Biological theories of population

In this slide discussed about the biological theories of the population by different famous biologist.

1. PRESENTATION ON- BIOLOGICAL THEORIES ON POPULATION SUBMITTED TO :- DR. A.K. BHARTIYA (ASSOCIATE PROF. DSW) SUBMITTED BY :- AVANISH KUMAR MSW 2 nd SEM.(REGULAR) DEPARTMENT OF SOCIAL WORK UNIVERSITY OF LUCKNOW

2. CONTENTS TABLE Sr. No. Contents 1. Introduction 2. Sadler’s Density Theory 3. Thomas Doubleday’s Diet Theory 4. Pearl and Reed’s Logistic Curve Theory 5. Ginni’s Circular Theory 6. Herbert Spencer’s Theory 7. Castro’s Protein Consumption Theory 8. Conclusion

3. INTRODUCTION Biological theories mainly based on biological aspects. Biological theories mainly concerned with human fecundity. Many of the social scientist proposed the different biological theories. Some important biological theories are as follows:- {1} Density Theory {2} Diet Theory {3} Logistic Curve Theory {4} Circular Theory {5} Spencer’s Theory {6} Protein Consumption Theory The biological theorists believed in existence of metaphysical will of nature to perpetuate the species.

4. Fecundity Density X Y P P’ A B C F1 F2 F3 O D1 D2 D3 Michael Thomas Sadler’s Theory / The Density Principle 1780-1835 Work entitled as ‘ The Law of Population ’ in 1830 Define inverse relationship b/w The Density of Population and The Fecundity According to Sadler, such increase of population and food supply in mathematical terms just cannot happen, because when population increases density too will increase. He believed that population adjusts itself with the times. People will be able to produce food according to their needs and the food supply and population will get adjusted to each other.

5. It measures only in a given situation with the absence of the technology Population controlled with Happiness and Pleasure Criticism of Sadler’s Theory Sadler failed to distinguish between fecundity and fertility Moreover, in many countries of the world where the density is high, the fertility rate is also high. Even in India, in some states like Delhi Sadler’s view that with industrialization the population decreases has not been proved true. In a country like India, industrialisation has not led to the decline in the growth of population.

6. Y X F1 F2 F3 Fecundity Food Supply S1 S2 S3 P P’ Stage-ii Stage-iii Stage- i THOMAS DOUBLEDAY’S DIET THEORY Thomas Doubleday propounded the ‘ true law of population ’ He stated the inverse relationship between food supply and fecundity Doubleday mentions three stages of food supply, i.e., ( i ) Stage-I : The Plethoric state having good food supply where the fecundity is low, (ii) Stage-II : The Deplethoric state in which due to food shortage we find diminution of proper nourishment where the fecundity is high (iii) Stage-III : When resources and fecundity both are eqal . O

7. d Y X Q4 Q3 Q2 Q1 Q P P1 P2 P3 size Time PEARL AND REED’S LOGISTIC THEORY Theory titled in his book ‘ The Biology of Population Growth ’ This theory is also known as the ‘S’ shape theory This theory is based on three assumptions: ( i ) In the given time, measure the curve. (ii) The number of population is maximum . (iii) The environment and population are constant. According to the graph 4 stages are shorted out ( i ) Rapid Growth: (Q-Q1) (ii) Stable Condition: (Q1-Q2) (iii) Decreasing Stage: (Q2-Q3) (iv) Low Decreasing Stage: (Q3-Q4) O

8. Y X A B C O G3 G2 G1 S1 S2 S3 P P’ F/PG SD/ND GINNI’S CIRCULAR THEORY Ginni define the inverse relationship between the population growth and social development and national development This theory stated that Population growth impacts upon the social and national development Ginni was of the opinion that only biological factors are responsible for the increase in population and therefore his theory of population can be characterised as a ‘ natural law theory ’ Ginni was of the opinion that due to high fecundity population increases and consequently social and economic problems become complex

9. Circular Theory has four population growth stages: ( i ) Rapid Growth Stage (ii) Slow Growth Stage (iii) Maturity Stage (iv) Decreasing Stage Ginni believed that the population growth is similar to the cyclical growth of an individual. In the first stage, the growth of population is very rapid while in the second stage, the growth is comparatively slow. In the third stage which is known as senescence, population decreases and there is deterioration in the quality of civilization Maturity Stable Increasing Slow Growth

10. Y X A B C O G3 G2 G1 S1 S2 S3 P P’ Genesis Individualization HERBERT SPENCER’S THEORY He stated that the population growth is determined by ‘ natural law ’. This theory is based upon the individualization and genesis He propounded the inverse relationship between the individualization and genesis Spencer shorted out three stages: ( i ) Rich- Where individualization is Increased and genesis is low i.e The developed condition (ii) Poor- Where individualization is low and genesis is high i.e Underdeveloped condition (iii) Medium- Where individualization And genesis both are equal i.e Developing condition

11. CASTRO’S PROTIEN CONSUMPTION THEORY He define his theory in his book ‘ Geography of Hunger ’ in 1952 He define the inverse relationship between the protein consumption and the fecundity According to Castro, deficiency of protein make undernourished people more fertile than those who are well nourished He conducted his experiment upon the rat and hen. He categorize the rats in three groups and provide the protein content in different ratio and shown the result : Rats’ group Protein consumption % Reproduction capacity (Births) Group 1 10% 23.3 Group 2 18% 17.4 Group 3 22% 13.8

12. CONCLUSION The Biological theories are mainly based on the Biological aspects that are responsible for population growth. These theories are mainly concerned with human fecundity. The biological theorists believed in existence of metaphysical will of nature to perpetuate the species. THANK YOU !