HTET PGT Biology Syllabus - Level 3

HTET PGT Biology Syllabus

HTET - Haryana Teacher Eligbility Test HTET PGT Biology Syllabus in detailed form is given below.

Reproduction of organisms

1. Life span, definition & types of reproduction.
2. Asexual & sexual reproduction. Budding, Binary fission, Spores, Clones, gemmule,.
3. Vegetative propagation, Terror of Bengal.
4. Sexual reproduction, Juvenile, Vegetative and senescent phase
5. Oestrous & menstrual cycle, seasonal & continuous breeders 
6. Events in sexual reproduction, Prefertilization events 
7. Gametogenesis, sexuality in organisms, cell division during gametogenesis. Diversity of sexuality in plants & animals, (only Diagram)
8. Gamete transfer, chromosome number in meiocytes, pollination, fertilization/syngamy.
9. Parthenogenesis, External & internal fertilization
10. Post fertilization events- the zygote, embryogenesis, oviparous & viviparous.
11. Post fertilization changes in flowers.

Sexual Reproduction in flowering plants.

1. Flower fascinating organs of Angiosperms.
2. Prefertilization:- structure and events-stamen, microsporangium & Pollen grain, Structure of microsporangium, microsporogensis.
3. Pollen grain, Pollen Products. Pistil, megasporangium (ovule). Megasporogenesis, female gametophyte or embryosac.
4. Pollinations, kinds of Pollinations, Agents of Pollinations, Adaptations in flowers for pollination, out-breeding devices. Pollen robbers & nectar robber, Pollen pistil interaction, Artificial hybridization. Double fertilization, Post fertilization:- Structure & Events.
5. Endosperms, Embryo - dicot & monocot, non albuminous and albuminous seed, coleorhiza, coleoptiles, advantages of seed, seed, dormancy, fruit-true & false.
6. Parthenocarpic fruit, Apomixis, polyembryony, Hybrid Varieties

Human Reproduction

Male Reproductive system, Female Reproductive system, structure of mammary gland, Gametogenesis- spermatogenesis, oogenesis. Role of Hormones in gametogenesis, Structure of sperms & ovum. Menstrual cycle fertilization & implantation, sex of baby, Pregnancy & embryonic development. Placenta, its role, Major features of embryonic development during pregnancy. Parturition & Lactation & Colostrums.

Reproductive Health

Reproductive Health- Problems & Strategies, RCH its role. Aminocentesis, Population explosion, Birth-control, Infant Mortality Rate & Maternal Mortality Rate. Effects of population explosion, Ideal contraceptives, various methods of population control-natural & artificial. Medical termination of Pregnancy. Why MTP? STD, various method/measure to control the STD. Infertility & various ART. Also See: HTET Level 3 PGT Biology Previous year question paper download pdf

Principles of Inheritance and Variation

Mendel’s law of inheritance, contrasting traits studied by Mendel in pea, steps in making a cross in Pea. Inheritance of one gene.  Definitions- gene, allele, genotype, phenotype, homozygous & heterozygous, dominant, recessive. Monohybrid cross, Punett square, test cross, law of dominance, law of segregation, incomplete dominance, explanation of concept of dominance. Codominance, multiple allelism, inheritance of two genes (Dihybrid cross) law of independent Assertment, chromosomal theory of inheritance, comparison between behavior of chromosome & genes. Drosophila melanogaster, linkage and recombination, sex determination: sex chromosome and autosomes, male & female heterogameity, sex determination in human, mutation, pedigree analysis, Mendelian disorders- Haemophilia, sickle cell Anaemia, phenylketonuria, chromosomal disorders- aneuploidy & polyploidy down’s syndrome, klinfelter’s & turner’s syndrome.

Moleculer Basis of Inheritance

The DNA: Structure of polynucleotide chain, central Dogma. Packaging of DNA helix, histone & Non histone, nucleosome, Euchromation & hetero chromatin. The search for genetic material Transforming Principle, Biochemical characterisation of transforming Principle. The Genetic material in DNA. Properties of Genetic material (DNA & RNA). Criteria of genetic material. RNA world, DNA Replication, Semiconservative mode with experimental proof. The Machinery and enzyme, transcription, transcription Unit, Template and coding strand, Transcription unit and gene, exon and introns. Types of RNA and process of transcription. Splicing, capping and tailing. Genetic code, Mutation and genetic code, sickle cell Anaemia, Frameshift mutations. tRNA- the adapter molecule, Translation. Initiator and terminator codon. Role of Ribosome in translation. Regulation of gene expression, lac operon, HGP, Goals salient features of Human Genome, Application and future challenges, DNA fingerprinting, repetitive & satellite DNA.

Evolution

Origin of life, Big bang Theory, Theory of spontaneous generation, Miller & Urey’s expt, Oparin & Haldane Theory of Abiogenesis, Evolution of life forms-A theory. What are the evidence of evolution? Homologus & Analogus organ , divergent and convergent evolution. Industrial Melanism, Evolution of pesticide Resistant variety. What is adaptive radiation? Biological evolution, Mechanism of evolution, Malthus Theory, Saltations, H.W. principle & its factors, founder effect. Types of Natural selection on different Traits. Brief account of evolution, Evolution of plant forms through geographical period, Evolutionary history of vertebrates through geological periods, origin and evolution of man.

Human Health and Disease

Health, Disease and types, common disease in Human- Typhoid, pneumonia, common cold, malaria, life cycle of plasmodium, amoebiasis, Ascarasis, Elephantiasis (Filarasis) Ringworms, prevention and control of infections disease, Immunity- innate, acquired. Structure of antibody molecule, Primary & secondary response, different types of Antibody Humoral & cell mediated Immunity. Active & passive Immunity, vaccinations & Immunisation , Allergies, Autoimmunity, Immune system in the body- Lymphoid organs, MALT, AIDS, Replication of Retrovirus, Cancer, Benign & Malignant Tumour, Metastasis Carcinogens. Drugs and alcohol abuse, smoking, adolescence & Drug/alcohol abuse, Addiction & dependence, withdrawal symptoms, effect of Drugs/alcohol abuse, Preventions and control of Drugs.

Strategies for Enhancement in Food Production

Animal Husbandry, Management of farms and farms animals: Diary farm management, Poultry farm management, Inbreeding and out breeding, inbreeding depression, out breeding & cross breeding, Inter specific hybridization, controlled breeding using artificial insemination MOET (Multiple ovulation Embryo transfer) Bee keeping, fisheries, plant breeding: what is plant breeding, some Indian hybrid crops (a) Maize (b) wheat (c) garden pea (d) Rice (e) sugarcane (f ) Millets. Plants breeding for disease resistant. Mutation breeding, crop varieties for disease resistant (Table). Plant breeding for developing resistance to insect pests, Released crop variety for insect pest Resistance (Table). Plant breeding for improved Quality. Biofortification, SCP, Tissue culture-somatic hybridization

Microbes in Human Welfare

Microbes in House hold products, Microbes in Industrial Products, (fermenters), fermented beverages, Antibiotics, chemicals, Enzymes & Other bioactive molecules, Microbes in sewage treatment, BOD, floes, Activated sludge, biogas, Ganga & Yamuna Action plan. Microbes in production of biogas, Biogas plant, Microbes as Biocontrol Agents, Bt cotton, Baculovirus, Microbes as biofertilizers, organic farming.

Bio Technology; Principles and Processes

Principles of biotechnology, gene cloning, plasmid, Restriction Enzyme, basic steps in genetically modifying an organism. Tools of Recombinant DNA technology: Restriction Enzymes, Recoginition sequence, Palindromic Nucleotide sequence, gel electrophoresis, cloning vectors, competent host (recombinant DNA) Processes of rDNA technologyisolation of genetic material (DNA), cutting of DNA at specific location, PCR, Insertion of rDNA into host, obtaining the foreign gene Product, Bioreactors, Down stream Processing.

Bio Technology And its Application

Three critical research areas of biotechnology, Biotechnology Applications in Agriculture, Green revolution, Genetically modified organisms (GMO), BtCotton, cry gene & Cry protein, Pest Resistant Plants, RNA interference, Biotechnological Applications in Medicines - Genetically Engineered Insulin, Gene therapy, Molecular Diagnosis, Transgenic animals, Ethical Issues, GEAC (Genetic Engineering Approval Committee), Biopiracy.

Organisms & Population

1. Levels of Biological organization, organisms and environment Major biomes of India, Major Abiotic factors- Temp, Eury thermal & Stenothermal, Water, light & soil.
2. Responses to Abiotic factors, homeostasis, Regulators & conformors migration, suspend, Adaptations in Desert plants & animals, Aestivation & Hibernation.
3. Allen’s rule, Altitude sickness, Behaviorial responses with variation in environment.
4. Population Attributes, Population ecology, Age structure/age pyramid for human population, Population density. 
5. Population Growth- natality, mortality, immigration, Emigration Growth Models- Exponential, & logistic growth curve.
6. Life history variations, Population-interaction-Predation, competition, Gause’principle, competitive release, Parasitism, adaptation in parasites, resource partitioning. Ectoparasite & endoparasite, Brood-parasitism, commensalism, mutualism, one-to-one relationship, sexual deceit.

Ecosystem

Ecosystem its types, Structure & function, Biotic & Abiotic components, stratification, various components of ecosystem. Productivity & types, Decomposition- various steps & factors, detritus, Energy flow, photosynthetically Active Radiation (PAR)  Producers, consumers, Herbivores & Carnivores, Decomposition cycle, terrestrial ecosystem grazing & detritus food chain, food web, various trophic levels of ecosystem, standing crop, ten percent law of energy, Energy flow through various trophic levels, ecological pyramids, ecological succession- Primary & Secondary, Hydrach & Xerach.  Nutrient cycling- standing state, carbon cycle, phosphorus cycle, ecosystem services.

Biodiversity & Conservation 

• Biodiversity -types, How many species are there on earth & how may in India Representation of global bio-diversity: Proportionate number of species of major taxa of plants, invertebrates & vertebrates, India a mega diversity nation. 
• Pattern of Bio-diversity -latitudinal gradients, species area relationship, the importance of species diversity- Rivet Popper hypothesis, loss of biodiversity, causes of bio-diversity loss. Habitat loss & fragmentation, over exploitation, alien species, invasion, co-extinction. Why should we conserve biodiversity? How do we can serve biodiversity? In situ conservation, ex situ conservation, Earth summit & world summit.

Environmental Issues

Pollution, pollutants, environmental act, air pollution & its control, Electrostatic precipitator, scrubber, catalytic converter, automobile pollution, Air, noise pollution Controlling vehicle air pollution, A case studyof Delhi, CNG, Auto Fuel policy, Euro norms - II&III, Water pollution & its control, Water Act, Domestic sewage & industrial effluents composition of waste water, BOD, Effect of sewage discharge into a river, algal bloom, Biomagnifications, Eutrophication, cultural or Accelerated Entrophication. Thermal waste water pollution, case study of integrated waste water treatment, ecological sanitation, solid waste- types, electronic waste, case study of remedy for plastic waste, Agrochemicals & effects, case study of organic farming, radio active waste, Green house effect & global warming, ozone depletion in stratosphere - Good ozone & bad ozone, ozone hole, UV-B, Montreal Protocol. Degradation by improper utilization & maintenance- Soil erosion & desertification , water logging & soil salinity, Deforestation slash & bum agriculture or jhum cultivation, Reforestation. Case study of people participating in conservation of forests, Amrita Devi Bishnoi wild life protection award, chipko movement, Joint Forest Management (JPM)

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Chapter No.-1 : The Living World:

What is living, All living organisms grow, Reproduction-character of living organism, Metabolism-characteristic of life, consciousness-the defining property of living organisms. Diversity in the living world, Nomenclature, Identification, Binomial nomenclature rules, Classification, Taxonomy, Systematic, Taxonomic categories, Species, genus, family, order, class, phylum, kingdoms, Taxonomical Aids, Herbarium, Botanical gardens, Museum, Zoological park. key.

Chapter No.-2 : Biological Classification

Two kingdom classification, Five kingdom classification, Kingdom Moneraclassification of bacteria on basis of form, Archaebacteria, Eubacteria cyanobacteria, heterocysts, heterotrophic bacteria, fission in bacteria, Mycoplasma, kingdom Protista, chrysophytes, Dinoflagellates, Englenoids. Slime moulds, protozoans-amoeboid protozoans, flagellated, ciliated, sporozoans. kingdom-fungi- mycorrhizae, dikaryon, lichen, phycomycetes.ascomycetes, basidiomycetes, deuteromycetes. Kingdom-plantae, cuscuta, alternation of generation. Kingdom animalia, virus, viroids and lichens, phycobiont, mycobiont.

Chapter No. -3 : Plant Kingdom

artificial and natural system of classification, phylogenetic classification, numerical taxonomy, cytotaxonomy, chemotaxonomy, algae, green, brown and red algae - characters & products, examples. Photosynthetic pigments of these algae, Bryophytes- gametophyte, sporophyte, liverworts and mosses, gemma, protonema & its examples. Pteridophytes-sporophylls, prothallus, homosporous, heterosporous, seed habit, examples, Gymnosperms- examples, sporophylls, ovule archegonia, antheridia, angiosperms- flowers, dicots & monocots, double fertilization, embryo sac, life cycle of An angiosperm, Plant life cycles and alternation of generations- haplontic, diplontic & haplodiplontic life cycles.

Chapter No. 4 : Animal Kingdom

Basis of classification-Level of organization, symmetry, diploblastic, triploblastic, coelom, segmentation, notochord, classification of animals, phylum— poriferae-characters & examples. Phylum- coelentrata (cnidaria)- characters & examples, ctenophora, platyhnelminthes, aschelminthes, annelida, arthropoda. mollusca, echinodermata, hemichordata, urochordata, cephalochordata, vertebrate-class-cyclostomata, chondrichythyes, osteichthyes, amphibia, reptilian, aves, mammalia, chart of characters.

Chapter No.-5: Morphology of flowering plants

The root, root systems, regions of root, modification of root, the stem-node & internode, modification of stem-underground stem, tendrils, thorns, suckers, corms, stem spine, Leaf-bud, leaf base, Petiole & lamina, venation. Reticulate & parallel, types of leaves- simple and compound- pinnate & palmate, phyllotaxy- alternate & opposite, whorled, modification of leaves- tendrils, spines, fleshy, Inflorescence- Racemose and cymose, flower- thalamus, arrangement of floral parts, unisexual, bisexual, symmetry- actinomorphic, zygomorphic or asymmetrical, trimerous, tetramerous, pentemerons, Bracteate, ebrecteate, ebicteolate, hypogynous, perigynous, epigynous, superior, inferior & half sueriour. Parts of flower calyxgamosepalous, polysepalous, corolla- gamopetalous & polypetalous, aestivation- valvate, twisted, imbricate, vexillary androceium- staminode, typical epipetalous, epiphyllous mono, diadelphous & polyddelphous, gynoceium - ovary, style & stigma, placenta, apocarpous, syncarpous, Placentation- marginal, axile, parietal, basal, free central & superficial. Fruitparthenocarpic, pericarp- epicarp, mesocarp & endocarp, seed- structure of dicot and monocot seed with example of maize & grams. Floral formula and floral diagram- in detail of familyFabaceae, solanaceae, Liliaceae with examples.

Chapter No.-6; Anatomy of flowering plants

The tisues and types- Meristamatic and Permanent, intercalary, primary, secondary, apical, lateral meristem, Permanent tissue- simple and complex, parenchyma, collenchyma, scherenchyma, sclereids & fibers. Complex-xylem and phloem, tracheids, vessels, fibers, paranchma- protoxylem, metexylem, endarch, exarch, mesarch, phloem, sieve tube, companion cell, parenchyma and fibers, protophloem, metaphloem. The tissue system- epidermal, ground & vascular tissue system , epidermal, epidermis, cuticle, stomata, guard cells, subsidary cells, stomatal apparatus. Root hair & Trichome. Ground tissue system mesophyll & cortex. Vascular tissue systemcambium, open & closed, Radial, conjoint, anatomy of dicot & monocot plants - Dicot & monocot root, stem & leaf. Secondary growth in dicot stem & dicot root- activity of vascular cambium, cork cambium, spring wood, autumn wood, heart wood, sap wood, bark and lenticels.

Chapter No. 7: Structural organization in animals

Tissue and types epithelial- simple, compound, simple- squamous, cubodial, columnar, ciliated, glandular compound, skin, junctions. connective tissue- loose and compact, dense, specialized, loose- areolar, adipose dense- regular & irregular, specalized ones and blood & cartilage. Muscle tissue- skeletal, smooth and cardiac Nervous tissue, organ and organ systems, earthworm- morphology, anatomy, digestive, circulatory, reproductive, excretory, nervous, cockroach-morphology- mouth parts, anatomy-digestive, excretory. Respiratory, Reproductive, circulatory frog- morphology , anatomy- digestive, excretory, reproductive & others.

Chapter-8: Cell: the Unit of Life

What is cell, cell theory, an overview of cell, Prokaryotic cell, cell envelope and its modification- Gram +ve & Gram -ve bacteria, cell wall, mesosome, pili, fimbriae, 7oS Riboscmes, Polysome. Eukaryotic cell- cell wall, cell membrane, structure, fluid mosaic model, cell organelles- cell wall. ER. Golgi comples, Lysosomes, Vaccoules, Mitochondria, Plastids, Ribosomes, cytoskeleton- cilia & flagella, centrioles, nuclear- chromosomes, structure and classification. Active, passive transport, osmosis.

Chapter No.9: Biomolecules:

How to analyze chemical composition, organic & inorganic molecules, macromolecules, micromolecules, Primary and secondary metabolites. Proteins, Polysacharides, Nucleic acid, structure of proteins- Primary, secondary, tert & Quartenary peptide bond and glycosidic bond, dynamic state of body constituents- concepts of metabolism- turnover no, Metabolism, catalytic actions and reaction of enzymes, metabolic basis for living, ATP, The living state-steady and homeostasis, Enzyme- chemical nature, denaturation, chemical reactions, how do enzymes bring about such high rate of chemical conversions. Nature of enzyme action, factors affecting enzymes activity- temp, pH, cone of substrate, inhibitors. Classification and nomenclature of enzymes, cofactors, prosthetic group, apoenzyme and coenzyme.

Chapter No. 10 : Cell cycle and cell Division

Cell cycle, phases of cell cycle, interphase, Mphase, karyokinesis, cytokinesis, G1 phase, S, G2 phase Quiescent. Go state, M phase- Prophase, metaphase, anaphase, telophase. Significance of mitosis, meiosis- meiosis I & II, Prophase-1 leptotene, zygotene, pachytene, diplotene, Diakinesis, synaptonemal complex, Bivalents, Tetrad, chiasmiata significance of meiosis.

Chapter No. 11: Transport in Plants

Means of Transport- diffusion, facilitated diffusion, Passive symports and antiports, porins and uniport, comparison of different transport processes, Plant water relation, Transpiration, water potential, solute potential, Pressure potential, Turgidity, osmosis, solute, solvent, solution, SPM, pressure gradient, Plasmolysis- isotonic, hypotonic & hypertonic solution, turgid, flaccid cells, imbibitions, long distance transports of water- mass or bulk flow, translocation how do plants absorb water- apoplast & symplast pathway plasmodesmata, endodermis, casparian strips, mycorrhizae. Water movement up a plant-root pressure, guttation, transpiration pull, cohesion tension transpiration pull- model transpiration- stomatal apparatus, guard cells, stomatal pore, surface tension, tensile strength capillarity, transpiration and photosynthesis- a compromise, uptake and transport of mineral nutrients, active absorption, translocation of mineral ions, phloem transport- flow from source to sink. The pressure flow or mass flow hypothesis.

Chapter No.12: Mineral Nutrition

Methods to study the mineral requirements of plants, hydrophonics, essential mineral elements, criteria for essentiality macro & micronutrients & role. Defeciency symptoms of essential element s- chlorosis, necrosis, inhibited growth, premature fall of leaf and buds & stunted plant growth, toxicity of micronutrients. Mechanism of absorption of elements active & flux. Translocation of solutes, soil as reserviour of essential elements, metabolisms of nitrogen, nitrogen cycle, N2 fixations, Nitrifications, chemoautotrophism, biological N2 fixation, symbiotic & nonsymbiotic N2 fixation, nodule formation, fate of ammonia, reductive amination, transamination.

Chapter No.13: Photosynthesis in Higher Plants:

What do we know? Early experiments, priestley’s expt, Where does photosynthesis take place, chloroplast, light reaction and dark reaction, how many pigments are involved in photosynthesis, chlorophyll a, b, xanthophylls and carotenoids, what is light reaction- PSI, PS II, electron transport, cytochromes, Z scheme, splitting of water, cyclic and nonocyclic photophosphorylation, chemiosmotic hypothesis, where are the ATP and NADPH2 used biosynthetic phase dark reacton calvin cycle, C3 and C4 pathway, graphical representation of calvin cycle, diagrammatic representation of Hatch and Slack phathway, Kranz anatomy, PEP, Photorespiration Factors affecting photosynthesis- Law of limiting factors. Light, C02 cone. Temp & water.

Chapter No. 14: Respiration in Plants:

Cellular respiration, repiratory substrates, Do plants breath, glycolysis, diagrammatic representation Kreb’s cycle, fermentation, anaerobic, aerobic respiration ETC and oxidative phosphorylation, Role of Mitochondria, Respriratory balance sheet, amphibolic pathway, Respiratory quotient.

Chapter No. 15 : Plant Growth and Development:

Diagrammatic representation of germination of bean seed and seedling, growth, plant growth is generally indeterminate, Growth is measurable, phases of growth, growth rate, constant linear & sig moid. Conditions for growth, differentiation, dedifferentiation, Redifferentiation. Development, sequence of developmental process in plant cell, plasticity, plant growth regulators- characterstics, discovery of regulators, physiological effects of plant growth regulators- auxins, gibberllins, cytokinins, ethylene & ABA. Photoperodism- SDP, LDP & DNP, Vernalisation

Chapter No. 16: Digestion and absorption:

Digestive system, alimentary canal and associated & glands, Graphical representation of human digestive system, types of teeth- thecodont, diphyodont, dental formula, various parts of all digestive organs, digestive glands, digestion of food- deglution, bolus, chyme goblet cells, success entericus. digestion of carbohydrates proteins, fats & nucleic acid. Absorption of digested products in forms of summary, disorders of digestive system- jaundice, vomiting, diarrhoeae, constipation & indigestion.

Chapter No. 17: Breathing and exchange of Gases.

Breathing vs respiration, respiratory organs. Human respiratory system, tract and organs, Mechanism of breathing, inspiration and expiration, respiratory volumes and capacities, exchange of gases. Diagramatic representation with special emphasis on alveolar capacity transport of gases, Transport of O2 & C02. Regulation of Respiration, Disorders of Respiratory systems- Asthma, Emphysema, OLD.

Chapter No. 18: Body fluids and circulation :

Blood- Plasma, RBC, WBC. platelets, Blood group- ABO group Rh grouping, coagulation of blood, lymph (Tissue fluid) circulatory path way, open & closed circulatory system Human circulatory system, structure of heart, cardiac cycle, electrocardiograph, double circulation, schmatic plan of blood circulation in human. Regulation of cardiac activity. Disorder of circulatory system, hypertension- CAD, Angina, Heart failure.

Chapter No.19: Excretory products and their elimination.

Ammonotelic, ureotelic, uricotelic animals, huma exertory system, diagrammatic representation of organs, Kidney (L.S) & nephron, urine formation, function of Tubules, Diagramatic representation of urine formation, Mechanism of cone, of the filtrate through Diagramatic representation of nephron and vasa Recta. Regulation of Kidney function, Micturition, Role of other organs in excretion. Disorders of excretory system. Ureamia, RF, Renal stones, Glomerulo nephritis.

Chapter No. 20 : Locomotion and movements:

Types of movement- Role of muscles, structure of contractile proteins, mechanism of muscle contraction through diagrammatic representation, sliding filament, theory, skeletal system- axial & appendicular, skull, ear ossicle, vertibral column, sternum, ribs, limb bones and girdles. Joints & types Disorders of muscular & skeletal system- myasthenia gravis. Muscular dystrophy, Tetany, Arthritis, osteoporosis & Gout Chapter No. 21: Neural control and coordination:

Chapter No. 21 : Neural Control and coordination :

Neural system, neurons, human neural system- CNS, PNS, ANS, Neuron as structural & functional unit of neural system, generation and conduction of nerve impulse, transmission of impulses at synaptic cleft, CNS- Brains & spiral cord. Reflex action and reflex arc, sensory receptors and processing, eye and its parts, mechanism of vision, ear & its parts, mechanism of hearing.

Chapter No. 22 Chemical coordination and Integration

Endocrine glands and hormones, human endocrine system, hypothalamus, Pitutary, Pineal, thyroid gland, Parathyoid, thymus, Adrenal gland, Pancreas, Testis, Ovary- Hormons & disorder. Hormones of Heart, kidneys and gastro interstinal tract, Mechanism of hormones action