World Population Growth

Natural population increase: When birth rates are higher than death rates, like in stage 2 and 3 of the DTM.

Natural population decrease: When death rates are higher than birth rates, like in stage 5 of the DTM.

A country's population can also be changed by immigration and emigration, but when there is reference to natural change, it only refers to changes caused by birth rates and death rates.

Population explosion or population bomb: The rapid growth in population, this might refer to the rapid growth of the world's population in the lat 100 years, or the rapid population growth of just one country.•Reasons for high birth rates include:
Lack of education about family planning
•Poor availability of contraception and cost of contraception
•Polygamy amongst some ethnic groups
•Primary based economy
•High rate of sexual violence often leading to unwanted pregnancies
•
Reasons for declining death rates include:
Better testing for and treatment of HIV/AIDS
•Improved water supply
•Improved housing (although large numbers still live in informal settlements)
•Better education about diet


South Africa also receives large numbers of migrants from countries like Zimbabwe, Mozambique and Swaziland. This is either because of lack of economic opportunities in these countries and/or political problems.
















What is population structure and population pyramids?
•Population structure is usually shown using a population pyramid. A population pyramid can be drawn up for any area, from a whole continent or country to an individual town, city or village.
•Population structure means the 'make up' or composition of a population. Looking at the population structure of a place shows how the population is divided up between males and females of different age groups.


Young Dependents: The number or the percentage of the population under the age of 16.

Old Dependents: The number or the percentage of the population over the age of 65.

Economically Active: People between the ages of 16 and 65. This is basically the working group.

Obviously some people stay at school past the age of 16, some people retire before 65 and some people work after 65. Also some people between 16 and 65 might unemployed. However, when we are look at entire populations we have to look at averages (the norm).

Dependency Ratio: The ratio between the amount of dependents (old and young) and the economically active.







Key things to know about population pyramids
•The shape of a population pyramid can tell us a lot about an area's population.
•It gives us information about birth and death rates as well as life expectancy.
•A population pyramid tells us how many dependants there are. There are two groups of dependants; young dependants (aged below 15) and elderly dependants (aged over 65).
•Dependants rely upon the economically active for economic support.


•Many LEDCs have a high number of young dependants, whilst many MEDCs have a growing number of elderly dependants.




How do pyramids change over time?
•A population pyramid that is very triangular (eg Mozambique in 2000) shows a population with a high number of young dependants and a low life expectancy.
•
•A population pyramid that has fairly straight sides (more like a barrel) shows a population with a falling birth rate and a rising life expectancy.
•
•Over time, as a country develops, the shape changes from triangular to barrel-like.
• Places with an ageing population and a very low birth rate would have a structure that looks like an upside-down pyramid




Migration: The movement from one location to another location.

There are many different types of migration. The most commonly referred to are:


Rural-urban migration: This is a type of internal migration. It is the movement of people from rural areas

(the countryside) to urban areas (towns and cities). In the settlements topic we look at the causes, problems

and solutions of and to rural-urban migration in Rio de Janeiro.
International Migration: Migration between countries e.g. El Salvador to US.

Temporary Migration: Migration for a limited period, this might only be for a few weeks or even several years.

Permanent Migration: Migration with the intention of staying forever.

Forced Migration: When people are forced to migrate, often because their life is in danger.

Voluntary Migration: When people freely choose to migrate e.g. for better weather or better universities.

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Posted in: Biology,EVM

HABITAT DESTRUCTION AND ITS EFFECTS ON SPECIES

Species becoming extinct is a natural process.
ÒIt is part of evolution eg: dinosaurs
ÒThe worry today is the alarming increase in the rate of extinction due to human actions.
ÒHabitat loss is the main reason.


ÒIncrease in population –land used for farming, industries, cities etc.
§They support habitat with high biodiversity.
§They contain useful food resources and raw materials
§They improve soil structure, depth and fertility.
§They prevent or slow down soil erosion.
§They are an important part of the water cycle.
§They are major carbon store or sink.
•These are ecosystems dominated by water.
•They include swamps, marshes, lakes and deltas.
•The water can be stagnant or flowing,
•Fresh or salty.
•They are like kidneys of the landscape.
•They maintain water quality and encourage plant growth.
•They are highly productive ecosystems with rich plants, fish and water birds.
•They absorb and store water.


•Store carbon.
•Rich fisheries, reeds and other building materials,
•Also used for recreation.


The service industries which benefit from tourism include transportation services, such as airlines, cruise ships, and taxicabs; hospitality services, such as accommodations, including hotels and resorts; and entertainment venues, such as amusement parks, casinos, shopping malls, music venues, and theatres.
•Coastal environment is very fragile and habitats are vulnerable.
•Natural movement of sand are blocked by jetties.
•Tropical mangroves are cleared for resots.
•Corals are easily damaged by divers.

•Cruise ships and glass bottomed boats put down anchor that dig into soil and habitat
•Gene banks to preserve a wide range of plants and animals .but it is not perfect because gene banks are vulnerable to disease, human error and accidents.

•The only secure way to preserve the full range of genes for future is to protect plants and animals growing in their natural environment.



•Biosphere reserves are areas of terrestrial and coastal ecosystems promoting solutions to reconcile the conservation of biodiversity with its sustainable use.
• They are internationally recognized, nominated by national governments .
•Biosphere reserves serve in some ways as 'living laboratories' for testing out and demonstrating integrated management of land, water and biodiversity.


•There are over 500 biosphere reserves in over 100 countries.
•The origin of Biosphere Reserves goes back to the "Biosphere Conference" organized by UNESCO in 1968.
•launched the UNESCO "Man and the Biosphere" (MAB) Programme in 1970.

Each biosphere reserve is intended to fulfil 3 basic functions, which are complementary and mutually reinforcing:



- a conservation function - to contribute to the conservation of landscapes, ecosystems, species and genetic variation;
-a development function - to foster economic and human development which is socioculturally and ecologically sustainable;
- a logistic function - to provide support for research, monitoring, education and information exchange related to local, national and global issues of conservation and development.

Biosphere reserves are organized into 3 interrelated zones:

- the core area

- the buffer zone
- the transition area

. 

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Posted in: EVM

HABITAT DESTRUCTION AND ITS EFFECTS ON SPECIES

 YouTube Link:https://www.youtube.com/watch?v=gS29dsOz1JQ

YouTube Link:https://www.youtube.com/watch?v=NyVI2tiRBeE

•Species becoming extinct is a natural process.

•It is part of evolution eg: dinosaurs

•The worry today is the alarming increase in the rate of extinction due to human actions.

•Habitat loss is the main reason.

•Increase in population –land used for farming, industries, cities etc.

FOREST –WORTH SAVING?

•THEY SUPPORT HABITAT WITH HIGH BIODIVERSITY.

•THEY CONTAIN USEFUL FOOD RESOURCES AND RAW MATERIALS

•THEY IMPROVE SOIL STRUCTURE, DEPTH AND FERTILITY.

•THEY PREVENT OR SLOW DOWN SOIL EROSION.

•THEY ARE AN IMPORTANT PART OF THE WATER CYCLE.

•THEY ARE MAJOR CARBON STORE OR SINK.

WETLANDS- WORTH

SAVING?

•THESE ARE ECOSYSTEMS DOMINATED BY WATER.

•THEY INCLUDE SWAMPS, MARSHES, LAKES AND DELTAS.

•THE WATER CAN BE STAGNANT OR FLOWING,

•FRESH OR SALTY.

•THEY ARE LIKE KIDNEYS OF THE LANDSCAPE.

•THEY MAINTAIN WATER QUALITY AND ENCOURAGE

PLANT GROWTH.

•THEY ARE HIGHLY PRODUCTIVE ECOSYSTEMS WITH

RICH PLANTS, FISH AND WATER BIRDS.

•THEY ABSORB AND STORE WATER.

•STORE CARBON.

•RICH FISHERIES, REEDS AND OTHER BUILDING

MATERIALS,

•ALSO USED FOR RECREATION.

WHAT ARE THE IMPACTS OF TOURISM?

•THE SERVICE INDUSTRIES WHICH BENEFIT FROM TOURISM INCLUDE TRANSPORTATION SERVICES, SUCH AS AIRLINES, CRUISE SHIPS, AND TAXICABS; HOSPITALITY SERVICES, SUCH AS ACCOMMODATIONS, INCLUDING HOTELS AND RESORTS; AND ENTERTAINMENT VENUES, SUCH AS AMUSEMENT PARKS, CASINOS, SHOPPING MALLS, MUSIC VENUES, AND THEATRES.

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Posted in: EVM

Ecosystem

Video:https://www.youtube.com/watch?v=xIVixvcR4Jc

Video:https://www.youtube.com/watch?v=5WECs5-jNlc

Video:https://www.youtube.com/watch?v=eo5XndJaz-Y

•Communities are well ordered and integrated in an ecosystem.
•There is intense competition b/w living organisms for the available resources.
•Every organisms has a role in the functioning of the ecosystem (niche)
•It is an important rule of nature ,that communities should be made of species that have different needs for resources,so that each can have different positions.
•Hence ensuring that natural resouces available

Vegetative succession

•When a new surface is created due to landslide or volcanic eruption.
•Sequence of events results in an area covered by vegetation.
•The change in vegetation is called plant succession.
•The 1rst organism to colonize the area is the pioneer community-on rocky surface,its usually the lichens and mosses,that do not need soil to survive.
•Lichens and mosses gradually break the rock into particles of sand, silt and clay, when they die, they adds humus to soil.
•Hence deeper and richer soil is made.
•Eventually grasses and herbs grows,
•Wind ,birds and animals bring seeds.
•Eventually trees grows.
•Dominant trees and species forms the climax

PHOTOSYNTHESIS

•Green leaves use light energy to combine carbon dioxide and water together to make glucose and oxygen.
•This process is called photosynthesis and takes place in the leaves of green plants.
•Chlorophyll is a green chemical found in plant cells which is essential for photosynthesis because it captures light energy from the sun and converts it into chemical energy.

STOMATA

•The carbon dioxide which a plant uses diffuses into the leaf through the stomata.
•If the stomata are closed ,then photosynthesis cannot take place.
•Stomata often close if the weather is very hot and sunny ,to prevent too much water being lost.
•This means that really hot day photosynthesis may slow down.

What is trophic levels?

The trophic level of an organism is the level it holds in a food pyramid. The sun is the source of all the energy in food chains. Green plants, usually the first level of any food chain.

Energy flow in food chains

•The amount of energy at each trophic level decreases as it moves through an ecosystem.
• As little as 10 percent of the energy at any trophic level is transferred to the next level; the rest is lost largely through metabolic processes as heat.
• If a grassland ecosystem has 10,000 kilocalories (kcal) of energy concentrated in vegetation, only about 1,000 kcal will be transferred to primary consumers, and very little (only 10 kcal) will make it to the tertiary level.

• Energy pyramids such as this help to
explain the trophic structure of an
ecosystem: the number of consumer
trophic levels that can be supported is
dependent on the size and energy richness
of the producer level.

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Posted in: EVM