# Exercise-6B Heat and Energy Concise Class-9 ICSE Physics Selina Publishers

Exercise-6B Heat and Energy Concise Class-9 ICSE Physics Selina Publishers Solutions Chapter-6 . Step By Step ICSE Selina Concise Solutions of Chapter-6 Heat and Energy  with Exercise-6(A), Exercise-6(B) , Exercise-6(C) and Exercise-6(D) including Numerical and MCQ Questions Solved Visit official Website CISCE for detail information about ICSE Board Class-9.

 Board ICSE Publications Selina Publication Subject Physics Class 9th Chapter-6 Heat and Energy  Exe-6(B) Book Name Concise Topics Solution of Exercise-6(A),  MCQ-6(A)   Exercise-6(B)  MCQ-6(B),  Exercise-6(C),  MCQ-6(C) and Exercise-6(D),  MCQ-6(D) Academic Session 2021-2022

## Exercise-6B Heat and Energy Concise Class-9 ICSE Physics Selina Publishers

–: Select Topics :–

Exercise-6(A),  MCQ-6(A)

Exercise-6(B),  MCQ-6(B)

Exercise-6(C),  MCQ-6(C)

Exercise-6(D),  MCQ-6(D)

Note :-  Before Viewing Selina Concise Physics Solutions of Chapter-6 Heat and Energy for ICSE Class-9 Physics. Read the whole chapter carefully and Solved all example of Chapter-6 Heat and Energy for Class-9 Physics.

Page 132

#### Question 1

What is an ecosystem?  Name its two components.

A unit composed of biotic components (i.e. producers, consumers and decomposers) and abiotic components (i.e. light, heat, rain, and humidity, inorganic and organic substances) is called an ecosystem.

#### Question 2

What is the source of energy for all ecosystems?

The source of energy for all ecosystems is the Sun.

#### Question 3

State the importance of green plants in an ecosystem

Green plants absorb most of the energy falling on them and by the process of photosynthesis they produce food for the consumers. Plants, being primary producers are of great importance in the ecosystem. They also maintain the balance of oxygen and carbon dioxide on earth.

#### Question 4

Differentiate between the producers and consumers.

Producers like plants and some bacteria are capable of producing its own food using the energy of sun but consumers are not capable of producing their own food. They depend on producers for food.

#### Question 5  Exercise-6B Heat and Energy Concise Class-9

State the functions of decomposers in an ecosystem.

The role of a decomposer is to break down dead organisms and then feed on them. The nutrients created by the dead organisms are returned to the soil to be later used by the producers. Once these deceased organisms are returned to the soil, they are used as food by bacteria and fungi by transforming the complex organic materials into simpler nutrients. The simpler products can then be used by producers to restart the cycle. These decomposers play an important role in every ecosystem.

#### Question 6

What is a food chain?

A food chain shows the feeding relationship between different living things in a particular environment or habitat. Often, a plant will begin a food chain because it can make its own food using energy from the Sun. In addition, a food chain represents a series of events in which food and energy are transferred from one organism in an ecosystem to another. Food chains show how energy is passed from the sun to producers, from producers to consumers, and from consumers to decomposers.

#### Question 7

Draw a simple diagram showing a food chain.

#### Question 8

Describe the energy flow in an ecosystem.

Ecosystems maintain themselves by cycling energy and nutrients obtained from external sources. At the first trophic level, primary producers (plants, algae, and some bacteria) use solar energy to produce organic plant material through photosynthesis. Herbivores-animals that feed solely on plants-make up the second trophic level.

##### Predators that eat herbivores comprise the third trophic level;

if larger predators are present, they represent still higher trophic levels. Decomposers, which include bacteria, fungi etc. break down wastes and dead organisms and return nutrients to the soil.

On average about 10 percent of net energy production at one trophic level is passed on to the next level. Processes that reduce the energy transferred between trophic levels include respiration, growth and reproduction, defecation, and non-predatory death.

The low rate of energy transfer between trophic levels makes decomposers generally more important than producers in terms of energy flow. Decomposers process large amounts of organic material and return nutrients to the ecosystem in inorganic forms, which are then taken up again by primary producers.

#### Question 9

State the law which governs the energy flow in an ecosystem.

The laws of thermodynamics govern the energy flow in the ecosystem.

According to the first law of thermodynamic, the energy can be transformed from one form to the other form, but it can neither be created nor destroyed.

According to the second law of thermodynamics, when energy is put to work, a part of it is always converted in un-useful form such as heat mainly due to friction and radiation.

#### Question 10

Show that the energy flow in an ecosystem is linear.

The energy flow in ecosystem is linear i.e., it moves in a fixed direction. The solar energy is absorbed by plants and a part of it is converted into food. These plants (or primary producers) are then eaten by the primary consumers, which are consumed by secondary consumers and the secondary by tertiary consumers.

This cycle is unidirectional. The dead and decomposed are fed by decomposers, which return the nutrients to the soil. At the end, the energy reaches the degraded state. It does not return to the sun to make the process cyclic, thus energy flow is linear.

#### Question 11  Exercise-6B Heat and Energy Concise Class-9

Draw a simple diagram showing the energy flow in a food chain.

#### Question 12

Draw a diagram to show that the energy flow in an ecosystem is governed by the law of conservation of energy.

Page 132

#### Question 1

Food chain begins with :

(a) Respiration  (b) Photosynthesis

(c) Decomposition   (d) Decay.

Photosynthesis

#### Question 2

The source of energy in an ecosystem is :

(a) Sun  (b) Decayed bodies

(c) Green plants  (d) Sugar.

Sun

#### Question 3

Energy enters in a food chain through :

(a) Primary consumers

(b) Secondary consumers

(c) Tertiary consumers

(d) Producers.

Producers

#### Question 4

The place of human being in food chain in an ecosystem is as a :

(a) Producer

(b) Consumer

(c) Decomposer

(d) Both (a) and (b).