Introduction Not all the known plants reproduce sexually. The flowering plants bear specialised organs for reproduction located inside the flower forming two inner whorls of the flower and regarded as the essential whorls.
Ecosystem
Ecosystem is the functional unit of nature where living organisms interact among themselves and also with the surroundings physical environment. Ecosystem- Structure and Functions Ecosystem : There are two basic categories of ecosystem , namely the terrestrial and the aquatic. Terrestrial ecosystem – forest, grassland , desert etc. Aquatic ecosystem – ponds, lake, river estuary etc. The biotic and abiotic factors of ecosystem work in integrated manner for flow of energy within the components of ecosystem. Interaction of biotic and abiotic components results in a physical structure that is characteristic for each type of ecosystem. The vertical distribution of different species occupying different levels is called stratification.For example, trees occupy top vertical strata or layer of a forest, shrubs the second and herbs and grasses occupy the bottom layers. The components of ecosystem that are seen as functional unit are (i) Productivity(ii) Decomposition(iii) Energy flow(iv) Nutrient cycling. · Productivity- Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (g –2 ) or energy (kcal m–2 ). The rate of biomass production is called productivity. It is expressed in terms of g –2 yr –1 or (kcal m–2 ) yr –1. It can be divided into gross primary productivity (GPP) and net primary productivity (NPP). GPP of an ecosystem is the rate of production of organic matter during photosynthesis and NPP is the remaining biomass after respiration (R). GPP –R = NPP NPP is the available biomass for consumption to heterotrophs. Secondary productivity is defined as the rate of formation of new organic matter by consumers. Decomposition- breakdown of complex organic matter into inorganic substances like carbon dioxide, water and nutrients is called decomposition. Dead plants remains like leaves, bark, flowers and dead remains of animals constitute detritus. Decomposition involves following steps- fragmentation, leaching, catabolism, humification and mineralization. Fragmentation of Detritus: Detritivores feed on detritus —breakdown — increases the surface area of detritus particles for microbial action. Leaching: Soluble inorganic nutrients dissolve in water -– percolate through the soil —removed due to leaching action. Catabolism: Decomposers (bacteria, fungi) release enzymes — decompose detritus — simpler inorganic compounds. Humification: Simplified detritus— converted to humus – Humus is a Dark, Amorphous substance.– Highly resistant to Microbial Action– Undergoes Decomposition very Slowly.– Reservoir of nutrients (due to colloidal nature) 5. Mineralisation: Humus is degraded – releases inorganic substances( CO2, H2O etc) and nutrients (Ca2+, Mg2+,K+ etc) Factors affecting rate of Decomposition: 1. Chemical composition – decomposition rate will be slow when detritus is rich in lignin and chitin and rate increases when detritus is rich in nitrogen and water soluble substances like sugars. 2. Climatic conditions – warm and moist environment favour decomposition and low temperature and anaerobiosis inhibit decomposition. Energy Flow- All living organisms are dependent for their food on producers, directly or indirectly. There is a unidirectional flow of energy from the sun to producers and then to consumers. Photosynthetically active radiation (PAR) is responsible for synthesis of food by plants. Animals obtain their food from plants, so they are called consumers. The process of eating and being eaten is called food chain in which energy flow from producers to consumers. In Grazing food chain (GFC)- The detritus food chain begins (DFC) begins with dead organic matter. It is made up of decomposers which are heterotrophic organisms (fungi and bacteria). These are also known as saprotrophs (sapro: to decompose). Decomposers secrete digestive enzymes that breakdown dead and waste materials into simple, inorganic materials, which are subsequently absorbed by them.Natural interconnection of food chain forms the food web. Based on source of food, organism occupies a specific place in food chain that is known as trophic level. Each tropic level has a certain mass of living material at particular time called as standing crop. It is measured as biomass of living organism or number in unit area. The number of trophic levels in the grazing food chain is limited as the transfer of energy follows 10 percent law that is only 10 percent of the energy is transferred to each trophic level from the lower trophic level. In GFC, following trophic levels are possible- producer, herbivore, primary carnivore, secondary carnivore. Ecological Pyramids Ecological pyramid is the graphical representation of an ecological parameter (number, biomass, energy) sequence wise in various trophic levels of a food chain with producers at the base and herbivores in the middle and carnivores at the top tiers. It can be upright, inverted, or spindle shaped. Three common ecological pyramids are a) Pyramids of number- employs the number of individuals per unit area at various trophic levels with producer at base and various consumers at successively higher levels. It is generally upright. A pyramid of number in case of a big tree is generally inverted because number of insects feeding on that tree generally exceeds in number. b) Pyramids of biomass- represent the biomass in various trophic levels. A pyramid of mass is upright except in aquatic food chain involving short lived plankton. A pyramid of biomass in sea is generally inverted because biomass of fishes generally exceeds that of phytoplankton. c) Pyramids of energy- that give s graphic representation of amount of energy trapped by different trophic levels per unit area. Pyramid of energy is always upright, can never be inverted, because when energy flows from a particular trophic level to the next trophic level, some energy is always lost as heat at each step e.g in feeding, digestion, assimilation and respiration. Ecological Succession The gradual and fairly predictable change in species composition of a given area is called ecological succession. During succession some species colonise an area and their population becomes more numerous whereas population of other species decline and even disappear. · Orderly and sequential change that leads to a community that is near equilibrium is called climax community. · The entire sequence of communities that successively changes in a given area is called sere and individual transitional communities are termed seral stage or seral
Equilibrium
Introduction: A state in chemical and biological reactions, during which there is no net change in the amounts of substances involved in these reactions is called the state of equilibrium. If water is boiled in a closed vessel, the rate of evaporation and rate of condensation will be equal in equilibrium conditions. The equation is as follows: H2O (l) ⇌ H2O (vap) Equilibrium is shown by a double arrow that is simultaneously moving in both directions. There is a significant amount of activity at the boundary between the liquid and vapour, thus this is not static equilibrium. As a result, at equilibrium, the rates of condensation and evaporation are equal. Equilibrium mixture refers to the combination of reactants and products in the equilibrium state. Equilibrium in the Physical Process: Transformations in nature may occur as physical changes involving the three states of matter; solid, liquid and gas. They may also undergo equilibrium when changing from one form to another. 1.Solid ⇌ Liquid – Ice and water are in equilibrium with one another at a particular temperature and pressure. These temperatures are the normal melting or boiling points of a particular state of matter. A system is at equilibrium when both processes of melting and freezing occur simultaneously and at the same rate to keep the same amount of water and ice in reaction. 2. Liquid ⇌ Gas – Molecules from the vapour phase enter the liquid phase until an equilibrium is reached, in which case: Rate of Condensation = Rate of Evaporation, This rate depends on the nature of the liquid, the amount of liquid and the applied temperature. 3.Solid ⇌ Gas – In sublimation reactions, solids turn into vapour and thereby reach a state of equilibrium. Eg. Camphor (solid) ⇌ Camphor (vapour) General Characteristics of Equilibrium Involving Physical Processes: At a given temperature, equilibrium can be achieved only in closed systems. If antagonistic reactions occur at the same rate then the system is said to be dynamic. Quantifiable properties in a system remain constant. Equilibrium for physical processes can be determined by constant values of one of its parameters. Equilibrium in Chemical Processes: Chemical equilibrium is reached when the rates of both forward and backward reactions are the same. Reversible Reactions A given reaction, A + B ⇌ C + D Is reversible in the sense that as the concentration of reactants decreases, the concentration of products formed will increase simultaneously. Irreversible Reactions In the given reaction, A + B → C+ D When the formed products cannot return to their reactant stages under the same conditions, it is an irreversible reaction. Such reactions do not show equilibrium and have a minimum Gibbs free energy. Dynamic Nature of Chemical Equilibrium: The reactants N2 and H2 in known quantities achieve equilibrium at a specific temperature during Haber’s process for producing ammonia. At equilibrium, N2, H2, and NH3 are in stable concentrations. Characteristics of Chemical Equilibrium: During equilibrium, reactants and products have constant concentrations. The dynamic nature of equilibrium is characterised by the equal rates of forwarding and backward reactions. Equilibrium can be achieved only if no solid products are permitted to get out of the reaction. Equilibrium Constant: In a general reversible reaction, where A & B are reactants and C & D are products, A + B ⇌ C + D Equilibrium constant, Kc = [C] [D] [A] [B] Unit of Kc (Concentrations) – molL-1 The Law of Chemical equilibrium states that, at a given temperature, the product of concentrations of the reaction products raised to their respective stoichiometric coefficients in the balanced chemical equation divided by the product of concentrations of the reactants raised to their stoichiometric coefficients has a constant value. For a general reversible reaction, aA + bB ⇌ cC + dD Kc = [C]c[D]d / [A]a[B]b Where, A, B, C, and D are the equilibrium concentrations of the reactants and products The product of the molar concentrations of the reactants, raised to their stoichiometric coefficients, divided by the product of the molar concentrations of the products, each raised to their stoichiometric coefficients, yields the equilibrium constant, which is a constant value. Characteristics of Equilibrium Constant: The value of the equilibrium constant for a given reaction does not change even if the direction from which the equilibrium was approached is changed. It is independent of the concentration of reactants with which the calculation is started. It depends only upon temperature. If a reaction is reversed, the value of KC is inverted. When the equation is divided by 2, Kc = √K When the equation is multiplied by 2, the new value of Kc = K2 The inclusion of a catalyst will not affect the value of equilibrium. Predicting the Extent of Reaction: The values of Kc help predict the dominant part of reactions : If Kc > 103 has high values, the reaction is forward dominant If Kc < 10-3 then the reaction is backwards dominant Moderate values ( 10-3 > Kc > 103 ) signify equilibrium in neither direction. Predicting the Direction of the Reaction- Reaction Quotient: The reaction quotient or QC helps to predict the direction of the reaction. It may not give us equilibrium values. aA + bB ⇌ cC + dD Qc = [C]c [D]d / [A]a[B]b Reaction proceeds in : The direction of reactants, when QC > KC The direction of products when QC < KC If QC = KC, the reaction mixture is already at equilibrium Calculating Equilibrium Concentrations: If initial concentrations are known, some steps can lead to finding equilibrium concentrations. Step 1. A balanced equation is written Step 2. Below the balanced equation, a list of each substance involved in that reaction is made Initial concentration Change in concentration on achieving equilibrium The equilibrium concentration. Assign x as the concentration (mol/L) of one of the substances that react after reaching equilibrium, and then use stoichiometry of the reaction to determine the concentrations of the other substances to find x. Step 3. Replace the
Ch 10 Gravitation
Ch 10 Gravitation Topics in the Chapter • Introduction• Newton’s Unversal law of Gravitation→ Relationship between Newton’s 3rd law and Newton’s law of gravitation→ Importance of universal law of gravitation• Free fall of an object and acceleration due to gravity→ Value of g→ Relationship between G and g• Mass• Weight• Difference between Mass and Weight• Factors that affect value of g• Thrust and Pressure• Buoyancy• Density• Archimede’s Principle→ Application of Archimede’s Principle• Relative density• Solved Numericals Introduction → Gravitational Force of Earth: If we release a small stone without pushing it from a height, it accelerates towards earth. → The stone is when accelerated towards earth, means some force is acting on it. The force which pulls the objects towards the centre of the earth is known as gravitational force of the earth. → Here, stone also attracts earth. It means every object in universe attracts every other object. Newton’s Universal Law of Gravitation → Sir Isaac Newton in 1687 proposed a law about the force of attraction between the two objects in the universe which is known as Newton’s law of gravitation.According to Universal law of Gravitation → Every mass in this universe attracts every other mass with a force which is directly proportional to the product of two masses and inversely proportional to the square of the distance between them. • Let masses (M) and (m) of two objects are distance (d) apart, then force of attraction (F) between themF ∝ M×mF ∝ 1/d2F ∝ Mm/d2F = (GMm)/d2 where,G is a constant and is known as Gravitational constant.Value of G = 6.67×10-11 Nm2/kg2G is called universal gravitational constant. → If unit of F is in Newton, m is in kg, d is in metre, then unit of G can be calculated as :G = (F×d2)/Mm, therefor unit will be Nm2/kg2 Relation between Newton’s third law of motion and Newton’s law of gravitation → According to Newton’s third law of motion, “Every object exerts equal and opposite force on other object but in opposite direction.” → According to Newton’s law of gravitation, “Every mass in the universe attracts the every other mass.” → In case of freely falling stone and earth, stone is attracted towards earth means earth attracts the stone. → But according to Newton’s third law of motion, the stone should also attract the earth. It is true that stone also attracts the earth with the same force F = m × a but due to very less mass of the stone, the acceleration (a) in its velocity is 9.8 m/s2 and acceleration (a) of earth towards stone is 1.65×10-24 m/s2 which is negligible and we cannot feel it. Importance of universal law of gravitation (i) The force that binds us to the earth.(ii) The motion of moon around the earth.(iii) The motion of earth around the sun.(iv) The tides due to moon and the sun. Free fall of an object and acceleration (g) → When an object is thrown upward, it reaches certain height, then it starts falling down towards earth. It is because the earth’s gravitational force exerts on it. → This fall under the influence of earth is called ‘free fall of an object’. → During this free fall direction do not change but velocity continuously changes which is called acceleration due to gravity. It is denoted by ‘g’. → Its unit is same as acceleration m/s2. Gravitational Acceleration and its value at the surface of earth → The uniform acceleration produced in a freely falling object due to the gravitational force of earth, is called acceleration due to gravity. → It is represented by ‘g’ and it always acts towards the centre of the earth. Value of ‘g’ on the surface of earth → The force acting on an object is F = (GMem)/R2 …. (i)where,Me = Mass of earthm = Mass of an objectR = Radius of earthIf acceleration due to gravity is ‘g’ due to force F then, F = m×g …. (ii)Relationship and difference between ‘G’ and ‘g’ G = Gravitational constantg = Acceleration due to gravityg = GM/R2Difference between G (Gravitational constant) and g (Acceleration due to gravity) Gravitation Constant (G) Gravitational acceleration (g) Its value is 6.67×10-11 Nm2/kg2. Its value is 9.8 m/s2. Its value remains constant always and everywhere. Its value varies at various places. Its unit is Nm2/kg2. Its unit is m/s2. It is a scalar quantity. It is a vector quantity. Example: If two stones of 150 gm and 500 gm are dropped from a height, which stone will reach the surface of earth first and why ? Explain your answer. Solution → It was Galileo, who first time demonstrated and depicted that the acceleration of an object falling freely towards earth does not depend on the mass of theobject. → It can be verified by universal law of gravitation. Let an object of mass m, is allowed to fall from a distance of R, from the centre of the earth. Then, the gravitational force, F = (GMem)/R2 (Me= Mass of the earth)The force acting on the stone is F = m×a∴ m × a = (GMem)/R2⇒ a = GMe/R2 → So, acceleration in an object falling freely towards earth depends on the mass of earth and height of the object from the centre of the earth. So, stones of mass 150 gm and 500 gm will reach the earth surface together. Equation of motion when an object is falling freely towards earth or thrown vertically upwards Case 1: When an object is falling towards earth with initial velocity (u) Velocity (v) after t seconds, v = u + ghtHeight covered in t seconds, h = ut + ½gt2Relation between v and u when t is not given: v2 = u2 + 2gh Case 2: When object is falling from rest position means initial velocity u=0 Velocity (v) after t seconds, v = gtHeight covered in t seconds, h = ½gt2Relation between v and u when t is not given: v2 = 2gh Case 3: When an object is thrown vertically upwards with initial velocity u, the gravitational acceleration
Ch 1 The Living World
Topics Covered In the Chapter • Introduction• What is ‘Living’?• Diversity in the Living World• Taxonomic Categories• Taxonomical Aids Introduction The life is life is full of amazing diversity of living organism. The diversity of habitats are very vast and deeply reflects on “What indeed is life”. This question has two implicit questions within it. The first is a technical one and seeks answer to what living is as opposed to the non-living, and the second is a philosophical one, and seeks answer to what the purpose of life is. What is Living? The main characteristics of living are:(i) Growth(ii) Reproduction(iii) Metabolism(iv) Cellular organization(v) Consciousness → Those characteristics which have no exception is called defining property of life. → Growth and Reproduction are not the defining property of life as well as metabolism, cellular organization, consciousness is the defining property of life. (i) Growth → Overall increase in mass or size of tissue or organism or its parts is called growth. → Increase in mass and increase in number are the twin characteristics of growth. This is an irreversible permanent increase in size of the organ or its part or even of an individual cell. → Growth is of two types: • Intrinsic growth: Growth from inside of the body of living organism. This is the defining property of life.• Extrinsic growth: Growth from outside of the body of the organism. Like accumulation of material on any body surface . Non-living exhibits this type of growth. → Intrinsic Growth is of two types: • Indeterminate growthUnlimited growth: Growth which occurs continuously throughout their life span. It occurs only in plants. • Determinate growth limited growth: Growth which occurs only up to certain age. It occurs only in animals. Cell division occurs only in certain tissues to replace lost cells. (ii) Reproduction → Production of new individual or progeny is called as reproduction. → Reproduction in case of multicellular organism is production of progeny possessing features more or less similar to those of parents. → Reproduction in case of unicellular organism like bacteria, unicellular algae or amoeba is increaser in number of cell. Means in unicellular organism the growth and reproduction are synonyms or same. → Reproduction is not found in any nonliving object. There are many living organism which cando not reproduce like mules, sterile human couples, worker bees. This is also not taken as defining property of life. → Reproduction is of two types: • Asexual reproduction: Reproduction in which fertilization or gametic fusion and meiosis is not involved is called asexual reproduction. (a) By Asexual spores: In algae and fungi.(b) By Budding: In Yeast and Hydra.(c) By Fragmentation: In filamentous Algae, Fungi and Protonema of moss plants.(d) By True Regeneration: Fragmented organism regenerate the lost parts of its body and becomes a new organism i.e. Planaria. → Regeneration is a process in which only lost part of the body is repaired or regenerated. Ex: Star fish, Lizards. • Sexual Reproduction: Reproduction in which gametes are formed by meiosis and fertilization takes place to form progeny is called as sexual reproduction. (iii) Metabolism → The sum total of all the chemical reaction occurring in our body is metabolism. → All organism, both unicellular as well as multicellular exhibit metabolism. No nonliving objects show metabolism. → It is the defining property of life. → The isolated metabolic reaction outside the body of an organism, performed in a test tube (in vitro) is neither living nor living. These isolated reactions cannot be regarded as living things, but they are definitely living reactions because they are similar to the reaction performing in our body. → All plants, animals, fungi, and microbes exhibit metabolism. (iv) Cellular organization → Cell is the basis unit of life. All organisms are composed of cells. → Some are composed of single cell and are called as unicellular organism while other are composed of many cells, are called multicellular organism. → Unicellular organism is capable of independent existence and performing essential functions of life. Anything less than a complete structure of a cell, does not ensure independent living. → Cell is the fundamental structure and functional structural and functional unit of all living organism. This is the defining property of life. Consciousness Ability to sense the surrounding environment and respond to these environment stimuli is called as consciousness. This is the most obvious and technically complicated features of all living organism. We sense these physical, chemical or biological stimuli through our sense organs. Plants also sense and respond to external factors like light, water, temperature, other organism, pollutants etc. All organisms from the prokaryotes to complex eukaryote show consciousness to environmental clues. Some common examples of consciousness can be seen in organism, like plants performs flowing in a particular seasons (photoperiodism), Some animals perform breeding in a particular season only (seasonal breeders), and all organism handle the chemicals entering their bodies etc. When human is concerned a very well developed nervous system and supreme level of skill of communication which is called as self-consciousness. Human is very fast to respond towards the external stimuli and even it can think or predict about possible changes of surrounding so it can prepare itself according to the surrounding situations. Further human can even change its surrounding situation up to a limit so this topmost or climax level of consciousness is regarded as self-consciousness, which cannot be seen elsewhere. Self –consciousness is thought to be present only in human. The brain dead coma patient who is supported who is supported by machines which replace heart and lungs also has consciousness so it is living but it does not has self-consciousness because it has lost the co-ordination of organs of different body parts. Means all the living phenomena are due to underlying interactions between different component of an individual or organ or tissue or cell. Living organism is self-replicating and self-regulating interactive system capable of responding to external stimuli. Adaptations and homeostasis are also very important characters of living. Diversity
