UNIT IX: Plant Ecology Chapter 6 Principles of Ecology
Learning Objectives • How soil, climate and other physical features aff ect the fl ora and fauna or vice versa? Th e learner will be able to Th ese questions can be better answered with Understand the interaction between the study of ecology. organisms and their Ecology is essentially a practical science environment. involving experiments, continuous Describe biotic and observations to predict how organisms react abiotic factors that to particular environmental circumstances infl uence the dynamics of and understanding the principles involved in populations. ecology. Describe how organisms adapt themselves to environmental changes. 6.1 Ecology Learn the structure of various fruits and The term “ecology” seeds related to their dispersal mechanism. (oekologie) is derived from two Greek words – oikos (meaning house or dwelling Chapter outline place and logos meaning study) It was first proposed by 6.1 Ecology R. Misra Reiter (1868). However, the 6.2 Ecological factors most widely accepted definition of ecology was 6.3 Ecological adaptations given by Ernest Haeckel (1869). 6.4 Dispersal of seeds and fruits Alexander von Humbolt - Father of Ecology Ecology is a division of biology which deals Eugene P. Odum - Father of morden Ecology with the study of environment in relation to R. Misra - Father of Indian Ecology organisms. It can be studied by considering individual organisms, population, community, biome or biosphere and their environment. 6.1.1 Definitions of ecology While observing our different environments, “The study of living organisms, both plants and one can ask questions like animals, in their natural habitats or homes.” - Reiter (1885) • Why do plants or animals vary with places? “Ecology is the study of the reciprocal •What are the causes for variation in relationship between living organisms and their biological diversity of diff erent places? environment.” - Earnest Haeckel (1889)
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 136 01-03-2019 17:00:30 6.1.2 Ecological hierarchy habitat and niche of any organism is called Ecotope The interaction of Biosphere organisms with their The differences between habitat and niche are environment results in Biome as follows. the establishment of grouping of organisms Landscape Habitat Niche which is called ecological 1. A specific A functional space hierarchy or ecological Ecosystem physical space occupied by an levels of organization. occupied by organism in the same The basic unit of an organism eco-system Community ecological hierarchy is (species) an individual organism. 2. Same habitat A single niche is Population The different hierarchy may be shared by occupied by a single of ecological systems is many organisms species Individual organism illustrated below: (species) 3. Habitat Organisms may 6.1.3 Branches of Ecology: specificity is change their niche Ecology is mainly divided into two branches, exhibited by with time and season. they are autecology and synecology. organism. 1. Autecology is the ecology of an individual Table 6.1: Difference between habitat and niche species and is also called species ecology.
2. Synecology is the ecology of a population or Applied ecology or community with one or more species and also environmental technology : called as community ecology. Application of the Many advances and developments in the field Science of ecology is ecology resulted in various new dimensions otherwise called as Applied ecology or and branches. Some of the advanced fields are Environmental technology. It helps us to Molecular ecology, Eco technology, Statistical manage and conserve natural resources, ecology and Environmental toxicology. particularly ecosystems, forest and wild 6.1.4 Habitat and Niche life conservative and management. Environmental management involves Habitat Bio-diversity conservation, Ecosystem Habitat is a specific physical place or locality restoration, Habitat management, occupied by an organism or any species which Invasive species management, Protected has a particular combination of abiotic or areas management and also help us plan environmental factors. But the environment of landscapes and environmental impact any community is called Biotope. designing for the futuristic ecology. Niche An ecological niche refers to an organism’s place 6.1.5 Ecological equivalents in the biotic environment and its functional Taxonomically different species occupying role in an ecosystem. The term was coined by similar habitats (Niches) in different geographical the naturalist Roswell Hill Johnson but Grinell regions are called Ecological equivalents. (1917) was probably first to use this term. The
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 137 01-03-2019 17:00:30 Examples:
• Certain species of epiphytic orchids of Sun light Western Ghats of India differ from the Precipitation epiphytic orchids of South America. But they are epiphytes. Carbon • Species of the grass lands of Western Ghats dioxide and Water vapour Climatic factors of India differ from the grass species of Wind temperate grass lands of Steppe in North America. But they are all ecologically primary producers and fulfilling similar
roles in their respective communities. Biotic factors Grazing animals Birds Rodents Insects Plant Pathogens 6.2 Ecological factors Man Epiphytes Many organisms, co-exist in an environment. Soil slope Edaphic factors The environment (surrounding) includes Soil water Minerals physical, chemical and biological components. Physical nature When a component surrounding an organism of the soil affects the life of an organism, it becomes a Soil air factor. All such factors together are called Figure 6.1: Environmental factors affecting a plant environmental factors or ecological factors. a. Light These factors can be classified into living Light is a well known factor needed for the (biotic) and non-living (abiotic) which make basic physiological processes of plants, such as the environment of an organism. However the photosynthesis, transpiration, seed germination ecological factors are meaningfully grouped and flowering. The portion of the sunlight which into four classes, which are as follows: can be resolved by the human eye is called i. Climatic factors visible light. The visible part of light is made- ii. Edaphic factors up of wavelength from about 400 nm (violet) to 700 nm (red). The rate of photosynthesis is iii. Topographic factors maximum at blue (400 – 500 nm) and red (600 – iv. Biotic factors 700 nm). Thegreen (500 – 600 nm) wave length We will discuss the above factors in a concise of spectrum is less strongly absorbed by plants. manner. Effects of light on plants Flowers of poppy, chicory, dog rose and many other Light regulates Stem and plants, blossom before the Leaf formation Photosynthesisd break of dawn (4 – 5 am), a s ProductionRunner evening primrose open up with the onset Opening an Closing of stomat
of dusk (5 – 6 pm) due to diurnal rhythm. Movements Tuber formation Tuber
Germination of seedFlowering 6.2.1 Climatic Factors Climate is one of the important natural factors controlling the plant life. The climatic factors includes light, temperature, water, wind and Figure 6.2: Various effects of light upon a fire. green plant
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 138 01-03-2019 17:00:32 Based on the tolerance to intensities of light, 1. Eurythermal: Organisms which can tolerate the plants are divided into two types. They are a wide range of temperature fluctuations.
1. Heliophytes - Light loving plants. Example: Zostera (A marine Angiosperm) and Example: Angiosperms. Artemisia tridentata. 2. Sciophytes - Shade loving plants. 2. Stenothermal: Organisms which can Example: Bryophytes and Pteridophytes. tolerate only small range of temperature variations. Example: Mango and Palm In deep sea (>500m), the environment is (Terrestrial Angiosperms). dark and its inhabitants are not aware of the Mango plant donot and cannot grow in existence of celestial source of energy called Sun. What, then is their source of energy? temperate countries like Canada and Germany. Thermal Stratification Palaeoclimatology–Helps to It is usually found in aquatic habitat. The reconstruct past climates of change in the temperature profile with our planet and flora, fauna increasing depth in a water body is called and ecosystem in which they thermal stratification. There are three kinds lived. Example: Air bubbles trapped in ice of thermal stratifications. for tens of thousands of years with fossilized pollen, coral, plant and animal debris. Epilimnion b. Temperature Metalimnion Temperature is one of the important factors which affect almost all the metabolic activities Hypolimnion of an organism. Every physiological process in an organism requires an optimum temperature at which it shows the maximum metabolic rate. Figure 6.3: Thermal stratification of pond Three limits of temperature can be recognized 1. Epilimniotn – The upper layer of warmer for any organism. They are water. 1. Minimum temperature - Physiological 2. Metalimnion – The middle layer with a activities are lowest. zone of gradual decrease in temperature. 2. Optimum temperature - Physiological 3. Hypolimnion - The bottom layer of colder activities are maximum. water. 3. Maximum temperature - Physiological Temperature based zonation activities will stop. Variations in latitude and altitude do affect the Based on the temperature prevailing in temperature and the vegetation on the earth an area, Raunkiaer classified the world’s surface. The latitudinal and altitudinal zonation vegetation into the following four types. They of vegetation is illustrated below: are megatherms, mesotherms, microtherms and hekistotherms. In thermal springs and deep sea Latitude: Latitude is an angle which ranges hydrothermal vents where average temperature from 00 at the equator to 900 at the poles. exceed 100oc. Altitude: How high a place is located above Based on the range of thermal tolerance, organisms are divided into two types. the sea level is called the altitude of the place.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 139 01-03-2019 17:00:33 c. Water Water is one of the most important climatic Ice/ Tundra factors. It affects the vital processes of all living Snow organisms. It is believed that even life had originated only in water during the evolution of forest Tree line Coniferous Earth. Water covers more than 70% of the earth’s Deciduousforest surface. In nature, water is available to plants in Grassland or desert three ways. They are atmospheric moisture,
EQUATOR Tropical precipitation and soil water. rain forest Figure 6.4: Latitudinal zonation of vegetation Evergreen forests – Found type where heavy rainfall occurs throughout the year. 14,500' Snow 13,000' 12,000' Tundra Sclerophyllous forests – 10,000' Found where heavy rainfall occurs during Coniferous winter and low rainfall during summer. 7500' forest 6500' Deciduous forest 4000' 3000' The productivity and distribution of plants depend 1800' Grassland or desert 1300' upon the availability of water. Further the quality Tropical rain forest of water is also important especially for the aquatic Figure 6.5: Altitudinal zonation of vegetation organisms. The total amount of water salinity in different water bodies are :i).5% in inland water Timber line / Tree line : It is an imaginary (Fresh water) ii).30 – 35% in sea water and iii). line in a mountain or higher areas of land More than 100% in hypersaline water (Lagoons) that marks the level above which trees do Based on the range of tolerance of salinity, not grow. The altitudinal limit of normal tree organisms are divided into two types. growth is about 3000 to 4000m. 1. Euryhaline: Organisms which can live in water with wide range of salinity. Examples: Effects of temperature Marine algae and marina angiosperms The following physiological processes are 2. Stenohaline: Organisms which can withstand influenced by temperature: only small range of salinity. Example: Plants of • Temperature affects the enzymatic action estuaries. of all the bio-chemical reactions in a plant Environmental Terminology body. factor
• It influences CO2 and O2 solubility in the Stenothermal Eurythermal Temperature biological systems. Increases respiration Stenohaline Euryhaline Salinity and stimulates growth of seedlings. Stenoecious Euryoecious Habitat selection • Low temperature with high humidity can (niche) spread diseases to plants. Stenohydric Euryhydric Water • The varying temperature with moisture Stenophagic Euryphagic Food determines the distribution of the Stenobathic Eurybathic Depth of water / vegetation types. habitat Table 6.2: Tolerance of Environmental factor
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 140 01-03-2019 17:00:34 Examples of tolerance to toxicity Effects of wind i. Soyabean and tomato manage to tolerate • Wind is an important factor for the presence of cadmium poisoning by isolating formation of rain cadmium and storing into few group of cells • Causes wave formation in lakes and ocean, and prevent cadmium affecting other cells . which promotes aeration of water ii. Rice and Eichhornia (water hyacinth ) tolerate • Strong wind causes soil erosion and reduces cadmium by binding it to their proteins. soil fertility These plants otherwise can also be used to • Increases the rate of transpiration remove cadmium from contaminated soil ,this • Helps in pollination in anemophilous plants is known as Phytoremediation. • It also helps in dispersal of many d. Wind fruits, seeds, spores, Air in motion is called wind. It is also a etc. vital ecological factor. The atmospheric air • Strong wind may contains a number of gases, particles and cause up-rooting of other constituents. The composition of gases big trees in atmosphere is as follows: Nitrogen -78% , • Unidirectional Oxygen -21%, Carbon-di-oxide -0.03%, Argon wind stimulates the and other gases - 0.93%. The other components development of flag of wind are water vapour, gaseous pollutants, Figure 6.6: Flag forms in trees. dust, smoke particles, microorganisms, form in trees pollen grains, spores, etc. Anemometer is the e. Fire instrument used to measure the speed of wind. Fire is an exothermic factor caused due to the chemical process of combustion, releasing heat Green House Effect and light. It is mostly man-made and some- Albedo Effect times develops naturally due to the friction Gases let out to atmosphere between the tree surfaces. Fire is generally causes climatic change. divided into Emission of dust and aerosols (small solids 1. Ground fire – Which is flameless and or liquid particles in suspension in the subterranean. atmosphere) from industries, automobiles, 2. Surface fire – Which consumes the herbs
forest fire, So2 and DMS (dimethyl sulphur) and shrubs. play an important role in disturbing the 3. Crown fire – Which burns the forest canopy. temperature level of any region. Aerosols Effects of fire with small particles is reflecting the • Fire has a direct lethal effect on plants solar radiation entering the atmosphere. • Burning scars are the suitable places for the This is known as Albedo effect. So it entry of parasitic fungi and insects reduces the temperature (cooling) limits, • It brings out the alteration of light, rainfall, photosynthesis and respiration. The nutrient cycle, fertility of soil, pH, soil flora sulphur compounds are responsible for and fauna acid rain due to acidification of rain water and destroy the ozone. • Some fungi which grow in soil of burnt areas called pyrophilous. Example: Pyronema confluens.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 141 01-03-2019 17:00:34 Soil types Indicators of fire – Pteris ( fern ) and Pyronema (fungus) indicates the burnt up Based on soil formation (pedogenesis), and fire disturbed areas. So they are called the soils are divided into indicators of fire. 1. Residual soils –These are soils formed by weathering and pedogenesis of the rock. Fire break – It is a gap made in the vegetation 2. Transported soils – These are transported that acts as a barrier to slow down or stop the by various agencies. progress of fire. The important edaphic factors which affect A natural fire break may occur when there vegetation are as follows: is a lack of vegetation such as River, lake and 1. Soil moisture: Plants absorbs rain water canyon found in between vegetation may act and moisture directly from the air as a natural fire break. 2. Soil water: Soil water is more important Rhytidome: It is the structural defense by than any other ecological factors affecting the plants against fire .The outer bark of trees distribution of plants. Rain is the main source which extends to the last formed periderm is of soil water. Capillary water held between called Rhytidome. It is composed of multiple pore spaces of soil particles and angles layers of suberized periderm, cortical and between them is the most important form of phloem tissues. It protects the stem against water available to the plants. fire , water loss, invasion of insects and 3. Soil reactions: Soil may be acidic or prevents infections by microorganisms. alkaline or neutral in their reaction. pH value of the soil solution determines the availability 6.2.2 Edaphic factors of plant nutrients. The best pH range of the soil Edaphic factors, the abiotic factors related for cultivation of crop plants is 5.5 to 6.8. to soil, include the physical and chemical 4. Soil nutrients: Soil fertility and productivity composition of the soil formed in a particular is the ability of soil to provide all essential area. The study of soils is called Pedology. plant nutrients such as minerals and organic The soil nutrients in the form of ions. Soil is the weathered superficial layer of the 5. Soil temperature: Soil temperature of an Earth in which plants can grow. It is a complex area plays an important role in determining composite mass consisting of soil constituents, the geographical distribution of plants. Low soil water, soil air and soil organisms, etc. temperature reduces use of water and solute absorption by roots. Soil formation 6. Soil atmosphere: The spaces left between Soil originates from rocks and develops gradually soil particles are called pore spaces which at different rates, depending upon the ecological contains oxygen and carbon-di-oxide. and climatic conditions. Soil formation is 7. Soil organisms: Many organisms existing initiated by the weathering process. Biological in the soil like bacteria, fungi, algae, weathering takes place when organisms like protozoans, nematodes, bacteria, fungi, lichens and plants help in the insects, earthworms, etc. are breakdown of rocks through the production of called soil organisms. acids and certain chemical substances.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 142 01-03-2019 17:00:34 Horizon Description O–Horizon It consists of fresh or partially decomposed (Organic horizon) organic matter. Humus O1 – Freshly fallen leaves, twigs, flowers and fruits O2 – Dead plants, animals and their excreta decomposed by micro-organisms. Usually absent in agricultural and deserts. A–Horizon It consists of top soil with humus, living creatures (Leached horizon) and in-organic minerals. Topsoil - Often rich in A1 – Dark and rich in organic matter because of humus and minerals. mixture of organic and mineral matters. A2 – Light coloured layer with large sized mineral particles. B-Horizon It consists of iron, aluminium and silica rich clay (Accumulation horizon) organic compounds. (Subsoil-Poor in humus, rich in minerals) C - Horizon (Partially It consists of parent materials of soil, composed weathered horizon) of little amount of organic matters without life Weathered rock forms. Fragments - Little or no plant or animal life. R – Horizon It is a parent bed rock upon which underground (Parent material) water is found . Bedrock Figure 6.7: Soil Profile Soil Profile Loamy soil is ideal soil for cultivation. It Soil is commonly stratified into horizons at consists of 70% sand and 30% clay or silt or both. different depth. These layers differ in their physical, chemical and biological properties. It ensures good retention and proper drainage This succession of super-imposed horizons is of water. The porosity of soil provides adequate called soil profile. aeration and allows the penetration of roots. Types of soil particles Based on the water retention, aeration and Based on the relative proportion of soil particles, mineral contents of soil, the distribution of four types of soil are recognized. vegetation is divided into following types. Soil type Size Relative proportion 1. Halophytes: Plants living in saline soils 1 Clayey Less than 50% clay and 50% 2. Psammophytes: Plants living in sandy soils soil 0.002 silt ( cold / heavy 3. Lithophytes: Plants living on rocky surface mm soil ) 4. Chasmophytes : Plants living in rocky crevices 2 Silt soil 0.002 to 90% silt and 10% 0.02mm sand 5. Cryptophytes : Plants living below the soil 3 Loamy 0.002 to 70% sand and 30 surface soil 2mm % clay / silt or both 6. Cryophytes: Plants living in ice surface (Garden soil) 7. Oxylophytes: Plants living in acidic soil 4 Sandy 0.2 to 2 85% sand and 15% 8. Calciphytes: Plants living in calcium rich soil mm clay ( light soil ) alkaline soil. Table 6.3: Types of soil particles
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 143 01-03-2019 17:00:35 Hollard –Total soil water content Ecotone - The transition zone between two Chresard –Water available to plants ecosystems. Example: The border between Echard – Water not available to plants forest and grassland. Edge effect – Those species are found in 6.2.3 Topographic factors the ecotone areas are due to the effect of The surface features of earth are called environment of the two habitats. This is called topography. Topographic influence on the edge effect. Example: Owl in the ecotone area climate of any area is determined by the between forest and grassland. interaction of solar radiation, temperature, The two faces of the mountain or hill receive humidity, rainfall, latitude and altitude. It affects different amount of solar radiation, wind action the vegetation through climatic variations in and rain. Of these two faces, the windward region small areas (micro climate ) and even changes possesses good vegetation due to heavy rains and the soil conditions. Topographic factors include the leeward region possesses poor vegetation due latitude, altitude, direction of mountain, to rain shadows (rain deficit). steepness of mountain etc. Similarly in the soil of aquatic bodies like a. Latitudes and altitudes ponds the center and edge possess different Latitudes represent distance from the equator. depth of water due to soil slope and different Temperature values are maximum at the equator wave actions in the water body. Therefore, and decrease gradually towards poles. Different different parts of the same area may possess types of vegetation occur from equator to poles different species of organisms. which are illustrated below. c. Steepness of the mountain The steepness of the mountain or hill allows the rain to run off. As a result the loss of water causes water deficit and quick erosion of the top soil resulting in poor vegetation. On the other hand, the plains and valley are rich in vegetation due to the slow drain of surface water and better retention of water in the soil.
Clouds Figure 6.8: Latitudinal and Altitudinal Vegetation Height above the sea level forms the altitude. At high altitudes, the velocity of wind remains high, temperature and air pressure Moist decrease while humidity and intensity of light Rain winds increases. Due to these factors, vegetation at
different altitudes varies, showing distinct Rich vegetation zonation.
b. Direction of Mountain Poor vegetation North and south faces of mountain or hill possess Sea different types of flora and fauna because they differ in their humidity, rainfall, light intensity, light duration and temperature regions. Figure 6.9: Steepness of mountain
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 144 01-03-2019 17:00:36 6.2.4 Biotic factors Other examples: Nodules The interactions among living organisms • Water fern such as plants and animals are called biotic (Azolla) and Root hair factors, which may cause marked effects upon Nitrogen fixing vegetation. The effects may be direct and indirect Cyanobacterium Bacteria and modifies the environment. The plants (Anabaena ). mostly which lives together in a community • Anabaena and influence one another. Similarly, animals in present in Figure 6.10: association with plants also affect the plant life coralloid A nodulated legume in one or several ways. The different interactions roots of Cycas. plant root with bacteria among them can be classified into following two (Gymnosperm) types they are positive interaction and negative • Cyanobacterium (Nostoc) found in the interaction thalloid body of Anthoceros.(Bryophytes) Positive interactions • Wasps present in fruits of fig. When one or both the participating species are • Lichen is a mutual association of an alga benefited, it is positive interaction. Examples; and a fungus. Mutualism and Commensalism. • Roots of terrestrial plants and fungal a. Mutualism: It is an interaction between hyphae- Mycorrhiza two species of organisms in which both are b. Commensalism: It is an interaction between benefitted from the obligate association. The two organisms in which one is benefitted and following are common examples of mutualism. the other is neither benefitted nor harmed. Nitrogen fixation The species that derives benefit is called the Rhizobium (Bacterium) forms nodules in the commensal, while the other species is called the roots of leguminous plants and lives symbiotically. host. The common examples of commensalism The Rhizobium obtains food from leguminous are listed below: plant and in turn fixes atmospheric nitrogen into nitrate, making it available to host plants.
Interaction type Combination Effects Examples 1.Positive interaction 1 Mutualism (+) (+) Both species benefitted Lichen, Mycorrhiza etc. 2 Commensalism (+) (0) One species is benefitted and orchids, Lianas etc. the other species is neither benefitted nor harmed 2.Negative interaction 4 Predation (+) (-) One species benefitted, the Drosera, Nepenthes etc. other species are harmed 5 Parasitism (+) (-) One species benefitted, the Cuscuta, Duranta, other species are harmed Viscum etc. 6 Competition (-) (-) Harmful for both Grassland species 7 Amensalism (-) (0) Harmful for one, but the Penicillium and other species are unaffected Staphylo coccus (+) Benefitted, (-) Harmed (0)Unaffected Table 6.4: Different interactions of plant
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 145 01-03-2019 17:00:37 Epiphytes Examples: The plants Leaves • A number of which are found plants like Drosera Lamina growing on Supporting (Sun dew Plant), Lid plant other plants Nepenthes (Pitcher Tendril without harming Clinging Plant), Diaonaea Pitcher root them are called (Venus fly trap), Insect epiphytes. They Arial absorping root Figure 6.11: Utricularia (Bladder Fluid are commonly An epiphytic plant-Vanda wort) and Sarracenia found in tropical are predators which Figure 6.12: Pitcher rain forest. consume insects and plant – with insect The epiphytic higher plant (Orchids) gets other small animals its nutrients and water from the atmosphere for their food as a source of nitrogen. They with the help of their hygroscopic roots which are also called as insectivorous plants. contain special type of spongy tissue called Sensitive hair Velamen. So it prepares its own food and does Capsule wall not depend on the host. They use the host Absorptive plant only for support and does not harm it Valve Insect larva in any way. hairs
• Many orchids, ferns, lianas, hanging mosses, Section view Peperomia, money plant and Usnea (Lichen) are some of the examples of epiphytes. • Spanish Moss –Tillandsia grows on the bark Natural form Bladder of Oak and Pine trees. Figure 6.13: Insectivorous plant Utricularia Proto Cooperation • Many herbivores are predators. Cattles, An interaction between Camels, Goats etc., frequently browse on organisms of different the tender shoots of herbs, shrubs and species in which both trees. Generally annuals suffer more than organisms benefit but neither is dependent the perennials. Grazing and browsing may on the relationship. Example: Soil bacteria / cause remarkable changes in vegetation. fungi and plants growing in the soil. Nearly 25 percent of all insects are known as phytophagous(feeds on plant sap and Negative interactions other parts of plant) When one of the interacting species is benefitted • Many defense mechanisms are evolved to and the other is harmed, it is called negative avoid their predations by plants. Examples: interaction . Examples: predation, parasitism, Calotropis produces highly poisonous cardiac competition and amensalism. glycosides, Tobacco produces nicotine, coffee a. Predation: It is an interaction between two plants produce caffeine, Cinchona plant species, one of which captures, kills and eats produces quinine. Thorns ofBougainvillea , up the other. The species which kills is called spines of Opuntia, and latex of cacti also a predator and the species which is killed is protect them from predators. called a prey. The predator is benefitted while the prey is harmed.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 146 01-03-2019 17:00:37 b. Parasitism: It is an interaction between two Hemiparasites different species in which thesmaller partner The organisms which derive only water (parasite) obtains food from the larger partner and minerals from their host plant while (host or plant). So the parasitic species is synthesizing their own food by photosynthesis benefited while the host species is harmed. Based are called Hemiparasites. They are also called on the host-parasite relationship, parasitism is partial parasites. classified into two types they are holoparasite Examples: and hemiparasite. • Viscum and Loranthus are partial stem Holoparasites parasites. The organisms which are dependent upon the • Santalum (Sandal Wood) is a partial root host plants for their entire nutrition are called parasite. Holoparasites. They are also called total The parasitic plants produce the haustorial parasites. roots inside the host plant to absorb nutrients from the vascular tissues of host plants. T.S of host along with Cuscuta Cuscuta on the host c. Competition: It is an interaction between
a) Parasite two organisms or species in which both the organisms or species are harmed. Competition Haustoria is the severest in population that has irregular Host distribution. Competition is classified into Xylem intraspecific and interspecific. 1. Intraspecific competition: It is an interaction Phloem between individuals of the same species. This b) c) competition is very severe because all the members of species have similar requirements of Flower Parasite food, habitat, pollination etc. and they also have similar adaptations to fulfill their needs. Host 2. Interspecific competition: It is an interaction Haustoria Root Tuber Host between individuals of different species. In grassland, many species of grasses grow well as there is little competition when enough nutrients Figure 6.14: a) Holoparasite – Cuscuta and water is available. During drought shortage b) A Partial stem parasite – Viscum c) Root parasite on the brinjal root Orobanche spp. of water occurs . A life and death competition starts among the different species of grass lands. Survival in both these competitions is determined Examples: by the quantity of nutrients, availability of water • Cuscuta is a total stem parasite of the and migration to new areas. Different species of herbivores, larvae and grass hopper competing host plant Acacia, Duranta and many for fodder or forage plants. Trees, shrubs and other plants. Cuscuta even gets flower herbs in a forest struggle for sunlight, water and inducing hormone from its host plant. nutrients and also for pollination and dispersal of • Balanophora, orobanche and Refflesia fruits and seeds. TheUtricularia (Bladderwort) are the total root parasites found on competes with tiny fishes for small crustaceans higher plants. and insects.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 147 01-03-2019 17:00:38 d. Amensalism: It is an interspecific interaction • Phyllium frondosum – leaf insect, another in which one species is inhibited while the other example of protective mimicry. species is neither benefitted nor harmed. The ii. Myrmecophily: Sometimes, ants take their inhibition is achieved by the secretion of certain shelter on some trees such as Mango, Litchi, chemicals called allelopathic substances. Jamun, Acacia etc. Ant Amensalism is also called antibiosis. These ants act as • Penicillium notatum produces penicillin to body guards of the inhibit the growth of a variety of bacteria plants against any especially Staphylococcus. disturbing agent • Trichoderma inhibits the growth of fungus and the plants in Figure 6.16: Myrmecophily Aspergillus. turn provide food • Roots and hulls of Black Walnut Juglans and shelter to these ants. This phenomenon nigra secretes an alkaloid Junglone which is known as Myrmecophily. Example: Acacia inhibits the growth of seedlings of Apple, and acacia ants. Tomato and Alfalfa around it. iii. Co-evolution: The interaction between organisms, when continues for generations, Interspecific interactions/ Co-evolutionary dynamics involves reciprocal i. Mimicry: It is a phenomenon in which changes in living organism modifies its form, appearance, genetic and structure or behavior and looks like another morphological living organism as a self defence and increases characters of the chance of their survival. Floral mimicry Figure 6.17: Co-evolution both organisms. is for usually inviting pollinators but animal This type of mimicry is often protective. Mimicry is a result evolution is called Co-evolution. It is a kind of evolutionary significance due to shape and of co- adaptation and mutual change among sudden heritable mutation and preservation of interactive species. natural selection. Examples: a) b) • Corolla length and proboscis length of butterflies and moths (Habenaria and Moth ). • Bird’s beak shape and flower shape and size. • More examples: Horn bills and birds of Scrub jungles ,Slit size of pollinia of Figure 6.15: Mimicry Apocynaceae members and leg size of insects. a) Phyllium frondosum b) Carausium morosus
Example: Kairomone released from Pieris rapae caterpillar exposed • The plant,Ophrys an orchid, the flower looks to wild Radish gets the capacity like a female insect to attract the male insect to transmit defence induced by predator to get pollinated by the male insect and it is to progeny of wild radish. Transmission otherwise called ‘floral mimicry ‘. capacity of defence induced by predator to • Carausium morosus – stick insect or progeny of wild radish. walking stick. It is a protective mimicry.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 148 01-03-2019 17:00:40 a) b) 6.3 Ecological adaptations Lamina Floating leaves The modifications in the structure of Inflated petiole organisms to survive successfully in an Stolen Fibrous roots Offset environment are called adaptations of Water Fibrous roots Root pocket Root pockets organisms. Adaptations help the organisms to i) Free floating hydrophyte exist under the prevailing ecological habitat. a) Eichhornia b) Pistia Based on the habitats and the corresponding c) d) adaptations of plants, they are classified Flower Leaf lets as hydrophytes, xerophytes, mesophytes, Lamina Petiole epiphytes and halophytes. Petiole Hydrophytes Flower bud Water Water The plants which are living in water or wet Young leaf Rhizome places are called hydrophytes. According to Rhizome Root Roots their relation to water and air, they are sub- Mud Mud divided into following categories: i) Free ii) Rooted floating hydrophyte floating hydrophytes, ii) Rooted- floating c) Nymphaea d) Marsilea hydrophytes, iii) Submerged floating e) f) hydrophytes, iv) Rooted -submerged Water Stem Submerged leaves hydrophytes, v) Amphibious hydrophytes. i. Free floating hydrophytes: These plants float freely on the surface of water. They remain in contact with water and air, but not with soil. Examples: Eichhornia, Pistia and iii) Submerged floating hydrophyte Wolffia (smallest flowering plant). e) Ceratophyllum f) Utricularia g) h) ii. Rooted floating hydrophytes: In these Female plant Male plant Female flower Flower plants, the roots are fixed in mud, but their Water Whorls of submerged leaves and flowers are floating on the surface leaves Water of water. These plants are in contact with soil, Male flower
water and air. Examples: Nelumbo, Nymphaea, Stolen Branch Potomogeton and Marsilea. Roots Roots Mud Mud Lotus seeds showing highest longevity in iv) Rooted - sumerged hydrophyte plant kingdom. g) Vallisneria h) Hydrilla i) Flower j) iii. Submerged floating hydrophytes:These Flowers Emergent leaves Emergent or plants are completely submerged in water and aerial leaves not in contact with soil and air. Examples: Stem Ceratophyllum and Utricularia. Submerged Submerged leaves dissected iv. Rooted- submerged hydrophytes: These leaves plants are completely submerged in water Stolen Water Roots Roots and rooted in soil and not in contact with air. Mud Mud Examples: Hydrilla, Vallisneria and Isoetes. v) Rooted emergent hydrophyte-Heterophylly v. Amphibious hydrophytes (Rooted emergent i) Sagittaria j) Ranunculus hydrophytes): These plants are adapted to both Figure 6.18: Hydrophytes
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 149 01-03-2019 17:00:43 aquatic and terrestrial modes of life. They grow • Cortex is well developed with aerenchyma in shallow water. Examples: Ranunculus, Typha • Vascular tissues are poorly developed. In and Sagittaria. emergent forms vascular elements are well developed. Hygrophytes: The plants which can grow • Mechanical tissues are generally absent in moist damp and shady places are called except in some emergent forms. Pith cells hygrophytes. Examples: Habenaria (Orchid), are sclerenchymatous. Mosses (Bryophytes), etc. Epidermis Hypodermis Morphological adaptations of Hydrophytes: In root Air chambers Cortex • Roots are totally absent in Wolffia and Salvinia or poorly developed in Hydrilla or
well developed in Ranunculus. Endodermis • The root caps are replaced by root pockets. Pericycle Example: Eichhornia Xylem cavity Sieve tubes In stem Phloem Parenchyma • The stem is long, slender, spongy and flexible in sub-merged forms. T.s of Hydrilla stem Figure 6.19: T.S. of Hydrilla stem • In free floating forms the stem is thick, short stoloniferous and spongy; and in rooted Physiological adaptations of Hydrophytes: floating forms, it is a rhizome . • Hydrophytes have the ability to withstand • Vegetative propagation is through runners, anaerobic conditions . stolon, stem and root cuttings , tubers, • They possess special aerating organs. dormant apices and offsets. Xerophytes In leaves The plants which are living in dry or xeric • The leaves are thin, long and ribbon shaped in condition are known as Xerophytes. Xerophytic Vallisneria or long and linear in Potamogeton habitat can be of two different types. They are: or finely dissected in Ceratophyllum • The floating leaves are large and flat as in a. Physical dryness: In these habitats, soil has a Nymphaea and Nelumbo. In Eichhornia and little amount of water due to the inability of the Trapa petioles become swollen and spongy. soil to hold water because of low rainfall. • In emergent forms, the leaves show b. Physiological dryness: In these habitats, heterophylly (Submerged leaves are water is sufficiently present but plants are unable dissected and aerial leaves are entire). to absorb it because of the absence of capillary Example: Ranunculus, Limnophila spaces. Example: Plants in salty and acidic soil. heterophylla and Sagittaria Based on adaptive characters xerophytes Anatomical adaptations are classified into three categories. They are • Cuticle is either completely absent or if Ephemerals, Succulents and Non succulent present it is thin and poorly developed plants. • Single layer of epidermis is present
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 150 01-03-2019 17:00:44 i. Ephemerals: In Xerophytic plants with the leaves and These are also stem are covered with hairs are called called drought escapers or trichophyllous plants . Example: Cucurbits drought evaders. (Melothria and Mukia ) These plants In stem complete their • Stems are mostly hard and woody. They may life cycle within Figure 6.20: be aerial or underground a short period Argemone mexicana-Ephemerals (single season). • The stems and leaves are covered with wax These are not true xerophytes. Examples: coating or covered with dense hairs. Argemone, Mollugo, Tribulus and Tephrosia. • In some xerophytes all the internodes in the ii. Succulents: These are also called drought stem are modified into a fleshy leaf structure enduring plants. These plants store water in called phylloclades (Opuntia) . their plant parts during the dry period. These • In some of the others single or occasionally plants develop certain adaptive characters to two internodes modified into fleshy green resist extreme drought conditions. Examples: structure called cladode (Asparagus). Opuntia, Aloe, Bryophyllum and Begonia. In some the petiole is modified into a fleshy iii. Non succulents: These are also called leaf like structure called phyllode (Acacia drought resistant plants ( true xerophytes). melanoxylon). They face both external and internal dryness. a) b) They have many adaptations to resist dry Flower conditions. Examples: Casuarina, Nerium, Spines Stipular Zizyphus and Acacia. Phylloclade spine
a) b)
Marginal Stem spines
Leaf
Succulent c d)c) Petiole leaves 3 2 Leaves Scale leaves 1 Rhizome Stipular Roots spines Stem 4 Phyllode Figure 6.21: a)Succulent xerophyte – Aloe 1,2,3 and 4 the gradual development b) Non succulent perennial - Ziziphus Spine of phyllodes in Acacia Figure 6.22: Xerophytes Morphological Adaptations a) A succulent xerophyte: Phylloclade – opuntia In root b) Non succulent: Perennial - Capparis • Root system is well developed and is greater than that of shoot system. c) Cladode of Asparagus d) Phyllode – Acacia • Root hairs and root caps are also well developed.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 151 01-03-2019 17:00:45 In leaves Physiological adaptations • Leaves are generally leathery and shiny to • Most of the physiological processes are reflect light and heat. designed to reduce transpiration. • In some plants like Euphorbia, Acacia, • Life cycle is completed within a short Ziziphus and Capparis, the stipules are period (Ephemerals). modified into spines. Mesophytes • The entire leaves are modified into spines The plants which are living in moderate (Opuntia ) or reduced to scales (Asparagus). conditions (neither too wet nor too dry) are Anatomical adaptations known as mesophytes. These are common land • Presence of multilayered epidermis with plants. Example: Maize and Hibiscus. heavy cuticle to prevent water loss due to Morphological adaptations transpiration. • Root system is well developed with root • Hypodermis is well developed with caps and root hairs sclerenchymatous tissues. • Stems are generally aerial, stout and highly • Sunken shaped stomata are present only in the branched. lower epidermis with hairs in the sunken pits. • Leaves are generally large, broad, thin with • Scotoactive type of stomata found in different shapes. succulent plants . Anatomical adaptations • Vascular bundles are well developed with • Cuticle in aerial parts are moderately several layered bundle sheath. developed. • Mesophyll is well differentiated into • Epidermis is well developed and stomata are palisade and spongy parenchyma. generally present on both the epidermis. • In succulents the stem possesses a water • Mesophyll is well differentiated into palisade storage region. and spongy parenchyma. Thick cuticle Multi-layered epidermis • Vascular and mechanical tissues are fairly developed and well differentiated. Palisade parenchyma Physiological adaptations Spongy parenchyma Stomata • All physiological processes are normal. Guard cells • Temporary wilting takes place at room Pit (Cavity) Trichomes (Hairs) temperature when there is water scarcity. Lower epidermis Cuticle Tropophytes are plants which behave Figure 6.23: T.S. of Nerium leaf as xerophytes at summer and behave as mesophytes (or) hydrophytes during rainy
Water storage cells season.
Palisade parenchyma Epiphytes Spongy parenchyma Epiphytes are plants which grow perched on
Upper epidermis Lower epidermis other plants (Supporting plants). They use Figure 6.24: A Succulent leaf of Pepromia (T.S.) the supporting plants only as shelter and not (lateral wing portion only) for water or food supply. These epiphytes
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 152 01-03-2019 17:00:46 are commonly seen in tropical rain forests. Physiological adaptations Examples: Orchids, Lianas, Hanging Mosses Special absorption processes of water by and Money plant. velamen tissue . Morphological adaptations Halophytes • Root system is extensively developed. These There are special type of Halophytic plants roots may be of two types. They are Clinging which grow on soils with high concentration roots and Aerial roots. of salts. Examples: Rhizophora, Sonneratia and Clinging roots fix the epiphytes firmly on Avicennia. the surface of the supporting objects. Halophytes are usually found near the sea- shores and Estuaries. The soils are physically Aerial roots are green coloured roots which wet but physiologically dry. As plants cannot use may hang downwardly and absorb moisture salt water directly they require filtration of salt from the atmosphere with the help of a using physiological processes. This vegetation is spongy tissue called velamen. also known as mangrove forest and the plants • Stem of some epiphytes are succulent and are called mangroves. develop pseudo bulb or tuber. Morphological adaptations • Generally the leaves are lesser in number and may be fleshy and leathery • The temperate halophytes are herbaceous but the tropical halophytes are mostly bushy • Myrmecophily is a common occurrence in the epiphytic vegetation to prevent the • In addition to the normal roots, many stilt predators. roots are developed • The fruits and seeds are very small and • A special type of negatively geotropic usually dispersed by wind, insects and birds. roots called pneumatophores with pneumathodes to get sufficient aeration Anatomical adaptations are also present. They are called breathing • Multilayered epidermis is present. Inner to roots. Example: Avicennia the velamen tissue, the peculiar exodermis
layer is present. Pneumathode Pneumatophores (or) Lenticel • Presence of thick cuticle and sunken stomata Pneumatophores greatly reduces transpiration. • Succulent epiphytes contain well developed parenchymatous cells to store water. Roots Epidermis
Velamen Figure 6.26a: Pneumatophores of mangrove plant Exodermis • Presence of thick cuticle on the aerial parts of the Cortex plant body • Leaves are thick, Endodermis Pith Pericycle entire, succulent and Metaxylem Conjuctive tissue Protoxylem glossy. Some species Figure 6.26b: Phloem are aphyllous (without Succulent Figure 6.25: T.S. of an aerial root of orchid leaves). halophyte - showing velamen tissue Salicornia
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 153 01-03-2019 17:00:47 • Vivipary mode of seed germination is found protective covering called seed coat. As seeds in halophytes contain miniature but dormant future plants, their dispersal is an important criterion for distribution and establishment of plants over a wide geographical area. The dissemination of
Calyx Leaf seeds and fruits to various distances from the Fruit parent plant is called seed and fruit dispersal. Radicle It takes place with the help of ecological factors such as wind, water and animals. Seed dispersal is a regeneration process
Hypocotyl of plant populations and a common means of Water colonizing new areas to avoid seedling level competition and from natural enemies like Mud herbivores, frugivores and pathogens. Fruit maturation and seed dispersal is Figure 6.27: Vivipary germination influenced by many ecologically favourable Anatomical adaptations conditions such as Season (Example: Summer), • Epidermal cells of stem is heavy cutinized, suitable environment, and seasonal availability of dispersal agents like birds, insects etc. almost squarish and are filled with oil and tannins. Seeds require agents for dispersal which are crucial in plant community dynamics in • ‘Star’ shaped sclereids and ‘H’ shaped heavy many ecosystems around the globe. They offer thickened spicules that provide mechanical many benefits to communities such as food and strength to cortex are present in the stem. nutrients, migration of seeds across habitats • The leaves may be dorsiventral or isobilateral and helps spreading plant genetic diversity. with salt secreting glands. 6.4.1 Dispersal by Wind (Anemochory) Physiological adaptations The individual seeds or the whole fruit may be • High osmotic pressure exists in some modified to help for the dispersal by wind. Wind plants . dispersal of fruits and seeds is quite common in • Seeds germinate in the fruits of mother tall trees. The adaptation of the wind dispersal plant itself (Vivipary). plants are • Minute seeds: Seeds are minute, very Out of three districts of Tamil small, light and with inflated covering. Nadu (Nagapattinam, Thanjavur Example: Orchids. and Thiruvarur), Muthupet • Wings: Seeds or whole fruits are flattened to (Thiruvarur district) was less damaged by form a wing. Examples: Maple, Gyrocarpus, Gaja cyclone ( November 2018) due to the Dipterocarpus and Terminalia presence of mangrove forest.
6.4 Dispersal of Fruits and Seeds Both fruits and seeds possess attractive colour, odour, shape and taste needed for the dispersal by birds, mammals, reptiles, fish, ants and insects even earthworms. The seed consists of an embryo, stored food material and a Figure 6.28: Asclepias Figure 6.29: Gyrocarpus
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 154 01-03-2019 17:00:48 • Feathery Appendages: Seeds or fruits may beings and get dispersed. have feathery appendages which greatly ii. Sticky fruits and seeds: increase their buoyancy to disperse to high a. Some fruits have sticky glandular hairs by altitudes. Examples: Vernonia and Asclepias. which they adhere to the fur of grazing animals. • Censor mechanisms: The fruits of many Example: Boerhaavia and Cleome. plants open in such a way that the seeds b. Some fruits have viscid layer which adhere to can escape only when the fruit is violently the beak of the bird which eat them and when shaken by a strong wind. Examples: they rub them on to the branch of the tree, they Aristolochia and Poppy. disperse and germinate. Example: Cordia and Guess!! Who am I…….? I am dispersed by Alangium ant and I have caruncle. iii. Fleshy fruits: Some fleshy fruits with conspicuous colours are dispersed by human 6.4.2 Dispersal by Water (Hydrochory) beings to distant places after consumption. Dispersal of seeds and fruits by water usually Example: Mango and Diplocyclos occurs in those plants which grow in or near water bodies . Adaptation of hydrochory are • Obconical receptacle with prominent air spaces. Example: Nelumbo. • Presence of fibrous mesocarp and light pericarp. Example: Coconut. • Seeds are light, small, provided with aril Figure 6.32: Sunflower Figure 6.33: Papaya which encloses air.Example: Nymphaea. 6.4.3 Dispersal by Explosive Mechanism • The fruit may be inflated. Examples: (Autochory) Heritiera littoralis. Some fruits burst suddenly with a force • Seeds by themselves would not float may be enabling to throw seeds to a little distance away carried by water current. Example: Coconut. from the plant. Autochory shows the following adaptations. • Mere touch of some plants causes the ripened fruit to explode suddenly and seeds are thrown out with great force. Example: Impatiens (Balsam), Hura. • Some fruits when they come in contact with Figure 6.30: Nelumbo Figure 6.31: Coconut water particularly after a shower of rain, burst suddenly with a noise and scatter the 6.4.3 Dispersal by Animals (Zoochory) seeds.Examples: Ruellia and Crossandra. Birds and mammals, including human beings • Certain long pods explode with a loud play an efficient and important role in the noise like cracker, scattering the seeds in dispersal of fruit and seeds. They have the all directions. Example: Bauhinia vahlii following devices. (Camel’s foot climber) i. Hooked fruit: The surface of the fruit or seeds • As the fruit matures, tissues around seeds are have hooks,(Xanthium), barbs (Andropogon), converted into a mucilaginous fluid, due to spines (Aristida) by means of which they adhere which a high turgor pressure develops inside to the body of animals or clothes of human the fruit which leads to the dispersal of seeds.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 155 01-03-2019 17:00:50 Example: Ecballium elatrium (Squirting outcrossing plants. cucumber) Gyrocarpus and Dipterocarpus. • Seed dispersal by animals help in conservation of many species even in human altered ecosystems. • Understanding of fruits and seed dispersal acts as a key for proper functioning and establishment of many ecosystems from deserts to evergreen forests and also for the Figure 6.34: Ecballium Figure 6.35: Impatents maintenance of biodiversity conservation and restoration of ecosystems. Human aided seed dispersal Seed Ball : Seed ball Summary is an ancient Japanese Ecology is a division of biology and deals technique of encasing with the study of environment in relation to seeds in a mixture of organisms. Ecology is mainly divided into clay and soil humus two branches Autecology and Synecology. The (also in cow dung) and Figure 6.36: Seed ball environment (surrounding) includes physical, scattering them on to chemical and biological components. These suitable ground, not planting of trees manually. factors can be classified into living (biotic) This method is suitable for barren and degraded and non-living (abiotic), which make the lands for tree regeneration and vegetation before environment of an organism. The ecological monsoon period where the suitable dispersal factors are meaningfully grouped into four agents become rare. classes, which are as follows: 1. Climatic factors Guess? what is atelochory or Achory? 2. Edaphic factors 3. Topographic factors 4. Biotic factors. Ecologically important days Climate is one of the important natural March 21 - World forest day factors controlling the plant life. The climatic April 22 - Earth day factors includes light, temperature, water, May 22 - World bio diversity day wind, fire, etc. Edaphic factors, the abiotic June 05 - World environment day factors related to soil, include the physical and July 07 - Van Mohostav day chemical composition of the soil formed in a particular area. The surface features of earth September 16 - International Ozone day are called topography. Topographic influence Advantages of seed dispersal: on the climate of any area is determined by • Seeds escape from mortality near the the interaction of solar radiation, temperature, parent plants due to predation by animals humidity ,rainfall, latitude and altitude. The or getting diseases and also avoiding interactions among living organisms, the plants competition. and animals are called biotic factors, which may • Dispersal also gives a chance to occupy cause marked effects upon vegetation. favourable sites for growth. The modifications in the structure of • It is an important process in the movement organisms to survive successfully in an of plant genes particularly this is the only environment are called adaptations of method available for self-fertilized flowers organisms. Based on the habitats and the and maternally transmitted genes in corresponding adaptations of plants, they are
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 156 01-03-2019 17:00:50 classified into 1) Hydrophytes 2) Xerophytes a) i, ii, and iii only b) ii, iii and iv 3) Mesophytes 4) Epiphytes and 5) Halophytes. c) ii and iii only d) i and ii only The dissemination of seeds and fruits to various 5. Which of the given plant produces cardiac distances from the parent plant is called seed glycosides? and fruit dispersal. It takes place with the help a) Calotropis b) Acacia of ecological factors such as wind, water and c) Nepenthes d) Utricularia animals. 6. Read the given statements and select the Evaluation correct option. 1. Arrange the correct i) Loamy soil is best suited for plant growth as sequence of ecological it contains a mixture of silt, sand and clay. hierarchy starting from ii) The process of humification is slow in lower to higher level. case of organic remains containing a a) Individual organism → large amount of lignin and cellulose. Population Landscape → Ecosystem iii) Capillary water is the only water b) Landscape → Ecosystem → Biome → available to plant roots as it is present Biosphere inside the micropores. c) community → Ecosystem → Landscape → iv) Leaves of shade plant have more total Biome chlorophyll per reaction centre, low d) Population → organism → Biome → ratio of chl a and chl b are usually Landscape thinner leaves. 2. Ecology is the study of an individual species a) i, ii and iii only b) ii, iii and iv only is called c) i, ii and iv only d) ii and iii only i) Community ecology ii) Autecology 7. Read the given statements and select the iii) Species ecology iv) Synecology correct option. a) i only b) ii only Statement A : Cattle do not graze on weeds c) i and iv only d) ii and iii only of Calotropis.
3. A specific place in an ecosystem, where an Statement B : Calotropis have thorns and organism lives and performs its functions is spines, as defense against herbivores. a) habitat b) niche a) Both statements A and B are incorrect. c) landscape d) biome b) Statement A is correct but statement B is incorrect. 4. Read the given statements and select the c) Both statements A and B are correct but correct option. statement B is not the correct explanation i) Hydrophytes possess aerenchyma to of statement A. support themselves in water. d) Both statements A and B are correct and ii) Seeds of Viscum are positively statement B is the correct explanation of photoblastic as they germinate only in statement A. presence of light. iii) Hygroscopic water is the only soil water 8. In soil water available for plants is available to roots of plant growing in soil a) gravitational water as it is present inside the micropores. b) chemically bound water iv) High temperature reduces use of water c) capillary water and solute absorption by roots. d) hygroscopic water
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 157 01-03-2019 17:00:51 9. Read the following statements and fill up A B C D the blanks with correct option. a) (+) Parasitism (-) Amensalism i) Total soil water content in soil is called b) (-) Mutalism (+) Competition ______c) (+) Competition (0) Mutalism ii) Soil water not available to plants is called d) (0) Amensalism (+) Parasitism ______iii) Soil water available to plants is called 13. Ophrys an orchid resembling the female of ______an insect so as to able to get pollinated is due to phenomenon of (i) (ii) (iii) a) Myrmecophily b) Ecological equivalents (a) Holard Echard Chresard (b) Echard Holard Chresard c) Mimicry d) None of these (c) Chresard Echard Holard 14. A free living nitrogen fixing cyanobacterium (d) Holard Chresard Echard which can also form symbiotic association with the water fern Azolla 10. Column I represent the size of the soil a) Nostoc b) Anabaena particles and Column II represents type of c) chlorella d) Rhizobium soil components. Which of the following is correct match for the Column I and 15. Pedogenesis refers to Column IL a) Fossils b) Water c) Population d) Soil Column - I Column - II I). 0.2 to 2.00 mm i) Slit soil 16. Mycorrhiza promotes plant growth by II) Less than 0.002 mm ii) Clayey soil a) Serving as a plant growth regulators III) 0.002 to 0.02 mm iii) Sandy soil b) Absorbing inorganic ions from soil IV) 0.002 to 0.2 mm iv) Loamy soil c) Helping the plant in utilizing atmospheric I II III IV nitrogen a) ii iii iv i d) Protecting the plant from infection b) iv i iii ii 17. Which of the following plant has a non- c) iii ii i iv succulent xerophytic and thick leathery d) None of the above leaves with waxy coating 11. The plant of this group are adapted to live a) Bryophyllum b) Ruscus partly in water and partly above substratum c) Nerium d) Calotropis and free from water a) Xerophytes b) Mesophytes 18. In a fresh water environment like pond, c) Hydrophytes d) Halophytes rooted autotrophs are a) Nymphaea and typha 12 . Identify the A, B, C and D in the given table b) Ceratophyllum and Utricularia Effects on Effects on Interaction c) Wolffia and pistia species X species Y d) Azolla and lemna Mutualism A (+) B (+) (-) Competition (-) C D (-) 0
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 158 01-03-2019 17:00:51 19. Match the following and choose the correct 28. What is Phytoremediation ? combination from the options given below: 29. What is Albedo effect and write their effects? Column I Column II (Interaction) (Examples) 30. The organic horizon is generally absent I. Mutualism i). Trichoderma and from agricultural soils because tilling, e.g., Penicillium plowing, buries organic matter. Why is an II. Commensalism ii). Balanophora, organic horizon generally absent in desert soils ? Orobanche III. Parasitism iii). Orchids and Ferns 31. Soil formation can be initiated by biological IV. Predation iv). Lichen and organisms. Explain how? Mycorrhiza 32. Sandy soil is not suitable for cultivation. V. Amensalism v). Nepenthes and Explain why? Diaonaea 33. Describe the mutual relationship between I II III IV V the fig and wasp and comment on a) i ii iii iv v the phenomenon that operates in this b) ii iii iv v i relationship. c) iii iv v i ii d) iv iii ii v i 34. Lichen is considered as a good example of obligate mutualism. Explain.
20. Strong, sharp spines that get attached to 35. What is mutualism? Mention any two animal’s feet are found in the fruits of example where the organisms involved a) Argemone b) Ecballium are commercially exploited in modern c) Heritier d) Crossandra agriculture.
21. Sticky glands of Boerhaavia and Cleome 36. List any two adaptive features evolved in support parasites enabling them to live successfully a) Anemochory b) Zoochory on their host? c) Autochory d) Hydrochory 37. Mention any two significant roles of predation plays in nature. 22. Define ecology. 38. How does an orchid ophrys ensures its 23. What is ecological hierarchy? Name the pollination by bees ? levels of ecological hierarchy. 39. Water is very essential for life. Write any 24. What are ecological equivalents? Give one three features for plants which enable them example . to survive in water scarce environment.
25. Distinguish habitat and niche 40. Why do submerged plants receive weak 26. Why are some organisms called as illumination than exposed floating plants eurythermals and some others as in a lake? stenohaline ? 41. What is vivipary? Name a plant group 27. ‘Green algae are not likely to be found in the which exhibits vivipary. deepest strata of the ocean’. Give at least one reason.
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TN_GOVT_BOTANY_XII_PAGES_136 -161 CH 06.indd 159 01-03-2019 17:00:51 42. What is thermal stratification? Mention Flora: The kinds of plants in region their types. Frugivores: Fruit eating organisms 43. How is rhytidome act as the structural Hekistotherms: (Temperature less than 70°C) defence by plants against fire? Where very low temperature prevails and the 44. What is myrmecophily? dominant vegetation is alpine vegetation.
45. What is seed ball? Landscape: The visible features of an area of land. 46. How is anemochory differ from zoochory? Lianes: Twining vines with woody stems, 47. What is co evolution? common in forest of warm climate. 48. Explain Raunkiaer classification in the Megatherms: (Temperature more than 240°C) world’s vegetation based on the temperature. Where high temperature prevails throughout 49. List out the effects of fire to plants. the year and the dominant vegetation is tropical rain forest. 50. What is soil profile? Explain the characters of different soil horizons. Mesotherms: (Temperature ranges between 170°C and 240°C) Where high temperature 51. Give an account of various types of alternates with low temperature and the parasitism with examples. dominant vegetation is tropical deciduous 52. Explain different types of hydrophytes with forest. examples. Microtherms: (Temperature ranges between 53. Enumerate the anatomical adaptations of 70°C and 170°C) Where low temperature xerophytes. prevails and the dominant vegetation is mixed coniferous forest. 54. List out any five morphological adaptations of halophytes. Population: A group of individuals of a single species. 55. What are the advantages of seed dispersal? Scotoactive type of stomata: Stomata opens 56. Describe dispersal of fruit and seeds by during night in succulent plants and closes animals. during the day.
Glossary Vivipary: When seeds or embryos begin to Antibiosis: An association of two organisms develop before they detach from the parent. which is harmful to one of them.
Biome: A major regional community of plants and animals with similar life forms and environmental conditions.
Biosphere: The envelope containing all living organisms on earth.
Community: A group of organism living in the same place.
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