Frank Brothers Solutions for ICSE Class 9 Biology Chapter 12 Interaction Between Biotic And Abiotic Factors In An Ecosystem

PAGE NO: 99

Question 1:
Answer:
Producers
Producers are organisms like green plants that can prepare their own food using sunlight. They form the base of every ecosystem by providing energy for all other living things.
Teacher's Tip: Remember, "Producers Produce" their own food.
Exam Tip: Always mention "green plants" as the primary example of producers.

Question 2:
Answer:
Consumers
Consumers are living beings that cannot make their own food and must eat plants or other animals. This group includes everything from tiny insects to large humans.
Teacher's Tip: Think of "Consumers" as "Customers" who buy (eat) food from the producers.
Exam Tip: Differentiate between herbivores, carnivores, and omnivores when discussing consumers.

Question 3:
Answer:
The climatic factors affecting ecosystem are sunlight, temperature, humidity, rainfall and wind.
These non-living factors determine which types of plants and animals can survive in a specific area. For example, a cactus thrives in high heat, while a polar bear needs freezing temperatures.
Teacher's Tip: Use the acronym "W.R.I.S.T" (Wind, Rainfall, Intensity of light, Sunlight, Temperature).
Exam Tip: List at least four factors to ensure you get full credit for climatic components.

Question 4:
Answer:
Low and high temperatures restrict the growth of plants and existence of animal species. Changes in temperature patterns will impact plant life which in turn will influence the animal life, since animals depend directly or indirectly on it for food. During extreme cold and hot conditions, animals either migrate to favourable places, some may hibernate or some may aestivate.
Animals have clever ways to survive when the weather becomes too harsh to handle. Hibernation is a deep sleep during winter, while aestivation is a similar rest taken during hot summer months.
Teacher's Tip: "H" for Hibernation happens in the "H"arsh cold.
Exam Tip: Clearly define the terms "migration," "hibernation," and "aestivation" to show a deep understanding.

Question 5:
Answer:
Consumers which eat only plants are called consumers of the first order. Consumers that eat herbivores like deer, goats, grasshoppers, etc. are called consumers of the second order.
First-order consumers are also known as herbivores because they only eat greenery. Second-order consumers are carnivores that hunt and eat those herbivores for energy.
Teacher's Tip: Think of a ladder; the plant is the ground, and the herbivore is the first step up.
Exam Tip: Always provide examples like "deer" for first-order and "lion" for second-order to clarify your answer.

Question 6:
Answer:
Deserts have scanty water, either because there is little rainfall, or because the water evaporates very fast in deserts. Desert species are adapted to less amounts of water and they are capable of surviving for long periods of time in the scarcity of water. The growth of plants and animals and their vital functions are dependent on water intake. Hence water is a vital limiting factor in deserts due to the scant availability of this important resource.
Because water is so rare, desert plants often have deep roots or thick skins to store every drop. Animals in these areas have also evolved to go long distances without needing a drink.
Teacher's Tip: A "Limiting Factor" is like a "Speed Limit" that controls how much life can grow.
Exam Tip: Use the term "limiting factor" when explaining why certain environments have fewer species.

Question 7:
Answer:
Abiotic components
These are the non-living factors affecting the organisms of an ecosystem.
E.g. - Water, sunlight, temperature etc.
Biotic components
These are the living organisms present in an ecosystem.
E.g. - Plants, animals, microbes etc.
Biotic factors are the "living" parts like your pets and garden plants. Abiotic factors are the "non-living" parts like the soil and the weather that support life.
Teacher's Tip: "Bio" means life, so Biotic means living!
Exam Tip: When comparing, always use examples to make the difference between living and non-living clear.

Question 8:
Answer:
Primary producers
These are autotrophic plants.
They use sun’s energy, water, air and chlorophyll to produce their own food.
Example - Green plants
Secondary producers
These are heterotrophic organisms.
They consume food and produce new types of organic substances while digesting their food.
Example - Fungi, animals
Primary producers are the true creators of food using the power of the sun. Secondary producers take that food and transform it into different forms of energy through digestion.
Teacher's Tip: "Primary" means first, so they are the very first link in the energy chain.
Exam Tip: Be careful not to confuse secondary producers with consumers; secondary producers focus on organic synthesis.

Question 9:
Answer:
Vital atmospheric gases are oxygen, carbon dioxide and nitrogen. Oxygen availability seldom becomes a limiting factor for land animals unless they live in soil or invade high altitudes. Plants release oxygen into the air which is used by animals for respiration. During respiration, animals release carbon dioxide which is required by plants for photosynthesis. Nitrogen is an essential gas which is vital for the growth and sustenance of organisms.
These gases create a perfect cycle where plants and animals help each other breathe and grow. Without this delicate balance of oxygen and carbon dioxide, life on Earth would come to a stop.
Teacher's Tip: Plants "inhale" $CO_{2}$ and "exhale" $O_{2}$, which is the opposite of what we do.
Exam Tip: Mention Nitrogen's role in "growth and sustenance" to provide a complete answer about atmospheric gases.

Question 10:
Answer:
In a natural ecosystem, green plants capture solar energy and convert it into chemical forms. The energy is then passed onto herbivores when they feed on green plants. From herbivores, the energy moves into carnivores that eat them. Some animals like lion and vultures are not eaten by other organisms. All the organisms ultimately pass on energy to the decomposers. Energy thus flows continuously through the ecosystem from plant to animals and from prey to predator.
This flow of energy ensures that the power captured from the sun eventually reaches every living thing. Decomposers are the final step, breaking down remains and returning nutrients to the soil.
Teacher's Tip: Follow the sun! Sunlight is the "battery charger" for the entire planet.
Exam Tip: Draw a simple flow chart starting from the Sun to represent this energy flow clearly.

Question 11:
Answer:
Energy passes through the ecosystem in a one-way path. Energy goes through each trophic level, one at a time. As it goes from one level to another, it is lost due to metabolism and in the form of heat. For example - The energy ingested by producers is used by the producers for carrying out various life activities and some amount of energy is lost as heat, so that the entire energy does not pass completely to the consumers. The energy lost as heat cannot be used anymore.
Because energy is lost as heat at every step, there is always less energy available for animals higher up the food chain. This is why you see many more plants and insects than you do lions or hawks.
Teacher's Tip: Energy is like a "leaky bucket"; some always drips out (as heat) before it reaches the next person.
Exam Tip: Use the phrase "unidirectional flow" to describe how energy moves in an ecosystem.

Question 12:
Answer:
The transfer of energy from autotrophs through a series of organisms that consume and are consumed is known as a food chain.
A food chain shows exactly "who eats whom" in a straight line. It starts with a plant and ends with a top predator.
Teacher's Tip: Think of a chain; every link is an animal or plant connected by what they eat.
Exam Tip: Always start your food chain with an autotroph (producer) to get full marks.

Question 13:
Answer:
The types of food chain are:
1. Grazing food chain
2. Detritus food chain
3. Auxiliary food chain
(Write any two)
The grazing food chain starts with living plants, while the detritus chain starts with dead organic matter. Knowing these types helps us understand how energy is recycled in different ways.
Teacher's Tip: "Grazing" is for green plants, and "Detritus" is for decaying stuff.
Exam Tip: If asked for types, naming two correctly with brief descriptions is usually enough for full points.

Question 14:
Answer:
Individual food chains interconnected in a complex way is called food web.
In nature, animals rarely eat just one thing, so many food chains overlap. A food web is a much more realistic picture of how life works in the wild.
Teacher's Tip: A "Web" is messy and tangled, just like how many animals eat many different things.
Exam Tip: Define a food web as a "network of food chains" for a perfect technical definition.

Question 15:
Answer:
An energy pyramid is a graphical representation of the flow of energy from the producers through the various consumers. It shows the amount of energy available and the loss of useful energy at each step of the food chain in an ecosystem.
This pyramid shape tells us that there is a massive amount of energy at the bottom and very little at the top. It visually explains why ecosystems can only support a small number of top predators.
Teacher's Tip: The pyramid is big at the bottom because plants have the most energy.
Exam Tip: Label the different layers of the pyramid (Producers, Primary Consumers, etc.) in your diagrams.

Question 16:
Answer:
As the energy gets transferred from lower trophic level to the higher one, there is a loss of large amount of energy due to metabolism and as heat. As a result very little energy (i.e. 10%) gets transferred to the next level. So the trophic level at the base has maximum energy and that at the top has the least amount of energy. Hence energy pyramid is broader at the base and narrower at the top.
Only about one-tenth of the energy from one level makes it to the next one. This "10% Rule" is why food chains usually don't have more than four or five links.
Teacher's Tip: Imagine a $100 bill; if you only get 10% each time, it quickly turns into $10, then $1, then pennies!
Exam Tip: Explicitly mention the "10% Law" to explain the narrowing shape of the energy pyramid.

Question 17:
Answer:
(i) (a) unidirectional
(ii) (d) producers and consumers
(iii) (d) all the above
(iv) (a) photosynthesis
(v) (b) herbivores
(vi) (b) bacteria, fungi, etc.
(vii) (b) Communities and their physical environment
(viii) (d) solar energy
(ix) (d) biotic and abiotic
(x) (d) high temperature and high rain
These multiple-choice answers summarize the most important facts about ecosystems. Reviewing them helps reinforce your knowledge of terms like "unidirectional" and "biotic."
Teacher's Tip: Read all the options carefully, especially when "all of the above" is a choice.
Exam Tip: Write the letter of the choice AND the words next to it to ensure your answer is clear.