•  Pheromones are chemical messengers secreted or discharged outside the body of the organism that activates a social response in members of the same species.
• The term “Pheromone” (Phero-to carry and hormone-to stimulate) was coined by Peter Karlson and Martin Lüscher in 1959.
• They are ectohormones in nature.
• Both plants and animals can release pheromones
• First sex pheromone was identified in 1959 from silk moth (Bombyx mori) termed as bombykol.
• Plants use pheromones to attract bees and other pollinators to their flowers.
• Some plant pheromones have alike chemistry to animal pheromones.
• Aphrodisiacs are fungi that has an odour nearly alike to androstenol; a sex attractant for pigs and very similar to chemicals that act as sex attractants in humans.
•  Both intraspecific and interspecific signals influence many forms of insect behaviour.
•  Chemicals engaged in signalling between organisms and affecting behaviour alteration are called semiochemicals.

These are of 2 major types of pheromones:

1)Pheromones – conciliate intraspecific interactions.

2)Allelochemicals – conciliate interspecific interactions.

Evolution of pheromone

•  Chemical senses being primitive, are shared by all organisms including bacteria, so animals are pre-adapted to determine chemical signals in the environment.
•  Pheromones originate from compounds that originally having other uses or importance.
•   Chemical molecules became signal molecules by increasing sensitivity and specificity.
•   Signals are acquired from movements, body parts or molecules already in use and are eventually changed in the course of evolution to intensify their signal
  function.
•   Evolution in the senses and response of the receiver which facilitated pheromones to become the mostly acceptable way of communication among animals.

Types of pheromones

1. Aggregation pheromones:

•  A group of individuals existing at one location is termed as aggregation.
• Released by male and utilized by species with long-lived adults.
•   These pheromones function in many ways including mate selection, protection against predators, and conquering host resistance by mass attack.
•  Ex: boll weevil (Anthonomus grandis B.) is a oligophagous insect which feeds primarily on cotton, Gossypium hirsutum L. Male boll weevils locate their host plant, feeding ensues and releases aggregation pheromones, grandlure.
•  Male or grandlure baited traps have been used for mass trapping the boll weevil for many years. It is the most ecologically selective pest suppression methods as they are nontoxic and effective at very low concentrations.

           2) Alarm pheromones:

• Some species are capable of releasing a volatile substance in response to attack of the predator which alerts/triggers other members of same species of the danger.
• Ex: Aphides belonging to Homoptera species secrete (E)- β – farnesene as alarm pheromone. These chemicals are released in air as envoy to help other to escape from danger.
• Certain plants emit alarm pheromones when grazed upon, resulting in tannin production in neighbouring plants. These tannins make the plants less beguiling for the herbivore.

           3) Releaser pheromones:

•  Releaser pheromone has an immediate impact on the behaviour of the recipient and alters it.
•  This type of pheromone shows a swift response, but is degraded in no time.
•   Ex: Some organisms use strong attractant molecules to lure mates from a distance of two miles or more.

4) Signal pheromones:

•  Signal pheromones results short-term changes, such as the neurotransmitter release that activates a response.
• For example, GnRH molecule act as a neurotransmitters in rats to gain lordosis behaviour (inward curve of the spine).

            5) Primer pheromones:

• Triggers a chain of physiological development events that may take days to weeks before an unconcealed response is noticed.
• For example- primer pheromones include stimulation of sperm production in fish, termites cast determination, development rates of locust, menstrual cycles in human and other mammals.

6) Epideictic pheromones (Ovipositor pheromones):

•   Also termed as spacing pheromones.
•  They are known to repel, rather than attract.
•  Capable of regulating population density.
•   For examples- in insects, female who lay their eggs in fruits deposit these unknown substance in the territory of the clutch to signal to other females of the same species they should clutch elsewhere.

7) Territorial pheromones:

•  These pheromones explains claimed region of specific organism.
• alert other organisms of nearby dominant animals.
• These are helpful to filter other animals, such as an ant from another colony.
•  Ex: Dogs deposit territorial pheromones present in their urine on landmarks to mark the boundaries their area.

8) Trail pheromones:

•   Recruited by social insects for direction and to employ nest mates to a suitable food source.
•  These are mostly vaporous compounds.
• Ex: When species of wasps such as Polybia sericea found new nests, they use pheromones to lead the rest of the colony to the new nesting site.

9) Sex pheromones:

•   Particularly related with signalling mating behaviours or dominance.
• These are excreted by an organism to lure an individual of the opposite sex and inspire them to mate with them.
•  Generally released by females.
• These are simple and volatile, long chain unsaturated alcohol, acids, benzene derivatives, or bicyclic aliphatic compounds.
•   Ex: The female Bombyx mori (silk moth) secretes bombykol, the first sex attractant isolated from natural source. It is released in air to attract the male from distance. The male organ of B.mori is intensely sensitive of bombykol.

Application of Pheromones in Pest management

• Inspecting a population of insects to determine if they are present or absent in an area.
• To detect if enough insects are present to permit a costly treatment.
• To mass trap insects to eliminate large numbers of insects from the feeding and breeding population.
• Example: Relatives of bark beetles called ambrosia beetles have been mass trapped from log sorting and timber processing areas throughout British Columbia. Disruption of mating in populations of insects. Useful in protecting crops and residents. Synthetic pheromone is dispersed into crops and the false odour plumes attract males away from females that are waiting to mate.
• Push-pull, attract and kill are direct plans for pest killing.
• Mating disturbance by creating hindrances can control pests as well.
• The theory of behavioural manipulation can be applicable to lure the natural enemies of pests  and  increase  biological  control  services in  managed agroecosystems.

References:

• https://www.researchgate.net/publication/267512282_Use_of_Pheromones_in_Insect_Pest_Management_with_Special_Attention_to_Weevil_Pheromones
• https://www.grains.k-state.edu/spirel/docs/research/domestic-presentation/heat-workshop-1/12_Jeff%20Weier.pdf

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• Biodiversity is defined as the variations among living organisms from all possible sources. It includes the variability within or between the species and within or between ecosystems.
• According to the definition of the 1992 UN conference on Environment and Development (UNCED) Convention, biodiversity includes all of its manifestations. Therefore, along with terrestrial biodiversity, it also covers marine as well as other aquatic biodiversity. As such biodiversity means the richness and variety of living things in the world as a whole or in any location within it.

What are the elements of biodiversity?

• Major elements of biodiversity comprise of- Ecosystem diversity, Species diversity, and Genetic diversity.
  

  1. Ecosystem diversity

• An ecosystem is made of a dynamic system of plant, animal, and microorganism groups and their non-living environment altogether interact as functional unit.
• Non-living components cover sunlight, air, water, minerals and nutrients.
• Ecosystem can be small and short-lived, for example, water filled tree holes or rotting logs on a forest floor or large and long-lived like forests or lakes. Thus, ecosystem commonly exist within ecosystems.
• Ecosystem diversity refers to the variation and rate of occurrence of distinct ecosystems including the variety of habitats, biotic communities and their change in structure and composition over time and ecological processes in the biosphere.
  

  2. Species diversity

• Species is defined as a population of organisms whose members are able to interbreed freely under natural conditions.
• A species represents a group of organisms which has evolved definite inheritable features and occupies a unique geographical area.
• Species usually do not freely interbreed with other species (Wilson,1992).
• Species diversity is used to describe the frequency and variety of species (wild or domesticated) within a geographical area.
• The total number of species in the globe has been estimated to range from 5-30 million (Wilson,1988), out of which approximately 1.7 million living species of all kinds of organisms have been described to date (WCMC,1992).
• The World Conservation and Monitoring Center suggests that there are many different ways to describe species diversity:
  • Species richness is the total number of species within a geographical area.
  • It is expressed as an enumeration of the species occurring within a particular sample area, and is one often used to measure species diversity.
  • Measures of species richness are the basis for the observation that diversity increases with decreasing latitude on Earth, for example, tropical areas are richer in species than temperate areas.
  • Species evenness is also used to measure species diversity which is expressed as relationship of species to each other.
  • This includes relative abundance of species in different categories.
  • It is also known as taxonomic diversity. For example, an island with two species of birds and one species of lizard has greater taxonomic diversity than an island with three species of birds but no lizards (Raven,1992).
  • Species dominance is expressed as the most abundant species as dominant (Botkin and keller,1995).

3. Genetic diversity

• Genes are the principal units of heredity which are passed from an organism to its offspring.
• These are composed of nucleic acids and are located along an organism’s chromosomes, in the plasmids of bacteria and other extra-chromosomal forms as well.
• Genes, either individually or in groups contribute different credits to an organism such as its physical appearance (black eyes or dark hair), its ability to resist certain pests, or survive drought
• Genetic diversity refers to contrast of genes and/or genomes within living organisms, that is, the genetic differences among populations of a single species and among individuals within a population.
• In other word this covers distinct populations of the same species such as hundreds of traditional rice varieties in Nepal.
• According to Raven (1992), it is also expressed as genetic variation within a population, such as genetic variation is very high among Indian rhinos, and very low among Cheetahs.
• Nature’s wild species contain valuable genetic information.
• If a species is to survive, it needs some genetic diversity. But an inbred population loses diversity, and becomes vulnerable to pests and infectious diseases which may endanger the whole population.
• Using ‘DNA fingerprinting’, molecular biologists can detect inbred population which may be moving forward for extinction.
• In the agriculture industry, monoculture crops, artificial insemination and embryo cloning technique lead to narrow, inbred population. In biomedicine too, genes from such species as fungi, lichens, marine organisms and higher plants have been used to produce antibiotics, anti-cancer agents, hormones, muscles relaxants, cardiac and respiratory stimulants.
• Modern biotechnology is generating recombinant DNA vaccines and pharmaceuticals, gene probes for inherited disease and forensic analysis, and genetically engineered organisms for mining, energy, chemical production and treatment of waste products.
• Therefore, genetic heritage of the earth once preserved can be read, appreciated and perhaps even reactivated by future generations.
  

  References:

• Chaudhary Ram P., M.Sc., Ph.D., D.Sc., F.N.R.S., Professor of Botany, TU, Kirtipur, Ktm, Nepal, Biodiversity in Nepal,1998.
• www.biologicaldiversity/org
• www.yourarticlelibrary.com

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• Cryopreservation is a process of preserving or storing cells, tissues, organs or any other biological materials from any potential damage by maintaining the materials at very low temperature (typically -80 °C using solid CO2 or −196 °C using liquid Nitrogen.
• In cryopreservation, very low temperatures is used to preserve living cells and tissues and maintain their viability. Unprotected freezing is normally lethal.
• Cryopreservation is based on the conversion of water present in the cells from a liquid to a solid state.
• When cooling below 0°C, the biological effects are dominated by the freezing of water, which typically constitutes at least 80% of the tissue mass.
• The cell water requires much lower temperature to freeze (even up to -68°C) due to the presence of salts and organic molecules in the cells, in comparison to the freezing point of pure water (around 0°C).
• The metabolic processes and biological divisions in the cells/tissues are almost stopped when stored at low temperature.

Process of Cryopreservation:

• The cryopreservation of plant cell culture followed by the regeneration of plants involves the following steps:
  • 1. Development of sterile tissue cultures
  • 2. Addition of cryoprotectants and pre-treatment
  • 3. Freezing
  • 4. Storage
  • 5. Thawing
  • 6. Re-culture
  • 7. Measurement of viability
  • 8. Plant regeneration

The features of the above steps are described as follows:

step I: Development of sterile tissue culture:

• One of the important steps is the selection of plant species with reference to morphological and physiological characters .
• It directly influence the ability of explant to survive cryopreservation.
• Any tissue from a plant can be employed for cryopreservation e.g. meristems, endosperms, embryos, ovules, seeds, cultured plant cells, calluses, protoplasts.
• Out of these, meristematic cells and suspension cell cultures which are in the late lag phase or log phase are most appropriate.

step II: Addition of cryoprotectants and pre-treatment:

• The compounds that can prevent the damage caused to cells by freezing or thawing are called as cryoprotectants.
• Cryoprotectants reduce the freezing point and super-cooling point of water.
• As a result, the ice crystal formation is delayed during the process of cryopreservation.
• Cryoprotectants used are dimethyl sulfoxide (DMSO), glycerol, ethylene, propylene, sucrose, mannose, glucose, proline and acetamide.
• Among them, DMSO, sucrose and glycerol are most commonly used.
• Generally, a mixture of cryoprotectants instead of a single one is preferred for more effective cryopreservation without damage to cells/tissues.

step III: Freezing:

• The sensitivity of the cells to low temperature is variable and largely relies on the plant species.
• The different types of freezing methods used are as follows:
• 1. Slow-freezing method:
  • The tissue or the essential plant material is allowed to slowly freeze at a slow cooling rates of 0.5-5°C/min from 0°C to -100°C.
  • Then it is transferred to liquid nitrogen.
  •  Slow-freezing method facilitates the flow of water from the cells to the outside.
  • This avoids intracellular freezing and promotes extracellular ice formation.
  • Because of this, the plant cells are partially dehydrated and can survive better.
  • The slow-freezing technique is successfully employed for the cryopreservation of suspension cultures.
• 2. Rapid freezing method:
  • This process is quite simple.
  • In this technique, the vial containing plant material is plunged into liquid nitrogen.
  • During rapid freezing,  reduction in temperature from -300° to -1000°C/min occurs.
  • The freezing process occurs so quickly that small ice crystals are formed within the cells.
  •  In addition to it, the growth of intracellular ice crystals is also minimum.
  • Rapid freezing technique is applied for the cryopreservation of shoot tips and somatic embryos.
• 3. Stepwise freezing method:
  • This technique is a combination of slow and rapid freezing procedures having the advantages of both, and occurs in a stepwise manner.
  • Firstly, the plant material is cooled to an intermediate temperature.
  • Then it is kept there for about 30 minutes.
  • Finally, it is rapidly cooled by plunging it into liquid nitrogen.
  • Stepwise freezing method has been successfully applied for cryopreservation of suspension cultures, shoot apices and buds.
• 4. Dry freezing method:
  • It has been reported that the non-germinated dry seeds can survive freezing at very low temperature in comparison to water-imbibing seeds which are sensitive to cryogenic injuries.
  •  In a similar way, dehydrated cells are observed to have a better survival rate after cryopreservation.

step IV: Storage:

• The frozen cultures should be maintained at the specific temperature.
• Generally, the frozen cells/tissues are maintained at temperatures in the range of -70 to -196°C for storage.
• Although, with temperatures above -130°C, ice crystal growth may take place inside the cells which decreases viability of cells.
• The ideal storage is done in liquid N₂ refrigerator at 150°C in the vapour phase, or at   -196°C in the liquid phase.
• The final aim of storage is to halt all the cellular metabolic activities and preserve their viability.
• The temperature at -196°C in liquid nitrogen is regarded as ideal for long term storage.
• A regular and constant supply of liquid nitrogen to the liquid nitrogen refrigerator is necessary.
• It is essential to check the viability of the germplasm time and again in some samples.
• Proper documentation of the germplasm storage should be done.

step V: Thawing:

• Thawing is usually performed by plunging the frozen samples in ampoules into a warm water (temperature 37-45°C) bath with robust swirling.
• By this process, rapid thawing (at the rate of 500- 750°C min^-1) takes place, and this preserves the cells from the damaging effects from ice crystal formation.
• As soon as the thawing occurs (ice completely melts), the ampoules are transferred to a water bath at temperature 20-25°C at the same instant.
• The cells get damaged if left in warm (37-45°C) water bath for long time.
• For the cryopreserved material (cells/tissues) where the water content has been decreased to an optimal level before freezing, the process of thawing becomes less vital.

step VI: Re-culture:

• To remove cryoprotectants, the thawed germplasm is washed various times.
• Following standard procedures, this material is then re-cultured in a fresh medium.
• In some cases, the direct culture of  the thawed material is preferred without washing.
•  It is so because certain vital substances, released from the cells during freezing, are assumed to enhance in vitro cultures.

step VII: Measurement of viability:

• The measurement of survival or viability of the frozen materials can be performed at any stage of cryopreservation or after thawing or re-culture.
• The techniques used to determine viability of cryopreserved cells are the same as applied for cell cultures.
• The commonly used techniques are staining techniques using triphenyl tetrazolium chloride (TTC), Evan’s blue and fluorescein diacetate (FDA).
• The entry of cryopreserved cells into cell division and regrowth in culture is the best indicator to measure the viability of them.
• This can be evaluated by the using following expression.

step VIII: Plant regeneration:

• The regeneration of the desired plant is the ultimate purpose of cryopreservation of germplasm.
• The cryopreserved cells/tissues have to be carefully nursed, and grown for appropriate plant growth and regeneration .
• Along with maintenance of proper environmental conditions, addition of certain growth promoting substances is often essential for successful plant regeneration.

Limitations for Cryopreservation:

• An individual with good technical and theoretical knowledge of living plant cells as well as cryopreservation method is required.

Precautions for cryopreservation:

• The formation of ice crystals inside the cells should be prevented as they are responsible for causing injury to the organelles and the cell.
• Cells might be damaged if the intracellular concentration of solutes is high.
• Leakage of certain solutes from the cell during freezing should be checked.
• The physiological status of the plant material is also essential.

Cryopreservation: Principle, Process, limitations and precautions

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• In vitro method is an advanced technology of ex situ conservation for the preservation of genetic materials.
• In vitro methods employing shoots, meristems and embryos are ideally suitable for the preservation of germplasm of vegetatively propagated plants.
• This approach can also preserve plants with recalcitrant seeds and genetically engineered materials along with orthodox plants.
• The conservation implies preservation of cells, calluses or tissues of selected plant species in sealed test tubes in in vitro method.
• This conservation depends on principle that plant cells are totipotent and plant materials can be kept alive for infinite period of time as in vitro cultures.
• Advantages:
  • Requires less area for preservation of large quantities of materials.
  • The germplasm are preserved in pathogen-free environment.
  • Genetic materials are protected against the nature’s hazards.
  • Large number of plants can be obtained from the germplasm stock whenever required.
  • Since the germplasm is kept under aseptic conditions, it can be easily transported.
• Disadvantage:
  • It requires constant electricity, skilled manpower and high technology.

Techniques for the in vitro conservation of germplasm:

1. Cryopreservation (freeze-preservation)
2. Cold storage
3. Low-pressure and low-oxygen storage

1. Cryopreservation:

• Cryopreservation (Greek, krayos-frost) actually means preservation in the frozen state.
• Cryopreservation is based on the principle where the metabolism or division of plant cells and tissue cultures are completely halted by reducing temperatures with the involvement of cryoprotectants.
• This approach is highly applicable for the conservation of plant species in danger of extinction.
• Cryopreservation broadly refers to the storage of germplasm at very low temperatures:
  • i. Over solid CO₂  (at -79°C)
  • ii. Low temperature deep freezers (at -80°C)
  • iii. In vapour phase nitrogen (at -150°C)
  • iv. In liquid N₂ (at -196°C)
• Out of these, the most commonly used cryopreservation is use of liquid nitrogen.
•  At the temperature of liquid nitrogen (-196°C), the cells remain in totally inactive state and thus can be preserved for long time.
• Cryopreservation has been applied for germplasm conservation of several plant species e.g. rice, wheat, peanut, cassava, sugarcane, strawberry, coconut.
•  Various plants can be regenerated from cells, meristems and embryos stored in cryopreservation.

2. Cold Storage:

• Germplasm conservation at a low and non-freezing temperatures (1-9°C) is involved in this stage.
• In contrast to complete stoppage of cryopreservation, the growth of the plant material is slowed down in cold storage.
• Thus, cold storage is considered as a slow growth germplasm conservation method.
• This approach avoids the cryogenic injuries of plant material.
• This step is simple, economical and results germplasm with good survival rate.
• This approach stores many in vitro developed shoots/plants of fruit tree species for e.g. grape plants, strawberry plants.
• With the addition of a few drops of medium periodically (once in 2-3 months), virus- free strawberry plants could be conserved at 10°C for about 6 years.

3. Low-Pressure and Low-Oxygen Storage:

• Low-pressure storage (LPS) and low-oxygen storage (LOS) are other alternatives for the cryopreservation and cold storage which have been developed for germplasm conservation.

Low-Pressure Storage (LPS):

• The atmospheric pressure surrounding the plant material is decreased in low pressure storage.
• This yields in a partial reduction of the pressure exerted by the gases around the germplasm.
• The lowering of partial pressure decreases the in vitro growth of plants (of organized or unorganized tissues).
• Low-pressure storage systems are essential for both short and long-term storage of plant materials.
• The short-term storage is specifically useful to enhance the shelf life of many plant materials e.g. fruits, vegetables, cut flowers, plant cuttings.
• The storage of germplasm grown in cultures can be done for long term under low pressure.
• Besides germplasm preservation, LPS decreases the activity of pathogenic organisms and prevents spore germination in the plant culture systems.

Low-Oxygen Storage (LOS):

• In the low-oxygen storage, the oxygen concentration is decreased, but the atmospheric pressure (260 mm Hg) is maintained by the addition of inert gases (specifically nitrogen).
• There is reduction in plant tissue growth if the partial pressure of oxygen is below 50 mm Hg.
• It is because, with less availability of O₂, the production of CO₂ is low.
•  As a result, the photosynthetic activity is decreased, thereby halting the plant tissue growth and dimension.
• Limitations:
  • The long-term conservation of plant materials by low-oxygen storage may halt the plant growth after certain dimensions.

In vitro methods of germplasm conservation

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• Germplasm in a broad way can be defined as the hereditary material i.e. total content of genes which is inherited by the off springs through germ cells.
• Germplasm serves as the raw material for the breeder to produce various crops. Therefore, conservation of germplasm has importance in all breeding programmes.
• In previous days, humans gained the knowledge about the use of plants for food , shelter and many more, thus they started saving selected seeds or vegetative propagules from one season to the next one. The possibility of life on earth is mainly due to the plants as it is the crucial component of the ecosystem, thus its preservation is our responsibility for the continuation of life.
• In other words, it may be regarded as the conventional germplasm preservation and management, which is highly precious in breeding programmes.
• The main objective of germplasm conservation is to preserve the genetic diversity of  selected plants or genetic stock for its utilization at any time in future.
• In recent years, the primitive and conventionally used agricultural plants are being replaced by many new plant species with desired and improved characteristics.
•  It is very crucial to conserve the endangered plants otherwise some of the important genetic traits possessed by the primitive plants may be lost.
• It has been estimated that up to 100,000 plants, depicting more than one third of all the world’s plant species, are currently threatened or face extinction in the wild.
• Biodiversity is seriously threatened, particularly, in Europe.
• Biotechnological approaches provide several conservation possibilities which have the potential to support in situ protection strategies and provide complementary conservation options.
• International Board of Plant Genetic Resources (IBPGR), a global body has been established for germplasm conservation.
• Its main aim is to provide essential support for collection, conservation and utilization of plant genetic resources all over the world.

Types of germplasm conservation:

There are mainly two types of germplasm conservation which are

• In-situ conservation
• Ex-situ conservation

In-situ conservation:

• The conservation of germplasm in their natural habitat by constructing national parks/gene sanctuaries is termed as in-situ conservation.
• It is regarded as a high priority germplasm preservation programme.
• It helps in the continuation of plant life in the ecological community.
• It aims in conservation of great number of cultivated and wild species in less area.
• One of the advantages of in-situ conservation is that it continues the evolution of the species along with the allowance of appearance of new recombinant form.
• limitations of in-situ conservation
  • Security is very low in absence of controlled monitoring.
  • Various environmental hazards can degrade the germplasm.
  • Expensive maintenance cost for large number of genotypes.

Ex-situ conservation:

• The genetic materials can be conserved either by collecting plants and kept in normal growing conditions or in the form of seeds in seed banks, through tissue culture and low temp maintained by liquid N_2. This type of conservation is termed as ex-situ conservation.
• It is the major method for the preservation of germplasm obtained from both wild and cultivated plant materials.
• Genetic resources either in form of seeds or plants cells, tissues or organs can be preserved as gene banks for long term storage under favourable conditions.
• Proper knowledge of plant diversity, their genetic structure and the methods involved in sampling, regeneration, maintenance of gene pools is important for the successful accomplishment of gene banks.
• Ex-situ conservation cannot allow the plants to continue its evolutionary process but it ensures the availability of stored genetic materials in need and its safety.
• Sugarcane, cocoa and rubber are stored in this way.

Technique of Germplasm conservation

Seeds conservation:

• Usually, seeds are the most efficient, simple, economic and convenient resources to conserve plant germplasm.
• This is because many plants are regenerated through seeds, and seeds cover relatively small space. In addition, seeds can be easily moved to various places.
• Seed conservation is the most broadly used method of ex-situ conservation.
• It is performed by drying the seeds at 10-25°C, 10-15% relative humidity followed by storage at -18°C.
• limitations:
  • Viability of seeds is decreased or lost along with time.
  •  Seeds are destructed by insect or pathogen attack.
  • This approach is only confined to seed propagating plants, and thus it is useless for vegetatively propagated plants e.g. potato, Ipomoea, Dioscorea.
  •  Heterogenous seeds are not suitable for true genotype maintenance.
  • Only orthodox seeds can be conserved by this method as the recalcitrant and intermediate seeds cannot stand the dessication.

Germplasm conservation

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• One of the most efficient methods of ex-situ conservation for sexually reproducing plants is the storage of conservation material in form of seeds.
• Every kind of seed has a distinct genetic makeup, thus consists a wide variety of genetic diversity.
• Seeds being small in size take up small space.
• At practical level, seed bank depends upon secure power supplies, requirement for careful monitoring, and periodical testing of seed viability.
• Seeds of orthodox types which has been previously dried to about 5-8% moisture content can be conserved for very long periods at temperatures below zero.
• The longevity varies from taxon to taxon, viability of seeds in medium-term storage (0°-5°C) can be 5-25 years whereas long term storage (-10°C to -20°C) can provide viability perhaps for a hundred years.
• Many tropical species produce seeds that possess no natural dormancy and die quickly if not allowed to germinate immediately. These are termed as recalcitrant seeds.
• Recalcitrant seeds are easily killed by the usual techniques of storing under reduced temperature and humidity.
• It is estimated that 50,000 plant species produce seeds that do not survive at low temperature and/or dehydration.
• Species with recalcitrant seeds and those who do not readily produce seeds are required to be maintained ex-situ as growing plants in field gene banks or as living collections.
• Recalcitrant fruits and seeds like Cocos nucifera (Coconut palm), Bertholetica excelsa (Brazil nut) are stored directly on mother trees in Sacred Grooves, Forest and Biosphere Reserves, National parks and in the Arboretums and Botanic gardens.
• There are Germplasm Storage Centers throughout the world where orthodox seeds are stored.
• The gene banks are closely related to plant collection activities either for taxonomic studies or breeding.
• The Consultative Group on International Agricultural Research (CGIAR) was established on 1971 to support a global network of gene banks which are located at 13 international agricultural research centers.
• The International Board for Plant Genetic Resources (IBPGR) and Crop Genetic Resource Centers have developed about 60 gene banks in the last 20 years with long- or medium- term storage facilities of crop plants.
• Currently only relatives of wheat (60 spp. or 75-80% of the total), potato (40 spp. or 70% of the total), tomato (10 spp or 90% of the total), and to limited extent, maize (15 spp. or 50% of the total) have been extensively collected and preserved in seed banks.
• Germplasm of only few traditional cultivars and wild relatives of crops has been collected and preserved by various Nepalese institutions, the few examples consists of rice, wheat, buckwheat, and maize in National Agricultural Research Council (NARC), buckwheat in Research Center for Applied Science and Technology (RECAST), many wild germplasm in National Herbarium and Royal Botanical Garden, Amaranth in Tribhuvan University (TU) while most wild relatives of crops still thrive only in the wild.
• The security of germplasm must be assured by making not only the germplasm available but also providing adequate information for a conservation effort to be sustainable.

Botanical gardens:

• According to Botanical Gardens Conservation International (BGCI), an independent UK based organization, Botanical gardens can be defined as public as public gardens which maintain collections of live plants mainly for study, for scientific research conservation or education.
• Botanical gardens fulfill an important role in preserving the world’s plant diversity by:
  • Growing large collections of endangered plants and holding them safely in cultivation or seed banks in case wild populations are destroyed
  • Reintroducing plants to the wild as a part of species recovery process
  • Undertaking botanical research to document and record the plants of the world, region or country and their characteristics, for example, herbaria contain millions pf specimens as a permanent reference on plant diversity
  • Promoting environmental awareness among the public through their education work
  • Providing expertise and training to grow plants
  • Helping to conserve natural vegetation by maintaining nature reserves and working with others to study, monitor and conserve plants and their ecology in the wild.
  • In global perspectives, botanic gardens are an essential network of botanical resource centers for environmental conservation.
  • Botanic gardens have become a place of multiple significance both for the general public as well as scientific community.
  • Rhododendrons in Royal Botanic Garden, Edinburgh, Chrysanthemums in Missouri Botanical Garden, USA and Botanical Garden, Kyoto, Tulips in Leyden University Garden, The Netherlands, different kinds of flowering shrubs in Royal botanic Gardens, Kew and Arnold Arboretum, USA are quite a few places that represent fascinating examples of collection of indigenous as well as exotic plants.
  • Above all immediate role of botanical gardens in the ex-situ conservation of rare and endangered species lies in research and education rather than in conservation.
• In nature, plants commonly exist in small populations. Example includes many rare endemic which occur in isolated areas where, in general, conservation priorities are low.
• It is quite often that too little is known of the ecology of many plant species.
• Further, destruction of natural habitats is taking place at an alarming rate.
• Ex-situ conservation in botanic garden serves the purpose of buffer against extinction of rare and endangered species as well as promote interdisciplinary research and instruction.
• Botanic Gardens Conservation International estimates that there are about 1600 botanic gardens in the world.
• They grow tens of thousands of plant species between them, probably as much as a quarter of all the world’s flowering plants and fens are in their collections.
• There are few botanic gardens in Nepal which are poorly funded and inadequately developed, thus, they have not been able to play significant role in conservation and research. Some of notable botanic gardens are Botanical Garden, Godavari and botanic garden of Tribhuvan University, Kirtipur.

Seed banks and Botanical gardens: ex-situ conservation

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• Biodiversity use and conservation education
• Integrated health care
• Agroforestry
• Afforestation
• Cottage industry
• Communities involvement in Biodiversity Conservation
• Improved hearth for cooking
• Traditional agro-ecosystems and biodiversity conservation
• Keystone species and conservation

1. Biodiversity use and conservation education:

• Forest resources are rich in medicinal and food plants, other non-wood forest products, timber, fodder, fuelwood, thatch-grass, sabia-grass, etc. People directly or indirectly depend on these products.
• If we talk about majority of people, their main priority is harvesting the resources whereas conservation always remains the second priority.
• People should be aware about the direct and indirect benefits from the forest and their change in attitude is needed.
• Initiation of educational programs that comprises teaching of conservation topics and its extension to adult literacy and schools will bring beneficial change in people’s attitude.
• Increase in enrollment of children in schools by providing some kind of extra benefit on token basis should be implemented.
• Department of National Parks and Wildlife Conservation in co-operation with local people can actively play an important role in conservation of protected areas in Nepal by publishing brochures in local language.

2. Integrated health care:

• After documentation of traditionally used plants, and selection of plants that are safe, effective and easily available or cultivated, these plants may be integrated into modern health care system.
• Fansworth under a joint UNICEF/WHO study investigation for health needs of developing world concluded that the combination of traditional with modern system health care is truly effective and affordable for low income groups.
• Development of an integrated health care system project in Madagascar which is funded by WWF has involved a team of people including traditional healers, ethnobotanists, medical doctors, and pharmacologists for sustainable utilization of the indigenous plants and return results to laboratory for analyses and to community members.
• An integrated program run by local Non-Government organization working at the grass-root level would aid to effectively motivate the community for integrated health care.
• Baudha-Bahunipati Family Welfare Project run by World Neighbors in Sindhupalchowk District, eastern Nepal has run an integrated program that comprise family planning adopted by 22% of fertile couples, and fertility rates reduced from 5.8 to 3.2 children per couple, built 55 new drinking water systems and 525 latrines, project now replicated in 38 villages where 153,000 people live.
  

3. Agroforestry:

• It combines growing trees along with agriculture or livestock or both on the same piece of land side by side.
• International Center for Research in Agroforestry (ICRAF) defines agroforestry as collective name for land-use systems and practices where woody perennials are deliberately integrated with other crops or animals on the same land management unit.
• Agroforestry is usually practiced with the intention of developing a more sustainable form of land use that can improve farm productivity and welfare of the rural community.
• In current view, agroforestry provides ways to eliminate deforestation and land depletion and thus reduce poverty.
• The increasing integration of trees and crops into land-use system can be viewed as a passage towards forming an ecological niche that are occupied by several organisms, making the system ecologically stable, and biologically diverse.
• Agroforestry is a traditional indigenous form of land-use is practiced by many farmers in the Asia-Pacific region having 69% of world’s agricultural population and only 28% world’s agricultural land.
• Local people are greatly benefited from such indigenous system in Nepal.
• Emphasis on cultivation of indigenous and multipurpose forest trees with medicinal herbs should be given for the development of agroforestry.
  

4. Afforestation:

• Multipurpose tree including legumes are marvelous, multipurpose resources that can protect and stabilize the soil, save water, symbiotically fix atmospheric nitrogen, produce valuable wood and fodder, and certain proteins and lipids for diet.
• In the most degraded areas where trees are difficult to grow, attention should be given to the shrubs which are highly palatable to cattle, such areas are found in north of Jomsom of Nepal.
• In the midhills and the Terai, effort should be made to develop afforestation programs prioritizing popularization of indigenous trees including Sisso, Satisal, Siris.

5. Cottage industry:

• Plants resources such as bamboos, fiber plants, rattans, leaves which are used to develop cottage industries in Nepal.
• Some of the important forest resources used for cottage industries in Nepal are Bamboos (Dendrocalamus strictus, D. hamiltonii), Lokhta (Daphne papyracea and D. bholua), Munj grass (Saccharum bengalense), Sabai grass (Eulaliopsis binata).
• Trainings should be organized in order to improve traditional skills of the villagers involved in the occupation.
• High market values provide incentives to exploit the resources and often indiscriminately that their population have depleted drastically in wild.
• Thus, market for these goods must be developed carefully to ensure that the harvest rate doesnot exceed the regeneration rate.
  

6. Communities involvement in Biodiversity Conservation:

• As per rule, the forest and protected areas in Nepal are banned to public for collection of wood and fodder.
• Still, the collection of fuel-wood for household cooking and fodder for animals undertaking mostly by women and children are not fully restricted.
• Also, people who use forest daily chop down trees illegally for sale as fuel. They belong to poor and low-level families and they have no interest in implementing the recommendations of the forest committee.
• Promotion of the community-based resource management systems of indigenous people will help in accomplishing the conservation of indigenous knowledge for biodiversity conservation.

7. Improved hearth for cooking:

• Due to the rapid growth in population and lack of supply of indigenous energy sources in Nepal, the use of traditional energy sources has been extensively increased.
• In Nepal, the major sources of energy are fuelwood (68% of total consumption), agricultural residues (15%), animal dung (12%), petroleum fuels (3%), coal (0.7%), and electricity (0.6%).
• Over-exploitation of traditional energy resources, increasing demand due to population growth, and low level exploitation of commercial energy resources best decribes the current condition of Nepal’s energy resources.
• Forest being the indigenous source of fuelwood, the extraction of fuelwood is leading to the degradation of forest ultimately causing biodiversity loss.
• A thorough examination of the existing earthen hearths can ne made and efficient hearths can be popularized particularly in villages to reduce the energy consumption.
• Likewise, the marginal lands that can be used for afforestation by community people may decrease pressure in the forest. Besides, proper alternative should be searched in Nepal.

8. Traditional agro-ecosystem and biodiversity conservation:

• Highly diverse plant species are maintained in the farm.
• Recent patterns of agricultural development are depleting soils, genetic diversity, species diversity both in managed fields and surrounding habitats.
• Due to introduction of imported seed of crops, fertilizers and pesticides, traditional agro-ecosystems are under threat in Nepal.
• A decline in the crop yield has been gradually noticed in lack of sufficient chemicals which the country imports.
• To maintain the diversity and productivity of traditional genetic resources of agriculture, the government should promote and encourage the farmers to maintain traditional agro-ecosytems.

9. Keystone species and conservation:

• An important category of plants that tend to be overlooked in consideration of genetic conservation are ‘keystone’ or ‘indicator’ or ‘target’ species.
• These are species whose presence is important in maintaining the organization and diversity of an area and whose absence would significantly decline biodiversity of an area.
• Terborgh predicted that elimination of presumed keystone, ‘palm nuts, figs and nectars’ community type would affect predicted loss of ½ to ¾ of total bird and mammal biomass.
• Selection of indicator species to monitor the ecological viability of the region need to be identified, as their removal could either rise or reduce species diversity and affect optimum ecological balance in a region.
• In Nepal’s perspective, due emphasis should be given on research and traditional ecological knowledge to identify keystone species that will be used in biodiversity monitoring.

Strategies for biodiversity conservation

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• Biofertilizers are the substances of biological origin (microorganisms), which when added to the soil enhances its fertility and promotes plant growth.
• Broadly, biofertilizer constitutes of living organisms which include mycorrhizal fungi, blue-green algae, and bacteria. Biofertilizers simply consists of specific strains of microorganisms like bacteria, fungi, algae or their combinations.
•  Mycorrhizal fungi uptakes minerals from organic matter for the plant whereas cyanobacteria are characterized by the property of nitrogen fixation. The process of conversion of the atmospheric Nitrogen into nitrogenous compounds in soil ready for plant to absorb in series of reaction is termed as nitrogen fixation.
• And the bacteria can be nitrogen fixers or phosphate solubilizers. They convert insoluble forms of soil phosphorus into soluble forms. As a result, phosphorus will be available for plants
• Biofertilizers are economical, effective, and renewable sources of plant nutrients.
• The role of biofertilizers in agriculture production shows a special importance, particularly in the present context of the sky-rocketing cost of agriculture inputs.
• The selective strains of microorganisms be used to prepare biofertilizer, for economic purpose and for significant results.
• When these prepared biofertilizers are incorporated with seeds, setts, seedlings or soil, they improve crop productivity and soil health, by the biological nitrogen fixation process, solubilisation and uptake of other nutrients and synthesis of growth-promoting substances such as vitamins and plant growth hormones.
• They also produces capsular polysaccharides to prevent soil erosion.
• They also convert immobilised chemical into soluble forms and make them accessible to the plants.
• Biofertilizers is highly advantageous over chemical fertilisers.

Advantages of biofertilizers:

• The biofertilizers has special contribution to agriculture due to the following advantages:
  • Biofertilizers act as supplements to chemical fertilisers.
  • Biofertilizers are cost-friendly and can aid to decrease consumption of such fertilisers.
  • Microbes in biofertilizers provide atmospheric nitrogen directly to plants.
  • They aid in solubilisation and mineralisation of other plant nutrients like phosphates.
  • Better synthesis and availability of hormones, vitamins, auxins and other growth-promoting substances improves plant growth.
  • On an average crop yield elevates by 10–20 percent by their use.
  • They help in the multiplication and survival of beneficial micro-organisms in the root region (rhizospheric bacteria).
  • They control and inhibit pathogenic soil bacteria.
  • They enhance soil texture by increasing amount of humus and maintain soil fertility.
  • Eco-friendly in nature and pollution free.

Types of biofertilizers:

• Biofertilizers are broadly classified into two main groups:
  1. Biological nitrogen fixing biofertilizers
  2. Phosphate solubilising (mobilising) biofertilizers
• Biological nitrogen fixing biofertilizers consist of micro-organisms which have the ability to fix biological molecular nitrogen (N2) either symbiotically or asymbiotically in the plants.
• Phosphate solubilising biofertilizers are capable of solubilising or mobilising the fixed insoluble phosphates of the soil

• However, Biofertilizers are divided into five main categories.
• These five types are again divided in sub-types as follows:
•  i. Nitrogen fixers:
  • Symbiotic: Rhizobium, Frankia, Anabaena azollae.
  • Free living: Azotobacter, Clostridium, Blue green algae, Azolla, Acetobacter, Nostoc, Anabaena.
  • Associative symbiotic: Azospirillum.
•  ii. Phosphate supplier:
  • Phosphate solubiliser:
    Bacteria: Bacillus megaterium, Phosphaticum, Bacillus circulans, Pseudomonas striata, Pseudomonas sp..
  • Fungi: Penicillium sp, Aspergillus awamori.
• iii. Phosphate absorber biofertilisers:
  • Arbuscular mycorrhiza: Glomus sp., Gigaspora sp., Acaulospora sp., Scutellospora sp. and Sclerocystis sp., Ectomycorrhiza: Laccaria sp., Pisolithus sp., Boletus sp., Amanita sp. Orchid mycorrhiza: Rhizoctonia solani.
•  iv. Sulphur supplier:
  • Thiobacillus novellus, Aspergillus.
• v. Micronutrients supplier:
  • Silicate and Zinc solubilisers: Bacillus sp.

Application-Method of applying biofertilizers

• The important method of biofertilizers applications are listed below:
• Seedling root dip:
  • This method is usually applicable for rice crops. The seedlings are sowed in the bed of water and kept for 8-10 hours.
• Seed Treatment:
  • The seeds are soaked in the mixture of nitrogen and phosphorus fertilizers. These seeds are then left to dry and are sown as soon as possible.
• Soil Treatment:
  • The biofertilizers along with the compost fertilizers are blended and kept for one night. This mixture is then scattered on the soil where the seeds have to be sown.

Disadvantages of biofertilizers

• Biofertilizers are supplement to chemical fertilizers but not substitute to it.
• Biofertilizers only result in 20 to 30 percent increase in crop production. They do not cause marked increase in productivity like chemical fertilizer.
• Specific fertilizers are required for specific crops. This is more applicable to symbiotic micro-organisms. If non-specific Rhizobium is used as fertiliser, then it will not lead to root nodulation and increase in crop production.
• During the production of microbial fertiliser, strict aseptic precaution is needed. Contamination is a common issue during microbial mass production.
• If exposed for long time in sunlight, microbes get killed as they are light-sensitive.
• Microbial fertilizer must be used within six months after production when stored at room temperature and within two years if stored at chilling temperature.
• Efficiency of microbial fertilizer depends on soil character, such as, moisture content, pH, temperature, organic matter and types of micro-organisms present. When these factors are unfavourable microbial fertilizer may not be effective in enhancing the soil fertility.

Biofertilizer- Advantages, Types, methods of application and Disadvantages

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• The combination of biotic and abiotic factors composes environment, which surrounds us and other organisms.
• Abiotic factors includes water, air, soil, light, temperature, etc that affects human beings the least.
• Biotic factors are other factors that influence the environment much more in comparison to abiotic factors.
•  Biotic factors consists all forms of life like animals, plants, micro-organisms, etc.
• Human is an incorporated part of the environment and have very intimate relationship with each other.
• The environment where human lives affects the social of human.
• It has been observed that water, soil, climate and language of human differ from one place to other which is responsible for the generation of various types of social and cultural activities all over the world.
• The people at hills have distinct life styles as compared to people in the low land area. Similarly, people around the world differ in their food, cloth, traditions, festivals, etc. All these are affected by the factors around them.
• A. G. Tensley coined the term ecology.
• The study of interaction and inter-relationship between an organism of some kind and its environment is termed as ecology.
•  In ecology,  ecological ‘Niche’ is role of an organism or species played in ecosystem.
•  An organism niches consists everything that are influenced by the organism independent of its lifetime.
• Ecology is studied to understand how nature interacts with living systems and how living systems respond to nature.
•  Thus, ecology is a study that helps scientist to achieve new motives by developing technical methods to protect the natural environment.
• Environmental biotechnology can play a crucial role in balancing interaction level of biotic and abiotic systems by developing these advanced methods for preserving environment and ecological system.
• Ecology has been defined as a study of interaction among living beings viz. animal, plants and their environment.
•  Ecology may be studied with particular reference to either animals or plants.
•  Thus, it can be divided in to animal ecology and plant ecology.
• It is difficult to study animal ecology completely without having a proper knowledge of plant ecology.
•  The animal and plants are given equal emphasis; thus the term bioecology is often used.
• The term ‘Synecology’ refers to the study of relation of communities with environment.
• The term ‘autecology’ refers to the study of relation of species with environment.

Components of environment

• There are three major components of environment.
• These are as follows:
  1.   Physical component.
  2. Biological component.
  3. Social component.

Physical component of environment:

• Physical component of environment includes air, water, soil, light, temperature, climate, etc.
• The physical components are also termed as abiotic components of the environment.
• These environmental components accounts for determination of living conditions for the human population.
• Physical component of the environment is again classified into three parts as follows:
  • Atmosphere (gas)
  • Hydrosphere (liquid)
  • Lithosphere (solid)
    • Structure of atmosphere:
    •  The atmosphere is broadly classified into four major zones.
    • These zones are named as Troposphere, Stratosphere, Mesosphere and Thermosphere.
• These three parts portrays the three important states of matter forming the environment.
• This physical component of environment includes abiotic components like air, water and soil.
• All these abiotic components affect much more to all living organisms along with human.
• Water and temperature are the most significant abiotic components affecting living beings as water is important for survival of livings.
• Water plays a vital role to keep optimum temperature of the body and perform metabolic activities.
• All living things perform in a particular range of temperature.
• Growth of living beings will be affected when temperature will not fall in that range.
• Air is one of the major physical components, which is needed for respiration.
• All living beings along with plants and animals need oxygen for their survival.
• In metabolic process, oxygen is inhaled into the body and exhaled in form of CO2.
• On contrast to it, the plants consume CO2 for food preparation during photosynthesis and releases oxygen to the emvironment.
• Soil is another important component for all living beings to build their habitat.
• It is the soil where plant grows and human builds houses to live in.
• Soil serves to retain ground water which is obtainable for drinking and other farming activities.

Biological component of environement:

• The biological component of environment is also termed as biotic component.
• This biological component includes all living things like plants, animals and small micro-organisms like bacteria, algae and fungi.
• Biological component interelates with the abiotic component of the environment. Interaction of these two components forms various ecosystems like forest ecosystem, pond ecosystem, marine ecosystem, desert ecosystem, etc.
•  Biosphere is independent and large ecosystem.
• All ecosystems has three different types of living organisms; i.e. producers, consumers and decomposers.
• Producer includes mainly green plants and other photosynthetic bacteria which synthesizes various organic substances such as carbohydrates, proteins, etc., with the aid of water, soil and light energy.
• Consumers rely on green plants for their nutrition as these green plants produces organic food materials.
• Decomposers are responsible to decompose dead plants and animals and yields various important minerals for the running of the natural cycles.

Social component of environment:

• The third component of environment is social component.
• This component is mainly consists of various groups of population of different living beings like birds, animals, etc.
• Human is the most independent and intelligent living organism.
• Like all other living creatures on earth, man constructs house, prepares food and delivers waste materials to the environment.
• It has been said about human by Greek philosopher, Aristotle that human is a social animal.
• He prepared various laws, policies for the proper functioning of the society.
• These three components of the environment give rise to four important zones like Atmosphere, Hydrosphere, Lithosphere and Biosphere.
• There is continual interaction among these four zones.
• These interactions include the transport of various elements, compounds and different forms of energy.

Environment and its components

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• The food chain is an ideal representation of flow of energy in the ecosystem.
• In food chain, the plants or producers are consumed by only the primary consumers, primary consumers are fed by only the secondary consumers and so on.
• The producers that are capable to produce their own food are called autotrophs.
• Any food chain consists of three main tropic levels, viz., producers, consumers and decomposers.
• The energy efficiency of each tropic level is very low. Hence, shorter the food chain greater will be the accessibility of food.
•  The typical food chain in a ground ecosystem proceeds as grass      mouse—————-> snake ————>     hawk.
• Food webs are more complex and are interrelated at different tropic levels.
• Organisms have more than one choice for food and hence can survive better.
• Hawks don’t restrict their food to snakes, snakes eat animals other than mice, and mice eat grass as well as grasshoppers, and so on.
• A more realistic illustration of feeding habits in an ecosystem is called a food web.

 Food web:

• Charles Elton presented the food web concept in year 1927, which he termed as food cycle.
• Charles Elton described the concept of food web as:
• The carnivore animals prey on the herbivores.
• These herbivores obtain the energy from sunlight.
• The later carnivores may also be preyed upon by other carnivores.
• Until a reach where an animal has no enemies it forms a terminus on this food cycle.
• There are chains of animals that are related together by food, and all are dependent on plants in the long run.
• This is termed as a food chain and all the food chains in a community is known as the food web.
• A food web is a graphical depiction of feeding connections among species of an ecological community.
• Food web includes food chains of a particular ecosystem.
• The food web is an illustration of various techniques of feeding that links the ecosystem.
• The food web also explains the energy flow through species of a community as a result of their feeding relationships.
• All the food chains are interconnected and overlapping within an ecosystem and they constitute a food web.
• In natural environment or an ecosystem, the relationships between the food chains are interrelated.
• These relationships are very complex, as one organism may be a part of multiple food chains.
• Hence, a web like structure is formed in place of a linear food chain.
• The web like structure if formed with the interlinked food chain and such matrix that is interconnected is known as a food web.
• Food webs are an inseparable part of an ecosystem; these food webs permit an organism to obtain food from more than one type of organism of the lower trophic level.
• Every living being is responsible and is a part of multiple food chains in the given ecosystem.

Ecological pyramids:

• The trophic levels of different organisms based on their ecological position as producer to final consumer is represented by ecological pyramid.
• The food producer is present at the base of the pyramid and on the top.
• Other consumer trophic levels are present in between.
• The pyramid includes a number of horizontal bars presenting specific trophic levels.
• The length of each bar stands for the total number of individuals or biomass or energy at each trophic level in an ecosystem.
• An ecological pyramid is a graphical representation outlined to show the biomass or bio productivity at each trophic level in a given ecosystem.
• These are trophic pyramid, energy pyramid, or sometimes food pyramid.
• Biomass is the quantity of living or organic matter present in an organism.
• Biomass pyramids represent the amount of biomass, and how much of it is present in the organisms at each trophic level.
• The productivity pyramids shows the production or turnover in biomass.
• Ecological pyramids initiates with producers on the bottom such as green plants and proceed through the various trophic levels such as herbivores that feed on plants, then carnivores that feed on herbivores, then carnivores that feed those carnivores, and so on.
• The highest level is shown at the top of the chain.
• An ecological pyramid of biomass represents the relationship between biomass and trophic level by quantifying the biomass present at each trophic level of an ecological community at a particular time.
• It is a graphical representation of biomass present in per unit area in different trophic levels.
• Flow of energy through the food chain will be in a predictable way, entering at the base of the food chain, by photosynthesis in primary producers, and then moving up the food chain to higher trophic levels.
• The transfer of energy from one trophic level to the next is not efficient.
• It may also be useful and productive to analyse how the number and biomass of organisms differs across trophic levels.
• Both the number and biomass of organisms at each trophic level should be affected by the amount of energy joining that trophic level.
• When there is a direct correlation between energy, numbers, and biomass then biomass pyramids and numbers pyramids will be formed.
• However, the relationship between energy, biomass, and number can be complex by the growth form and size of organisms and ecological relationships occurring among trophic levels.

 Types of pyramids:

• The ecological pyramids are of three categories:
  1. Pyramid of numbers.
  2. Pyramid of biomass.
  3. Pyramid of energy or productivity.

1. Pyramid of numbers:

• Pyramid of numbers represents the population of trophic level as the total number of individuals of different species present at each trophic level.
• Pyramid of numbers may be upright and or completely inverted depending upon count of individual present and so.
• The pyramid of number does not completely define the trophic structure for an ecosystem as it is very tough to count all the organisms present there.
• Pyramid of number- upright: grassland ecosystem
• In this pyramid, the number of individuals is decreased from lower level to higher trophic level.
• The examples of pyramid of numbers are Grassland ecosystem and pond ecosystem.
• In grass ecosystem, at base (lowest trophic level) grass is present in plentiful amount.
• The next higher trophic level is primary consumer i.e. herbivore (example – grasshopper).
• The number count of grasshopper is less than that of grass.
• The next energy level is primary carnivore (example: rat). The number of rats are less than grasshopper, because, they feed on grasshopper.
• The next higher trophic level is secondary carnivore (example: snakes). They feed on rats.
• The next higher trophic level is the top carnivore. (example – Hawk).
• As we reach each higher trophic level, the numbers of individual decreases from lower to higher trophic level.
• Pyramid of numbers – inverted: tree ecosystem
• In this type of pyramid, the number of individuals is increased from lower level to higher trophic level. Example, tree ecosystem.

2. Pyramid of biomass:

• Pyramid of biomass represents the total dry weight of organisms.
• It is usually determined by collecting all organisms inavding each trophic level separately and measuring their dry weight.
• This will serve to solve the size difference problem because all kinds of organisms at a trophic level are weighed.
• The unit for measurement of biomass is g/m2.
• The biomass of a species is expressed in terms of fresh or dry weight.
• Measurement of biomass in terms of dry weight is considered more accurate.
• Certain mass of living material of each trophic level at a particular time called as standing crop.
• The standing crop is measured as the mass of living organisms (biomass) or the number in a unit area.
• pyramid of biomass: upright
• The pyramid of biomass on land contains a large base of primary producers with a lesser trophic level present on top.
• The biomass of producer termed as autotrophs is at the maximum trophic level.
• The biomass of next trophic level from base, i.e., primary consumers is less than the producers.
• The biomass of next higher trophic level, i.e., secondary consumers is less than the primary consumers.
• The top, high trophic level consists very less amount of biomass.
• On other hand, in many aquatic ecosystems, the pyramid of biomass may be present in an inverted form whereas pyramid of numbers for aquatic ecosystem is upright.
• It is because the producers are small phytoplankton that grow and reproduce very rapidly.
• Here, the pyramid of biomass has a small base as compared to the consumer biomass at any instant actually exceeding the producer biomass and the pyramid is represent in inverted shape.

3. Pyramid of energy:

• The pyramid of energy represents the flow of energy from lower trophic level to higher trophic level.
• During the flow of energy from one organism to other, there is remarkable loss of energy.
• This loss of energy is in the form of heat.
• The primary producers like the autotrophs contain more amount of energy available.
• The least energy is available in the tertiary consumers.
• Thus, shorter food chain has more amount of energy available even at the highest trophic level.
• An energy pyramid is regarded most suitable to compare the functional roles of the trophic levels in an ecosystem.
• An energy pyramid represents the amount of energy at each trophic level and loss of energy taking place during transfer to another trophic level.
• Hence the pyramid is always upward, with a large energy base at the bottom.
• Suppose an ecosystem receives 1000 calories of light energy in a given day.
• Most of the energy is not absorbed by plants; some amount of energy is reflected back to space.
• Green plants utilise only a small portion of that absorbed energy, out of which the plant uses up some for respiration and of the 1000 calories, only 100 calories (10%) are stored as energy rich materials.
• Now, suppose an animal eats the plant containing 100 calorie of food energy, that animal uses some of it for its own metabolism and stores only 10 calorie as food energy.
• A lion that eats that animal gets an even smaller amount of energy.
• Thus, usable energy decreases while passing from sunlight to producer to herbivore to carnivore. Therefore, the energy pyramid will always be upright.

Food chain, food web and ecological pyramids

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