A population is the net number of individuals of a particular species that is, adults of both the sexes, juveniles, larvae, eggs, in a habitat at a specific time. As species don't exist individually in their natural habitat, the word which readily comes to mind when population is described is density. Population density, thus, signifies to the number of individuals of a species per unit area of the habitat. It might be per square meter or per square kilometer. Natural population modifies in size and there are various factors which are as well responsible for such changes.
The Population of species in natural habitats develops or increases, though, this rise is not indefinite as populations are kept in check by some ecological factors. If a species is introduced into a new habitat where food is plentiful and other factor influencing growth and reproduction are favorable, then the s-shaped sigmoid growth curve is the characteristic growth pattern noticed.
The sigmoid pattern of growth is characteristic of populations where food is plentiful and factors which influence reproduction and growth are not restrictive.
Overcrowding and Overpopulation:
Overcrowding at times termed to as overpopulation is if a population in a given habitat rises further than the carrying the capacity of that habitat. That is, the resources of the habitat are not adequate to support all the individuals in that habitat. The given factors lead to overpopulation.
a) Natality: The birth of young will naturally raise the population of a specific species.
b) Immigration: Signifies to the movement of individuals from other regions into a habitat.
c) High survival rate is the other factor which leads to overpopulation. Survival rate is direct function of the parental care. Species such as mice, rabbits, dogs and humans defend their young and are thus capable to survive to the reproductive age and can reproduce before they pass away. This will naturally lead to rise in the size of the population. Where life anticipation is high and pre-sexual maturity age is low, populations will naturally rise.
Effects of Overcrowding:
Overcrowding or overpopulation leads to the following:
a) Food shortage and scarcity of other resources that is, space, light, nutrient and so on.
b) Occurrence of diseases.
c) Predation and parasites.
d) Struggle for space, shelter, food, mates and so on.
e) Toxic wastes are possible to build-up in such a habitat.
In order to evade overcrowding and its resulting effects, living organisms make use of the given methods:
a) Plants utilize the methods of dispersal that make sure that seeds are dispersed far and broad. Agents of dispersal like animals, water and wind make sure this. As well plants employ explosive procedures of dispersal.
b) Seasonal variations in availability of food influence the carrying capacity of habitats. For example, in the savanna, food is plentiful all through the rainy season however scarce all through the dry season. To avoid overcrowding throughout the dry season, most of the animals emigrate out and return when the rains begin.
Food shortages or scarcities mainly caused by two factors, these are diseases and draught. Food shortages lead to a reduction in population size. Decrease in the population mainly caused by:
Food scarcity will naturally lead to the competition for the restricted food amongst organism. This competition becomes more extreme if it is between individuals or species which encompass similar ecological niche. Such who are better adapted will survive whereas those than can't adapt or less adapted will pass away.
Scarcity of food will force individuals to move out of the habitat in search for food. Note that the individuals only emigrate when possibilities of survival are extremely threatened in the present habitat and enhanced in the new habitat.
Mortality signifies to death of individuals in a specific time. Food scarcity will lead to death generally especially in the vulnerable age groups that is, the young and the old.
4) Reproductive Rate:
If food is in short supply, the rate of reproduction is decreased. Birds will tend to place fewer eggs and mammals will give fewer births. Scarcity of food as well consists of a direct effect on the sexual maturity. Longer period of time is needed to rise in size or grow and accomplish sexual or reproductive maturity.
Populations in the natural habitats exhibit exponential growth. The restrictive factors in the atmosphere cause the population to become stable. These limiting factors are termed as environmental resistance. Though, human populations have been found to take exemption to this as humans have controlled ecological factors. This have facilitated them raise their average life span. This is accomplished by lowering mortality via enhanced food consumption, medicare, better shelter and sanitation; as well they have enhanced agricultural productivity. These have led to an incessant growth in the human population.
Human Population Control:
The factors which control human populations are as:
a) Diseases or outbreak of disease.
d) Natural disasters example: earthquakes, flood, fires, typhoons and so on.
Though, as a civilized nation, such factors are undesirable as means of population control. The acceptable alternatives are, thus, birth control techniques.
Birth control is used via several means. These comprise:
a) Contraceptives: Women take contraceptive pills on a regular basis. It might be taken once daily for three weeks of each and every month. A break is required all through the menstrual period. Such pills prevent ovulation. Side effects are general. There are different kinds of contraceptives; one is counsel to see a medical doctor prior to using any contraceptive.
b) Withdrawal process: The penis is withdrawn just prior to ejaculation of the sperms. The draw back or demerits is that failure rate is high.
c) Rhythm process: This process targets the discharge of the female egg and intercourse is suspended or ignored at such period. The problem is that ovulation period modifies.
d) Spermicides: Such are tablets or creams for foams which kill the sperm as they are ejaculated into the vagina. The spermicide is applied to the vagina prior to sexual contact.
e) Use of condoms or barriers that are worn above the penis. This prevents the sperms from entering the vagina.
f) Intra-uterine device: A device or tool put in into the woman's womb and prevents the implantation of the fertilized egg in the uterus.
g) Abstinence: This comprises self control; individual don't contribute in the sexual activity.
Relationship among Availability of Food and Human Population
Adequate food leads to a healthy population. This consists of a direct bearing on the society as healthy people work harder than unhealthful people. Less death would as well take place. Inadequate food signifies the population is weak and unhealthy and fall victim to infectious diseases. Such a population can't be productive. Standard of living is highly decreased or poor and education is adversely influenced.
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