STD 7 Science Chapter 4

Explanation
Nepenthes is insectivorous because it is a pitcher plant that has specialized leaves adapted to trap and digest insects. The plant forms pitcher-like structures that contain a fluid which attracts and drowns insects. The plant then absorbs nutrients from the decomposing insects to supplement its diet, making it a carnivorous plant.

Explanation
Stomata are small openings on the surface of leaves that regulate the exchange of gases and the loss of water through transpiration. They control the rate of water loss by opening and closing their pores, allowing water vapor to escape when open and minimizing water loss when closed. The other options listed, such as the midrib and vascular bundle, are not directly involved in controlling the rate of water loss from the leaf.

Explanation
All of these options are considered nutrients. Proteins are essential macronutrients that are required for growth and repair of body tissues. Vitamins are micronutrients that are necessary for various metabolic processes in the body. Therefore, all of these options are correct as they are all nutrients.

Explanation
Human beings are categorized as heterotrophs because they obtain their energy and nutrients by consuming other organisms. Unlike autotrophs, which can produce their own food through processes like photosynthesis, human beings rely on consuming plants or other animals for sustenance. Parasites, on the other hand, are organisms that live in or on another organism (the host) and rely on the host for their nourishment. Therefore, the correct categorization for human beings is heterotrophs.

Explanation
Photosynthesis is the correct answer because it is the process by which plants convert sunlight, carbon dioxide, and water into glucose (food) and oxygen. During this process, plants use chlorophyll, a pigment found in their cells, to capture sunlight energy and convert it into chemical energy. This chemical energy is then used to produce glucose, which serves as the plant's food source. Therefore, photosynthesis is the food-making process in plants. Glycolysis is a metabolic pathway that occurs in the cytoplasm of cells and breaks down glucose to produce energy. Chemosynthesis is a process by which certain bacteria and archaea convert inorganic compounds into organic compounds without using sunlight.

Explanation
Leaves are called the food factory of a plant because they contain chloroplasts, which are responsible for photosynthesis. During photosynthesis, leaves use sunlight, water, and carbon dioxide to produce glucose (a form of sugar) and oxygen. Glucose is the primary source of energy for the plant, and it is transported to other parts of the plant for growth and development. Therefore, leaves play a crucial role in producing food for the plant.

Explanation
Chlorophyll is the correct answer because it is the green pigment present in the leaves. It is responsible for capturing light energy and converting it into chemical energy through the process of photosynthesis. Chlorophyll gives leaves their green color and plays a crucial role in the plant's ability to produce glucose and oxygen. Hemoglobin and globulin are not green pigments and are not found in leaves.

Explanation
The raw materials for photosynthesis are carbon dioxide (CO2) and water (H2O). During photosynthesis, plants use sunlight energy to convert CO2 and H2O into glucose and oxygen (O2). The glucose is then used as a source of energy for the plant, while the oxygen is released into the atmosphere. Therefore, the correct answer is CO2, as it is one of the essential raw materials for photosynthesis.

Explanation
Cuscuta is a parasite because it is a genus of plants that lack chlorophyll and cannot produce their own food through photosynthesis. Instead, they attach themselves to other plants and obtain nutrients from them, effectively parasitizing the host plant. This dependency on a host plant for survival is a characteristic feature of parasitic organisms.

Explanation
Amoeba is a single-celled organism that belongs to the group of protists. Unlike multicellular organisms like frogs and cows, amoebas do not have specialized organs like hands and mouths. Instead, they have a flexible cell membrane that allows them to engulf food particles and move by extending and retracting their pseudopods. This unique characteristic of amoebas sets them apart from other organisms and makes them the correct answer in this case.

Explanation
Leaves are indeed the food factory of a plant. Through a process called photosynthesis, leaves use sunlight, water, and carbon dioxide to produce glucose, which is the plant's source of energy. This glucose is then converted into other substances, such as starch, that can be stored and used as needed by the plant. Therefore, leaves play a crucial role in the plant's ability to produce its own food.

Explanation
Food is essential for all living organisms because it provides the necessary nutrients and energy required for growth, development, and maintenance of bodily functions. Without food, living organisms would not be able to survive or carry out their normal physiological processes. Food provides essential macronutrients such as carbohydrates, proteins, and fats, as well as micronutrients like vitamins and minerals, which are all crucial for the proper functioning of the body. Therefore, it is true that food is essential for all living organisms.

Explanation
Water does not enter leaves in the form of vapor through stomata. Stomata are small openings on the surface of leaves that allow for gas exchange, including the release of water vapor through a process called transpiration. However, water is primarily absorbed by the roots of plants and transported through the xylem tissue to the leaves, where it is used for various metabolic processes and transpiration occurs. Therefore, the given statement is false.

Explanation
Algae are not saprotrophs. Saprotrophs are organisms that obtain nutrients by decomposing dead organic matter. Algae, on the other hand, are autotrophic organisms that can produce their own food through photosynthesis. They use sunlight, water, and carbon dioxide to synthesize organic compounds. Therefore, the statement "Algae are saprotrophs" is false.

Explanation
Cuscuta is not a parasite. It is actually a genus of plants that are commonly known as dodder. While dodder plants are parasitic, not all plants in the Cuscuta genus are parasitic. Some species of Cuscuta are actually non-parasitic and can photosynthesize to obtain their own nutrients. Therefore, the statement "Cuscuta is a parasite" is false.