Grade 9: Nature and Environment

Nature and Environment

Very short answer type questions.
1.      What are decomposers?
Decomposers are organisms that convert complex organic matter in dead bodies into simple inorganic substances.
2.      What factors determine the types of organisms in an area?
Climate, soil, water, and availability of food are the factors that determine the type of organism of an area.
3.      Define commensalism.
A relationship where one organism benefits while the other is neither harmed nor benefited is commensalism.
4.      Define parasite and host.
Parasite: An organism that lives on or inside another organism and derives nutrients.
Host: The organism that provides food and shelter to the parasite.
5.      What is mutualism?
Mutualism is a relationship between two organisms where both organisms benefit from each other.
6.      Name two endoparasites found in man.
Two endoparasites found in man are: Tapeworm and roundworm.
7.      What are the components of ecosystem?
The components of ecosystem are: Biotic (living organisms) and abiotic (non-living factors like soil, water, air).
8.      Name the bacteria that live in association with the legume plants.
Rhizobium is the bacteria that live in association with the legume plants.
 Short answer type questions.
1.      What are the reasons for the difference in environment of different places?
Following are the reasons for the difference in environment of different places.

• Differences in climate  e.g., deserts vs. rainforests.

• Variation in topography and altitude (mountains, plains)

• Differences in soil types and nutrient availability.

• Variation in latitude (distance from equator) and exposure to sunlight.

• Influence of water bodies (coastal vs. inland) and ocean currents.

• Human activities (urbanization, agriculture, deforestation) altering local environments.

 
2.      What will happen if all the lions in a forest ecosystem are removed or killed?
If all lions in a forest ecosystem are removed then, Prey populations (e.g., deer, antelope) would likely increase, causing overgrazing. Overgrazing would reduce plant biomass, harming plant diversity and regeneration. Secondary effects include decline of species that depend on certain plants, soil erosion, and altered ecosystem balance.
3.      Write any two differences between abiotic and biotic components.
Two differences between abiotic and biotic components
Abiotic: nonliving (temperature, water, sunlight, soil).
Biotic: living (plants, animals, microbes).

• Abiotic factors influence organisms but do not grow or reproduce;

• biotic components grow, reproduce, and interact (competition, predation).

 
4.      Write any two differences between food chain and food web.
Two differences between food chain and food web
Food chain: a single linear sequence of who eats whom (simple path).
Food web: many interconnected food chains showing multiple feeding relationships.

• Food chain shows a single energy flow path;

• food web shows multiple energy pathways and greater ecosystem complexity/stability.

 
5.      Write any two differences between mutualism and commensalism.
Two differences between mutualism and commensalism
Mutualism: both species benefit (e.g., bees and flowering plants).
Commensalism: one species benefits, the other is neither helped nor harmed (e.g., barnacles on a whale).

• Mutualism often involves obligate or facultative close interactions affecting survival; commensalism typically has one-sided benefit without major impact on the host.

 
6.      How does rhizobium help legume plants?
Rhizobium bacteria fix atmospheric nitrogen (N2) into ammonia/nitrate usable by the plant through nodules on roots, supplying essential nitrogen for growth and protein synthesis. In return, the plant supplies carbohydrates to the bacteria.
 
7.      Why are plants called producers?
Plants synthesize organic food molecules (glucose) from inorganic inputs (carbon dioxide and water) using sunlight through photosynthesis, forming the base of food chains and supplying energy to all other organisms. So, they are called producers.
 
8.      Write any two advantages of decomposers to the environment.
Two advantages of decomposers to the environment

• They recycle nutrients by breaking down dead organisms and waste into inorganic forms (like minerals and nitrates) that plants can absorb, maintaining soil fertility.

• They clean up organic waste, reducing buildup of dead matter and preventing the spread of disease by decomposing carcasses and plant litter.

Long answer type questions:
1.      Farmers suffered from snakes campaigned for killing snakes. Was it appropriate from the point of view of balance ecosystem. Explain with reason.
No, it was not appropriate from the point of view of balance ecosystem to kill snakes because it disrupts the food web. Snakes control rodent populations (mice/rats). Without snakes, rodent numbers rise, causing crop damage and disease spread. This trophic imbalance can cascade to plant loss, increased pesticide use, and long‑term harm to the ecosystem and human livelihoods.
2.      If the number of tertiary consumers is increased more, then it is necessary. It causes imbalance in ecosystem, how?
If the number of tertiary consumers is increased more, then it is necessary then they can overconsume secondary consumers, causing their populations to decrease leading to prey shortages for top predators, causing starvation or migration. This disturb the trophic level and hence the whole ecosystem will be changed.
 
3.      How does decomposer help make soil fertile? Explain in brief.
Decomposers break down dead plants, animals, and waste into simpler inorganic nutrients (minerals, nitrates, phosphates). These released nutrients enrich the soil, making them available for plant uptake and improving soil structure and fertility.
Thus, decomposer helps make soil fertile.
4.      Construct a food chain comprising snake, mice, hawk and plants.

                                        🌱➡️🐭➡️🐍➡️🦅

 

5.      What will happen if all the phytoplanktons are eliminated from a pond?
If all phytoplankton are eliminated from a pond then Primary production would collapse and there won't be any organism to carry out photosynthesis. Then, Herbivorous zooplankton and small fish would starve, causing food web collapse. Oxygen levels would drop due to low photosynthesis, leading to hypoxia and mass die‑offs. Consequently, all biodiversity and ecosystem functioning would collapse.
6.      What will happen if all deers are removed from the forest.
·        If all deer are removed from the forest then Plant species that deer browsed may increase, changing plant community composition. Predators that rely on deer (wolves, big cats) would decline or switch prey, stressing other species. Reduced grazing can alter habitat structure, affecting other herbivores and seed dispersal. Long‑term shifts in vegetation and associated fauna could reduce biodiversity.
7.      How does deforestation affect the land ecosystem? Give an example.
Deforestation removes trees and plants that provide habitat, food, and shelter, causing loss of biodiversity and species displacement or extinction. It disrupts soil structure and nutrient cycles, increasing erosion, reducing soil fertility, and raising landslide risk.It alters local climate and hydrology. It increases atmospheric carbon dioxide (reduced carbon sequestration), contributing to climate change.
Example: Clearing tropical rainforest for cattle ranching destroys habitat for tree‑dependent species like monkeys, orangutan, etc.
 
8.      Flow of energy in the food chain is unidirectional. Explain.
Flow of energy in the food chain is unidirectional. Energy enters ecosystems from an external source (mainly the sun). Producers convert solar energy into chemical energy via photosynthesis. Consumers obtain that stored chemical energy by eating producers or other consumers. At each transfer, a large fraction of energy is lost as heat through respiration, movement, growth and maintenance. Because energy is dissipated as heat and cannot be converted back into high‑quality biological energy within the system, it cannot be recycled the way nutrients are. That means energy flows one way:
Decomposers break down dead organisms and return nutrients to the soil (nutrient cycling), but they do not return usable energy back up the chain — they release it as heat.
9.      Answer the questions based on the following diagram of terrestrial ecosystem.

 

a) Identify producer and consumer.
Green plants are producers while the herbivores and carnivores are consumer.
b) Which one should be the largest in number in order to balance the ecosystem? Explain
Producers should be largest number in order to balance the ecosystem. It supports all the consumers directly or indirectly.
c) How does producer obtain nutrients? Explain.
Producers obtained nutrients by the following ways.
They trap solar energy of the sun, their roots absorb nutrient and water from the soil and carbon dioxide from the atmosphere.
CO₂ and H₂O are reacted in the chloroplast region to generate glucose which is utilized for growth and development of the producers.

10.   Answer the questions based on the following diagram of a pond ecosystem.

 

a) Identify the producers and consumers.

The producers in this ecosystem are phytoplankton, algae and aquatic plants like Lemna, hydrilla, etc. 

b) Which one should be the largest in number in order to balance ecosystem?

Producers should be the largest in number in order to balance ecosystem.

c) What will happen if there is no producers in this ecosystem?

If there is no producers in pond ecosystem, then the whole of the ecosystem will collapse. As producer are the main biotic factor which generates food from inorganic substance. All the consumers directly or indirectly depends on producer for their nutrients. Due to the lack of producers, all the consumers will finally die.

2.      Given below is an example of food chain.

GrassàGrasshopperàFrogàSnakeàHawk

What will happen to the members at different tropic level of this food chain, if all the frogs are removed? Explain.

In the above food chain, frogs are removed, this will increase in the number of grasshopper, because their main predator is frog which is not existing. This will decrease in the quantity of grass due to overgrazing.

Snakes depend on frog food, therefore they have to struggle more for food and most of them will die due to starvation.

The population of hawk will also reduce because they won't get sufficient amount of snakes.

3.      The diagram given alongside is a part of food chain. On the basis of it answer the following questions.

 

a) Identify the producers, primary consumers, secondary consumers and top consumers.

The producers are grasses, primary consumer is rabbit, secondary consumer is jackal and top consumer is tiger.

b) Give two reasons why the population of jackal would increase if all the tigers are killed.

Two reasons why Jackal Population Would Increase if All Tigers Are Killed

    1. No Predation Pressure: Tigers prey on jackals. Without tigers, jackals are fearless allowing their population to grow.

    2.      More Availability of food: Tigers also eat rabbits. With tigers gone, more rabbits are available, giving jackals more food to survive and reproduce.

4.      Apart from plants and animals, microbes form a permanent biotic component in an ecosystem. While plants have been referred to as autotrophs and animals as heterotrophs, what are microbes referred as? How do these microbes fulfil their energy requirement? Explain with example.

Microbes are referred to as saprotrophs or decomposers in an ecosystem. They fulfill their energy requirement by breaking down dead organic matter and absorbing nutrients through external digestion.

• Rhizopus Fungi grows on bread or decaying leaves, secretes enzymes to digest starch externally, and absorbs sugars.
• Nitrosomonas Bacteria converts ammonia into nitrites in soil — a process called nitrification, which helps in nitrogen cycling and provides energy to the bacteria.