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About 3.8 billion years ago the first signs of life appeared on earth taking the form of very simple, small, single celled microorganisms. 1.8 billion Years after this, these cells became more and more complex, with the formation of internal structures called organelles, such as mitochondria. Moving 2 billion years further, the first multi-cellular organisms evolved and thus becoming the basis for most life on Earth as we know it today.[Mic09). Ever imagined your ancestor being some cell ‘living’ in an alkali vent somewhere under the ocean? No I didn’t think so.
These organisms then evolved over long periods of time inheriting different features, depending on the environment that they were living in, to form the mammals, reptiles, birds, fish, amphibians and arthropods of the current age. Studying fossils and evolutionary patterns of organisms has allowed us to understand how these organisms have changed over time and why this may have happened. We are also able to acquire some understanding of how humans may have come into being.
It allows us to make sense of ourselves. Evolution has lead there to be a diverse range of multiple different species. Some, if not most of these species however are not currently living in the world today, as you may have noticed. Why? Mainly because of mass extinctions, five mass extinctions, which have taken place at different time periods in the Earth’s life time. These mass extinctions created catastrophic changes to ecosystems all over the world in very short periods of time so causing many of the species living within these ecosystems to become extinct.
We may be currently part of a mass extinction as we speak.
As shocking as it sounds, it may be true and what’s worse is that it’s your fault, well our fault, as a human race. As humans continue to grow and develop their activates and actions may lead to one of the fastest mass extinction ever recorded in history. It is said that the extinction rate is 1,000 – 10,000 times higher than the natural extinction rate.[Dra15] [THE16]Scary figures right. In this essay I will be discussing whether we are in a 6th mass extinction comparing causes, consequences and effects to two previous mass extinctions however frightening they may be. The Earth can be said to be very bio-diverse being the home to millions of different species. Staggering figures of approximately 1.2 million species have been discovered so far to be living on the planet. This is only 14 percent of the total number of species on the Earth according to a new study. The study claims that there is around 8.7 million species most yet still to be discovered. [Tra11]
The number of species and the variety within species and variety between different species is described as biodiversity. You may be thinking why do scientists bother spending time studying biodiversity? Well, biodiversity actually brings many advantages to both the environment and to society and so studying it allows us to take advantage of these benefits. Biodiversity allows essential medicines to be created as genes of certain organisms from the multiple species within an ecosystem can be used to treat deadly and critical diseases. Biodiversity also regulates nitrate and phosphate levels in the soil making it more fertile as well as detoxifying the soil and so improving conditions for growth. This increases the yield for crops as they will be able to grow bigger and healthier and so resulting in more food being produced improving the world food crises. The population of the world is increasing exponentially meaning much higher demands for food. Biodiversity allows this demand to be met. Finally biodiversity brings a balance to ecosystems as ones with high biodiversity are able to cope with more changes and difficulties due to them having a larger gene pool. Certain organisms may be able to survive through certain changes and may be able to adapt to these changes as they have beneficial genes. Biodiversity is much more important than we think, so it needs to be conserved.
Humans are developing day by day and communities are becoming more and more complex. Technology is improving and new advances are being created every second. This all sounds great and is in many ways however with everything, there comes a price. As humans develop, their actions seem to have a very strong effect on the levels of biodiversity. Many different ecosystems and the species living within them are being damaged and destroyed by everyday human activities such as fishing, hunting, farming and deforestation. Humans fish for endangered animals living in oceans and so reducing the number of individuals within that certain species. This may result in the species becoming extinct. Hunting has also lead to the extinction of many animals such as the Caribbean monk seal, Pyrenean ibex and the West African black rhinoceros [Jam13].
Hunting is often done for entertainment and to obtain useful resources but has serious consequences on biodiversity. Deforestation has increased over the last few centuries with the increase in the world population the demand for food and resources has also increased. Forests have been cut down to create paper and other capitol, destroying the habitats for numerous species. These species will therefore die as they have no shelter further reducing biodiversity. Human activities continue to decrease biodiversity at frightening rates. Humans should try to conserve biodiversity not destroy it. If biodiversity continues to decrease then there may be devastating consequences. First, it may lead to an increase in disease meaning that more people will get infected and become ill. There has been increasing evidence showing that greater biodiversity may decrease the spread of many wildlife pathogens to humans and so reducing the number of illnesses. [Bio16][Why05][How] An example would be the spread of Lyme disease which decreases with greater biodiversity. However biodiversity is currently decreasing not increasing and so more diseases are likely to spread to humans. Furthermore economies all around the world are more likely to be affected by natural disasters such as flooding. As biodiversity continues to decrease, the effects of natural disasters seem to be greater on economies, especially those of LEDC countries.
Many people living in rural areas conserve ecosystem diversity as a risk management plan against natural disasters. They use these strategies to create a sustainable livelihood. Biodiversity loss has affected us greatly and may lead to more terrifying consequences if we continue to kill animals and continue to destroy ecosystems. [Why05] Finally we move onto mass extinctions the main topic which you probably have been waiting to read about since the beginning of the essay. A mass extinction is a global extinction of a huge number of species over a very short period of time. [Wha16]There have been 5 mass extinctions recorded to have taken place at different time periods in the Earth’s history. Mass extinctions of the past can be understood by looking at the fossil record and using carbon dating to identify which period of time these mass extinctions took place. Scientists are able to carbon date the sediment above and below the fossils of the extinct organisms giving them a rough idea of how long ago the organism became extinct.
Studying mass extinctions has allowed us to make sense of gaps and patterns found in the fossil record. We are able to understand why certain species became extinct over such a short period of time and which evolutionary consequences this lead to. An example of this is after the 2nd mass extinction when animals in sea’s and oceans migrated onto land and evolved into all of the modern land animals today. We can use information/knowledge of mass extinctions to predict future mass extinctions that may happen and also understand why a mass extinction may be happening so that we can try to stop them from taking place. I will now describe two previous mass extinctions in order to give you an idea of how large and serious a mass extinction is and the factors which may cause it. The first mass extinction I will talk about is the Late Devonian mass extinction. This mass extinction took place 374 million years ago. At this period of time, plants had evolved onto land.[Wha16]
These plants absorbed carbon dioxide in order to carry out photosynthesis. A large amount of carbon dioxide was removed from the atmosphere causing temperatures to fall leading to global cooling.[The16][Ext12][Mic15] This changed the composition of the soil causing it to be washed into oceans and seas. Soil has lots of nutrients within it and so providing food for algae allowing it to thrive. The thriving algae took in oxygen from the oceans and seas for respiration. Due to such low levels of oxygen the fish and sea life suffocated and died leading to the extinction of many species. Also due to global cooling a process called glaciation may have taken place which would have also killed many species. The Cretaceous-Tertiary mass extinction was caused by a different factor. A large asteroid about 10km in diameter collided with the earth in a region now located as Mexico. The collision sent a lot of dust into the atmosphere blocking sunlight and so again creating global cooling. The shockwave from the collision combined with the global cooling killed many species. [Cha13][The161]
Both events caused numerous species to become extinct, increasing the natural extinction rate by an incredible amount and so the reason why they are called mass extinctions. As I have mentioned before, we may be part of a 6th mass extinction and have a guess what the cause may be. No it’s not due to a large asteroid or due to volcanic activity but because of us humans and our actions. We have done many things to potentially cause the 6th mass extinction that this planet has experienced. In this paragraph I will describe a few of these things starting with global warming. We are constantly burning fossil fuels in order to produce electricity and energy. As a result, large amounts of carbon dioxide and other greenhouse gasses are being released into the atmosphere every day. This creates a greenhouse effect which then leads to increases in global warming. Global warming has created incredible climate change affecting ecosystems all over the world. Ecosystems are not able to change/adapt to the constantly changing climates and so the species within them are affected and are likely to die and become extinct. [Jer15] [FIO15]
Secondly when humans travel to different countries they take with them a domestic species or animal to the foreign ecosystem. The animal may disrupt this ecosystem and the species living within it and so causing certain animals to die and therefore become extinct. [Jer15]Thirdly many toxins from nuclear power plants, factories and large industries have leaked into ecosystems especially those in seas and oceans. The toxins have poisoned many animals causing them to die and so causing that species to become extinct [FIO15]. Finally a lot of land/ecosystems have been cleared in order to create space for farming and houses. The world population is increasing, so more food and shelter is required. Ecosystems have been destroyed in order to achieve this and so further increasing the extinction rate. [FIO15]If we do not try to stop or reduce these effects then we may be the cause of the death of millions of species.
So are we currently in a 6th mass extinction? With the extinction rate this high at 100 1000 times higher than the natural extinction rate then I think we may be in one of the fastest mass extinctions ever recorded in history. Is this the work of human actions and activates? Many scientist believe that human activates are the main reasons for the increased extinction rate but others think otherwise. Some scientists believe that global warming is being caused by solar flares from the sum or just from Mother Nature herself, as the hottest periods for the earth was way before humans. One thing we can agree on is that humans are having a large effect on biodiversity and if biodiversity continues to decrease then there may be some horrific consequences. This essay may sound all gloom and doom but on a positive note, look how far ‘life’ has gone from that single celled microorganism 3.8 billion years ago to the many complex multi-cellular organisms of the current day.
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