Changes in the Atmosphere Causing Multicellularity
About 2.5 billion years ago, oxygen began slowly to accumulate in the atmosphere, as a result of the photosynthetic activity of the cyanobacteria.
Those prokaryotes that were able to use oxygen in ATP production gained a strong advantage, and so they began to prosper and increase. Some of these cells may have evolved into modern forms of aerobic bacteria. Other cells may have become symbionts with larger cells and evolved into mitochondria. As the amount of oxygen and other atmospheric gasses increased, they started blocking out deadly
u.v. rays from the sun. The sun’s rays made life outside of water nearly impossible. These changes made life on land possible and evolution occurred as prokaryotes gave rise to land living eukaryotes.
The microfossil record indicates that the first eukaryotes evolved at least
1.5 billion years ago. Eukaryotes are distinguished from prokaryotes by their larger size, the separation of nucleus from cytoplasm by a nuclear envelope, the association of DNA with histone proteins and its organization into a number off distinct chromosomes, and complex organelles, among which are chloroplasts and mitochondria. Scientists believe that eukaryotic organisms such as the protists evolved from the prokaryotes. There are two main theories which describe how this transition may have occurred. The first is the endosymbiotic theory, or enosymbiosis, and the other is the autogenous theory, or autogenisis. These two theories are not mutually exclusive, meaning one or the other could account for different parts of eukaryotic cells. The endosymbiotic theory states that the formation of eukaryotic cells were symbiotic associations of prokaryotic cells living inside larger prokaryotes. The endosymbiotic hypothesis accounts for the presence in eukaryotic cells of complex organelles not found in the far simpler prokaryotes. Many modern organisms contain intracellular symbiotic bacteria, cyanobacteria, or photosynthetic protists, indicating that such associations are not difficult to establish and maintain. Endosymbiosis is said to be responsible for the presence of chloroplasts and mitochondria in eukaryotes.
Autogenisis, the alternative to the endosymbiotic theory is specialization of internal membranes derived originally from the plasma membrane of a prokaryote.
Autogenisis could be responsible for structures like the nuclear membrane and endoplasmic reticulum in eukaryotes.
There are two scenarios for which multicellularity may have occurred. The first is unicellular organisms came together to form a colonial organism, then
Knoll, Andy "The Planet ary Context of Biological Evolution" Lead Teams Online. NASA Astrobiology Institute 2Apr 2003
Since Woese’s research, Archaea have been divided into two main phyla, the Eutyarchota and Crenarchaeota, with the majority being extremophiles. This supports the hypothesis that Eubacteria and Archaea had a thermophilic common ancestor that was able to tolerate the hot conditions on Earth. Nelson et al (1999) also found that Thermotoga maritima bacteria had 24% genes of archaeal origin when analysed, supporting the theory of Thermatoga’s early branching from Archaea in the Tree of Life.
Eukaryotic cells share several distinguishing features, such as: cytoplasm within specialized organelles such as the mitochondria, chloroplast, the Golgi complex, both a rough and smooth endoplasmic reticulum, a nuclear envelope that isolates DNA from the cytoplasm, and a endomembrane system that provides structure and function to the organelles of the cell. Both the mitochondrion and chloroplast are energy transducing organelles, meaning that they transform energy from one form to another, and are believed to be evolved from free living prokaryotes as held by the theory of endosymbiosis. This theory suggests that infolding of the plasma membrane coupled with the absorption of a prokaryotic cells by other prokaryotes could evolve into a later, more complex and specialized type of cell and is proofed by related morphological features such as between cytobacteria and chloroplasts, and between mitochondria and aerobic prokaryotes. Further substantiation includes mitochondria and chloroplasts reproduction through binary fission like prokaryotes, the presence of DNA in both free living prokaryotes and in energy transducing organelles (apart from in the nucleus), protein synthesis and the presence of enzymes and ribosomes where the ribosomes of prokaryotes are comparable to those in mitochondria and chloroplast,
The Intergovernmental Panel on Climate Control (IPCC) was established in 1988, reported in 2007 in “very high confidence” that since 1750 human activity has played a major part in overloading the atmosphere with carbon dioxide. Whether it’s through cellular respiration or the burning of fossil fuels is debatable. Cellular respiration is a process of creating energy and it takes place in all living things, even in plants. Carbon dioxide, oxygen, light and water are important factors in this process. Keeping a balance level of carbon dioxide is crucial to the earth’s atmosphere, because if it gets too high, it increases the average temperature on earth, which is unfortunately what we are dealing with and call “global warming”. I believe cellular respiration does not affect global warming as greatly as industrial fossil fuels do.
[7] Rothschild, Lynn J. “The Influence of UV Radiation on Protistan Evolution.” Journal of Eukaryotic Microbiology (1999), Issue 46 no. 5 pg. 548-555.
Since the beginning billions of years ago when God reached down and fused the base elements of life into a single-cell organism, that's how long this process has been taking place. As the amoeba of life spread to different parts of a world that was just beginning to take shape, it encountered different challenges for survival, the cells that couldn't survive died and the one or two mutated cells that could survive continued, multiplying and dominating each particular environment.
I. Photosynthetic organisms are those that convert the sun’s energy through a process called photosynthesis. They are also referred to as autotrophs. These organisms include plants, algae, and bacteria. These organisms take energy from the sun and water. They then complete the steps of photosynthesis and produce oxygen and glucose.
Cyanobacteria are one of the largest and most important groups of bacteria on the earth. Often called ‘the blue-green algae’ Cyanobacteria is in fact, not an algae at all. Algae are eukaryotic, whereas cyanobacteria, is a bacteria, and is prokaryotic. The name algae is used to refer to any aquatic organisms capable of photosynthesis, so the term is considered general, though in this case, inaccurate. Being tiny and normally unicellular, cyanobacteria grow in large colonies, making them visible to the human eye, and often dominate aquatic habitats such as shorelines. Over their 3.5 billion year reign, Cyanobacteria have helped to successfully establish the earth’s atmosphere, making it possible for human life forms to thrive and some of the oldest known fossils in the world are cyanobacteria, earning it the title of one of the great survivors of all time.
According to the theory of evolution, approximately 3.8 billion years ago some chemicals accidentally structured themselves into a self-replicating molecule. This beginning spark of life was the ancestor of every living thing we see today. Through the processes of mutation and natural selection, that simplest life form, has been shaped into every living species.
“Evolution as a whole seems to explain variation of life, but it doesn’t explain where the first living thing came from!” Yes that’s absolutely true. Evolution does not explain where living things originated. It’s not supposed to. Evolution explains how living organisms have changed over the course of time. The origins of life on Earth from non-life are in a separate field of study called Abiogenesis. Abiogenesis is still merely a hypothesis and has not yet reached the status of a scientific theory such as evolution has. It could have started from self-replicating RNA, or amino acids, or proteins, or Yahweh, or Allah, or Zeus, or Panspermia, or aliens. We do not have the evidence yet to say how life originally started. Scientists have been on the search for evidence to show how life began.
The oldest known photosynthesisers were small aquatic bacteria, such as cyanobacteria and Halobacterium halobium. Biomarkers indicate organisms similar to cyanobacteria were present 2.7 billion years ago [5], and other archaeological fossils have been shown as evidence of photosynthesis at this early stage of Earth’s development. Cyanobacteria, like modern plants, use the energy of the sun to power their photosynthesis, and can photosynthesise in both aerobic and anaerobic conditions. [6] Cyanobacteria were one of the first organisms to produce oxygen. This newly produced oxygen was toxic to a majority of the other species of organism at the time, causing extinction. It was also responsible for the production of an ozone atmosphere [7].
Living things like vertebrates and invertebrates were appeared on earth. The multi cellular organism start to evolve from that. The plants could only live in the sea at first but as the time passes they evolve and start to appear on the shore side of the sea and lakes. After that they start to appear on the land. Slowly the animals on sea were evolved like fish and other. All the animals first evolved on sea and then later on land. The evolution started in both land and water. Big sharks and fishes ruled the sea and the land was covered by vegetation. The tall trees and other fungi covered the land. Soon after that the animals on earth start to evolve too. animals and insects ruled the
...o happen. But with the help of fossil evidence we are able to identify common ancestors and evolutionary pathways between species. We also identify oxygen as a major key contribution for life to evolve. Also, through scientific research it has been established that arthropods and chordates have shared genes, leading to the path of vertebrates and human life.
Climatology is described as the study of the origins and impacts of climate. To understand climatology, one must know the true definition of climate. Climate, simply, is the typical weather of a specific geographical region on earth. Climate can be affected by many factors. Some of these factors consist of: pollution, outgassing of volcanoes, seasonal changes, natural disasters, and carbon dioxide emissions, and greenhouse gasses. Ultimately, these factors lead to a phenomenon called climate change. Pollution, carbon dioxide emissions and the trapping of greenhouse gasses are most known for drastically changing earth's climate over the years. Carbon dioxide alone plays a key role in heating up the atmosphere. It alone combined with other greenhouse
Global Environmental change also known as global warming has been a rising concern for a while. The International Panel on Climate Change states that Environmental change is anthropogenic. The World Health organization defines anthropogenic climate change a cause of human and human activity. Major causes of environmental change throughout the world are the increase in Carbon dioxide and greenhouse gases.1 In the past when looking at environmental change the main focus has been on the environment and the ozone layer of the earth, but climate change has a very immense effect on human health. This paper specifically looks at how global environmental change has an effect on the health of people residing in Canada. In the past decade the global environmental change has increased Canada’s weather temperature 1.6 degrees Celsius.2 With climate change it said that in Canada there would be a greater spread of infectious disease. Another factor that can affect human health due to climate change is extreme weather events.