To understand the basics of Marine Population Modeling, we first have to take a look on the concepts of Population Modeling. So, we are going to make an analysis and gather some bibliography on Population Modeling before we start in Marine Population.
The first approach in this blog will be about Populations Modeling, as you can see:
Individuals tend to have offspring, so the populations of this individual tend to grow. But, as this individual grows, it also dies due to late age. The growth rate is the difference between the newborn individual and the individuals that died. Its important to notice that the growth rate will be positive if more individuals were born then the individuals that died. So, we can first classify our first variable, called Growth rate. In our analysis we are going to call this variable the letter “R”.
Most populations don’t grown indefinitely. They have a resource capacity such as food, shelter, predators, diseases. So, each population have its maximum limit of stability, based on its relation to the environment. We call this limit Carrying Capacity, and it determinates on how much a population can grow in such environment. In our analysis we are going to call this variable the letter “K”.
Things that limit the population growth comes in two forms:
Density dependent factors: The amount of these factor affect the population directly related to its population density. Such factors are: Food, Water, Shelter, Desease, Predation.
Density Independent Factors: These factors do not depend on the population density. Such factors are: weather, climate.
We can make an analogy of the population with a bucket being filled with water. The growth rate is the amount of water that is entering in the bucket. At first, there is no water, so the water level of the bucket will rise as the same rate as the water comes in. Later on, the bucket will be filled totally with water, and will star to pour the exceeding water out. The amount of water that comes out of the bucket symbolizes the population loss, due to various causes. The following image illustrates this:
But, this representation is not so accurate because the volume of water that was initially in the bucket was zero, and in that case, the population would be extinct. By the way, is a good analogy at first, just to illustrate the problem.
In real situations, the population will grow to a level higher than the carrying capacity. When this happens, the death rate will bi higher, making the population to decrease, as seen in the following image:
This will oscillates around the carrying capacity level. This cycles repeats itself, and each cycle it gets less drastic over time, like a dumped oscillation. The following image illustrates this:
We are going to have two Growth patterns. These growth patterns depends on witch species we are analyzing, based on its procreation and lifestyle characteristics.
R-Selected Species:
Species that grow exponentially when the environment allows it. Results in temporary large population. Such as bacteria, cockroach, fungus, ants.
Characteristics:
Short life spans
Reproduce Early in life
Create lots of offspring each time they reproduce
Offspring are small
Offspring mature rapidly, with little/no parental care
K-Selected Species:
Species that have mature populations near carrying capacity (K) of their environment. Such as Elephants, Wales, Humans.
Characteristics:
Long life spans
Few young
Slow maturation process
Reproduce late in life
Tend to provide care to their young
Tend to live in stable environment
With all this information, we can give our first step for our main goal: Modeling a Marine Population.
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