Ecology is concerned with the study of organisms and their habitats. This includes the interdependence of various populations, their impact on each other and their surroundings, the effect of the surroundings on their behaviour, as well as the ways in which the organisms and the environment change in response to each other. A pond and its inhabitants provide a good example of these interrelationships. A pond contains: a.
soil consisting of rock, minerals and dead remains of organisms b.
water with minerals
aquatic plants including algae
aquatic animals like snails and tadpoles
bacteria and other microorganisms such as protozoans
All these components interact to produce a system called an ecosystem which is constantly changing. An ecosystem may be divided into physical or abiotic factors and living or biotic components. Abiotic factors may be climatic, physical and chemical. A number of ecological factors are common to both terrestrial and aquatic habitats. Most of these factors are climatic - that is having to do with heat, cold, amount of rainfall or sunshine and so on. Some ecological factors like edaphic (those relating to soil – like pH of soil, water content, drainage and porosity) and topographic ( shape of the land, whether it is mountainous or flat) only relate to terrestrial environments. Other like salinity ( freshness or saltiness of the water) and tidal action ( ebb and flow if the tides)only apply to aquatic habitats.
ECOLOGICAL FACTORS COMMON TO ALL HABITATS
Factors like temperature, rainfall, light, hydrogen ion concentration (pH), wind and pressure are common to all habitats. Temperature
Temperature is one of the main climatic factors. It affects terrestrial habitats more than aquatic ones as the range in temperature is much wider in terrestrial habitats. Temperature variations result in both hot and cold climates. The temperatures of temperate terrestrial habitats have markedly seasonal variations with temperatures below 00C in winter and above 200C in summer. Aquatic habitats experience a vertical variation in temperature with a drop in temperature as the depth increases. In tropical marine waters, the temperature at the surface is about 300C while at a depth of 1500 m the temperature is 40C. Organisms differ in their ability to tolerate variations in temperature. Generally, each organism has its optimum temperature at which it can maintain itself. Poikilothermic animals (cold-blooded) become inactive when the temperature falls to about 60C or rises above 400C. If unfavourable temperatures are seasonal or persist for ling periods, these animals tend to aestivate. Homoiothermic animals (warm-blooded) are able to adapt to temperature changes by maintaining a constant body temperature. In plants, the rate of photosynthesis and transpiration are affected by temperature. Rainfall
Rainfall is another climatic factor that affects mainly terrestrial habitats. Droughts and floods are determined by the amount of rainfall and these can cause the destruction of vegetation covers and as a consequence, community. Rainfall affects the distribution of any kind of vegetation. An annual rainfall of 1600 mm yields an equatorial forest. Rainfall is essential to maintaining the life of freshwater habitats. Lack of rainfall causes drying up of ponds, lakes and streams and consequently death to organisms living there. Plants found living in areas that are aquatic are known as hydrophytes and have adaptations for living in these areas e.g. water lily. Plants found in dry, arid areas are called xerophytes and possess certain adaptations for living there such as stems modified to store water, leaves reduced to spines, sunken stomata and hairy leaves, e.g cactus. Light
Light is needed for photosynthesis to take place. It also affects animals in various ways. Some animals like the earthworm, woodlice and bats shy away from light while others are active by day. Exposure to ultraviolet rays enables man to...
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