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Evolution

The scientific theory according to which populations change gradually through a process of natural selection.

5,264 Questions

Who is Ardi and why is she important?

Ardi is important because she is the oldest human skeleton in the whole world. She lived 4.4 million years ago.

Ardi shows upright walking with a somewhat prehensilefoot, but no "knuckle walking" like the Great Apes.

The mechanism by which evolution occurs is called?

Answer

Natural selection is the mechanism put forward by Darwin as one of the two essential mechanisms for evolution, the other being random mutation (which Darwin described as inheritable variation, not knowing about genes at the time).

The modern evolutionary synthesis includes genetic mutations as the mechanism which provides variations upon which natural selection can act.

What was the tallest extinct mammal ever?

The largest mammal that is ever known to have lived was Paraceratherium, also known as Indricotherium. This animal can be described as a large hornless rhino with an elongated neck and head relative to its body. Paraceratherium had a height of 5.5 m (18 ft), over 8 m (27 ft) in length without the tail, the ability to raise its head 7.5 m (25 ft) over the ground, and a skull length of 1.35 m (4.5 ft). In comparison, the largest land mammal today, the African Bush Elephant, has a height of only 3.5 m (11.5 ft). The tallest giraffes match the height of Paraceratherium, but it weighed 5-10 times more -- estimates range from 10 to 20 tons. Even though this mammal I just explained to you is over-all the largest mammal , the tallest was Megatherium, otherwise known as the Giant Ground Sloth, it stood 21 feet tall, and weighed 16 tons, it was the largest known ancestor of the Three-Toed Sloth.

What type of selection is shown when the bell curve narrows over time?

Stabilizing selection, which acts against both extreme phenotypes and favors intermediate variants. Hence the narrowing of the bell curve in the middle.

The history of plants can be understood in terms of the evolution of what kind of structures?

Over time, the demands of life on land favored the evolution of plants more resistant to the drying rays of the sun, more capable of conserving water, and more capable of reproducing without water.

Why is it important for physicians to have a clear understanding of evolution by natural selection?

Physicians prescribe drugs to the patients.But the pathogens have the propensity to evolve and become "super bugs"(so called because they are drug resistant).This could lead to a bad condition of the disease or might develop some rare form of disease.The common cause of the development of drug resistance is inappropriate dosage of drugs.In that case these drugs act as natural selection agents and could not kill the entire population of pathogens this could lead to the increase in frequency of those resistant forms of pathogens.So if a physican has a clear understanding of evolution by natural selection he will not be careless about the dosage of drugs

Explain Lamarck's idea about how animals change through use and disuse?

If an animal uses something they will keep that trait if not, it will die out. For instance, the giraffe's long neck was required for survival therefore they kept the trait (their ancestor's had shorter necks, which Lamarck explained was because they inherited traits gained by their parents "who had to increasingly stretch their necks for food"--this theory was incorrect). In the first snakes, which were basically lizards because they had legs, they no longer need the legs so they lost them.

When does Evolution occur in a population?

Evolution occurs at a constant rate from one generation to the next due to small genetic variations cause by mutation. This is known as the molecular clock. Eventually, one species will become many because these small genetic variations allows organisms with the same mutation to live in a slightly different environment. The finches of the Galapagos Islands is a good example of this type of evolutionary event. However, there time in Earth history where evolution seems to have occurred much faster. These leaps in evolution occurred because of changes in Earth climate. During these changes in climate, only the organisms with genes that allowed them to live in the new environments created by these climate changes survived. The others died off. Here is an example to this type of evolutionary event. Say there is a field of corn and in the field of corn there are a few plants that have a mutation that allows them to live with less water. While the rain fall is good this doesn't give those plants any better odds of survival than the others. However, in this example a period of low rain falls occurs causing a drought. The plants with the mutation do just grow up and create seeds just fine. The other corn plants die without create seeds.

Why are vestigial structures considered critical evidence of evolution?

Vestigial structures are considered evidence, but no more critical than any other line of evidence in Biology and palaeontology. They're considered evidence, not because of their function, but because of the way their morphologies follow the nested hierarchies of biology: the vestigial legs of whales, for instance, have exactly the kind of shape we would have expected them to have if whales had descended from land mammals. The same goes for human tailbones and embryonic branchial ridges, the wings of emus, and so on.

Evolutionists often make the distinction between evolution as a fact and evolutionary theory What does this mean?

Evolution is descent with modification. Or, change over time. And formally as the change in allele frequencies over time in a population of organisms. This is an observed and a observable fact. The theory is; the theory of evolution by natural selection, which explains the fact of evolution. Natural selection is the main mechanism ( there are others ) that drives the adaptive change in organism that can lead to speciation, or just simple evolution.

The three major categories of evidence provided by the fossil record are?

The three major categories of evidence provided by the fossil record are body fossils (actual remains of organisms), trace fossils (impressions or structures left by past organisms), and chemical fossils (organic molecules preserved in rocks). These categories help scientists understand past life forms, their environments, and evolution over time.

Theory of evolution Vs Law of Thermo Dynamics?

The theory of evolution does not vs the law of thermodynamics. They are quite compatible since the earth is an open system.

How numerous base changes could occur in DNA yet have no effect on an organism's fitness?

Any number of base changes in DNA not coding for or controlling the coding of gene expression would have no effect on an organisms fitness.

What could changes in our ancestors' teeth tell us about the evolutionary history of humans?

One simple thing is diet. Large molars and massive jaws indicate that rough vegetable matter the required heavy mastication was being consumed. Australopithecus robustus, for instance.

6 Explain why evolution by natural selection can not occur if the variation in a characteristic does not contribute to differences in fitness?

If there is not reproductive fitness conveyed by a variant trait, then natural selection has nothing to select and nothing to promote into the populational gene pool.

How are alleles frequencies related to gene pools?

The frequency of the allele represents the percentage of that allele in the gene pool

What may have occurred to prevent species that are of the same grade from also belonging to the same clade?

similar structures arising independently in different lineages, convergent evolution among different lineages, and adaptation by different lineages to the same selective pressures

What is fad in compressor?

FAD stands for Free Air Delivery which indicates the compressors capacity, it normally described in: L/Sec, m3/min or cfm. Quote: The capacity of a compressor is the full rated volume of flow of gas compressed and delivered under conditions of total temperature, total pressure, and composition prevailing at the compressor inlet. It sometimes means actual flow rate, rather than rated volume of flow. This is also called free air delivery (FAD) i.e. air at atmospheric conditions at any specific location. This term does not mean air delivered under identical or standard conditions because the altitude, barometer, and temperature may vary at different localities and at different times.

Why is evolution reffered to as a theory?

I don't exactly know why evolutionists refer to it as a theory, but I do know this.

A theory is an explanation or model based on observation, experimentation, and reasoning.

According to the definition of a theory, evolution is not a theory. Evolution cannot be based on observation. No one was here to observe it. So evolution should be classified as a hypothesis not a theory. It is only a guess as to how things came about.

Which idea did lamarck propose that was rejected by his fellow scientists?

That organisms pass on traits acquired in their lifetimes. It was rejected in favour of Darwinian evolution, in which species and not individuals evolve, but Larmarckism is valid to a point where epigenetics is concerned.