Population Pyramids :D

There are different types of Pyramid Shapes:


Stage 1 Expanding: High CBR, rapid fall in each upward age group due to high CDR, short life expectancy.


Stage 2 Expanding: High CBR, fall in CDR as more individuals live to middle age, slightly longer life expectancy.


Stage 3 Stationary: Declining CBR, low CDR, more individuals live to old age.


Stage 4 Contracting: Low CBR, low CDR, higher dependency ratio (those that cannot work), longer life expectancy.


LECD tend to be stage 1 or 2, while MEDC are in stages 3 or 4.

Sustainable Yields :D

Sustainable Yield: natural income that can be exploited each year without depleting the original stock or affecting its potential for replenishment.


There are several concepts involved when calculating the sustainable yield of an ecosystem, such as the carring capacity (K), the population size , and  biomass of the ecosystem. 


In order to calculate the Sustainable Yield, the following formulas should be applied:


SY= Annual Growth and Recruitment - Annual Death and Emigration


This formula measures the inputs and outputs that an ecosystem has, by considering the number of individuals that enter or are born in the ecosystem minus the number of individuals that leave or die.


Another formula used by measuring the sustainable yield available in an ecosystem is:


SY= (Total Biomass or energy at a Time T)+1 - (Total Biomass or energy at a Time T)


This formula consideres the change in biomass in an ecosystem between a period of time.

Economy... Systems... Economic Systems :O

An economic system is a system that distributes goods and services by using different types of resources. The main objective of economic systems is to satisfy people's needs and wants in the must effective and efficient way.   Economic systems, as any other system, requires an input (in this case resources) and has an output (which means the goods and services)

The resources used by an economic system, can be classified into 3 different categories:

• Natural Capital
• Human Capital
• Manufactured Capital

Natural resources, which are the ones provided by Natural Capital, are classified in the following categories:

• Renewable
• Non renewable
• Replenishable
• Recyclable

Sustainability :P

Sustainability is a word that is being very used lately by everyone. We find this word in many places, such as TV,  Newspapers, radio, etc. but we don't really know its meaning. So how can we define it? Why is this word so important for us?

Sustainability involves many concepts that lead to taking care of what we have and making it work, but always taking care of the impact that our actions have and trying to do the best, not only for us, but for everything around us. Sustainability, also involves many actions that we as humans can perform in order to take care of our planet, such as using only the resources we need, being responsible with this usage, taking care of nature and environment and educating everyone else in all the actions they can do in order to have a sustainable life or being a sustainable person :)

Biomass!!! :D

What is biomass? Why is it important?

Biomass is the ammount of organisms living in a certain area. Biomass can be measured for knowing the state of an acosystem, since it studies the ammount of energy available in an ecosystem. This will be useful, because by knowing the energy present in the ecosystem, we can know how many species will be able to live in there. 

How to measure Biomass?

There are several ways for measuring biomass, each of them has advantages and disadvantages in the process and results given:

• Obtaining the weight of an organism and multiply it times the ammount of organisims living in the area. The units are grams per meter squared. The disadvantage of this method is that it is difficult to know accurately the number of organisms of each specie, which in case of error, will highly modify the result of the measurement.
• Transect method, consists on tracing an imaginary line across the selected ecosystem, and counting the organisms that are in the quadrants following the transect.
• Quadrant method, is another method for measuring biomass in which an area is determined and  biomass is measured by applying other methods but only in the specified area.

 What about an estuary?
After biomass is collected at different trophic levels, a biomass pyramid can be made. Here's an example of an estuary, more specifically, Chesapeake Bay. Taking the following food chain:

phytoplankton -> clams -> blue crabs -> sandbar sharks

Firstly, the units will be measured in kg per cubic kilometer, since it is a aquatic ecosystem. We can calculate the amount of each species in the food chain, and we get the following information:

There are 31,333,333 units of phytoplankton in 2320 cubic km of water in Chesapeake Bay.
There are 9,200,000 clams in that same area.
There are 278,666 blue crabs.
There is one sandbar shark.

Then, considering the weight of each specie and the area, we can calculate biomass, which then can be shown in what is known as a biomass pyramid.

Biodiversity :D

Biodiversity is defined as the variety of all forms of life, from genes to species, through to the broad scale of ecosystems.  

Biological diversity can be quantified in many different ways. The two main factors taken into account when measuring diversity are richness and evenness. Richness is a measure of the number of different kinds of organisms present in a particular area. For example, species richness is the number of different species present. However, diversity depends not only on richness, but also on evenness. Evenness compares the similarity of the population size of each of the species present.

 A diversity index is a statistic  intended to measure the differences among members of an ecosystem consisting of various types of objects. There are different types of diversity indexes such as:

• Simpson's Diversity Index: measures the probability that two individuals randomly selected from a sample will belong to the same species. It is measured by the following formula:

When apllying the formula, the value that we can obtain starts with 1, representing a community of only one specie. The higher the value obtained, represent greater diversity.

To calculate Simpson's Index for a particular area, the area must first be sampled. The number of individuals of each species present in the samples must be noted. 

• Shannon's Diversity Index: Is another diversity index used for characterize diversity in a community. It accounts for both abundance and evenness of the species present. The formula for applying this index is:

• 
  

  Berger-Parker Diversity Index: Number of individuals in the dominant taxon relative to n

Organizing Organisms...

Because of the enormous amount of species in our planet, it is neccesary to classify them using a logical order. The most used system for achieving this organization, is the binomial nomenclature. This system was developed by Carolus Linnaeus. There are seven classification levels:

• Kingdom
• Phylum
• Class
• Order
• Family
• Genum
• Species

In the generally accepted system there are 5 kingdoms:

• Animalia
• Plantae
• Fungi
• Protista
• Monera

Dichotomous Key is a method of organizing organisms based on characteristics. Organisms paired  with a series of direction that leads to increrasingly more specific descriptions of an organism, ending when a group containing all of the relevant characteristics found.