Dispersal by Animals (Zoochory)
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:
a. Some fruits have sticky glandular hairs by which they adhere to the fur of grazing animals. Example: Boerhaavia and Cleome.
b. Some fruits have viscid layer which adhere to the beak of the bird which eat them and when they rub them on to the branch of the tree, they disperse and germinate. Example: Cordia and Alangium.
iii. Fleshy fruits: Some fleshy fruits with conspicuous colours are dispersed by human beings to distant places after consumption.
Example: Mango and Diplocyclos

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.

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

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.

i. Free floating hydrophytes: These plants float freely on the surface of water. They remain in contact with water and air, but not with soil. Examples: Eichhornia, Pistia and Wolffia (smallest flowering plant).
ii. 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. Lotus seeds showing highest longevity in plant kingdom.
iii. Submerged floating hydrophytes: These plants are completely submerged in water and not in contact with soil and air. Examples: Ceratophyllum and Utricularia.
iv. 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.
v. 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.

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.
Holoparasites:
The organisms which are dependent upon the host plants for their entire nutrition are called Holoparasites. They are also called total parasites.
Examples:
1. 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.
2. Balanophora, orobanche and Refflesia are the total root parasites found on higher plants.

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.

1. In many species of fig trees, there is a one-to one relationship with the pollinator species of wasp. It means that a given fig species can be pollinated only by its 'partner' wasp species & no other species.
2. The female wasp uses the fruit not only as an oviposition (egg, laying) site but uses the developing seeds within the fruit for nourishing its larvae.
3. The wasp pollinates the fig inflorescence while searching for suitable egg-laying sites.
4. In return for the favour of pollination the fig offers the wasp, some of its developing seeds, as food for the developing wasp larvae.
5. The relationship that operates here is co-evolution.