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Model Answer M.Sc. (Fourth Semester) Zoology, Paper LZT 401: Animal behaviour and Environmental Biology 1. (i). a (ii). a (iii). b (viii). c (ix).d (x). d (iv). d (v). a (vi). a (vii). b Answer 2. Biological Rhythms: A biological rhythm is any cyclic change in the level of a bodily chemical or function. It includes cyclic pattern of physiological changes or changes in activity in living organisms, most often synchronized with daily, monthly, or annual changes in the environment. Biological rhythms can be internal (endogenous) controlled by the internal biological clock e.g. body temperature cycle; or External (exogenous)- controlled by synchronizing internal cycles with external stimuli, e.g. sleep/wakefulness and day/night. These stimuli are called zeitgebers from the German meaning “time givers”. These stimuli include environmental time cues such as sunlight, food, noise, or social interaction. Zeitgebers help to reset the biological clock to a 24hour day. Circadian Clock: In humans (and other mammals), a circadian clock is located in the suprachiasmatic nuclei (SCN). The SCN is in the hypothalamus. It is a tiny cluster of about 10 thousand nerve cells. The internal mechanism by which such a rhythmic phenomenon occurs and is maintained even in the absence of the apparent environmental stimulus is termed a biological clock. When an animal that functions according to such a clock is rapidly translocated to a geographic point where the environmental cycle is no longer synchronous with the animal's cycle, the clock continues for a time to function synchronously with the original environmental cycle. Circadian rhythm: A rhythm with a 24-hour cycle is called a circadian, solar day and daily rhythm. Circadian rhythms are physiological and behavioral rhythms which include: sleep/wakefulness, body temperature, patterns of hormone secretion, blood pressure, digestive secretions and levels of alertness. Two specific forms of circadian rhythms commonly discussed in research are morning and evening types. There is a direct correlation between the circadian pacemaker and the behavioral trait of morningness - eveningness. People considered morning people rise between 5 a.m. and 7 a.m. go to bed between 9 p.m. and 11 p.m., whereas evening people tend to wake up between 9 a.m. and 11 a.m. and retire between 11 p.m. and 3 a.m. Majority of people falls somewhere between the two types of circadian rhythms. Evidence has shown that morning types have more rigid circadian cycles evening types who display more flexibility in adjusting to new schedules. One theory is that evening types depend less on light cues from the environment to shape their sleep/wake cycle, and therefore exhibit more internal control over their circadian rhythms. Circadian Organization in vertebrates (fish, amphibians, reptiles Non-Mammalian Vertebrates: Non-mammalian and birds) have more complex circadian systems than mammals. While the suprachiasmatic area remains a site of circadian pacemakers, it is, unlike in mammals, not the only such site. The pineal organ, which in mammals is a purely secretory organ, is directly photosensitive in other vertebrates (with the exception of snakes) and is a site of a circadian pacemaker. Retinae of the eyes are also sites of circadian pacemakers in at least some non-mammalian vertebrates. Thus, the non-mammalian circadian system is composed of multiple pacemakers (eyes, pineal, SCN) and multiple photic inputs (eyes, pineal, deep-brain photoreceptors). These structures communicate with each other neurally and humorally and provide a single synchronized output in the rhythmic behavior of the animal. Entrainment: The natural, endogenous period of circadian rhythms, as measured in constant conditions, is almost never exactly 24 hours. In the real world, however, the light-dark cycle provided by the Earth's rotation around its axis is exactly 24 hours long. Utility of biological clocks is in retaining a constant phase between environmental cycles and activities of the organism. Thus, a mechanism must exist to synchronize the internal clock to the environmental cycle, in other words, to force the biological clock to assume a period of exactly 24 hours. The phenomenon of synchronization of biological rhythms by external cues is called entrainment. Freerun: The length of the period of a biological rhythm in the absence of environmental cues. Ultradian rhythms: Ultradian rhythms are defined as an endogenous rhythm pattern that occurs on a shorter time scale than circadian rhythms. As a result of the brief cycle time the frequency of occurrence is much higher. A prime example of an ultradian rhythm is feeding patterns. For the average person this cycle repeats about 3 times a day. Unlike diurnal rhythms ultradian rhythms are share no overlapping relationship with circadian rhythms. Infradian rhythms: Infradian rhythms are defined as an endogenous rhythm pattern that a cycle has duration longer than circadian rhythms, that is more than 24 hours per cycle. Due to the longer time frame for each cycle the frequency of occurrence in these cycles is lower than that of the circadian rhythms. The female menstrual cycle is an example of an infradian rhythm. It is a cyclical biological event that occurs in a fairly regular pattern on a monthly basis. Similar to the ultradian cycle the infradian rhythms are not directly linked to circadian rhythms. Circannual rhythms: It includes bird migrations, reproductive activity, and mammalian hibernation. Daily cycles, or circadian rhythms, are in part a response to daylight or dark, and annual cycles in part responses to changes in the relative length of periods of daylight. There are a number of obvious changes in the environment that occur as a year progresses. It is cold in the winter and hot in the summer. It snows in the winter, and there is a lot of rain during spring and fall. It is easy to find food during the warm season, but very difficult during the winter. It makes sense that organisms would evolve physiological mechanisms that allow them to allocate energy-expensive and risky activities (e.g., reproduction, parenting) to the times of the year when food and cover are abundant, while switching to a more energy-saving mode in the winter. Migrations of birds are conspicuously rhythmic phenomena. As a rule, they occur at certain seasons and certain times of day and thus are manifestations of an approximately annual (circannual) as well as an approximately diurnal (circadian) rhythmicity. Both of these rhythms reflect basic adaptations to environmental cycles and serve as biological clocks to cope with the annual and daily fluctuations in external conditions. The present account summarizes some recent results on the temporal orientation of migratory birds, concentrating on areas in which mechanisms of orientation in time interact with mechanisms of orientation in space. Many bird species, such as warblers, migrate exclusively at night. When kept in cages provided with an appropriate arrangement of perches, the birds’ locomotor activity can be measured by means of microswitches mounted underneath the perches. With this widely used experimental method, it has been shown that locomotor activity in summer and winter is restricted to daytime, i.e. it occurs exclusively in the light portion of the light:dark (L:D) cycle. In autumn and spring, however, the seasons corresponding to natural migratory activity, the birds exhibit additional locomotor activity at night. The rhythm is usually accompanied by variations in migratory fattening (indicated by an increase in body mass) and followed by a moult in winter and a phase of reproductive activity in summer. In the typical case, the period of the rhythm is longer or shorter than 12 months under such constant conditions, attesting to its endogenous circannual nature. Answer 3. Bat Echolocation Echolocation, also called bio sonar, is the biological sonar used by several kinds of animals. Echolocating animals emit calls out to the environment and listen to the echoes of those calls that return from various objects near them. They use these echoes to locate and identify the objects. Echolocation is used for navigation and for foraging (or hunting) in various environments. Some blind humans have learned to find their way using clicks produced by a device or by mouth. Microbats use echolocation to navigate and forage, often in total darkness. They generally emerge from their roosts in caves, attics, or trees at dusk and hunt for insects into the night. Their use of echolocation allows them to occupy a niche where there are often many insects (that come out at night since there are fewer predators then), less competition for food, and fewer species that may prey on the bats themselves. Microbats generate ultrasound via the larynx and emit the sound through the open mouth or, much more rarely, the nose. The latter is most pronounced in the horseshoe bats (Rhinolophus spp.). Microbat About this sound calls (help·info) range in frequency from 14,000 to well over 100,000 Hz, mostly beyond the range of the human ear (typical human hearing range is considered to be from 20 Hz to 20,000 Hz). Bats may estimate the elevation of targets by interpreting the interference patterns caused by the echoes reflecting from the tragus, a flap of skin in the external ear. There are two hypotheses about the evolution of echolocation in bats. This is crucial to a bat's survival, as their main prey are small, quick-moving insects. The task of hunting is made even more difficult for bats because they are only active at night, dusk and dawn. Bats have adapted to this lifestyle to avoid the fierce flying predators that are active in the daytime, and also to take advantage of the abundance of insect species that are active at night. To help them find their prey in the dark, most bat species have developed a remarkable navigation system called echolocation. To understand how echolocation works, imagine an "echo canyon." If you stand on the edge of a canyon and shout "hello," you'll hear your own voice coming back to you an instant later. The process that makes this happen is pretty simple. You produced sound by rushing air from your lungs past your vibrating vocal chords. These vibrations caused fluctuations in the rushing air, which formed a sound wave. A sound wave is just a moving pattern of fluctuations in air pressure. The changing air pressure pushes surrounding air particles out and then pulls them back in. These particles then push and pull the particles next to them, passing on the energy and pattern of the sound. In this way, sound can travel long distances through the air. The pitch and tone of the sound are determined by the frequency of the air-pressure fluctuations, which is determined by the way you move your vocal chords. When you shout, you produce a sound wave that travels across the canyon. The rock face on the opposite side of the canyon deflects the air-pressure energy of the sound wave so that it begins moving in the opposite direction, heading back to you. In an area where atmospheric air pressure and air composition is constant, sound waves always move at the same speed. If you knew the speed of sound in the area, and you had a very precise stopwatch, you could use sound to determine the distance across the canyon. Let's say you're at sea level, and the air is relatively dry. In these conditions, sound waves travel at 741.1 miles per hour (1,193 kph), or 0.2 miles per second (0.32 kps). To figure out the distance across the canyon, you would clock the time between when you first started shouting and when you first heard your echo. Let's say this took exactly 3 seconds. If the sound wave were moving at 0.2 miles per second for 3 seconds, it would have travelled 0.6 miles (0.97 km). This is the distance of the total trip, across the canyon and back. Dividing the total by two, you get 0.3 miles (0.48 km) as the one-way distance. This is the basic principle of echolocation. Bats make sounds the same way we do, by moving air past their vibrating vocal chords. Some bats emit the sounds from their mouth, which they hold open as they fly. Others emit sound through their nose. It's not fully understood how the bat's sound production works, but scientists believe that the strange nose structure found in some bats serves to focus the noise for more accurate pin-pointing of insects and other prey. The bat can also determine where the object is, how big it is and in what direction it is moving. The bat can tell if an insect is to the right or left by comparing when the sound reaches its right ear to when the sound reaches its left ear: If the sound of the echo reaches the right ear before it reaches the left ear, the insect is obviously to the right. The bat's ears have a complex collection of folds that help it determine an insect's vertical position. Echoes coming from below will hit the folds of the outer ear at a different point than sounds coming from above, and so will sound different when they reach the bat's inner ear. A bat can tell how big an insect is based on the intensity of the echo. A smaller object will reflect less of the sound wave, and so will produce a less intense echo. The- bat can sense in which direction the insect is moving based on the pitch of the echo. If the insect is moving away from the bat, the returning echo will have a lower pitch than the original sound, while the echo from an insect moving toward the bat will have a higher pitch. Territoriality: It is a type of intraspecific or interespecific competition that results from the behavioral exclusion of others from a specific space that is defended as territory. This well-defined behavior is exhibited through songs and calls, intimidation behavior (to frighten), attack and chase, and marking with scents. This form of defense proves to be very costly for animals. So one is forced to ask, why do animals take part in such interspecific competition? In order to understand this question one must take a cost-benefit approach to territoriality. The proximate reasons for such defense vary. For some animals the reason for participating in such elaborate protective behavior is to acquire and protect food sources, nesting sites, mating areas, or to simply attract a mate. The ultimate cause of this behaviour may be attributed to the increased probability of survival and reproductive successes. In defending a territory an animal is ultimately securing that it will have a habitat in which to forage for food and to successfully reproduce, thus increasing the animal's overall fitness. This ultimate theory is strengthened when one considers the instances in which territoriality increases; in times of depleted resources the presence of territoriality increases. The presence of territoriality often forces less fit animals to live in sub optimal habitats, thus reducing their reproductive success. Though territoriality offers immense reproductive and nutritional benefits, it also comes at a cost. Defending territory is not easy. Territoriality cost time and energy and can often interfere with other fundamental activities as parenting, feeding, courting, and mating. For these reasons territoriality may not be seen as a benefit in all animals. Animals must be able to reap the fruits of territoriality, while expending the least amount of energy. For these reasons if resources are abundant and predictable it would be disadvantageous to defend the territory. On the other hand, if resources are scarce and undependable it would be advantageous to exhibit territoriality. An animal chooses its territory by deciding what part of its home range it would like to defend. In selecting a territory the size and the quality play a crucial role in determining an animal’s habitat. Territory size generally tends to be no larger than the organism than requires to survive, because with an increase in territory comes an increased in energy expenditure. For some animals the territory size is not the most important aspect of territoriality, but rather the quality of defended territory. The quality is considered to be fundamentally important due to amount of food availability and superior nesting sights. Animals depend on these features to ensure their superior fitness. Animals invest a lot of time and energy in defending their territories, and for this reason they fight vigorously to defend their territory at all cost. Researchers suggest for this reason that when a rival challenges a territory holder, the owner almost always wins the contest. This phenomenon could be attributed to an evolutionary stable strategy which assets that rules for behavior is controlled by an inherited proximate mechanism such that the differences between individuals in their strategies are liked to differences in their genes. Territory plays an important role as a mechanism of population regulation, insuring the success of fit animals, and aiding in the eradication of less fit animals. Territorially also plays a fundamental role as an indicator of carrying capacity; it also serves as an indicator of how much habitat is necessary to support viable populations. Defending a territory: Some animals defend their territory by fighting with those who try to invade it. Fighting, however, is not often the best option, since it uses up a large amount of energy, and can result in injury or even death. Most animals rely on various threats, either through vocalizations, smells, or visual displays. The songs of birds, the drumming of woodpeckers and the loud calls of monkeys are all warnings that carry for long distances, advertising to potential intruders that someone else's territory is being approached. Many animals rely on smells to mark their territories, spraying urine, leaving droppings or rubbing scent glands around the territories' borders. Approaching animals will be warned off the territory without ever encountering the territory's defender. On occasion, these warnings may be ignored, and an intruder may stray into a neighboring territory, or two animals may meet near the border of their adjacent territories. When two individuals of a territorial species meet, they will generally threaten each other with visual displays. These displays often will exaggerate an animal's size by the fluffing up of feathers or fur, or will show off the animal’s weapons. The animals may go through all the motions of fighting without ever actually touching each other, a behavior known as ritual fighting. The displays are generally performed best near the center of an animal's territory, where it is more likely to attack an intruder, and become more fragmented closer to the edges, where retreating becomes more of an option. This spectrum of performances results in territorial boundaries, where displays of neighbors are about equal in intensity, or where the tendency to attack and the tendency to retreat are balanced. Actual fighting usually happens in overcrowded conditions, when resources are scarce. Serious injury can result, and old or sick animals may die, leading to a more balanced population size. Under most natural conditions, territoriality is an effective way of maintaining a healthy population. The study of social behaviors such as territoriality in animals may help us also to understand human society, and to learn how individual behavior affects human populations. Answer 4. Behaviour: Behaviour includes all those processes by which an animal senses the external world and the internal state of its body and responds accordingly. Many such processes will take place inside the nervous system and not be directly observable. Behaviour continues as long as life persists; anything and everything may count. There are different kinds of animal behaviour developed in animals which is given as follows: Innate Behaviour: Whatever our level of study, the adaptiveness of behaviour is one of the most dominant features that we observe. Of course animals do make mistakes and may appear clumsy at times, particularly when they put into unnatural situation, but for the most part their behaviour is beautifully matched to their way of life. They respond appropriately to the features of their world and thereby feed themselves, find shelter, mate and produce offspring. How can behaviour acquire this near perfect match to an animal’s mode of life? This question has fascinated people for centuries, because we have always been observers of animals. During seventeenth century, Rene Descartes a French philosopher and mathematician supposed that animals were able to respond adaptively because they operated using instincts endowed by the Creator, which automatically provided them with the correct response, requiring neither experience nor thought. The concept of instinct or instinctive behaviour (the terms ‘innate behaviour’ or ‘inborn behaviour’ are effectively synonymous) is still a familiar one. Instinct is often described as patterns of inherited, preset behavioural responses which develop along with the developing nervous system and can evolve gradually over the generations, just like morphology, to match an animal’s behaviour to its environment. It might be defined in a negative kind of way, as that behaviour which does not require learning or practice. However, they can learn how to behave appropriately and perhaps practice or even copy from others to produce the best response. Learning Habituation: It is an extremely simple form of learning, in which an animal, after a period of exposure to a stimulus, stops responding. The most interesting thing about habituation is that it can occur at different levels in the nervous system. Sensory systems may stop, after a while, sending signals to the brain in response to a continuously present or often-repeated stimulus. Lack of continued response to strong odors is a common example of sensory habitation. Habituation is important in filtering the large amounts of information received from the surrounding environment. By habituating to less important signals, an animal can focus its attention on the most important features of its environment. A good example of this is species that rely on alarm calls to convey information about predators. In this case animals stop giving alarm calls when they become familiar with other species in their environment that turn out not to be predators. Habituation is an important component of "not crying wolf" when nonthreatening animals come close. Birds learn not to waste energy by taking flight at the sight of every leaf blowing in the wind. Squirrels learn not to respond to the alarm calls of other animals if these calls are not followed by an actual attack. This may also help us understand why animals avoid predators, while ignoring common, harmless species. Conditioning: It is the term used to designate the types of human behavioral learning. Since the 1920s, conditioning has been the primary focus of behavior research in humans as well as animals. There are four main types of conditioning: Classical Conditioning, Operant Conditioning, Multiple-Response Learning, and Insight Learning. Operant conditioning is goal-directed behavior. We learn to perform a particular response as a result of what we know will happen after we respond. For example, a child may learn to beg for sweets if the begging is usually successful. There is no single stimulus that elicits the begging behavior, but instead it occurs because the child knows that this action may result in receiving treats. Every time the child receives sweets after begging, the behavior is reinforced and the tendency of the child to beg will increase. At first the rat would not show any signs of associating the two events, but over time its exploring behavior becomes less random as it begins to press the lever more often. The food pellet reinforced the rat's response of pressing the lever, so eventually the rat would spend most of its time just sitting and pressing the lever. This type of learning is based on the idea that if a behavior is rewarded, the behavior will occur more frequently. Reasoning: Reasoning is the generation or evaluation of claims in relation to their supporting arguments and evidence. The ability to reason has a fundamental impact on one's ability to learn from new information and experiences because reasoning skills determine how people understand, evaluate, and accept claims and arguments. Reasoning skills are also crucial for being able to generate and maintain viewpoints or beliefs that are logical with, and justified by, relevant knowledge. There are two general kinds of reasoning that involve claims and evidence: formal and informal. Formal reasoning is used to evaluate the form of an argument, and to examine the logical relationships between conclusions and their supporting assertions. Arguments are determined to be either valid or invalid based solely on whether their conclusions necessarily follow from their clearly stated assertions. An example of a logically valid syllogism (a process of logic / logical statement) is: All dogs are animals; all poodles (dogs with curly hair that is usually cut short, except on its head, tail and legs) are dogs; therefore poodles are animals. A slight change to one of the premises will create the invalid syllogism: All dogs are animals; some dogs are poodles; therefore all poodles are animals. Informal reasoning refers to attempts to determine what information is relevant to a question, what conclusions are reasonable, and what degree of support the relevant information provides for these various conclusions. It includes making predictions of future events or trying to explain past events. These cognitive processes are involved in answering questions as ordinary as "Did human beings evolve from simple one-celled organisms?" Informal reasoning has a pervasive influence on both the everyday and the monumental decisions that people make, and on the ideas that people come to accept or reject. In recent decades it has become apparent that the cognitive skills of many animals are greater than previously suspected. Part of the problem in research on cognition in animals has been the intrinsic difficulty in communicating with or testing animals, a difficulty that makes the outcome of a cognitive experiment heavily dependent on the cleverness of the experimental approach. Another problem is that when investigating the non-human primates, the animals whose cognitive skills are closest to that of humans, one cannot do experiments on large populations because such populations either do not exist or are prohibitively expensive to maintain. The result is that in the area of primate cognitive research reported experiments are often "anecdotal", i.e., experiments involving only a few or even a single animal. Answer 5. Ecosystem is the minimal entity that has the properties required to sustain life. An ecosystem is a community of organisms and its non-living environment in which matter (chemical elements) cycles and energy flows. Components of Ecosystem A. Biotic Components (Living Components) The biotic or living components of the ecosystem comprise the kinds, numbers and distribution of living organism. All organisms require energy for their life processes and materials for their formation and maintenance of body structures. Food supplies both energy and materials for sustenance of life. Green plants produce carbohydrate by photosynthesis and also synthesize fats and proteins. a. Producers The communities of green plants-which absorb carbon-dioxide, mineral nutrients, water and built up organic matter with the help of a solar energy, are called producers. Producers release oxygen and thus life activity in the system will collapse in the absence of producers. They are also called as autotrophic organisms. b. Consumers All animals that do not make their own food but depend on other organisms to obtain their energy for survival are called heterotrophs or consumers. Among consumers some animals such as goat, cow, deer, rabbit and insects which eat green plants are called primary consumers or herbivores. Organisms which eat herbivores like a frog that eat grasshoppers are called secondary consumers. Organisms which eat these secondary consumers are called tertiary consumers. The primary consumers are herbivores but the secondary and tertiary consumers are called carnivores. Consumers may be classified into two classes which are summarized as: (i) Macro-consumers: Macro-consumers include herbivores, carnivores and omnivores. The herbivores are also known as primary consumers, carnivores as secondary consumers and omnivores as tertiary consumers. (ii) Micro-consumers: Organic materials are added to the environment with the death of plants and animals and also due to deposition of animal's waste products. Such organic materials are decomposed by micro-organisms, i.e. known as decomposers. c. Decomposers Faecal matter, exudates and excreta of plants, animals and their dead bodies are decomposed by the activity of bacteria, fungi and other small organisms which live on dead and decaying organic matter. They constitute the community of decomposers which bring the constituent elements of the plants and animals bodies back to the surrounding medium or to the soil. B. Abiotic Components All the abiotic factors or non-living factors are not known as yet and the implications of many have not been understood adequately. Abiotic components of the ecosystem are of three types: (i) Climatic System: Climatic conduction as well as physical factors of the given region e.g. air, water, soil, temperature, light, moisture, rainfall etc. (ii) Inorganic substances: Inorganic substances e.g. carbon, nitrogen, sulphur, phosphorus, hydrogen etc all of which are involved in geochemical cycle. (iii) Organic Substances: The major organic substances e.g. proteins, carbohydrates, lipids, humic substances which are present either in the environment or in biomass. The biochemical structure links the biotic and abiotic compounds of the ecosystem. Answer 6. Mutualism vs Commensalism • • Mutualism: In mutualistic interactions, both species benefit from the interaction. A classic example of mutualism is the relationship between insects that pollinate plants and the plants that provide those insects with nectar or pollen. Another classic example is the behavior of mutualistic bacteria in ecology and human health. Gut bacteria in particular are very important for digestion in humans and other species. In humans, gut bacteria assist in breaking down additional carbohydrates, out-competing harmful bacteria, and producing hormones to direct fat storage. Humans lacking healthy mutualistic gut flora can suffer a variety of diseases, such as irritable bowel syndrome . Some ruminant animals, like cows or deer, rely on special mutualistic bacteria to help them break down the tough cellulose in the plants they eat. In return, the bacteria get a steady supply of food . Commensalism: In commensalism, one organism benefits while the other organism neither benefits nor suffers from the interaction. For example, a spider may build a web on a plant and benefit substantially, while the plant remains unaffected. Similarly, a clown fish might live inside a sea anemone and receive protection from predators, while the anemone neither benefits nor suffers. Competition It is an antagonistic interaction in which two or more members of same species (intraspecific), or two or more members of different species (interspecific) of same trophic level compete for common resource like light, moisture, space, nutrients etc. which are in short supply in relation to the member of individuals. On the basis of nature of struggle, competition is of two types. a) Direct interference type Where members of two different populations are mutually and actively inhibitory to each other. In such a case competition benefits the organism, which is more suitably adapted while the other is at a disadvantage. The size of population of the latter decreases, finally leading to its elimination. Example: Crombie conducted experiments on two beetle populations. Tribolium confusum and Oryzaephilus surinamensis, in a wheat flour medium. After sometime it was observed that O.surinarnensis population died out. b) Competition resource use type In this each population inhibits the other indirectly for the resource in short supply. Example: Trees, shrubs and herbs in a forest, struggle for sunlight, water and nutrients. Similarly, grasshoppers, rats, rabbits, deer (herbivores) compete for food especially during draught and less food availability. On the basis of interacting species competition may be divided in to: 1. Interspecifis: between two species 2. Intraspecific: between individuals of the same species. Predation It is a negative, direct food related interspecific interaction between two species of animals in which larger species called predator attacks, kills and feeds on the smaller species called prey. Predator population adversely affect the growth and survival of smaller prey population and therefore predation is considered an antagonistic interaction. Examples: i) There are certain carnivorous plants also referred, as insectivorous plants that act as predators in nature. Plant like Nepenthes (pitcher plant), Drosera (sundew), Dionoeae (Venus fly trap) etc. feed on insects to fulfil their nitrogen requirement. ii) All carnivorous animals and scavengers are predators. Some predators (such as frog) act as prey for others (snake) which inturn are prey to a higher carnivores (eagle). iii) Herbivorous animals, eating plants or seeds, are also predators as they feed on individuals or future individuals. Parasitism: This is a symbiotic relationship between two organisms in which one species (parasite) benefits for growth and reproduction to the harm of the other species (host). It must be emphasized that parasite and host interact and that excessive harm done to a host, which makes it less competitive, also endangers the survival of the parasite species. The bilharzia parasite, Schistosoma haematobium, a parasitc flatworm, is a good example of a successful parasite. It completes its life cycle in two hosts. The male and female adults live in the blood of humans while larval forms live in the bodies of a type of snail, Bulinus africanus. The adults posses suckers with which they attach themselves to the walls of blood vessels. Their bodies are covered with thick cuticles. When mature, adults meet in the blood of man. The male and female become 'associated' in that the slightely broader male rolls its body into a tube in which the long, thin female lives. When the female is ready to lay eggs she frees herself and moves into small blood vesels in the wall of the bladder. There she lay eggs. When the egg comes into contact with the water, its shell breaks and a ciliated larva, called a miracidium, is released. If it comes in contact with a host it works itself into the body of the snail by means of hydrolysis. Sporocysts are produced by the miracidium. Cercariae are produced after several generations of sporocysts. The cercariae make their way into the water and make contact with a human. Their it comes into the blood stream and live their. Within six to twelve weeks the larvae develop into adults and the cycle is reported once more. Ammensalism It is an antagonistic interspecific interaction in which one species is inhibited while other species is neither benefitted nor harmed. In simple words, in ammensalism, one organism does not allow other organism to grow or live near it. It is also called antibiosis and the affected species is called ammensal and the affecting • species is called inhibitor. Such inhibition is achieved through the secretion of certain chemicals called allochemics or allelopathic substances. Examples: Most common phenomenon of antibiosis is formation of antibiotics that are antagonistic to the microbes. 1) Penicillium notatum releases the antibiotic substance Penicillin, which inhibits the growth of variety of bacteria. 2) Streptomyces griseus produce antibiotic Streptomycin, which again inhibits the growth of many bacteria. 3) Roots of certain plants produce allochemic substances which check the growth of other plants to conserve resources, such as, Convolvulus arvensis, a weed inhibits the germination and growth of wheat. Answer 7. Charles Elton developed the concept of ecological pyramid. After his name these pyramids are also called as Eltonian pyramids. It is a graphical representation or pyramid shaped diagram which depicts the number of organisms, biomass and productivity at each trophic level. Ecological pyramids begin with the producers at the bottom and proceed through the different trophic level. There are three types of ecological pyramids as follows: 1. Pyramid of number 2. Pyramid of biomass 3. Pyramid of energy 1. Pyramid of number: When plotted the relationships among the number of producers, primary consumers (herbivores), secondary consumers (carnivore of order 1), tertiary consumers (carnivore of order 2) and so on in any ecosystem, it forms a pyramidal structure called the pyramid of number. The shape of this pyramid varies from ecosystem to ecosystem. There are three types of pyramid of numbers · Upright · Partly upright · Inverted Upright Pyramid of Number In aquatic and grassland ecosystem numerous small autotrophs support lesser herbivores which support further smaller number of carnivores and hence the pyramidal structure is upright. Partly upright pyramid of Number In forest ecosystem lesser number of producers support greater number of herbivores who in turn support a fewer number of carnivores. Inverted Pyramid of Number In parasitic food chain one primary producer support numerous parasites which support still more hyperparasites. 2. Pyramid of Biomass: When we plot the biomass (net dry weight) of producers, herbivores, carnivores and so on we have a pyramid of biomass. Two types of pyramid of biomass are found · Upright · Inverted Upright Pyramid of Biomass: When larger weight of producers support a smaller weight of consumers an upright pyramid results. eg forest ecosystem Inverted Pyramid of Biomass: When smaller weight of producers supports larger weight of consumers an inverted pyramid of biomass is formed eg aquatic ecosystem 3. Pyramid of Energy: The pyramid of energy is drawn after taking into consideration the total quantity of energy utilized by the trophic levels in an ecosystem over a period of time. As the quantity of energy available for utilization in successive trophic levels is always less because there is loss of energy in each transfer, the energy pyramid will always be upright. Answer 8. Solid Waste Pollution Solid wastes are generally composed of non-biodegradable and non-compostable biodegradable materials. The latter refer to solid wastes whose biodeterioration is not complete; in the sense that the enzymes of microbial communities that feed on its residues cannot cause its disappearance or conversion into another compound. Parts of liquid waste materials are also considered as solid wastes, where the dredging of liquid wastes will leave solid sedimentation, to which proper waste management techniques should also be applied. Sources: • • • • Households Businesses and Commercial establishments Manufacturers or Industrial sites Biomedical sources like hospital and clinics. They are the trash collected by the municipal waste management units for segregation according to the process of disposal. Effects of Solid Waste Water Pollution: Randomly pile up these solid wastes which yet to be decontaminated and slits up for a long time, narrowing water area; the micro toxic element in these substances such as mercury, cadmium and lead will intrude into soil along with drain which next pollutes underground water and might penetrate to water network accompanying with rains, even flows into well, river and nearby sea area; besides, it is also taken by plant, next enter into human body through the food chain to damage human health. Atmospheric Pollution: The solid waste will generated a great deal of toxic gas and dust through the burning process; other kinds of organic solid wastes will be decomposed by microorganism under appropriate temperature and moisture after long time of pile-up and also release toxic gas. Soil Pollution: The toxic liquids from untreated hazardous solid wastes will penetrate into soil through weathering action, raining action, ground runoff action, further kill microorganism living in the soil and damage biological balance.