The living environment

Question 1

Living environment

Answer 1

The living environment can be defined as the world of living organisms but, just like the concept of life, it is hard to define precisely. What is important to know is that it is characterized by a specific structure, or ecosystem, and by the relationships between the living organisms inhabiting it.

Question 2

Ecosystem

Answer 2

The ecosystem is the structural and functional unit of ecology where the living organisms interact with each other and the surrounding environment. In other words, an ecosystem is a chain of interactions between organisms and their environment. The term “Ecosystem” was first coined by A.G.Tansley, an English botanist, in 1935.

Question 3

Types of ecosystem

Answer 3

An ecosystem can be as small as an oasis in a desert, or as big as an ocean, spanning thousands of miles. There are two types of ecosystem:

• Terrestrial Ecosystem
• Aquatic Ecosystem

Question 4

Terrestrial Ecosystem

Answer 4

Terrestrial ecosystems are exclusively land-based ecosystems. There are different types of terrestrial ecosystems distributed around various geological zones. They are as follows:

1. Forest Ecosystems
2. Grassland Ecosystems
3. Tundra Ecosystems
4. Desert Ecosystem

Forest Ecosystem
A forest ecosystem consists of several plants, animals and microorganisms that live in coordination with the abiotic factors of the environment. Forests help in maintaining the temperature of the earth and are the major carbon sink.

Grassland Ecosystem
In a grassland ecosystem, the vegetation is dominated by grasses and herbs.
Temperate grasslands, savanna grasslands are some of the examples of grassland ecosystems.

Tundra Ecosystem
Tundra ecosystems are devoid of trees and are found in cold climates or where rainfall is scarce. These are covered with snow for most of the year. The ecosystem in the Arctic or mountain tops is tundra type.

Desert Ecosystem
Deserts are found throughout the world. These are regions with very little rainfall. The days are hot and the nights are cold.

Question 5

Aquatic ecosystem

Answer 5

Aquatic ecosystems are ecosystems present in a body of water. These can be further divided into two types, namely:

1. Freshwater Ecosystem
2. Marine Ecosystem

Freshwater Ecosystem
The freshwater ecosystem is an aquatic ecosystem that includes lakes, ponds, rivers, streams and wetlands. These have no salt content in contrast with the marine ecosystem.

Marine Ecosystem
The marine ecosystem includes seas and oceans. These have a more substantial salt content and greater biodiversity in comparison to the freshwater ecosystem.

Question 6

Structure of the Ecosystem

Answer 6

The structure of an ecosystem is characterized by the organization of both biotic and abiotic components. This includes the distribution of energy in our environment. It also includes the climatic conditions prevailing in that particular environment. The structure of an ecosystem can be split into two main components, namely:

• Biotic Components
• Abiotic Components

The biotic and abiotic components are interrelated in an ecosystem. It is an open system where the energy and components can flow throughout the boundaries.

Question 7

Biotic components

Answer 7

Biotic components refer to all life in an ecosystem. Based on nutrition, biotic components can be categorized into autotrophs, heterotrophs and saprotrophs (or decomposers).

Question 8

Abiotic components

Answer 8

Abiotic components are the non-living component of an ecosystem. It includes air, water, soil, minerals, sunlight, temperature, nutrients, wind, altitude, turbidity, etc.

Question 9

Autotrophs

Answer 9

Producers include all autotrophs such as plants. They are called autotrophs as they can produce food through the process of photosynthesis. Consequently, all other organisms higher up on the food chain rely on producers for food.

Question 10

Heterotrophs

Answer 10

Consumers or heterotrophs are organisms that depend on other organisms for food. Consumers are further classified into primary consumers, secondary consumers and tertiary consumers.

• Primary consumers are always herbivores that they rely on producers for food.
• Secondary consumers depend on primary consumers for energy. They can
either be a carnivore or an omnivore.
• Tertiary consumers are organisms that depend on secondary consumers for
food. Tertiary consumers can also be an omnivore.
• Quaternary consumers are present in some food chains. These organisms prey on tertiary consumers for energy. Furthermore, they are usually at the top of a food chain as they have no natural predators.

Question 11

Decomposers

Answer 11

Decomposers include saprophytes such as fungi and bacteria. They directly thrive on the dead and decaying organic matter. Decomposers are essential for the ecosystem as they help in recycling nutrients to be reused by plants.

Question 12

Functions of the ecosystem

Answer 12

1. It regulates the essential ecological processes, supports life systems and renders stability.
2. It is also responsible for the cycling of nutrients between biotic and abiotic
   components.
3. It maintains a balance among the various trophic levels in the ecosystem.
4. It cycles the minerals through the biosphere.
5. The abiotic components help in the synthesis of organic components that
   involves the exchange of energy.

Question 13

Food Chain

Answer 13

The sun is the ultimate source of energy on earth. It provides the energy required for all plant life. The plants utilize this energy for the process of photosynthesis, which is used to synthesize their food. During this biological process, light energy is converted into chemical energy and is passed on
through successive levels. The flow of energy from a producer, to a consumer and eventually, to an apex predator or a detritivore is called the food chain.
Dead and decaying matter, along with organic debris, is broken down into its constituents by scavengers. The reducers then absorb these constituents. After gaining the energy, the reducers liberate molecules to the environment, which can be utilized again by the producers.

The food chain is an ideal representation of flow of energy in the ecosystem. In food chain, the plants or producers are consumed by only the primary
consumers, primary consumers are fed by only the secondary consumers and so on.

Any food chain consists of three main tropic levels, viz., producers, consumers and decomposers. The energy efficiency of each tropic level is very low. Hence, shorter the food chain greater will be the accessibility of food.

The typical food chain in a ground ecosystem proceeds as grass mouse > snake > hawk.

Question 14

Food web

Answer 14

Charles Elton presented the food web concept in year 1927, which he termed as food cycle.

A food web is a graphical depiction of feeding connections among species of an ecological community. Food web includes food chains of a particular ecosystem. The food web is an illustration of various techniques of feeding that links the ecosystem.

The food web also explains the energy flow through species of a community as a result of their feeding relationships. All the food chains are interconnected and overlapping within an ecosystem and they constitute a food web.

In natural environment or an ecosystem, the relationships between the food
chains are interrelated. These relationships are very complex, as one organism may be a part of multiple food chains. Hence, a web like structure is formed in place of a linear food chain.

Food webs are an inseparable part of an ecosystem; these food webs permit an organism to obtain food from more than one type of organism of the lower trophic level.

Question 15

Energy budget

Answer 15

An energy budget is the specification of the uptake of energy from the environment by an organism (feeding and digestion) and of the use of this energy for the various purposes:
maintenance, development, growth and reproduction. A static energy budget represents a kind of snapshot of these fluxes for an individual in a given state, while a dynamic energy budget follows the changes of these fluxes during the life cycle of an organism.

Question 16

Emergent properties

Answer 16

Emergent properties are properties that manifest themselves as the result of various system components working together, not as a property of any individual component. To put it another way, it is a property that a complex system or collection of system parts has, but which individual parts do not possess. Since emergent properties are viewable at more macro levels of analysis, only examining individual parts of the system will prevent one from seeing emergent properties → the whole is greater than the sum of the parts.

When units of biological material are put together, the properties of the new material are not always additive, or equal to the sum of the properties of the components. Instead, at each level, new properties and rules emerge that cannot be predicted by observations and full knowledge of the lower levels. Such properties are called emergent properties (Novikoff, 1945).
Life itself is an example of an emergent property. For instance, a single-celled bacterium is alive, but if you separate the macromolecules that combined to create the bacterium, these units are not alive. Based on our knowledge of macromolecules, we would not have been able to predict that they could combine to form a living organism, nor could we have predicted all of the characteristics of the resulting bacterium.

Question 17

Energy flow

Answer 17

●Not all trophic levels of a food chain receive the same amount of energy. Only about 10% of the Sun’s energy absorbed by plants is transferred to the
consumers at the next trophic level. Where does 90%of the energy go? Some of it is used to fuel body processes such as growth, repair, and reproduction.
Most of it is transferred to the atmosphere as heat. We can represent the energy flow of an ecosystem in an energy pyramid. The different levels of the pyramid represent the different groups of a food chain or food web.
The producers are found at the bottom of the pyramid. The more levels there are in a pyramid, the less energy is available to the organism at the top.

● Energy moves through an ecosystem in a single direction. First it flows from the Sun to autotrophs, or producers. Then it flows from producers to consumers. Energy never flows backward from consumers to producers.

● A small percentage of organisms use sulfur compounds from volcanic
sea vents deep in the ocean as their source of energy. Instead of using
Sunlight in photosynthesis, these organisms use chemicals to aid in
chemosynthesis. They make their own food, just like in photosynthesis

Question 18

Ecological pyramids

Answer 18

Ecological pyramids are a model that captures the amounts of energy contained in each level, as well as what level it came from and where it is
going. The advantage of pyramids over webs is that they can capture the abundance of organisms and energy contained in each level better than webs.

The disadvantage of pyramids is that they frequently ignore the great variety of organisms at each level and provide only an average of energy transfer.

On average, only 10 percent of the energy contained in one level reaches the next higher level. The rest is lost to heat and maintaining body function. However, ecological efficiency varies greatly. It is generally highest in plants and lowest in animals that can maintain a stable internal body temperature like mammals or birds. The number of organisms at each level and the total biomass can be determined. There are usually fewer large animals than small animals. Biomass may be a better indicator of energy contained in the level than abundance.