LYNN MARGULIS TEORIA ENDOSIMBIOTICA PDF

Endosymbiosis: Lynn Margulis Margulis and others hypothesized that chloroplasts bottom evolved from cyanobacteria top. The Modern Synthesis established that over time, natural selection acting on mutations could generate new adaptations and new species. But did that mean that new lineages and adaptations only form by branching off of old ones and inheriting the genes of the old lineage? Some researchers answered no.

Author:Nikozilkree Yogis
Country:Dominica
Language:English (Spanish)
Genre:Video
Published (Last):13 October 2012
Pages:448
PDF File Size:5.33 Mb
ePub File Size:10.22 Mb
ISBN:599-6-58089-724-6
Downloads:3553
Price:Free* [*Free Regsitration Required]
Uploader:Votaur



Endosymbiosis: Lynn Margulis Margulis and others hypothesized that chloroplasts bottom evolved from cyanobacteria top. The Modern Synthesis established that over time, natural selection acting on mutations could generate new adaptations and new species. But did that mean that new lineages and adaptations only form by branching off of old ones and inheriting the genes of the old lineage? Some researchers answered no.

Evolutionist Lynn Margulis showed that a major organizational event in the history of life probably involved the merging of two or more lineages through symbiosis. In the late s Margulis left studied the structure of cells. Mitochondria, for example, are wriggly bodies that generate the energy required for metabolism. To Margulis, they looked remarkably like bacteria. She knew that scientists had been struck by the similarity ever since the discovery of mitochondria at the end of the s.

Some even suggested that mitochondria began from bacteria that lived in a permanent symbiosis within the cells of animals and plants. There were parallel examples in all plant cells.

Algae and plant cells have a second set of bodies that they use to carry out photosynthesis. Known as chloroplasts , they capture incoming sunlight energy.

The energy drives biochemical reactions including the combination of water and carbon dioxide to make organic matter. Chloroplasts, like mitochondria, bear a striking resemblance to bacteria. When one of her professors saw DNA inside chloroplasts, Margulis was not surprised.

Margulis spent much of the rest of the s honing her argument that symbiosis see figure, below was an unrecognized but major force in the evolution of cells. In she published her argument in The Origin of Eukaryotic Cells. Mitochondria are thought to have descended from close relatives of typhus-causing bacteria. The genetic evidence In the s scientists developed new tools and methods for comparing genes from different species.

The DNA in mitochondria, meanwhile, resembles that within a group of bacteria that includes the type of bacteria that causes typhus see photos, right. Margulis has maintained that earlier symbioses helped to build nucleated cells.

For example, spiral-shaped bacteria called spirochetes were incorporated into all organisms that divide by mitosis. Tails on cells such as sperm eventually resulted. Most researchers remain skeptical about this claim. It has become clear that symbiotic events have had a profound impact on the organization and complexity of many forms of life.

Algae have swallowed up bacterial partners, and have themselves been included within other single cells. Nucleated cells are more like tightly knit communities than single individuals. Evolution is more flexible than was once believed. Phylogenetic analyses based on genetic sequences support the endosymbiosis hypothesis.

INTOXICACION POR GRAMOXONE PDF

Endosimbiosis seriada

A principios del siglo XX, en , el ruso Kostantin S. Javier Sampedro, Deconstruyendo a Darwin. Los trabajos de Merezhkovsky pasaron inadvertidos. Para Lynn Margulis, tal variedad revela las dificultades a las que las bacterias se tuvieron que enfrentar y su capacidad para aportar soluciones a esas dificultades.

6ES7 216 2AD23 0XB0 PDF

Lynn Margulis

Los cloroplastos y las mitocondrias poseen en su interior ribosomas y estos exhiben los rasgos de los ribosomas descritos en las eubacterias. Las secuencias del ADN de las mitocondrias son marcadamente parecidas a las secuencias encontradas en un grupo puntual de bacterias denominadas alfa-proteobacterias. Los estudios comparativos basados en filogenias moleculares lograron trazar el origen de los genes codificados por los plastidios de las plantas hasta las cianobacterias. Estos plastidios secundarios se caracterizan por la presencia de membranas adicionales, es decir, una o dos membranas extras a las dos membranas que usualmente rodean a la organela. Referencias Anderson, P.

CHARLES DICKENS SZP REMNYEK PDF

Lynn Margulis: BiografĂ­a y Aportaciones

.

Related Articles