1. Choose the correct option.
2. In the process of photosynthesis, the gas given out by Green Leaves is _______
3. Oxygen (ii)carbon dioxide (iii) nitrogen (iv)ozone.

   Answer. Oxygen

• To test the presence of starch using iodine, the green leaf is first boiled in alcohol to

(i) remove starch (ii) dissolve chlorophyll (iii) make the leaf soft (iv) make the leaf transparent

   Answer. dissolve chlorophyll

• Which of the following is an insectivorous plant?

(i)Cuscuta (ii) Croton (iii) Lichen (iv) Sundew

 Answer. Sundew

• The mode of nutrition shown by coral root is ___________
• Myco – heterotrophic (ii) parasitic (iii) Saprotrophic (iv) autotrophic

Answer. Myco – heterotrophic

• Assertion – Reasoning questions.

For question numbers (i) and (ii), two statements are given and labeled as Assertion (A) and the other labeled as Reason (R). Select the correct answer to these questions from the codes (a), (b),(c), and (d) as given below.

• Both Assertation (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertation (A)
• Both Assertation (A) and Reason (R) are true and Reason (R) is not the correct explanation of the Assertation (A)
• Assertation (A) is true but Reason (R) is false.
• Assertation (A) is false but Reason (R) is true.
• Assertation (A) All plants are not autotrophic.

Reason (R) Insectivorous plants cannot synthesise their food.

• Assertation (A) Plants convert light energy into chemical energy during the process of photosynthesis.

Reason (R)sugar produced from photosynthesis by plants is used by human beings as a source of energy

(i) The correct answer is (b) Both Assertion (A) and Reason (R) are true and Reason (R) is not the correct explanation of the Assertion (A).

Explanation:

Assertion (A): All plants are not autotrophic.

Reason (R): Insectivorous plants cannot synthesize their food.

Both the assertion and reason are true. However, the reason provided doesn’t directly explain why all plants are not autotrophic. Insectivorous plants are indeed not completely autotrophic because they obtain some nutrients from insects, but this does not necessarily mean all plants are not autotrophic. Therefore, the reason does not directly explain the assertion.

(ii) The correct answer is (a) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of the Assertion (A).

Explanation:

Assertion (A): Plants convert light energy into chemical energy during the process of photosynthesis.

Reason (R): Sugar produced from photosynthesis by plants is used by human beings as a source of energy.

Both the assertion and reason are true, and the reason provided correctly explains why plants convert light energy into chemical energy during photosynthesis. The chemical energy stored in sugars produced during photosynthesis serves as a source of energy for various organisms, including humans. Therefore, the reason explains the assertion.

Q3. Answer the following questions in one sentence.

1. Organism on which a parasite lives.

Answer. Parasites can live in or on various organisms across different kingdoms of life, including humans, mammals, birds, fish, insects, plants, and others.

b. Organisms that break down organic matter to release nutrients.

Answer. Organisms such as bacteria, fungi, and certain invertebrates like earthworms break down organic matter through processes like decomposition, releasing nutrients into the environment.

c. Modified succulent roots in parasitic plants.

Answer. Modified succulent roots in parasitic plants, such as dodder and mistletoe, serve to penetrate the host plant and extract water and nutrients for the parasite’s survival.

d. A relationship between two organisms in which both are benefited.

Answer. Symbiosis is a mutually beneficial relationship between two species of organisms.

e. Cells that regulate the opening and closing of stomata.

Answer. Cells that regulate the opening and closing of stomata guard cells.

Q4. Answer the following questions in 2-3 sentences.

a. Explain the term autotrophic nutrition.

Answer. Autotrophic nutrition is a process whereby an organism synthesizes its own food utilizing basic inorganic substances such as water, mineral salts, and carbon dioxide in the presence of sunlight; the term “autotrophic” stems from the fusion of “auto,” signifying self, and “trophic,” indicating nutrition.

b. What is crop rotation?

Answer.

Crop rotation is a beneficial agricultural technique involving the cultivation of a variety of crops in sequential seasons within the same area. This method aims to prevent soil depletion by ensuring that different sets of nutrients are utilized across different planting cycles.

c. What is lichen?

Answer.

Lichen is a symbiotic organism composed of a fungus and an alga or cyanobacterium living together in a mutually beneficial relationship. The fungus provides structural support and protection, while the alga or cyanobacterium photosynthesizes, producing food for both partners. Lichen can be found in various environments worldwide, ranging from rocky surfaces to tree bark, and it plays important roles in ecological processes such as soil formation and nutrient cycling.

5. Answer the following questions in 3 -4 sentences.

a. Explain total parasites with an example.

Answer, Obligate parasites rely completely on the host for sustenance, including both food and water. An illustrative instance of such a parasitic plant is Cuscuta, which solely depends on the host for its nutritional and water needs. Conversely, facultative parasites only partially rely on the host, seeking either water or nutrients from it, but not both simultaneously.

b. What are decomposers? Explain the two of decomposers with examples.

Answer. Decomposers are microorganisms responsible for breaking down and converting deceased plant and animal matter into humus. Among the well-known decomposers are bacteria and fungi, which play vital roles in the decomposition process within ecosystems.

Notes 

Mode of Nutrition:

Modes of nutrition refer to the various ways organisms obtain and utilize nutrients for their survival and growth. This includes autotrophic nutrition, where organisms produce their food through processes like photosynthesis, and heterotrophic nutrition, where organisms consume organic matter from other sources for nourishment. These modes of nutrition are essential for sustaining life and maintaining biological processes within ecosystems.

Nutrition:

Nutrition is the process by which living organisms acquire and utilize essential substances necessary for their growth, development, and overall well-being. It involves the intake, digestion, absorption, and utilization of nutrients such as carbohydrates, proteins, fats, vitamins, and minerals, which provide energy and support various physiological functions within the body. Proper nutrition is fundamental for maintaining health and optimizing biological functions across all levels of life, from individual cells to entire organisms.

Nutrients:

Nutrients refer to the essential elements present in our diet, including carbohydrates, vitamins, minerals, fats, and more. These components are vital for the survival of living organisms. Unlike plants, which synthesize their own food, animals and humans rely on external sources for their nutritional needs.

Autotrophic Nutrition: Autotrophic nutrition is a process through which certain organisms, like plants, produce their own food using sunlight, water, and carbon dioxide. In simpler terms, it’s like plants making their meals from sunlight and air. This process is important because it forms the basis of the food chain, providing energy and nutrients for other living things. So, autotrophic nutrition is like plants being able to cook up their own meals using sunlight and simple ingredients from the air and soil.

Chlorophyll:

Chlorophyll is a green pigment found in the chloroplasts of plant cells and some other photosynthetic organisms like algae and cyanobacteria. It plays a crucial role in photosynthesis, the process by which plants convert light energy into chemical energy, ultimately producing glucose (sugar) from carbon dioxide and water. Chlorophyll absorbs sunlight, particularly in the blue and red regions of the electromagnetic spectrum, while reflecting green light, which gives plants their characteristic green color. In essence, chlorophyll acts as a catalyst for photosynthesis, capturing light energy to fuel the synthesis of organic compounds essential for plant growth and survival.

Photosynthesis:

Photosynthesis is a biological process found in plants, algae, and some bacteria, where light energy is converted into chemical energy. This process occurs primarily in the chloroplasts of plant cells. During photosynthesis, carbon dioxide from the air and water from the soil are combined in the presence of sunlight to produce glucose (a type of sugar) and oxygen. The equation representing photosynthesis is

This reaction is crucial for the survival of life on Earth as it provides the oxygen we breathe and serves as the primary source of energy for plants and other organisms in the food chain.

The materials required for photosynthesis include:

Carbon dioxide (CO2): Plants absorb carbon dioxide from the air through small pores called stomata, primarily located on the underside of their leaves.

Water (H2O): Plants absorb water from the soil through their roots. Water is then transported through the plant’s vascular system to the leaves, where it is used in photosynthesis.

Light energy: Sunlight serves as the primary source of energy for photosynthesis. Plants capture light energy using pigments such as chlorophyll, located in the chloroplasts of their cells.

These three materials—carbon dioxide, water, and light energy—are essential for plants to carry out photosynthesis, enabling them to produce glucose and oxygen, which are vital for their growth and survival.

Stomata: Stomata are tiny pores found primarily on the underside of plant leaves, though they can also occur on stems and other plant parts. These microscopic openings are surrounded by specialized cells known as guard cells. Stomata regulate the exchange of gases, such as oxygen and carbon dioxide, between the plant and its environment. Additionally, they play a crucial role in the plant’s water regulation by controlling the loss of water vapor through transpiration. Stomata open and close in response to environmental factors such as light intensity, humidity, and carbon dioxide levels, helping to optimize photosynthesis and maintain the plant’s overall health and hydration.

Products of photosynthesis:

The products of photosynthesis are glucose (a type of sugar) and oxygen. During photosynthesis, plants use carbon dioxide, water, and sunlight to produce glucose and release oxygen as a byproduct. Glucose serves as the primary energy source for plants, while oxygen is released into the atmosphere, which is essential for the survival of all aerobic organisms, including humans and animals.

Importance of photosynthesis:

Oxygen Production: Photosynthesis produces oxygen as a byproduct, which is essential for the survival of aerobic organisms, including humans and animals. It replenishes the oxygen in the atmosphere, allowing us to breathe.

Food Production: Photosynthesis is the primary process by which plants produce food in the form of glucose. This glucose serves as the basic energy source for plants, fueling their growth, development, and reproduction.

Carbon Dioxide Reduction: Photosynthesis removes carbon dioxide from the atmosphere, helping to mitigate the greenhouse effect and climate change by absorbing excess carbon dioxide from the air.

Overall, photosynthesis is fundamental for maintaining the balance of oxygen and carbon dioxide in the atmosphere, providing food for organisms, and sustaining life on Earth.

Heterotrophic Nutrition in Plants:

Heterotrophic nutrition in plants refers to the process where plants obtain organic nutrients from external sources rather than producing their own through photosynthesis. This occurs primarily in parasitic and carnivorous plants, as well as in mycoheterotrophy plants that rely on fungi for nutrients. Unlike autotrophic plants, which synthesize their own food using sunlight, heterotrophic plants rely on other organisms for their nutritional needs

Parasitic plants:

Parasitic plants are organisms that rely on other plants for their nutrients and survival. They attach themselves to a host plant and extract water, minerals, and organic compounds from it, often harming the host in the process. These plants have specialized structures, such as haustoria, which penetrate the host’s tissues to access its resources. Examples of parasitic plants include dodder, mistletoe, and certain species of orchids.

Partial parasites:

Partial parasites, also known as hemiparasites, are plants that obtain some of their nutrients from a host plant but can also photosynthesize to produce their own food. Unlike full parasites, which rely entirely on their host for nutrients, partial parasites can supplement their diet through photosynthesis. However, they still rely on their host for water, minerals, and other essential nutrients, establishing a partial dependence on the host for their survival. Examples of partial parasites include certain species of mistletoe and Indian paintbrush.

Total parasites:

Total parasites, also known as holoparasites, are plants that completely depend on a host organism for their nutrients and survival. Unlike partial parasites, which can photosynthesize to some extent, total parasites lack chlorophyll and cannot produce their own food through photosynthesis. Instead, they rely entirely on their host plant for water, minerals, and organic nutrients. Total parasites often have specialized structures, such as haustoria, which penetrate the host’s tissues to extract nutrients. Examples of total parasites include broomrape and corpse flower (Rafflesia).

Insectivorous plants: Insectivorous plants are organisms that have adapted to supplement their nutritional needs by capturing and digesting insects and other small prey. These plants typically grow in nutrient-poor environments, such as bogs or acidic soils, where they struggle to obtain essential nutrients like nitrogen and phosphorus. To compensate for this deficiency, insectivorous plants have evolved specialized structures, such as pitcher traps, sticky glands, or snap traps, to capture their prey. Once caught, the insects are broken down by enzymes secreted by the plant, allowing the plant to absorb the nutrients released. Examples of insectivorous plants include Venus flytraps, pitcher plants, and sundews.

Pitcher Plant: The pitcher plant is a type of carnivorous plant known for its modified leaves that form a pitcher-like structure, often filled with liquid. This plant attracts and captures insects and other small organisms as a source of nutrients. The pitcher plant lures its prey with nectar or colorful markings on its “lid” or rim. Once insects enter the pitcher, downward-pointing hairs prevent them from escaping, causing them to fall into the liquid-filled pit where they drown. Enzymes produced by the plant break down the trapped prey into nutrients that the plant can absorb, helping it thrive in nutrient-poor environments. This unique adaptation allows pitcher plants to supplement their nutritional needs by consuming insects.

Sundew Plant: The sundew plant is a type of carnivorous plant characterized by its sticky, glandular hairs that cover its leaves. These hairs secrete a sticky substance that attracts and traps small insects. When an insect lands on the sundew’s leaf and becomes stuck, the plant’s tentacles curl around the prey, bringing it closer to the leaf surface. Enzymes released by the plant then digest the trapped insect, allowing the sundew to absorb essential nutrients such as nitrogen and phosphorus. This carnivorous adaptation enables sundew plants to thrive in nutrient-poor soils, supplementing their diet with the nutrients obtained from captured prey.

Venus flytrap: The Venus flytrap is a carnivorous plant known for its unique trapping mechanism to capture and digest insects. It has specialized leaves with hinged traps that contain trigger-sensitive hairs. When an insect lands on the surface and triggers the hairs multiple times, the trap snaps shut rapidly, trapping the prey inside. The trapped insect is then digested by enzymes secreted by the plant over several days. The Venus flytrap derives essential nutrients, particularly nitrogen, from the digested prey, supplementing its diet in nitrogen-poor environments such as acidic bogs and wetlands. This carnivorous adaptation allows the Venus flytrap to thrive in habitats where other plants may struggle to obtain sufficient nutrients.

Symbiotic Plants:

Symbiotic plants are those that engage in mutually beneficial relationships with other organisms, typically fungi or bacteria. These symbiotic associations often involve the exchange of nutrients between the plant and its partner. One common example is mycorrhizal symbiosis, where fungi colonize the roots of plants and form structures called mycorrhizae. These fungi help the plant absorb water and nutrients, particularly phosphorus and nitrogen, from the soil, while the plant provides the fungi with carbohydrates produced through photosynthesis. Another example is nitrogen-fixing bacteria, which form symbiotic relationships with certain plants, such as legumes. These bacteria convert atmospheric nitrogen into a form that the plant can use for growth, while the plant provides the bacteria with sugars and a protected environment. Symbiotic plants rely on these partnerships to enhance their nutrient uptake, improve their resistance to stress, and ultimately thrive in various environments.

Nitrogen Fixation by Rhizobium:

Nitrogen fixation by Rhizobium is a symbiotic process wherein certain species of bacteria, specifically Rhizobium, form a mutualistic relationship with leguminous plants such as beans, peas, and clover. These bacteria colonize the roots of the host plant, forming structures called nodules. Within these nodules, Rhizobium bacteria convert atmospheric nitrogen (N2) into ammonia (NH3), a form of nitrogen that the plant can utilize for growth and development. In return, the plant provides the bacteria with carbohydrates and a suitable environment for growth. This symbiotic relationship benefits both parties: the plant gains access to essential nitrogen nutrients, while the bacteria receive energy sources and a protected habitat. This process plays a crucial role in maintaining soil fertility and is an important component of sustainable agricultural practices.

Lichens: Lichens are unique organisms resulting from a symbiotic relationship between fungi and algae or cyanobacteria. In this mutually beneficial partnership, the fungal partner provides structure, protection, and anchorage, while the photosynthetic partner (algae or cyanobacteria) produces food through photosynthesis. Lichens can be found in various habitats worldwide, including rocks, trees, and soil, and they come in a wide range of shapes, sizes, and colors. They play important ecological roles, such as soil stabilization, nutrient cycling, and serving as indicators of environmental health. Lichens are resilient organisms, capable of surviving in extreme conditions like deserts, arctic tundra, and polluted urban areas.

Myco-heterotrophs: Myco-heterotrophs are organisms that obtain their nutrients from fungi through a symbiotic relationship. Unlike plants, which typically engage in photosynthesis to produce their food, myco-heterotrophs lack chlorophyll and cannot photosynthesize. Instead, they rely on fungi for organic carbon and other nutrients. Myco-heterotrophs can establish associations with various types of fungi, including mycorrhizal fungi that form symbiotic relationships with plant roots. By tapping into the nutrient network of fungi, myco-heterotrophs are able to thrive in environments where photosynthesis is not feasible, such as dense forests with limited light availability. Examples of myco-heterotrophs include certain species of orchids and mono tropes.

How does soil regain lost nutrients?

Soil can regain lost nutrients through various natural processes, including:

Decomposition: Dead plant and animal matter decomposes in the soil, releasing nutrients back into the soil in a form that plants can absorb.

Nutrient cycling: Nutrients in the soil are recycled through biological processes such as the decomposition of organic matter, microbial activity, and the feeding activities of soil organisms.

Weathering of rocks and minerals: Over time, rocks and minerals break down into smaller particles through physical and chemical weathering processes. This releases minerals and nutrients into the soil.

Nitrogen fixation: Certain bacteria in the soil, such as Rhizobium species in root nodules of legumes, can convert atmospheric nitrogen into a form that plants can use, thus replenishing nitrogen in the soil.

Addition of organic matter: Adding organic materials like compost, manure, or mulch to the soil can increase its nutrient content and improve its fertility.

These processes work together to replenish lost nutrients in the soil, ensuring that it remains fertile and capable of supporting plant growth over time.

Detritivores: Detritivores are organisms that play a vital role in ecosystems by breaking down dead organic matter, such as dead plants and animals, into smaller particles and nutrients. They primarily feed on detritus, which includes decaying plant and animal material, feces, and other organic debris. Detritivores are often referred to as “nature’s recyclers” because they help to decompose organic matter and return nutrients to the soil, making them available for uptake by plants. Examples of detritivores include earthworms, millipedes, woodlice, and certain species of bacteria and fungi. Through their feeding activities, detritivores contribute to nutrient cycling and the overall health of ecosystems

Saprotrophs:

Saprotrophs, also known as saprophytes, are organisms that obtain their nutrients by decomposing dead organic matter. They play a crucial role in ecosystems by breaking down complex organic compounds into simpler forms, such as carbon dioxide, water, and inorganic nutrients. Saprotrophs secrete enzymes onto dead or decaying organic material, such as dead plants, animals, or fecal matter, to digest and absorb the resulting simpler molecules. By recycling nutrients from dead organic matter, saprotrophs contribute to the decomposition process and the recycling of nutrients back into the soil, making them available for uptake by plants and other organisms. Examples of saprotrophs include certain species of fungi, bacteria, and some protists.

What is saprotrophic nutrition?

Saprotrophic nutrition is a type of nutrition where organisms, called saprotrophs, obtain nutrients by decomposing dead organic matter. These organisms secrete enzymes onto the dead or decaying material, breaking it down into simpler compounds. These simpler compounds are then absorbed by the saprotrophs to fulfill their nutritional needs. Saprotrophic nutrition is vital for the decomposition of organic matter in ecosystems, facilitating nutrient recycling and the return of essential elements to the soil. Fungi and certain bacteria are common examples of organisms that exhibit saprotrophic nutrition, playing a crucial role in the decomposition process.

Saprophytes:

Saprophytes, also known as saprotrophs, are organisms that obtain nutrients by decomposing dead organic matter. They play a vital role in ecosystems by breaking down complex organic compounds into simpler forms, such as carbon dioxide and water, through the secretion of enzymes. Examples of saprophytes include certain species of fungi, bacteria, and some protists.

Recycling of Nutrients:

The recycling of nutrients refers to the process by which essential elements, such as carbon, nitrogen, and phosphorus, are reused and redistributed within an ecosystem. This process involves the breakdown of organic matter by decomposers, such as bacteria, fungi, and detritivores, which release nutrients back into the soil or water. These recycled nutrients are then absorbed by plants and other organisms, contributing to the sustainability and productivity of the ecosystem

Crop Rotation:

Crop rotation is a farming practice where different crops are planted in the same area over a sequence of growing seasons. This technique helps improve soil health, control pests and diseases, and enhance crop yield. By alternating crops with different nutrient needs, crop rotation helps prevent soil depletion and promotes sustainable agriculture.