Sample Materials for CSAT Paper -1 (G.S.) Pre 2013: "Environment and Ecology: Organisms and the Environment"

Subject: Environment and Ecology
Topic: Organisms and the Environment

In nature, organisms can survive only in appropriate environments, interact with each other, and are influenced by the whole complex of environmental factors. Ecology is the branch of biology that deals with the study of interaction between organisms and their environments. An understanding of ecological principles is needed for the sustainable use of resources, and to evolve strategies for the mitigation of environmental problems at local, regional and global levels. In this chapter, you will learn the effects of environmental factors of organisms, the significance of the range of tolerance, and adaptations of organism to varying physical environmental conditions.

Level of Organisation

In ecology, we study the distribution and abundance of organisms, their interactions among themselves and with the physical environment. The latter is comprised of lithosphere, hydrosphere and the atmosphere. Ernst Haeckel, in 1869, has its origin from the Greek word, Oikos meaning ‘home’, and logos meaning ‘to study’. Like other fields of learning, the developments in the field of ecology have been gradual. Ecology has progressed from natural history and biogeography to ecosystem ecology. More recently, global ecology with an emphasis on climate change, biodiversity conservation and ecological sustainability has been emphasised. Biology is a field of enquiry from genes to the ecosystems, forming a spectrum of several levels of organisation. These levels, in the ascending order complexity, include the genes, cells, tissues organs, individual organism, population, biological community, ecosystem, landscape, biome and the biosphere. In ecology we study about the organisms, populations, biological community, ecosystem, landscape and the biosphere. It should be understood that one level or organisation integrates with the other levels, and there are no sharp lines or breaks in the functional sense among various levels.

Organisms are the basic unit of study in ecology. At the level of organism, we intend to understand the form, physiology and behaviour, distribution and adaptations in relation to the environmental conditions. Similar organisms having the potential for interbreeding and producing fertile offspring constitute what we call species. Population is a group of individuals of a plant or an animal species, inhabiting a given area. For example, all individuals of elephants in an area constitute its population. We also study how two populations interact, a predator with its prey, or a parasite with its host. Competition, mutualism and predation are various types of interactions between organisms. The biological community is an assemblage of populations of plants, animals, bacteria and fungi that live in an area and interact with each other. A biological community has a distinct species composition and structure. An ecosystem is composed of a biological community, integrated with its physical environment through the exchange of energy and recycling of the nutrients. The structure and functioning of ecosystem shall be described in detail.

A landscape is a unit of land with a natural boundary having a mosaic of patches. These patches generally represents different ecosystems. A biome is a large regional unit characterised by a major vegetation type and associated fauna found in a specific climatic zone. Some examples of terrestrial biomes are desert, temperate deciduous forest, tropical rain forest, etc. On a global scale, all the earth’s terrestrial biomes and aquatic systems consti-tute the biosphere. The biosphere consists of the lower atmosphere, the land and the oceans, rivers and lakes, where living organisms are found.

Answer of Question 1: D

Answer of Question 2: A