N= the total number of organisms of all species n= the total number of organism of a particular species.
Measuring abiotic factors
Acuatic ecosystem: ph (water acidity, PH meter or litmus paper), salinity (hydrometer), Temperature (determines soluvility of oxygen, thermometer), dissolved oxygen (oxygen sensor), flow velosity (impellor measure), turbidity(cloudiness of water, nephelometric).
Terrestial ecosystem: temperature (thermometer), light intensity (footcandle meter), wind (anemometer), mineral content (important for soil water holding capacity), particle size, slope (use water in a bottle).
Using Biological Dichotomous keys
Biological keys: groups of organisms that have several characteristics (invertebrates).
Dichotomous keys: helps the scientists to identify stuff in nature by asking simple yes/no questions.
Resources
Natural capital: resources that nature gives you, reserves. It is not manufactured. (Trees, living organisms).
Natural income: it is what we can get from natural capital. (Fresh water, wood, food,).
Types of natural capital:
Renewable: can replece themselves usually with the sun as source of energy, but can disappear if not harvested sustainable. (fish, trees).
Non-Renewable: finite amounts. (oil)
Replenishable: takes time to restorage, but on a human existence scale. (ground water)
Reciclable: can be transformed into usable materials after being used. (aluminium).
Sustainable Yield: the highest rate at which a renewable resource can be used indefinitely without reducing its available supply.
SY= (Total Biomass or energy at time t+1) – (total biomass or energy at time t)
SY= (annual growth and recruitment) – (deaths and emigration)
Population Dynamics
Remember that the space between the initial phase and the K is the environmental resistance. It is usually the exponential rate.
Human developing index, measures the well being of a country (life expectancy, standarts of living, education, and GDP).
Economically, countries are divided between MEDC (industrialized, high GDP) and LEDC (low gdp, poverty, resources exported to MEDC, high population growth rates).
To measure population changes use the following:
Crude birth rate: the number of births per 1000 individuals in a population per year.
CBR= # of birth *1000
total population
Crude death rate: the same as the last one.
Natural increase rate: NIR = (CBR – CDR) / 10 (births – deaths)/10
Doubling time: Time it takes a population to double its size. Doubling Time = 70 / NIR
Fertility rate: the avarage number of child each woman can have during life time. If it is more than 2 population is increasing…
Thomas Malthus vs. Ester Boserup.
Population Pyramids: Types of pyramids shapes
Stage 1 Expanding: High CBR, short life expectative , big difference of size between each level.
Stage 2 Expanding: high CBR, falling CBR.
Stage 3 Stationary: declining both. More adults.
Stage 4 Contracting: low both, high dependency rate, less births.
Demographic transition models: show the changes in population in relation to economy. Five stages:
Preindustrial, LEDC, Wealthier LEDC, MEDC stable, MEDC decreasing.
Food!!!
Undernourished: those who do not obtain enough energy from what they eat.
Malnourished: those whose food has enough energy, but lack essential vitamins, proteins, etc.
It is important to remember that only 10% of the world land is suitable for growing food, and many people also grow things that cannot be eaten (tobacco, algodon no se como se diga en ingles).
There is enough food in the planet to feed everyone, but the food is not distributed equally and there are political and distribution problems with that (how to carry all the food? Who will pay? How would governments control it?
There are two types of Farming systems:
Subsistence: just for the farmers, their family and their community.
Commercial: large profits, usually monocultures, high technology input.
Extensive: uses more lands and obtains less inputs and outputs, less animal density.
Intensive: intensive use of land, higher inputs and outputs.