HOTS Questions: Plant Life | Science Class 5 PDF Download

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)
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)
Mycorrhizal associations are beneficial partnerships between plants and fungi. The fungi's hyphal networks extend into the soil, increasing the plant's surface area for water absorption and nutrient uptake. This mutualistic relationship helps plants thrive, especially in nutrient-poor soils.

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)
Opening stomata at night in arid environments like deserts helps plants like cacti take in carbon dioxide without losing excessive water through transpiration, as cooler temperatures and higher humidity during the night reduce water loss.

Q4: Which part of a plant embryo develops into the first leaves?
(a) Radicle
(b) Plumule
(c) Cotyledon
(d) Epicotyl
Ans: (b)
The plumule is the embryonic shoot of a plant embryo. It develops into the first leaves of the plant as it germinates. The radicle, on the other hand, becomes the root.

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)
Root hairs are tiny extensions of root cells that significantly increase the surface area of the roots. This increased surface area enhances the plant's ability to absorb water and nutrients from the soil.

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)
Nitrogen fixation is the process of converting atmospheric nitrogen into forms that plants can absorb. This enriches the soil with essential nitrogen compounds, supporting healthy growth and development in plants.

Q7: Which plant hormone is responsible for the elongation of stems towards light?
(a) Gibberellins
(b) Cytokinins
(c) Auxins
(d) Abscisic acid
Ans: (c)
Auxins are plant hormones that regulate various growth processes, including phototropism, which is the bending of plants towards light. Auxins accumulate on the shaded side of a stem, causing it to elongate more on that side, leading to the stem bending towards the light source.

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)
Deciduous trees shed their leaves to conserve water during the cold and dry winter months. As the leaves are the primary sites for water loss through transpiration, shedding them helps the tree conserve resources and survive winter conditions.

Q9: Which plant adaptation is prominent in plants that live in habitats with frequent wildfires?
(a) Rapid flower production
(b) Ability to photosynthesize in low light
(c) Thick bark and underground buds
(d) Extremely tall stems
Ans: (c)
Plants that live in habitats with frequent wildfires often have thick bark to protect against the heat and underground buds that can sprout new growth after the fire has passed, enabling them to regenerate quickly.

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)
Nitrogen-fixing nodules are formed when certain types of bacteria establish a symbiotic relationship with the roots of plants. These bacteria convert atmospheric nitrogen into a usable form, providing plants with essential nutrients.