Biodiversity plays major role in many ecosystem services that nature provides:
1. Amazon forests produce 20 percent of total oxygen of earth's atmosphere through photosynthesis.
2. Ecosystems provide pollinator layers, bees, birds, and bats.

Genetic Diversity.
(i) Greater the genetic diversity among organisms of a species, more sustenance it has against environmental perturbations, The genetically uniform populations are highly prone to diseases and harsh environment.
(ii) The genetic variation shown by Rauwolfia can be in terms of the conservation and potency of the chemical reserpine.
There are more than 50,000 genetically different strains of rich and 1000 varieties of mango in India.

Nematode-resistant tobacco plants are produced through RNA interference. The process RNA interference (RNAi) involves silencing of a specific mRNA.
A complementary double-stranded RNA binds to the mRNA and prevents its translation.
The complementary! RNA for making the double stranded RNA comes either from an infection by RNA viruses or mobile genetic elements, called transposons, which replicate through an RNA-intermediate.
The nematode-specific genes were introduced into the host plant by the use. of Agrobacterium vectors.
The introduction of DNA is such that it produced both sense and anti-sense RNA in the host cells.
These two RNAs are complementary to each other and hence form a double-stranded RNA, which initiates the RNA interference and silencing of mRNA.
The parasite could not live in such a transgenic host that expresses the specific interfering double-strandedRNA; so, the transgenic plant is protected from the nematode.

1. It is believed that the rise in temperature is leading to deleterious changes in the environment and resulting in odd climatic changes (like EI Nino-effect) leading to increased melting of polar ice caps and snow caps in other places like Himalayas.
2. Over many years, this will result in a rise in sea level that can submerge many coastal areas.

(i) Certain insect species and frogs have camouflage (cryptic colouration) to avoid detection by their predators.
(ii) Some animals are highly distasteful to their predators, e.g. monarch butterfly accumulates a chemical by feeding on a poisonous weed during its caterpillar stage.
(iii) Some prey are poisonous and hence are avoided by predators.
(iv) Plants have developed thorns and spines as defence mechanism against browsing animals.
(v) Some plants produce certain chemicals which affect the metabolism of the herbivores.

Desert lizards cope with the temperature variations in their habitat by behaviour means.
They bask in the sun and absorb heat when their body temperature drops below the comfort zone.
They move into the shade when the temperature starts increasing.

A single-stranded DNA or RNA is tagged with a radioactive molecule and used as a probe.
It is allowed to hybridise with its complementary DNA in a clone of cells, followed by detection using autoradiography.
The clone having the mutant gene will not appear on the photographic film, because the probe will not be complementary with the mutated gene.

1. Sun is the ultimate source of energy for all ecosystems on the earth.
2. Only about 50% of the incident solar radiation is photosynthetically active radiation (PAR).
3. Plants capture only 2-10% of the PAR and all organisms are dependent for their food on producers, either directly or indirectly. 
4. The flow of energy from the sun to producers and then to consumers is unidirectional and is keeping with the first law of thermodynamics.
5. Ecosystems need a continuous supply of energy for the synthesis of molecules needed and to counteract the tendency towards increasing disorderliness, i.e. energy flow follows the second law of thermodynamics too.

Deletion of the gene for ADA causes ADAdeficiency, i.e. deficiency of adenosine deaminase, the enzyme which is crucial for the normal functioning of our immune system.
 ADA deficiency can be cured by:
(i) Bone marrow transplantation.
(ii) Enzyme replacement therapy in which functional ADA is given by injection.
(iii) Gene therapy, in which functional ADA cDNA is introduced into lymphocytes or into cells at early embryonic stage.

Narrowly utilitarian: Humans derive direct economic benefits from nature (or explained with example). Broadly utilitarian: Provides many ecosystem services such as provide oxygen (through photosynthesis) prevents pollution, provides aesthetic pleasure.
Ehical: We share this planet with millions of other organisms and every species has intrinsic value and it is our moral duty to conserve them and pass on the legacy to future generation.

Man can be a primary as well as secondary consumer because man eats plants as well as meat of other animals. So, man is herbivores as well as carnivores.

Co-evolution is a phenomenon where many parasites have evolved to be host-specific in such a way that both the host and parasite tend to co-evolve, i.e.if the host develops/evolves special mechanism for rejecting or resisting the parasite the latter has to evolve mechanism to counteract and neutralise them to succeed with the same host species, e.g. malarial parasite.
Parasites have special adaptations according to their lifestyles such as; loss of unnecessary sense organs, presence of adhesive organs or suckers, loss of digestive system and high reproductive system

Warm water can hold much less dissolved oxygen than cold water. Also, rise in temperature speeds up animal metabolism increasing O₂ requirement thus further aggravating O₂ problem for aquatic animals.

Genetically modified organisms are the living organisms (plants, animals, or bacteria) which have been genetically 'engineered' by the insertion of a foreign gene (a transgene).

1. In Antarctica, winter (June to August) months receive no sunlight and the temperature is about - 85 °C that facilitates the formation of ice clouds.
2. The Antarctica air is completely isolated from the rest of the world by a natural circulation of wind, called polar vortex.
3. The ice clouds provide a catalytic surface on which the chlorine atoms react with ozone and degrade it; since light is necessary,it happens with the return of sun in spring .(September and October). 
Effects:
The UV-B radiation reaches the earth and causes the following :
(i) It damages the DNA and mutations arise.
(ii) It causes ageing of skin, damage to skin cells and ultimately causes skin cancer.
(iii) It causes inflammation of cornea (called snow-blindness) and cataract.
(iv) It is lethal to microbes.

1. It refers to the increase in concentration of the harmful/toxic substances at successive trophic levels.
2. It happens because such harmful/toxic substances can neither be metabolised nor excreted, but are passed onto the next (higher) trophic level.
3. In fish-eating birds, the high concentrations of DDT disturb the calcium metabolism.
4. It causes thinning of eggshell and the premature breaking of such eggs leads to a decline in bird populations of fish-eating birds.

1. When DDT is: sprayed on the crop plants, it remains in the soil as it is non-biodegradable and enters the plant.
2. As it travels through food chain, it undergoes biomagnification, i.e. increase in concentration at successive higher trophic levels, as it can neither be metabolised nor excreted; this causes disorders in those organisms.
3. In birds, a high concentration of DDT interferes with calcium metabolism and causes thinning of egg shells leading to their premature breaking; consequently there is a decline in bird population.

Fungi produce various kinds of thick-walled spores to survive under unfavorable conditions; they germinate when conditions become favorable.
Zooplanktons enter diapause, a stage of suspended development, under unfavourable conditions.
Bears go into hibernation during winter to escape in time of unfavourable conditions.

(a)  (i) Per cent cover.
(ii) Number caught per trap for fishes.
(iii) Pug marks or faecal pellets for tiger census.
(b) The population density tells us about the status of a species, i.e. the outcome of competition, impact of predation, or effect of pesticides, etc.

1. The pyramid is inverted.
2. Since the biomass of fishes far exceeds that of the phytoplanktons, the pyramid is inverted.