Biology BIOLOGICAL ORGANISATIONS IN ECOLOGY

### KEY TOPICS

star Introduction
star Biomes
star Key factors causing Habitat Variations

### INTRODUCTION

● Our living world is color{violet}("fascinatingly diverse") and color{violet}("amazingly complex").

● We can try to understand its color{violet}("complexity") by investigating processes at various levels of biological organisation–color{violet}("macromolecules, cells, tissues, organs"), color{violet}"individual organisms, population", color{violet}("communities and ecosystems") and color{violet}("biomes").

● At any level of color{violet}("biological organisation") we can ask two types of questions….

● For example, when we hear the bulbul singing early morning in the garden, we may ask – color{violet}("‘How does the bird sing?’") Or, color{violet}("‘Why does the bird sing?’ ")

● The ‘how-type’ questions seek the mechanism behind the process while the color{violet}("‘why type’") questions seek the color{violet}("significance of the process").

● For the first question in our example, the answer might be in terms of the color{violet}("operation of the voice box") and the color{violet}("vibrating bone") in the bird, whereas for the second question the answer may lie in the bird’s need to color{violet}("communicate with its mate during breeding season").

● color{violet}("Ecology") is a subject which studies the color{violet}("interactions among organisms") and between the color{violet}("organism") and its color{violet}("physical (abiotic) environment").

● color{violet}("Ecology") is basically concerned with four levels of color{violet}("biological organisation – organisms, populations, communities") and color{violet}("biomes.")

### BIOMES

● Ecology at the organismic level is essentially color{violet}("physiological ecology") which tries to understand how color{violet}("different organisms") are adapted to their color{violet}("environments") in terms of not only color{violet}("survival") but also color{violet}("reproduction").

● It is known that the rotation of our planet around the Sun and the tilt of its axis cause color{violet}("annual variations") in the color{violet}("intensity") and color{violet}("duration of temperature, resulting in distinct seasons").

● These color{violet}("variations") together with color{violet}("annual variation") in color{violet}("precipitation (precipitation includes both rain and snow)") account for the formation of color{violet}("major biomes") such as color{violet}("desert, rain forest") and color{violet}("tundra") .

● On planet Earth, life exists not just in a few favourable habitats but even in extreme and harsh habitats – color{violet}("scorching Rajasthan desert"), color{violet}"perpetually rain-soaked Meghalaya forests", color{violet}"deep ocean trenches", color{violet}"torrential streams", color{violet}("permafrost polar regions"), color{violet}"high mountain tops", color{violet}("boiling thermal springs", and color{violet}("stinking compost pits"), to name a few.

● Even our intestine is a unique habitat for hundreds of species of color{violet}("microbes.")

### KEY FACTORS CAUSING HABITAT VARIATIONS

● There are some key elements that lead to so much color{violet}("variation") in the color{violet}("physical and chemical conditions") of color{violet}("different habitats").

● The most important ones are color{violet}("temperature, water, light and soil").

● It is important to note that the color{violet}("physico-chemical (abiotic)") components alone do not characterize the habitat of an color{violet}("organism completely").

● The habitat includes color{violet}("biotic components") also – color{violet}("pathogens, parasites, predators and competitors") – of
the organism with which they interacts constantly.

● We assume that over a period of time, the organism had through natural selection, color{violet}("evolved adaptations to optimise") its color{violet}("survival") and color{violet}("reproduction") in its habitat.