. Surgeons harvest it for reconstructive surgery.

MALE NIPPLES
Lactiferous ducts form well before testosterone causes sex differentiation in a fetus. Men have mammary tissue that can be stimulated to produce milk.

ERECTOR PILI
Bundles of smooth muscle fibers allow animals to puff up their fur for insulation or to intimidate others. Humans retain this ability (goose bumps are the indicator) but have obviously lost most of the fur.

APPENDIX
This narrow, muscular tube attached to the large intestine served as a special area to digest cellulose when the human diet consisted more of plant matter than animal protein. It also produces some white blood cells. Annually, more than 300,000 Americans have an appendectomy.

BODY HAIR
Brows help keep sweat from the eyes, and male facial hair may play a role in sexual selection, but apparently most of the hair left on the human body serves no function.

PLANTARIS MUSCLE
Often mistaken for a nerve by freshman medical students, the muscle was useful to other primates for grasping with their feet. It has disappeared altogether in 9 percent of the population.

THIRTEENTH RIB
Our closest cousins, chimpanzees and gorillas, have an extra set of ribs. Most of us have 12, but 8 percent of adults have the extras.

MALE UTERUS
A remnant of an undeveloped female reproductive organ hangs off the male prostate gland.

FIFTH TOE
Lesser apes use all their toes for grasping or clinging to branches. Humans need mainly the big toe for balance while walking upright.

FEMALE VAS DEFERENS
What might become sperm ducts in males become the epoophoron in females, a cluster of useless dead-end tubules near the ovaries.

PYRAMIDALIS MUSCLE
More than 20 percent of us lack this tiny, triangular pouchlike muscle that attaches to the pubic bone. It may be a relic from pouched marsupials.

COCCYX
These fused vertebrae are all that&rsquos left of the tail that most mammals still use for balance and communication. Our hominid ancestors lost the need for a tail before they began walking upright.

PARANASAL SIN– USES
The nasal sinuses of our early ancestors may have been lined with odor receptors that gave a heightened sense of smell, which aided survival. No one knows why we retain these perhaps troublesome mucus-lined cavities, except to make the head lighter and to warm and moisten the air we breathe.

In 1859, Charles Darwin (1809-1882) published The Origin of Species, which articulated the first full-fledged theory of evolution by natural selection. Darwin viewed the history of life like a tree, each fork in the tree&rsquos limbs representing a shared ancestry. The tips of the limbs represented modern species and the branches represented the common ancestors shared amongst species. To explain these relationships, Darwin contended that all living things were related and descended from a few forms, or even from a single common ancestor, in a process he described as “descent with modification”.

Darwin’s view was controversial because humans did not receive special consideration in this evolutionary tree: they were merely one of its many branches. Though he did not make this explicit at first, his friend and supporter T. H. Huxley soon presented evidence that humans and apes shared a common ancestor. The popular press of the day misinterpreted this as an assertion that humans were descended from monkeys.

Darwin’s explanation of the mechanism of evolution relied on his theory of natural selection, a theory developed from the following observations:

1. If all the individuals of a species reproduced successfully, the population of that species would increase exponentially.
2. Except for seasonal fluctuations, populations tend to remain stable in size.
3. Environmental resources are limited.
4. The traits found in a population vary extensively. No two individuals in a given species are exactly alike.
5. Many of the variations found in a population can be passed on to offspring.

From these observations, Darwin deduced that the production of more offspring than the environment can support leads to a struggle for existence, with only a small percentage of individuals surviving in each generation. He noted that the chance for surviving this struggle is not random, but depends on how well-adapted each individual is to its environment. Well-adapted, or “fit” individuals will more likely leave a greater number of offspring than their less well-adapted competitors. Darwin concluded that the unequal ability of individuals to survive and reproduce leads to gradual changes in the population as the traits which help the organism survive and reproduce accumulate over generations and those that inhibit its survival and reproduction are lost. Darwin used the term natural selection to describe this process.

The variations in a population arise by chance mutations in DNA, but natural selection is not a process of chance: the environment determines the probability of reproductive success. The end products of natural selection are organisms that are adapted to their present environments.

Natural selection does not involve progress towards an ultimate goal. Evolution does not necessarily strive for more advanced, more intelligent, or more sophisticated life forms. For example, fleas (wingless parasites) are descended from a winged, ancestral scorpionfly, and snakes are lizards that no longer require limbs. Organisms are merely the outcome of variations that succeed or fail, dependent upon the environmental conditions at the time. In reality, when the environment changes, most species fail to adapt and become extinct.