(a) Mutualism - E.g: Lichen
(b) Commensalism - E.g: Orchids.

(a) Halophytes: Plants living in saline soils.
(b) Chasmophytes: Plants living in rocky crevices.
(c) Cryophytes: Plants living in ice surface.
(d) Psammophytes: Plants living in sandy soils

Gases let out to atmosphere causes climatic change. Emission of dust and aerosols from industries, automobiles, forest fire, SO₂ and DMS (dimethyl sulphur) play an important role in disturbing the temperature level of any region. Aerosols with small particles is reflecting the solar radiation entering the atmosphere. This is known as Albedo effect.

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

The interaction of organisms with their environment results in the establishment of grouping of organisms which is called ecological hierarchy.

Based on the temperature prevailing in an area, Raunkiaer classified the world's vegetation into the following four types.
(i) Megatherms
(ii) Mesotherms
(iii) Microtherms
(iv) Hekistotherms

S. No	Anemochory	Zoochory
a	Dispersal of seeds or fruits by wind.	Dispersal of seeds or fruits by animals
b	Seeds are minute or may have wings.	Seeds or fruit surface may have hooks or sicky glandular hairs are seen.

It is a technique of encasing seeds in a mixture of clay & soil humus & scattering them on to suitable ground, not planting of trees manually.

Submerged plants are unable to obtain full illumination because a lot of sunlight is absorbed by overlying layers of water this is not the case for exposed floating plants that receive sunlight directly.

Certain plants can also be used to remove cadmium from contaminated soil, this is known as phytoremediation.
Example: Eichhornia

The blue green light have short wavelength & penetrates into the water. Green algae is unable to use that component of light. Blue light can penetrate up to 500 ft depth therefore algae are unlikely to survive below that depth.

The interaction of organisms with their environment results in the establishment of grouping of organisms
Levels of ecological hierarchy

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

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:
1. Corolla length and proboscis length of butterflies and moths (Habenaria and Moth).
2. Bird's beak shape and flower shape and size.

(a) Carausium morosus (Stick insect)
(b) Phylliumfrondosum (Leaf insect).

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

1. Ground fire - Which is flame less and subterranean.
2. Surface fire - Which consumes the herbs and shrubs.
3. Crown fire - Which burns the forest canopy.

Thermal stratification is usually found in aquatic habitat. The change in the temperature profile with increasing depth in a water body is called thermal stratification. There are three kinds of thermal stratifications.
1. Epilimnion - The upper layer of warmer water.
2. Metalimnion - The middle layer with a zone of gradual decrease in temperature.
3. Hypolimnion - The bottom layer of colder water.

1. 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).
2. Many defense mechanisms are evolved to avoid their predations by plants. Examples:  Calotropis produces highly poisonous cardiac glycosides, tobacco produces nicotine, coffee plants produce caffeine, Cinchona plant produces quinine. Thorns of Bougainvillea,  spines of Opuntia, and latex of cacti also protect them from Predators.

(a) Mutualism: It is an interaction between two species of organisms in which both are benefitted from the obligate association. The following are common examples of mutualism.
(b) 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.
Other examples:
Water fern (Azolla) and Nitrogen fixing Cyanobacterium (Anabaena) .

Aerosols with small particles is reflecting the solar radiation entering the atmosphere. This is known as Albedo effect.
Effects:
1. It reduces the temperature limits, photosynthesis & respiration.
2. The sulphur compounds are responsible for acid rain due to acidification of rain water and destroy the ozone.

The differences between habitat and niche are as follows.

S. No	Habitat	Niche
1	A specific physical space occupied by an organism (species).	A functional space occupied by an organism in the same eco-system
2	Same habitat may be shared by many organisms (species).	A single niche is occupied by a single species.
3	Habitat specificity is exhibited by organism.	Organisms may change their niche with time and season

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.
1. Stem of some epiphytes are succulent and develop pseudo bulb or tuber.
2. Generally the leaves are lesser in number and may be fleshy and leathery.
3. Myrmecophily is a common occurrence in the epiphytic vegetation to prevent the predators
4. The fruits and seeds are very small and usually dispersed by wind, insects and birds.

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

Advantages of seed dispersal:
1. Seeds escape from mortality near the parent plants due to predation by animals or getting diseases and also avoiding competition.
2. Dispersal also gives a chance to occupy favourable sites for growth.
3. It is an important process in the movement of plant genes particularly this is the only method available for self-fertilized flowers and maternally transmitted genes in outcrossing plants.
4. Seed dispersal by animals help in conservation of many species even in human altered ecosystems.
5. Understanding of fruits and seed dispersal acts as a key for proper functioning and establishment of many ecosystems from deserts to evergreen forests and also for the maintenance of biodiversity conservation and restoration of ecosystems.
Seed ball:
1. It is an ancient Japanese technique of encasing seeds in a mixture of clay and soil humus (also in cow dung).
2. It also includes the soil humus scattering them on to the suitable; not planting of trees manually.
3. This method is suitable for barren and degraded lands for tree regeneration and vegetation before monsoon period where the suitable dispersal agents become rare.

The plants which are living in dry or xeric condition are known as Xerophytes.
Xerophytic habitat can be of two different types They are:
(a) physical dryness: In these habitats, soil has a little amount of water due to the inability of the soil to hold water because of low rainfall.
(b) physiological dryness: In these habitats, water is sufficiently present but plants are unable to absorb it because of the absence of capillary spaces. Example: Plants in salty and acidic soil.
Based on adaptive characters xerophytes are classified into three categories. They are Ephemerals, Succulents and Non - succulent plants.

(i) Ephemerals: These are also called drought escapers or drought evaders. These plants complete their life cycle within a short period (single season). These are not true xerophytes. Examples: Argemone, Mollugo, Tribulus and Tephrosia.
(ii) Succulents: These are also called drought enduring plants. These plants store water in their plant parts during the dry period. These plants develop certain adaptive characters to resist extreme ,drought conditions. Examples: Opuntia, Aloe, Bryophyllum and Begonia.
(iii) Non succulents: These are also called drought resistant plants ( true xerophytes). They face both external and internal dryness. They have many adaptations to resist dry conditions. Examples: Casuarina, Nerium, Zizyphus and Acacia.

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.
Horizon Description O-Horizon (Organic horizon) Humus It consists of fresh or partially decomposed organic matter.
01 - Freshly fallen leaves, twigs, flowers and fruits.
02 - Dead plants, animals and their excreta decomposed by micro-organisms.
Usually absent in agricultural and deserts. A-Horizon
(Leached horizon)
Topsoil - Often rich in humus and minerals. It consists of top soil with humus, living creatures and in-organic minerals.
A1 - Dark and rich in organic matter because of mixture of organic and mineral matters.
A2 - Light coloured layer with large sized mineral particles. B-Horizon (Accumulation horizon) (Subsoil - Poor in humus, rich in minerals) It consists of iron, aluminium and silica rich clay organic compounds. C - Horizon (partially weathered horizon) Weathered rock Fragments - Little or no plant or animal life. It consists of parent materials of soil, composed of little amount of organic matters without life forms. R-Horizon (Parent material) Bedrock It is a parent bed rock upon which underground water is found.