Lesson 6- The Evolution of Cells, Organisms, and Microorganisms
There are three theories of the origin of life on Earth. The first is that it arrived in the form of extraterrestrial sources; the other is that it originated as a heterotroph, and the last that is originated as an autotroph. We had scientist explore this theories of life and find evidence of how the life started on Earth. But till this day do we really know how life was started we can only go off the evidence that we read about in book.
There is yet no evidence to support or contradict panspermia; although the majority view holds that panspermia especially in its form is unlikely given the challenges of survival and transport in space. There are also important issues of the atmosphere, and may be responsible for epidemic outbreaks, new diseases, and the genetic novelty necessary for macroevolution. Panspermia does not ...view middle of the document...
One new twist to the hypothesis is that it proposes that plasmodia magnetic fields ejected from the magnetosphere may move the few spores lifted from the Earth’s atmosphere with sufficient speed to cross interstellar space to other systems before the spores can be destroyed. Then transfer of material is well documented, as evidenced by meteorites of Martian origin found on Earth.
Space travel may also be a way of transport mechanism for cross-pollination in our solar system or even beyond. However, space agencies have implemented sterilization procedures to avoid planetary contamination.
In experiments, scientists have showed that the electrical discharges of lightning, radioactivity, and ultraviolet light caused the elements in the early Earth atmosphere to form the basic molecules of biological chemistry, such as nucleotides, simple proteins, and ATP. It seems likely, then, that the Earth was covered in a hot, thin soup of water and organic materials. Over time, the molecules became more complex and began to collaborate to run metabolic processes. Eventually, the first cells came into being, These cells were heterotrophy, which could not produce their own food and instead fed on the organic material from the primordial soup. (this heterotrophy gives this theory its name).
The anaerobic metabolic processes of the heterotrophy released carbon dioxide into the atmosphere, which allowed for the evolution of photosynthetic autotrophy, which could use light and CO2 to produce their own food. The autotrophy released oxygen into the atmosphere. For most of the original anaerobic heterotrophy, oxygen proved poisonous. The few heterotrophies that survived the change in environment generally evolved the capacity to carry out aerobic respiration. Over the subsequent billions of years, the aerobic autotrophy and heterotrophy became the dominant life-forms on the planet and evolved into allof the diversity of life now visible on Earth.
Concepts in Biology (2008) Svante Arrhenius, I quoted him on the Panspermia information.