Understanding Organismic Ecology: Interactions and Adaptations

Abhipedia IAS Environment & Ecology ORGANISM AND ENVIRONMENT-1 AUTECOLOGY Pritam Sharma Abhimanu IAS ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 1

Abhipedia IAS WHAT DOES ECOLOGY AT THE ORGANISMIC LEVEL INVOLVE THE STUDY OF? As we already know that in Nature no organism can survive alone, it has to depend on other organisms for food or reproduction. But then in Ecological studies, an organism can be studied at the individual level especially when it comes to studying its interactions with its surrounding abiotic environment. Therefore, Ecology at the organismic level is essentially physiological ecology which tries to understand how different organisms are adapted to their environments in terms of not only survival but also reproduction. In short, here we shall understand how does a single organism interact with its surrounding environment and what morphological or physiological changes that it has evolved in so as to be fit and successful in its survival under quite diverse habitats some of which may be too hostile and inhospitable. ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 2

Abhipedia IAS WHY SO MUCH VARIATIONS IN THE PHYSICAL ENVIRONMENT OF AN ORGANISM? The simple answer is the CLIMATE and what that brings about so much variations in the climate of different regions of the world, we also know that it is the temperature and precipitation which include both rainfall and snow fall. And what that influences the temperature and precipitation of the globe is the understanding of our knowledge from geography that it is the rotation of our planet Earth around the Sun and the tilt of its axis that becomes responsible for annual variations in the intensity and duration of temperature across the globe and hence, in the resultant appearance of distinct seasons and hence different climatic zones. These variations together with annual variation in precipitation, eventually, account for the formation of major biomes, such as desert, rain forest and tundra . ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 3

Abhipedia IAS For example, 0-20 degree latitude is the tropical climatic zone, 20-40 degree latitude is the sub-tropical, 40-60 degree latitude is the temprate and 60- 80degree latitude is the Arctic/Antartic zone. Each of these climatic zones hosts a variety of habitats and distinct organisms both plants and animals resulting into the formation of distinct biomes on the planet earth. It must be noted that regional and local variations within each biome lead to the formation of a wide variety of habitats. While the fact remains that on the planet Earth, life exists not just in a few favorable habitats but even in extreme and harsh habitats scorching deserts, perpetually rain-soaked Amazonian forests, deep ocean trenches, torrential streams, permafrost polar regions etc ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 4

Abhipedia IAS FACTORS THAT AFFECT THE ENVIRONMENT OF AN ORGANISM A question may be raised as to what are the key elements that lead to so much variations in the physical and chemical conditions of different habitats? The most important factors that are responsible for this, may be mentioned as below: 1. Temperature, 2.Water, 3.Light and 4. Soil. But as we have noted elsewhere and be repeated here again that the environment or so called the habitat of an organism does not include

Abhipedia IAS only the physio-chemical or abiotic factors but also include the biotic factors such as pathogens, parasites, predators and competitors of the organism with which they interact constantly. In fact, it is these factors which become responsible for the occupation of distinct so called, Ecological Niches by an organism within its habitat. The idea of an ecological niche indicates that no matter how good the abiotic conditions are, an organism may not thrive in its habitat if the same is also a perfect location for its main competitors and predators or for that matter, lacks its preferred food or nesting material etc. this is why, we say that an organism's habitat is determined both by biotic and abiotic factors. This also gives us an answer as to why an organism in a particular place ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 6

Abhipedia IAS not only exists but flourishes as well. Because, this will tell us about what biotic constraints that an organism could face while living in its physical habitat so as to determine its potential niche (where it could occur) including its preferences and behavior that will determine the more restricted range of its so called, realised niche (where it does occur). If two species occupy the same niche, they will generally compete with one another until one is displaced ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 7

Abhipedia IAS HOW DO ORGANISMS BECOME SO FIT TO SURVIVE IN THEIR HABITATS? The simple answer to this benign question is the phenomenon of evolution. In short, one can argue that over a period of time, the organism had through natural selection, evolved such adaptations in the form of physiological or morphological modifications so as to optimize its survival and reproduction in its very habitat. We also know that the nature selects only those who become fit for survival amidst the changes in the surrounding environment meaning thereby that those who are unfit are eliminated in the process of natural selection. In order to understand such of the modifications and adaptations, it is important to go into little details about such environmental or abiotic factors to which an organism has learnt to acclimatize itself with which even holds equally true to human beings as well

Abhipedia IAS MAJOR ABIOTIC FACTORS AFFECTING AN ORGANISM 1. TEMPERATURE: We know that the main source of heat on the planet earth is the Sun s radiation. Although, there are geothermal sources of heat too but that holds importance only in a minority of habitats such as the growth of bacteria in hot springs. Moreover, every one of us may be aware that the average temperature on land varies seasonally, decreases progressively from the equator towards the poles and from plains to the mountain tops. It ranges from subzero levels in polar areas and high altitudes to >500C in tropical deserts in summer. There are, however, unique habitats such as thermal springs and deep-sea hydrothermal vents where average temperatures exceed 1000C. It is general knowledge that mango trees do not and cannot grow in temperate countries like Canada and Germany, snow leopards are not found in Kerala forests. ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 9

Abhipedia IAS This means that temperature is indeed one of the most important ecological factors affecting the life of an organism. This is because, a given organism will survive only within a certain temperature range for which it is metabolically and structurally adapted. We have learnt it from Biology that if the temperature of a living cell falls far below freezing, the cell is usually physically damaged and killed by the formation of ice crystals. At the other extreme, if the temperatures are too high, proteins become denatured. This means that the temperature affects the kinetics of enzymes and through it the basal metabolism, so called as BMR and other physiological functions of the organism. The enzyme controlled reactions and hence metabolic activity double in rate with 10 degree C in temperature.

Abhipedia IAS A few organisms can tolerate and thrive in a wide range of temperatures (they are called eurythermal), but, a vast majority, say upto 99% of them are restricted to a narrow range of temperatures (such organism are called stenothermal). The levels of thermal tolerance of different species determine to a large extent their geographical distribution. This means that there are some organisms which are able to exert some degree of control over their temperature by a variety of responses and adaptations so that extreme and sudden changes of environmental temperature can be smoothed out. Aquatic environments undergo less extreme temperature changes owing to high heat capacity of water and thus provide more stable habitats than terrestrial environments ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 11

Abhipedia IAS LIGHT AS AN ECOLOGICAL FACTOR Sunlight is the only celestial source of light energy which in the first becomes responsible for photosynthesis' in plants. In this sense, light is very essential for the sustenance of life, but then it also influences living organisms in many other ways too. Moreover, it is not only light but its quality such as intensity, quality (wavelength or color) including its duration (photoperiod) can also has profound effect on the life of an organism. Since light is the only source of energy which plants require for photosynthesis, there is even a competition among them for light as we can see in terrestrial ecosystems where competition for light favours certain strategies such as gaining height through growing tall or climbing or increasing leaf surface area. In a woodland, this results in the phenomenon of stratification.

Abhipedia IAS Many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesize optimally under very low light conditions because they are constantly overshadowed by tall, canopied trees. As we noted earlier that it is the duration of light too that affects the living organisms. Among plants this is witnessed in the phenomenon of photoperiodism. At higher altitudes/ latitudes where light varies seasonally, the plants and animals are adapted to show photoperiodic responses that synchronise their activities such as flowering or germination with the seasons. Similarly, the animals also show responses such as hibernation, migration and even reproduction. Finally light quality is also important for the plants as they can use light only at certain wavelengths. Red algae solve this by developing a different light intercepting pigment (Phycoerythrin). ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 13

Abhipedia IAS WATER AS AN ECLOGICAL FACTOR Who can deny that water is the most important factor influencing the life of all organisms. In fact, life on earth originated in water and is unsustainable without water. Its availability is so limited in deserts that only special adaptations make it possible to live there. The productivity and distribution of plants is also heavily dependent on water. This means that water can be a major limiting factor in terrestrial ecosystems. We know that it is precipitated from atmosphere as rain, snow, sleet, hail or dew and there is a continuous cycling of water through what we know as hydrological cycle which governs water availability over land surfaces. Terrestrial plants mainly absorb water from the soil. Rapid drainage, low rainfall and high evaporation--- ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 14

Abhipedia IAS Or a combination of these factors, can result in dry soils, whereas, the opposite extremes can lead to permanent waterlogging. Like light, it is the quality of water too that has a profound affect on the life of an organism. In short, (chemical composition, pH etc.) of water becomes equally important a factor for an organism s survival. The salt concentration (measures as salinity in parts per thousand), is less than 5 per cent in inland waters, 30-35 per cent the sea and > 100 per cent in some hyper saline lagoons. Some organisms are tolerant to a wide range of salinities and thus are referred to as (euryhaline), while others are restricted to a narrow range of such salinities and hence, are called as (stenohaline). For example, a snail, Hydrobia ulvae can survive a range of salinities from 50-1600 mmolof NaCl ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 15

Abhipedia IAS SOIL AS AN ECOLOGICAL FACTOR The nature and properties of soil in different places vary; it is dependent on the climate, the weathering process, whether soil is transported or sedimentary and how soil development occurred. Various characteristics of the soil such as soil composition, grain size and aggregation determine the percolation and water holding capacity of the soils. These characteristics along with parameters such as pH, mineral composition and topography determine to a large extent the vegetation in any area. This is in turn dictates the type of animals that can be supported. Similarly, in the aquatic environment, the sediment-characteristic often determine the type of benthic animals that can thrive there .

Abhipedia IAS Thank You ABHIMANU IAS : COMPLETE GENERAL STUDIES PRE CUM MAINS COURSE CALL 7347432666, MAIL AT INFO@ ABHIMANU.COM.. 17