In an aquarium two herbivorous species of fish are living together and feeding on phytoplanktons. As per the Gause's principle, one of the species is to be eliminated in due course of time, but both are surviving well in the aquarium. Give possible reasons.
Competition is a rivalry relationship between two or more organisms. A competition between individual of same species (intraspecific) is more acute than the competition between individual of different species as all the members in a intraspecific competition have same basic requirements like food, water, light, space, mating and shelter.
But this is true only when resources are limited. According to Gause's principle, one of the species is to be eliminated.
But studies recently have revealed that species facing intraspecific competition may evolve mechanism to pencourage co-existence rather than exclusion. This can also be done by a method known as ' resource partitioning'.
While living in and on the host species, the animal parasite has evolved certain adaptations. Describe these adaptations with examples.
Parasites have evolved special adaptations such as
(i) The loss of unnecessary sense organs as in lice, mites and fleas don't have wings.
(ii) Presence of adhesive organs or suckers to cling on to the host-in tapeworms and leeches.
(iii) Loss of digestive system i.e., tapeworm.
(iv) High reproductive capacity i.e., roundworm produces large progeny.
Do you agree that regional and local variations exist within each biome? Substantiate your answer with suitable example.
A biome can be define as the large communities of the world and shows that area with similar climate have communities of same type. Climate is the main factor that determine the type of soil which in turn determines the type of vegetation. The type of vegetation and climate together determine the kind of microorganisms and animals.
The other determining factors are latitude and altitude, intensity and duration of winter and summer days, water mass and topography. The main biome of the world does not show boundary of any country and regional and local variations exist in each biome.
e.g., temperate deciduous forest receive an annual precipitation between $75-150 \mathrm{~cm}$ and tropical rain forest show a rainfall above $140 \mathrm{~cm} / \mathrm{yr}$ which may reach upto $400 \mathrm{~cm} / \mathrm{yr}$.
Which element is responsible for causing soil salinity? At what concentration does the soil become saline?
Soil salinity is the salt content in soil, which is caused by improper irrigation. The process of increasing salt content is termed as salinisation.
Causes of Soil Salinity The high salt concentration of soil is caused by improper irrigation method from a salt laden water table. When salt concentration in soil is increased, than it get accumulated due to evaporation.
Human activities like fertilising crop is also responsible for salinity of soil. As fertiliser contain potassium, which can form a naturally occuring salt-sylvite. Salinity of soil degrades soil and vegetation. Normally the pH value of soil comprises between 2.2-9.7, while above which the soil is degrading by salt content.
Does light factor affect the distribution of organisms? Write a brief note giving suitable examples of either plants or animals.
Plants require sunlight for photosynthesis. Therefore, light is an important factor that affects the distribution of plants. e.g.,
(i) Many species of small plants (herbs and shrubs) growing in forests are adapted to photosynthesise optimally under very low light conditions so they will be seen distributed in shady areas under tall, canopied trees.
(ii) Many plants in the shade will grow vertically to gain access to light. These plants will appear to have smaller leafs and smaller than others of the same species of the same age found in conditions with better sunlight.
(iii) Large sized trees will be present in areas that get abundant sunlight.
(iv) Plants dependent on sunlight to meet their photoperiodic requirements for flowering, will try to be distributed in area, where this requirement is being met for their reproductive success.