POPULATION AND POPULATION GROWTH MODEL

A.    Definition Population

Population is a group of individuals together and occupy species in a habitat that is small enough to allow interbreding among all members of the group. Some populations do not experience interbreding yet self-pollinating (self polination) or reproduce sexually. The total area occupied by allowing the potential for gene shuffling through self-pollination or neighbor.

Determination or classification of species in the population can be done in two ways: In taxonomy, the species is determined based on both the evolution of family relationships, as well as the history of his ancestors. Based on the role or function, namely the determination of species based on shared its role in the environment based on its unique and distinct nature of each individual, the population has characteristics are as follows:

1.      Density

Density is a measure of population size in units space or volume, which is generally described by the size of the fish mince individual or population biomass per unit of space or volume.

2.      The Birth Rate

Birthrate is the reproduction of new individuals in the population through birth, germination / cleavage.

3.      The Death Rate (Mortality)

Mortality is the number of individuals in the population die during a specific time period.

4.      Genetic

5.      Age Structure

Population properties that are important affect both the birthrate and mortality. Motalitas usually differ according to age and ability to multiply very dry limited to a particular age group.

6.      Biotic potential

Biotic potential is the potential of the total population in an area / ecosystem is influenced by life, encompassing all living things on earth, both plants and animals.

7.      Growth Form

Spreading/ displacement of population is the movement of individuals or tools of reproduction into or out of a population or population areas, also influence the shape and density of population growth is concerned together with birthrate and mortality. There are three deployment / migration population, namely (1) emigration is the movement out, (immigration) movement into and (3) migration is going (out) and back (sign periodically).

B.     Population Growth

Population growth is a central process in ecology. Because there is no population that grows continuously so we know their population regulation. The interaction of species such as predators, competition, herbivory and disease impact on pop growth and population growth resulted in changes in community structure is therefore very important to know how a growing population.

A population that is released in a suitable environment, will continue to increase in number. In the life cycle of the organism there are phases of birth, growth, mature, old and then die. In ecology Boden Heimer (1938) divides the age of the animal in three periods, namely the phase of preduktif, where animals experienced rapid growth but has not been able to produce, reproductive phase, in which the animal is able to reproduce, the phase of post-reproductive, where the animals are no longer able to reproduce that at the age of old.

Model Population Growth

Population Growth Model(PopulationGrowth)

1.      Model Continuous Time

Models Continuous Time is the model used to determine the number of plants that exist in the foreseeable future. In this model, the individual develops is not limited by the environment such as competition and limitations will supply the food. The rate of population change can be calculated if the number of births, deaths and migration is known. Predictions that the population number will grow continuously first coined by Malthus (1798). Population dynamics can in approximation to this model only for a short period only.

Using this model we can determine the number of plants that exist in the foreseeable future (Nt), the amount of which is formed from seed produced by existing plants (B), and scattered on the site (I), then reduced by the amount already dead (D), and the number of seeds that are spread out area (E) during the time period t to t + 1.

Continuous models can be accumulated using the equation:

N_{t + 1}= N_t + B + IDE

Nt: number of plant populations that exist in time t.

B: the number of births per unit time

I: The number of arrivals per unit time

D: the number of deaths per unit time

E: total population out per unit time.

2.      Matrix Model

One model of growth that is most often used by experts demogragi is Leslie matrix model, which was developed in the 1940s. This model explains the growth in population reproduction in plants. In this model plant reproduction are divided into classes or mathematically

Thus if we know the initial distribution of x (0) and Leslie matrix (L), then we can determine the distribution of plant reproductive age at any time in the future. Matrix model is a model that allows the determination of population growth in plants with the exact calculation of the time period, and phase can be determined from the direction of living plants. Matrix model is very profitable when the unit of the population moving from a stage of growth which can be specified to another.

a.       Matrix that consists Top Single Column Column referred to as matrix. Column matrix can show the number of individuals and each stage of development. For example, the number of seeds (N_), the number of plants in the form of a rosette (N_) and the number of plants in phase of flowering (N +)

b.      Matrix of transition, a transition matrix for the three stages of the growth is a rectangular shape and consists of a group of probability values which presents the change whereby plants in particular the development stage will reach different developmental stages (or stay the same) during the period between the date of the population census.

3.      Carrying (Carrying Capacity)

Given the various constraints that exist, we can estimate that the environment has a carrying capacity, ie the number of individual species that can be supported by the environment. Carrying capacity can be determined not only by the number of individuals in the population, but also by the size and rate of growth of individuals in the population.

Environmental carrying capacity implies the ability somewhere in supporting optimum living creatures in a long time period. Environmental carrying capacity can also be interpreted capability provides living organisms environment and sustainable prosperity for the people who inhabit an area. The carrying capacity of the environment shows the magnitude ability to support plant life.

But the population of ordinary plants produce only a brief period during the year, and not all plants reach the reproductive adult. Intermediate growth in plants making the number of individuals as an indicator of unfavorable about the resource needs of the population.

4.      Exponential population growth

population growth exponential model describes an ideal population in a restricted environment. Shall, if a curve showing population growth in a variety of different times, it will obtain the curve shape of the letter J. The exponential growth have equal = No e^rt or  dN/dt  = r N, where

No       = Number of initial population, at time t = 0

Nt        = Total population at time t

e          = Base of natural logarithm

r           = Konstante / scr growth intrinsic reasonable speed.

dN       population change= Speed / pd given moment of time.

dt         time interval=

5.      Density Dependent

All individuals in a population of plants will require common, so that every individual in the population to be on par to be occupied by other individuals. Is it because of genetic differences or microhabitat, some people get more of the share in the resources, and they are growing faster than in the same plant size.

The result is a multilevel self thinning on very dense population, because a certain individual plants will die, while others mendominer upright. Plant death due competence and dense stands of the same age to follow the pattern can be determined. Dependent density is the number of individuals per unit of a particular area that existence is influenced by influencing the situation.

6.      Dependent Population Dense

Population is dependent dense population size continues to increase as predicted by most models of population growth, the population is dependent on the density dependent changes in survival or production rate because the population becomes larger. We know that the law of constant yield where plants against luxuriance not only by the density but also to the individual. It is more accurate to say that the population growth is more dependent than dependent Dependent dense

7.      Stadia Versus Age

Classic wear age demographic theory as the basis for estimates of fertility and survivorship. However, age may also not be an indicator of reproductive status in plants. There are two main reasons are:

a.       The size does not need to be correlated with age

b.      Many plants will bloom when it reaches a certain size regardless of its age.

In contrast, in an optimal environment, the necessary size and carbohydrate deposits may be collected quickly and flowering can occur within the first year of growth. Seedling trees remain small for several years when grown in the shade of a dense forest. This is a development stage which determines the demographic status of the individual, not about age.

8.      Life Tables

There are two types of life tables based on length of life of individuals in the population:

-       A dynamic table. Used observers to follow the growth of germination at a certain time until all the individual dies

-       Static life table. The table which measures the age structure of a population to estimate the survival patterns of various age groups in a population.

9.      Survivorship Curves

That is the number of survivors at each age interval to time will yield a survivorship curve.

There are 3 types of survivorship curves serving a population of extreme responses:

-       Type 1: survivorship curve is characteristic of organisms with low mortality and mortality in young stadia rapidly in old age.

-       Type 2: a straight line, wherein substantially the same probability of death at any age.

-       Type 3: Typical organisms that have high youth mortality rate, followed by seed mortality due to their eating fruit and seed eaters.

10.  Fecundity

Fecundity generally means the ability to reproductions. In biology, fecundity is the actual reproductive rate an of organism or population as measured by the number of gametes, seeds, or propagula asexual. In the field of demography, fecundity is the potential reproductive capacity of an individual or population. Fecundity is undercontrol genetic and the environment and is the primary measure of biological fitness of a species. Also called age-specific rate of birth of the individual or the birthrate is measured by counting the total number of seeds produced during each interval age and divided by the number of individuals living.