RBSE Solutions for Class 11 Biology Chapter 39 Environmental Factors

Rajasthan Board RBSE Class 11 Biology Chapter 39 Environmental Factors

RBSE Class 11 Biology Chapter 39 Multiple Choice Objective Questions

Question 1.
Which of the following factor primarily decides the vegetation of a region-
1. Climatic
2. Topographical
3 . Biotic
4. Edaphic

Question 2.
Most suitable for plant growth –
1. Sand soil
2. Loam soil
3. Clay soil
4. Gravel

Question 3.
Which type of water is absorbed by the plants –
1. Gravitational water
2. Hygroscopic water
3. Capillary water
4. Run off water

Question 4.
Root cap is normally absent in –
1. Hallophytes
2. Xeropliytes
3. Hygrophytes
3. Mesophytes

RBSE Solutions for Class 11 Biology Chapter 39 Environmental Factors

Question 5.
Many hygrophytes disappear from the pond during summer because –
1. More light is present
2. Plants migrate towards shadow places
3. Plants die because of evaporation
4. CO2 concentration in water is reduced due to high temperature. As a result plants couldn’t perform sufficient photosynthesis.

Answers :
(1). 1
(2). 2
(3). 3
(4). 3
(5). 4

RBSE Class 11 Biology Chapter 39 Very Short Answer Questions

Question 1.
What is PAR?
Answer :
The visible light of solar spectrum is called as photo synthetically active radiation (PAR).

Question 2.
What is Lapse rate.
Answer :
Decrease in temperature with increase in altitude.

Question 3.
Write botanical names of three insectivorous plants.
Answer :
Drosera, Nepenthes, Utricularia.

Question 4.
Write botanical names of four plants having root pneumatophores (spaces)
Answer :
Rizophora, Avicennia, Ceriops, Nypct.

RBSE Solutions for Class 11 Biology Chapter 39 Environmental Factors

Question 5.
What are phreatophytes?
Answer :
Phreatophytes are deep rooted plants that obtain water that it needs from phreatic zone (zone of saturation)

Question 6.
What are malacophyllous? What is the reason of their fleshy nature.
Answer :
The plants which have fleshy leaves due to much water storage tissue.

RBSE Class 11 Biology Chapter 39 Short Answer Questions

Question 1.
Differentiate season & weather.
Answer :
The meaning of climate is the average climatic factors in a place over many years. The prediction of these factors for a specific time and place is called as weather. Hence, the weather exhibits weekly, daily changes whereas climate is of long standing (seasons & years).

Question 2.
Differentiate Heliophytes & Sciophytes.
Answer :
The effect of daily light or day length on the flowering & fruiting of the plants is called as photoperiodism. The term photoperiodism was first used by Garner & Allard (1920). On the basis of daily light required for flowering, the plants are of three types-

  • Long day plants (LDP)
  • Short day plants (SDP)
  • Dav natural plants (DNP)

On the basis of requirement of light, the plants are of two types*

  1. Photophilous or Heliphelous or Heliophytes –
    The plants which need bright light to grow. Examples – Sun flower, Ameranthus, Populus etc.
  2. Sciophilous or Sciophytes –
    The plants which grow in less light or shadow.
    synthesis of anthocyanin pigment in plants. The purple sulphur bacteria use infra red & UV radiations for photosynthesis.

Question 3.
Explain types & formation of humus.
Answer :
Soil Organic Matter : It is also called as humus. It is essential for soil fertility. The decaying organic material of dead organisms is called as humus. It is formed by degradation of remnants of plants and animals, and excreta of animals. Earthworms, microorganisms like bacteria & fungi utilize the humus as food. Formation of humus is called as humification and conversion of humus into mineral salts is called as mineralization. The Humus is of two types :

  • Mor humus : It is raw humus. It has less mineral salts & microorganism or animals are almost absent.
  • Mull humus : It is a granular & mature humus. It harbors microorganisms & earthworm abundantly.

RBSE Solutions for Class 11 Biology Chapter 39 Environmental Factors

Question 4.
Write short notes on
(a) Vernalization (b) Photoperiodism
Answer :
(a) Vernalization – In some plants, flowering depends upon  minimum temperature. The induction of flowering by exposure to prolonged cold of winter or by and artificial treatment of seeds by low temperature is called as vernalization. Presence of Oxygen is essential for it. According to some scientists, Vernalin compound is formed during vernalization that converts into Florigen or gibberllin. It is responsible for beginning of flowering.

(b) Photoperiodism –
The effect of daily light or day length on the flowering & fruiting of the plants is called as photoperiodism. The term photoperiodism was first used by Garner & Allard (1920). On the basis of daily light required for flowering, the plants are of three types-

  • Long day plants (LDP)
  • Short day plants (SDP)
  • Dav natural plants (DNP)

On the basis of requirement of light, the plants are of two types

  1. Photophilous or Heliphelous or Heliophytes –
    The plants which need bright light to grow. Examples – Sun flower, Ameranthus, Populus etc.
  2. Sciophilous or Sciophytes –
    The plants which grow in less light or shadow.
    synthesis of anthocyanin pigment in plants. The purple sulphur bacteria use infra red & UV radiations for photosynthesis.

RBSE Class 11 Biology Chapter 39 Essay Type Questions

Question 1.
Give a brief account of climatic factors which affect the plants.
Answer :
Climatic factors :
The climatic factors include light, temperature, air, water, humidity, gases etc. The study of climatic factors is called as climatology. They play very important role in the growth & distribution of the plants.

Light :
Sunlight is the only natural source of light. The visible spectrum of solar radiations from 390 nM to 760 nM ( nano meter) form the visible light. It is called as PAR (Photo synthetically Active Radiation). The three phases of the light energy affect the organisms-

(A) Wavelength of Light-

The wavelength of the colours of visible spectrum is different. The process of photosynthesis occurs maximum in red light (650 to 760 nM) then in blue light ( 430 to 470 nm) and almost nils in green light (500 to 560 nm). The middle part of the spectrum is absorbed by carotinoids which later on is transferred to the chlorophyll as energy . Accumulation of carbohydrates takes place in the red colour and synthesis of proteins occurs in blue light. Though the UV rays are harmful for plants but they help in the synthesis of anthocyanin pigment in plants. The purple sulphur bacteria use infra red & UV radiations for photosynthesis.

(B) Light intensity –
The intensity of light on the Earth is affected by topography, latitude, altitude, environmental condition & seasons. The intensity & duration of light at any place depend upon latitude & earth rotation. The light intensity is measured with the help of Luxmeter or Photometer and the unit of measurement is Lux. In forests the growth of the ground flora is determined by the light intensity.
RBSE Solutions for Class 11 Biology Chapter 39 Environmental Factors img-1

(C) Duration of Light or Photoperiodism –
The effect of daily light or day length on the flowering & fruiting of the plants is called as photoperiodism. The term photoperiodism was first used by Garner & Allard (1920). On the basis of daily light required for flowering, the plants are of three types-

  1. Long day plants (LDP)
  2. Short day plants (SDP)
  3. Dav natural plants (DNP)

On the basis of requirement of light, the plants are of two types –
(a) Photophilous or Heliphelous or Heliophytes –
The plants which need bright light to grow. Examples – Sun flower, Ameranthus, Populus etc.
(b) Sciophilous or Sciophytes – The plants which grow in less light or shadow.
Example – Picea , Abies, Texas

Effect of light on the plants –
It is reflected in the following farms-

1. Effect on Photosynthesis –
Light is essential for the formation of Chlorophyll. The light plays important role in the light reaction of photosynthesis. On the basis of light energy, ATP is formed by phosphorylation. Photolysis of water forms coenzyme NADPEE+ H which is essential for fixation of CO2 in the dark reaction. In photosynthesis, the formation of ATP & NADPH H is called as assimilatory power.

2. Effect on Transpiration –
The opening & closing of stomata for gaseous exchange is controlled by light. The stomata open during bright light to increase transpiration. The rate of transpiration decides the rate of water absorption & the rate of ascent of sap.

3. Effect on Respiration & Plant growth –
Increase in light intensity increases rate of respiration in many plants. It depends upon the permeability of the cell membrane and viscosity of the protoplasm. The light effects the growth of seedling, germination of seeds, bud blossum, terminal growth of shoot etc. The seedling in lack of sufficient light becomes yellowish (Etiolated) which is called as etiolation. The light is essential for formation of florigen hormone & plant growth hormones.

4. Effect of Light on Plant distribution –
Light is an important factor in local distribution of plants and stratification of vegetation’s. In aquatic ecosystems (Lake. Oceans etc), the light determines distribution of plants. As a result different zones (Such as Littoral, Lacustrine or Limnetic, Profundal) are formed.

5. Effect of Light on Internal structure of Plants –
The light mainly effects the internal structure of the leaves. In the dorsiventral leaves of dicotyledon plants, the variation on both the sides in the columnar tissue and spongy parenchyma of mesophyll tissue is because of uneven distribution of light. In the monocotyledon plants, both the sides of isobilateral leaves mesophyll variation is not found because of even distribution of light and all the cells are isodiametric.

6. Effect of Light on Aquatic system –
In aquatic ecosystem (such as ponds, lakes, oceans etc), the distribution of the plants is regulated by the light. The availability of the light controls the vital activities. In deep aquatic system, the availability & the intensity of the light determine the type & population of producer and consumer organisms. Such as the phytoplanktons found in limnetic zone the benthic animals are found in the bottom.

Similar to the plants, the animals are also affected by the light. Their many structural & behavioural characters are controlled by the light. Both the aquatic & terrestrial animals are affected by the amount, intensity & duration of the light. Such as colour change in calotese, movements in phytoplanktons & Zooplanktons. Gonadal development in lizards & tortoise etc.

RBSE Solutions for Class 11 Biology Chapter 39 Environmental Factors

Question 2.
How the Edaphic factors affect the plants?
Answer :
Soil is a upper most layer of weathered Earth crust in which plants grow. It is a complex composite mass of minerals and degraded organic material. The study of soil is called as pedology. The foundation of pedalogy was laid by Russian scientist Dokuchaw (1889). According to him, soil is the result of interaction among mother rocks, environment, organisms & time. The formation of soil as a result of weathering of rocks is called as pedogenesis. The rock is an aggregation of minerals which degrades constantly which is called as degradation. Three main factors participate in this process viz.-

  1. Physical factors : Such as air. precipitation, temperature, landslide etc.
  2. Chemical factors : Such as hydrolysis, oxidation, catabolism, hydration, carbonization etc.
  3. Biological factors : Moss, blue green algae, mining etc.

Formation of soil is a continuous but a very slow process. On the basis of formation & origin of minerals, the soil is of two types (a) Residual soil : The soil that remains in the place of its origin.
(b) Transported soil : The soil that has been transported from other places by many ways. It is of four types viz.-

  • Alluvial soil : The soil which is transported by water.
  • Glacial soil : Transported by glaciers.
  • Colluvil soil : Transported by Earth’s gravity.
  • Aeolian soil : Transported by air.

Soil Profile :
A soil profile makes up a distinct layer of soil. It runs roughly parallel to the soil surface and has different properties and characteristics than the adjacent layers above & below. The soil profile is a vertical section of the soil that depicts all its horizons. These horizons are as follows :
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1. Horizon ‘A’ :
It is the uppermost layer which is also called as top soil It allow s plants to grow. It is formed by the interaction of rock degradation, activities of the organisms. It is rich in humus. It is dark brown in colour.

2. Horizon ‘B’ :
It is situated below the top soil & also called as subtop soil. It is light brown in colour & denser than top soil. If is life less i.e. without organisms. It contains fine rock particles & soluble minerals. It stores the rain water & acts as water reservoir. This water gradually reach up to the top soil by capillary action.

3. Horizon ‘C’ :
It is the lowermost stratum of the soil profile which is of less important concerning to life. Sometimes long roots of plants are found in it. It is followed by hard rocks.

The top soil is comparatively thicker in the grasslands. The soil devoid of vegitation is without top soil, hence the subtop soil becomes uppermost.

Composition of soil :
Normally, the garden soil consists of four main components-

  1. Mineral components (40% by volume)
  2. Soil organic matter (10% by volume)
  3. Soil water (25% by volume)
  4. Soil air (25% by volume)

They are called as soil factors and they vary qualitatively & quantitatively according to the ecological conditions. In addition, soil temp., soil organisms & soil activities also help in plant growth

1. Mineral Components & Soil texture :
The minerals are the derivatives of the rock. The size of minerals particles is variable and it affects the soil properties.
Chemically, gravel and sand are inert Dead granules are normally made up of oxides of aluminium & silicon. The relative ratio of mineral particles of various sizes determines the soil texture. Pebbles & gravel are not considered in textural classes.

The soil texture decides the water holding, nutrients & growing plants of the soil.
On the basis of relative ratio of rock particles, the soil is of six types –

  • Sandy soil : In includes sand particles. It has sufficient soil air but its water & nutrients holding capacity is less.
  • Clay soil : It mainly includes clay. It’s water holding capacity is high but the aeration is less. It is not suitable for plants to grow.
  • Loam soil : It includes equal quantity of silt & clay. It has moderate aeration & water holding capacity. Hence, it is suitable for plants to grown.
  • Sandy loam soil : It is a loam soil with more soil particles.
  • Silt loam soil : It is a loam soil with more silt granules.
  • Clay loam soil : It is a loam soil with more clay.

2. Soil Organic Matter :
It is also called as humus. It is essential for soil fertility. The decaying organic material of dead organisms is called as humus. It is formed by degradation of remnants of plants and animals, and excreta of animals. Earthworms, microorganisms like bacteria & fungi utilize the humus as food. Formation of humus is called as humification and conversion of humus into mineral salts is called as mineralization. The Humus is of two types :
(a) Mor humus : It is raw humus. It has less mineral salts & microorganism or animals are almost absent.
(b) Mull humus : It is a granular & mature humus. It harbors microorganisms & earthworm abundantly.

3. Soil Water :
The main source of soil water is rain. After heavy rain some of the water flows down which is called as run off water. It is not easily available to the plats. Some water under the influence of gravity reaches unto the water table and it is called as gravitational water. It is also not available easily to the plants. Some part of the rain water occupies the spaces in between the colloidal granules of soil or forms thin layer surrounding the granules. It is called as capillary water. It is easily available to the plants and is of much importance. It is absorbed easily by the roots. Some of the soil water is absorbed by soil colloids which help to bind these particles. It is called as hygroscopic water. It is not available to the plants. Some of the soil water is associated with the mineral molecules. It is called as chemically combined water. It is not absorbed by the roots. To conclude, out of all types of soil water only capillary water is used by the plants.
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Soil water holding or Field Capacity (FC) :
Field capacity is the amount of soil water held in the soil after excess water drained away.

Field Capcity ⇒ Capillary water + Hygroscopic water + Chemically combined water + Water vapor

The total of hygroscopic water and capillary water is called as soil water holding capacity. The mineral point of soil moisture the plant requires not to wilt is called as permanent wilting point (PWP). If moisture decreases to this, a plant wilts and can no longer recover its turgidity. The percent hurnidy of soil at which the plant first develops permanent wilting is called as wilting coefficient.

The part of soil water which can be absorbed by plants is called as available water, normally it is capillary water. The part of soil water which cannot be absorbed by the plants is called as non-available water. In other words, the total amount of soil water is called as holard. the part of water that can be absorbed is called as chresard and the part which cannot be absorbed is called as Echard.

Proper growth of plants require a sufficient amount of water. Excess of soil water i.e. water logging reduces the air spaces and roots get damaged. The water absorption is affected and the plant growth is highly reduced. This type of land is called as physiologically dry land.

4. Soil air :
The soil is porous and there are air spaces in between the soil particles which are occupied by either water or air. The amount of soil air depends upon the size of these pores. The soil oxygen is essential for germination of seeds,’ root growth, soil fertility, humus formation, development of root hair, nitrogen fixation by bacteria, absorption by roots etc. Diminished aeration causes morphological & anatomical modifications such as presence of pneumatophores in mangroove plants. The hydrophytes have a developed system spaces that helps to provide O2 to the submerged roots.

Question 3.
Write an essay on positive & negative interactions among organisms.
Answer :
Biotic Factors :
The vital activities (such as growth, nutrition, reproduction, pollination etc) of the organisms and the effect of their interactions are termed as biotic factors. Odum (1971) divided the biotic relations into two groups viz.-

Positive Interactions :
In these interactions one or more species are benefited. Such as mutualism, protocooperation, commensalism.

(1) Symbiosis :
A permanent relationship between two different species (dissimilar organism) in which both are benefited. It may also be called as obligatory mutualism.

Examples : Lichens. Rhizobium, Mycorrhiza etc. Mycorrhizal assocation occurs between the roots of higher plants & fungus.
Examples : Pinus. Oak. Hickories. Birch etc. The fungus absorbs the water & minerals to provide to the plants and in tum obtain other nutrients from the roots. Absorption of phosphorus from the soil is perform by the fungus. Such roots are without root hairs.

(2) Protocooperation :
It is a temporary relationship between two different species (dissimilar organisms) in which both are benefited. It is also called as non- obligatory mutualism.

Examples : Sea anemone & Hermit crab. The hermit craps lives in an empty gastropod shell to which sea anemone/s remain attached. They may live independently also.

(3) Commensalism :
The relationship between two different species (dissimilar organisms) in which one is benefited & second remains unaffected (Neither loss nor benefit).

Examples : (i) Epiphytes & Epizoans – The epiphytes are autotrophs which grow on other plants for support. They have hanging roots bearing velamen which absorb atmosheric humidity. They synthesize their own food by photosynthesis. Such as Vanda & Orchids. Green algae Basicladia grow on the shell (back) of fresh water turtles. It can be an examples of epizoan.
RBSE Solutions for Class 11 Biology Chapter 39 Environmental Factors img-4
Example : (ii) Lianas – They are long – stemmed woody vines, that are rooted in the soil at ground level and use trees to climb up to the canopy to get access to well-lit areas of the forest. Examples – Tinospora, Bignoia, Bouganvilliaetc.

Negative Interactions :
The relationship between two dissimilar organisms in which one or both remain in loss. It is also called as antagonism. They are of three types –
1. Exploitation,
2. Antibiosis &
3. Competition

1. Exploitation :
In this relationship one species directly or indirectly hanns other species to get support, shelter or food and mainly for food. The exploitation for food is of two types :

  • Parasitism: A relationship between two dissimilar organisms in which one is benefited (Parasite) and second remains in loss (host)
    Examples : Leach, Dodder (Amarbel), Striga, Purple toothwort, Cuscuta, Aureolaria (Orobanchaceae)
  • Predation : Some animals feed on other organisms which may be herbivorers or carnivores and are called as predators. The plant eater predators are called as herbivores such as some fungi (Dactyella, Zoophagus), Insects, Nematods etc. Some plants feed on insects and are called as insectivorous plants. Such as Drosera, Nephenthes, Utricularia, Dionea etc. They have various organs to feed insects.

2. Antibiosis :
In this relationship, one organism secretes some chemicals which partially or completely inhibit the growth of other organism and lead to death. The roots of some higher plants secrete toxic chemicals which inhibit the germination of seeds of plants of other species. It is called as allelopathy. Examples – Allelopathy parthenium, Lantana, Eucleptus etc. Antibiosis is applicable on microorganisms such as fungi, bacteria, actinomycetes etc.

3. Competition :
Similar environmental needs develop competition among organisms. This competition is mainly for shelter, food, light, water etc. The competition among the organisms of same species is called as intraspecific competition and among the organisms of different species is termed as interspecific competition.

S.No. Type of Relationship Species A Species B Effect of Relationship
1. Symbiosis + + Both in benefit, obligatory
2. Protocooperation + + Both in benefit, Non- obligatory
3. Commensalism + 0 One is benefited & second is unaffected
4. Antibiosis 0 One is in loss & second is unaffected
5. Parasitism + One is in benefit & second in loss
6. Predation + One is benefit & second is in loss
7. Competition Harmful to each other

RBSE Solutions for Class 11 Biology