KnowledgeBoat Logo
OPEN IN APP

Chapter 4

Ecosystems

Class 8 - Concise Biology Selina


Multiple Choice Questions

Question 1

The term “ecosystem” is derived from the Greek word "Oikos" meaning.

  1. Body weight
  2. Food
  3. House
  4. Size

Answer

House

Reason — The term "ecosystem" is derived from the Greek word "Oikos" which means a "house", a dwelling place with the inhabitants living together and interacting with each other and also with their physical environment in some definite ways.

Question 2

Rat in any food chain would occupy the position of

  1. Tertiary consumer
  2. Secondary consumer
  3. Primary consumer
  4. Producer

Answer

Primary Consumer

Reason — Rat is the primary consumer in the food chain. Rat is eaten by snake which is a secondary consumer of the food chain or ecosystem.

Question 3

Evergreen broad-leaved trees are characteristic of

  1. Tropical rain forests
  2. Temperate deciduous forests
  3. Coniferous forests
  4. All of the above types of forests.

Answer

Tropical rain forests

Reason — These forests grow in regions where year-round rainfall is high and steady and frost is rare. Evergreen trees have broad leaves to permit transpiration of surplus moisture.

Question 4

The number of steps in a food chain can never be more than

  1. Four
  2. Five
  3. Six
  4. Seven

Answer

Six

Reason — The number of steps in different food chains may vary from 2 to 5 and very rarely these can be 6 but never 7.

Short Answer Questions

Question 1

Mention if the following statements are true (T) or false (F):

(a) Snakes are primary consumers.

(b) Some humans are strictly primary consumers while others are secondary or tertiary consumers as well.

(c) No ecosystem can survive without light.

Answer

(a) False
Reason — Snakes are tertiary consumers.

(b) True

(c) True

Question 2

Match the following:

Column IColumn II.
GrassCarnivore
DeerDecomposers
CobraPrimary consumer
VultureAutotroph
MicrobesScavenger

Answer

Column IColumn II.
GrassAutotroph
DeerPrimary consumer
CobraCarnivore
VultureScavenger
MicrobesDecomposers

Question 3

Rewrite the following in their correct sequence in a food chain:

(a) Snake → Grasshopper → Grass → Frog

(b) Grass → Tiger → Deer

(c) Snake → Peacock → Rat → Wheat

Answer

(a) Grass → Grasshopper → Frog → Snake

(b) Grass → Deer → Tiger

(c) Wheat → Rat → Snake → Peacock

Long Answer Questions

Question 1

Differentiate among primary, secondary and tertiary consumers. Give one example each in a food chain.

Answer

Primary
Consumers
Secondary
Consumers
Tertiary
Consumers
The organisms that feed on primary producers.The organisms that feed on primary consumers.The animals that obtain their nutrition by eating primary consumers and secondary consumers.
HerbivoresEither carnivores or omnivoresCarnivores
Obtain energy from primary producersObtain energy from primary consumersObtain energy either from primary or secondary consumers
Examples — Grasshopper eating grassExamples — Frog eating GrasshopperExamples — Snake eating Frog.

Question 2

Define the terms (a) Flora and (b) Fauna.

Answer

Flora — Flora means the plants naturally occurring in a particular area. Some examples of flora include — grasslands, forests, flowering and non-flowering plants and trees.

Fauna — Fauna means the animals naturally living in that area. Some examples of fauna include — birds, animals, fish, insects, etc.

Question 3

List any three members each of the flora and fauna of tropical rain forests.

Answer

Three members of flora and fauna of tropical rain forests includes —

Flora — Evergreen trees, bamboos, ferns.

Fauna — Jungle cats, Leopards, monkeys.

Question 4

Define the following terms and give two examples in each case.

(a) Autotrophs

(b) Consumers

(c) Food chain

(d) Symbiosis

(e) Parasitism

(f) Predation

Answer

(a) Autotrophs — Autotrophs are organisms that produce their own food through Photosynthesis using simple substances like Carbon dioxide and Water in the presence of Sunlight. They come at the beginning of the food chain. Plants like grass, bushes, trees, etc. are examples of Autotrophs.

(b) Consumers — Consumers are organisms that depend on producers for food. Consumers can be primary, secondary, or tertiary. Primary consumers eat plants or plant products. Example: Grasshopper, Rat etc. Secondary consumers feed on primary consumers. Examples include Frog, Lizard, etc. Tertiary consumers feed on secondary consumers. Example : Eagle, Fox, etc.

(c) Food chain — Food chain is the linear sequence of organisms in which each organism eats the lower member and is itself eaten by the next higher member. Two examples of food chain are:

  1. Grass (Producer) → Goat (Primary Consumer) → Man (Secondary consumer)
  2. Grass (Producer) → Grasshopper (Primary Consumer) → Frog (Secondary Consumer) → Snake (Tertiary Consumer).

(d) Symbiosis — Symbiosis is defined as a relationship or interaction in which both the interacting species are benefitted. Two examples of Symbiotic relationship are:

  1. Plants need the help of animals for pollinating their flowers and dispersing their seeds. Animals are paid fees by the plants in the form of juicy and nutritious fruits.
  2. Lichens is another example in which a fungus and a photosynthetic alga live in a symbiotic relationship. Algae provides food and nourishment to fungus while fungus protects the algae from getting damaged by ultraviolet rays by forming a protective shell.

(e) Parasitism — In parasitism, one partner (the parasite) receives an advantage while the other (the host) is at a loss. The parasites harm the host reducing the revival, growth and reproduction of the host. Two examples of Parasitism are:

  1. The malarial parasite, Plasmodium needs an intermediate host (vector) — a mosquito to spread to other hosts.
  2. Human liver fluke depends on two intermediate hosts (a snail and a fish) to complete its life-cycle.

(f) Predation — When an animal catches and kills other organisms for food, it is termed Predation. All animals in food chain fall under the category of Predators regardless they be herbivores. Two examples of Predation are:

  1. Tiger hunting and eating deer.
  2. House sparrow eating any seed.
PrevNext