Succession, Habitat, Microhabitat and Niche PDF

AECC -1/OSOU Succession Interacting populations of community are characterized by continuous death and replacement and usually by immigration and emigration (one way movement from home range to other habitat) of their individuals. In this way, composition and shape of community remains in changing...

AECC -1/OSOU Succession Interacting populations of community are characterized by continuous death and replacement and usually by immigration and emigration (one way movement from home range to other habitat) of their individuals. In this way, composition and shape of community remains in changing state. The changes in the community go on taking place until a complete balance is established between community and environment. This is called succession. At complete equilibrium state a stable community is established which is called climax community. In the climax community very little or no change in the shape can be anticipated over a long period of time. Thus with the change in the environment the composition of community also tends to change. The sequence of communities showing a gradual change in composition is called continuum. Community in such a gradient can be recognized as a discrete point with uniform floristic composition in the continuum. Eco-tone In nature, there is no sharp line to indicate the end of one community and the beginning of another community. When two communities are adjacent, there is a zone of transition between them where the species of the two communities intermingle. The transition or marginal zone between two major communities presenting a situation of special ecological interest is called an eco-tone or transition zone. The transition zone between grassland and forest or the intermediate zones between any two major lands or aquatic communities are the examples of eco-tone. Strictly speaking, a transition zone is an eco- tone only if tension exists between the bordering communities. The eco-tone is colonized by the species that are commonly found in the communities on both the sides, as well as by some versatile species of plants and animals. As a rule, the eco-tone contains more species and often denser populations than the bordering communities. This is known as ‘principle of edges’. This edge effect is chiefly due to wider range of suitable environmental conditions. 5.6 HABITAT, MICROHABITAT AND NICHE Habitat refers to a specific place where a species normally lives. For example, habitat of a tiger is the forest, of a shark is the sea, and of Plasmodium are the red blood cells. More than one animal or plant may live in the same habitat. For example, tiger, deer, wolf, fox, lion, etc. may be found in the same forest. Animals exhibit habitat specificity and require specific environmental conditions to live. For example, a fish lives in an aquatic habitat, but a river fish can live only in freshwater, while a sea fish can live only in a marine habitat. Some organisms are more tolerant than the other. A habitat can be subdivided into regions with different environmental conditions. These subdivisions are called microhabitat. For example, in a pond, some organisms are surface dwellers while some others are bottom dwellers. For a species to maintain its population, its individuals must survive and reproduce. Certain combinations of environmental conditions are necessary for individuals of each species to tolerate the physical environment, obtain energy and nutrients and avoid predators. The total requirements of a species, i.e. resources and physical conditions determine where it can live and how abundant it can be at any one place within its range. These requirements are termed abstractly as the ecological niche. In other words, niche is a term used to indicate not only the habitat but also the role played by the organisms in the environment. 117  AECC -1/OSOU Hutchinson suggested that the niche could be modelled as an imaginary space with many dimensions, in which each dimension or axis represents the range of specific environmental condition or resource that is required by the species. Thus, the niche of a plant might include the range of temperatures that it can tolerate, the intensity of light required for photosynthesis, specific humidity regimes and minimum quantities of essential soil nutrients for uptake. A habitat possesses many niches and supports many species. An organism changes its niches as they develop. For example, the common toad, Bufobufo occupies the aquatic environment when it is a tadpole and feeds on algae and detritus. But after it metamorphosis’s into an adult it becomes terrestrial and becomes insectivorous. According to Odum, while the habitat is the organisms ‘address’, its ecological niche is its ‘profession’. Two organisms may be found in the same habitat, but do not occupy the same ecological niche. Each plays a different role in its habitat. Different animals that occupy similar ecological niche in different geographical regions are called ‘ecological equivalents’. 5.7 LET US SUM UP  In exponential growth, a population's per capita (per individual) growth rate stays the same regardless of population size, making the population grow faster and faster as it gets larger.  In nature, populations may grow exponentially for some period, but they will ultimately be limited by resource availability.  In logistic growth, a population's per capita growth rate gets smaller and smaller as population size approaches a maximum imposed by limited resources in the environment, known as the carrying capacity (KKK).  Exponential growth produces a J-shaped curve, while logistic growth produces an S- shaped curve.  In nature, population size and growth are limited by many factors. Some are density- dependent, while others are density-independent.  Density-dependent limiting factors cause a population's per capita growth rate to change—typically, to drop—with increasing population density. One example is competition for limited food among members of a population.  Density-independent factors affect per capita growth rate independent of population density. Examples include natural disasters like forest fires.  Limiting factors of different kinds can interact in complex ways to produce various patterns of population growth. Some populations show cyclical oscillations, in which population size changes predictably in a cycle. 5.8 MODEL QUESTIONS SHORT ANSWER TYPE QUESTIONS 1. Define population? 2. What are the different parameters of population? LONG ANSWER TYPE QUESTIONS 118  AECC -1/OSOU 1. How can be the population parameters are measured. 2. How does the population grow? How its growth is regulated? 5.9 REFERENCES 1. N.A. Croll et al., “The Population Biology and Control of Ascarislumbricoides in a Rural Community in Iran.” Transactions of the Royal Society of Tropical Medicine and Hygiene 76, no. 2 (1982): 187-197. 2. Martin Walker et al., “Density-Dependent Effects on the Weight of Female Ascarislumbricoides Infections of Humans and its Impact on Patterns of Egg Production.” Parasites & Vectors 2, no. 11. 3. David Nogués-Bravo et al., “Climate Change, Humans, and the Extinction of the Woolly Mammoth.” PLoSBiol 6 (April 2008): e79. 4. G.M. MacDonald et al., “Pattern of Extinction of the Woolly Mammoth in Beringia.” Nature Communications 3, no. 893 (June 2012). 5. Rogers, R.L, and Slatkin, M., "Excess of genomic defects in a woolly mammoth on Wrangel island." PLoS Genetics 13(3) (2017): e1006601. 119  AECC -1/OSOU UNIT-6 POPULATION GROWTH AND CONTROLS Structure: 6.1 Learning Objectives 6.2 Introduction 6.3 Population density 6.4 Characteristics of Population in India 6.5 Control methods of human population 6.6 Urbanizations and its effect on human society 6.7 Causes of Urbanisation 6.8 Effects of Urbanisation 6.9 Let Us Sum Up 6.10 Model Questions 6.11 References 6.1 LEARNING OBJECTIVES After going through this unit, you will be able to  Explain optimum control of the population density and its role in improving the quality of life.  Understand the need to achieve a stable population at a level consistent with the requirements of sustainable economic growth.  Understand different methods or factors responsible in controlling population growth,  Understand the impact of urbanisation on society.  Understand the effects of urbanisation. 6.2 INTRODUCTION The word population has its origin in the Latin word populous meaning people. Population defined as a group of individuals of a particular species occupying a particular area at a specific time. The population of a species commonly arises as a result of reproduction. Many animal populations have built-in behavioural mechanisms-with-which they restrict their population size. Human populations do not have such mechanisms. In primitive and ancient civilizations, some social practices, such as religious human sacrifice, cannibalism, tribal war, restraining from sexual things to do for few months after child birth and large- scale infant mortality prevent population growth to a massive extent. But in modern societies these practices have been stopped and because of proper medical care, the infant mortality has been considerably reduced. Since the number of children born was proportional to the size of the population, the increase of population in every year became greater than in the previous year, and gradually the total human population assumed 120  AECC -1/OSOU massive proportions. All nations are committed in achieving a higher standard of living for their people—adequate food, good health, literacy, education, and gainful employment. Populations are characterized with such traits as dispersion, fluctuation in numbers, birth rate, death rate etc. The current population of India is at 132.42 crores (as of 2016) and is the second highest in the world. Population growth is determined by the annual growth rate, which is calculated in percent per annum. Like, if there is an increase of two people per 100 people of the population, then the annual growth rate would be 2%.The high population growth rate is associated with lack of education, and prevalence of poverty. Increased population means more requirements of clothes, food, housing and other facilities. Hence increased population puts a lot of strains on the resources of the world. Since all the human requirements like food, fodder etc., are to be raised from the-land, the pressure to produce more food from unit area of land increases and it brings lot of strain on the ecosystem. Besides, we dig out coal, petroleum, iron, copper and so on from the earth and all of the substances will be exhausted within a restricted number of years. The exhaustion time is reduced as the population is increasing and their demand on these resources also increasing. 6.3 POPULATION DENSITY The uneven population distribution is caused by the country's varying population density. Population density = the total number of people per unit of area. In addition, population density depends mainly on the geographical location and geological factors. Therefore, States like Assam, Himachal Pradesh and other hilly terrains have a reduced population density and the northern plains and coastal areas like Kerala, West Bengal, and Maharashtra have a very high population density. Another important aspect of population study is the change in population. This is largely influenced by three main factors like birth, death, and migration of people in a given year.  Birth rate: The number of children born per 1000 people in a year  Death rate: The number of people died per 1000 people in a year. The birth rate in India has always been higher than the death rate, which is a major reason for population growth. Migration is the third and one of the most significant variables in demographic change. Migration can be internal (between states) and international (between countries). While internal migration does not alter the population change, it affects the density of population in the migrated areas. 6.4 CAHARACTERISTICS OF POPULATION IN INDIA Age Composition One of the most significant characteristics of populations is the age composition that determines the social and economic structure of the country. The total population is divided into three age groups-  Children- below 15 years  Working-age- 15- 59 years  Aged (Senior)- 59 years and above 121  AECC -1/OSOU Adolescent population It is among significant and influential element of the age composition aspect of the population. Adolescents are people in our country in between the age groups of 10-19 years. Approximately one-fifth of the population include adolescent individuals. They are particularly important for future. Sex Ratio The population sex ratio is determined by the number of females for every 1000 males. This helps in understanding the male and female equality in society, thus giving an idea of the nation’s culture. India’s sex ratio has always been on the lower side, until recently. States like Kerala and Union Territory of Pondicherry have higher sex ratio than the major States. Literacy Rate This is another significant feature of the population because a country’s literacy rate determines its economic structure and growth. Literacy, according to the 2001 Census is the ability of a 7 year old person to read and write in any language. The census shows the Indian population’s literacy rate is nearly74.04% (2016). Occupational Structure The number of people in a population involved in different economic activities helps to assess the growth of the country’s economy. The occupational structure is the population distribution across various occupations. This is an important part of the India’s population. The work structure has three wide categories-  Primary occupation- agriculture, fishing, mining, animal husbandry, forestry etc.  Secondary occupation- manufacturing, building, construction work etc.  Tertiary occupation- communication, transportation, administration etc. 6.5 CONTROL METHODS OF HUMAN POPULATION India’s population is quite large and growing rapidly. One percent growth rate implies an addition of 1 cores people every year but actually speaking 2 cores persons are being adding every year. The need for the hour is therefore efficient population control measures. We understand birth rates are mainly responsible for fast development of the population growth. Hence measures which can reduce the birth rate should be adopted. These measures can be classified into 3 heads. A. Social measures B. Economic measures C. Other measures A. Social measures Explosion of population is a social issue that is deeply rooted in society. So efforts must be done to eliminate these social evils in the country. 1. Minimum age of marriage: As fertility depends on the age of marriage, so the minimum age of marriage should be raised. In India minimum age for marriage is 21 122  AECC -1/OSOU years for males and the law has set 18 years for females. This law should be firmly enforced and publicity should also be made to the people. 2. Raising the status of women: There is still discrimination to the women. They are restricted to four walls of house. They are still restricted to children’s rearing and bearing. So women should be given opportunities to develop themselves socially and economically. Free education should be given to them. 3. Spread of education: The spread of education changes the perspective of people. The educated people prefer to delay marriage and adopt small family norms. Educated females are aware of health and avoid frequent pregnancies, thereby helping to lower the birth rates. 4. Adoption: Some parents do not have any child, despite costly medical treatment. It is advisable that they should adopt orphan children. It will be beneficial to both orphan children and children’s couples. 5. Change in social outlook: Social perspective of the people should be changed. Marriage should no longer be considered a binding social relationship. It should not be looked down on isolated females. 6. Social security: Under-social security schemes should cover more and more people, so that they will not be dependent on others in the event of old age, sickness, and unemployment etc. With these facilities they will have no desire for more children. B. Economic Measures The following are the economic measures: 1. More employment opportunities: The first and foremost measure is to increase both rural as well as urban areas job opportunities. There is disguised unemployment in rural areas. So efforts should be made to migrate unemployed persons from rural to urban area. This step can monitor the population growth. 2. Development of agriculture and industry: If agriculture and industry are developed properly, there will be employment for large number of people. They would improve their standard of living and adopt small family norms when their revenue is increased. 3. Standard of living: Improved in standard of living improved which acts as a deterrent to large family norm. In order to maintain their higher standard of living people prefer to have a small family. According to A.K. Das Gupta those who earn less than Rs. 100 per month have on the average a reproduction rate of 3.4 children and those who earn more than Rs. 300 per month have a reproduction rate of 2.8 children. 123  AECC -1/OSOU 4. Urbanization: It is recorded that people in urban areas have low birth rate as compared to those living in rural areas. Therefore urbanization should be encouraged and promoted. C. Other measures 1. Late marriage: Marriage should be solemnized at the age of 30 years as far as possible. This will decrease the reproductive period among the females which will reduce the birth rate. 2. Family planning: This method involves choosing the family not by chance. People can control birth rates by implementing preventive measures. This method is widely used, success of this method depends on the availability of cheap birth control contraceptive devices. 3. Recreational facilities: Birth rates are probable to drop if there are distinct recreational facilities such as cinema; theatre, sports and dance etc. are available to the people. 4. Publicity: Communication media such as T.V., radio and newspaper are the right way to spread the benefits of the planned family to the uneducated and illiterate people, particularly in rural and backward areas of country. 5. Incentives: The govt. showed provide various types of incentives to the people to take birth control measures. It is possible to extend monetary incentives and other amenities such as leave and promotion to the working class that adopts small family standards. 6.6 URBANIZATIONS AND ITS EFFECT ON HUMAN SOCIETY What is Urbanisation? Urbanization is the extent to which urban character or nature increases. It can refer to a geographical region that combines urban and rural areas, or to transform an individual locality from less to more urban. The term can describe a condition at a specific time, particularly the proportion of total population or area in urban localities or areas (cities and towns), or the rise in the proportion of people living in towns and cities. Urbanization occurs because people move from rural areas to urban areas. This usually occurs when a country is still developing. 6.7 CAUSES OF URBANISATION Various reasons have led to the growth of cities. They are as follows: 124  AECC -1/OSOU i. Industrialization: Industrialization is an important cause of urbanization. It has expanded the possibility of job. Because of better job possibilities, rural peoples are moving to towns ii. Social factors: Many social factors such as attraction of cities, better standard of living, better academic infrastructure and the need for status also induce people to move to cities. iii. Employment opportunities: Primarily people depend on agriculture for their livelihood in the rural sector. But Indian agriculture depends on monsoon, which is found to be irregular. Hence rural people migrate to cities in drought or natural disasters. iv. Modernization: Urban regions are defined by improved infrastructure, communication, and medical facilities etc. with advanced technology. People feel they can live in the cities comfortably and the before migrate to the cities. v. Rural urban transformation: It is interesting to note that not only cities are increasing in number but, also rural communities are adopting urban culture, so rural communities are no longer retaining their unique rural culture. Rural people are trying to pursue the material culture of urban people and a rural urban transformation is observed. vi. Spread of education: The literacy rate has increased among the rural people. They are showing the following advanced features- i. Change in habits of dress. ii. Modern technology adoption iii. Enlightenment of women. iv. Modern communication and transportation. E.g.: Cell phones have become common even among rural people. v. Participation in active politics. 6.8 EFFECT ON URBANISATION A number of significant changes have taken place with a high level of urbanization. The urbanization impact can be summarized as follows: Positive effect: i. Migration of rural people to urban areas. ii. Opportunities for employment in urban centers. iii. Facilities for transportation and communication. iv. Facilities of education. v. Increase in the standard of living. Urbanization can have beneficial impacts, if it happens to a desirable limit. Extensive urbanization or indiscriminate growth may have adverse effects, which may be as follows: 125  AECC -1/OSOU i. Problem of over population: Population concentration is a major problem of cities. It has resulted in accommodation problem, growth of slums etc. ii. Disintegration of Joint family: Joint family can’t be maintained in cities on account of high cost of living: People prefer to live in the nuclear type of families. iii) Cost of living: High cost of living is a major problem of cities. In metro cities like Mumbai, Bangalore etc, it is very difficult for lower income group to maintain a decent standard of living. iv) Increase in crime rates: Urban areas are known for high rate of crimes. Theft, Dacoity, Murder, Cheating, Pick pocketing, rape etc. are common in urban areas. v) Impersonal relations: Urban areas are defined by extremely secondary relationships. The concept of neighbourhood, in cities community life are almost absent. Urban life is highly monotonous. This can have a negative psychological effect on individual. People are often self- centered and have no concern for fellow human beings. vi) Problem of Pollution: Pollution is a major problems in industrialized cities. It may be caused by different industries or by excessive movement of vehicles. viii) Stress: Urban life is characterized by stress that can even strain family relationships. Women’s employment in cities is almost inevitable to meet the increasing cost of living. Changing the role of women in the family generates stress in the family that can result in divorce or strained relationship. Thus urbanization has its own merits and de-merits. Urbanization can not be prevented. But the adverse effect of urbanization can be minimized. Adverse effects There is growing competition for facilities due to the high standard of living in urban regions, which has several adverse effects:  Slums and its consequences of overcrowding.  Lack of sanitation  Poverty  Illiteracy  Unemployment  Crime is the worst impact of urbanization.  Global warming, air, pollution, water scarcity and pollution and loss of forest cover, agricultural land and wildlife depletion as a result of urban sprawl, pose severe threats to the environment. 126  AECC -1/OSOU 6.9 LET US SUM UP  The major challenge of the world today is to minimize the negative effects and build the benefits.  Infrastructure needs to be improved. Opportunities should be created within rural areas to prevent migration to cities.  Rural areas face many challenges that result from their sparse populations and the great distances that people must often travel. Among other problems, rural areas have a lack of economic opportunities in today’s information age and a general lack of various kinds of human services.  Rapid population growth and urbanization will have a dramatic effect on the increased demand for jobs, housing, energy, clean water, food, transportation infrastructure, and social services.  Urbanization is a consequence of population growth. Cities first developed in ancient times after the rise of horticultural and pastoral societies and “took off” during the Industrial Revolution as people moved to be near factories. Urbanization led to many social changes then and continues today to affect society. 6.10 MODEL QUESTIONS 1. What do you mean by the term density of population of a country? 2. What is the population of India according to the 2011 census? 3. Describe the different methods for control of population growth? 4. What is population density and describe different aspects? 5. Describe characteristic of population of India? 6. Write down the causes of urbanization? 7. Briefly describe the effects of urbanization? 127  AECC -1/OSOU 6.11 REFERENCES  Agarwala, R. 1983. “Price Distortions and Growth in Developing Countries.” World Bank Working Paper 575, Washington, DC.  Bhagat, R.B. and Mohanty, Soumaya (2009) ‘Emerging pattern of urbanization and the contribution of migration in urban growth in India’, Asian Population Studies, vol. 5, No. 1, pp. 5-20.  Deshingkar, P. and M. Sandi (2012) ‘Migration and human development in India: new challenges and opportunities’ National Workshop on Internal Migration and Human Development in India, 6–7 December 2011, Workshop Compendium, Vol. 2, Workshop Papers, UNESCO/ UNICEF, 2012  Kumar, Nandan and Bhagat, R. B. “Interaction between Migration and Development: A Study of Income and Workforce Diversification in Rural Bihar” Environment and Urbanization ASIA 8(1):120-136. 128  AECC -1/OSOU UNIT-7 CLIMATE CHANGE Structure: 7.1 Learning Objectives 7.2 Introduction 7.3 Definitions 7.4 Causes of climate changes 7.5 Effects of climate changes 7.6 Global Warming 7.7 Carbon Footprint 7.8 Environmental Protection 7.9 Let Us Sum Up 7.10 Model Questions 7.11 References 7.1 LEARNING OBJECTIVES After going through this unit you will be able to-  Define climate change  Explain natural and human-induced causes for climate change  Effects of climate change  Analyze the relationship between greenhouse gas emissions and climate change  Have an idea about global warming and its causes  A brief idea about the carbon footprint  Find out steps for environmental protection 7.2 INTRODUCTION Climate Climate refers to the long-term average weather conditions of a particular area. For example, climate of Jammu is cold and snowy in the winter, but the climate of Rajasthan is warm and humid throughout the year. A regional climate is the climate of a specific area, such as the climate of Jammu or Rajasthan. The term "global climate" refers to the climate of the whole world. When Ecologists talk about global climate change, they're referring to a consistent pattern in the climate. Other changes around the world as a result of rising global temperatures include hurricanes, melting of glaciers, and the loss of biodiversity. Because the atmosphere, water, and landmass are all linked to one another and with the climate. This means that a modification in one place can cause changes everywhere. When atmospheric 129  AECC -1/OSOU temperatures rise, for example, the oceans absorb more heat from the atmosphere and warm up. Warmer waters can lead to more powerful storms. Weather Weather refers to the state of the atmosphere at a certain location at a specific time. For example, it is windy and rainy for some day but not always. Satellites are used by weather forecasting agencies to examine the atmosphere and forecast the weather for the next several days. The Meteosat satellite transmits photographs of the Earth's atmosphere. The weather forecasters prepare the weather forecast using these photographs. At a specific location and time, the weather describes instant atmospheric conditions such as rainfall, temperature, and wind speed. It varies from day today. Climate refers to the average (or "typical") weather pattern for a certain location over several decades. Consider how weather and climate change operate on different time scales to better understand the difference. Weather is defined as the events of the environment in hours, days, and some time months; whereas the climate is defined as the environmental events during months, years, and decades; and climate change is the measurement of environmental differences during decades and centuries. Thunderstorms that last for one or two hours and tropical cyclones that last for several days are examples of weather. Climate variability is described by climate patterns like the El Nio, and Southern Oscillation, while climate change is defined by events occurring across periods, such as the average increase in temperature of the globe or global warming. 7.3 DEFINITION Climate change: “Any change in climate over time, whether due to natural variability or as a result of human activity” (IPCC, 2001a).The United Nations Framework Convention on Climate Change (UNFCC) in Article 1defined it as: “climate change refers to a change in climate which is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural climate variability observed over a comparable period” (IPCC, 2001a). Climate variability: Climate variability is defined by scientists as the way the climate changes, over time, not just from day to day like the weather. Some summers are significantly cooler than others. Some years have more precipitation than others. Even though people are highly sensitive. It is not as evident as weather variability in terms of climatic variability. Since it occurs throughout seasons and years. Yearly deviation of environmental parameters such as temperature, wind speed, rain fal, etc., from a long-term average climatic variability. 130  AECC -1/OSOU Fig. Various climatic variations as a result of environmental events Source:https://www.google.com/search?q=global+wind+circulation+diagram&rlz=1C1CHBF_enIN968IN968&source =lnms&tbm=isch&sa=X&ved=2ahUKEwjunMXZ- pz4AhXH8DgGHXrzCx8Q_AUoAXoECAEQAw&biw=1600&bih=781&dpr=1#imgrc=P68L2uUqqKR4-M 7.4 CAUSES OF CLIMATE CHANGE Environmental disturbances which are either natural or man-made are the main cause of climate change. Natural processes like volcanic eruptions, ocean currents, Solar movements, El Ninos and La Ninas are the causes of climate change. On the other hand, Greenhouse gas emissions, deforestation, forest fire, coal mining, fossil fuel burning, industrialization, and agriculture are the man made causes of climate change. Fig. The earth surface due to climate change Source:https://www.google.com/search?q=CLIMATE+CHANGE+ON+EARTH+SURFACE&rlz=1C1CHBF_enIN96 8IN968&source=lnms&tbm=isch&sa=X&ved=2ahUKEwjGuLX_- pz4AhXTjgGHWaQAFoQ_AUoAXoECAIQAw&biw=1600&bih=781&dpr=1#imgrc=mL6sevU5r6BvXM Human activities, particularly fossil fuel combustion, increasing greenhouse gases (GHGs), resulted an extraordinary variation in the climate during the last 100 years. The 131  AECC -1/OSOU infrared energy emitted from the earth's surface is captured by these gases, warming the globe. Since the early twentieth century, gglobal lobal average surface temperature increased by about 0.7°C (1.4°F). The climate of the Earth is a complicated system that is continuously changing, but it is currently warmer than it has been in early years. The increasing atmospheric carbon dioxide (CO2) level is creating havoc on plant and animal life as well as environmental systems. And, if CO2 levels continue to climb at their current rates, the world will become far hotter than it is now, maybe hot enough to melt much of the Earth's current ice cover.The repeatedly throughout The temperature of the Earth has changed repeatedly geological time. The earth has gone through repeated cycles of glacial (cold) and interglacial (warm) periods lasting around 80,000 years on average. These were most likely caused by the Milankovich ovich Cycles, which govern the seasonal timing and intensity of solar radiation entering the atmosphere and are governed by regular variations in Earth's orbit and spin. The number of greenhouse gases (primarily carbon dioxide, methane, and water vapor) in the atmosphere, the extent of sea and land-based based ice across the northern hemisphere, and alterations in wind and ocean current patterns are all possible contributors to the onset and termination of ice ages. Earth's climate has changed between periods of relative warmth and relative cold for much of its 4.5 billion billion-year history, each lasting tens to hundreds of millions of years. The polar parts of the earth were fully ice-free free during the warmest periods. Earth has also gone through multiple ice ages, which h lasted millions of years and saw sea ice advance and retreat many times throughout the world. During the coldest parts of the year, snow blanketed the entire globe. Scientists have gone back in time to identify a time when atmospheric GHG concentrations were as high as they are expected to be in the next decades, if current emission trends continue. They, CO2 levels were higher than 500 parts per million during the Eocene epoch, which lasted from 55 million to 38 million years ago. Source:https://www.google.com/search?q=PAST+500+MILLION+YEARS+OF+CLIMATE+CHANGE&tbm=isch&v https://www.google.com/search?q=PAST+500+MILLION+YEARS+OF+CLIMATE+CHANGE&tbm=isch&v ed=2ahUKEwj7m8qA5z4AhWe0HMBHUCCAjIQ2 ed=2ahUKEwj7m8qA5z4AhWe0HMBHUCCAjIQ2- cCegQIABAA&oq=PAST+500+MILL cCegQIABAA&oq=PAST+500+MILLION+YEARS+OF+CLIMATE+CHANGE&gslcp=CgNpbWcQAzoECAAQQz ION+YEARS+OF+CLIMATE+CHANGE&gslcp=CgNpbWcQAzoECAAQQz oLCAAQgAQQsQMQgwE6CAgAEIAEELEDOgoIABCxAxCDARBDOgcIABCxAxBDOgUIABCABDoGCAAQH hAFOgYIABAeEAg6BAgAEBhQ6QdYmYQBYIeHAWgAcAB4A4AB2gGIAd1AkgEGMC42Ny4ymAEAoAEBqg ELZ3dzLX 132