Chapter-1 Nutrition In Plants Test-1 - Class 7 MCQ

Green plants are called autotrophs since they synthesize their own food.

• Autotrophs: Green plants are classified as autotrophs because they have the ability to synthesize their own food.


• Photosynthesis: Autotrophs use a process called photosynthesis to convert sunlight, carbon dioxide, and water into glucose (a form of sugar) and oxygen.


• Chlorophyll: Green plants have a pigment called chlorophyll, which allows them to capture sunlight and use its energy for photosynthesis.


• Energy Source: By being autotrophs, green plants are self-sufficient when it comes to obtaining energy. They do not rely on consuming other organisms for food.


• Primary Producers: Autotrophs are considered primary producers in the food chain because they are the foundation of energy flow. They provide energy and nutrients to other organisms in the ecosystem.


• Importance: Green plants play a crucial role in maintaining the balance of ecosystems and the survival of other organisms. They produce oxygen, remove carbon dioxide from the atmosphere, and provide food and shelter for various animals.

Therefore, the correct answer is C: Autotrophs.

Food making process in plants is called as photosynthesis and synthesized food is stored as carbohydrates (glucose as well as starch).

The Pigment Absorbing Solar Energy in Photosynthesis is Chlorophyll
Explanation:
Photosynthesis is the process by which plants, algae, and some bacteria convert sunlight, water, and carbon dioxide into glucose and oxygen. The absorption of solar energy is a crucial step in this process, and it is facilitated by a pigment called chlorophyll.
Chlorophyll:
- Chlorophyll is a green pigment found in the chloroplasts of plant cells.
- It is responsible for absorbing light energy from the sun, which is essential for photosynthesis.
- There are several types of chlorophyll, including chlorophyll a and chlorophyll b, each with slightly different absorption spectra.
Function of Chlorophyll:
- Chlorophyll molecules are located within the thylakoid membranes of chloroplasts.
- When sunlight hits chlorophyll, the energy is absorbed by the pigment and transferred to the chloroplast, where it is used to produce ATP (adenosine triphosphate) and NADPH (nicotinamide adenine dinucleotide phosphate).
- These energy-rich molecules are then used to convert carbon dioxide and water into glucose through a series of chemical reactions.
Importance of Chlorophyll:
- Without chlorophyll, plants would be unable to carry out photosynthesis and produce the energy they need to survive.
- Chlorophyll is responsible for the green color of plants, as it reflects green light while absorbing other wavelengths.
- The absorption of solar energy by chlorophyll is a critical process for the maintenance of life on Earth, as it provides the foundation for the food chain and oxygen production.
In conclusion, chlorophyll is the pigment responsible for absorbing solar energy in photosynthesis. Without chlorophyll, plants would be unable to harness the power of sunlight and carry out the vital process of converting light energy into chemical energy.

Answer:
Photosynthesis:
During photosynthesis, plants use sunlight, water, and carbon dioxide to synthesize glucose (a sugar) and release oxygen gas as a byproduct. This process occurs in the chloroplasts of plant cells and is responsible for the production of food and oxygen in the environment.
Input and Output:
Plants take in carbon dioxide (CO2) and release oxygen (O2) gas during photosynthesis.
Explanation:
During photosynthesis, the following reactions occur:
1. Light-dependent reactions:
- Light energy is absorbed by chlorophyll in the chloroplasts.
- Water molecules (H2O) are split into hydrogen ions (H+), electrons (e-), and oxygen gas (O2) through a process called photolysis.
- Oxygen gas (O2) is released as a byproduct.
2. Light-independent reactions (Calvin cycle):
- Carbon dioxide (CO2) molecules are taken in from the atmosphere.
- Carbon dioxide (CO2) is converted into glucose (C6H12O6) through a series of chemical reactions.
- Glucose (C6H12O6) is used as energy by the plant or stored for later use.
Therefore, the correct answer is A: Carbon dioxide, Oxygen.

Parasite Plant with Yellow, Slender, and Branched Stem
The correct answer is A: Cuscuta.
Here is a detailed explanation:
Cuscuta:
- Cuscuta, commonly known as dodder, is a parasitic plant that belongs to the family Convolvulaceae.
- It is characterized by its yellow, slender, and branched stem.
- Cuscuta lacks chlorophyll and cannot carry out photosynthesis, so it relies on other plants for nutrients and water.
- The stem of Cuscuta wraps around the host plant, penetrating its tissues and absorbing nutrients.
- It can be found in various habitats, including fields, forests, and wetlands.
Pitcher Plant:
- Pitcher plants are carnivorous plants that have specialized leaves in the shape of a pitcher.
- They are not parasites and have green leaves with chlorophyll for photosynthesis.
- Pitcher plants use their unique leaves to attract, capture, and digest insects and other small prey.
- They are typically found in boggy or swampy areas.
Algae:
- Algae are simple, photosynthetic organisms that can be found in diverse environments, including freshwater, marine, and terrestrial habitats.
- They can vary in color, but yellow is not a common color for algae.
- Algae can be unicellular or multicellular and can range from microscopic to macroscopic in size.
Lichens:
- Lichens are a symbiotic relationship between a fungus and an alga or a cyanobacteria.
- They are not parasites and can be found growing on rocks, trees, and other surfaces.
- Lichens have a variety of colors and forms, but yellow is not specific to them.
To sum up, the correct answer is A: Cuscuta, which is a parasite plant with a yellow, slender, and branched stem. This plant relies on other plants for nutrients and water as it lacks chlorophyll and cannot carry out photosynthesis.

The Pores through Which Leaves Exchange Gases
The pores through which leaves exchange gases are called stomata. Stomata play a vital role in the process of photosynthesis and respiration in plants. Here is a detailed explanation:
1. What are stomata?
- Stomata are microscopic openings found on the surface of plant leaves, stems, and other organs.
- They consist of two specialized cells called guard cells that surround a pore-like opening.
2. Structure of stomata:
- Each stoma consists of a pore surrounded by two specialized kidney-shaped guard cells.
- The guard cells can change shape to open or close the pore.
3. Function of stomata:
- Stomata regulate the exchange of gases, including carbon dioxide (CO2) and oxygen (O2), between the plant and the environment.
- They are responsible for the intake of carbon dioxide needed for photosynthesis and the release of oxygen produced during photosynthesis.
- Stomata also control the loss of water vapor through a process called transpiration.
4. Process of gas exchange through stomata:
- During the day, when photosynthesis occurs, stomata open to allow the entry of carbon dioxide and the release of oxygen.
- At night or during periods of water stress, stomata close to reduce water loss through transpiration.
5. Factors influencing stomatal opening and closing:
- Stomatal opening and closing are regulated by various factors such as light intensity, carbon dioxide concentration, temperature, and water availability.
- When the plant has sufficient water and favorable environmental conditions, stomata open to facilitate gas exchange.
In conclusion, stomata are the pores through which leaves exchange gases. They play a crucial role in maintaining the balance of gases and water in plants, allowing for photosynthesis and respiration to occur efficiently.

Cuscuta is an example of a parasite.

Here is a detailed explanation:

• Parasite: Cuscuta is a parasitic plant that belongs to the family Cuscutaceae. It is commonly known as dodder or devil's hair. Parasites are organisms that depend on other organisms, known as hosts, for their survival and reproduction. Cuscuta is a holoparasite, meaning it completely lacks chlorophyll and cannot carry out photosynthesis. Instead, it relies on its host plant for nutrients and water.


• Mode of nutrition: As a parasite, Cuscuta obtains its nutrients by attaching itself to the stems of host plants using specialized structures called haustoria. The haustoria penetrate into the host's vascular system, allowing Cuscuta to extract water, sugars, and other nutrients directly from the host plant.


• Host range: Cuscuta has a wide range of host plants, including various agricultural crops, ornamental plants, and wild species. Once attached to a host, Cuscuta forms a network of tangled, yellowish or orange stems that can cover and smother the host plant.


• Reproductive strategy: Cuscuta produces small, white or pink flowers that are pollinated by insects. After pollination, it forms small capsules containing numerous seeds. These seeds are dispersed to new locations and can germinate when they come into contact with a suitable host plant.


• Ecological impact: While Cuscuta can negatively impact crop yields and reduce the vigor of host plants, it also plays a role in ecological interactions. It can serve as a food source for certain insects and provides shelter for beneficial organisms.

Overall, Cuscuta serves as a prime example of a parasitic plant, showcasing its unique adaptation and dependency on host plants for survival.

The plants which traps and feeds on insects is:
There are several plants that have evolved to trap and feed on insects as a source of nutrients. One such example is the pitcher plant. Here is a detailed explanation:
Pitcher Plant:
- Pitcher plants are carnivorous plants that have specialized leaves shaped like a pitcher or a cup.
- The leaves of the pitcher plant are modified to form a deep cavity with a slippery wax-like coating on the inner surface.
- The pitcher plant lures insects into the cavity through nectar secretions or attractive colors on the rim of the pitcher.
- Once inside, the insects become trapped due to the slippery walls and downward-pointing hairs that prevent them from climbing out.
- The pitcher plant secretes digestive enzymes into the cavity, which help break down the insect's body.
- The nutrients released from the decomposed insects are then absorbed by the plant to supplement its nutrition, especially in nitrogen-deficient environments.
- Some species of pitcher plants can even digest small vertebrates like frogs or lizards.
Other plants that also trap and feed on insects include:
Cuscuta:
- Cuscuta, also known as the dodder plant, is a parasitic plant that does not have chlorophyll.
- It attaches itself to a host plant and derives nutrients by piercing the host's stem and absorbing its sap.
- While it doesn't directly trap insects, it depends on other plants for its nutrition.
China Rose:
- The China rose is not a carnivorous plant and does not trap insects for feeding.
Rose:
- The rose is also not a carnivorous plant and does not trap insects for feeding.
In conclusion, the correct answer is C: Pitcher plant. It is a fascinating example of a plant that has evolved to trap and feed on insects as a means of supplementing its nutrition.

Explanation:
Photosynthesis:
- Photosynthesis is the process by which plants, algae, and some bacteria convert sunlight, carbon dioxide, and water into glucose and oxygen.
- It takes place in the chloroplasts of plant cells, specifically in the thylakoid membrane.
- The process can be divided into two stages: the light-dependent reactions and the light-independent reactions (Calvin cycle).
Carbon Dioxide in Photosynthesis:
- During the light-dependent reactions, light energy is used to split water molecules, releasing oxygen and generating ATP (energy) and NADPH (a high-energy electron carrier).
- Carbon dioxide is not directly involved in the light-dependent reactions.
- In the light-independent reactions (Calvin cycle), carbon dioxide is used to synthesize glucose.
- The Calvin cycle takes place in the stroma of the chloroplasts.
- During the Calvin cycle, carbon dioxide is converted into sugar molecules using the energy stored in ATP and NADPH.
Carbon Dioxide Release:
- Carbon dioxide is released during cellular respiration, which is the process by which organisms break down glucose to release energy.
- In this process, glucose and oxygen are consumed, and carbon dioxide and water are produced.
- Carbon dioxide is also released when organic matter, such as plant material, decomposes or when fossil fuels are burned.
Conclusion:
- Carbon dioxide is not directly released during photosynthesis.
- Instead, it is consumed during the light-independent reactions (Calvin cycle) to synthesize glucose.
- The release of carbon dioxide occurs during cellular respiration and other processes such as decomposition and combustion.

False: Plants that synthesize their own food are not called saprotrophs.

Saprotrophs are organisms that obtain their nutrition by decomposing dead organic matter. They are commonly found in fungi and bacteria. Plants, on the other hand, are autotrophs, which means they can produce their own food through photosynthesis.

Here are the key points to support the statement:

- Plants that synthesize their own food are called autotrophs.
- Autotrophs use photosynthesis to convert sunlight, carbon dioxide, and water into glucose and oxygen.
- Saprotrophs, such as fungi and bacteria, obtain their nutrition by decomposing dead organic matter.
- Saprotrophs play an important role in the decomposition and recycling of nutrients in ecosystems.
- While plants can obtain nutrients from the soil, they rely on photosynthesis as their primary source of energy and food production.

Therefore, it is incorrect to say that plants which synthesize their own food are called saprotrophs.