Population Growth and Regulation

Population Dynamics – Population Growth and Regulation

Introduction

Population dynamics  

Population dynamics is the study of how and why populations change in size and structure over time. Rates of reproduction, mortality, and migration are all important elements in population dynamics. The term population dynamics refers to how a species’ populations vary over time. 

What is meant by population growth? 

Population growth is the change in a population through time, and it may be measured as the change in the number of individuals of any species in a population per unit time. Between 1800 and 2011, the global population increased from one billion to seven billion. According to estimations, 135 million people were born in 2011, and 57 million died, resulting in a 78 million rise in population. 

Principle of population growth 

The Malthusian theory of population growth is a theory proposed by Thomas Robert Malthus in which population growth is stated to rise exponentially. Malthus investigated the link between population increase and resources in An Essay on the Principle of Population. As a result of this, he established the Malthusian hypothesis of population growth, in which he argued that population growth happens exponentially and grows in proportion to the birth rate. 

According to Malthus, there are two sorts of ‘checks’ that may be used to restrict the pace of population expansion.  

1. Preventive checks are steps that people can take voluntarily to avoid contributing to the population. 

2. Positive population growth restraints include factors like sickness, wars, starvation, and poor living and working conditions. 

The population is inevitably constrained by means of sustenance. Unless there are some very strong and visible checks, the population will necessarily grow when means of sustenance increase. These restraints, as well as the checks that repress the population’s greater might and maintain its consequences at a level with the means of sustenance, are all resolvable into moral restraint, vice, and suffering.   

Population growth curve 

A population growth curve is anything that depicts the pattern of population increase over time; in other words, a growth curve is an empirical model of the development of a quantity through time. 

In biology, growth curves are commonly used to calculate values like population size or biomass, individual body height or biomass. Values for the measured attribute can be plotted as a function of time on a graph. In principle, any creature might take over the world just by reproducing.  

Types of the population growth curve 

Depending on the environmental conditions, two types of population growth patterns may occur: 

1. In an ideal, limitless environment, an exponential growth pattern (J curve) arises. 

2. When environmental forces slow the rate of growth, a logistic growth pattern (S curve) develops.  

Exponential growth curve 

In an ideal environment with infinite resources, exponential population increase will occur. Population growth will be modest at first due to a scarcity of reproducing people who may be geographically distributed. 

As the population grows, so does the rate of growth, culminating in an exponential (J-shaped) curve. Exponential growth can be observed in relatively small populations or in freshly colonized areas by a species.  

Logistic growth curve 

When population numbers begin to approach a finite carrying capacity, logistic population growth will occur. Environmental resistance develops as a population approaches its carrying limit, decreasing the rate of expansion. This produces a sigmoidal (S-shaped) growth curve that reaches a plateau at carrying capacity. Any steady population occupying a fixed geographic location will ultimately experience logistical expansion.  

Population regulation 

Population regulation refers to biological mechanisms that counteract disruptive occurrences (for example, weather events, changing environmental circumstances, disease outbreaks, and so on). The variables that regulate population increase are classified into two categories: density-dependent and density-independent.  

Density-dependent: 

• Disease, competition, and predation are all density-dependent issues. Population size can have a positive or negative connection with density-dependent characteristics.  
• These limiting constraints rise with population size and limit growth as population size grows in a positive relationship. 
•  With a negative connection, population growth is constrained at low densities and becomes less constrained as densities increase. 
• Population mortality and migration may also be affected by density-dependent variables.  

Density-independent: 

• Density-independent factors are those that influence per capita growth rate regardless of population density. 
• Environmental stresses and natural disasters, for example, are unaffected by population density changes. While density-dependent variables are frequently biotic, density-independent factors are frequently abiotic. 
• Food or nutrient scarcity, pollution in the environment, and climatic extremes, including seasonal cycles such as monsoons, are examples of density-independent causes.