Download Answer 2.

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
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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
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Upright
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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:
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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.