Short notes for Enviro and Formulae needed for exam

BIRTH AND DEATH

A species- includes all individuals that are capable of inter-breeding.

A population- This is a group of individuals of the same species, living in the same area or inter-breeding and sharing genetic information.

The rapid change in a population depends on growth rate.

Demographics – this is the study of population.

Birth Rate – This is the number of live births in a year, measured per 1000 people. It relates the number of births to the total population.

Factors affecting birth rate

Age structure Infant mortality Child labour Social services

Religion and culture Status and education level of women Contraception and abortion Government policies

Fertility Rate – This is a more specific measure; it is the number of births in a year per 1000 women in the normal reproductive age range.

This is also the average number of children a woman may be expected to have throughout her childbearing years.

Death Rate – this is the number of deaths in a year, measured per 1000 people. It relates the number of deaths to the total population.

The Infant death rate or Infant mortality rate – is the number of infant deaths in a year, measured per 1000 live births. In other words, it relates the number of children in a year who die before they are a year old, measured per 1000 live births.

Factors affecting death rate:

Health, public health care Natural disaster Genocide Nutrition, diet and lifestyle Medical care War Age structure Diseases

Rate of Natural Increase – This is the difference between the birth rate (per 1000) and the death rate (per 1000). (Now this is called the rate of natural increase only if it is a (+) no. But if it is (-) it is known as the rate of natural decrease).

Natural increase (or decrease) = birth rate-death rate x 100 = __% 1000

Doubling Time – this is the number of years that it takes for a population to double, assuming a constant rate of natural increase.

Calculating double time (1. Assume the population is growing exponentially or constant. (2. Estimation value is 70

(3. Double time =_______ 70_______ annual growth rate

The maximum lifespan/time – is the genetically determined maximum possible age to which an individual of a species can live.

Life expectancy – is the average number of years an individual can expect to live, given their sex, culture, country and social status.

FORMULAE

Fertility Rate = number of live births__________ x 100% number of fertile women x 1000

Birth Rate = b = B x 100% N

Death Rate = d = D x 100% N

Migration Rate = I (number of migrants) E (number of emigrants) = (I-E) per 1000 population

Growth rate = If the net migration or (I-E) = 0 = g = B-D x 100% N

And now if the growth rate isn’t zero = g = B-D + net migration x 100% N

Population Growth – The size of a particular species is usually expressed as the number of individuals per unit area

Density of Population growth may be affected by;___Depletion___Migration___Birth Rate___Death Rate

Carrying Capacity of a Habitat – A population tends to stabilise at a level the habitat can tolerate or support on a sustainable basis for an indefinite period.

Exponential Growth – this is defined as growth in which the rate of increase is a constant percentage of the current size. This occurs at a constant rate per time period.

FOOD CHAINS AND WEBS

Food chain - is the sequence of nutrition that leads from the producers to the top carnivores. - it consist of a series of organisms through when the organic compounds initially produced by plants or other autotrophs are transferred.

Trophic levels – this is the levels in a food chain.

A tophic level – is the stage in a food chain at which the organisms all obtain their food in the same general manner.

The niche – is a full range of physical and biological conditions in which an organism lives and way that it uses those conditions. --- Fundamental niche – a niche that a species would occupy in absence of any competitor, predator or parasite --- Realistic niche – the niche that the species actually occupies

Ecological pyramidsAll three

Pyramids of numbers Pyramid of biomass Pyramid of energy

Pyramid by numbers characteristics

Ecosystems are populated by very large numbers of small animals and smaller numbers of larger animals.

Predators are larger than prey and are able to catch or overpower the prey relatively easily. Because the prey is small, it takes the predator a long time to collect sufficient food. A surplus of small organisms to power the food chain.

The Environment Climax – This is the maximum amount of organisms the environment can sustain

Ecological Succession – Ecological Succession is the process by which organisms occupy a site and gradually change the environmental conditions so that other species can replace the original inhabitants.

CYCLES

The Phosphorus Cycle

Nitrogen Cycle

Water cycle

Carbon cycle

SOIL WATER AND RIVERS

HUMANS AND THE ENVIRONMENT