Biology (Ecology)

GREASE THOSE WHEELS ( BIOLOGY )

#2 ECOLOGY

• define the terms habitat, niche, population, community and ecosystem and state examples of each;
• explain the terms producer, consumer and trophic level in the context of food chains and food webs;
• explain how energy losses occur along food chains and discuss the efficiency of energy transfer between trophic levels;
• describe how nitrogen is cycled within an ecosystem, including the roles of microorganisms;

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Many students often describe ecology as the most easiest part of any biology course and I agree with them because ecology is nothing more than memorizing key definitions and remembering them at the time of need with a few exceptions like nitrogen and carbon cycles...

and so we will get over with this in the same method...

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Lets start with all the important definations that you should know...

• Ecology is the study of living organisms and their relationship with all the other biotic (living) and abiotic (non-living) components of their environment.
• Environment are the external conditions, resources and stimuli with which organisms interact which in turn affects their survival, life and growth.
• Species are a group of organisms that are reproductively isolated, inter-breed within themselves to produce fertile offsprings and have structural similarities between them that results in them being told apart from other species.
• Habitat is a Latin word for it inhabits and is defined as an ecological area that is inhabited by a population or an organism which is characterized by its dominant producer or physical features. For example, grasslands, alps etc.
• Population is the collective name given to all the organisms of a particular species within a particular area at a given time. They share the same gene pool and are usually isolated from other populations of the same species. For examples the Tigers of central Bengal are a population.
• A niche is a functional role of a specie or population within an ecosystem, i.e, its way of interacting with other biotic and abiotic factors of its environment. For example, a shoal of fishes are a niche in an aquatic habitat, because they interact with other factors and play their part in the ecosystem like providing food to the sharks (prey), feeding over plankton (eating), reproducing within themselves to increase the size of the population etc.
• Community is basically an expanded defination of population as it is the collective name given to all populations of different species that inhabit a particular area at a given time. For example camels, foxes, scorpions etc living in the Sahara are a community.
• Ecosystem is defined as a unit in which all biotic and abiotic factors interact with each other during their normal function and is characterized by an energy flow through the chain of organisms. Examples can be, an ocean, a rain-forest or even a decomposing log!
• Producers are the auto-trophic organisms, like plants, who initiate a food chain because of their ability to produce energy rich organic compound from simple inorganic compounds, like water and carbon dioxide, and energy from sunlight.
• Consumers are hetero-trophic organisms that obtain their food form other organisms by eating or decomposing them.
• Decomposers are sapro-trophic organisms that feed on dead and decaying organisms and organic waste. They play an important part in nutrient recycling.
• Trophic Level is the position on which an organism feeds in a food chain. It can be trophic level 1 for producers, 2 for herbivores, upto 5 for predators and no place for decomposer.

Thats it for the definitions part...now lets move on to the other components...

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The concept of energy losses should be mastered before sitting for your AS Level examination as it is one of the most frequently  tested concepts.

Food chains cannot be simply put as transfer of food from one living thing to another, for example not all the energy a hen produces is transfered to your chicken roast!!, it involves energy losses as some energy is utilized by the organism for...

• Respiration (energy expended by consumers is larger than the producers due to their increased activity)
• Excretion (exhalation and excretion)
• Death and decaying of the organism.
• Heat Energy due to activity.

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Nitrogen Cycle is an important part of the ecosystem because nitrogenous compounds help the growth and survival of almost all living organisms, as nitrogen is a component of almost all amino acids and subsequently all proteins, RNA and the most important of all the DNA. But the problem is that atmospheric nitrogen (N2) is  not usable by living organisms for the above listed functions so nitrogen fixation is as important a process as nitrogen itself. Lets look into this crucial-for-life cycle and its processes.

• Nitrogen-fixing bacteria forming symbiosis (an ecological partnership) with a legume plant. It resides in the root modules of the plant and gets food and shelter from the plant while rhizobium (a type of nitrogen-fixing bacteria) provides th plant with organic nitrogen compounds such as glutamines (first of all it converts atm. nitrogen to ammonia).
• Another type of Nitrogen fixation occurs in the soil where bacterias like azotobacter convert atmospheric nitrogen to more reactive forms of nitrogen. Nitrogen fixation also occurs in some other ways..
• Via the Haber Process, when ammonia is made from hydrogen and nitrogen under high temperature and pressure. The subsequent use and manufacture of fertilizers and other chemicals helps in nitrogen fixation.
• Lightning is another source of fixed nitrogen.
• Oxides of nitrogen releases by internal combustion engines.
• Ammonification is basically the conversion of nitrogenous wastes or dead animals or plants back into ammonium ions. It is done by both aerobic or anaerobic bacteria and in some cases fungi.
• Nitrification is the conversion of ammonium ions into nitrates and nitrites; usually in two steps...
• Nitrosomonas convert ammonium ions to nitrites (NO2-). As accumulation of nitrites is toxic for plants so it must be quickly converted to nitrates.
• Nitrobacter converts nitrites in to highly soluble nitrates (NO3-).
• Bacteria species like Clostridium convert nitrates back to inert atmospheric nitrogen, in a process called Denitrification, thus completing the nitrogen cycle. They do this by using nitrates as the electron acceptor in place of oxygen in their respiration cycle.

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Thats all! Hoping that it was of some use to you!!