Mechanical Properties of Solids

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Mechanical Properties of Solids

Mechanical Properties of Solids

Before Learning, the Mechanical Properties of Solids, what is Matter The matter is broadly divided into three categories, viz. Solid, Liquid and Gas. Due to the strongest intermolecular force of attraction in solids, they are tough and have a definite shape and size. This force is relatively weak in liquids and so the shape is easily changed but liquids have a definite volume. In gases, the intermolecular force of attraction is minimum and hence, they do not have a definite shape, size, and volume. There is a fourth state of matter called plasma state in which matter exists in the ionized state. Plasma state is common in stars.

Solids

In solids, the constituent particles (atoms, molecules or ions) are held strongly at the position of minimum potential energy. Solids are of two categories :
  1. Crystalline Solids: They have a regular pattern of constituent particles in three-dimensional space. Hence, they have a definite external geometrical shape and a sharp melting point. They are an isotropic i.e. their physical properties like conductivity (thermal and electrical), refractive index, mechanical strength etc. have different values in different directions e.g. rice, sugar, quartz, diamond, rock salt, most of the metals & their compounds, etc.
  2. Amorphous or Glassy Solids: They have an irregular arrangement of particles. Hence, they do not have a definite external geometrical shape and sharp melting point. They are isotropic i.e. their physical properties have the same value in all directions e.g glass, cement, rubber, paraffin, plastic, etc.

Mechanical Properties of Solids based on Elasticity

Elasticity of Solids

The property of the body by virtue of which it tends to regain its original shape and size after the removal of applied forces, is called elasticity and body itself is called elastic body. Some Terms Related to Elasticity
  • Deforming Force: The force which when applied changes the configuration of the body, is called deforming force.
  • Perfect Elastic Body: A body which regains its original configuration immediately and completely after the removal of deforming force, is called perfectly elastic body e.g.., quartz, phosphor bronze.
  • Plastic Body. A body which does not regain its original configuration at all on the removal of deforming force from it is called plastic body e.g., putty, mud, paraffin wax etc. The body that remains in deformed shape even after the removal of deforming force is called a perfectly plastic body.
  • Elastic Limit. It is the upper limit of deforming force up to which, if deforming force is removed, the body regains its original form completely and beyond which, if deforming force is increased, the body loses its property of elasticity and gets deformed permanently.
  • Elastic After Effect: The temporary delay in regaining the original configuration of an elastic body after the removal of a deforming force, is called elastic after effect.
  • Elastic Fatigue. The property of an elastic body by virtue of which its behavior becomes less elastic under the action of repeated alternating deforming forces called elastic fatigue.
  • Stress When a deforming force is applied on a body, it changes its configuration due to which an internal force comes into play which tends to bring the body back to its initial configuration.
The internal restoring force acting per unit area of a deformed body is called stress

where σ is the stress, F is the force and A is the surface area.

Its unit is N/m² and dimensions are M1L1T-2 It is of two types
  1. Normal Stress When a deforming force acts normally (perpendicularly) over the area of cross section of a body, then internal restroing force is called normal stress
  2. Tangential or Shearing Stress. When a deforming force acts tangentially to the surface of the body and produces a change in the shape of the body, the stress surface of the body and produces a change in the shape of the body, the stress set up in the body is called tangential or shearing stress
  • Strain. When a deforming force is applied on a body, there is a change in the configuration of the body. The body is said to a deformed.
The ratio of change is configuration to the original configuration, is called Strain Strain is a ration of two similar quantities, so it has no units and dimesions. It is of three types. Mechanical properties of solids
  1. Longitudinal Strain. If there is a change in length alone due to deforming force then strain in the body is called longitudinal stra.
  2. Volumetric Strain. If there is a change in volue due to deforming force, then strain in the body is called volumetric strain.
  3. Shearing Strain. If the deforming force produces a chane in the shape of the body without changing its voluem, the strain is called shearing strain.
Thus, shearing strain is also defined as the ratio of displacement of a surface under a tangential force to the perpendicular distance of the displaced surface from the fixed surface
  • Glass is more elastic than rubber because for a given applied force per uniit area, the strain produced in glass is much smaller than produced in rubber.
  • Water is more elastic than air because the volume of elasticity is reciprocal of compressibility. Further, the air is more compressible than water Mechanical properties of solids

Hooke’s Law (Modulus of Elasticity)

According to this law within the elastic limits, the stress is directly proportinal to the strain produced in a body

i.e. Stress ∝ Strain

or Stress = E x strain ⇒ Stress/Strain = E

Where E is constant of proportionality, it is called modulus of elasticity Hooke’s law is valid only in the linear part of stress-strain curve. There are three types of modulus of elasticity

Young’s Modulus of Elasticity (Y)

The ratio of longitudinal stress and longitudinal strain in the elastic limits, is called Young’s modulus i.e.  Young’s Modulus = Longitudinal Stress/ Longitudinal Strain

Bulk Modulus of Elasticity (B)

The ration of normal stress to the volumetric strain within the elastic limits, is called bulk modulus of elasticity.

i.e. Bulk modulus = Normal stress / volumetric strain

Its SI units is N/m² or pascal and CGS units is dyne/cm²

The negative sign indicates the fact that twith an increase in pressure, a decrease in volume occurs.

Bulk modulus is involved in solids, liquids and gases. Bulk modulus for solids is much larger than that for liquids which is again much larger than the bulk modulus for gases Young’s modulus and bulk modulus for a perfectly rigid body is infinity.

Modulus of Rigidity or Shear Modulus of Elasticity (η)

The ratio of shearing stress to the shearing strain within the elastic limits, is called shear modulus of rigidity.
i.e.,    Modulus of rigidity (η) = Shearing Stress / Shearing Strain
Its SI units is N/m² or pascal and CGS unit is dyne/cm².

 Classification of Materials Based on the Property of Elasticity

Based on the property of elasticity, materials are classified as follows

Ductile Materials

The materials which show large plastic range beyond the elastic limit, are called ductile materials e.g., copper, silver, iron, aluminum, etc.
It is used for making springs and sheets

Brittle Materials

The materials which show very small range beyond the elastic limit, are called brittle materials, e.g., glass, cast iron, etc. Mechanical properties of solids

Elastomers

The materials for which strain produced is much larger than the stress applied within the limit of elasticity, are called elastomers. e.g., rubber, the large vessel carrying blood from the heart, etc.
Elastomers have no plastic range.

Reproduction System

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Reproduction System
Reproduction is the formation of new similar young living organisms by the grown up individuals of a species or race. It is meant for the perpetuation of the race/ species because individuals are bound to die after a life span. Reproduction provides group immortality. Four processes are basic to reproduction— DNA replication, cells division, the formation of reproductive units and development of a new individual. Animal reproduction is of two types, asexual and sexual. Reproduction is the inherent property of the living organisms to continue their race Sby producing offsprings. Reproduction is of two types: (i) Asexual reproduction, (ii) Sexual reproduction

Asexual Reproduction System

The development of new individuals without the fusion of the male and female gamates is known as asexual reproduction. The asexual reproduction usually includes mitotic division of the body (somatic) cells. Therefore it is also known as somatogenic reproduction. The sexual reproduction is common only in lower plants and animals and it is of following types:
  1. Binary fission: In the binary fission, the body splits in such a way that two equal and identical halves are produced. It is most common in protozoans, bacteria, and some lower metazoans.
  2. Budding: In certain multicellular animals, e.g. hydra and fungi the body gives out a small outgrowth known as the bud, the bud is supported by the parent body and it ultimately develops into a new individual.
  3. Gemmule formation: In certain metazoan animals, e.g. fresh water sponges and in some bryophytes such as Marchantia, the asexual reproduction is carried on by certain peculiar asexual bodies known as gemmules, which is composed of a group of undifferentiated cells which contain stored food material.
  4. Spore formation: In many unicellular plants, fungi etc. the asexual reproduction by spore formation is very common under unfavorable conditions. In this process the condensation of protoplasm due to reduction in the water content results. These spores under favorable conditions absorbs water and germinate to form a new plant.
  5. Vegetative reproduction: A fragment or part of the plant grows to produce new plants. Fragmentation is very common in algae and fungi. In higher plants the vegetative propagation takes place in many ways under the following ways:
  • Sucker stem as in mint banana which run horizontally under ground can be separated and grown individually and each is able to develop into separate plant. The vegetative multiplication in the certain storage fleshy leaf like Bryophyllum has also been found very useful.
  • Tubers like potato, when cut into pieces with a bud in each piece and sown each grow into individual tuber plants.
  • Bulbs are also propagated by separating the young bulb eg. Crinum or adventintious ends of the scale leaves eg. Urginea.

Sexual Reproduction

It is a mode of multiplication in which the new individuals or young ones are formed through the process of formation and fusion of gametes. Haploid (gametes)- diploid (individual) attraction occurs. Gametogenesis involves meiosis. Fusion of gametes or fertilization restores the chromosome number. The offspring is produced by growth of the fusion product of gametes called zygote. Sexual reproduction is commonly bi-parental.
  • Exogamy: Sexual reproduction involving gametes from different parents (bi-parental).
  • Unisexual: Organism in which the two sexes occur in different individuals, e.g., humans, mammals, birds, lizards.
  • Bisexual/Hermaphrodite: Organism in which the two types of sex organs (mal and female) occur in the same individual, e.g., Earthworm.

Sexual reproduction in plants

This is a very common type of reproduction in the angiospermic plants. Meiosis (reduction division) occurs in the male and female parts of a flower to form male (pollen grains) and female (ovum) gametes. In order to produce seeds (to reproduce) male and female gametes fuse together to form zygote that divides mitotically and develops into a seed. The process of transference of pollen grains from the another of a flower to the stigma of the same or of different flower is called pollination. It is of two types:

Self-pollination

If the pollen grains are transferred to the stigma of the same flower or between two flowers borne by the same parent then it is self pollination or autogamy.

Cross-pollination

If the pollen-grains are transferred to the stigma of a different flower borne by a different plant then it is called cross-pollination or allogamy. All unisexual flowers are cross pollinated. However, the bisexual flowers also show the following characteristics to favor cross-pollination.

Mammalian Reproduction

Primary Sex Organs: Gonads which form gametes are called primary sex organs — testis (plural testes) in males and ovary (plural ovaries) in females. Testis produces sperms and secretes testosterone (formation and maintenance of secondary sex organs, accessory male glands, and external sex characters). Ovary produces ova. Maturing Graffian follicles secrete estrogens for development and maintenance of secondary sex organs, accessory or external sex characters and part of menstrual cycles. Progesterone produced by ruptured Graffian follicles or corpus luteum controls a part of menstrual cycle, implantation, and development of placenta. Secondary Sex Organs: Sex organs, glands, and ducts which do not produce gametes but are otherwise essential for sexual reproduction are known as secondary sex organs. In human male reproductive system, the secondary sex organs are vasa efferentia, epididymes, vasa deferentia, ejaculatory ducts, seminal vesicles, urethra, prostate glands, Cowper’s glands and penisin. Secondary sex organs of a human female include fallopian tubes, uterus, vagina, external genitalia, Bartholin glands and mammary glands.
Species Life Span (Yrs) Gestation Period (months) Litter No.
Mare 27 11.5 1
Cow 18 9.5 1
Ass 24 12 1
Goat 17 5 1-8
Ewe 13 5 1-3
Sow 14 4 4-6
Bitch 16 2 1-12
Cat 15 2 1-6
Rabbit 5 1 1-13
Accessory/External Sex Characters: They are traits which do not have any direct role in reproduction but provide specific features and structures to the two sexes. The important external/ accessory sex characters of the human male are beard, mustaches, body hair on shoulder and chest, pubic hair on both lateral and vertical directions, comparatively more height with more muscular body, larynx apparent externally, voice low pitched with breathing more by means of diaphragm. The important accessory sex characters of human females are high pitched voice, breast, broader pelvis, lateral pubic hair, rounded body contous with more subcutaneous fat in thighs buttocks and face, and a sternal breathing. Puberty: Beginning of sexual maturity or ability to reproduce is known as puberty. Primary sex organs being functioning. Secondary sex organs develop fully under the influence of sex hormones produced by primary sex organs. Growth is rapid. It is accompanied by the slow development of accessory/ external sexual characters. Puberty occurs at the age of 10-14 years in girls and 13-15 years in boys. Characteristics of Human Reproduction
  1. Human beings are nonseasonal breeders.
  2. There is no oestrus/ heat.
  3. In human females, the ability to produce young ones begins at menarche (beginning of menses) and ends at menopause (stoppage of menses).
  4. In human females, the reproductive phase has 28 days repeated the menstrual cycle.
  5. Fertilization is internal.
  6. There is vivipary. i.e., giving birth to young ones.
  7. The fetus develops inside the uterus and is nourished by a joint special structure called placenta.
  8. Infants can be fed on mother’s milk.
  9. Parental care is very well developed.
  10. Male Genital
Below the bladder and between the legs the plum sized testes and expandable sausage-like penis exist which make and deliver sperm into a woman.
  • Sperm and male sex hormones are made in two plum sized glands called the testes.
  • The testes lie in a sac called the scrotum that hangs outside the body, between the legs. This arrangement maintains sperm at a temperature slightly below body temperature, which is essential for the production of healthy sperm.
  • Each testis has a long highly coiled tube attached to it known as an epididymis. Immature sperm passes out of the testes into the epididymis. As sperm make their way through these tubes, they mature and learn to swim. Maturation takes between one and three weeks, after which they are either ejaculated out of the body or reabsorbed into the body.
  • Every day a man makes between 50 and 500 million sperm.
  • Sperm and urine both leave the body through a tube called the urethra that runs down the middle of the penis.
  • Semen is a milky white, sticky mixture of sperm and fluid secretions. It provides nutrients to energize sperm and acts as a transport medium to carry sperm through the penis, out of the body and into a woman’s vagina.
  • During ejaculation, sperm is propelled from the epididymis along a duct called the vas deferens. This carries sperm upwards, out of the scrotum, towards the penis.
  • En route, fluids from the seminal vesicles (the small red glands at the end of the vas deferens) and the prostate gland dilute the sperm. These fluids provide the optimal environment for sperm to swim and survive in the acidic conditions of the female reproductive tract.
  • During ejaculation, a man produces between two and five milliliters of semen that contains between 50 and 130 million sperm per milliliter.
  • The tiny bulbourethral glands secrete a thick, clear mucus that drains into the urethra. It cleans the urethra before ejaculation and acts as a lubricant during sex.

Female Genital

Behind the bladder there is uterus, or womb, the size of an upside-down pear which produces eggs, have sex, carry a developing baby and to give birth.
  • The female genitals consist of two glands called ovaries that are responsible for producing eggs and female sex hormones.
  • Once women reach sexual maturity, they experience a hormone regulated monthly fertility cycle known as a menstrual cycle. These hormones control the maturation and release of an egg from one of the ovaries every month, and they affect the lining of the womb making it ready to receive a fertilized egg.
  • Mature eggs are released from the ovary and move along the fallopian tube to the uterus. If an egg is fertilized, it tries to embed itself in the uterus wall, ready to develop into a foetus. If no egg becomes implanted, the uterus lining is shed, and this results in a flow of menstrual blood, known as the ‘period’.
  • When a baby girl is born, she already carries all the eggs that she will ever produce through her life. A boy, however, does not carry sperm at birth, and only begins to produce sperm when he reaches sexual maturity.

Menstrual Cycle

It is a series of cyclic changes that occur in the reproductive tract of human females and other primates with a periodicity of 28 days, right from menarche to menopause. It is characterised by menses or loss of blood for a few dyas. Menstrual cycles consists of the following phases.

Menstrual Phase

It is the phase of menstrual flow menses which continues for 3-5 days and involves the discharge of blood (a total of 50-100 ml). Menstrual phase is also called funeral of unfertilized egg or shedding tears of lost ovum. The first day of menstrual phase is also considered to be first day menstrual cycle.

Post-Menstrual/Follicular Phase

Anterior pituitary secretes FSH which stimulates follicular cells of Graafian follicle to secrete estrogen Recovery Phase. It last for 2 days and brings about repair of ruptured blood vessels and mucous lining or endometrium of reproductive tract. Proliferative Phase. The endometrial lining begins to thicken, especially that of uterus. There is development of blood capillaries, elongation, and coiling of uterine glands, greater activity of uterine muscles thickening and development of more cilia in the epithelial lining of fallopian tubes.

Fertility Phase/Ovulation

Production of FSH decreases while that of LH increases. Presence of both FSH and LH causes ovulation. The ovum is drawn into the fallopian tube. It is viable for two days when fertilization can occur. Ovulation takes place between 10-14 days (fertility period 10-16 days of menstrual cycle).

Pre-Menstruation/Luteal/Secretory Phase:

It operates under the influence of progesterone produced by corpus luteum (empty proliferated Graafian follicle and supervised by LH of the anterior pituitary. Endomitrial lining thickens and its glands become secretary. Uterine movements are reduced. The stage is meant for receiving fertilized ovum. In the absence of fertilization, corpus lutem degenerates. LH level falls. Progesterone level is reduced. Reduced level of both progesterone and estrogen causes menses.

Estrous Cycle

It is a series of cyclic changes that occur in the reproductive tract of nonprimate mammalian females with variable periodicity in different animals. There is a period of estrous or heat near the time of ovulation due to rising level of estrogen. It lasts for only 18 hours in cow. The female receives the male only during estrous or heat. There is generally specific period of oestrous (= estrous, except for domesticated mammals), may be two (spring and autumn for bitches), called breeding seasons. In case of no fertilization, the endometrial breakdown is not accompanied by rupturing of blood vessels. Hence, there is no bleeding.

what is a virus

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what is a virus

What is Virus

The viruses are the simplest forms of life which instead of having the cellular organization (viz. plasma membrane, cytoplasm, and nucleus) similar to bacteria, blue-green algae, plants and animal, contain definite genetically determined macromolecular organization, genetic material and characteristic mode of inheritance.

Who discovered the virus? When Virus Discovered?

The viruses were first discovered by Iwanowski (1892) as extremely small micro organisms.

Virus Structure

The viruses are sub-microscopic, acellular, forms of life and are much smaller than bacteria. They range in size from 20 to 80 m. Iwanowski showed that mosaic disease in the leaves of tobacco is caused by the ultramicroscopic agents that can pass even through the pores of fine filter paper which did not allow even bacterial cells to pass through. The viruses possess a regular geometrical and macromolecular organization. Basically, all viruses consist of a core of only one type of nucleic acid (DNA/ RNA) which remains wrapped in a coat of protein called capsid. The capsid is composed of numerous protein molecules called capsomeres. The capsomeres determine the shape of the virus particle or viron, thus the viruses may contain three types of symmetry such as cubic (eg Bacteriophase x 174, Turnip yellow mosaic virus, etc.) Helical (eg Potato spindle tuber virus) have no capsid around the nucleic acid core or viral chromosomes. There are some highly specialized viruses such as influenza virus and mumps containing a membranous envelope around the capsid.

How does Virus work?

Viruses contain only one kind of nucleic acid as the hereditary material. The DNA viruses have single DNA molecule which may be either linear (having free and) or circular (having no free end) in shape, mostly, the linear DNA molecule is double stranded (eg P 22 bacteriophage). The circular DNA molecule may be either single stranded (eg x 174 bacteriophages) or double stranded as in most animal viruses. The RNA viruses are the only biological systems known in which RNA is the genetic material mostly, the RNA is present in its usual single stranded form (eg Plant viruses, Influenza etc.) but some viruses such as Retrovirus have a core of double stranded RNA similar in properties to DNA.

Why is virus host specific?

The viruses lack in necessary energy yielding and synthetic enzyme systems. Therefore, they cannot lead a free living mode of life for the performance of fundamental life activities such as reproduction, genetically determined structures and functions, they have to lead a parasitic mode of existence. All viruses are, therefore, invariably intercellular parasites of specific hosts which may be bacteria plants, or animals. The viruses may be classified into following 3 groups according to the type of host:

Types of Viruses

Bacterial viruses or Bacteriophages

Viruses that parasitize bacterial cells are called bacteriophages. At the time of infection of T4 bacteriophage, a phage becomes anchored to the bacterial cell wall by its tail fibers. An enzyme at the core of the tail of the phage digests the part of the bacterial cell wall so as to produce a hole and finally, the phage DNA is injected into the bacterial cell.

Plant Viruses

The plant viruses parasitize the plant cells and disturb their metabolism and cause severe disease in them. All plant viruses consist of ribonucleoproteins in their organization. Some of the important plant viruses are tobacco mosaic virus (TMV) potato virus, and turnip yellow viruses (TYV).

Animal Viruses

They infect the animal cells and cause different diseases in animals and human beings. Generally, they have a spherical shape and genetic material in the form of DNA and sometimes RNA. The capsid of animal viruses is surrounded by an envelope. Some of them are Small pox virus, Influenza virus, mumps, pea virus etc. Poliomyelitis is an extensively studied animal virus which has got RNA as its genetic material

Disease caused by Virus in Human

Disease Causative Pathogen Mode of transmission Incubation
Small Pox Variola Virus Direct contact (droplets), Indirected by infected articles 12 days
Chicken Pox Varicella Virus Direct contact (droplets), Indirect by Infected object 12-16 days
Common Cold Rhinovirus Contact 2-5 days
Influenza /Flu Orthomixo-virus Contact, Virus transmitted through discharge from respiratory tracts of persons infected with disease 1-2 days
Measles Measles virus (Paramyxo virus) Direct contact, virus transmitted through air by droplets during talking Coughing and sneezing 10-14 days
Mumps Mumps virus Direct contct, virus in Saliva and Secretin of nose invades salivary glands 12-21 days
Viral encephalitis Encephalitis virus (arbovirus) Some domestic animals reservoir of virus, transmitted by mosquito bite to man 4-21 days
Poliomylitis Poliovirus Contact, housflies, fleas, food and water 7-14 days
Rabies Rabies virus Bite of a mad (Rabid) dog 2-16 days
Dengue fever Dengue virus Mosquito (Aedes) bite 4-8 days
Herpes simplex Herpes virus simplex Contact, Saliva, stools, contaminated articles
Herpes Zoster Herpes virus zoster Contact droplets 7-14 days
Acquired immuno Deficiency Syndrome (AIDS) Human T-cell Leukemia Virus (HTLV-III); also called LAV Via blood and sperm among homosexuals, heterosexuals, intravenous drug users, hemophiliacs, promiscuous individuals and prosititutes 2 months to 10 years

What is Algae

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What is Algae

What is Algae?

Algae are used by man in a great many ways. Because many species are aquatic and microscopic, they are cultured in clear tanks or ponds and either harvested or used to treat effluents pumped through the ponds. Food Stuff: Algaculture on a large scale is an important type of aquaculture today. Certain species are edible like red dulse, which is dried and marketed in Ireland. It is eaten raw, fresh or dried, or cooked like spinach. Porphyra, commonly known as purple laver, is also collected and used as “laver bread” and jelly in UK. Chondrus crispus, common name: Irish moss, is also used as carrageen for the stiffening of milk and dairy products, such as ice-cream. Ulva lactuca, common name: sea lettuce, is used locally in Scotland where it is added to soups or used in salads.

Uses of Algae

Algae Used as a Fertilizer:

For centuries seaweed has been used as manure. There are also commercial uses of algae as agar. Maerl is harvested as fertilizer of organic gardening. Chemical analysis of maerl showed that it contained 32.1% CaCO 3 and 3.1% MgCO 3 (dry weight).

Algae uses as an Energy Source:

Algae can be used to make biodiesel, and by some estimates can produce vastly superior amounts of oil, compared to terrestrial crops grown for the same purpose. Because algae grown to produce biodiesel does not need to meet the requirements of a food crop, it is much cheaper to produce. Also, it does not need fresh water or fertilizer. Algae like Chlamydomonas reinhardtii (a green- algae) can be grown to produce hydrogen. Algae can be grown to produce biomass, which can be burned to produce heat and electricity.

Algae used in Pollution Control

Algae are used in wastewater treatment facilities, reducing the need for more dangerous chemicals. Algae can be used to capture fertilizers in runoff from farms and if this alga is then harvested, it itself can be used as fertilizer. Algae bioreactors are used by some power plants to reduce CO 2 emissions. The CO 2 can be pumped into a pond, or some kind of tank, on which the algae feed. Alternatively, the bioreactor can be installed directly on top of a smokestack.

Nutritional Value of Algae

Algae is commercially cultivated as a nutritional supplement. One of the most popular micro algal species is Spirulina, which is a Cyanobacteria (known as blue-green algae). Other algal species cultivated for their nutritional value include; Chlorella (green algae), and Dunaliella (Dunaliella salina), which is high in beta-carotene and is used in vitamin C supplements. Algae is sometimes also used as a food, as in the Chinese vegetable known as fatchoy (which is actually a cyanobacterium). The oil from some algae has high levels of unsaturated fatty acids. Arachidonic acid (a polyunsaturated fatty acid), is very high in Parietochloris incisa, (a green alga) where it reaches up to 47% of the triglyceride pool.

Dyes & Pigments produced from algae

The natural pigments produced by algae can be used as an alternative to chemical dyes and coloring agents. Many of the paper products used today are not recyclable because of the chemical inks that they use but inks made from algae are much easier to break down. There is also much interest in the food industry into replacing the coloring agents that are currently used with coloring derived from algal pigments.
  • Blue-Green Algae (Moneran): They contain a blue pigment phycocyanin in addition to chlorophyll and other pigments. Only asexual reproduction occurs among them. They contaminate drinking water, causing very disagreeable odor and taste. They bring about the reddish color of the Red Sea, used as soil fertilizer. Some species thrive in the digestive tract of human without causing ill effects. Some members – Gloeocapsa and Nostoc have formed a partnership with fungi, making up the separate group of organism known as lichens.
  • Euglena : Found in stagnant ponds, swimming pools, aquariums, water become greenish, unpleasant flavor.
  • Green Algae: Self-food maker, add O 2 to water available for fish and other organisms, also serve food for these creatures. They often cause water pollution in lakes, tanks etc. may cause unpleasant flavors and odors, their respiration may lower the O 2 content of the water. So the fish in this area may die of suffocation (CuSO 4 can eradicate unwanted green algae). Spirogyra – B.G. Algae
  • Brown Algae : (brown pigment fucoxanthin): They are marine plants and are the source of food for fish and others- It is the major source of Alginic acid. By removing from sea can be used as cattle feed. Some species yield Iodine, some make excellent fertilizers. Kelps – B. Algae include the largest member of the group. Macyosist Pyrifera- giant kelp, longest plant of world (30 mt. or more). Gulfweed or sargassum – B. Algae in Saragossa sea (West Indies to Azores).
  • Diatoms (yellowish green to yellowish brown): They have cell-wall, contain silica and are harmless to man. They often make up the bulk of the plankton as sea animal food. It serves as filter and clarifies many liquids. They are excellent insulating material for boilers, blast furnaces refrigerators and are used as a milk abrasive in polishes and scouring powders
  • Red Algae : (red, brown and violet): They are multicellular and generally used as food for sea animals and fish, as food for human (in Europe and Far East). Irish moss is also used for curing leather and for shoe polish and creams and shampoos. Ceylon moss yields a gelatinous material known as agar-agar, observe a great deal of water, used by researchers as growth material for bacteria, also serves to thicken soups and broths, as a sizing material for textiles, as a mild laxative, to provide body for puddings, pastries, ice-creams, etc. Some algae secrete lime so they have helped to build coral reefs (dating back to Ordovician times).

Ecological Role of Algae

Although often inconspicuous, fungi occur in every environment on Earth and play very important roles in most ecosystems. Along with bacteria, fungi are the major decomposers in most terrestrial and some aquatic ecosystems, and therefore play a critical role in biogeochemical cycles and in many food webs. Many fungi are important as partners in symbiotic relationships with other organisms, as mutualists, parasites, or commensalism, as well as in symbiotic relationships that do not fall neatly into any of these categories. One of the most critically important of these relationships is various types of mycorrhiza, which is a kind of mutualistic relationship between fungi and plants, in which the plant’s roots are closely associated with fungal hyphae and other structures. The plant donates to the fungus sugars and other carbohydrates that it manufactures from photosynthesis, while the fungus donates water and mineral nutrients that the hyphal network is able to find much more efficiently than the plant roots alone can, particularly phosphorus. The fungi also protect against diseases and pathogens and provide other benefits to the plant. Recently, plants have been found to use mycorrhizas to deliver carbohydrates and other nutrients to other plants in the same community and in some cases can make plant species that would. Lichens are formed by a symbiotic relationship between algae or cyanobacteria and fungi, in which individual photobiont cells are embedded in a complex of fungal tissues. As in mycorrhizas, the photobiont provides sugars and other carbohydrates while the fungus provides minerals and water. The functions of both symbiotic organisms are so closely intertwined that they function almost as a single organism. Certain insects also engage in mutualistic relationships with various types of fungi. Several groups of ants cultivate various fungi in the Agaricales as their primary food source, while ambrosia beetles cultivate various kinds of fungi in the bark of trees that they infest. Some fungi are parasites of plants, animals (including humans), and even other fungi. Pathogenic fungi are responsible for numerous diseases, such as athlete’s foot and ringworm in humans and Dutch elm disease in plants. Some fungi are predators of nematodes, which they capture using an array of devices such as constricting rings or adhesive nets. Some fungi are parasites of plants, animals (including humans), and even other fungi. Pathogenic fungi are responsible for numerous diseases, such as athlete’s foot and ringworm in humans and Dutch elm disease in plants. Some fungi are predators of nematodes, which they capture using an array of devices such as constricting rings or adhesive nets.

What is fungi

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What is fungi

What is Fungi?

Fungi have a long history of use by humans. Many types of mushrooms and other fungi are eaten, including button mushrooms, shiitake mushrooms, and oyster mushrooms. Of course, many species of mushrooms are poisonous and are responsible for numerous cases of sickness and death every year. A type of single-celled fungus called yeast is used in baking bread and fermenting alcoholic beverages, while mycelial fungus is used to make Shoyu (soya sauce) and tempeh. Fungi are also used to produce industrial chemicals like lactic acid, antibiotics and even to make stonewashed jeans. Some types of fungi are ingested for their psychedelic properties, both recreationally and religiously. Edible and Poisonous Fungi Some of the most well-known types of fungi are the edible and poisonous mushrooms. Many species are commercially raised, but others must be harvested from the wild. Button mushrooms are the most commonly eaten species, used in salads, soups, and many other dishes. Portobello mushrooms are the same

Edible and Poisonous Fungi

Some of the most well-known types of fungi are the edible and poisonous mushrooms. Many species are commercially raised, but others must be harvested from the wild. Button mushrooms are the most commonly eaten species, used in salads, soups, and many other dishes. Portobello mushrooms are the same Some of the most well-known types of fungi are the edible and poisonous mushrooms. Many species are commercially raised, but others must be harvested from the wild. Button mushrooms are the most commonly eaten species, used in salads, soups, and many other dishes. Portobello mushrooms are the same species, but are allowed to grow to a much larger size. Other commercially-grown mushrooms that have gained in popularity in the West and are often available fresh in grocery stores include straw mushrooms (Volvariella volvacea), oyster mushrooms (Pleurotus ostreatus), shiitakes (Lentinula edodes), and enokitake (Flammulina spp.). There are many more mushroom species that are harvested from the wild for personal consumption or commercial sale. Milk mushrooms, morels, chanterelles, truffles, black trumpets, and porcini mushrooms (also known as king boletes) all command a high price in the market. They are often used in gourmet dishes. It is also a common practice to permit the growth of specific species of mold in certain types of cheeses that give them their unique There are many more mushroom species that are harvested from the wild for personal consumption or commercial sale. Milk mushrooms, morels, chanterelles, truffles, black trumpets, and porcini mushrooms (also known as king boletes) all command a high price in the market. They are often used in gourmet dishes. It is also a common practice to permit the growth of specific species of mold in certain types of cheeses that give them their unique It is also a common practice to permit the growth of specific species of mold in certain types of cheeses that give them their unique flavour. This mold is non-toxic and is safe for human consumption. This accounts for the blue colour in cheese such as Roquefort or Stilton. Hundreds of mushroom species are toxic to humans, causing anything from upset stomachs to hallucinations to death. Some of the most deadly belong to the genus Amanita. Stomach cramps, vomiting, and diarrhea usually occur within 6-24 hours after ingestion of these mushrooms, followed by a brief period of remission, usually 1-2 days. Patients often fail to present themselves for treatment at this time, assuming that they have recovered. However, within 2-4 weeks liver and kidney failure Hundreds of mushroom species are toxic to humans, causing anything from upset stomachs to hallucinations to death. Some of the most deadly belong to the genus Amanita. Stomach cramps, vomiting, and diarrhea usually occur within 6-24 hours after ingestion of these mushrooms, followed by a brief period of remission, usually 1-2 days. Patients often fail to present themselves for treatment at this time, assuming that they have recovered. However, within 2-4 weeks liver and kidney failure leads to death if untreated. There is no antidote for the toxins in these mushrooms, but kidney dialysis and administration of corticosteroids may help. Fly agaric mushrooms are also responsible for a large number of poisonings, but these cases rarely result in death.

Fungi in Biological Control of Pests

Many fungi compete with other organisms, or directly infect them. Some of these fungi are considered beneficial because they can restrict, and sometimes eliminate, the populations of noxious organisms like pests, insects, mites, weeds, nematodes and other fungi, such as those that kill plants. There is much interest on the manipulation of these beneficial fungi for the biological control of pests. Some of these fungi can be used as biopesticides, like the ones that kill insects (entomopathogenic fungi). Specific examples of fungi that have been developed as bioinsecticides are Beauveria bassiana, Metarhizium anisopliae, Hirsutella, Paecilomyces fumosoroseus, and Verticillium lecanii. In

Fungi Kingdom

  • Mycorrhizal (fungus root): some fungus invades the roots of the plant but instead of harming the seed plants it helps them by assisting in transporting water and minerals from the soils to the roots of the plant. The seed plant, in turn, supplies food to fungi. Fungi of this kind are called Mycorrhizal. A good example of symbiosis.
  • Downy mildews: They produce a downy growth on the surface of infected plant parts usually on leaves. One of the best known downy mildews is the late blight of potatoes. They also cause other plant diseases, they attack tobacco, cabbage, cucumbers, etc.
  • Black bread mold group: usually called mucous. Most of them occurs as fluffy growth on bread, fruits, vegetables and preserved food. They are white at first but soon becomes dark as their spores mature in large number. It develops on bread.
  • Yeast: Occurs wherever simple sugars are available like on fruits, in the sap from trees, in soil (particularly in orchards and vine yards).
  • Brewer’s Yeast: has been bred for high alcoholic fermentation; used in making beer, liquors, commercial alcohol.
  • Baker’s Yeast: is placed in bread dough, it causes the dough to ‘rise’ or expand by producing CO 2.
  • Candida Albicans: responsible for thrush, a disease of mouth and throat.
  • Blue and Green Moulds Group: Aspergillus, ( the primary source of citric acid, used in flavoring candies & fruits) Penicillium (used for antibiotics).
  • Powdery Mildews: as powdery white substance on leaves. They are plant parasites, causes disease of crop plants and ornamentals, including grape, apple, rose, etc.
  • Rusts and Smuts: parasitic, attack higher plants. Most common species is wheat barberry rust.
  • Mushrooms and Toadstools: The first is edible while the second one is poisonous.
  • Imperfect fungi: from the class ‘Deuteromycotina’, parasitic. They are often very destructive to crop and ornamental plants and causes disease in human beings, responsible for ringworm.
  • Lichens : a combination of fungus and an algae; symbiosis; through photosynthesis the algae manufactures all the organic food that they both require. The fungus brings in water and minerals and offers protection to the algae. Certain kinds of lichens yields litmus a dye used as chemical indicators.
  • Yeasts: one celled are eukaryotic micro-organisms classified in the Kingdom Fungi. Most reproduce asexually by mitosis and also by budding. Used in baking bread and alcoholic beverages.
  • Mushrooms: the complex is the fleshy, spore bearing fruiting body of a fungus. Are neither angiosperms or gymnosperms and do not undergo photosynthesis. Edible mushrooms are consumed by humans for their nutritioned and medicinal value and are cultivated.

Human Endocrine System

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Human Endocrine System
Chemical coordination the body includes endocrine glands, their hormones and their mode of action. The chemical coordination is performed by a system known as the endocrine system (Human endocrine System).

Glands (Human Endocrine System)

A gland is an organ which synthesizes some substances and secretes them at various locations e.g., sweat glands secrete sweat, endocrine gland secretes hormones like growth hormone, etc.

Types of glands

In vertebrates, glands may be classified on the basis of presence or absence of ducts. These are called exocrine and endocrine glands.

Difference between Exocrine and Endocrine Glands

Exocrine Glands Endocrine Glands
These are glands with ducts These are ductless glands or glands of internal Secretions
The secretions of these glands are carried by ducts to a particular organ for some metabolic activities, e.g., salivary glands, liver, etc These glands have no ducts and their secretions (hormones) get absorbed into the immediate surrounding blood circulation to reach the target (specific) organs to initiate a particular metabolic change, e.g., thyroid, parathyroid, adrenals, etc.
 

Hormones

These are the non-nutrient chemical made up of amino acid derivatives, peptides and steroids etc., that are secreted by endocrine glands in response to change in external or internal environment. They act as intercellular messengers that regulate the biological processes in organisms and are produced in trace amounts. Ernest H starling coined the term hormone in 1905. The first hormone was discovered by the English physiologist William M bayliss and Ernest H starling in 1903.

Characteristics of Hormones

  • Hormone releases directly into the blood and circulates in the body for performing regulatory functions.
  • It is always released out in very small amount
  • It regulates various functions in the body like growth and development, behavioral characters, sexual characters, reproductive activities, metabolic activities etc.
  • It also helps in maintaining body balance.
The human endocrine system includes the endocrine glands and hormones produced by diffused tissues or cells located in different parts of the body. It includes the following organs for the purpose of secretion Endocrine Glands Thyroid, parathyroid, adrenal, pituitary, thymus, and pineal. Mixed Glands Pancreas Other Structures include hypothalamus, skin, gastrointestinal mucosa, heart, kidneys, gonads (ovaries in woman and testes in men), placenta and liver.

Types of Pituitary Glands

Gland Hormone Type Action
Posterior Oxytocin Antidiuretic hormone Peptide Initiate labor and milk ejection
Antidiuretic hormone Peptide Stimulates water resorption by kidneys
Anterior Growth hormone Protein Stimulates body growth
Prolactin Protein Promotes lactation
Follicle-stimulating homorne Glycoprotein Stimulates follicle maturation and production of estrogen
Luteinising hormone Glycoprotein Triggers ovulation and production of estrogen and progesterone by ovary
Adrenocorticotropic hormone Peptide Promotes release of glucocorticoid and androgens from adrenal cortex
Thyroid-stimulating hormone Glycoprotein Stimulates release of T3 and T4
Thyroid gland T3 (Triiodothyronine) Amine Increase metabolism, blood pressure and regulates tissue growth
T4 (Thyroxine) Amine Increase metabolism, blood pressure and regulates tissue growth
Calcitonin Peptide Childhood regulation of blood calcium levels through uptake by bone
Parathyroid hormone Peptide Increse blood calcium levels through action on bone, kidneys, and intestine
Pancreas Insulin Protein Reduces blood sugar levels by regulating cell uptake
Glucagon Protein Increases blood sugar levels
 

Types of Adrenal Glands

Gland Hormone Type Action
Adrenal medulla Epinephrine Amine Short-term stress response: increased blood sugar levels, vasoconstriction, increased heart rate and blood divination
Norepinephrine Amine Short-term stress response increased blood glucose levels; blood volume maintenance and immune suppression
Adrenal cortex Glucocorticoids Steroid Long-term stress response; Increased blood glucose levels, blood volume maintenance, immune and suppression
Mineralocorticoids Steroid Long term stress response, blood volume and pressure maintenance, sodium and water retention by kidneys
Pineal gland Melatonin Amine Circadian Timing
Thymus Thymosis Peptide Development of T-lymphocytes
 

Types of Gonads

Gland Hormone Type Action
Testes Androgens Steroid Reproduction maturation and sperm production
Ovaries Estrogens Steroid Reproduction maturation and regulation of menstrual cycle
Progesterone Steroid Regulation of menstrual cycle
  • The study of endocrine glands and hormones secreted by them is called endocrinology.
  • The first hormone to be discovered was secretin but the first hormone to be isolated was insulin by Banting and McLeod
  • Hypothalamus is considered as supreme commander of human endocrine system
  • Pituitary gland was considered as master gland of the body but today it is considered as Orchestra of Human endocrine system
  • The pituitary gland is the smallest endocrine gland in the human body.
  • Thyroid gland is the largest endocrine gland in the human body

Disorders of Human Endocrine System

  1. Dwarfism. It occurs due to deficiency of Growth Hormone (GH) secretions during childhood. Growth of long bones and body stop prematurely making person dwarf.
  2. GIgantism It occurs when large quantities of growth hormone is secreted during childhood resulting in person with abnormal height and very long bones.
  3. Acromegaly If an acidophilic tumor occurs causing high GH secretion after adolescence, it results in acromegaly in which jaws and limbs become abnormally large bu the body do not attain giant structure.
  4. Cretinism It is caused due to the hyposecretion of thyroid hormone in infants. This leads to slow heart beat, lower blood pressure, low body temperature, stunted growth, mental retartdation, retarded sexual development.
  5. Addison’s disease It is caused by deficiency of mineralocorticoids and glucocorticoids
  6. Cushing’s Syndrome It is caused by excess of cortisol which may result in high blood sugar, obesity, rise in blood volume and pressure.
  7. Aldosteronism It is caused by dexcessive production of aldosterone from adrenal contical tumours.
  8. Adrenal virilism It is the appearance of male characters in female, which result in beard, moustaches, etc. It is caused due to excessive production of male sex corticoids (androgen) in females.
  9. Gynecomastia It is the development of enlarged mammary glands (breasts) in males due to excessive secretion of female sex hormones (estrogen) in males.
  10. Precocious Puberty It is early maturation of ovaries and testes with the production of ova before the age of 9 years in girls or sperms before 10 years in boys, called sexual pseudo precocity.
  11. Eunuchoidism It is a disorder which affects males due to failure of testosterone secretion. A eunuch has under developed and non-functional secondary sex organs lacks external or accessory sex characters and does not produce sperms.

Education isn’t a commodity for labor

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Education isn’t a commodity for labor
Steven Fesmire, Middlebury College When it comes to current debates in politics and policy, even a strident defense of the liberal arts – such as George Anders’s “You Can Do Anything: The Surprising Power of a ‘Useless’ Liberal Arts Education” or Randall Stross’s “A Practical Education: Why Liberal Arts Majors Make Great Employees” – tends to accept that gainful employment is the chief aim of education. As a specialist in the 20th-century philosopher and educator John Dewey, I’ve been watching these debates with interest. The most-cited academic philosopher of the 20th century, Dewey made, arguably, the past century’s most significant contributions to the development of educational thinking. Among other things, he influentially criticized education conceived as “mere preparation for later life.” Looking back to Dewey raises pertinent questions about education’s fundamental mission today. Is the principal aim of education to provide a padded yoke for the state’s preexisting workforce? Or is it, all things considered, to improve our lives?

The purpose of education

In the 19th century, women’s rights advocate Margaret Fuller admonished the practice of educating girls just to be wives and mothers. “A being of infinite scope,” she wrote, “must not be treated with an exclusive view to any one relation. Give the soul free course… and the being will be fit for any and every relation to which it may be called.” In my view, educational policy in the United States today is entangled in a practice as constrictive as the one Fuller criticized more than 150 years ago. For many, the mission of K-12 and higher education is, in Wisconsin Gov. Scott Walker’s infamous words, “to develop human resources to meet the state’s workforce needs.” Whatever one may think of Walker’s politics, his general outlook is no outlier. It typifies the view that education is mostly a way to fuel industry with skilled labor – and it’s in tension with the goal of preparing students for “any and every relation to which [they] may be called.” Rather than educating whole persons for lifelong growth, this “industrial model” treats education as just another sector of the economy. In this view, education’s job is to manufacture skilled labor, and it’s expected to do so in a way that’s maximally efficient. Knowledge is seen as a market commodity, teachers and professors are delivery vehicles for knowledge content and students are either consumers or manufactured products. Educational institutions that follow the industrial model are seen as marketplaces for acquiring and delivering content. And when tuition is involved, that’s simply the fair price for accessing that content.

What does society lose?

When described in this way, it seems a cold, inhuman approach to education. Nevertheless, both major U.S. political parties seem to have embraced the industrial model. The parties may substantively disagree on the particulars of how to provide education, but (in the main) noneconomic values are too often not on the radar. I contend that something is indeed lost when we treat education as nothing but a sector of the industrial economy. First, the industrial model deepens our social problems. It’s true that many specific goals of education are, and should be, defined by our economic infrastructure – such as the demand for a curricular emphasis on STEM. But that doesn’t mean that our primary educational aim must revolve around this. Training students exclusively to fit existing specifications not only stifles imagination and innovation, but also directs students down the very channels that are implicated in our social, economic, environmental and geopolitical problems. I believe this sacrifices our best hope for making things better.
Philosopher John Dewey believed that students who were trained to be fed into an existing structure wouldn’t help that structure evolve. Library of Congress
And so we come to John Dewey. As a child, he regularly did chores on his grandfather’s farm outside Burlington, Vermont. He later lamented that such productive occupational supplements to formal education were mostly eclipsed by urbanization and mechanization. He sought ways to bring practical life into the classroom so that schooling could speak to living. But there is an important distinction to be made. In one approach, you may infuse education with content that speaks to potential careers – so-called “real life.” On the other hand, you might allow the existing economic infrastructure to be the singular driving force behind educational practice. The latter, in the words of Dewey, turns students and teachers into “instrument[s] in accomplishing the feudal dogma of social predestination.” The former is what most educators themselves hope for: students who become participants in the intelligent redirection of society.

Cultures of imagination, growth and fulfillment

Not only does the industrial model of education dampen intelligent social action, but it also sacrifices personal enrichment. An educational institution is capable of training more students with fewer or lower-paid teachers or professors – just as an industrial sector can produce more clothes, cars or animal protein to meet market demands with lower overhead costs. These products can then be purchased at a relatively low price and used for, or put to work to produce, more things. But what else do we unintentionally produce when education – or industry, for that matter – is made “efficient” in this way? For instance, do we make narrower lives? Do we, in Dewey’s words, make life more “congested, hurried, confused, and extravagant”? As seen through a narrowly utilitarian-industrial lens, it’s simply not clear how education might address personal growth, community and quality of life. If unaddressed, I believe we risk marginalizing these aspects of individual enrichment.
Education is about more than churning out worker bees. Personal enrichment is a vital component as well. Stephanie, CC BY

Democracy and education

Democracy, Dewey urged, is not a static inheritance that we can simply live off of, but an ideal that every generation must re-achieve through active effort. Schools are our chief cultural means for educating free citizens who can intelligently and creatively participate in this effort. Education is how we invest in the future of our democracy. Under today’s economic and social conditions, what does it mean if “education for the state’s workforce” is the chief mission of schools? Does it sacrifice the quality of a student’s present life for the sake of a promised good? Does it support a frozen system of privilege, frantic and unsustainable consumption and deadening efficiency? The ConversationDewey argued, in opposition, that everyone should have the ongoing opportunity for a critically reflective and occupation-rich education that emphasizes growth, emotional development, imaginative engagement, aesthetic vitality, social responsibility and care. From K-12 to university, such an education can help to establish conditions for personal enrichment, critical inquiry and democratic participation. Steven Fesmire, Visiting Professor of Philosophy, Middlebury College This article was originally published on The Conversation. Read the original article.

What is Metamorphism in Geology | Geology Notes

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What is Metamorphism in Geology | Geology Notes

What is Metamorphism?

Metamorphism is the mineralogical and structural adjustment of solid rocks to physical and chemical conditions which have been imposed at depths below the surface zones of weathering and cementation, and which differ from the conditions under which the rocks in question originated. Thus metamorphism is the response of the solid rocks to pronounced changes of temperature, pressure and chemical environment.

What happens when metamorphism takes place?

Metamorphism stands midway between diagenesis and general melting of rocks. Important features of metamorphic changes: i) The bulk chemical composition of the metamorphic rock is the same as that of the rock from which it formed. Thus metamorphic changes are isochemical changes. ii) The structural and textural characteristics of the metamorphic rocks are the outcome of the structure and texture of the pre-existing rocks and the temperature-pressure condition of the metamorphic changes. iii) The changes in metamorphism take place is an essentially solid medium.

Metamorphism occurs for which class of rocks?

Metamorphic rocks which are derived from igneous rocks are known as Orthometamorphic rock, and those which are derived from the sedimentary rocks, are known as para metamorphic rocks.

Which agent of metamorphism can cause?

The agents which are mostly responsible for  bringing about metamorphic changes are as follows:

Temperature – Metamorphism

It may be supplied by geothermal gradient, magmatic heat, frictional heat and by radioactive disintegration. The temperature range within which metamorphic changes take place is from 200 to 700 degree C. However, in certain cases, a temperature of 1000 to 1200 degree C may be encountered. Temperature accelerates the process of reaction, increases the volume of the rocks, remove volatiles and moisture contents of the rocks. The following types of metamorphism are said to be the result of temperature effect on rocks.

Metamorphism occurs at temperatures between

i) Pyrometamorphism. At 800 to 1000 degree C, in the immediate vicinity of intrusives. The induration, backing, burning and fritting effects of lava flows and intrusions on neighboring rocks is known as Caustic metamorphism or optalic metamorphism. ii) Contact metamorphism. It occurs around larger intrusives at comparatively low temperature. it includes: a) Normal contact Metamorphism. Where rocks are simply crystallized without new mineral formation. b) Pneumatolytic, additive or metasomatic. The composition of the rocks is vastly modified depending on the addition of material from magmatic emanations. c) Injection metamorphism. Here with the intrusion of magma or its residual liquid may alter the intruded rock substantially. iii) Auto metamorphism. It is the mineralogic readjustment of an igneous assemblage to the falling temperature as the body of the igneous rock cools. It includes uralitization, serpentinization etc. iv) Retrograde metamorphism. Also known as diaphoresis, where mineralogical rearrangement of high-temperature assemblage to a low-temperature one take place.

Metamorphism due to pressure

a) Uniform pressure. It is the hydrostatic pressure which increases with depth. Uniform pressure and temperature can both dominate together at great depths. there is a reduction in the volume of the rock and a change in the mineralogical composition. It is known as Plutonic Metamorphism, e.g., Granulites, Eclogites. Load Metamorphism. It is due to the vertically acting stress of superincumbent rock masses aided by high temperature. b) Directed pressure. It is produced mostly by orogenic movement. It dominates at or near the surface. It results in crushing and granulation of minerals, without the formation of any mineral. It is also known as dynamic metamorphism or cataclastic metamorphism, e.g., Mylonites. Water both heat and stress dominates, the metamorphism is known as Regional Metamorphism. here the country rocks are subjected to changes both in mineral composition and texture. It is also known as dynamo thermal metamorphism.

Chemically active fluids.

These are from the following sources: a) Meteoric water. b) Juvenile water. Water carries minerals in some cases in solution and also serves as a medium in which chemical changes occur with ease. Chemical activity is more pronounced in the vicinity of the igneous intrusions.

Grades of Metamorphism

The degrees of metamorphism or grades depend upon the extent to which the agents were in operation during the process. According to the temperature, pressure condition, there are usually three grades of metamorphism and accordingly, there are three zones: 1 Epizone. It is the zone of low-grade metamorphism, where temperature ranges from 100 to 300 degree C, pressure is low to moderate. It is characterized by the presence of the hydrous minerals. Sericite, muscovite, chlorite, biotite, talc, actinolite, epidote, andalusite etc. Rocks. Slates, phyllites, chlorite-schists, muscovite-schists, biotite-schists. 2. Mesozone. This is the zone of medium grade metamorphism, where the temperature ranges from 300 to 500 degree C, pressure is moderately high. It occurs at an intermediate depth, i.e., between 5 to 10 miles. Minerals. Biotite, andalusite, cordierite, quarz, hypersthene, almandine, orthoclase. ilmenite etc. Rocks. Phyllites and mica-schists. 3. Katazone.  It is the zone of high grade metamorphism where the temperature ranges from 500 to 650 degree C, pressure is high. It occurs at a depth of 9 to 13 miles. It is characterized by anhydrous and anti-stress minerals. Minerals. Biotite, alkalifeldspar, plagioclase, quartz, garnet, silimanite, kyanite, etc. Rocks. Gneisses of various types, hornfels etc.

In case of Regional metamorphism, the following grades have been identified:

  1. Zone of Chlorite
  2. Zone of biotite
  3. Zone of Garnet
  4. Zone of staurolite
  5. Zone of kyanite
  6. Zone of sillimanite
These zones are according to the progressive grade of regional metamorphism.

Human Nervous System

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Human Nervous System
Nervous system is fully restricted to animals and not found in plants. It is mainly an ectodermal in origin and functions in an integrated manner for control and coordination of various body functions (responding, understanding and memorizing) through neurons and hence also called as a neural system. The neural system and endocrine system work together to control and coordinate various body parts to maintain physiology. The neural system is basically a control system involve highly specialized cells, called neurons.

Neurons (basic unit of nervous system)

It functions by detecting and receiving information from different sense organs, i.e., receptors in the form of stimuli and transmit the stimuli to the central nervous system. Neuron or nerve cell is a structural and functional unit of neural tissue. They are known to be the longest cells present in the human body. Human neural system has about 100 billion neurons and they are mostly present in brain. Structurally, neuron has following two main parts

Cell body – nervous system

It is also known as cyton or soma that vary in size and form. It may be irregular, spherical, oval, round, star-shaped or pyramidal. They have neurofibrils and Nissl’s granules that play a characteristic role in the body. Neurofibrils play a significant role in the impulse transmission while Nissl’s granules or Nissl’s bodies are like rough endoplasmic reticulum with numerous attached free ribosomes and polysomes, i.e., synthesize proteins for the cell. Some neuro-tubules are also present that help in maintaining the shape of the neuron. Functions: These are mainly associated with metabolic maintenance and growth.

Neurites – nervous system

The process associated with neurons are called neurites. These are mainly of two types

Dendrites

These are usually shorter, tapering and much-branched structures, which contains neurofibrils, neuro tubules and Nissl’s granules. They conduct nerve impulse towards the cell body and this process is called afferent process (i.e., the receiving process).

Axon

It is a very long structure of uniform thickness. The part of cyton from where the axon arises is known as axon hillock. It is mainly dependent on cell body for the supply of protein. Each branch of axon fiber terminates as a bulb like structure called synaptic knob that possess some chemicals called neurotransmitters. Axons mainly conduct nerve impulse away from the cell body and therefore the process is called as an efferent process. Axons are mainly of two types
Myelinated 
Axons are nerve fibers enveloped with Schwann cells that form a myelin sheath around the axon. It mainly found in spinal and cranial nerves.
Unmyelinated
Axons are nerve fiber enveloped by a Schwann cell that does not form a myelin sheath around the axon and is commonly found in autonomous and motor neurons somatic neural system.

Types of Neurons

Sensory Neurons

They conduct impulses from receptors to central nervous system. The terminal ends of dendrites become modified to form receptor and acts as sensory.

Inter Neurons

They act as connectors and functions in connecting the sensory and motor neuron. It mainly carries stimuli in the brain and spinal cord.

Motor Neurons

They conduct impulses from central nervous system to the effectors i.e., they mainly transmit impulse from brain and spinal cord to the muscle or gland, which will respond to the stimulus. On the basis of the number of dendrites and axons neurons can be of other three types i.e., Multipolar (with one axon and two or more dendrites), Bipolar i.e. (with one axon and one or more dendrites), Unipolar i.e. with one axon only.

Parts of Human Nervous system

Human nervous system mainly constitutes three different parts
  1. Central Nervous System
  2. Peripheral Nervous System
  3. Autonomic Nervous System

Central Nervous System (CNS)

It is mainly comprised of brain and spinal cord.

Brain – Central Nervous System

It is the anterior portion of the CNS which is lodged in the cranial cavity, i.e., cranium of the skull. It weights from 1220 to 1400 grams.

Structure – Brain

Structurally, it consists of three membranes (meninges) i.e., pia mater membrane (innermost thin, very delicate, vascular and inverts the brain closely), arachnoid membrane (outer to diameter, thin, spider, webby structure) and durameter membrane (outermost, tough fibrous membrane, adhering closely to the inside of the skull). Cerebrospinal Fluid The space between arachnoid membrane and piamater is known as subarachnoid space in which a fluid known as cerebrospinal fluid, serves as pad to cushion the central nervous system from shocks. It also provides a medium for exchange of food materials, waste, respiratory gases and other materials

Human brain structurally consists of three main parts

Fore Brain (Prosencephalon)
It includes olfactory lobes, cerebrum, and diencephalon. i) Olfactory lobes are the anterior part of the brain formed by a pair of short club shaped structures. They are fully covered by the cerebral hemisphere. Function of these olfactory lobes are concerned with the sense of smell. ii) Cerebrum is the largest and most complex part of the brain. It mainly have two hemisphere (i.e. left and right) connected by a large bundle of myelinated fibres, the corpus callosum and small bundle of fibers.
Structure of Cerebrum
The outer portion of cerebrum is called the cerebral cortex. The surface of the cortex is greatly folded. The upward folds are known as gyri. There is a cavity present inside the cerebrum whose outer part is known as grey matter and inner part (i.e., beneath the grey matter) is the white matter.
Functions of Cerebrum 
It has sensory areas that receives impulse from receptor motor area that transmits impulse to the effectors Diencephalon The main parts involved in diencephalon are epithalaums, thalamus and hypothalamus.
  • Thalamus represents the lateral walls of diencephalon and mainly formed of grey matter. It is the relay station of sensory inputs and does not produce hormones.
  • Epithalamus thin membrane tissue that acts as a posterior segment of the diencephelon
  • Hypothalamus contains a number of centres that control urge for eating and drinking. It also called as thermostat of the body, because it acts as thermoregulatory centre. It also integrates and control the visceral activites.
Functions of Diencephalon It control and coordinate various functions like body temperature, feeling of satisfaction, appetite, thirst etc.
Mid Brain
It is mainly the portion located in between the thalamus/hypothalamus of the forebrain and pons of the hind brain. There is canal known as cerebral aqueduct that passes through the mid brain. Mid brain and hind brain together forms the brain stem.
Functions of Midbrain.
  1. It relay impulse back and forth between cerebrum, cerebellum, pons, and medulla.
  2. It is also concerned with sense of sight.
Hind brain
It involves some parts like cerebellum and pons, medulla. Cerebellum  It is second largest part of the human brain. It has convoluted surface in order to provide more space for many more neurons. Functions of Cerebellum It controls rapid muscular activites such as running typing and even talking. Nearly all activities are involuntary in nature but sometimes may involve learning in early stages. Pons It is located below mid brain and above the medulla oblongata Functions of Pons: It relays impulses between medulla to regulate breating Medulla (Oblongata) It extends from the pons varolii in above direction and is continuous with the spinal cord in below direction. Functions of Medulla It functions as receiver, integrates signal from spinal cord and sends resulting signal to the cerebellum and thalamus. It mainly have centres that regulate heart rate, blood prssure, breating, swallowing salivation, sneezing, coughing, vomiting and other involuntary movements etc.

Spinal Cord (Myelon) – Central Nervous System

It extends from the base of the brain and is continuous to the second lumbar vertebra. In adult, the spinal cord ranges from 42 to 45 cm in length. It manly lies in the neural canal fo the vertebral column. It is basically the posterior part of CNS which runs mid-dorsally within the vertebral column. The three meninges, i.e., duramater, arachnoid and piameter which covers the brain, also continue over the spinal cord. The two indentations, i.e., posterior median sulcus and the anterior median tissues separates the spinal cord into left and right halves. The inner area is the grey matter, while outside to it are white columns called the white matter.

Functions of Spinal Cord

i) The stimuli pass from and to the brain through the spinal cord. ii) It also acts as the center of spinal reflex action.

Peripheral Neural System (PNS)

The nerves that originate from central nervous system connect either with receptor or effector organs from peripheral neural system and those nerves which arise from brain are called cranial nerves while the nerves originating from the spinal cord are termed as spinal nerves. It relays impulse from the CNS to skeletal muscles. In human body there are 12 pairs of cranial nerves and 31 pairs of spinal nerves.

Autonomic Neural System (ANS)

It transmits impulse from the CNS to the involuntary organs and smooth muscles of the body. This system was discovered by Langly in 1921. It is further divided into two types.

Sympathetic Nervous system

Accelerates heart beat, enlarge pupils, supply blood to muscles, contract nerves of urinary bladder, lower the intestinal digestion activities, helps in blood clotting, increased secretion of sweat glands, make breathing easier and promote liver to release sugar and decrease bile production are some activities controlled by this nervous system.

Parasympathetic Nervous System

Works just analogous to the sympathetic nervous system, i.e., slows down heart beat. dilates arteries and lower blood pressure, speeds up peristalsis, stimulate salivary gland secretion, contracts gall bladder, promotes pancreas for secretion, decreases the secretion of sweat glands etc.  

Human Digestive System

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Human Digestive System

Digestive system anatomy

Biomacromolecules which we consume in our food is not directly utilized by our body in its original form. Thus, they are subjected to a process called digestion and the system that helps in the complete process of digestion by mechanical and biochemical methods is called digestive system. The human digestive system consists of various parts (organs and glands) that are concerned with the uptake, digestion, and elimination of indigestible remains of food from the body.

Human digestive system organs

Human digestive system diagram
Human digestive system

Alimentary Canal- Human Digestive system

The Alimentary canal in human beings is a long tube (about 8 to 10 meters in length) which begins with an anterior opening i.e., mouth and ends posteriorly through the anus. Parts associated with the alimentary canal are as follows

1. Mouth

It is transverse slit bounded by two soft movable lips which are covered with skin on the outer side and lined with mucous membrane on the inner side.

2. Vestibule

Mouth mainly leads to vestibule which is a narrow space enclosed between the lips and cheeks externally and the gums and teeth internally. It’s lining contains mucous glands.

3. Buccal Cavity

It is bounded by lips and cheeks. It contains teeth, tongue and salivary glands. Mouth (buccal) passes through both the jaws. The uppermost portion of the buccal (mouth) cavity is called palate. The upper and lower jaws of the buccal cavity consist of two separate sequences of teeth.

Teeth

These are hard structures present in the mouth and both the jaws (i.e., upper and lower jaw). Each tooth is embedded in a socket of jaw bone. A tooth consists of 3 major parts, namely crown (upper part), neck (middle part) and root (lower part). In human beings, the number of teeth presents in 32, 16 teeth present in each jaw. The half teeth of the jaw are towards left while the rest half is towards right. The arrangement of these teeth includes two incisors, one canine, two premolars and three molars on each side (half). Each of the teeth is specialized to perform a particular function. The main function of teeth is to perform physical digestion.
  • Incisors are outer mostly forward, flatten and extremely sharp, which helps in biting or cutting the food.
  • Canines are sharply pointed which crack and split or tear the food.
  • Premolars and molars, crush, grind and chew food smoothly.
 

4. Tongue

It is a highly muscular organ containing voluntary muscles attached to the floor of the buccal cavity with the help of a connective tissue (frenulum linguae). There are taste buds present on the tongue to realize the nature of the food like sweet, salt and sour. Functions The tongue helps in tasting and swallowing of food. It also helps in the process of speech and masticating the food by mixing saliva with it.

5. Pharynx

The pharynx is small (12 cm long) vertical canal beyond the soft palate of the oral cavity. It acts as a common passage for both air and food. i.e., it communicates with both oesophagus and treachea. During swallowing of food, trachea is covered by epiglottis (a cartilagenous flap or lid) to prevent the entry of food into trachea (wind pipe).

6. Oesophagus

The oesophagus is a thin, long highly muscular and purely conducting (23 to 27 cm long) tube. It opens in the stomach. Its opening is called gullet and carries food to it. The secretion of fluid from the mucous glands present in the wall of oesophagus helps in the forward movement of food. A muscular gastro-oesophageal sphincter regulates the opening of oesophagus into the stomach. Function It transfers food from the pharynx to the stomach.

7. Stomach 

Stomach It is the widest organ and the most dilated organ of the alimentary canal. The stomach is J shaped organ which churns, breaks up food and mix the pieces with gastric juice (include enzymes like renin, pepsin and HCl). The inner lining of stomach secretes various components like mucous, hydrochloric acid and digestive juices. The mucous lining of stomach protects it fromthe acidic environment and allow it to work firmly. Stomach has three major parts as given below
  • Cardiac Stomach, the upper portion into which the oesophagus opens.
  • Fundic stomach, the middle portion
  • Pyrolic stomach, the lower portion which open into the first part of small intestine, i.e., duodenum. The terminal pyrolus part of stomach (i.e., opening of stomach into duodenum) is guarded by a pyrolic sphincter.
Functions
  • It acts as a short term reservoir of food
  • Food become liquified in the stomach before being released into the small intestine.

8. Intestine

Small Intestine: 

It is the longest part of the alimentary canal. It is about 6m long It is divisible into three main parts as
  1. Dudenum: It is U shaped, about 25cm long and is the widest part of the small intestine.
  2. Jejunum It has a diameter of about 4 cm. It is the middle part of the small intestine and is about 2.5 metres long.
  3. Ileum It is the last part with diameter around 3.5 cm. Its wall is thinner than that of the jejunum. It is the longest part of small intestine. Ileum opens into the colon of large intestine.
Functions:  Small Intestine completes digestion of components like proteins, carbohydrates, nucleic acid and fats. Thus, acts as major site in digestion of food. It absorbs nutrients into the blood and lymph and also helps in absorption of fats.

Large Intestine

Although it is shorter, but its diameter is larger than that of the small intestine thus, it is known as large intestine. It is about 1.5 metres long and is divisible into three main part as
  1. Caecum It is a small pouch like structure of about 6 cm. It also has an outgrowth known as vermiform appendix, which is slightly coiled tube of about 8 cm long.
  2. Colon The caecum part leads into the colon. The colon has three main parts as ascending, transverse and descending part.
  3. Rectum The descending portionof colon leads into the rectum which is the last part of the intestine. Rectum is of about 20 cm in length and opens into the anus.
Functions The absorption of water and nutrients and elimination of solid wastes takes place mainly in large intestine.

Digestive Glands

To bring about the simplification of complex food molecules chemically, secretion of digestive juices take place by different glands. These are as follows

Salivary or Mouth Watering Glands

These are exocrine glands which discharge their secretion into the oral cavity. In man there are three pairs of salivary glands; parotid, sublingual and submandibular glands. The fluids secreted by the salivary glands constitute saliva, which is a slightly acidic fluid (pH 6.8). Saliva is mainly a mixture of water, electrolytes (Na+, K+ Cl-, HCO3-) derived from blood plasma, mucous, serum fluids, and enzyme, i.e. salivary amylase or ptyalin and lysozyme (antibacterial agent)

Gastric Glands

Glands of stomach are called gastric glands. These are numerous microscopic, tubular glands formed by the epithelium of the stomach. Gastric glands have three majro types of cells
  • Chief cells or peptic cells which secrete inactive precursors of gastric enzymes.
  • Oxyntic cells secrete hydrochloric acid.
  • Mucous cells or Goblet cells secrete alkaline null cells.
The secretions from these cells form gastric juice with pH 1.5 2.5 (very acidic). The gastric juice contains two proenzymes, i.e., pepsinogen (propepsin) and prorennin and the enzymes gastric lipase gastric amylase, mucous and hydrochloric acid.
In human body, about 2000-3000 mL of gastric juice is secreted per day.

iii) Liver

It is the largest gland of the body that lies in the upper right side of the abdominal cavity just below the diaphragm. It is heavier in males ( i.e., about 1.4-1.8 kg) as compared to females (about 1.2-1.5 kg). Internally the structural and functional units of liver are the hepatic lobules (containing hepatic cells arranged in the form of cords). Each lobule is covered by a thin connective tissue sheat called the Glisson’s capsule. Fat storage cells are also present in liver.

iv) Pancreas

Pancreas is a soft, lobuled, greyish pink gland which weighs about 60 gm. It is about 2-5 cm wide and 12-15 cm long, located posterior to the stomach in the abdominal cavity i.e. between stomach and dudenum. As it is mixed gland, the exocrine portion of pancreas seccretes an alkaline pancreatic juice (containing enzymes and hormones) while, the endocrine part of the pancreas consists of group of cells known as Islets of Langerhans, which secrete hormones to be passed into the circulating blood, i.e., insulin and glycogen.

v) Intestinal glands

Apart from the above mentioned glands involved in the process of digestion, Intestinal glands are also present in the walls of small intestine called intestinal glands which secretes intestinal juice (containing lipolytic, proteolytic and amylolytic enzymes) commonly called as succus entericus.

Next Mechanism of Digestive system or Functions of Digestive system

 
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