Principle ecology | Environmental Geography | Principle Of Geography

Environmental Geography

Principle Of Geography

Geography Complete Study Material

(Paper - I)

Principles of Ecology

            ‘Ecology may be defined as the scientific study of the relationship of living organisms with each other and with their environment.’ The term ecology was first coined in 1869 by the German biologist Ernst Haeckel. It has been derived from two Greek words, ‘oikos’, meaning home or estate and ‘logos’ meaning study. The emphasis is on relationships between organisms and the components of the environment namely abiotic (non-living) and biotic (living).

LEVELS OF ECOLOGICAL ORGANIZATION 

         Ecology not only deals with the study of the relationship of individual organisms with their environment, but also with the study of populations, communities, ecosystems, biomes, and biosphere as a whole.

HABITAT AND ORGANISM 

        Habitat is the physical environment in which an organism lives. Each organism has particular requirements for its survival and lives where the environment provides for those needs. The environmental requirement of an elephant would be a forest. You would not expect an elephant in the ocean nor would you expect a whale in the forest? A habitat may support many different species having similar requirements. For example, a single ocean habitat may support a whale, a sea-horse, seal, phytoplankton and many other kinds of organisms. The various species sharing a habitat thus have the same ‘address’. Forest, ocean, river etc. are examples of habitat. 

       The features of the habitat can be represented by its structural components namely (1) space (2) food (3) water (4) and cover or shelter.

           Earth has four major habitats-(1) Terrestrial (2) Freshwater (3) Estuarine (Where rivers meet the ocean) and (4) Ocean. The human gut is the habitat of a tapeworm and the rotting log a habitat of a fungus.

NICHE AND ORGANISM 

         In nature, many species occupy the same habitat but they perform different functions. The functional characteristics of a species in its habitat is referred to as “niche” in that common habitat. Habitat of a species is like its ‘address’ (i.e. where it lives) whereas niche can be thought of as its “profession” (i.e. activities and responses specific to the species). The term niche means the sum of all the activities and relationships of a species by which it uses the resources in its habitat for its survival and reproduction.

          A niche is unique for a species while many species share the habitat. No two species in a habitat can have the same niche. This is because if two species occupy the same niche they will compete with one another until one is displaced. For example, a large number of different species of insects may be pests of the same plant but they can co-exist as they feed on different parts of the same plant.

           Another example is the vegetation of the forest. The forest can support a large number of plant species as they occupy different niches: the tall trees, the short trees, shrubs, bushes and grasses are all part of the forest but because of varying heights they differ in their requirements for sunlight and nutrients and so can survive together The most important resources in the niches of animals are food and shelter while in case of plants, they are moisture and nutrients (phosphorous and nitrogen).

ADAPTATION 

         Every organism is suited to live in its particular habitat. You know that the coconuts cannot grow in a desert while a camel cannot survive in an ocean. Each organism is adapted to its particular environment. An adaptation is thus, “the appearance or behaviour or structure or mode of life of an organism that allows it to survive in a particular environment”. Presence of gills and fins are examples of adaptation in fishes to aquatic habitat. In aquatic flowering plants absence of wood formation and highly reduced root system are adaptations to aquatic environment. Adaptations that can be observed in structure or behaviour or physiology of an organism. Adaptations have genetic basis and have been produced and perfected through evolution. This means that the adaptions have developed over many generations to help a species survive successfully in its environment. Examples of basic adaptations that help animals and plants to survive in their respective environments. 

• Shape of bird’s beak. 
• The thickness or thinness of fur. 
• Presence of feathers and wings in birds. 
• Evergreen and deciduous nature of trees. 
• Presence and absence of thorns on leaves and stems.

SPECIES FORMATION: SPECIATION 

             The number of species surviving in the world today is the outcome of two processesspeciation and extinction. Speciation is the process by which new species are formed and evolution is the mechanism by which speciation is brought about. A species comprises of many populations. Often different populations of a species remain isolated due to some geographic barrier such as mountain, ocean, river, etc. Geographic isolation occurs when a physical barrier develops between two populations of a species as you can see in fig. 4.8. The most common way a population undergoes speciation is by geographic isolation. 

• The members of a population of a species live in a particular environment and are capable of breeding with the member of another population of the same species. 

• The population then becomes separated into two completely isolated populations by a barrier which prevents their interbreeding and gene exchange. The isolating mechanism may be a physical barrier like water, mountain, ocean represent geographical isolation.

POPULATION 

              ‘Population’ is defined as a group of freely interbreeding individuals of the same species present in a specific area at a given time. For example, when we say that the population of a city is 50,000, we mean that there are 50,000 humans in that city. However, all populations of humans living in any part of the world constitute the species Homo sapiens. A population has traits of its own which are different from those of the individuals forming the population. An individual is born and dies but a population continues. It may change in size depending on birth and death rates of the population. An individual is either female or male, young or old but a population has a sex ratio and age structure, which means, the ratio of male to female in the population and the various age groups into which the population may be divided. The characteristics of any population depends on: (i) density of the population, (ii) natality (birth rate), (iii) mortality (death rate), (iv) dispersal, (v) biotic potential (vi) age distribution (vii) dispersion and (viii) growth form.