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A population is defined as a distinct group of people, whether it is a country or a collection of people who share common characteristics and attributes.
By research we discovered that some organisms are able to respond physiologically, while others respond by the behavioural changes (like by migrating temporarily to less stressful places). Adaptation can be explained as any characteristic of an organism (morphological, physiological, or behavioural) that allows it to survive and reproduce in its environment. Many adaptations are genetically predefined and have evolved over a lengthy evolutionary time. So, we can also define population as the number of people residing in a particular area like a city or town, a region, any country , continent or the whole world in a particular time or time interval.
Population Attributes
- Population Size or Density
It is the number of individuals of a particular species living per unit defined area or volume.
- Birth Rate (Natality)
It is the rate of production of new individuals in a particular population per unit of Population per unit time. For e.g- If in a small pond , there were 30 flowering plants last year and through reproduction, 10 new plants are added, taking the current population to 40. Then, birth rate = 10/30 = 0.33 offspring per flowering plant per year.
- Death Rate (Mortality)
It is the net rate of loss of individuals from a defined population per unit time due to the harsh and unfavourable environmental changes, death , competition or may be predation etc. For e.g – If individuals in a laboratory population of 30 , 3 mosquitos die during a definite time interval. Then, the death rate = 3/30 = 0.1 individuals per mosquito per week.
- Sex Ratio
The sex ratio is the ratio of males to females in a defined population. The ratio tends to be 1:1 in most the sexually reproducing species which can be explained by Fisher’s principle
- Age Pyramid
A population pyramid or “age-sex pyramid” is a way of diagrammatically representing the distributions of a particular population by their age groups and sex; It takes the shape of a pyramid when the population is growing. The pyramid can be used to visualise the age of a particular population. Age and sex are two central features of a population. Populations are not homogeneous units. Population differ by age, sex, race/ethnicity, marriage status, and other many characteristics. Accordingly, the study of population composition receives considerable attention in demography
Population Growth
Population growth of a population depends on food availability, predation and weather
- Natality
Natality or more commonly birth.
It is commonly represented as the Birth Rate. It is the ratio of the number of births in a population to the total strength/Size of the population.
- Mortality
Mortality or more commonly death.
It’s commonly represented by the death rate. It is the ratio of the number of deaths in a population to the total strength/size of the Population.
- Immigration
Immigration is defined as the movement of people or persons from a place to a country or place in which they are not citizens, for permanently settling in that place and becoming a citizen.
- Emigration
In-migration and out-migration do not necessarily alter the age distribution of a population. If migration rates did not vary by age, and if migrants experienced the same fertility and mortality levels as the population of interest, then migration would affect the size of the population but not the age composition. However, migration rates almost always do vary with age. Out-migration from an area is predictably higher for young people than for older people.
Growth Models
- Exponential Growth
- Logistic Growth
Population Interactions
A population is defined as a group of individuals of the same species. The interrelationship between the individuals in an ecosystem is termed population interaction. The organisms in an interaction are most likely to be influenced by each other either positively, negatively or neutral.
- Predation
Predation is an ecological process in which an animal kills and eats another animal. The animal which kills is called a predator and the animal which is being killed is called prey.
- Competition
Competition is the interaction of organisms or species that require a resource that is in short supply. Because the presence of one of the species always affects the number of resources accessible to the other, competition reduces both organisms’ fitness.
- Parasitism
Parasitism is a type of symbiosis in which one creature (the parasite) benefits at the expense of another organism (the host), usually of a different species; the relationship can also result in the host’s damage.
- Commensalism
Commensalism is defined as the connection between two species/individuals in which one organism gains food/ benefits from the other organism without harming or without benefiting the latter organism..
Ecological Adaptations
An ecological adaptation is defined as any physiological, behavioural, or morphological feature of an organism that allows the organism to survive and reproduce in its natural habitat or environment.
Plants possess unique characteristics that enable them to increase their tolerance limits to –
- Light schedules
- Unfavourable weather
- Excessive heat
- Saturated water condition
- Environments that are saline
Plants are classified as Sciophytes (shade-loving plants) or Heliophytes (light-loving plants) based on light intensity (Adapted to high intensity of light).
Plants are divided into Five Groups based on their Habitats
Hydrophytes- grow in aquatic environments
Mesophytes- grow in a moderate humid and temperature environment
Epiphytes- grow on other plants
Halophytes- grow in saline environments
Xerophytes- grow in dry or xeric environments
Conclusion
A population has many characteristics like Population attributes, Population Growth, Interactions etc. Populations are living things. Populations are made up of all of the species that live in a given area, and they fluctuate due to a variety of variables, including seasonal and yearly changes in the climate, natural disasters such as fires in forest and volcanoes , and competition of resources between and within the species. Demography is a statistical study of population dynamics that employs a set of mathematical methods to analyse how people react to changes in their surroundings. Rather of being a physical form or a part of the organism, adaptation is essentially a process. An internal parasite (such as a liver fluke) can demonstrate the difference: despite having a fairly simple biological structure, the parasite is highly adapted to its specialised environment.
