Plant Life Extra Questions And Answers - Class 5 Science | Important Question Answer

Q1: Which plant adaptation is responsible for the movement of water from the roots to the leaves?
(a) Transpiration
(b) Photosynthesis
(c) Respiration
(d) Absorption
Ans: (a)
Explanation: Transpiration is the process by which plants release water vapor into the atmosphere through small openings called stomata on the surface of leaves. This process creates a continuous flow of water from the roots to the leaves, allowing the plant to absorb essential nutrients and minerals from the soil.

Q2: What is the primary role of mycorrhizal associations in plant growth?
(a) Protection against herbivores
(b) Enhanced water absorption
(c) Increased flower production
(d) Direct energy production
Ans: (b)
Explanation: Mycorrhizal associations are helpful partnerships between plant roots and fungi. The fungi send out fine threads (hyphae) into the soil, which act like extra rootlets and increase the area available for taking up water and nutrients. This makes it easier for plants to get scarce minerals, especially in poor soils. In return, the plant supplies the fungi with sugars. Together they help the plant grow more healthily.

Q3: Why do some plants like cacti open their stomata only at night?
(a) To conserve water loss
(b) To prevent pests from entering
(c) To aid in nighttime photosynthesis
(d) To allow carbon dioxide intake
Ans: (d)
Explanation: Many desert plants open their stomata at night so they can take in carbon dioxide when it is cooler and more humid. Nighttime conditions reduce water loss, so the plant can collect CO₂ with less evaporation from the leaves. The CO₂ taken in at night is stored and used for photosynthesis during the day, helping the plant survive dry conditions.

Q4: Which part of a plant embryo develops into the first leaves?
(a) Radicle
(b) Plumule
(c) Cotyledon
(d) Epicotyl
Ans: (b)
Explanation: The plumule is the embryonic shoot in a seed. As the seed germinates, the plumule grows upward and develops into the plant's first true leaves. The radicle grows downwards and becomes the root system.

Q5: What is the primary function of the root hairs in plants?
(a) Photosynthesis
(b) Water absorption
(c) Flower production
(d) Nutrient storage
Ans: (b)
Explanation: Root hairs are tiny finger-like extensions of root cells that greatly increase the surface area of the root. This larger surface area helps the plant absorb more water and minerals from the soil. Because they are thin and close to the soil particles, root hairs make absorption much more efficient.

Q6: How do plants benefit from the process of nitrogen fixation?
(a) Enhanced water absorption
(b) Increased photosynthesis
(c) Improved disease resistance
(d) Access to essential nutrients
Ans: (d)
Explanation: Nitrogen fixation is the process by which certain organisms change atmospheric nitrogen into forms that plants can use, such as nitrates. This adds usable nitrogen to the soil, which plants need to make proteins and grow well. As a result, plants in nitrogen-rich soils grow healthier and stronger.

Q7: Which plant hormone is responsible for the elongation of stems towards light?
(a) Gibberellins
(b) Cytokinins
(c) Auxins
(d) Abscisic acid
Ans: (c)
Explanation: Auxins are plant hormones that control several growth processes, including phototropism - the bending of a stem toward light. Auxins gather on the shaded side of a stem, causing cells there to grow longer. This uneven growth makes the stem bend towards the light, helping the plant receive more sunlight for photosynthesis.

Q8: Why do deciduous trees shed their leaves in the fall?
(a) To reduce water loss during winter
(b) To prepare for pollination
(c) To prevent overgrowth
(d) To conserve energy
Ans: (a)
Explanation: Deciduous trees lose their leaves in autumn mainly to reduce water loss during the cold, dry winter months. Leaves lose water through transpiration, so shedding them helps the tree conserve its moisture and survive when liquid water is harder to obtain. This also reduces the energy the tree needs to maintain its leaves over winter.

Q9: Which plant adaptation is prominent in plants that live in habitats with frequent wildfires?
(a) Rapid flower production
(b) Ability to photosynthesis in low light
(c) Thick bark and underground buds
(d) Extremely tall stems
Ans: (c)
Explanation: Plants in fire-prone areas often have thick bark that insulates and protects the living tissues from heat. They also have buds or roots buried underground that survive the fire and can sprout new shoots afterwards. These features help the plants recover quickly after fires.

Q10: In a symbiotic relationship known as nitrogen-fixing nodules, which organisms are involved?
(a) Fungi and plants
(b) Bacteria and plants
(c) Insects and plants
(d) Birds and plants
Ans: (b)
Explanation: Nitrogen-fixing nodules form when certain bacteria live in partnership with plant roots, especially in legumes. The bacteria convert atmospheric nitrogen into forms the plant can use, and the plant supplies the bacteria with food.