Effects of Rapid Population Growth Essay Example. Another cause of population growth is older populations living longer while birth rates do not decline. Many nations are experiencing rapid population growth of that sort in numbers that haven’t existed in the past. Any combination or single factor can cause the population number to increase Population Growth: Essay on Population Growth! From sociological point of view – population simply means number of people, living at a particular area (country/region) at a particular time. The current human population growth is something unprecedented in the history of the world. If we look back to the history of human population growth While between and the percentage of increase was , between and it was The addition of 16 crore people in the decade means an addition of little less than 2 crore persons every year, or about 17 lakh persons every month, or about 74 thousand persons every day, or about 52 persons every minute
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edu no longer supports Internet Explorer. To browse Academia. edu and the wider internet faster and more securely, please take a few seconds to upgrade your browser. Log in with Facebook Log in with Google. Remember me on this computer. Enter the email address you signed up with and we'll email increase in population essay a reset link. Need an account? Click here to sign up. Download Free PDF. Population growth and structure in a variable environment Oecologia, Uno Wennergren. Jan Landin. Download Download PDF Full PDF Package Download Full PDF Package This Paper. A short summary of this paper. Download Download PDF. Download Full PDF Package. Translate PDF. Oecologia Oecologia 9 Springer-Verlag Population growth and structure in a variable environment I.
When a population experiences temporal on the conditions it experiences during its lifetime. For changes in the vital rates due to environmental or biotic poikilothermic organisms, the temperature regime is variation, change is not only increase in population essay in the rate of crucial. It is evident that changes in the vital and develop- population growth but also in the structure of the popula- mental rates caused by environmental variation will result tion. In this study we present a method for transforming in more or less pronounced variation of population observed patterns notably how vital rates change with growth rates. temperature into functions that can be used in population External factors, such as temperature or competition, growth models and analysis of population structure.
The acting on the conditions for fecundity, survival and method is exemplified by applying it to cohort studies in growth may cause a change in the instantaneous mean different constant temperatures of four species of aphids, population growth rate. We conditions for summation of individual vital rates. If there use piece-wise linear functions to transform the vital rates is no change in vital increase in population essay over a long period, the distribu- of the cohort studies. The lifespans are divided into tion will stabilize and the intrinsic rate of increase may be phases, each phase having linear rates.
A projection used as the mean growth rate. So, the two different kind of matrix is formulated, increase in population essay, where the elements are temperature causes mentioned above are both driven by the variation dependent fecundities, survivorships and developmental in conditions for fecundity, survival and growth. We will rates. The major result is, contrary to what theory predicts discuss changes in the vital rates and their direct effect on as reasonable Caswellthat population structure of mean population growth assuming stable stage distribu- these aphid species will become almost fixed although the tion, i. the intrinsic rate of increase, and thereafter the temperature varies. This result is consistent with findings problems associated with variable stage distribution.
For of earlier field studies Wiktelius A fixed population fast growing species, like aphids, increase in population essay, one can expect conver- structure implies that it increase in population essay possible to calculate the popula- gence of the distribution to take between a few days and tion growth rate on the basis of intrinsic rates increase in population essay increase. a few weeks depending on the temperature and the initial By simulating different temperature regimes we also show stage distribution within the population. When calculat- that initial oscillations in the population structure dam- ing this convergence, one usually has to assume constant pen out after a few days, increase in population essay. After initial oscillations, calcu- temperature, or even constant environment.
But this, of lations of population growth using intrinsic rates of course, is not what we expect to find in nature, increase in population essay. When increase are consistent with calculations made by a matrix a large within-day temperature variation is common, we model. can expect that no stable stage distribution will be achieved, or as Caswell puts it, "Convergence ofn t Key words: Demography - Population growth - Temper- to a fixed, stable stage distribution is too much to expect ature - Stage distribution - Aphids when the environment varies", [n t is here defined as the stage distribution at time t].
To avoid confusion we will henceforth denote stage distribution as stage or popula- tion structure. The ability of an individual member of a population to A new theory for predicting population growth when survive and reproduce depends on its physiological state, increase in population essay. variation in vital rates is frequent and large enough to The state which an organism can actually achieve depends produce a variable stage structure has been put forth by Cohen, Yuljapurkar and OrzackTuljapurkarand Kim and Sykes ; for Correspondence to: U. Wennergren review see Tuljapurkar This weak ergodicity implies that the addition, calculate the population growth rate on the population "forgets" its past, and that it is therefore pos- basis of intrinsic rates of increase.
To be more precise; sible to discuss the behaviour of population growth in what kind of probability distribution of aphid population general terms. Note that the population growth and struc- structures can we expect when the temperature varies? ture may still vary with time, though independently of the A large variance in population structure, especially in the initial structure. The theory also includes stochastic envi- fertile stages, indicates major impacts on population ronments. If the stochasticity of the environmental states growth. To examine this we will use some theory and eventually converges to a stationary distribution of differ- mathematics and we will also simulate population growth ent environmental states, increase in population essay, then the strong stochastic to explore the structural variation.
ergodicity implies that there will be a fixed stationary distri- Many studies of population dynamics in a variable bution of structures to which all initial populations will environment have been concerned with the development converge. The population structure need not converge to of elaborate population growth models based on systems a fixed stationary distribution of structures if the probabil- of discrete or delay differential equations Groenendael ity distribution of environmental states changes through et al. Anyhow the weak stochastic ergodicity implies that how the effect of environmental variation should be evalu- any two initial populations will converge to the same ated both analytically and numerically Tuljapurkar time-variant probability distribution of structures.
The a, b; Orzack and Tuljapurkar In this study, we magnitude of the fluctuations in mean population growth will transform observed patterns, notably how vital rates rate and population structure will depend on the response change with temperature, into functions that can be used to the environmental variation. In this paper we will show in these population growth models and analysis. In this that the response can primarily be studied as the variation way we will be able to predict population growth more in the stable stage structure at different constant condi- accurately using experimental data as raw material. Note that while it is not a logical imperative, it is The model is exemplified by applying it to experimental most likely that a large variation in the intrinsic rate of data describing the vital rates of four dissimilar species of increase is followed by a large variation in the stage aphids, Lipaphis erysimi K.
Some earlier field studies indicated the converse, Wlk. that although population growth may vary with tem- perature, it will be possible to calculate population growth Model and methods using intrinsic rates of increase Wiktelius contradic- ting Caswell The aim of our work is to demonstrate Demographic data from four aphid species are used to demonstrate how different temperature regimes may affect the popula- the formulation and application of our model. All four species are 15 ~ O. For notations of the different linear parts and functions, i.
phases, see the text. The data on Lipaphis erysimi K. are pre- squares, increase in population essay, the best fitting increase in population essay to the survivorship and fecundity of sented in Landin and Wennergren The data for the three the four aphid species at 5, 10, 15, 20, 25 and 30 ~ C. This curve fitting other species, Metopolophium dirhodum Wlk. Lipaphis piece in Fig. was chosen for the principal interpretation, since its data nodes. In the next step, a set of functions polynomials of, as set has a more comprehensive measurement of vital rates days vs. a maximum, second degreeF~ Twas fitted to demonstrate how weekscompared to the other three species. The applications using nodes in the piecewise linear functions, for example, age when first the three other species are mainly to emphasize the generality of the giving birthchanged with temperature Fig.
This set of functions findings. The model is based on data on the vital rates, i. fecundity will then describe how fecundity and survivorship change with both and survivorship, increase in population essay, for some of the environments that the population chronological age and temperature Fig. from these functions will experience. Such data may originate from cohort studies in it is, for every temperature, possible to derive all the linear equations constant temperatures. The idea is to transform these data in such that make up the piecewise linear functions described in Fig. The a way that most will be intact when inserted into a model for 20~ data for the mustard aphid were not included in the calcu- population growth.
We will first present how we calculate popula- lations of the various F~ T due to experimental problems which tion growth and at the end of this section and in the Appendix we made these values unreliable; see Landin increase in population essay Wennergren As will use some mathematics to explore possible behaviour of the for the three other species, the experimental data presented in Dean population structure. To improve increase in population essay fitting of the linear piecewise functions to organism. It is therefore necessary to define some kind of develop- Dean's experiments, we decided to lock the node of the age when mental scale for the life history of an organism. This scale should, to first giving birth since these values are presented in a separate table some extent, identify specific stages that characterize change in the in Dean's article.
So in this case the curve-fitting program will only vital rates. The rate at which organisms pass through the stages is move around the other nodes to minimize the sum of squares. Note denoted developmental rate. Note that these stages need not differ that the surfaces in Fig, increase in population essay. Rather, they are defined by change in fecundity functions as in Fig. These surfaces do not make it possible to relate and survivorship. This kind of formalism is essential since a basic the vital rates at different temperatures to each other because of problem is the infinite number of possible environments. Temper- inconsistent age scale. For example, at age 10 days at 25~ the ature is a continuous variable and poikilothermic organisms mustard aphid has been fecund for 5 days while the same species at respond to temperature in a nonlinear and complex manner, increase in population essay.
Thus 15~ has 5 more days to go in the prereproductive phase. Therefore it is impossible to experimentally investigate every conceivable we have to define some kind of increase in population essay age and developmental temperature regime or even every constant temperature. Our rate.
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Essay on Increasing Population! ADVERTISEMENTS: The total number of people inhabiting this planet as of July has been estimated to be billion by the United Nations, with billion (or % living in economically more developed countries of Europe, North America, Oceania, former Soviet Union and Japan, and the remaining billion (or %) living in Estimated Reading Time: 5 mins Rapid growth in population has become a global issue and Pakistan is not an exception in this blogger.com the time of its being Pakistan got some uncalled gifts such as illiteracy, unemployment, corruption, lawlessness and the over population added to the blogger.com the time of partition, Pakistan had a population of 33 million. Today, our country has crossed the number of 1. Describe the world’s population growth up until now and the predicted growth towards The Global human population increases growth amounts to around 75 million annually, or % per year. The global population has grown from 1 billion in to 7 billion in
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