Organisms and Population Attributes


The sustainability of the species and population rest on the interdependency and the nature of the interaction between the organisms living in a habitat. As a thumb rule, there must be logical balance between the numebr of prey and predators in a given ecosystem as this can bring balance in the ecosystem. The statistical analysis, reporting and distribution of facts about population are called the population attributes or demographics. A population is open to different  external influences that result in the disese or death . To understand this we need to learn the basic formulae used to explain the population.



Species  and population

A population is a more comprehensive term defined as the collection of many species live in a well-defined geographical area". Different organisms share, compete, and interbreed with each other proves the fact that they all rely on common factors such as food, air, and water.  Species make up the group of organisms that shares similar characteristic features and are able to interbreed within the same species. For example, all human beings. 


Attributes of population

Population attributes may be represented by descriptive, numerical or graphical methods with the use of charts, tables, pictures and some mathematical devices. Most of the population attributes are calculated by using rates, ratios and percentages. The value of a particular phenomenon such as death rate or birth rate by comparing the standardized numbers for every 100 or 1000 population of a given geographic province. For example, if we want to calculate the death rate due to malaria, we do it by taking into the consideration deaths of malarial patitients in every 1000 population within the given circumference( say 10 kilometres) .  Some of the population attributes and their formulae are explained.


Size of Population

It is the number of living individuals of a given species per unit area. In other words, it is the mathematical expression of the number of human beings/tigers/lions etc. living in per square kilometres/square mile/10 kilometres and so on. It is represented as;



Birth rate

It is the total number of live births in a given year against the total population of that area X 1000. So, the birth rate is expressed as,




Sex ratio or gender ratio

It is the ratio between the male and female population of a species. For example, if we take human subjects, the gender ratio  is calculated as the total number of girls for every 1000 boys in a given geographic area or vice-versa.  Assume that there are 1000 boys and 800 girls within a square kilometre; then the gender ration is 8:10. It can be represented by a pi-diagram or bar chart as shown below.





Age pyramid

It is the graphical representation of the distribution of different age groups in a specified locality at a given point of time. In general, human age groups can be categorized as  0-20 years, 21-40 years, 41-60 years, 61-80 years, above 80 years etc. If the age distribution (% of individuals of a particular age or age group) is plotted against the total population, the resulting structure is called the age pyramid. Age pyramid is characterized by, expanding, stable and declining traits as shown below. Expanding age pyramids depict populations that have a larger percentage of people in younger age groups. Populations in this category usually have high fertility rates but lower life expectancies. Declining age pyramids, on the other hand, depict populations where there is limited young generation. The stable population is of middle age population with lesser chances of death and disease.






Population Distribution

It is a variant of the population density which mainly concentrates on the population thickness and  pattern in a given area, for example, 20 insects can spread equally, or in groups/clumps. The population distribution can be clumped, random or uniform. The distribution pattern may reflect on various characteristics of the species and how favourable is the environment for a given pattern of distribution. The simple illustration below depicts the visuals of different types of population distribution.








  1. What are attributes? Mention the few population attributes.

  2. Brief the process of population distribution

  3. What are mortality and morbidity indicators in  a population?

  4. How do we calculate the size of a population?

  5. Explain the dynamics of age pyramids.





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