Syllabus of HSEB CHEMISTRY 11

Literally, ecology is the study of earth's households including the plants, animals, microorganisms and people that live together as interdependent components. Because, ecology is concerned not only with organisms but with energy flows and material cycles on the land, in the oceans, in the air and in the fresh water. Thus, the ecology is the totality of relations between organisms and environment.

An organism is always in the state of perfect balance with environment. The environment refers to the things and conditions around the organism which directly or indirectly influences the life and development of the organism and their population. Organisms react with each other and also with physical conditions that are present in their habitats. The organisms and physical features of the habitat form an ecological complex called ecosystem.

Ecosystem is the major ecological unit. It has both structure and functions. The structure is related with species diversity and function of ecosystem is related with the flow of energy and cycling of materials through structural components of ecosystem. The ecosystem is the basic functional unit of the organisms and their environment interacting with each other and with their own components.

Different types of ecosystem of nature consisting giant ecosystem called the biosphere. These may be categorized as

These are operated by themselves under natural conditions without any interference by men. Based upen the particular kind of habitat, these are further divided as:-

I. Terrestrial Ecosystem: as forest ecosystem, grassland ecosystem, desert ecosystem

II. Aquatic Ecosystem:

i. Freswater: which may be lotic(running water as spring, stream or river) or

lentic( pool, lake or pond)

ii. Marine: such as deep bodies, oceans, sea, estuarine(river mouth in sea)

Temperature effects plants and animals in various ways which are as follows:

a. Effects on metabolism: All metabolic process are influenced by temperature. Since temperature regulates all the activities in the body of the organism are controlled by the temperature it affects rate of transpiration, photosynthesis, in plants and respiration rates and other metabolic processes in plants as well as in animals. In plants it affects the seed germination.

b. Effects on reproduction: Flowering in plants is affected by temperature through thermoperiodism (response of plant to rhythmic diurnal fluctuations in temperature. In animals maturation of gonads of sex cells and the liberation of gametes takes place at the particular temperature which varies from species to species. Breeding of some animals occurs only in summer or in winter. In blow fly the number of eggs laid per female increase with increase with temperature upto 32.5 C. But number decreases in further decrease in temperature. Thus, temperature affects fecundity(the reproductive capacity)

c. Effect on growth and development: Both extremely low and high temperature have adverse effects on the growth of plants. Low temperature brings cold injuries such as desiccation (tissue are dehydrated due to rapid transpiration and slow absorption during winter), chilling injuries (killing or injury of hot plants when exposed to lower temperature for sometime) and freezing injuries ( in some plants of temperate climate, if exposed to low temperature; water is frozen into crystals in the intercellular space causing injuries to plants). Some perennials can tolerate extremely low temperature and this ability is called resistance.

In animals also temperature effects the growth as well as development. For e.g. in Oyster the body length increases from 1.5mm to 10.3mm with an increase in temperature from 10C to 20C. Sea-urchin shows maximum size of its body in warmer water, corals also do not fluorish well when water temperature drops below 21C

d. Effects on crossing over: In animals like fruitflies Drosophilla sps (bee) temperature is shown to effect the crossing over and somatic expressions of gene characters. Development of wings, eyes, etc are affected if larva, pupa etc are kept at low or high temperature. Wings tend to be longer and shorter at low temperatures.

e. Effects on sex-ratio: In some animals, Daphnids, sex ratio is affected by temperature.

Under normal conditions Daphnids give pathogenic eggs that develop into female whereas in high temperature they give sexual eggs which after fertilization develops into male or female.

f. Effect on duration: In some insects, birds and mammals in humid climates bear darker pigments that the races of same species present in cool and dry climates(gloger rule). In frog Hyla and horned toad more temperature induce darkenings.

g. Effects on morphology: Temperature also affect the absolute size of an animal and the relative properties of various body parts (Bergman's rule). Birds and mammals attain greater body size in the cold regions than in warm areas. The tails, ears and legs of mammals are relatively shorter in cold regions than in warmer areas (Allen's rule). Temperature also affects the morphology of some fishes and is found to have some relationship with the number of vertebrates.

Though its effects an organism in various ways described above temperature affects geographical distribution of plants and animals.

Rainfall is the chief source of soil water. The water available to plants and animals from soil comes as a result of rainfall through its hydrological cycle. Precipitation occurs in various forms as drizzle (minute drops appearing in air) rain (drops in liquid water), snow, dew and frost, sleet( is in the form of small grain of ice), hails (balls of ice). Snow is injurious to plants breaking branches, flowers and fruits. Hail and sleet also cause similar damage. It also affect the humidity of the atmosphere.

The amount of annual rainfall greatly influence the vegetation and animal population of a particular region. Rainfall distribution in different seasons of the year also may further be important in regional distribution of vegetation.

High mountain region are correlated with distribution of rainfall. Annual rainfall determines the type of vegetation in any region. For e.g.: in tropical areas with heavy rainfall throught the year main vegetation are evergreen forest.

Atmosphere in the form of invisible vapour is known as humidity. The humidity of air is expressed in terms of relative humidity values. Humidity is greatly influenced by intensity of solar radiation, temperature, altitude, wind, exposure, cover, water and status of soil. High temperature increases the capacity of air to retain moisture and cause lower humidity. Low temperaure cause higher relative humidity by releasing the capacity of air for moisture.

Daily variation in relative humidity value depend upon the type of habitat conditions. In plains and deserts it may show variations during day whereas in oceanic islands there is a little variation throughout the year.

Process of treanspiration, absorption of water, etc are influenced by the atmospheric humidity. Saturation deficit, temperature and wind velocity modify evaporation-transpiration rates. Saturation deficit in mm Hg is the difference between the pressure of water vapour in atmosphere at a given time and the maximum vapour pressure that it could contain in same temperature. Decrease or increase in saturation deficit causes a fall or rise in evaporation rate respectively. Similarly temperature variation also influences evaporation. Dry wind decrease the amount of air moisture by removing moist air about plants and mixing it with dry air which decrease the humidity and increases the transpiration.

Some plants as orchids, lichen, mosses, etc make direct use of atmospheric moisture. In fungi and other microbes, it play an important role in germination of spores and subsequent stages in life cycle.

Air in motion is called wind. It is an important ecological factor of the atmosphere as it affects plant's life mainly on flat plains, along sea coast and at high altitudes in mountains. Wind is directly involved in transpiration in causing several types of mechanical damage and dissemination of pollens, seeds and fruit. It also modifies the water relations and water content of a particular area. The velocity of wind is affected by such factors as geographic situation, topography, vegetation and position. Effects of wind are much pronounced in plants along the sea coast and at high altitudes on mountains. Air moves from a region of high pressure to the region of low pressure. The equatorial regions receive more heat than north or south regions. Thus low pressure occurs at low latitudes. The air generally moves from a poles towards equator.

Wind brings about a number of physical, anatomical and physiological effects on plants which are as follows: -

A wind of much high velocity may cause the breaking of living branches of trees and sometimes even their complete uprooting. However in forest where the canopies(different strata) of individual trees at different heights reduce the velocities of wind to about 80%. Such effects are uncommon. Thus, such vegetation in forest serves as wind break. Sometimes special trees and shrubs provide protection against wind for fields buildings of livestock. Usually violent winds may cause breakage of soft woods of such plants as cotton, single trees or groups of trees which are uprooted in forest and often known as wind throws of wind falls.

Strong winds from a constant direction sometimes cause permanent alternation in the form and position of shoots. Deformation is very common in trees growing on ridges and along coast.

3. Lodging: It is a type of wind injury common in grasses as wheat, maize, sugarcane, etc where violent winds cause the flattening of this herbaceous plants.

4. Abrasion: Particles of soils or ice carries by the wind may act as strong abrasive force by which buds and other parts of plants may be eroded away. Crops grown on sandy soils usually suffer with such damage.

5. Erosion and Deposition: The roots of plants whose covers are very thin may be exposed as the soil is generally eroded out by strong wind. Moreover where the additional soils are deposited become unsuitable for plants growing there.

6. Salt spray: Along sea coasts, the salts of water are carried along by strong winds in the near of the ocean. Such salts have injurious effect on plants growing there.

7. Wind is an important agent for the dispersal of pollen grains, fruits seeds and spores of the plant. Thus, it plays an important role in local distribution in plant species or communities of plants.

1. In the areas subjected to strong winds, the leaves of plants become small and grown. The diameter of the trunk in the direction of wind becomes greater. The plants in such areas show extensive development of mechanical tissues which provide mechanical support and shape the plants from wind injuries.

2. Wind increases the water loss by constantly removing the air saturated with water vapour from the intercellular spaces of the leaves and bringing unsaturated air contact with leaves and shoots causing desiccation(means plants fail to maintain an internal water balance).

3. Plants growing under the influence of dry winds generally suffer from dehydration and consequent loss of turgidity. Under these conditions their organs become dwarfed. This is common in trees of sea coast, arctic and alpine timberland.

Except those fires caused by lightening or volcanic activities which are rare and confined only to certain specific areas, most of the fire very common in most of the regions are of biological origin. These are mostly man caused and sometimes chiefly in forest due to mutual friction between tree surfaces. E.g. bamboo. Fires are classified as: -

1. Ground Fire: Which develop in such conditions where organic matter richly accumulates and they catch fire. These fires are flameless and subterranean (underground) and kill almost all plants rooted in the burning materials except some woody species.

2. Surface Fire: which sweep over the ground surface rapidly and their flames consume the litter living herbaceous vegetation and shrubs.

3. Crown Fire: Which are most destructive burning the forest canopy, surface debris and bringing about vegetation destruction in large scale.

In addition to its direct lethal(killing) effects on plants, fire also effects them indirectly as in following ways:

1. Some trees as a result of injury by fire have large scars on their stems. Such scars may serve as suitable path of entry of parasitic fungi and insects.

2. Fires bring about marked alternation of such environmental factors as light, rainfall, nutrient cycle, fertility of soils and humus content of soil, pH and soil funna. Sometimes the habitat needs thousands of years in the return of normal conditions. The natures of such alternations depend only on the nature of fire.

3. Fire plays an important role in the removal of competition for surviving species. Such species that fortunately survive fire(fire tolerant) generally increase in abundance at the expense of those killed by fire( by fire sensitive). As a result of considerable reduction in competition and possibly due to alternation in other condition.

4. Some plants as Populus sps. stimulated to growth by fire. A number of grasses like Cyanodon dactylon are stimulated by fire to produce large quantities of seed. In some grasses and some legumes the seeds would germinate only after these get fire treatment.

5. Some fungi mainly Ascomycetes grow in soils of burnt area. Such fungi are known as pyrophilous.

The soil acidity is associated with the present of hydrogen ion concentration. It is expressed is the form of pH which is defined as the negative logarithmic

to mean effective concentration. pH values of soil show much correlation with the soil type, vegetation type, profile origin, thus affecting plants growth time requirement and mineral nutrition.

The pH values of natural soil show much variation ranging from 3.0 to 9.4. However extreme values do occur. Pearsal (1952) suggested some boundary pH values which are ecologically significant. Plants regarded as calcicoles usually occur in soil with pH 6.5 whereas calcifuges in those with pH value 3.8-4.0.

1) Soil pH strongly affects the microbial activities as follows:

In pH 5.0 bacteria as well as fungal activities are reduced. Some soil born diseases like root rot of cotton, potato scrab, etc. Merely controlled by lowering the pH of soil whereas others like club roots of Crucifer by increasing the soil pH.

2) Some plants grow on soils with high concentration. Some plants are known as halophytes as some mosses and ferns. In arid regions (with low rainfall) where evaporation rates exceed precipitation. Soil become generally saline (salty). Salinity brings about marked physiological effects on plants affecting osmotic concentration of cells. Most of the halophytes show xerophytic tendencies and vivipary (i.e. germination of seed before the fruit is shed from the parent plants. Aquatic organisms also have problem of water regulation. Salinity of water is relevant as a comparison between freshwater and marine species will reveal relatively few plants and animals can withstand large fluctuation in salinity for example snail can survive a range of salinities from 50-1600 m mol dm^-3 of sodium chloride.

1) As a raw material for photosynthesis an increase in carbondioxide concentration upto about 1% increases the rate of photosynthesis but very high concentration may prove toxic and the rate of photosynthesis will go down.

2) An increase in CO2 concentration in atmosphere may result into adverse effects, green house effect (preventing the heat from being reradiated in outer space results rise in temperature of earth).

3) Higher CO2 levels with a poorly oxygenated water kills fishes and other animals.

4) It forms the component of soil air. Carbondioxide and oxygen make up 21% and Nitrogen 71%. Soil air is very important for growth of roots, seed germination and microbial activity. Poor soil aeration supresses root hair development and may reduce rates of absorption of water and nutrients.

5) An increase in carbondioxide in hot tropical climates acts as fertilizers.

6) Higher concentration of carbondioxide in the atmosphere especially in poorly aerated soil has retarding effect on the rate of respiration.

1) Oxygen is required for aerobic respiration. In complete absence of oxygen anaerobic respiration takes place while aerobic respiration stops. Except in anaerobic respiration, continuous absence of oxygen for very long period will ultimately cause the death of the living organisms.

2) It is the component of soil complex, soil is very important for the growth of roots, seed germination and microbial activities.

3) Biological Oxygen Demand (BOD) is the amount of oxygen required for biological oxidation by microbes in any unit volume of water. The test is done at 20C for at least 5 days. BOD is proportional to the amount of organic waste present in water. BOD values are useful for self purification capacity of a water body and form possible control measure of pollution. The quantity of oxygen in water (dissolved oxygen) along with BOD is indicated by the kind of organism present in water. Decrease in OD value may lead to increase in anaerobic bacteria. Depletion of oxygen in water leads to die aquatic plants and animals.

Edaphic factor include the structure and composition of soil

Under natural situations organisms live together influencing each other's life directly or indirectly. Such vital processes as growth, nutrition and reproduction depend very much upon the interactions between the individuals of same species (intraspecific interaction) or between those of different species (interspecific interaction). Pollination, seed and fruit dispersal, grazing, parasitism, symbiosis are the common examples of such interactions. Under natural conditions we find interdependencies between plant as well as between plants and animals, between animals. Moreover, interdependency may exist between species, which are taxonomically widely different such as between trees and bacteria. The relationship between species may be beneficial to both, harmful to both, or beneficial or harmful to one and neutral for other.

Plants and animals exhibit a wide range of relationship. Individuals of one species interact with the other individuals of the same species and those of other species. There are various types of interactions including in two heading.

It is an interaction that is beneficial to both species. In such association, there occurs a close and often permanent and obligatory contact more or less essential for the survival of each. The two populations enter into same sort of physiological exchange. The following are some common examples of mutualism.

1} Pollination by animals:- Bees, butterflies derive food from the nectar or other plant product and in return bring about pollination.

2} Dispersal of fruits and seed:- Seeds and fruits are commonly transported by animals. The fruits are eaten by birds, mammals and seeds content in them are dropped in the excreta at various places.

3} Lichen(Association with algae and fungi):- Mutualism is permanent as well as obligatory. The body is made up of matrix of fungi within the cells of which an alga is embedded. Fungus makes moisture as well as minerals available whereas alga manufactures food. Neither of the two can grow alone independently in nature.

4} Symbiotic nitrogen fixers:- Where the bacterial Rhizobium forms the nodules in the roots of leguminous plants and lives symbiotically with the host. Bacterium obtains fruit from the higher plants in turn fix gaseous nitrogen making it available to plants.

5} Mycorrhiza:- This is also an example of similar nutrition in fungi that form mycorrhizal structure either inside the root and or on outside surface of plants.

6} Some unicellular plants esp. algae known as Zoochlorella lives symbiotically in the outer tissues of certain sponges, coelenterates, molluscs and worms.

7} There are associations between animals themselves for example termites which feed on woods and protozoans present in their gut. Termites cannot digest cellulose and in return obtain food and shelter from the termites.

In this association between members of different species only one is benefitted and neither is harmed. Here two of more populations live together without entering into any kind of physiological exchange. One is benefitted without any effect on the other. e.g. Linnas. These are vascular plants rooted in the ground and maintain erectness of their stems by making use of their objects for supports. Epiphytes are plants growing on other plants. These use other plant as support and not for water and food supply. e.g. Orchid. There are several commensals that make temporary contact with other organisms. e.g. monkeys, treefrogs, snakes, insects, etc. use trees and other plants for substratum, shelter and breeding sites.