Question

Think and answer.
(a) We prepare a variety of foodstuffs and dishes at home. Are we then autotrophic organisms ?
(b) Which organisms are greater in number - autotrophs or heterotrophs ? Why?
(c) The number of heterotrophs found in desert regions is smaller. However, they are found in greater numbers in the sea. Why is this so ?
(d) What damage or harm do ectoparasitic and endoparasitic animals cause ?
(e) Why is plant food not produced in any other parts of the plant except the green ones ?

Answer 1

a. By preparing variety of foodstuffs and dishes at home, we do not become autotrophic. Autotrophic is a term which is used for organisms which can produce their own food. We humans depend on plants for our food and the products which we get from them are used by us to make a variety of foodstuffs. Also, autotrophic organisms contain chloroplast which is an absolute necessity to be classified as an autotroph and we do not possess any such structures. So, we cannot be considered autotrophs.

b. Autotrophs are the organisms which are greater in number. It is because heterotrophs are dependant on autotrophs to meet their food requirements. If heterotrophs exceed the number of autotrophs, then all the autotrophs will vanish and so will be the heterotrophs. However, this is not the case because autotrophs are always more than heterotrophs so that they can help in sustaining the heterotrophs.

c. The conditions in deserts are extremely difficult for survival of organisms. Not all kinds of organisms can survive in such harsh climatic conditions, which means there are only few types of organisms which would be found in this region. Since, there are not many kinds of plants and animals which are found in this region, heterotrophs would not be able to survive and would die of starvation. That is why less heterotrophs are found in desert areas. However, in case of a habitat like sea, there are plenty of organisms which are found in region ranging from aquatic plants, to small fishes to big fishes. It is an environment which supports the survival of heterotrophs and thus more heterotrophs are found in this region.

d. Parasitism is a type interaction in which one of the partners is benefited because it resides outside or inside the body of the host and gets free accommodation and food while the host is affected due to loss of nutrients. Ectoparasites and endoparasites devoid the host of its nutrition. Some of the parasites are known to cause diseases like Ascaris/roundworm which is an endoparasite of intestine causes ascariasis. Another example is of Wuchereria which causes elephantiasis or filariasis. It is an endoparasite which lives in lymphatic vessels of lower limbs.
Lice or ticks which are found in humans and dogs respectively are examples of ectoparasites. They absorb the nutrients from their host.

e. Plant food is produced by a special process known as photosynthesis. The process of photosynthesis requires specialised structures called chloroplasts and these structures are found only in green regions of plants. The green colour of specific parts of plants is due to the presence of chlorophyll pigment present in these chloroplasts. Structures in plants which do not contain chloroplast, do not appear green in colour and are not capable of producing food.