Population Pyramids

They are a useful graphic, also called age-sex pyramids, representation that give us the information to analyze population distribution and population change

Population numbers are the x-axis and age groups are on the y-axis.

*As we can see it can also be focused on only one sector of the population.

It shows:

• How many individuals are alive in different age groups cohorts in a country or region for any given year.
• Show the male-female ratio

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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 the middle age, slightly 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 expectanxy

LEDC’s tend to be in stage 1 and 2, while MEDC’s are in the 3 and 4 stages.

The measuring Roll

The measurements information is used to value the state of things (good or wrong) and then act towards control the variables.

The methods for measuring biomass vary between ecosystems, biomes and type of organism.

It is important in the vegetation measurement, representing an indicator of productivity and of ecological and management processes in the vegetation.

Vegetation biomass measuring tell us what plant dominates a land by controlling the nutrients and water resources. Estimates of biomass and residual biomass also strongly influence the hydrologic properties of the site including infiltration, runoff, and erosion. Biomass of both grasses and woody plants constitute potential fuels that can be measured to assess the risk of wildfire.

Biomass can be directly measured with little training, although, it is time consuming.

*http://www.global-greenhouse-warming.com/measuring-biomass.html

The above MODIS Enhanced Vegetation Index (EVI) map above shows the density of plant growth over the entire globe. Very low values of EVI (white and brown areas) correspond to barren areas of rock, sand, or snow. Moderate values (light greens) represent shrub and grassland, while high values indicate temperate and tropical rainforests (dark greens). The MODIS EVI gives scientists a new tool for monitoring major fluctuations in vegetation and understanding how they affect, and are affected by, regional climate trends.

The biomass of a trophic level is likely to be proportional to the number of organisms and the energy found in each level. This could be graphically shown by the use of the ecological pyramid, which are graphical representations of the trophic structure of ecosystems:

*http://scienceaid.co.uk/biology/ecology/food.html

References.

http://www.cnr.uidaho.edu/veg_measure/Modules/Lessons/Module%206/6_2_Why%20Measure%20Biomass.htm