General overview The evidence for evolution Darwin and other 19th-century biologists found compelling evidence for biological evolution in the comparative study of living organisms, in their geographic distribution, and in the fossil remains of extinct organisms.
A look at cichlid fish in Lake Victoria This is the first in what I hope to be a series of postings. In the series I hope to accomplish two things, establish that evolution is an active branch of mainstream science and that there is indeed an overwhelming amount of evidence in favor of the idea of evolution.
Note that no single post is meant to be a proof, just another piece of evidence that supports the theory of evolution. In the October 11th issue of Nature, Meyer et. If they all share a recent common ancestor in that lake or came from separate lineages that invaded the lake.
In their paper they sequenced a bp part of the cytochrome b gene and a bp segment of mitochondrial DNA from what is called the control region. They sequenced these genes from several species of fish in the lake and a few species from relatively nearby lakes.
What they found was the sequences in the Lake Victoria species of fish were all very similar, but they were different from the sequences of fish in nearby lakes.
All the sequences are listed in the paper.
They came to the conclusion that this indicated the cichlid species of Lake Victoria all derive from a recent common ancestor in the lake. They estimate the time of divergence at aboutyears ago based on a model that assumes mutations are relatively constant over time.
The lake, incidentally, had been independently dated to be-years old The News and Views section of that issue has an overview of the paper written by John Avise. Also, the cover photo of this issue consists of a picture of several of these fish. As I said in part one, I have two goals in for this series.
One, to show that evolution is an accepted branch of mainstream science. And two, that contrary to the continual assertions of creationists, there is an overwhelming amount of data in favor of the theory of evolution.
Again, note that no single post is intended as a stand alone proof. This post is divided into two section, an introduction the part you are reading to provide a bit of background, and the actual summary of the paper discussed.
Speciation occurs when two or more possibly subsets of a formerly interbreeding population become reproductively isolated. For many years, speciation theorists thought that virtually all speciation occured when the two subsets of the population where separated by geographical boundaries.
Reproductive isolation followed physical isolation as the two, now separate lineages, diverged. This could occur for many reasons, for example mating rituals grew different or chromosome numbers changed etc.
In any case the end result would be that the two lineages could no longer interbreed if they encountered each other. Incidentally this type of speciation is called allopatric speciation. A second type of speciation, sympatric speciation, occurs when two lineages of a formerly interbreeding population diverge to the point of reproductive isolation while still residing in the same locale.
This was first demonstrated to occur by Guy Bush working on the Apple maggot fly Rhagoletis pomenella. The paper I will outline here is one found in the August 9, issue of Nature. I will continue this discussion in my next post. Isolation mediated by microorganisms In the paper outlined here Breeuwer and Werren, the authors examine two species of wasps living sympatrically in the same area.
Wasps like ants, bees and termites are haplodiploid organisms. In these organisms, females develop from fertilized eggs so there is a male and a female contribution to the genome i. The authors of the paper experimented with two species of wasps, N.
They noticed that when they crossed individuals from different species, only males were produced. In other words, fertilization was not occuring. They found out that this was the result of microorganisms in the cytoplasm of the gametes destroying the males chromosomes from his sperm. Microorganisms had been seen in the cytoplasm of the eggs of these species, but this alone did not prove that they were the cause of the reproductive isolation.
So what they did was feed some wasps food that contained tetracycline, which kills microorganisms, and cross the wasps again.
What they found was, in crosses in which all the microorganisms had been killed, the two species produced both male and female offspring. In crosses where the parents gametes still harbored the microorganisms, only males were produced in interspecific crosses.
Note that intraspecific crosses matings in the same species always produced male and female offspring Therefore they concluded that the microorganisms made it unable for the sperm from a different species of wasp to fertilize the females egg.
This worked bidirectionally N. The microorganisms did not, however, inhibit males and females of the same species from producing offspring of both sexes.
The authors then went on to speculate that microorganism induced reproductive isolation may be a quick way for sympatric speciation to occur.This article directly addresses the scientific evidences in favor of macroevolutionary theory and common descent. It is specifically intended for those who are scientifically minded but, for one reason or another, have come to believe that macroevolutionary theory explains little, makes few or no testable predictions, or cannot be falsified.
acquired trait: A phenotypic characteristic, acquired during growth and development, that is not genetically based and therefore cannot be passed on to the next generation (for example, the large. lausannecongress2018.com examines bioscience issues in biodiversity, environment, genomics, biotechnology, evolution, new frontiers in the sciences, and education.
Includes peer-reviewed articles, class lessons, and educator resources. Articles [Back to top] FitzRoy & Darwin.
A letter, containing remarks on the moral state of Tahiti, New Zealand, &c. South African Christian Recorder. Text Image PDF F Geological notes made during a survey of the east and west coasts of S.
America, in the years , , and , with an account of a transverse section of the Cordilleras of the Andes between Valparaiso and. The Origin and Evolution of Birds is a masterpiece both technically and artistically.
In scholarship and completeness it is of the highest possible level, yet it is easily readable even by non-specialists.
The Origin and Evolution of Birds is an excellent ornithological text. The views on the evolution of Aves are very good. However, where this book is most controversial is the discussion of the origin of birds/5(4).