What is the scientific theory of how life came to earth?

Question

I was thinking that maybe life came from an asteroid, but im not sure.

Answer 1

In biology, evolution is the change from generation to generation in a population's inherited characteristics, or traits. Minor random changes in the genes that encode these traits produces new traits, and variations on old ones, within every generation. While random chance can intervene and cause even the most beneficial trait to be lost, organisms with traits that help them to survive and reproduce tend to have more offspring. In doing so, they will pass more copies of these beneficial traits on to the next generation, leading, on average, to advantageous traits becoming more common in each generation, while disadvantageous traits become rarer. Given enough time, this passive process result in varied adaptations to changing environmental condition Furthermore, because newly discovered beneficial traits are conserved (for as long as they remain

beneficial), natural selection allows for the gradual accumulation

of improvements which continuously build upon each other, potentially resulting in very high levels of optimisation over time. As differences in and between populations accumulate, new species can evolve from prior ones. All known species are descended from a single ancestor through this process of gradual divergence

The theory of evolution by natural selection was first put forth in detail in Charles Darwin's 1859 book On the Origin of Species. In the 1930s, Darwinian natural selection was combined with Mendelian inheritance to form the modern evolutionary synthesis.[4] With its enormous explanatory and predictive power, this theory has become the central organizing principle of modern biology, providing a unifying explanation for the diversity of life on earth

Fossils are critical evidence for estimating when various lineages originated. Since fossilization of an organism is an uncommon occurrence, usually requiring hard parts (like teeth, bone, or pollen), the fossil record provides only sparse and intermittent information about ancestral lineages.[35]

The fossil record provides several types of data important to the study of evolution. First, the fossil record contains the earliest known examples of life itself, as well as the earliest occurrences of individual lineages. For example, the first complex animals date from the early Cambrian period, approximately 520 million years ago. Second, the records of individual species yield information regarding the patterns and rates of evolution, showing whether, for example, speciation occurs gradually and incrementally, or in relatively brief intervals of geologic time. Thirdly, the fossil record is a document of large-scale patterns and events in the history of life. For example, mass extinctions frequently resulted in the loss of entire groups of species, while leaving others relatively unscathed. Recently, molecular biologists have used the time since divergence of related lineages to calibrate the rate at which mutations accumulate, and at which the genomes of different lineages evolve.

Phylogenetics, the study of the ancestry of species, has revealed that structures with similar internal organization may perform divergent functions. Vertebrate limbs are a common example of such homologous structures. The appendages on bat wings, for example, are very structurally similar to human hands, and may constitute a vestigial structure. Vestigial structures are idiosyncratic anatomical features such as the panda's "thumb", which indicate how an organism's evolutionary lineage constrains its adaptive development. Other examples of vestigial structures include the degenerate eyes of blind cave-dwelling fish, and the presence of hip bones in whales and snakes. Such structures may exist with little or no function in a more current organism, yet have a clear function in an ancestral species. Examples of vestigial structures in humans include wisdom teeth, the coccyx and the vermiform appendix.

These anatomical similarities in extant and fossil organisms can give evidence of the relationships between different groups of organisms. Important fossil evidence includes the connection of distinct classes of organisms by so-called "transitional" species, such as the Archaeopteryx, which provided early evidence for intermediate species between dinosaurs and birds,[36] and the recently-discovered Tiktaalik, which clarifies the development from fish to animals with four limbs.


Molecular evidence
By comparing the DNA sequences of species, we can discern their evolutionary relationships. The resultant phylogenetic trees are typically congruent with traditional taxonomy, and are often used to either strengthen or correct taxonomic classifications. Sequence comparison is considered a measure robust enough to be used to correct erroneous assumptions in the phylogenetic tree in instances where other evidence is scarce. For example, neutral human DNA sequences are approximately 1.2% divergent (based on substitutions) from those of their nearest genetic relative, the chimpanzee, 1.6% from gorillas, and 6.6% from baboons.Genetic sequence evidence thus allows inference and quantification of genetic relatedness between humans and other apes.The sequence of the 16S rRNA gene, a vital gene encoding a part of the ribosome, was used to find the broad phylogenetic relationships between all extant life. This analysis, originally done by Carl Woese, resulted in the three-domain system, arguing for two major splits in the early evolution of life. The first split led to modern bacteria, and the subsequent split led to modern archaea and eukaryotes.

Since metabolic processes do not leave fossils, research into the evolution of the basic cellular processes is done largely by comparison of existing organisms. Many lineages diverged when new metabolic processes appeared, and it is theoretically possible to determine when certain metabolic processes appeared by comparing the traits of the descendants of a common ancestor or by detecting their physical manifestations. As an example, the appearance of oxygen in the earth's atmosphere is linked to the evolution of photosynthesis.

The proteomic evidence also supports the universal ancestry of life. Vital proteins, such as the ribosome, DNA polymerase, and RNA polymerase, are found in everything from the most primitive bacteria to the most complex mammals. The core part of the protein is conserved across all lineages of life, serving similar functions. Higher organisms have evolved additional protein subunits, largely affecting the regulation and protein-protein interaction of the core. Other overarching similarities between all lineages of extant organisms, such as DNA, RNA, amino acids, and the lipid bilayer, give support to the theory of common descent. The chirality of DNA, RNA, and amino acids is conserved across all known life. As there is no functional advantage to right- or left-handed molecular chirality, the simplest hypothesis is that the choice was made randomly by early organisms and passed on to all extant life through common descent. Further evidence for reconstructing ancestral lineages comes from junk DNA such as pseudogenes, "dead" genes which steadily accumulate mutations.

There is also a large body of molecular evidence for a number of different mechanisms for large evolutionary changes, among them: genome and gene duplication, which facilitates rapid evolution by providing substantial quantities of genetic material under weak or no selective constraints; horizontal gene transfer, the process of transferring genetic material to another cell that is not an organism's offspring, allowing for species to acquire beneficial genes from each other; recombination, capable of reassorting large numbers of different alleles and of establishing reproductive isolation; and endosymbiosis, the incorporation of genetic material and biochemical composition of a separate species, a process observed in organisms such as the protist hatena and used to explain the origin of organelles such as mitochondria and plastids as the absorption of ancient prokaryotic cells into ancient eukaryotic ones.

Answer 2

That is one of the theories

Life may have came from an asteroid or comet but the chances of life surviving atmospheric entry temperatures is highly unlikely unless it was deep within a comet or asteroid.

The other theory is that the sea was a broth of the building blocks of life and electrical sparks (lightening) can set off a sort of chain reaction.

We know that lipid formations are found in nature, similar to the phospholoipid bi layer found around cells, however they are not living cells. It has also been found that these lipid balls can engulf reactions and contain them but again they are not living cells.

The theory is that,along with, or as bacteria, organnelles such as chloroplasts and mitochondria formed and existed long before what we know as cells and that these were engulfed by a lipid bi layer ball and it contained them and formed the first eukaryotic cells. if the organelles contained in the lipid ball were beneficial it is possible that they could replicate themselves and the lipid bi layer containing them.

comically It is also strongly believed that many unsuited organneles were engulfed together and that it took many millions of attempts to get the mix right and that all these little lipic bi layer balls were popping all over the place inside the worlds oceans.

Hope this gives you an insight into ur beginnings

Answer 3

The Big Bang Theory.

http://liftoff.msfc.nasa.gov/academy/universe/b_bang.html
http://en.wikipedia.org/wiki/Big_Bang

Answer 4

in case you think of the fossil information proves the concept of evolution, you haven't any longer studied the fossil checklist. It would not combination via ingenious small-step evolution. It exhibits that different creatures seem completely formed over billions of years, via fact the earth and atmosphere substitute, and proceed to be especially much unchanged till extinction. The fossil checklist would desire to be sufficient to discredit the concept of evolution.

Answer 5

what you are referring to is panspermia, I believe that life on this earth probably originated through a process taking billions of years in just the right environmental conditions for life to take hold and flourish but panspermia is also another possibility.