Class 7 Science MCQ Chapter 1

The Sun is the ultimate source of energy in our Earth. It radiates light and heat energy, which is essential for various processes on Earth. Through a process called photosynthesis, plants convert solar energy into chemical energy, which is then consumed by other organisms in the food chain. Additionally, solar energy is harnessed through solar panels to generate electricity. The Sun's energy also drives weather patterns, ocean currents, and the water cycle. Therefore, the Sun plays a crucial role in sustaining life and powering the Earth's systems.

Litchen is a symbiotic relationship between algae and fungi. The fungi provide a protective structure for the algae and absorb water and nutrients for them, while the algae produce food through photosynthesis. This mutualistic relationship allows both organisms to thrive in environments where they might not be able to survive alone. Protozoa and viruses do not form a symbiotic relationship with algae, so they are not the correct answer.

Iodine can be used to test for the presence of starch in our food. When iodine comes into contact with starch, it forms a blue-black color. This reaction is a reliable indicator of the presence of starch. Therefore, if we want to determine whether a particular food contains starch or not, we can use iodine as a testing agent.

Insectivorous plants feed on insects for nitrogen. Insects are a rich source of nitrogen, which is an essential nutrient for plant growth. These plants have evolved to capture and digest insects as a way to supplement their nutrient intake, especially in nutrient-poor environments such as bogs or acidic soils. By obtaining nitrogen from insects, insectivorous plants can thrive in habitats where other plants may struggle to survive due to limited nitrogen availability.

Cuscuta is an example of a parasitic plant. It is commonly known as dodder and belongs to the family Cuscutaceae. This plant lacks chlorophyll and cannot produce its own food through photosynthesis. Instead, it attaches itself to the stems of other plants and absorbs nutrients and water from its host. Cuscuta has specialized structures called haustoria that penetrate the host plant's tissues to extract nutrients. This parasitic relationship can be detrimental to the host plant as it weakens and eventually may lead to its death.

During photosynthesis, plants use sunlight, water, and carbon dioxide to produce glucose and oxygen. Oxygen is a byproduct of this process and is released into the atmosphere. Therefore, the correct answer is oxygen.

Money plant is an example of a variously coloured leafed plant. It is known for its attractive and vibrant green leaves, which can sometimes have hints of yellow or silver. The leaves of the money plant can also have unique patterns or variegation, adding to its visual appeal. This makes it a suitable choice for those looking for a plant with different colored leaves.

Fungi is an example of a saprophytic organism. Saprophytic organisms obtain their nutrients by decomposing dead organic matter. Fungi play a crucial role in the ecosystem as they break down dead plants and animals, recycling nutrients back into the environment. They secrete enzymes that break down complex organic compounds into simpler forms, which they can then absorb and use for their own growth and reproduction. This process of decomposition is essential for nutrient cycling and ecosystem functioning.

Fungi is the correct answer because it is a non-chlorophyllous plant. Unlike algae and lichen, fungi do not contain chlorophyll and therefore cannot perform photosynthesis. Instead, fungi obtain nutrients by absorbing organic matter from their surroundings.

Roots of higher plants have a symbiotic relationship with fungi. This relationship is known as mycorrhizae, where the fungi colonize the roots and form a mutually beneficial association with the plant. The fungi provide the plant with increased nutrient absorption, especially phosphorus, while the plant provides the fungi with carbohydrates produced through photosynthesis. This symbiotic relationship enhances the plant's ability to survive and thrive in various soil conditions, making it an essential component of plant growth and ecosystem functioning.