Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

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Tamilnadu Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Samacheer Kalvi 12th Bio Botany Principles of Ecology Text Book Back Questions and Answers

Question 1.
Arrange the correct sequence of ecological hierarchy starting from lower to higher level.
(a) Individual organism → Population Landscape → Ecosystem
(b) Landscape → Ecosystem → Biome → Biosphere
(c) community → Ecosystem → Landscape → Biome
(d) Population → organism → Biome → Landscape
Answer:
(a) Individual organism → Population Landscape → Ecosystem

Question 2.
Ecology is the study of an individual species is called
(i) Community ecology
(ii) Autecology
(iii) Species ecology
(iv) Synecology
(a) i only
(b) ii only
(c) i and iv only
(d) ii and iii only
Answer:
(b) ii only

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 3.
A specific place in an ecosystem, where an organism lives and performs its functions is
(a) habitat
(b) niche
(c) landscape
(d) biome
Answer:
(b) niche

Question 4.
Read the given statements and select the correct option.
(i) Hydrophytes possess aerenchyma to support themselves in water.
(ii) Seeds of Viscum are positively photoblastic as they germinate only in presence of light.
(iii) Hygroscopic water is the only soil water available to roots of plant growing in soil as it is present inside the micropores.
(iv) High temperature reduces use of water and solute absorption by roots.
(a) i, ii, and iii only
(b) ii, iii and iv
(c) ii and iii only
(d) i and ii only
Answer:
(d) i and ii only

Question 5.
Which of the given plant produces cardiac glycosides?
(a) Calotropis
(b) Acacia
(c) Nepenthes
(d) Utricularia
Answer:
(a) Calotropis

Question 6.
Read the given statements and select the correct option.
(i) Loamy soil is best suited for plant growth as it contains a mixture of silt, sand and clay.
(ii) The process of humification is slow in case of organic remains containing a large amount of lignin and cellulose.
(iii) Capillary water is the only water available to plant roots as it is present inside the micropores.
(iv) Leaves of shade plant have more total chlorophyll per reaction centre, low ratio of chi a and chi b are usually thinner leaves.
(a) i, ii and iii only
(b) ii, iii and iv only
(c) i, ii and iv only
(d) ii and iii only
Answer:
(d) ii and iii only

Question 7.
Read the given statements and select the correct option.
Statement A: Cattle do not graze on weeds of Calotropis.
Statement B: Calotropis have thorns and spines, as defense against herbivores.
(a) Both statements A and B are incorrect.
(b) Statement A is correct but statement B is incorrect.
(c) Both statements A and B are correct but statement B is not the correct explanation of statement A.
(d) Both statements A and B are correct and statement B is the correct explanation of statement A.
Answer:
(b) Statement A is correct but statement B is incorrect.

Question 8.
In soil water available for plants is
(a) gravitational water
(b) chemically bound water
(c) capillary water
(d) hygroscopic water
Answer:
(c) capillary water

Question 9.
Read the following statements and fill up the blanks with correct option.

  1. Total soil water content in soil is called ______
  2. Soil water not available to plants is called ______
  3. Soil water available to plants is called ______

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Answer:
(a) Holard, Echard and Cheresard

Question 10.
Column I represent the size of the soil particles components. Which of the following is correct match for the Column I and Column II

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Answer:
(c) i, ii, i and iv

Question 11.
The plant of this group are adapted to live partly in water and partly above substratum and free from water
(a) Xerophytes
(b) Mesophytes
(c) Hydrophytes
(d) Halophytes
Answer:
(b) Mesophytes

Question 12.
Identify the A, B, C and D in the given table:
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Answer:
(a) (+) Parasitism (-) Amensalism

Question 13.
Ophrys an orchid resembling the female of an insect so as to able to get pollinated is due to phenomenon of
(a) Myrmecophily
(b) Ecological equivalents
(c) Mimicry
(d) None of these
Answer:
(c) Mimicry

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 14.
A free living nitrogen fixing cyanobacterium which can also form symbiotic association with the water fem Azolla
(a) Nostoc
(b) Anabaena
(c) Chlorella
(d) Rhizobium
Answer:
(b) Anabaena

Question 15.
Pedogenesis refers to
(a) Fossils
(b) Water
(c) Population
(d) Soil
Answer:
(d) Soil

Question 16.
Mycorrhiza promotes plant growth by
(a) Serving as a plant growth regulators
(b) Absorbing inorganic ions from soil
(c) Helping the plant in utilizing atmospheric nitrogen
(d) Protecting the plant from infection
Answer:
(d) Protecting the plant from infection

Question 17.
Which of the following plant has a non-succulent xerophytic and thick leathery leaves with waxy coating?
(a) Bryophyllum
(b) Ruscus
(c) Nerium
(d) Calotropis
Answer:
(d) Calotropis

Question 18.
In a fresh water environment like pond, rooted autotrophs are
(a) Nymphaea and typha
(b) Ceratophyllum and Utricularia
(c) Wolffia and pistia
(d) Azolla and lemna
Answer:
(a) Nymphaea and typha

Question 19.
Match the following and choose the correct combination from the options given below:
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Answer:
(d) iv, iii, ii, v and i

Question 20.
Strong, sharp spines that get attached to animal’s feet are found in the fruits of
(a) Argemone
(b) Ecballium
(c) Heraitier
(d) Crossandra
Answer:
(a) Argemone

Question 21.
Sticky glands of Boerhaavia and Cleome support
(a) Anemochory
(b) Zoochory
(c) Autochory
(d) Hydrochory
Answer:
(b) Zoochory

Question 22.
Define ecology.
Answer:
Ecology is the study of the reciprocal relationship between living organisms and their environment.

Question 23.
What is ecological hierarchy?
Name the levels of ecological hierarchy.
Answer:
The interaction of organisms with their environment results in the establishment of grouping of organisms which is called ecological hierarchy.
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 24.
What are ecological equivalents? Give one example.
Answer:
Taxonomically different species occupying similar habitats (Niches) in different geographical regions are called Ecological equivalents.
E.g: Certain species of epiphytic orchids of Western Ghats of India differ from the epiphytic orchids of South America. But they are epiphytes.

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 25.
Distinguish habitat and niche.
Answer:
Habitat:

  1. A specific physical space occupied by an organism (species).
  2. Same habitat may be shared by many organisms (species).
  3. Habitat specificity is exhibited by organism.

Niche:

  1. a functional space occupied by an organism in the same eco-system
  2. A single niche is the occupied by a single species
  3. Organisms may change their niche with time and season

Question 26.
Why are some organisms called as eurythermals and some others as stenohaline?
Answer:

  1. Eurythermal: Organisms which can tolerate a wide range of temperature fluctuations.
    Example: Zostera.
  2. Stenothermal: Organisms which can tolerate only small range of temperature variations.
    Example: Mango.

Question 27.
‘Green algae are not likely to be found in the deepest strata of the ocean’. Give at least one reason.
Answer:
As the name indicates, green algae possess photosynthetic pigments which use the light as energy source for survival and they are not found in deepest sea since there is lack of light.

Question 28
What is Phytoremediation?
Answer:
Phytoremediation refers to the using of living green plants to overcome soil or water contamination.
E.g: Growing Eichhomia in cadmium enriched soil reduces the level of cadmium.

Question 29.
What is Albedo effect and write their effects?
Answer:
Gases let out to atmosphere causes climatic change. Emission of dust and aerosols from industries, automobiles, forest fire,  and DMS (dimethyl sulphur) play an important role in disturbing the temperature level of any region. Aerosols with small particles is reflecting the solar radiation entering the atmosphere. This is known as Albedo effect.

Question 30.
The organic horizon is generally absent from agricultural soils because tilling, e.g., plowing, buries organic matter. Why is an organic horizon generally absent in desert soils?
Answer:
Organic horizon is generally absent in deserts because of low content of organic matter due to scarcity of plant and animal remains or excreta.

Question 31.
Soil formation can be initiated by biological organisms. Explain how?
Answer:
Soil formation is initiated by the biological weathering process. Biological weathering takes place when organisms like bacteria, fungi, lichens and plants help in the breakdown of rocks through the production of acids and certain chemical substances.

Question 32.
Sandy soil is not suitable for cultivation. Explain why?
Answer:
Sandy soil has a high porosity leading to decreased water retention hence unfit for cultivation.

Question 33.
Describe the mutual relationship between the fig and wasp and comment on the phenomenon that operates in this relationship.
Answer:
Wasps present in the figs is an example of mutualism where both the interacting species are benefitted from the obligate association. Wasps acts as a pollinating agents for figs intum larvae of wasps are nourished and protected by fruits of figs.

Question 34.
Lichen is considered as a good example of obligate mutualism. Explain.
Answer:
Lichen is a mutual association of an alga and a fungus, where the algal partner nourishes and provides shelter to fungi, intum fungi confers protection from bacterial infections and also maintains moisture for algal growth.

Question 35.
What is mutualism? Mention any two example where the organisms involved are commercially exploited in modern agriculture.
Answer:

  1. Mutualism is an interaction between two species of organisms in which both are benefitted from the obligate
  2. association. Nitrogen fixing cyanobacteria associated with Azolla (a fern) and Rhizobium found in the root nodules of leguminous plant are used in the field of agriculture to increase the soil fertility.

Question 36.
List any two adaptive features evolved in parasites enabling them to live successfully on their host?
Answer:
Presence of haustorial roots inside the host plant to absorb nutrients.

Question 37.
Mention any two significant roles of predation plays in nature.
Answer:
Predation maintains the stability of food chain in an ecosystem. Population of the insects and small animals are in control due to predation or else it may lead to overgrazing and browsing thereby altering the vegetation.

Question 38.
How does an orchid ophrys ensures its pollination by bees ?
Answer:
The plant, Ophrys an orchid, the flower looks like a female insect to attract the male insect to get pollinated by the male insect and it is otherwise called ‘floral mimicry ‘

Question 39.
Water is very essential for life. Write any three features for plants which enable them to survive in water scarce environment.
Answer:

  1. Presence of highly developed root system to absorb water.
  2. Stems and leaves are covered with waxing coating or dense hairs to avoid transpirational loss.
  3. Modified leaves generally leathery and shiny to reflect light and heat.

Question 40.
Why do submerged plants receive weak illumination than exposed floating plants in a lake?
Answer:
Submerged plants like Vallisneria receive dim illumination because majority of the light are reflected back by the water surface whereas, the floating hydrophytes receive and absorb maximum light as they are on the water surface.

Question 41.
What is vivipary? Name a plant group which exhibits vivipary.
Answer:
Viviparity is the phenomenon, where the seeds germinate and then starts developing to some extent before they detach from the parent plant body. In plant, it is noticed in Halophytes like Rhizophora.

Question 42.
What is thermal stratification? Mention their types.
Answer:
Thermal Stratification is usually found in aquatic habitat. The change in the temperature profile with increasing depth in a water body is called thermal stratification. There are three kinds of thermal stratifications.

  1. Epilimnion – The upper layer of warmer water.
  2. Metalimnion – The middle layer with a zone of gradual decrease in temperature.
  3. Hypolimnion – The bottom layer of colder water.

Question 43.
How is rhytidome act as the structural defence by plants against fire?
Answer:
Rhytidome is the structural defense by plants against fire. The outer bark of trees which extends to the last formed periderm is called Rhytidome. It is composed of multiple layers of suberized periderm, cortical and phloem tissues. It protects the stem against fire, water loss, invasion of insects and prevents infections by microorganisms.

Question 44.
What is myrmecophily?
Answer:
Sometimes, ants take their shelter on some trees such as Mango, Litchi, Jamun and Acacia, etc. These ants act as body guards of the plants against any disturbing agent and the plants in turn provide food and shelter to these ants. This phenomenon is known as Myrmecophily. Example: Acacia and its ants.

Question 45.
What is seed ball?
Answer:
Seed ball is an ancient Japanese technique of encasing seeds in a mixture of clay and soil humus (also in cow dung) and scattering them on to suitable ground, not planting of trees manually. This method is suitable for barren and degraded lands for tree regeneration and vegetation before monsoon period where the suitable dispersal agents become rare.

Question 46.
How is anemochory differ from zoochory?
Answer:
Anemochory:

  1. Anemochory refers to the seed dispersal by wind.
  2. Anemochory seeds are very minute and may have wings or feathery appendages for dispersal.
  3. E.g: Orchids

Zoochory:

  1. Zoochory refers to the seed dispersal by animals.
  2. Zoochory seeds and fruits are very fleshy and succulent and sticky they may have hooks to adhere to the body of animals.
  3. E.g: Mango

Question 47.
What is co-evolution?
Answer:
The interaction between organisms, when continues for generations, involves reciprocal changes in genetic and morphological characters of both organisms. This type of evolution is called Co-evolution. It is a kind of co-adaptation and mutual change among interactive species.
Examples:

  • Corolla length and proboscis length of butterflies and moths (Habenaria and Moth).
  • Bird’s beak shape and flower shape and size.

Question 48.
Explain Raunkiaer classification in the world’s vegetation based on the temperature.
Answer:
Raunkiaer classified the world’s vegetation into the following four types. They are megatherms, mesotherms, microtherms and hekistotherms.

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 49.
List out the effects of fire to plants.
Answer:
Effects of fire:

  1. Fire has a direct lethal effect on plants.
  2. Burning scars are the suitable places for the entry of parasitic fungi and insects.
  3. It brings out the alteration of light, rainfall, nutrient cycle, fertility of soil, pH, soil flora and fauna.
  4. Some fungi which grow in soil of burnt areas are called pyrophilous.
  5. Example: Pyronema confluens.

Question 50.
What is soil profile? Explain the characters of different soil horizons.
Answer:
Soil is commonly stratified into horizons at different depth. These layers differ in their physical, chemical and biological properties. This succession of super-imposed horizons is called soil profile.
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 51.
Give an account of various types of parasitism with examples.
Answer:
(a) Parasitism: It is an interaction between two different species in which the smaller partner (parasite) obtains food from the larger partner (host or plant). So the parasitic species is benefitted while the host species is harmed. Based on the host-parasite relationship, parasitism is classified into two types they are holoparasite and hemiparasite.

(b) Holoparasites: The organisms which are dependent upon the host plants for their entire nutrition are called Holoparasites. They are also called total parasites.
Examples:

  • Cuscuta is a total stem parasite of the host plant Acacia, Duranta and many other plants. Cuscuta even gets flower inducing hormone from its host plant.
  • Balanophora, orobanche and Refflesia are the total root parasites found on higher plants.

(c) Hemiparasites: The organisms which derive only water and minerals from their host plant while synthesizing their own food by photosynthesis are called Hemiparasites. They are also called partial parasites.
Examples:

  • Viscum and Loranthus are partial stem parasites.
  • Santalum (Sandal Wood) is a partial root parasite.
    The parasitic plants produce the haustorial roots inside the host plant to absorb nutrients from the vascular tissues of host plants.

Question 52.
Explain different types of hydrophytes with examples.
Answer:
Hydrophytes
The plants which are living in water or wet places are called hydrophytes. According to their relation to water and air, they are sub-divided into following categories:

  1. Free floating hydrophytes
  2. Rooted-floating hydrophytes
  3. Submerged floating hydrophytes
  4. Rooted- submerged hydrophytes
  5. Amphibious hydrophytes.

1. 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 Wolffia (smallest flowering plant).

2. Rooted floating hydrophytes: In these plants, the roots are fixed in mud, but their leaves and flowers are floating on the surface of water. These plants are in contact with soil, water and air. Examples: Nelumbo, Nymphaea, Potomogeton and Marsilea.

3. Submerged floating hydrophytes: These plants are completely submerged in water and not in contact with soil and air. Examples: Ceratophyllum and Utricularia.

4. Rooted-submerged hydrophytes: These plants are completely submerged in water and rooted in soil and not in contact with air. Examples: Hydrilla, Vallisneria and Isoetes.

5. Amphibious hydrophytes (Rooted emergent hydrophytes): These plants are adapted to both aquatic and terrestrial modes of life. They grow in shallow water. Examples: Ranunculus, Typha and Sagittaria.

Question 53.
Enumerate the anatomical adaptations of xerophytes.
Answer:

  1. Presence of multilayered epidermis with heavy cuticle to prevent water loss due to transpiration.
  2. Hypodermis is well developed with sclerenchymatous tissues.
  3. Sunken shaped stomata are present only in the lower epidermis with hairs in the sunken pits.
  4. Scotoactive type of stomata found in succulent plants.
  5. Vascular bundles are well developed with several layered bundle sheath.
  6. Mesophyll is well differentiated into palisade and spongy parenchyma.
  7. In succulents, the stem possess a water storage region.

Question 54.
List out any five morphological adaptations of halophytes.
Answer:
Morphological adaptations

  1. The temperate halophytes are herbaceous but the tropical halophytes are mostly bushy.
  2. In addition to the normal roots, many stilt roots are developed.
  3. A special type of negatively geotropic roots called pneumatophores with pneumathodes to get sufficient aeration are also present. They are called breathing roots.
    Example: Avicennia.
  4. Presence of thick cuticle on the aerial parts of the plant body.
  5. Leaves are thick, entire, succulent and glossy. Some species are aphyllous (without leaves).

Question 55.
What are the advantages of seed dispersal?
Answer:
Advantages of seed dispersal:

  1. Seeds escape from mortality near the parent plants due to predation by animals or getting diseases and also avoiding competition.
  2. Dispersal also gives a chance to occupy favourable sites for growth.
  3. It is an important process in the movement of plant genes particularly this is the only method available for self-fertilized flowers and maternally transmitted genes in outcrossing plants.
  4. Seed dispersal by animals help in conservation of many species even in human altered ecosystems.
  5. 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 maintenance of biodiversity conservation and restoration of ecosystems.

Question 56.
Describe dispersal of fruit and seeds by animals.
Answer:
Birds and mammals, including human beings play an efficient and important role in the dispersal of fruit and seeds. They have the following devices.

  1. Hooked fruit: The surface of the fruit or seeds have hooks (Xanthium), barbs (Andropogon), spines (Aristida) by means of which they adhere to the body of animals or clothes of human beings and get dispersed.
  2. Sticky fruits and seeds:
    • Some fruits have sticky glandular hairs by which they adhere to the fur of grazing animals. Example: Boerhaavia and Cleome.
    • Some fruits have viscid layer which adhere to the beak of the bird which eat them and when they rub them on to the branch of the tree, they disperse and germinate.
      Example: Cordia and Alangium.
  3. Fleshy fruits: Some fleshy fruits with conspicuous colours are dispersed by human beings to distant places after consumption.

Samacheer Kalvi 12th Bio Botany Principles of Ecology Additional Questions and Answers

1 – Mark Questions

Question 1.
Who is called as the father of Modem Ecology?
Answer:
Eugene P. Odum

Question 2.
Autoecology deals with the study of ________
(a) Community
(b) Population
(c) Individual species
(d) Niche of species
Answer:
(c) Individual species

Question 3.
Environment of any community is called
(a) Paratope
(d) Biotope
(c) Opitope
(d) Biotope
Answer:
(d) Biotope

Question 4.
Match Coloumn I with Column II
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Answer:
(a) – iii
(b) – i
(c) – iv
(d) – ii

Question 5.
The study of soil is called as __________
(a) Lithotripsy
(b) Lithosphere
(c) Pedology
(d) Pedology analysis
Answer:
(c) Pedology

Question 6.
Identify the indicators of fire.
(a) Pucinia
(b) Pyricularia
(c) Pyronema
Answer:
(c) Pyronema

Question 7.
The surface features of earth are called __________
Answer:
Topography

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 8.
Amensalism is called as __________
Answer:
Antibiosis

Question 9.
is the transition zone between two ecosystems.
Answer:
Ecotone

Question 10.
Match the type of species interaction with correct combination. Interaction Type Combination
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Answer:
(a) – iii (b) – i (c) – iv (d) – ii

Question 11.
Wasps is the fruits of fig is an example for ________ type of species interaction.
Answer:
Mutualism

Question 12.
Statement 1: Latitudes represent distance from the equator.
Statement 2: Height above the seal level from longitude.
(a) Statement 1 is correct. Statement 2 is incorrect.
(b) Statement 1 is incorrect. Statement 2 is correct.
(c) Both the statements are correct.
(d) Both the statements are incorrect.
Answer:
(a) Statement 1 is correct. Statement 2 is incorrect.

Question 13.
Statement 1: Holoparsites depend totally on other organisms for nutrition.
Statement 2: Dumta is holoparasite.
(a) Statement 1 is correct. Statement 2 is incorrect.
(b) Statement 1 is incorrect. Statement 2 is correct.
(c) Both the statements are correct.
(d) Both the statements are incorrect.
Answer:
(c) Both the statements are correct.

Question 14.
Statement 1: Ephemerals are drought evaders.
Statement 2: They are not true xerophytes.
(a) Statement 1 is correct. Statement 2 is incorrect.
(b) Statement 1 is incorrect. Statement 2 is correct.
(c) Both the statements are correct.
(d) Both the statements are incorrect.
Answer:
(c) Both the statements are correct.

Question 15.
Assertion (A) : Plains and valleys are rich in vegetation
Reason (R): Slow drain of surface water and better water retention is noticed.
(a) A is true R is false
(b) R explains A
(c) A and R are false
(d) A and R are true. But R doesnot explains A
Answer:
(b) R explains A

Question 16.
Utricularia is a _______
(a) Rooted floating hydrophyte
(b) Submerged floating hydrophyte
(c) Rooted submerged hydrophyte
(d) Amphibious hydrophyte
Answer:
(b) Submerged floating hydrophyte

Question 17.
Earth day is observed on
(a) April 22nd
(b) March 21st
(c) July 07th
(d) September 16th
Answer:
(a) April 22nd

Question 18.
Plants in sandy soils are commonly called as _______
Answer:
Psammophytes

2 – Mark Questions

Question 1.
How Earnest Haeckel defined ecology?
Answer:
Earnest Haeckel defined “Ecology is the study of the reciprocal relationship between living organisms and their environment.”

Question 2.
What is ecological hierarchy?
Answer:
The interaction of organisms with their environment results in the establishment of grouping of organisms which is called ecological hierarchy.

Question 3.
Sequentially arrange the different units of ecological hierarchy.
Answer:
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 4.
Define

  1. Autecology
  2. Synecology.

Answer:

  1. Autecology is the ecology of an individual species and is also called species ecology.
  2. Synecology is the ecology of a population or community with one or more species and also called as community ecology.

Question 5.
What is Niche?
Answer:
An ecological niche refers to an organism’s place in the biotic environment and its functional role in an ecosystem.

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 6.
What are ecological factors?
Answer:
The environment (surrounding) includes physical, chemical and biological components. When a component surrounding an organism affects the life of an organism, it becomes a factor. All such factors together are called environmental factors or ecological factors.

Question 7.
Name the climatic factors that affect plant life.
Answer:
Light, Temperature, Water, Wind and Fire.

Question 8.
Name any four physiological processes in plants, where the light plays a crucial role.
Answer:

  1. Photosynthesis
  2. Transpiration
  3. Seed germination
  4. Flowering

Question 9.
Heliophytes differ from Sciophytes. How?
Answer:
Heliophytes – Light loving plants. Example: Angiosperms.
Sciophytes – Shade loving plants. Example: Bryophytes and Pteridophytes.

Question 10.
Based on temperature prevalence, Raunkiaer classified world’s vegetation into four types. Name them.
Answer:
Raunkiaer classified the world’s vegetation into the following four types. They are megatherms, mesotherms, microtherms and hekistotherms.

Question 11.
Distinguish between evergreen forests and sclerophyllous forests.
Answer:
Evergreen Forests: Found where heavy rainfall occurs throughout the year.
Sclerophyllous Forests: Found where heavy rainfall occurs during winter and low rainfall during summer.

Question 12.
What does the term ‘Timber line’ refers to?
Answer:
Timber line is an imaginary line in a mountain or higher areas of land that marks the level above which trees do not grow. The altitudinal limit of normal tree growth is about 3000 to 4000 m.

Question 13.
Compare Euryhaline organisms with stenohaline organisms.
Answer:

  1. Euryhaline: Organisms which can live in water with wide range of salinity. Examples: Marine algae and marina angiosperms.
  2. Stenohaline: Organisms which can withstand only small range of salinity. Example: Plants of estuaries.

Question 14.
Write the composition of gases in atmosphere.
Answer:
Nitrogen -78% , Oxygen -21%, Carbon-di-oxide -0.03%, Argon and other gases – 0.93%.

Question 15.
What is Albedo effect?
Answer:
Gases let out to atmosphere causes climatic change. Emission of dust and aerosols from industries, automobiles, forest fire, S02 and DMS (dimethyl sulphur) play an important role in disturbing the temperature level of any region. Aerosols with small particles is reflecting the solar radiation entering the atmosphere. This is known as Albedo effect.

Question 16.
Point any two adverse effects of fire in an environment.
Answer:

  1. Fire has a direct lethal effect on plants.
  2. It brings out the alteration of light, rainfall, nutrient cycle, fertility of soil, pH, soil flora and fauna

Question 17.
Pyronema confluens is the indicator of fire – comment.
Answer:
Pyronema confluens is a fungus which grow on the soil of burnt or fire disturbed areas. Hence it is called as indicator of fire.

Question 18.
What are edaphic factors?
Answer:
Edaphic factors are the abiotic factors related to soil, include the physical and chemical composition of the soil formed in a particular area.

Question 19.
Name the study that deals with soil factors. Also mention the optimal soil pH for crop cultivation.
Answer:
The study of soil is called pedology. The best pH of soil for crop cultivation is 5.5 to 6.8.

Question 20.
Define soil profile.
Answer:
Soil is commonly stratified into horizons at different depth. These layers differ in their physical, chemical and biological properties. This succession of super-imposed horizons is called soil profile.

Question 21.
Given below are few types of plants. Mention their habitats.

  1. Halophytes
  2. Chasmophytes
  3. Cryophytes
  4. Psammophytes.

Answer:

  1. Halophytes: Plants living in saline soils.
  2. Chasmophytes: Plants living in rocky crevices.
  3. Cryophytes: Plants living in ice surface.
  4. Psammophytes: Plants living in sandy soils.

Question 22.
Mention any four topographic factors that affect vegetation.
Answer:

  1. Latitude
  2. Altitude
  3. Direction of mountain and
  4. Steepness of mountain.

Question 23.
How the steepness of mountain affects the vegetation?
Answer:
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.

Question 24.
Name any two positive interactions with an example for each.
Answer:

  1. Mutualism – E.g: Lichen
  2. Commensalism – E.g: Orchids.

Question 25.
Define mutualism with an example.
Answer:
Mutualism is an interaction between two species of organisms in which both are benefitted from the obligate association. E.g: Lichens (alga with fungus).

Question 26.
What is the principle of commensalism?
Answer:
Commensalism is an interaction between two organisms in which one is benefitted and the other is neither benefitted nor harmed. The species that derives benefit is called the commensal, while the other species is called the host.

Question 27.
Specify the type of interactions between the given pair of species.

  1. Spanish moss and Oak tree
  2. Cuscuta and Acacia
  3. Nepenthes and Ants
  4. Alga and fungus

Answer:

  1. Commensalism
  2. Parasitism
  3. Predation
  4. Mutualism

Question 28.
Explain the concept of proto co-operation.
Answer:
Proto Co-operation is an interaction between organisms of different species in which both organisms benefit but neither is dependent on the relationship. Example: Soil bacteria / fungi and plants growing in the soil.

Question 29.
What are Holoparasites? Give example.
Answer:
The organisms which are dependent upon the host plants for their entire nutrition are called Holoparasites. They are also called total parasites.
Example: Cuscuta is a total stem parasite of the host plant Acacia.

Question 30.
What are hemiparasites? Give example.
Answer:
Hemiparasites is the organisms which derive only water and minerals from their host plant while synthesizing their own food by photosynthesis are called Hemiparasites. They are also called partial parasites.
Example: Viscum.

Question 31.
Cite an example for partial stem parasite and partial root parasite.
Answer:

  1. Partial stem parasite – E.g: Loranthus.
  2. Partial root parasite – E.g: Santalum.

Question 32.
Define Amensalism.
Answer:
Amensalism is an interspecific interaction in which one species is inhibited while the other species is neither benefitted nor harmed. The inhibition is achieved by the secretion of certain chemicals called allelopathic substances. Amensalism is also called antibiosis.

Question 33.
Point out any two morphological adaptations noticed in the roots of hydrophytes.
Answer:

  1. Roots are totally absent in Wolffia and Salvinia or poorly developed in Hydrilla or well developed in Ranunculus.
  2. The root caps are replaced by root pockets.
    Example: Eichhomia.

Question 34.
What are hygrophytes? Give example.
Answer:
The plants which can grow in moist damp and shady places are called hygrophytes. Examples: Habenaria (Orchid) and Mosses (Bryophytes), etc.

Question 35.
What are trichophyllous plants? Give example.
Answer:
In xerophytic plants, with the leaves and stem are covered with hairs are called trichophyllous plants.
Example: Cucurbits (Melothria and Mukia)

Question 36.
Give an example for following type of adaptations.

  1. Phyllode
  2. Cladode

Answer:

  1. Phyllode – E.g: Acacia.
  2. Cladode – E.g: Asparagus.

Question 37.
Write a brief note on pneumatophores. Give an example.
Answer:
Pneumatophores are the special type of negatively geotropic roots developed by halophytes. It possess pneumathodes to get sufficient aeration. They are also called breathing roots.
Example: Avicennia.

3 – Mark Questions

Question 38.
Differentiate habitat from niche.
Answer:
Habitat:

  1. A specific physical space occupied by an organism (species).
  2. Same habitat may be shared by many organisms (species).
  3. Habitat specificity is exhibited by organism.

Niche:

  1. A functional space occupied by an organism in the same eco-system.
  2. A single niche is occupied by a single species.
  3. Organisms may change their niche with time and season.

Question 39.
What is thermal stratification? Explain its types.
Answer:
Thermal stratification is usually found in aquatic habitat. The change in the temperature profile with increasing depth in a water body is called thermal stratification. There are three kinds of thermal stratifications.

  1. Epilimnion – The upper layer of warmer water.
  2. Metalimnion – The middle layer with a zone of gradual decrease in temperature.
  3. Hypolimnion – The bottom layer of colder water.

Question 40.
What are the adverse effects of temperature on plant?
Answer:

  1. Temperature affects the enzymatic action of all the bio-chemical reactions in a plant body.
  2. Low temperature with high humidity can spread diseases to plants.
  3. The varying temperature with moisture determines the distribution of the vegetation types.

Question 41.
Explain briefly about the three types of fire.
Answer:

  1. Ground fire – Which is flameless and subterranean.
  2. Surface fire – Which consumes the herbs and shrubs.
  3. Crown fire – Which bums the forest canopy.

Question 42.
Classify soil based on its formation.
Answer:
Based on soil formation (pedogenesis), the soils are divided into:

  1. Residual soils -These are soils formed by weathering and pedogenesis of the rock.
  2. Transported soils – These are transported by various agencies.

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 43.
Loamy soil is ideal for crop cultivation – Justify.
Answer:
Loamy soil is ideal soil for cultivation, since it consists of 70% sand and 30% clay or silt or both. It ensures good retention and proper drainage of water. The porosity of soil provides adequate aeration and allows the penetration of roots.

Question 44.
Direction of mountain determines the richness of vegetation – Justify.
Answer:
North and south faces of mountain or hill possess different types of flora and fauna because they differ in their humidity, rainfall, light intensity, light duration and temperature regions. The two faces of the mountain or hill receive different amount of solar radiation, wind action and rain. Of these two faces, the windward region possesses good vegetation due to heavy rains and die leeward region possesses poor vegetation due to rain shadows (rain deficit).

Question 45.
What are epiphytes? Explain their characteristic features.
Answer:
The plants which are found growing on other plants without harming them are called epiphytes. They are commonly found in tropical rain forest The epiphytic higher plant (Orchids) gets its nutrients and water from the atmosphere with the help of their hygroscopic roots which contain special type of spongy tissue called Velamen. So it prepares its own food and does not depend on the host. They use the host plant only for support and does not harm.

Question 46.
Discuss on predator – prey interaction with example.
Answer:
Predation: It is an interaction between two species, one of which captures, kills and eats up the other. The species which kills is called a predator and the species which is killed is called a prey. The predator is benefitted while the prey is harmed. Many herbivores are predators. Cattles, Camels and Goats etc., frequently browse on the tender shoots of herbs, shrubs and trees.

Question 47.
Give an account of Mimicry.
Answer:
Mimicry is a phenomenon in which living organism modifies its form, appearance, structure or behavior and looks like another living organism as a self defence and increases the chance of their survival. Floral mimicry is for usually inviting pollinators but animal mimicry is often protective. Mimicry is a result of evolutionary significance due to shape and sudden heritable mutation and preservation of natural selection.

Question 48.
Mention any two species that exhibits protective mimicry.
Answer:

  1. Carausium morosus (Stick insect)
  2. PhyIlium frondosum (Leaf insect).

Question 49.
What is co-evolution? Explain with example.
Answer:
The interaction between organisms, when continues for generations, involves reciprocal changes in genetic and morphological characters of both organisms. This type of evolution is called Co-evolution. It is a kind of co-adaptation and mutual change among interactive species.
Examples:

  • Corolla length and proboscis length of butterflies and moths (Habenaria and Moth).
  • Bird’s beak shape and flower shape and size.

Question 50.
How physical dryness differ from physiological dryness?
Answer:

  1. Physical dryness: In these habitats, soil has a little amount of water due to the inability of the soil to hold water because of low rainfall.
  2. Physiological dryness: In these habitats, water is sufficiently present but plants are unable to absorb it because of the absence of capillary spaces.
    Example: Plants in salty and acidic soil.

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 51.
Point out the Anatomical adaptations exhibited by the Halophytes.
Answer:
Anatomical adaptations:

  1. Epidermal cells of stem is heavily cutinized, almost squarish and are filled with oil and tannins.
  2. Star’ shaped sclereids and ‘H’ shaped heavy thickened spicules that provide mechanical strength to cortex are present in the stem.
  3. The leaves may be dorsiventral or isobilateral with salt secreting glands.

5-Mark Question

Question 52.
Explain various edaphic factors that affect vegetation.
Answer:
The important edaphic factors which affect vegetation are as follows:

  1. Soil moisture: Plants absorbs rain water and moisture directly from the air.
  2. Soil water: Soil water is more important than any other ecological factors affecting the distribution of plants. Rain is the main source of soil water. Capillary water held between pore spaces of soil particles and angles between them is the most important form of water available to the plants.
  3. Soil reactions: Soil may be acidic or alkaline or neutral in their reaction. pH value of the . soil solution determines the availability of plant nutrients. The best pH range of the soil for cultivation of crop plants is 5.5 to 6.8.
  4. Soil nutrients: Soil fertility and productivity is the ability of soil to provide all essential plant nutrients such as minerals and organic nutrients in the form of ions.
  5. Soil temperature: Soil temperature of an area plays an’important role in determining the
    geographical distribution of plants. Low temperature reduces use of water and solute absorption by roots. .
  6. Soil atmosphere: The spaces left between soil particles are called pore spaces which contains oxygen and carbon-di-oxide.
  7. Soil organisms: Many organisms existing in the soil like bacteria, fungi, algae, protozoans, nematodes, insects and earthworms, etc. are called soil organisms.

Question 53.
What does competition refers to? Classify and describe it.
Answer:
1.Competition: It is an interaction between two organisms or species in which both the organisms or species are harmed. Competition is the severest in population that has irregular distribution. Competition is classified into intraspecific and interspecific.

2. Intraspecific competition: It is an interaction between individuals of the same species. This competition is very severe because all the members of species have similar requirements of food, habitat and pollination etc., and they also have similar adaptations to fulfill their needs.

3. Interspecific competition: It is an interaction between individuals of different species. In grassland, many species of grasses grow well as there is little competition when enough nutrients and water is available. During drought Shortage of water occurs. A life and death competition starts among the different species of grass lands.

Survival in both these competitions is determined by the quantity of nutrients, availability of water and migration to new areas. Different species of herbivores, larvae and grass hopper competing for fodder or forage plants. Trees, shrubs and herbs in a forest struggle for sunlight, water and nutrients and also for pollination and dispersal of fruits and seeds, The Utricularia (Bladderwort) competes with tiny fishes for small crustaceans and insects.

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 54.
Point out any five morphological adaptations of epiphytes.
Answer:
Morphological adaptations:

  1. Root system is extensively developed. These roots may be of two types. They are Clinging roots and Aerial roots. Clinging roots fix the epiphytes firmly on the surface of the supporting objects. Aerial roots are green coloured roots which may hang downwardly and absorb moisture from the atmosphere with the help of a spongy tissue called velamen.
  2. Stem of some epiphytes are succulent and develop pseudo bulb or tuber.
  3. Generally the leaves are lesser in number and may be fleshy and leathery.
  4. Myrmecophily is a common occurrence in the epiphytic vegetation to prevent the predators.
  5. The fruits and seeds are very small and usually dispersed by wind, insects and birds.

Higher Order Thinking Skills (HOTs) Questions

Question 1.
Being a tropical country, India is the largest producer of delicious mangoes. These mango tree don’t grow in temperate countries. Give reason.
Answer:
Mango tree show very narrow range of thermal tolerance. Hence they cannot grow in temperate countries.

Question 2.
What is cause of flag forms in trees?
Answer:
Unidirectional wind stimulates the development of flag forms in trees.

Question 3.
In the picture given below, A and B represents the two different biomes. What does the letter C denotes? What will be its impact on the organisms in C Explain with example.
Answer:
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
The letter C denotes Ecotone – a transition zone between two different ecosystem. Those species found in the ecotone will have impact of environment of two habitats.
E.g. Owl in the ecotone area between forest and grassland.

Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology

Question 4.
Observe the tabular column and complete it using proper terms.
Samacheer Kalvi 12th Bio Botany Solutions Chapter 6 Principles of Ecology
Answer:
A = +
B = Commensalism
C = –
D = Parasitism
E = –

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