· Ecology ('Oikos means Homes and 'logos' means understanding or study) is the study of the interrelationship between living organisms and non-living environments.
· Ecosystem: largest ecological units.
· Term ecology was coined and described by E. Haeckel in 1869 but its first authentic use was made by Reiter (1835)
· Ecosystem coined by A.G. Tansley (1935)
· Father of Ecology is Reiter.
· Father of Ecosystem is E. P. Odum.
· Warming employed term ecology for the study of plants.

(VVI Ques) Ecology term was coined by: (BPKIHS)
a) Linnaeus        
b) Haeckel
c) Harvey            
d) Odum
Ans: b

a) Aristotle 
b) Reiter
c) Linnaeus
d) odum
Ans: b

a) Haeckel 
b) Reiter
c) Odum 
d) Linnaeus
Ans: a

Various Branches of Ecology

· Autoecology: Study of ecological relationships regarding a single species.
· Synecology: Study of species living together making a community.
· Synecology deals with the study of the relationship between communities and the environment.
· Bioecology: The integrated study of plant ecology and animal ecology.
· Genecology: Study of ecological adaptations in relation to Genetic Variability.
· Paleoecology: Study of the relationship between organism and environment in past.

Terminology Related to Ecology
· Speciation (cladogenesis): is the phenomenon of the development of one or more new species from an existing one due to reproduction isolation.
· Interbreeding is possible among similar species.
Types of Speciation:
1. Allopatric speciation

· Formulation of a new species from a spatial isolated population.
· All operatic species are the same or related species having separated and mutually exclusive areas of geographical distribution.
· It's a slow process and takes a long time.
2. Sympatric speciation
· Formation of new species from a segment of the population due to the sudden appearance of reproductive isolation.
· It's abrupt and is caused by mutation.
· Two or more species having the same or overlapping areas of geographical isolation are called sympatric species.
· Darwins' finches of Galapagos island are examples of adaptive radiation (adaptation of various ecotypes of a species in a different environment).
· Ecosystem is the interaction between biotic and abiotic components of an environment
· Term ecosystem was coined by A.G. Tansley.
· Ecotype: Individuals who have developed various morphological characters for local adaptation. Individuals are genetically dissimilar but morphologically or ecologically similar. They are genetically fixed.
· Ecads or Ecophene: Individuals of the same species having various morphological character, genetically not fixed (i.e variations are environmentally based, not genetically).
· Ecesis or Ecosis: Establishment of a plant in a new area during secondary succession.
· Ecotone: The transition zone between two communities is called ecotone or tension zone. It has a greater number of species and density.
· It has a mosaic of individuals of adjoining communities.
· The transition zone between fresh water and saline water (sea) is called Estuary which has hypersaline water.
· Ecological Niche: Word given by Grinnel; Habitat and function of every organism in the ecosystem:
· It includes habitat, tolerance, food type, reproductive vigour, adaptional features, competition and its role as producer-consumer, scavenger or decomposer, etc.
· No two organisms can occupy the same ecological niche for a long time; if two species try to occupy the same ecological niche, then competition occurs which eliminates fewer vigour species.
· Sibling: A morphologically similar member of a species. They do not cross-fertilize.

Ecological Laws:
1. Allen’s law: The extremities of mammals like tail, snout, ears and legs are relatively shorter in colder parts than warmer parts.

2. Rensch’s law/Rule: The races of birds with relatively narrow and more acuminate (elongated or sharp) tend to occur in the colder regions while those in warmer climates tend to be broader.

3. Jordan’s rule: Fishes inhabiting water of low temperature tend to have more vertebrates than those of warmer water.

4. Bergman’s rule: Mammals living in cold climates tend to be larger than similar species inhabiting colder climates.

5. Gloger rule: Based on pigmentation. In warm and humid climates many animals like insects, birds and mammals bear darker pigmentation than the races of some species in the cold and dry climates.

Ecological Parameters:

1) Population: A group of individuals of the same species living at one place (specific geographical area) constitute the population.

2) Organism: Basic (smallest) unit of ecology, has the ability to grow, regenerate, self regulate, self perpetuate and reproduce.
- Demography: study of population.
- Population: increases by birth, immigration
- Population: decreases by death, emigration.

3) Migration: Two-way temporary movement of the organism; do not affect population size.

4) Key-stone species: Species that influence the ecosystem and determine its property. eg; Kangaroo of Tiaga ecosystem and Reptiles of the desert ecosystem.

5) Phytotron: Device in which plants are grown under controlled environment.

6) Genetic drift: It is the sudden cause of loss or evolution of new species due to drastic changes in genetic characters in a small population. It is caused by environmental factors like natural calamities, volcanic eruptions, drastic changes in ecological nature etc.

7) Carrying capacity: Total number of individual species in an ecosystem which can be fitted by the locality for an optimum healthy life is called carrying capacity. If the addition of a new one occurs beyond the carrying capacity, the population decreases.

8) Biotic potential: The inherent capability of an organism to produce a new one in an ideal condition/optimum condition is known as biotic potential. It is always more than the realized potential which is determined by the given condition of the ecosystem.

9) Noosphere: sphere dominated by human mind eg; greenhouse, culture media etc.

10) Biosphere: It refers to the area occupied by plants and animals. It is a hospitable (inhabitable) area on the earth’s atmosphere; Lithodpher and hydrosphere.

11) Cultigens: Cultivated plants like tomato, maize that would be without human help.

Factors determining the distribution of organisms, Various Ecological factors
There are four ecological factors:
1. Climatic factors
a. Light

· Solar energy of light is the main source of energy in an ecosystem.
· Light is important for photosynthesis, photorespiration, transpiration(Stomatal opening and closing), seed germination and plant movement, pigmentation.
· Light plays a significant role in mutation and anthocyanin formation in plants
· Sun-loving plants are Heliophytes.
· Sciophytes are shade-loving plants
· In plants stem is positively and the roots are negatively phototropic.
Plant movement:
    · Photonasty: flower open or close in response to light.
    · Nyctionasty: folioing of leaves in response to darkness.

b. Temperature
· It's important for photosynthesis transpiration seed germination flowering, breakdown of seed dormancy and seed dispersal.
· Temperature and rainfall determine the types and distribution of plant communities.
· Note:
1. Homisthermic (Endothermal) or warm-blooded animals: Animals that are capable of maintaining their body temperature irrespective of the surrounding temperature. eg. Birds and Man.
2. Poikilothermic (ectothermic) or cold-blooded animals: Animals whose body temperature fluctuates according to the surrounding temperature. eg. fishes, amphibians, reptiles etc.

c. Rainfall (Precipitation)
· Main factor to determine the plant communities.
· Rainfall is the main source of water for land plants.
· Total water present in the soil is Hollard.
· Water available to the plant is Chresard.
· Water hardly available or non-available to the plant is Echard.
· Water easily available to the plant is capillary water which is present between the soil particles.
· Water hardly available to the plants is gravitational water. It is the water that drains down through the soil. The level to which it drains is called the water table. It is of extreme importance as it causes the washing out of minerals and nutrients from the soil called leeching.
· Water not available to the plants is Hygroscopic water. It is present on the surface of soil particles.
· Diversity or variation is high in tropical rainforests.

d. Wind:
· It affects the rate of transpiration.
· Wind speed is measured by an anemometer.
· Low wind: few stomata open
· Moderate wind: maximum stomata open.
· High wind: stomata close.
· Negative effect of wind-breaks twig, flowers, fruits.
· Positive effect-pollination, seed dispersal.

e. Humidity:
· It is the amount of water vapour present in the atmosphere. 
· It affects the rate of transpiration.
· Transpiration is low in high atmospheric humidity and vice versa.
· Submerged hydrophytes-not affected by humidity since they have no stomata.
· Relative humidity is measured by a psychrometer.
· Guttation: occurs at high humidity and high root pressure.
· No guttation occurs in submerged hydrophytes.
· Colocasia antiquorum is known to guttate heavily.

2. Edaphic factory (Soil)
· The physical and chemical properties of soil are related to edaphic factors.
· Soil: It is the uppermost withered layer of rock mixed with organic colloids (humus).
· Soil provides water, nutrients and anchorage to plants.
· Best pH for mineral absorption is 6 to 7 (neutral or slightly acidic).
· Dark colour of soil is due to high humus content (i.e organic matter).
· Light colour of soil is due to high iron oxide (laterite).
· Pedogenesis: development/maturation/formation of soil.
· Edaphology or Pedology: the study of soil.
· Soil texture: As a result of weathering soil particles of different sizes are formed. They are described below:
  1. Clay → < 0.002 mm
  2. Slit → 0.002 - 0.02 mm
  3. Fine sand → 0.02 - 0.2 mm
  4. Coarse sand → 0.2 - 2 mm
  5. Gravel or Grit → 2 mm - 5 mm
  6. Coarse Gravel → > 5.00 mm
Note: Clay soil is the least porous one.

Soil composition:
· Mineral matter soil organism
· Organic matter
· Soil air
· Soil water
· Soil is a mixture of different sized particles.
· Size of soil particle in decreasing order: Sand > Silt > Clay
· Best soil for plant growth is loam soil (50% sand + 50% silt and Clay)
· Best soil for rooting is sandy soil 20% clay + 40% sand + 40% slit.
· Water holding capacity is high for Clay soil and low for sandy soil but the best soil for cultivation is Loam soil.
· O2, CO2, N2 soil air- the space between the soil particle is filled with air known as soil air that helps in aeration for plants
· Plants shows better growth in aerated soil than water lodged soil.
· Physical dry soil is sandy soil.
· Soil is called physiologically dry in Halophytic condition (i.e. high concentration of salt and other salts like nutrients), in physiologically dry soil water is present in abundance.
· Weathering – it's a method of pedogenesis (soil formation) in which larger rocks break into a smaller and finer mineral particle which ultimately changes into the soil.
· The upper layer of soil is composed of humus which is the partially decomposed organic matter added by living organisms.
· The process of formation of humus from the bodies of organisms by changing into organic materials is called humification.

· Special Note:
· Hollard is total water in the soil.
· Chesard is the Available water (water absorbed by plant root from the soil)
· Echard is the Non-available water (amount of water that is not absorbed by the plant from the soil).

Various Types of Soil water:
1. Capillary water: Water present in the capillary space of soil due to surface tension. This is water readily available to plants.

2. Gravitational water:
The water that moves downward due to gravity, it is hardly available to plants. It forms groundwater.
Note: But for psammophytes, this water is available.

3. Hygroscopic water: A thin layer of water attached tightly to surfaces of soil particles due to forces of cohesion or adhesion.
Note: It can’t be used by plants.

4. Water vapour
: vapour in capillary space.
Note: Velamen in terrestrial roots can absorb water vapour from the air, eg; sobralia, phajas etc.

5. Combined water: water present in hydrated oxides of minerals (Al, Fe, Si, etc) in soil.
· Note: Sandy soil due to bigger pores can’t hold water. So they are physically dry soils.
· If water is present in the soil in abundance but not available to the plants due to a high degree of salinity, such soils are referred to as physiologically dry soil.

6. Field capacity or water holding capacity: It is the amount of water retained by the soil after the removable gravitational water.
· i.e, Field capacity = Holard - Gravitational water.

7. Storage capacity:
This is the extent to which the soil can hold capillary water against gravity.

Soil Adaptation:
1) Lithophytes: Plants growing on rocks.
2) Psammophytes: Plants growing on sandy soils.
3) Oxylophytes: Plants growing on humus or acidic soil.
4) Halophytes: Plants growing on saline or alkaline soils.
5) Psychrophytes/Cryophytes: Plants growing on cold soil.
6) Eremophytes/Xerophytes: Plant growing on dry soil/desert.
7) Chasmophytes: Plants growing in crevices of rocks.
8) Chersophytes: grow in the wasteland.

Soil Erosion
· Loss of topmost layer of soil known as soil erosion [MOE]
Ways for soil conservation:
    1. Controlled grazing
    2. Afforestation
    3. Terracing
    4. Crop rotation: the process of keeping the mineral content of soil constant.

· Formation of soil: Soil formation takes place in two ways:
a) Weathering: The breakdown of bigger rock into fine, smaller mineral particles is called weathering.
b) Pedogenesis (soil formation)
· Soil profile: Soil lies on the earth in the form of different layers known as the soil profile.
· Soil profile is normally distinguished into three distinct zones called as the horizon (A, B and C).
a) Horizon A:
- It is referred to as topsoil. It contains humus and minerals hence its colour is variable according to its contents.
- The roots of the small plants grow in topsoil only.
b) Horizone B:
- It Is known as sub-soil. It contains minerals, sand and clay.
- Due to poor aeration root doesn’t develop.
c) Horizone C:
- It contains weathered rock and for no use of plants.

Types of soil on the basis of mode of their formation
a) Residual soil: The soil in which soil formation i.e, weathering and pedogenesis, occur at the same time.
b) Transported soil: weathering and pedogenesis occurs at a different place.
- Colluvial soil: soil carried by gravity @CG
- Alluvial soil: Soil carried by water, it is highly fertile.
- Glacial soil: Soil brought by ice.
- Eolian soil: Soil brought by wind (air)

3. Topographic Factors:
It includes:
    i) Altitude of mountain
    ii) Steepness of slope.
    iii) Direction of mountains etc.
· As we move from low to high altitude, water scarcity ↑.temperature↓ and organic matter becomes less available.
· Species richness ↑ as we move from high to low latitude and altitude.
· Mountain chains lying on the path of monsoon clouds receive more precipitation, hence rich in species diversity.

4. Biotic factors.
· Living or Biological factors.
A. Intraspecific relationship: Among the individuals of the same species. This includes:
a) Competition – Intraspecific competition between two individuals of the same species due to similar basic and daily needs.

b) Parasitism – one species parasitise on the organisms of the same species.

c) Predation (cannibalism)
  a member of species kills another member of the same species:

B. Interspecific Relationship: Among the individual of different species.
a. Symbiosis – an association of two species of an organism where both the partners derive benefit from each other is called symbiosis.
Eg. Nitrogen-fixing bacteria (Rhizobium) in root nodules of legumes.
Algae and fungi live together in lichen.
Water fern (Azolla) and the nitrogen-fixing cyanobacteria (Anabaena)

b. Commensalisms – Relationship between two organisms in which one species is benefitted but another is neither benefited nor harmed. 
Eg. Epiphytes and lianas, Association of sea anemones and Hermit crab.

c. Parasitism – It is the association of two types of organisms in which one gets benefitted while the other is harmed.
· It's the association in which the weaker organism feeds on the stronger organism.
· The parasite is an organism that lives one another organism (the host from where it obtains food as well as shelter. 
Eg. The Dodder (Cuscuta sp), Rafflesia is a parasite plant.
  • Rafflesia – Total root parasite.
  • Cuscuta – Total stem parasite.
Endoparasites – Ascaris, Taenia, Fasciola, plasmodium
Ectoparasite – Tick, leech, lice, aphids, cab mites, suck the juice of plants.

d. Predation- This is the relationship in which one organism kills another for the of feeding. In this relationship, a predator always kills its prey. Predator is always large and stronger than prey.
For eg., Tiger kills deer for feeding. In this relationship, Tiger is a predator and the deer is prey.

e. Mutualism - It's the relationship between two or more individuals of different species in which all are benefitted from one another it's similar to symbiosis.

f. Scavaging - It's also a direct food relationship between two organisms in which one feed on the other which have already died naturally or have been already killed by another animal.

g. Amensalism- It's the association between two species in which one is neither benefited nor harmed while another is harmed. 
Eg. Penicillium notatum and bacteria (Penicillium produces and antibiotic penicillin which inihibits the growth of bacteria)

h. Myrmecophily – It's the association of certain ants with some plants like mango and litchi. Ants protect the tree from other animals and get shelter and food from trees.

i. Camouflaging - The blending of an animal with its surrounding is called camouflage. Its' also known as protective colouration. 
Eg. Trees and other plants harbour, protect and hide animal-like insects reptiles and birds by camouflaging, their body shape and colour to the surrounding.

j. Mimicry - It's a type of protective resemblance in which an animal mimics another animal so as to avoid predation 
Eg. a butterfly mimics the stem of plant-insect mimics dead leaves to avoid being eaten by birds.

k. Saproptrohic Nutrition - organisms obtain their food from dead organic matter. They either absorb in the form of a solution or ingest very small pieces eg. Fungi.

l. Scavengers - These animals feed on dead organic matter by ingesting large pieces of it.
Autotrophs - They can prepare their food themselves. eg. green plants.
Photoautotrophs - Utilize light energy to prepare their food.
Chemoautotrophs - Obtain energy from the chemical reaction or chemical oxidation of nutrients.
Heterotrophs - Depends on their organisms for food.


· It is the interaction between biotic and abiotic components of an environment
· Ecosystem is the structural and functional unit of ecology.
· Term ecosystem was coined by A.G. Tansley.
· The structure of an ecosystem is related to species diversity.
· The ultimate source of energy for the ecosystem is solar energy.

Components of the Ecosystem:
1) Biotic component
· It deals in the kind, number and distribution of organisms. It includes all living organisms which are categorised into 3 different groups.
    a) Producer
    b) Consumer
    c) Decomposer

a) Producers (Transducers or converters):
· These are the autotrophic organisms that synthesise food by using light energy.
· They produce carbohydrates, (by photosynthesis), proteins, fats,
· Producers include green plants, algae, protists and phototrophic bacteria.
b) Consumers
· They are heterotrophic organisms that obtain energy from producers directly or indirectly. (Phagotrops)
3 Types
1. Primary consumers
· They feeds directly on green plants. eg. Herbivore like deer cattle, insects, birds.
2. Secondary consumers
· They are the organisms feeding on the primary consumers. Eg. snake, frog, jackal, fox, etc.
3. Tertiary consumers
·  They feed on secondary consumers. Eg. Carnivorous like lion, tiger etc.
c) Decomposers
· These are dead or decayed plants or animal feeders which include bacteria and fungi.
· They change the complex organic compound into a simple organic compound which is later absorbed by the producers.
· Energy ecosystem involves the cycling of material and flow of energy
· Energy flow in the ecosystem is always unidirectional.

2) Abiotic components
· It includes chemical factors like light, temperature, water, oxygen, organic compounds (Proteins, amino acids, lipids and Carbohydrates)

Food Chain

· Food chain is the transfer of food energy from the source (producers) through the series of organisms in the ecosystem by the process of eating and being eaten.
· It is the study of the relationship between food and energy in linear form.
  • Green plants → Butterfly → Spider → Bird.
  • Producers  Primary consumers  Secondary consumer  Tertiary consumers

Various Types of Food Chain:
1. Grazing or predator food chain:
· The base of this food chain consists of producer level including herbivores and carnivorous.
· This type of food chain depends on the solar energy which is circulated through the food chain.
· Green plants → Rabbit → Wolf → Lion

2. Detritus or saprophytic food chain:
· It starts from dead organic matter and is then directed towards microorganisms and other detritus feeders.
· Parasitic food chain – It goes from larger to smaller organisms.

· A group of interconnected food chains is called a food web. It provides more feeding opportunities to the organisms As there is an alternative feeding opportunity to the organisms food web to make the ecosystem stable.

Trophic level:

· Every organism need the energy to survive grow and reproduce so that they consume their prey 
· Eg. carnivores consume herbivores, thus organisms are found in different feeding groups or levels of feeding which is called trophic levels.
· Step in the food chain represents a trophic level.
· The energy flows only one way through various trophic levels.
· The total dry weight of organisms at a particular trophic level is called biomass.

Fig: Trophic Level

Ecological pyramid:
· They represent the relationship between different organisms or groups in an ecosystem.
· It is the graphic representation of various successive trophic levels in decreasing or increasing order.
· When energy transfers from one level to another level in a food chain, there is a loss of energy in each step.
· The concept of the ecological pyramid was proposed by Charles Elton.

Pyramid of Number
· It represents the number of organisms at each successive level.
· It is erect for the forest, grassland and pond ecosystem but it is inverted for tree ecosystem, so-called Eltonian pyramid.

Pyramid of Energy:
· Represent the number of calories transferred from one trophic level to the next.
· Pyramid of energy is always erect.

Pyramid of Biomass:
· Represents the total biomass (dry weight of organisms at each trophic level at a particular time.
· It is erect for forest and grassland ecosystem but inverted for pond system.

· Community is a nature assemblage or aggregation of living organisms having mutual relationships among themselves and to the environment (physical habitat).
· Ecological Niche of an organism includes the function of an organism (feeding activities, interactions, movement) in a community along with the physical space it occupies. It means the place of organisms in the biotic environment to its relation to food enemies, habits and the abiotic factors.
· Natality – Refers to birth rate, which means the production of new species
· Mortality – Death rate.

Different kinds of Ecological Pyramids in a Single Table

Ecological succession:

· It is the series of changes in a community structure and species composition in due course of time. it is the process in which one community is replaced by another type of community.
· It is a gradual and continuous process that doesn't stop unless a stable community is formed. This final stable community is called climax community (@ while the first community to inhabit is called pioneer community).
· Seral stages: Intermediate communities succession (between pioneer and climax).
· The first plant to appear in an area are called pioneer plants.
· In hydrosere, pioneers are submerged hydrophytes.
· In lithosere, the pioneers are crustose (saxicolous) lichen.
· Overgrazing is the most important causative factor for desertification.
· The different intermediate stages of plant succession are called seral stages and a complete range of plant succession is called sere.
· Serule: Development of plant community in a small area. eg; wall. fallen log.

Types of Succession:
i. Primary succession.
· Succession starting on bare lands or uncolonised land or newly formed water bodies that had no vegetation before is called primary succession.
· Lichens (pioneer organisms) are responsible for primary succession
· Trees form the climax community (final and stable community) in primary succession.
ii. Secondary succession
· It's the type of succession which takes place in the areas which have been occupied by some kind of community before.
· Grasses, Shrubs and weeds are the first organisms to appear in secondary succession.
· Biome – a large geographical area characterized by specific plant communities.
  • Hydrosere – succession starting in the water body
  • Lithosere – succession on the rock surface
  • Halosere – Succession in saline habitats
  • Xerosere – Succession starting in dry habitat (desert)
  • Psammosere – succession in sandy habitat


On the basis of the plant-water relationship, plants are classified into 4 major groups:
    1. Hydrophytes
    2. Xerophytes
    3. Halophytes
    4. Mesophytes

1. Hydrophytes (hydra = water, phyton = plants)
· These are found where abundant water is available
a. Roots:

· Roots poorly developed or absent e.g. Wolffia Root caps replaced root pockets.
· Root hairs absent e.g. Pistia, Eichornia
b. Stem:
· Reduced in free-floating plants. e.g. Pistia
· Narrow and slender in submerged plants. e.g. Hydrilla
· Well developed in amphibian plants. e.g. Nymphaea
c. Leaves:
· Long ribbon-like. e.g. Potamogeton
· Finely divided e.g. Ranunculus
· Thin membranous e.g. Hydrilla
Anatomical Adaptation:
· Cuticle absent over epidermis in submerged part.
· Stomata absent or functionless in the epidermis of submerged part but in plants with floating leaves, present only on the upper surface.
· Well developed aerenchyma present.
· Mechanical tissue like collenchyma/sclerenchyma is poorly developed or absent.
· Poorly developed vascular tissue.
· Secondary growth absent.
· Covered with mucilage – protects from epiphytes, pathogens and animals.
E.g. Wolffia (smallest flowering plant), Lemna, duckweed, Azolla Utricularia (bladder worst insectivorous) Vallisneria.
Types of Hydrophytes
    A. Free floating = Wolffia, Lemma, Pistia, Eichhornia, Azolla.
    B. Submerged = Utricularia, Hydrilla, Vallisneria, Potamogeton.

2. Xerophytes
· Plants that are adopted for dry habitats are called Xerophytes.

a. Roots:
· Extensively developed to increase water absorption
E.g. Alfalfa
· Superficial roots store water in succulents
e.g. Ceiba [Phylloclade: stem of indefinite growth]
b. Stem:
· Usually stunted (dwarf), woody, hard modified into flat phylloclade/cladodes (opuntia, asparagus) may be thorny succulent (opuntia) or waxy/hairy (Calotropis)
c. Leaves:
· Thick and leathery e.g Calotropis or reduced to spine (opuntia) or scales (Asparagus) or needles (pinus) may also store water e.g Aloe vera
Anatomical Adaptation:
· Epidermal cells are thick-walled, multiple epidermises may be present,
· Thick cuticle.
· Sclerenchymatous hypodermis, sunken stomata and presence of hairs.
· Water storing parenchyma well developed.
· Mechanical and vascular, tissues well developed.
· Multiple layered palisades in leaves.
· Therefore high osmotic potential, reduction of transpiration, resistance to desiccation and mucilage to hold water. 
E.g. Opuntia, Casurina Aloe vera, Begonia Calotropis, Asparagus, Rusus etc.

3. Mesophytes
· Intermediate between Xerophytes and Hydrophytes.
a. Roots:

· Luxuriant growth in the root system
· Abundant root hairs
· Root nodules and mycorrhizae are found in many plants.
b. Stem
· Slender (herbs), strong and dwarf (shrubs) or woody (trees)
· Spine, thorn hairs etc are usually absent.
c. Leaves
· Leaves show Maximum development usually broad and deep green.
Anatomical adaptations:
· Epidermis and cuticle are thin, stomata occur on both surfaces and are seldom sunken
· Chlorophyll is abundant and both palisade and spongy parenchyma are well developed.
· Mechanical and vascular tissues are highly elaborated. Therefore, they grow on moist habitats, found in evergreen tropical forests and on banks of rivers, irrigated fields and gardens.

4. Hallophytes:
· May halophytes actually secrete salt via salt or chalk glands.
· This group comprises plants that grow in saline soils (with a high concentration of salts).
· They may be found growing in marine water, soil, rocks or sand.
· Halophytes found in swamps form special vegetation called Mangrove vegetation.
· They produce stilt roots or Pheumatopores (respiratory organs) and are viviparous. e.g. Rhizophoral and Sonneratia.
· Anatomical adaptation of halophytes.
· They have both areal and subterranean roots.
· The cells are large with small intercellular spaces.
· Water storage tissue is well developed in them.
· Stomata are less in number, sunken and on the inner surface of leaves.
· Aerial parts are covered by thick cuticles and trichomes.
· The mechanical tissues are well developed
· The leaves may be dorsiventral or isobilateral.
· They have tannin, oil and mucilage cells.
· The stilt roots show normal anatomy
· Lenticels are present on Pheumotophores
· Their cortex in pneumatophores is spongy and aerenchymatous.
· Morphological adaptations:
· Stilt roots, root buttresses and pneumatophores are present in them.
· The leaves and stems are succulent in nature.
· The seeds are small, light and plants show viviparity. (seed germination while attached to plants).
Physiological Adaptations:
· They show a high rate of transpiration and osmotic pressures
· Their exudation of sap contains dissolved salts of the plants show selective absorption.

Biogeochemical Cycle
· The cyclic transfer of minerals from the atmosphere or soil to the atmosphere or soil through a living organism is called a biogeochemical cycle.
· Hence, the flow of minerals is cyclic, bidirectional and closed.
· There are three types of a biogeochemical cycle:
i) Gaseous cycle: O2, CO2, N2
- Operates through the atmosphere (Perfect cycle)
ii) Sedimentary cycle: S, P, Mg cycle.
- Operates through soil (Imperfect cycle)
iii) Hydrologic cycle: the water cycle.
- Energy from sunlight

A. Nitrogen cycle:
· The cyclic transfer of nitrogenous compounds from the atmosphere back to the atmosphere with the involvement of living organisms is called the nitrogen cycle.
It occurs in the following steps:
a) Nitrogen fixation:

· Conversion of atmospheric nitrogen into soil nitrogen with physical or biological activities.
- Thunderstorms, lightning, storms, volcanic eruption.
- Biological nitrogen fixation occurs by biofertilizers i.e, Bacteria, Fungi, BGA.
b) Nitrification:
· Conversion of a nitrogenous compound into usable forms.
· It has two steps:
· Ammonia → Nitrites → Nitrates
· The first part of Conversion is carried out by Nitrosomonas and Nitrosoccocus the second part of Conversion are carried out by Nitrocystic and Nitrobacter.
c) Nitrogen Assimilation:
· This is the process of utilization of nitrogenous compounds by the organisms.
· Nitrogen is an important element for the cellular pool.
d) Ammonification:
· Conversion of complex nitrogenous compounds into simplest ammonium complex by microbial activities after the death of the organism.
· Common microscopic Bacillus group are well-known ammonifying bacteria.
e) Denitrification:
· Process of releasing free atmospheric nitrogenous compounds from soil nitrogen.
· The denitrifying bacteria are Pseudomonas, Thiobacillus, Nitrosomonas denitrificans.
f) Sedimentation:
· Process of conversion of remaining nitrogenous compounds into soil particles is called sedimentation.
· It is a physical process of fossilization.

B. Carbon Cycle:

· Cyclic transfer of carbonic compounds from the atmosphere back to the atmosphere with the involvement of living organisms is the carbon cycle.
It has 4 steps:
a) Carbonylation or CO2 fixation:
· Requires abiotic factors (CO2, H2O, light, chlorophyll) and autotrophic biotic factors.
· During the carboxylation, autotrophs utilize the atmospheric CO2 and convert it to 1st stable carbonic compound ‘3PGA’ which is utilized for the formation of the glucose molecules.
b) Carbon assimilation:
· Carbon molecules are utilized by all types of living organisms for metabolic activities.
c) Decarboxylation:
· Process of releasing free atmospheric carbon molecules by living organisms through oxidation of organic compounds, aerobic respiration and anaerobic respiration.
· Due to the high rate of decarboxylation of sedimented and non-sedimented organic compounds global concentration of CO2 is increased by more than 50% per year.
d) Sedimentation:
· The physical process of fossilisation or impregmentation of remaining carbonic compounds or biomass into soil particles is called sedimentation.
· The sedimented carbon compounds are called fossil fuels and may also become sources for fossil fuels.

Various Forest Types Found in Nepal:

1. Tropical Zone: (Up to 1000m)
· Forest: Sal forest (Shorea robusta), Tropical evergreen forest and Tropical deciduous riverine forest
· Vegetation:
- Shorea robusta and Dalbergia sissoo are used as timber yielding plants.
- Sisham is the wood is obtained from Dalbergia sissoo
- Terminalia bellarica (Barro), T. chebula (Harro), Butea monosperma (forest fire or flame of the forest).
- The flame of the forest refers to A forest full of trees that burst with red flowers during autumn.
- The highest diversity of living organisms is seen in Tropical rainforests but the least in the Tundra ecosystems.

2. Sub-tropical Zone: (1000-2000m)
· Forest: Schima-castanospsis forest, Alnus nepalensis forest (Utis), Pinus roxburgii forest.
· Vegetation: Schima wallichi (chilaune), Castanopsis indica (katush), Alnus nepalensis (Utis), Pinus roxburgi (Pine/sala).

3. Temperate Zone: (2000-3000m)

· Forest: Lower temperate mixed broad-leaved forest, Temperate mixed evergreen forest, upper temperate/mixed broad-leaved forest.
· Vegetation: Quercus semacarpifolia (Oak), Cedrus deodara (Devdar), Betula utilis (Bhojpatra), Rhododendron arborium (Gurans).

4. Sub-alpine Zone: (3000-4000m):
· Forest: Birch-Rhododendron forest and silver fir forest.
· Vegetation: Betula utilis (Birch/Bhojpatra), Rhododendron barbatum, Rhododendron companulatum, Abies spectabilis (silverfish) Juniperus recurva (Juniper/Dhubi), Picea (spruce).

5. Alpine Zone: Above 4000m
· No forest, major vegetation: small plants like lichen, moss, etc.
· Timberline: Zone in altitude and latitude above which trees can’t grow.
Few terms:

· Phenerophytes: Perennial herbs, shrubs and trees.
· Therophytes: Annual plants that perennate as seeds.
· Trophophytes: Plants that behave as hydrophilous in the rainy season and xerophytes in the dry season.
· Crinohalophytes: Salt secreting halophytes.
· Helophytes: Amphibious plant.
· Psilophytes: Plants growing on savannah biome.
· Euryhaline: Plant that can tolerate a wide range of salinity.
· Brackish water: Slightly saline.
· Phreatophytes: Plant which depends completely on groundwater.
· Calciphytes: Plants growing on calcium-rich soil. eg; Euphorbia.
· Phanerophytes: Trees, shrubs, and climbers with buds exposed on upright shoots.
· Kairmones: metabolic by-product detected by other animals. Eg nematodes in soil → stimulate the growth of fungus.
· Pheromones (Bio-insecticides): Ants release the chemicals containing pheromones for other members to detect colonies.
· Scavenging: Association I which one partner called scavenger or saprobic, eats the dead bodies of other animals, which have died naturally or killed by another animal 
Eg; jackals, vulture, ants, crow.
· Helotism: Association between 2 organisms in which one behaves as a master and the other as slave. Eg: Lichen’s (husband and wife), Master-fungus & Slave-algae.

Special Note:
1. A population with an equal number of births and death will show a plateau phase.
2. Gene flow is the transfer of genes between genetically distinct but inbreeding populations.
3. Allopatric speciation is caused by Geographical isolation but sympatric speciation is caused by Reproductive isolation.
4. Dance pattern of the Honey bee is communication.
5. Lentic: pertaining to standing water; swamp or lake, Lotic: pertaining to running water river or brook
6. Grassland with scattered trees is found in Savannah.
7. Difference between tropical forest and the temperate forest is that tropical forest has more angiosperm and temperate forest has more gymnosperm.
8. The forest that colours in autumn is a temperate deciduous forest.
9. An ecosystem does not normally alter because it is in a state of Homeostasis.
10. In an aqueous environment, microscopic animals and plants are collectively known as plankton.
11. Abyssal zone in the ocean has no sunlight but contains consumers and decomposers.
12. Flow of energy declines as it passes from lower to higher trophic levels. This is explained by the second law of thermodynamics.
13. Species diversity increases as one proceeds from high to low altitude and high to low latitude,
14. Pheromones secreted by certain exocrine skin glands, affect the mutual behaviour of members of species.
15. Stratification is more common in tropical rain forests.
16. Concept of life was given by Raunkier.
17. Sal forest is a deciduous forest.
18. Zone of the atmosphere near the ground is the troposphere.
19. Peak concentration of ozone occurs in the atmosphere above a height of 25Km.
20. Ozone layer is found in the stratosphere.
21. Limitation of food can counteract biotic potential.
22. The abundance of a species population within its habitat is called Niche density.
23. When the population reaches carrying capacity, then mortality = Birth rate.
24. Climatic and edaphic factors controlling the distribution of community constitute ecological niche.
25. The limiting factor in soil nitrification is soil pH.
26. Fertility of soil is measured by the ability to support life.
27. Greatest problem in water conservation is to reduce the amount of evaporation.
21. Temperature gradient is found in the thermocline region of the pond.
22. Pheromones are mainly used for communication.
23. Secondary growth is absent in hydrophytes.
24. Human population shows a J-shaped growth curve.
25. Competition is severe in a population that is irregular.

High Yielding Points from Ecology

1. Biotic potential refers to an increase in population under optimum conditions

2. The members of a form of polymorphic species interbreed among themselves and with members of other forms also

3. When a tiger attacks cheetahs, the stag with the best antlers is surrounded by other individuals to protect it. It is an example of Altruism

4. Area covered by members of a species in search of food and mates is called Bome range

5. Primary succession refers to the development of communities on a newly exposed habitat with no record of earlier vegetation

6. Climatic and edaphic factors controlling the distribution of a community constitute the ecological niche

1. The basis of the classification of hydrophyte, mesophyte and xerophytes is the availability of water

2. Hydrophytes have a less mechanical system as well as the feebly developed vascular system

3. The stem of submerged water plants is soft and weak because the supporting tissue and xylem are feebly developed

4. The classification of plants into hydrophytes, mesophytes and xerophytes was suggested by warming

5. A non–succulent xerophytes with thick leathery leaves having a white sticky waxy coating is Calotropis

The most characteristic feature of a xeric environment is low atmospheric humidity

7. Photosynthetic and respiratory gaseous exchange in hydrophytes takes place through the epidermis

1. Shey-Phoksundo National Park is situated in Dolpa and Mugu

2. Khaptad National Park which is also famous for Ashram of Khaptad swami is located in the Seti zone

3. One-horned rhinoceros, tiger and gharial crocodile are characteristics of Chitwan National Park and Bardiya National Park.

4. The main grass found in Shuklaphanta Wildlife Reserve which is extremely used by the local people for thatching is Imperta cylindrica and Saccharum heteropogon

5. Type of forest:
a. Tropical forest:
    * Found up to 4,000 ft
    * Covers southern Terai plains along Churia hills
    * Sal forest is found here
b. Temperate forest:
    * From 4,000 ft to 10,000 ft
    * Covers entire Mahabharat range
    * Also known as deciduous monsoon forest
c. Alpine forest:
    * Located in Alpine zone
    * From above 4,000 ft.

1. In a biosphere reserve, limited human activity is permitted in the buffer zone

2. In developing countries, the heaviest demand on forests is for fuelwood

3. A high density of tiger population in an area can result in Intraspecific competition

4. Man has identified only a part of the living species today % of identified species to the total is 1% - 10%

1. Primary or main source of energy in an ecosystem is sunlight (solar system)

2. The total energy fixed by a gram plant (Cicer arietinum) in an ecosystem, on the whole, is called gross production

3. When a big fish eats small fish which eats water fleas supported by phytoplankton, the water fleas are primary consumers

4. The most vital process for the existence of life on earth is photosynthesis by plants

5. If we completely remove the decomposers from an ecosystem, the ecosystem functioning will be adversely affected because mineral movement will be blocked

6. Flow of energy declines from lower to higher trophic levels in the ecosystem is mainly explained by the first law of thermodynamics

7. The number of primary producers within a specified area could be maximum in the pond ecosystem

8. The region consisting of long and severe winters growing season consisting of a few months of summers is a Tundra ecosystem

9. Good soil is which allows the water to percolate slowly from it

10. Animals like cockroaches, lizards and mice share the buildings of human dwellings. Such animals are called Inquilines

11. The productivity of all the autotrophs including green plants protists and bacteria is called community productivity


1. Biogeochemical cycling means cycling of nutrients in an ecosystem

2. Amount of nitrogen fixed by nitrogen-fixing organisms constitutes what fraction of our total requirement is 70%

3. Restoration of ecological equilibrium in mined areas can be achieved through revegetation of the mined habitats

4. The effect of pollution is first and most marked on the natural balance of our environment

5. Smog is a consequence of the rapid buildup of photochemical oxidants, pollutants and thermal inversion

6. Exposure of plants to high fluoride concentration results in necrosis or chlorosis characteristic in leaf tip and leaf margins

7. The worst environmental hazards were created accidents in nuclear power plants and MIC gas leaks in Ukraine in 1986 and Bhopal in 1984 (Only place is important)

8. Measurement of the rate of O2 consumption in the unit volume of water over a period of time is done to find out Biological oxygen demand (BOD).

9. If water pollution continues at its present rate, it will eventually make oxygen molecules unavailable to water plants

10. The effect of today’s radioactive fallout will probably be more harmful to children of future generations than children now living because mutated genes are frequently recessive

11. A sewage treatment process in which a portion of the decomposer bacteria present in the waste is recycled into the beginning of the process is called Activated sludge treatment.

12. Warm ocean surge of the Peru current recurring every 5-8 years or so in the east pacific of south America is widely known as El Nino
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