7th Grade Science Test Quiz!

Explanation
Autotrophs are organisms that are able to produce their own food using simple naturally available raw materials, such as sunlight, water, and carbon dioxide. They are capable of photosynthesis or chemosynthesis, converting these raw materials into organic compounds that they can use as a source of energy. Autotrophs are the opposite of heterotrophs, which rely on consuming other organisms for their food. Parasites and saprophytes are also types of heterotrophs, but they do not prepare their own food.

Explanation
Photosynthesis is the process by which plants convert sunlight into energy. Chlorophyll is a pigment found in the chloroplasts of plant cells that is responsible for capturing sunlight and initiating the photosynthesis process. Without chlorophyll, plants would not be able to absorb sunlight and therefore photosynthesis would not occur. Guard cells are responsible for regulating the opening and closing of stomata, which are necessary for gas exchange during photosynthesis. The vacuole is responsible for storing water and nutrients, but it is not directly involved in the photosynthesis process. The space between cells is also not directly involved in photosynthesis.

Explanation
The correct answer is "grows in soils which lack in nitrogen." Pitcher plants are known for their unique adaptation to nutrient-poor environments. They have specialized leaves that form a pitcher-like structure, which traps insects. The main reason for this adaptation is that pitcher plants typically grow in soils that are deficient in nitrogen. By capturing and digesting insects, they obtain the necessary nutrients, including nitrogen, to survive in these nutrient-poor conditions.

Explanation
The correct answer is (i) and (iv) because statement (i) is true, as green plants have chlorophyll which enables them to prepare their own food through photosynthesis. Statement (iv) is also true, as oxygen is indeed liberated as a byproduct of photosynthesis. Statement (ii) is incorrect because most animals are heterotrophs, meaning they rely on consuming other organisms for food. Statement (iii) is also incorrect because carbon dioxide is essential for photosynthesis as it is one of the reactants in the process.

Explanation
Stomata are the small openings found on the lower surface of a leaf that are visible when observed through a magnifying lens. These openings allow for gas exchange between the leaf and the surrounding environment, facilitating the intake of carbon dioxide for photosynthesis and the release of oxygen and water vapor.

Explanation
Excretion is not a part of nutrition because it refers to the process of eliminating waste materials from the body, such as urine and feces. Nutrition, on the other hand, involves the intake and utilization of nutrients by the body for growth, energy, and overall health. While digestion, absorption, and assimilation are all processes involved in the breakdown and absorption of nutrients from food, excretion is unrelated to the intake and utilization of nutrients.

Explanation
Birds do not have teeth. Unlike rats, elephants, and snakes, birds have a beak instead of teeth. The beak is a hard, pointed structure that birds use for various purposes such as eating, grooming, and defense. Birds have adapted to have a beak instead of teeth to suit their specific dietary needs and lifestyles. This adaptation allows them to efficiently catch and consume their prey, as well as crack open seeds or nuts.

Explanation
Amylase enzyme is present in saliva. Saliva contains an enzyme called amylase, which is responsible for breaking down starch into simpler sugars. This enzyme begins the process of digestion in the mouth by breaking down complex carbohydrates into smaller molecules that can be easily absorbed by the body.

Explanation
Bile is a substance produced by the liver and stored in the gallbladder. Its main function is to aid in the digestion and absorption of fats. Bile helps to break down large fat molecules into smaller ones, making it easier for enzymes to digest them. Therefore, fats are digested by bile.

Explanation
Woollen clothes are made from animals, specifically the fur or hair of certain animals like sheep, goats, or rabbits. The fur or hair is sheared or collected from these animals and then processed to remove impurities and create yarn. This yarn is then woven or knitted to make woollen fabrics, which are known for their warmth and insulation properties.

Explanation
Wooly Dog does not yield wool because it is not a natural source of wool. While yaks, camels, and goats are known for producing wool, wooly dogs do not possess the necessary characteristics or genetic traits to produce wool.

Explanation
Moth is not a type of silk. Moth refers to the insect that produces silk, but it is not a specific type of silk itself. Mulberry, Mooga, and Tassar are all different types of silk produced by different species of silkworms.

Explanation
Silk fiber is obtained from the cocoon. The cocoon is a protective covering spun by silkworms to encase themselves during the pupal stage of their life cycle. The silk fiber is extracted from these cocoons by unraveling the silk threads. This process is known as sericulture and it is primarily carried out in countries like China, India, and Brazil, where silk production is a major industry. The silk fiber obtained from the cocoon is then processed and woven into various silk fabrics, known for their smoothness, strength, and lustrous appearance.

Explanation
Silkworms secrete fiber made of protein. This is because silk, which is produced by silkworms, is primarily composed of fibroin, a protein. Silkworms spin cocoons made of silk fibers, which they produce by secreting the fibroin protein from their silk glands. These fibers are then used to create silk fabric, known for its strength, smoothness, and lustrous appearance.

Explanation
Silviculture refers to the cultivation and management of trees and forests, not the rearing of silkworms for obtaining silk. The correct term for the rearing of silkworms is sericulture.