Tamilnadu State Board New Syllabus Samacheer Kalvi 12th Bio Botany Guide Pdf Chapter 6 Principles of Ecology Text Book Back Questions and Answers, Notes.

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

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

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

I. Choose the correct evaluation

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:
c. Community → Ecosystem → Landscape → Biome

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:
d. ii and iii only

Samacheer Kalvi 12th Bio Botany Guide 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:
b. ii, iii and iv correct answer

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

Question 5.
Which of the given plant produces cardiac glycosides?
a. Calotropis
c. Nepenthes
b. Acacia
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

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

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.
i) Total soil water content in soil is called ……………………………..
ii) Soil water not available to plants is called ……………………………
iii) Soil water available to plants is called ……………………..

(i)(ii)(iii)
a. HolardEchardChresard
b. EchardHolardChresard
c. ChresardEchardHolard
d. HolardChresardEchard

Answer:
a) i – Holard, ii-Echard, iii-Chresard

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

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

Column -IColumn – II
I. 0.2 to 2.00 mmi. Slit soil
II. Less than 0.002 mmii. Clayey soil
III. 0.002 to 0.02 mmiii. Sandy soil
IV. 0.002 to 0.2 mmiv. Loamy soil

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 1

Answer:
c) I (iii), II (ii), III (i), IV (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:
d. Halophytes

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

Question 12.
Identify the A, B, C and D in the given table

InteractionEffects on species XEffects on species Y
MutualismA(+)
B(+)(-)
Competition(-)C
D(-)0

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 2
Answer:
a) A (+) B – Parasitism, C (-), D – 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 Guide Chapter 6 Principles of Ecology

Question 14.
A free living nitrogen fixing cyanobacterium which can also form symbiotic association with the water fern 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:
b. Absorbing inorganic ions from soil

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:
c. Nerium

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

Question 18.
In a fresh water environment like pond, rooted autotrophs are
a. Nymphaea and typha
b. ‘ CeratophyllumandUtricularia
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:

Column I
(Interaction)

Column -II
(Examples)

MutualismTrichoderma and Penicillium
CommensalismBalanophora, Orobanche
ParasitismOrchids and Ferns
PredationLichen and Mycorrhiza
AmensalismNepenthes and Diaonaea

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 3
Answer:
d (I) iv, (II) iii, (III) ii, (IV) v, (V) i

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

Question 20.
Strong, sharp spines that get attached to animal’s feet are found in the fruits of
a. Ar gemone
b. Ecballium
c. Heritier
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

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

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

Question 23.
What is the ecological hierarchy? Name the levels of ecological hierarchy.
Answer:
Ecological hierarchy is the interaction of organisms with their environment results in the establishment of a grouping of organisms. Which is called ecological hierarchy (or) ecological levels of organisation.
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 4

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.

Question 25.
Distinguish habitat and niche
Answer:
Habitat

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

Niche

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

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

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

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

Question 27.
‘Green algae are not likely to be found in the deepest strata of the ocean’. Give at least one reason.
Answer:

  • The deepest strata of the ocean is dark and sufficient light is not available for the photosynthesis of green algae.
  • Algae need brackish water for its growth. Which is also not available in the deepest strata of the ocean.

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 the Albedo effect and write their effects?
Answer:

  • The albedo effect is due to greenhouse effect.
  • Aerosols (suspension of fine solid (or) liquid particles in gas) with small particles is reflecting the solar radiation entering the atmosphere is known as Albedo effect.
  • It reduces the temperature, photosynthesis and respiration
  • The sulphur compounds present in the aerosol are responsible for acid rain due to acidification of rain water and destroy the ozone.

Question 30.
The organic horizon is generally absent from agricultural soils because tilling, e.g., ploughing, 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 weathering process.
  • Biological weathering takes place when organisms like bacteria, fungi, lichens and plants helps 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.

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

Question 33.
Describe the mutual relationship between the fig and wasp and comment on the phenomenon that operates in this relationship.
Answer:

  • Mutualism interaction exist between fig tree and wasp
  • In fig tree there is a tight one to one relationship with a pollinator species of wasp and no other species.
  • The wasp pollinates the fig while finding egg lav ing sites and in turn, the fig offers the wasp developing seeds, as food for the developing larvae.

Question 34.
Lichen is considered as a good example of obligate mutualism. Explain.
Answer:

  • It is an interaction between two species of organisms in which both are benefitted from the obligate association.
  • Lichens is a mutual association of algae and a fungus.
  • The alga is usually green alga (or) blue green alga. The fungus is an ascomycete (or) basidiomycete.
  • It is believed that alga contributes organic food from photosynthesis and the fungus is able to absorb water and mineral salts.
  • The fungus can also conserver water and this enables lichens to grow in extremely dry conditions where no other plants can exist.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 5

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

  • Mutualism is an interaction between two species of organisms in which both are benefitted from their association.
  • Eg: 1 – Water Fern (Azolla) and Nitrogen fixing Cyanobacterium (Anabaena)
  • Eg: 2 – Roots of terrestrial plants and fungal hyphae – Mycorrhiza.

Question 36.
List any two adaptive features evolved in parasites enabling them to live successfully on their host?
Answer:
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 manv 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.

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.
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 6

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

Question 37.
Mention any two significant roles predation plays in nature.
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 prey.
  • The predator is benefitted while the prey is harmed.

Examples:
A number of plants like Drosera (Sundew Plant), Nepenthes (Pitcher Plant), Diaonaea (Venus flytrap), Utricularia (Bladderwort), and Sarracenia are predators
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 7

  • which consume insects and other small animals for their food as a source of nitrogen.
  • They are also called insectivorous plants.
  • Many herbivores are predators. Cattles, Camels, Goats, etc., frequently browse on the tender shoots of herbs, shrubs, and trees.
  • Generally, annuals suffer more than perennials.
  • Grazing and browsing may cause remarkable changes in vegetation.
  • Nearly 25 percent of all insects are known as phytophagous (feeds on plant sap and other parts of the plant)

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 8
Many defense mechanisms are envoloved to avoid their predations by plants.
Calotropis produces highly poisonous cardiac glycosides.
Tobacco: Produces nicotine.
Coffee: coffee plants produce coffeine.

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

Question 38.
How does an orchid ophrys ensure 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:

  • Xerophytes are the plants which are living in dry (or) xeric condition are known as xerophytes.

Adaptations of xerophytes:

  • Root system is well developed and is greater than that of shoot system.
  • In some xerophytes all the internodes in the stem are modified into a fleshy leaf structure called phvlloclades (Opuntia)
  • In some the petiole is modified into a fleshy leaf like structure called phyllode (Acacia melanoxylon).

Question 40.
Why do submerged plants receive weak illumination than exposed floating plants in a lake?
Answer:

  • Submerged plants which receive weak illumination because
  • Submerged plants are completely immersed in water and not in contact with the atmosphere (or) surface of the water.
  • The floating hydrophytes float freely (or) float their leaves and flowers on the surface of water do not allow light to pass inside the lake.
  • So submerged plants receive weak illumination than exposed floating plants.

Question 41.
What is vivipary? Name a plant group which exhibits vivipary.
Answer:

  •  Vivipary is the special type of seed germination
  • During germination, the seed is till attached to the parent plant and nourished by it.
  • Vivipary generally occurs in mangrove plants.
  • The mangrove plants are medium sized trees which grow in salty marshes of sea coasts. (Eg.) Rhizophora, Sonneratia, Avicennia.
  • The seeds of this plant cannot germinate on the marshy habitat because of the excessive salt concentration and lack of oxygen.
  • The radicle of the plant elongates considerably and projects out of the fruit.
  • Then dark like seedling breaks off from the parent plant.
  • Then radicle immediately forms new roots and establishes the seedling as a new plant.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 9

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

Question 42.
What is thermal stratification? Mention their types.
Answer:
Thermal Stratification is usually found in aquatic habitats. 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 a 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 bodyguards 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 a seed ball?
Answer:

  • It is a method of human aided seed dispersal r 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 suitable ground, not planting of trees manually.
  • This method is suitable for barren and degraded lands for tree regeneration and vegetation before the monsoon period where the suitable dispersal agents become rare.

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

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

AnemochoryZoochory
1. Individual seeds (or) the whole fruit may be modified to help for the dispersal by wind, wind dispersal of fruits and seeds is quite common in tall trees.1. Birds and mammals, including human beings play an efficient and important role in the dispersal of fruit and seeds.
2. Minute seeds are very small light and with inflated covering. (Eg.) Orchids.

 

2. The surface of the fruits (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 disposed.
3. Seeds (or) whole fruits are flattened to form a wing .(Eg.) Maple, Gyrocarpus

 

3. Some fruits and seeds have sticky glandular hairs by which they adhere to the fur of grazing animals.
(Eg.) Boerhaavia and cleome
4. Seeds (or) fruits may have feathery appendages which greatly increase their buoyancy to disperse to high altitudes. (Eg.) Asclepias and vernonia.4. Some fruits have viscid layers (sticky layer) which adhere to the beak of the bird which eats them and when they rub them on to the branch of the tree, they disperse and germinate. (Eg.) Cordia, Alangium
Censor mechanismFleshy fruit
The fruits of many plants open in such a way that the seeds can escape only when the fruits are violently shaken by a strong wind.Some fleshy fruits with conspicuous colours are dispersed by a human being to distant places after consumption.
(Eg.) Mango and Papaya.

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

Question 48.
Explain Raunkiaer classification of the world’s vegetation based on temperature.
Answer:
Based on the temperature prevailing in an area, Raunkiaer classified the world’s vegetation into the following four types.

They are megatherms, mesotherms, microtherms, and hekistotherms.
In thermal springs and deep sea hydrothermal vents where average temperature exceed 100°c.

Based on the range of thermal tolerance, organisms are divided into two types.

  • Eurythermal: Organisms which can tolerate a wide range of temperature fluctuations.
    (Eg.) Zostera (A marine Angiosperm) and Artemisia tridentata.
  • Stenothermal: Organisms which can tolerate only a small range of temperature variations.
    (Eg.) Mango and Palm (Terrestrial Angiosperms).

Mango plants do not and cannot grow in temperate countries like Canada and Germany.

Thermal stratifications:
It 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 stratification

  1. Epilimniotn 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.

Temperature based zonation:
Variations are latitude and altitude do affect the temperature of the vegetation on the earth’s surface.
Latitude: Latitude is an angle which ranges from 0° at the equator to 90° at the poles.
Altitude: How High a place is located above the sea level is called the altitude of the place.

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

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

  • A fire has a direct lethal effect on plants
  • Burning scars are suitable places for the entry of parasitic fungi and insects
  • It brings out the alteration of light, rainfall, nutrient cycle, the fertility of the soil, pH, soil flora, and fauna
  • Some fungi which grow in the soil of burnt areas called pyrophilous. (Eg.) Pyronema confluens.

Question 50.
What is the soil profile? Explain the characters of different soil horizons.
Answer:
Soil Profile:

  • 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 a soil profile.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 10 Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 11

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 Rafflesia 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.

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

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

Question 52.
Explain different types of hydrophytes with examples.
Answer:
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 the following categories:

  • Free floating hydrophytes: These plants float freely on the surface of the water. They remain in contact with water and air, but not with soil. Examples: Eichhornia, Pistia and Wolffia (smallest flowering plant).
  • 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.
  • Submerged floating hydrophytes: These plants are completely submerged in water and not in contact with soil and air. Examples: Ceratophyllum and Utricularia.
  • 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.

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.
Hygrophytes: The plants which can grow in moist damp and shady places are called hygrophytes. (Eg.) Habenaria (Orchid), Mosses (Bryophytes), etc.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 13

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

  • Presence of multilayered epidermis with heavy cuticle to prevent water loss due to transpiration.
  • The hypodermis is well developed with sclerenchymatous tissues.
  • Sunken shaped stomata are present only in the lower epidermis with hairs in the sunken pits.
  • Scotoactive type of stomata found in succulent plants.
  • Vascular bundles are well developed with several layered bundle sheath.
  • Mesophyll is well differentiated into palisade and spongy parenchyma.
  • In succulents the stem possesses a water storage region.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 14

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

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

  • The temperate halophytes are herbaceous but the tropical halophytes are mostly bushy
  • In addition to the normal roots, many stilt roots are developed
  • 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

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 15

  • Presence of thick cuticle on the aerial parts of the plant body
  • Leaves are thick, entire, succulent and glossy. Some species are aphyllous (without leaves).
  • Vivipary mode of seed germination is found in halophytes

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 16

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 helps 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,

i. 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.

ii. 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 a viscid layer which adheres to the beak of the bird which eats them and when they rub them on to the branch of the tree, they disperse and germinate. Example: Cordia and Alangium

iii. Fleshy fruits: Some fleshy fruits with conspicuous colours are dispersed by human beings to distant places after consumption. Example: Mango and Diplocyclos
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 24

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

12th Bio Botany Guide Principles of Ecology Additional Important Questions and Answers

I. Match the following

Question 1.

Column IColumn II
A. StenobathicI. Salinity
B. Stenoecious2. Depth of water/habitat
C. Stenohaline3. Food
D. Stenophagic4 Habitai selection

a. A – (4), B – (1), C – (3), D – (2)
b. A – (3), B – (1), C – (2), D – (4)
c. A – (2), B – (1), C – (4), D – (3)
d. A – (2), B – (4), C – (1), D – (3)
Answer:
d. A – (2), B – (4), C – (1), D – (3)

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

Question 2.

Column IColumn II
A. EurythermalI. Salinity
B. Stenothermal2. Depth of water / habitat
C. Euryhaline3. Food
D. Stenohaline4. Wide range of salinity

a. A – (4), B – (3), C – (2), D – (1)
b. A – (3), B – (1), C – (4), D – (2)
c. A – (1), B – (2), C – (3), D – (4)
d. A – (2), B – (3), C – (4), D – (1)
Answer:
b. A – (3), B – (1), C – (4), D – (2)

Question 3.

Column IColumn II
A ScierophyllousPast climate
B. TimberlineHeavy rainfall throughout the year
C. paleoclimatologyHeavy rainfall during winter.
D. Evergreen forestMarks the level of tree

a. A – (1), B – (2), C – (3), D – (4)
b. A – (2), B – (3), C – (1), D – (4)
c. A – (3), B – (4), C – (1), D – (2)
d. A – (2), B – (3), C – (1), D – (4):
Answer:
c. A – (3), B – (4), C – (1), D – (2)

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

Question 4.

Column IColumn II
A. Altitude1. Physiological activities stop
B. Hypolimnion2. Physiological activities more
C. Maximum temperature3. Place above sea level.
D. Optimum temperature4. Colder water

a. -(1), B – (2), C – (3), D – (4)
b. A -(2), B – (3), C – (1), D – (4)
c. A – (4), B – (3), C – (2), D – (1)
d. A – (3), B – (4), C – (1), D – (2)
Answer:
d. A – (3), B – (4), C – (1), D – (2)

Question 5.

Column IColumn II
Free floating hydrophytei Utricularia
Rooted floating hydrophyteii Pistia
Submerged floating hydrophyteiii Hydrilla
Rooted submerged hydrophyteiv Nymphaea

. A – (ii), B – (iv), C – (i), D – (iii) b. A – (ii), B – (iii), C – (iv), D – (i)
c. A – (iii), B – (iv), C – (i), D – (ii) d. A – (iv), B – (iii), C – (ii), D – (i)

Question 6.

Column IColumn II
Parasitismi (+) (+)
Amensalismii (+) (0)
Mutualismiii (+) (-)
Commensalismiv (-) (0)

Anwer:
a. A – (ii), B – (iv), C – (i), D – (iii)

Question 7.

Column IColumn II
A. Competitioni. Orchids, Lianas
B. Mutualismii. Lichens
C. Amensalismiii. Grassland species
D. Commensalismiv. Penicillium

a. A- (i), B- (iii), C- (ii), D- (iv)
b. A- (i), B- (ii),C- (iii), D- (iv)
c. A- (iv), B- (iii), C- (ii), D (i)
d. A- (ii), B- (iii), C- (i), D- (iv)
Answer:
b. A- (iii),B- (ii),C- (iv),D- (i)

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

Question 8.
Match the following
Read the statement and fill it with correct (A) and (B)
In Halophytes …………….. shape sclereids and …………………. heavily thickened spicules that provide mechanical strength to the cortex are present in the stem.

AB
a. StirrupSickle
b. WedgeSkull
c. Star
d. ‘H’ shapedStar-shaped

Answer:
c) A – Star- B – H-shape

9. Match the following
Read the statement and fill it with correct (A), (B) and (C)
It is the structural defence by plants against fire. The outer bark of trees which extends to the last formed ………… A……………. is called Rhytidome. It is composed of multiple layers of suberised …………..B……………… cortical and ……….C………….. tissues.

ABC
a. CorticalPeridermDefence
b. PeridermCorticalDefence
c. PeridermPeridermPhloem
d. PeridermPeridermXylem

Answer:
c) A-Periderm, B – Periderm, C – Phloem

II. Pick out the correct pair.

A) Oxylophytes – Plants living ice surface
B) Hollard – Total soil water content
C) Chresard – Water not available to plants
D) Echard – Water available to plants
Answer:
B) Hollard – Total soil water content

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

III. Choose the incorrect statements and select the option.

Question 1.
A) Some fungi which grow in soil of burnt areas called pyrophilous
B) Pyronema confluens is the indicator of fire.
C) Lagoons salinity will be more than 100%
D) Low temperature with high humidity helps the plants to become disease-free
a. None of these
b. A alone
c. A, B and C
d. D alone
Answer:
d. D alone

Question 2.
A) Applied ecology help us to manage and conserve the natural resource.
B) Niche – The term was coined by the naturalist Roswell Hill Johnson.
C) Halophytes are the plants which lives in saltwater.
D) Metalimnion is a zone of a gradual decrease in temperature.
a. A and B
b. A, B, and C
c. C and D
d. C alone
Answer:
d. C alone

Question 3.
Choose the incorrect one with respect to type of soil particles.
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 17
Answer:

Question 4.
A) R – Horizon consists of parent bedrock.
B) C – Horizon is partially weathered horizon.
C) B – Horizon is rich in minerals.
D) A – Horizon is often rich in humus and minerals.
a. A, B and C
b. B, C, D
c. None of these
d. C, A, and B
Answer:
c. None of these

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

Question 5.
a. Hollard is total soil water content
b. Echard is water not available to plant
c. The visible part of the light is made up of wavelengths from 400 nm to 700 nm
d. July 06 is Van Mahostav day
Answer:
d. July 06 is Van Mahostav day

VI. Choose the incorrect pair

Question 1.

Column IColumn II
A Halophytes1 Defence against fire
B Cryptophytes2 Bryophytes and pteridophytes
C Sciophytes3 Angiosperms
D Rhytidome4 Plants, below soil surface

a. A – 3), B – 4), C – 2), D – 1)
c. A – 2), B – 3), C – 4), D – 1)
b. A – 4), B – 2), C – 3), D – 1)
d. A – 1), B – 2), C – 3), D – 4)
Answer:
a. A – 3), B – 4), C – 2), D – 1)

Question 2.
Choose the incorrect pair which is related to mimicry.
A) Ophrys an orchid is an example of floral mimicry.
B) Carausius morosus – Stick insect is an example of protective mimicry.
C) Phyllium frondosum – Leaf insect another example of protective mimicry.
D) Ants take their shelter on Mango, Litchi
a. A, Band C b. B, C and D c. C alone d. None of these
Answer:
d. None of these

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

V. Assertion and Reason

Question 1.
Assertion(A): Hypolimniotic layer of water is always cold.
Reason (R): The water holds the temperature of the soil at the bottom of pond
a. (A) correct; (R) wrong
b. Both (A) and (R) are correct, but (R) is not the correct explanation of (A)
c. Both (A) and (R) are correct; (R) is the correct explanation of (A)
d. Both (A) and (R) are wrong.
Answer:
a. (A) correct; (R) wrong

Question 2.
Assertion: Non-succulent plants are called drought resistant plants.
Reason: They have many adaptation to resist dry conditions.
a. A is correct R is wrong
b. A is the wrong R is correct
c. Both are wrong
d. A is correct R is the correct explanation of A
Answer:
d. A is correct R is the correct explanation of A

VI. odd man out

Question 1.
Choose the odd man out:
Hornbills,
Slitz size of pollina of Apocynaceae,
Birds of scrub jungles,
Leg size of insect camel’s foot climber
Answer:
Leg size of insect camel’s foot climber

Question 2.
Choose the odd man out:
Isoetes
Hydrilla,
Potamogeton
Ranunculus Mukia.
Answer:
Ranunculus Mukia

Question 3.
Choose the odd man out:
Argemone,
Mollugo,
Tribulus
Bryophyllum
Answer:
Bryophyllum

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

VII. Pictorial Questions

Question 1.
Observe the diagram and choose their part from the following option.
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 19

a. Petiole, phyllode
b. Stem, leaf
c. Spines, leaves
d. Stem, Scale leaves
Answer:
d. Stem, Scale leaves

Question 2.
Observe the diagram and write the name of this plant.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 20
Answer:
Ceratophyllum

Question 3.
Observe the diagram and choose the correct vegetation option for A, B, C and D
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 21
a. Tundra, ice, treeline, desert
b. Rain, coniferous, tropical, grass land
c. Grass, conifer, tropical, deciduous
d. Coniferous, deciduous, grassland
Answer:
d. Coniferous, deciduous, grassland

Question 4.
Draw the diagram showing altitudinal zonation of vegetation.
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 22

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

VIII. True or False

Question 1.
Read the sentences and select the correct options stating which ones are true (T) and which ones are false (F).
A) Juglone which inhibits the growth of seedlings of Apple, Tomato and Alfalfa around it.
B) Penicillin which inhibits the growth of staphylococcus bacteria.
C) Amensalism is not antibiosis.
D) Trichoderma inhibit the growth of Aspergillus.
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 23
Answer:
C) T, T, F, T

IX. Fill in the blanks Answers

1. Roots and hulls of Black Walnut Juglans nigra secretes an alkaloid……………………………………….
Answer:
Juglone

2. The plants which behave as xerophytes at summer and behave as mesophvtes during rainv season is……………………………….
Answer:
tropophytes

3. The ……………………………….wave length of spectrum is less strongly absorbed by plants.
Answer:
green (500 – 600 nm)

4. The rate of photosynthesis is maximum at blue (400 – 500 nm) and……………………………….
Answer:
red (600 – 700 nm)

5. ……………………………….is well known factor needed for the physiological process of plants.
Answer:
Light

6. In climatology diurnal cycle is the basic form of climatic pattern in every ………………………………..
Answer:
24 hrs.

7. The altitudinal limit of normal tree growth is about ………………………………..
Answer:
3000 to 4000

8. ……………………………….are organisms, which derive onlv water and minerals from their host plant for synthesizing their own food.
Answer:
Hemiparasites

9. ……………………………….is the smallest free floating hvdrophvtes.
Answer:
Wolffia

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

10. Scotoactive tvpe of stomata found in ……………………………….plants.
Answer:
succulent

11. ……………………………….are plants which grow perched on other plants.
Answer:
Epiphytes

12. The plants which are living in moderate conditions (neither too wet nor too drv) are known as……………………………….
Answer:
Mesophytes

13. ……………………………….is the world forest dav.
Answer:
March – 21

14. Earth dav falls on……………………………….
Answer:
April – 22

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

15. International ozone dav is celebrated on……………………………….
Answer:
September -16

X. Choose the correct answer

Question 1.
Which one of the following is not related to mutualism.
a. Anabaena present in coralloid root of cycas.
b. Wasps present in fruits of fig.
c. Tillandsia grows on the bark of oak and pine trees.
d. Cyanobacterium (Nostoc) found in the thalloid body of Anthoceros.
Answer:
c. Tillandsia grows on the bark of oak and pine trees.

Question 2.
Dionaea, Bladder wort and sarracenia are
a. Epiphytes
b. Commensals
c. Predators
d. Parasites
Answer:
c. Predators

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

Question 3.
Tobacco produces nicotine, coffee plants produce caffeine, cinchona plant produce quinine it is meant for…………….
a. Predators
b. Defence mechanism
c. Proto cooperation
d. Holoparasites
Answer:
b. Defence mechanism

Question 4.
Which of the following is not related to parasitism.
a. Acacia, Duranta – cuscuta
b. Balanophora,Orabanche and Refflesia – higher plants.
c. Pitcher plant with insect
d. Viscum and Loranthus – Stem parasite
Answer:
c. Pitcher plant with insect

Question 5.
Which plant pods explodes with a loud noise like cracker?
a. Boerhaavia
b.Cleome
c. Bauhinia vahlii
d.Ecballium elatrium
Answer:
d. Ecballium elatrium

Question 6.
Casuarina, Nerium, Ziziphus and Acacia examples for
a.Truexerophytes
b. Succulents
c. Ephemerals
d. Phyllode
Answer:
a. True xerophytes

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

Question 7.
Root pockets are present in
a. Eichhornia
b. Nelumbo
c. Potamogeton
d. Ceratophyllum
Answer:
a. Eichhornia

Question 8.
Stenophagic means
a. The organism can survive by taking wide range of food.
b. The organism can survive by taking narrow range of food.
c. The organism can live in water with wide range of salinity
d. The organism can live in water with narrow range of salinity.
Answer:
a. The organism can survive by taking wide range of food.

Question 9.
In euphorbia, acacia, ziziphus and capparis are modified into spines.
a. Stipules
b. Scales
c. Leaves
d. Bud
Answer:
a. Stipules

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

Question 10.
Latitude, altitude, direction of mountain, steepness of mountain etc are factors.
a. Topographic
b. Ecotone
c. Altitude
d. Edge effect
Answer:
a. Topographic

Question 11.
The roots of orchids which contain special type of spongy tissue called
a. Xylem
b. Phloem
c. Parenchyma
d. V elamen
Answer:
d. Velamen

Question 12.
Thorns of Bougainvillea, spines of opuntia and latex of cacti protect them from
a. Drought
b. Parasites
c. Predators
d. Insects
Answer:
c. Predators

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

Question 13.
Which seeds showing highest longevity in plant kingdom.
a. Lotus
b. Hydrilla
c. Nymphaea
d. Marsilea
Answer:
a. Lotus

Question 14.
plants are completing life cycle within a short period.
a. Lotus
b. Hydrilla
c. Nymphaea
d. Marsilea
Answer:
a. Lotus

XI. Two Marks

Question 1.
What is biotope and ecotope?
Answer:
The environment of any community is called biotope.
The habitat and niche of any organism is called ecotope.

Question 2.
What is biome?
Answer:
Biome is a large naturally occurring community of flora and fauna occupying in a major habitat. (Eg.) forest, fundra

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

Question 3.
Difference between evergreen forest and sclerophyllous forest?
Answer:
Evergreen forest
It is found where heavy rainfall occurs throughout the year.

Sclerophyllous forest
It is found where heavy rainfall occurs during winter and low rainfall during summer.

Give reason for the following

  • Species of the grass lands of western ghats of India differ from the grass species of temperate grass lands of steppe in North America. But they are all ecologically primary producers.
  • Taxonomically different species occupying similar habitats (Niche) in different geographical regions are called ecological equivalents.

Question 4.
What are the various latitudinal zonation of vegetation ?
Answer:
Tropical rain forest, grassland (or) desert, deciduous forest, coniferous forest, treeline (or) tundra, snow (or) ice.

Question 5.
What are the various altitudinal zonation of vegetation?
Answer:
Tropical rain forest, grassland (or) desert, deciduous forest, coniferous forest, tundra snow are the various vegetation of altitudinal zonation.

Question 6.
Differentiate between euryhaline and stenohaline.
Answer:
Euryhaline Stenohaline

  1. Organisms which can live in water with wide range of salinity.
  2. (Eg.) Marine algae and marine angiosperms

stenohaline.

  1. Organisms which can withstand only small range of salinity.
  2. (Eg.) Plants of estuaries

Question 7.
What is albedo effect ?
Answer:

  • Aerosols with small particles is reflecting the solar radiation entering the atmosphere called albedo effect.
  • It reduces the temperature limits, photo synthesis and respiration.

Question 8.
Define : Indicators of fire (or) Why pteris and pyronema are called as fire indicators?
Answer:

  • Some pteris are well adapted to grow in burnt and highly disturbed area
  • Pteris (fern) and pyronema (fungus) indicates the burnt up and fire disturbed areas.
  • So they are called indicators of fire.

Question 9.
What is edge effect?
Answer:

  • Some species are found in the ecotone areas border between forest and grassland due to the effect of the environment of the two habitats. This is called the edge effect.
  • (Eg.) Owl in the ecotone area between forest and grassland.

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

Question 10.
What is the ecotone area?
Answer:
The transition zone between two ecosystems. (Eg.) The border between forest and grassland.

Question 11.
Why do valleys are rich in vegetation compare to the steepness of the mountain?
Answer:

  • The steepness of the mountain (or) hill allows the rain to run off.
  • Asa 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 retention of water in the soil.

Question 12.
Draw the picture and mark the A and B.
Write the name of the plant which is present on the host trunk.
Answer:
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 25

Question 13.
Write the examples for the following type of holo parasites (or) total parasites.
a) Total stem parasite:………………
b) Total root parasite on higher plants :……………., …………………, ……………..
Answer:
a) Cuscuta
b) Balanophora, Orobanche and Reflesia.

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

Question 14.
Write the examples for the following type of hemi parasites (or) partial parasites.
a) Partial stem parasite :……………… , ………………
b) Partial root parasite:………………
Answer:
a) Viscum and Loranthus
b) Santalum (sandal wood)

Question 15.
“The utricularia (Bladderwort) competes with tiny fishes for small crustaceans and insects” What type of interaction exist in the above examples.
Answer:

  • Inter-specific competition is exist in the above examples.
  • It is an interaction between individuals of different species for common need.

Question 16.
What is intra specific competition ?
Answer:

  • It is an interaction between individuals same species.
  • It is very severe because all the members of species have similar requirement of food habitat, pollination etc.

Question 17.
What is the competition?
Answer:
It is an interaction between two organisms (or) species in which both the organisms (or) species are harmed.

Question 18.
What is junglone?
Answer:
Roots and hulls of black walnut junglone nigra secretes an alkaloid junglone.

  • Which inhibits the growth of seedlings of apple,tomato and alfalfa around it.
  • It is an example for amensalism type of interspecific interaction.

Question 19.
What are trichophyllous plants? Give example.
Answer:
In xerophytes, the leaves and stem are covered with hairs are called trichophyllous plants. (Eg.) cucurbits, (melothria and mukia)

Question 20.
Orchids, money plant and lianas are epiphytes. Why? (or) What are epiphytes give an example.
Answer:

  • Many orchids ferns, lianas, money plant usnea (lichen) are some of examples of epiphytes.
  • These plants which are found on other plants and growing without harming them are called epiphytes.

Question 21.
What are tropophytes?
Answer:
Tropophytes are plants which behave as xerophytes at summer and behave as mesophytes (or) hydrophytes during rainy season.

Question 22.
Seeds of maple gyrocarpus, dipterocarpus and terminalia exhibit which type of adaptations for dispersal of fruits and seeds?
Answer:
Seeds (or) whole fruits are flattened to form a wing for dispersal by wind.

Question 23.
Guess !! Who am I………….? I am dispersed by ant and I have caruncle.
Answer:

  • Caruncle is a structure found in micropylar region of euphorbiaceae seeds, that attract ants. Which feed the caruncle to their larvae.
  • Then ants leave the seed to their waste disposal area. Where the seeds germinate.
  • This type of seed dispersal called myrmecophily.

Question 24.
What are xerophytes ? What are its types ?
Answer:
Xerophytes are plants, which are living in dry (or) xeric conditions are known as xerophytes. They are a) Physical dryness, b) Physiological dryness

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

Question 25.
In some habitats, water is sufficiently present but plants are unable to absorb it. Why? How do you call it?
Answer:

  • It is called physiological dryness.
  • In these habitats, water is sufficiently present but plants are unable to absorb it because of the absence of capillary spaces.
  • (Eg.) Plants in salty and acidic soil.

Question 26.
Define pedology
Answer:
The study of soils is called pedology

Question 27.
What is palaeoclimatology? Give an example.
Answer:

  • Helps to reconstruct past climates of our planet and flora, fauna and ecosystem in which they lived.
  • Example : Air bubbles trapped in ice for tens of thousands of years with fossilized pollen, coral, plant and animal debris.

Question 28.
What is sclerophyllous forests?
Answer:
Found where heavy rainfall occurs during winter and low rainfall during summer.

Question 29.
Define Anemometer?
Answer:

  • Air in motion is called wind.
  • It is also a vital ecdogical factor.
  • The atmospheric air contains a number of gases, particles and other constituents.
  • Anemometer is the instrument used to measure the speed of wind.

Question 30.
Which is Nitrogen fixation?
Answer:
Rhizoblum (Bacterium) forms nodules in the roots of leguminous plants and lives symbiotically.
The Rhizobium obrains food from leguminous plant and in turn fixes atmospheric nitrogen in to nitrate, making it available to host plants.

XII. Three Marks

Question 1.
Is there any limit of tree growth related to altitude ? (or) What is treeline or timberline?
Answer:

  • Timberline (or) tree 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.

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

Question 2.
How does Rhytidome protect the plant against forest fire?
Answer:

  • It is the structural defense by plant against.
  • 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 tissue. It protects the stem against fire, water loss, invasion of insects and prevents infections by microorganism

Question 3.
Which branch of ecology help us to manage and conserve natural resources, particularly ecosystem? (or) What is applied ecology (or) environmental technology?
Answer:
Applied ecology (or) environmental technology helps us to manage and conserve natural resource particularly ecosystems, forest and wild life conservative management.

Environmental management involves bio-diversity, conservation, ecosystem restoration, habitat management, invasive SPS management protected areas management and also help us plan landscapes and environmental impact designing for the futuristic ecology.

Question 4.
What are ecological factors (or) environmental factors?
Answer:

  • Many organisms co-exist in an environment.
  • The environment includes physical, chemical biological component.
  • When a component surrounding an organism affects the life of an organism called factor.
  • These factors may be biotic and abiotic.

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

Question 5.
What are the environmental factors affecting a plant life?
Answer:

  • Climatic factors : Sunlight, precipitation wind, carbon dioxide and water vapour.
  • Biotic factors : Birds, insects, man, grazing animals, rodents, plant pathogens and epiphytes.
  • Edaphic factors : Soil slope, soil water, physical nature of soil, minerals, soil air.

Question 6.
What are the various effects of light upon a green plant ?
Answer:
Various effects of light on green plants are photosynthesis, opening and closing of sto¬mata movements, germination of seeds, flowering tuber formation, runner production stem and leaf formation.

Question 7.
What is phytoremediation ? Given Example.
Answer:
Some plants are used to remove cadmium from contaminated soil is known as phyto remediation. tM.-fTiVM
(Eg.) Rice and eichhornia tolerate cadmium by binding it to their proteins.
Soybean and tomato manage to tolerate cadmium by storing into few group of cells.

Question 8.
Which soil is ideal for cultivation ? (or) Why loamy soil is ideal for cultivation ?
Answer:

  • Loamy soil is ideal for cultivation. It consist of 70% sand and 30% clay (or) silt.
  • It ensures good retention and proper drainage of water.
  • The porosity of soil provides adequate aeration and allows the penetration of roots.

Question 9.
What is soil profile (or) super-imposed 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.

Question 9.
Differentiate species ecology from community ecology.
Answer:
Species Ecology :
It is the study of a group of individual of particular species, (population)

Community Ecology :
It is the study of several species that are living together as a community (made up of several populations)

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

Question 10.
Why do vegetation at different altitude are varies ?
Answer:
Height above the sea level forms the altitude.
At high altitudes

  • The velocity of wind remains high.
  • Temperature and air pressure-decreases.
  • While humidity and intensity of light increases.

Due to these factors vegetation at different altitudes varies showing distinct zonation.

Question 11.
Why do different types of vegetation occur from equator to poles (or) latitudes?
Answer:

  • Latitudes represent distance from the equator.
  • Temperature values are maximum at the equator and decrease gradually towards poles.
  • So different types of vegetation occur in latitude.

Question 12.
What is topography? WTiat are its factors?
Answer:

  • The surface features of earth are called topography.
  • Its factors include, latitude, altitude, direction of mountain, steepness of mountain.

Question 13.
Spanish Moss-Tillandsia grows on the bark of oak and pine trees. Which type of interactions exist in the above examples ?
Answer:

  • They were epiphytes showing commensalism type of positive interaction.
  • In which one is benefitted and other is neither benefitted nor harmed.
  • The species that derives benefit is called the commensal, while the other species is called the host.

Question 14.
What is velamen?
Answer:

  • The epiphytic higher plant gets its nutrients and water from the atmosphere with the help of their hygroscopic roots.
  • These roots contain special type of spongy tissue called velamen.

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

Question 15.
What is proto cooperation?
Answer:
An interaction between organisms of different species in which both organisms benefit but neither is dependent on the relationship.
(Eg.) Soil bacteria, fungi and plants growing in the soil.

Question 16.
Draw the picture and mark A, B and C
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 26
Answer:
A – Tendril, B – Pitcher, C – Lamina

Question 17.
Draw the diagram mark A, B and C.
Answer:
A – Haustoria, B – Host, C – Parasite

a) Name the parasite with example.
Answer:
Holoparasite Cuscuta.
Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 27

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

Question 18.
What are holo parasites ? (or) total parasites.
Answer:
The organisms which are dependent upon the host plants for their entire nutrition are called holo parasites (or) total parasites. (Eg.) Cuscuta.

Question 19.
Trichoderma (fungus) inhibits the growth of fungus aspergillus. Why ? (or) What is amensalism? (or) WTiat is antibiosis?
Answer:

  • It is an inter specific interaction in which one species is inhibited while the other species is neither benefitted nor harmed.
  • The inhibition is achieved by secretion of chemicals called allelopathic substances.

Question 20.
Phyllium frondosum, carausius morosus exhibit what type of interactions ? (or) WTiat is mimicry?
Answer:

  • It exhibits mimicry of inter specific interactions (or) mimicry of co-evolutionary dynamics.
  • Mimicry is a phenomenon in which living organism modifies its form appearance structure (or) behaviour and looks like another living organism as a self defence and increases the chance of their survival.

Question 21.
What is kairomones ? (or) Which type of defence induced by the predator to the progeny of wild radish?
Answer:
kairomone is a chemical substance emitted by pieris rapae caterpillar (butterfly) exposed to wild radish gets the capacity to transmit defence induced by predator (butterfly) to progeny of wild radish.

Question 22.
Name the phenomenon which is exhibited by acacia and acacia ants ? What does it says?
Answer:

  • Sometimes, ants take their shelter on some trees such as Mango, Litchi, Jamun, 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 acacia ants.

Question 23.
What is hygrophytes ? Why do they call so ?
Answer:
The plants which can grow in moist damp and shady places are called hygrophytes.
(Eg.) Habenaria (orchid),
Mosses (Bryophytes)

Question 24.
How do mangroves work to protect us from natural disaster with example.
Answer:

  • Mangroves protect vulnerable coastal areas from wave action by holding the soil together and prevent coastal erosion.
  • Out of three districts of Tamil Nadu (Nagapattinam, Thanjavur and Thiruvarur), Muthupet (Thiruvarur district) was less damaged by Gaja Cyclone (Nov-2018) due to the presence of mangrove forest.

Question 25.
Some plants are called drought evaders. Why?
Answer:

  • Ephemerals are called drought evaders (or) drought escapers because
  • These plants complete their life cycle within a short period, (single season)
  • (Eg.) Argemone, Mollugo, Tribulus, Tephrosia.

Question 26.
What is the source of energy in deep sea?
Answer:

  • In deep sea (>500 m) the environment is dark and its inhabitants are not aware of the existence of celestial source of energy called sun.
  • Dead sea organisms use chemical energy rather than energy from sunlight.
  • Chemosynthesis is a process, special bacteria use this process to produce energy without using sunlight.

Question 27.
Write any four ecologically important days.
Answer:

  • March 21 – World Forest Day
  • May 22 – World Biodiversity Day
  • June 05 – World Environment Day
  • July 07 – Van Mohot Stav day.

Question 28.
What is phylloclades (or) fleshy leaf? Give an example
Answer:
In some xerophytes all the internode in the stem are modified in to a fleshy leaf structure is called phylloclades.
Ex.→ opuntia

Question 29.
What is breathing roots? Give an example.
Answer:
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

Question 30.
Define cladode? Give an example
Answer:
In some of the others single or occasionally two internodes modified into fleshy green structure called cladode Example: Asparagus

Question 31.
Define phyllode?
Answer:
In some the petiole is modified into a fleshy leaf like structure called phyllode (Acacia melonoxylon)

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

XIII. Five Marks

Question 1.
What are the various zonation based on climatic factor temperature and its effects ?
Answer:
Temperature based zonation:

  • Variations in latitude and altitude do affect the temperature and the vegetation on the earth surface.
  • Timber line / Tree line : It 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 4000m.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 28
Effects of temperature:

  • The following physiological processes are influenced by temperature:
  • Temperature affects the enzymatic action of all the bio-chemical reactions in a plant body.
  • It influences CO2 and O2 solubility in the biological systems. Increases respiration and stimulates growth of seedlings.
  • Low temperature with high humidity can spread diseases to plants
  • The varying temperature with moisture determines the distribution of the vegetation types.

Question 2.
What are the important climatic effects of wind on plants ?
Answer:
Effects of wind:

  • Wind is an important factor for the formation of rain
  • Causes wave formation in lakes and ocean, which promotes aeration of water
  • Strong wind causes soil erosion and reduces soil fertility
  • Increases the rate of transpiration
  • Helps in pollination in anemophilous plants
  • It also helps in dispersal of many fruits, seeds, spores, etc.
  • Strong wind may cause up-rooting of big trees
  • Unidirectional wind stimulates the development of flag forms in trees.

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

Question 3.
Write about important edaphic factors which affect vegetation of plants ?
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 temperature:
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, earthworms, etc. are called soil organisms.

Question 4.
What is topography? What are the various topographic factors involves (or) influence on the climate of any area ?
Answer:
The surface features of earth are called topography. Its factors include, latitude, altitude, direction of mountain, steepness of mountain.

a. Latitudes and altitudes:

  • Latitudes represent distance from the equator. Temperature values are maximum at the equator and decrease gradually towards poles.
  • So different types of vegetation occur in latitude.
  • Height above the sea level forms the altitude. At high altitudes
  • The velocity of wind remains high. Temperature and are pressure – decrease While humidity and intensely of light increases.
  • Due to these factors vegetation at difference altitudes varies showing distinct zonation.

b. Direction of mountain:
North and south faces of mountain (or) hill possess different types of flora and fauna because thev differ in their humidity, rainfall light intensity, light duration and temperature regions.

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 retention of water in the soil.

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

Question 5.
What are various biotic factors which is exist between the organism ?
Answer:
The interactions among living organisms such as plants and animals are called biotic factors.

Positive interactions:
When both (or) one the participating species are benefited. (Eg.) Mutualism and commen¬salism.

Mutualism:

  • It is an interaction between two species of organisms in which both are benefitted from the obligate association.
  • Lichens is a mutual association of an algae and a fungus.
  • The alga is usually green alga (or) blue green alga. The fungus is an ascomycete (or) basidiomycetes.
  • It is believed that alga contributes organic food from photosynthesis and the fungus is able to absorb water and mineral salts.
  • The fungus can also conserve water and this enables lichens to grow in extreme dry conditions where no other plants can exist.

Nitrogen fixation:

  • Rhizobium (Bacterium) forms nodules in the roots of leguminous plants and lives symbiotically.
  • The Rhizobium obtains food from leguminous plant and in turn fixes atmospheric nitrogen into nitrate, making it available to host plants.
  • Example: Water fern (Azolla) and Nitrogen fixing cyanobacterium (Anabaena)
  • Anabaena present in coralloid roots of cycas

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 29

Commensalism:
Many orchids ferns, lianas, money plant usnea (lichen) are some of the examples of epiphytes.
These plants which are found on other plant and growing without harming them are called epiphytes.

Negative interactions:

a. 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.

Examples:
A number of plants like Drosera (Sun dew Plant), Nepenthes (Pitcher Plant), Dionaea (Venus fly trap), Utricularia (Bladder wort) and Sarracenia are predators which consume insects and other small animals for their food as a source of nitrogen. They are also called as insectivorous plants.

Many herbivores are predators. Cattles, Camels, Goats etc., frequently browse on the tender shoots of herbs, shrubs and trees. Generally annuals suffer more than the perennials. Grazing and browsing may cause remarkable changes in vegetation. Nearly 25 percent of all insects are known as phytophagous(feeds on plant sap and other parts of plant)

Question 6.
Write the morphological adaptations of xerophytes.
Answer:
Morphological Adaptations:
In root:

  • Root system is well developed and is greater than that of shoot system.
  • Root hairs and root caps are also well developed.
  • In Xerophytic plants with the leaves and stem are covered with hairs are called tricho- phyllous plants.
  • Eg: Cucubits (Melothria andMukia)

In stem:

  • Stems are mostly hard and woody. They may be aerial or underground.
  • The stems and leaves are covered with wax coating or covered with dense hairs.
  • In some xerophytes all the internodes in the stem are modified into a fleshy leaf structure called phylloclades (Opuntia)
  • In some of the others single or occasionally two internodes modified into fleshy green structure called cladode (Asparagus)
  • In some the petiole is modified into a fleshy leaf like structure called phyllode (Acacia melanoxylon)

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 30

a) A succulent xerophyte: Phylloclade – opuntia
b) Non succulent: Perennial – Capparis
c) Cladode of Asparagus
d) Phyllode – Acacia
aquatic and terrestrial modes of life. They grow in shallow water.
Examples: Ranunculus, Typha and Sagittaria.

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

Question 7.
Write anatomical and physiological adaptation of hydrophytes ?
Answer:
Anatomical adaptations:

  • Cuticle is either completely absent or if present it is thin and poorly developed
  • Single layer of epidermis is present
  • Cortex is well developed with aerenchyma
  • Vascular tissues are poorly developed. In emergent forms vascular elements are well developed.
  • Mechanical tissues are generally absent except in some emergent forms. Pith cells are sclerenchymatous.

Physiological adaptations of hydrophytes:

  • Hydrophytes have the ability to withstand anaerobic conditions.
  • They possess special aerating organs.

Question 8.
What are epiphytes ? What are its morphologic adaptations?
Answer:
Epiphytes:
Epiphytes are plants which grow perched on other plants (Supporting plants). They use the supporting plants only as shelter and not for water or food supply.
Orchids, Lianas, Hanging Mosses and Money plant.

Morphological adaptations:

  • 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.
  • Stem of some epiphytes are succulent and develop pseudo bulb or tuber.
  • Generally the leaves are lesser in number and may be fleshy and leathery Myrmecophily is a common occurrence in the epiphytic vegetation to prevent the predators.

Question 9.
Write about anatomical and physiological adaptations of epiphytes ?
Answer:
Anatomical adaptations:

  • Multilayered epidermis is present. Inner to the velamen tissue, the peculiar exodermis layer is present.
  • Presence of thick cuticle and sunken stomata greatly reduces transpiration.
  • Succulent epiphytes contain well developed parenchymatous cells to store water.

Physiological adaptations:
Special absorption processes of water by velamen tissue.

Samacheer Kalvi 12th Bio Botany Guide Chapter 6 Principles of Ecology 31

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

Question 10.
Write about anatomical and physiological adaptations of halophytes ?
Answer:
Anatomical adaptations:

  • Epidermal cells of stem is heavy cutinized, almost squarish and are filled with oil and tannins.
  • Star’ shaped sclereids and ‘H’ shaped heavy thickened spicules that provide mechanical strength to cortex are present in the stem.
  • The leaves may be dorsiventral or isobilateral with salt secreting glands. Physiological adaptations:
  • High osmotic pressure exists in some plants
  • Seeds germinate in the fruits of mother plant itself (Vivipary).

Question 11.
What are the adaptations found in hy drochory plants with example ?
Answer:
Dispersal of seeds and fruits by water usually occurs in those plants which grow in or near water bodies. Adaptation of hy drochory are

  • Obconical receptacle with prominent air spaces. Example: Neliimbo.
  • Presence of fibrous mesocarp and light pericarp. Example: Coconut.
  • Seeds are light, small, provided with aril which encloses air. Example: Nymphaea.
  • The fruit may be inflated. Examples:

Heritiera littoralis.

  • Seeds by themselves would not float may be carried by water current.
    Example: Coconut.

Question 12.
Write about the various adaptation of wind dispersal plant (or) anemochory plants.
Answer:
The individual seeds or the whole fruit may be modified to help for the dispersal by wind. Wind dispersal of fruits and seeds is quite common in tall trees.

  • Minute seeds: Seeds are minute, very small, light and with inflated covering. Example: Orchids.
    Wings : Seeds or whole fruits are flattened to form a wing. Examples: Maple, Gyrocarpus, Dipterocarpus and Terminalia
  • Feathery Appendages : Seeds or fruits may have feathery appendages which greatly increase their buoyancy to disperse to high altitudes. Examples: Vernonia and Asclepias.
  • Censor mechanisms : The fruits of many plants open in such a way that the seeds can escape only when the fruit is violently shaken by a strong wind. Examples: Aristolochia and Poppy.

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

Question 13.
What is autochory? Write about its explosive mechanism for dispersal of fruits and seeds.
Answer:

  • Some fruits burst suddenly with a force enabling to throw seeds to a little distance away 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 water particularly after a shower of rain, burst suddenly with a noise and scatter the seeds. Examples: Ruellia and Crossandra.
  • Certain long pods explode with a loud noise like cracker, scattering the seeds in all directions. Example: Bauhinia vahlii (Camel’s foot climber)
  • As the fruit matures, tissues around seeds are converted into a mucilaginous fluid, due to which a high turgor pressure develops inside the fruit which leads to the dispersal of seeds.
  • Example: Ecballium elaterium (Squirting cucumber) Gyrocarpus and Dipterocarpus.

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

Question 14.
Explain the role of wind as a vital Ecological
Answer:

  • Air in motion is called wind. It is also vitral ecological factor.
  • The atmospheric air contains a number of gases, particles and other constituents.
  • The composition of gases in atmosphere is as follows
  • Nitrogen – 78%, Oxygen – 21%., Carbon-di¬oxide – 0.03%., Argon and other gases – 0.93%.
  • The other components of wind are water vapour, gaseous pollutants, dust, smoke particles, microorganisms pollen grains, spores etc.
  • Anemometer is the instrument used to measure the speed of wind.