The sea anemone is transported on the back of hermit crab for reaching new food sources.Alternative term for this type of mutualism is proto cooperation.

Interdependence of mother and infant, husband and wife.

Plants, animals, and bacteria and fungi.

Population (size/density) increases by birth/hatching/germination and immigration that add individuals. Population (size/density) decreases by death and emigration. Population is regulated by food, space, disease, natural calamities and environmental factors.

(a) Mimicry. It is phenomenon in which a living organism modifies its form, appearance, structure or behaviour and looks like another living organism or some inanimate (non-living) object so as to defined from its predators, or to increase the chances of capturing they prey.
The individual which shows mimicry is called mimic while the animate or inanimate object with which a mimic resembles is called model. The concept of mimicry was first observed by an English naturalist, Henry Bates (1862 A.D.) so the phenomenon is also called Batesian mimicry.
Types: Mimicry is three types:
(i) Protective mimicry,
(ii) Aggressive mimicry,
(iii) Feigning death or Conscious mimicry.
(b) Acclimatisation. The gradual physiological adjustment to slowly changing new environmental conditions is known as acclimatisation. If some factors shift beyond the tolerance range, the organism can come to tolerance range or migrate to acclimatise.

The camel adjusts itself with desert environment and can use it as a habitat. The physical conditions prevailing in the desert and biological endowments of camel suit each other nicely e.g., it can easily move on hot sand and run at the speed of 25 kilometres per hour. Hump at the back of camel contains fats in the form of reserve food. Such adaptations are not found in the case of frog.

(i) They have short ears and short limbs.
(ii) Aquatic mammals have a thick layer of fat, called blubber under their skin, which acts as an insulator.

Physical Properties:
(i) Grain size
(ii) Water holding capacity
(iii) Aggregation of grains.
Chemical Properties:
(i) Mineral composition
(ii) pH of the soil.

The interaction is called commensalism.
The egrets always, forage close to where the cattle are grazing.
As they move, thJ cattle stir up and flush out from the vegetation the insects which otherwise might be difficult for the egrets to find and catch.
Thus, the egrets are benefitted while the cattle are neither benefitted nor harmed.

The mountain dwellers have
(i) higher red blood cell count.
(ii) higher haemoglobin content.
(iii) faster breathing rate.
(iv) decreased binding capacity of haemoglobin.

(a) Protocooperation
(b) Mutualism
(c) Mutualism
(d) Parasitism

(a) Differences between hibernation and aestivation

(b) Difference between ectotherms and endotherms.

Co-evolution of mutualists:
Evolution of the flower characteristics and its pollinator species is highly linked with each other as in wasp-fig relationship.
A given species of fig is pollinated by a specific (partner) wasp species.
The wasp pollinates the fig inflorescence while searching fon a suitable egg laying site.
The female wasp uses the ovary of flowers for oviposition (laying eggs) and the developing seeds provide nourishment to the young ones.
Later the young ones emerge from the fruits of fig.

Reproductive strategies:
(i) Some organisms breed only once in their life time-e.g. Bamboo, Pacific Salmon.
(ii) Some produce a large number of small-sized offspring-Oysters.
(iii) Some breed many times during their life time-e.g. birds.
(iv) Some produce a small number of large sized offspring, e.g. Mammals.

(i) Tropical rainforest    
(ii) Deciduous forest    
(iii) Desert    
(iv) Coniferous forest    
(v) Agricultural fields    
(vi) Grassland.

(a) Arctic tern    
(b) Tiger/Lion    
(c) Aphid    
(d) Chameleon    
(e) Glycosides (in Calotropis).

Effect of temperature or water scarcity and adaptation of animals. As discussed in (c) and reducing loss of water from body, and ability to tolerate arid condition.

(a)The study tells about the status of the population. A change in the population size can indicate the outcome of competition with another species, the impact of a predator or the effect of a pesticide application.
(b) The per cent cover is a more meaningful measure of population size, in case of a single huge banyan tree with C1 large canopy in an area where 200 small plants like Parthenium are present.
In such a case, stating that the population density of banyan is low is underestimating the enormous role of the banyan tree in the community.

Fig 1. represents  interaction between individuals of a single population.
Fig 2. represents  interaction between individuals of 3species (A,B,C) in a community.
Fig 3. represents a biome having 3 communities at different stages of development

Adaptation is the quality of the organism (morphological, physiological, behavioural) that enables the organism to survive and reproduce in its habitat. It adopts organism to live in different types of habitats.
Adaptation of desert plant are as follows:
(i) Desert plants have cuticle to minimise transpiration.
(ii) In some desert plant, leaves modify into spines to minimise loss of water.
(iii) They have long roots and adaptations to reduce transpiration, e.g., Acacia.
Adaptation of desert animal are as follows:
(i) Desert animals concentrate their urine for minimum loss of water, e.g., Kangaroo rat.
(ii) Desert animals absorb heat from the sun when the body temperature drop below the comfort zone.
(iii) They live in burrows during hot season and have little water requirement.

(a) The factors include
(i) The rotation of the earth around the sun and the tilt of its axis cause annual variation in the intensity and duration of temperature, which affects distinct reasons.
(ii) Annual variation in precipitation.
(b) (i) Scorching deserts of Rajasthan.
(ii) Rain-soaked Meghalaya forests
(iii) Deep ocean trenches.
(iv) Tropical rain forests
(v) High mountain tops. (any four)
(c) Interactions are necessary; they should be beneficial to all.

(a) Commensalism:
It is the interspecific interaction, where one species is benefitted by the association while the other is neither benefitted nor harmed, e.g. Sucker fish attached to a shark.
(b) Parasitism:
It is the interspecific interaction, where one species (called parasite) takes food and shelter from another living species (host) and damages the host in due course of time; the parasite is benefitted and the host is harmed,e.g. Tapeworm in the intestine of man.
(c) Camouflage:
It is an adaptation, where the animal (organism blends with the surroundings to escape detection by the predator, e.g. Frogs have olive green skin with patches of chromatophores to camouflage with the grasses.
(d) Mutualism:
It is the interspecific interaction, where both the interacting species are mutually benefitted, e.g. An alga and a fungus in a lichen. Rhizobium and legume plant.
(e) Interspecific competition: It is an interspecific interaction, where organisms of two different species compete with each other for certain resources, e.g. Flamingoes and fishes competing for their common food, i.e. zooplanktons.