Control And Coordination-III

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Q1. Plants respond to stimuli using:
Chemical and electrical signals
Plants lack a nervous system and muscles. Instead, they respond to stimuli (light, gravity, touch, etc.) through chemical signals (hormones like auxin) and weak electrical signals that travel from cell to cell. Blood circulation is absent in plants. Therefore, chemical and electrical signals are the correct means.

Q2. Special proteins in muscle cells change their:
Shape and arrangement
Muscle contraction is caused by the sliding filament mechanism, where the proteins actin and myosin change their relative arrangement (sliding past each other) and shape briefly during cross‑bridge formation. Colour does not change, number of proteins remains the same, and muscles are not inside bone.

Q3. The final job of performing movement in animals is done by:
Muscle tissue
While nervous tissue sends commands and bones provide leverage, the actual execution of movement (contraction, shortening) is carried out by muscle tissue. Blood does not perform movement. Thus, muscle tissue is the final effector.

Q4. Tendril movement is an example of:
Thigmotropism
Tendrils are modified stems or leaves that coil around a support when touched. This growth‑based response to physical contact is called thigmotropism. Phototropism is response to light, hydrotropism to water, and geotropism to gravity.

Q5. Involuntary muscles work:
Without conscious control
Involuntary muscles (e.g., heart muscle, smooth muscle in intestines) are controlled by the autonomic nervous system and function automatically without conscious thought. They work all the time, not only during sleep or exercise, and not “with thinking.”

Q6. Movement of Mimosa leaves is:
Independent of growth
Mimosa pudica (sensitive plant) folds its leaflets rapidly when touched. This movement is caused by changes in turgor pressure (water loss) in pulvini, not by cell growth. It is reversible and temporary, not permanent, and occurs quickly – not slowly. It is independent of growth.

Q7. Movement in plants due to growth is:
Slow
Growth‑based movements (e.g., bending of shoots toward light) occur through differential cell elongation, which takes minutes to hours. They are slow compared to animal movements or turgor‑based plant movements. They are not immediate, very fast, or temporary (they can be permanent in direction).

Q8. Environmental triggers for plant movement include:
Light and gravity
Plants respond to various environmental stimuli, including light (phototropism), gravity (geotropism), water (hydrotropism), and touch (thigmotropism). Blood, nerves, muscles, and bones are not environmental triggers; heat is only one of many, not the only one. Light and gravity are common and correct examples.

Q9. Touching the leaves of Mimosa causes them to:
Fold and droop
When touched, Mimosa leaves rapidly fold together and the leaf stalk droops. This is a defence mechanism against herbivores. The plant does not grow, change colour, or dry up in response to a single touch.

Q10. Nervous tissue is absent in plants because:
Plants use chemical coordination
Plants lack a nervous system because they rely on chemical signals (hormones) and electrical impulses (via plasmodesmata) for coordination. They do respond to stimuli, and slowness or weakness is not the reason. Thus, chemical coordination substitutes for nervous tissue.

Q11. When a nerve impulse reaches a muscle:
The muscle fibre moves
At the neuromuscular junction, an impulse triggers release of acetylcholine, causing muscle fibre contraction (movement). Relaxation occurs when impulses stop; blood flow and bone growth are not direct effects.

Q12. Immediate plant response does not require:
Growth
Immediate plant responses (e.g., Mimosa leaf folding, Venus flytrap closure) are based on rapid changes in turgor pressure (water movement) and do not involve cell growth. They still require living cells, a stimulus, and water. Growth is a slower process and not needed for immediate responses.

Q13. Plants lack specialised tissue for:
Conduction of information
Plants have specialised tissues for photosynthesis (mesophyll), storage (parenchyma), and respiration (all living cells). However, they lack nerve tissue or any equivalent for rapid, long‑distance conduction of information like animals. They use hormones and electrical signals but no dedicated “information‑conduction tissue.”

Q14. Mimosa leaf movement is:
Fast and temporary
Mimosa leaves fold within seconds of touch (fast) and later reopen after a few minutes (temporary). It is not growth‑based, not directional growth, and not permanent. This nastic movement is independent of the direction of stimulus.

Q15. Voluntary muscles are muscles that are:
Under conscious control
Voluntary muscles (skeletal muscles) are consciously controlled by the somatic nervous system. They are not automatic (involuntary), not found in plants, and are richly supplied with nerves.

Q16. Roots growing away from light helps plants to:
Absorb water and minerals
Roots exhibit negative phototropism (grow away from light) and positive geotropism (grow toward gravity). Growing away from light and into the soil increases access to water and minerals. Making food (photosynthesis) is done by shoots; seeds and water loss are not benefits.

Q17. Directional movement of seedlings is caused by:
Growth
Seedlings exhibit tropisms (directional growth) due to differential cell elongation on one side. Water absorption may be involved in turgor changes, but the underlying cause is growth. Muscle action is absent in plants; respiration provides energy but does not direct movement.

Q18. The sensitive plant is also called:
Mimosa
The sensitive plant, known for rapid leaf folding when touched, is Mimosa pudica. Cactus, sunflower, and pea plant do not show this rapid response.

Q19. Roots bend away from light showing:
Negative phototropism
Roots growing away from light is a response to light (photo‑) directed away from the stimulus (negative). Geotropism is gravity response, thigmotropism is touch, positive phototropism would be toward light (shoots).

Q20. Directional growth in plants appears as:
Movement
Directional growth (e.g., bending toward light or gravity) is a form of movement, though slow. It is not photosynthesis, respiration, or reproduction, although it supports these functions.

Q21. In sensitive plants, movement occurs at a point:
Different from point of touch
In Mimosa, touching one leaflet causes folding that spreads to adjacent leaflets and even other leaves. The movement occurs at sites away from the point of touch (signal transmission). It is not limited to roots, not always opposite end, and not only at the same point.

Q22. Muscle cells respond to:
Nervous electrical impulses
Muscle cells (skeletal) contract in response to electrical impulses from motor neurons. Some muscles also respond to hormones (e.g., adrenaline on heart), but the primary direct trigger for voluntary movement is nervous electrical impulses. Gravity and blood pressure do not directly cause contraction.

Q23. Plants do not have:
Nervous system
Plants have roots, leaves, and produce hormones (auxins, gibberellins, etc.), but they lack a nervous system (neurons, brain, nerves). Coordination is chemical and electrical without dedicated nerve cells.

Q24. Unequal growth in tendrils causes them to:
Coil around support
When a tendril touches a support, cells on the opposite side grow faster, causing the tendril to bend and coil around the object. This thigmotropic response uses differential growth. It does not cause falling, breaking, or drying.

Q25. Plant cell movement occurs due to change in:
Water content
Rapid plant movements (e.g., Mimosa, stomata opening/closing) result from changes in turgor pressure driven by water movement into or out of cells. Cell wall thickness is fixed, protein structure changes in muscle (not plants), and cell number increases in growth but not for immediate movement.

Q26. Plant movement independent of growth is also called:
Nastic movement
Nastic movements are responses to stimuli (e.g., touch, temperature) where the direction of movement is independent of the stimulus direction, and they occur without growth (using turgor changes). Tropic movements are growth‑based and directional. Voluntary and reflex are animal terms.

Q27. Muscle cells shorten because of:
Rearrangement of proteins
Muscle contraction (shortening) occurs when actin and myosin filaments slide past each other via cross‑bridge cycling – a rearrangement of proteins, not cell death, digestion, or water loss (water loss would cause shrinkage, not functional contraction).

Q28. Swelling or shrinking of plant cells results in:
Movement
Swelling (turgor increase) or shrinking (turgor loss) in plant cells causes movement – e.g., opening/closing of stomata, leaf folding in Mimosa. Growth is permanent increase in size; respiration and photosynthesis are metabolic processes.

Q29. Growth‑based plant movements are usually:
Directional
Growth‑based movements (tropisms) are directional – they occur toward or away from a stimulus (light, gravity, water). They are not sudden (slow), not non‑directional, and not random. Nastic movements (non‑growth) are non‑directional.

Q30. Tendrils are sensitive to:
Touch
Tendrils exhibit thigmotropism – they are highly sensitive to physical contact, which triggers coiling. While they may also respond to light or gravity, their primary specialised sensitivity is to touch.

Q31. Nervous tissue mainly helps in:
Collecting and processing information
The primary function of nervous tissue is to receive stimuli, process information, and integrate responses. Producing movement is done by muscles, but nervous tissue commands it. Growing bones and digesting food are not its main roles.

Q32. Information in plants is conveyed from cell to cell by:
Electrical‑chemical means
Plants use weak electrical signals (action potentials) and chemical signals (hormones, second messengers) that move via plasmodesmata or apoplast. They lack blood vessels, muscles, and nerves for information transfer.

Q33. Plants do not use muscles for movement because:
They use water pressure
Plants move by altering turgor pressure (water movement into/out of cells) or by differential growth. They do not have muscle tissue. Water pressure provides an alternative mechanism. Plants do respond and are not completely fixed (they move slowly).

Q34. Muscle movement at cellular level occurs due to:
Shape change of muscle cells
Muscle cells shorten (change shape) during contraction due to sliding filaments. Cell division occurs in growth, water loss is not the mechanism, and increase in size is not contraction – it’s the opposite.

Q35. Growth response away from stimulus is:
Negative tropism
A tropism is a growth response toward (positive) or away from (negative) a stimulus. For example, roots show negative phototropism (away from light). Neutral movement does not exist in this context; reflex is animal.

Q36. Coordination in plants is mainly achieved by:
Electrical and chemical signals
Plants coordinate responses using plant hormones (chemical signals) and electrical signals (action potentials). They lack bones, nerves, muscles, and blood circulation as animals have.

Q37. Immediate response in plants occurs:
Without growth
Immediate (rapid) plant responses, such as Mimosa leaf folding, are nastic movements based on turgor pressure changes, not growth. Growth is slow. Such responses occur in leaves and stems, not only roots.

Q38. Directional growth gives the appearance of:
Movement
Though plants are stationary, their directional growth (e.g., bending toward light) appears as a form of movement. This is not respiration, digestion, or reproduction, even though those processes occur.

Q39. Information in plants moves:
From cell to cell
Plants lack blood, nerves, and muscles. Signals (hormonal, electrical) move via plasmodesmata (cell‑to‑cell) or through the vascular system (e.g., auxin transport). “From cell to cell” is the correct description.

Q40. Plant responses help them mainly to:
Survive and grow
Plant responses to light, gravity, water, and touch enable them to obtain resources, avoid stress, and reproduce – i.e., survive and grow. Plants do not sleep, cannot escape predators actively (though some have deterrents), and do not produce sound.

Q41. When a tendril touches a support, the part in contact:
Grows slower
In thigmotropism of tendrils, the cells on the side in contact with the support elongate less (grow slower) than cells on the opposite side. This differential growth causes coiling. The part does not stop growing completely, break, or grow faster.

Q42. Shoots bending away from gravity show:
Negative geotropism
Shoots grow upward, away from the pull of gravity – this is negative geotropism (or negative gravitropism). Positive geotropism would be toward gravity (roots). Phototropism is light, thigmotropism is touch.

Q43. Tendrils help plants to:
Climb
Tendrils are thin, coiling structures that allow climbing plants to attach to supports, gaining height for light access. They do not produce seeds, absorb water (roots do), or make food (leaves do). Climbing is their primary function.

Q44. Chemical changes in plant cells mainly involve:
Proteins
Chemical changes in plant responses often involve proteins – e.g., receptor proteins, enzymes, and ion channels. Hormone signalling and electrical changes rely on protein activity. Lipids, DNA, and water movement are involved but not the primary chemical changes in signalling.

Q45. Growth response towards stimulus is called:
Tropic movement
A growth response directed toward or away from a stimulus is a tropism (tropic movement). Reflex and voluntary actions are animal terms, and it is not random.

Q46. Roots bending towards gravity show:
Positive geotropism
Roots grow downward, toward gravity – this is positive geotropism. Negative geotropism would be away (shoots). Phototropism is light, hydrotropism is water.

Q47. Plants show how many types of movement?
Two
Plant movements are broadly classified into two types: (1) growth‑dependent movements (tropisms) and (2) turgor‑dependent (independent of growth, e.g., nastic movements). Some sources also classify as tropic and nastic, but the basic count is two.

Q48. If growth is prevented in a seedling:
No movement occurs
Seedling movements (tropisms) depend on differential growth. If growth is prevented (e.g., by inhibitors or lack of water), the seedling cannot bend or orient itself. It may still have turgor‑based movements, but in a seedling, visible directional movement stops. Leaves falling or direction changes without growth are not possible.

Q49. Bending of shoots towards light helps plants to:
Get more light for photosynthesis
Positive phototropism in shoots maximizes light capture for photosynthesis, which produces food. Avoiding predators, root growth, and water absorption are not direct benefits of bending toward light.

Q50. Shoots bend towards light because of:
Phototropism
The bending of shoots toward light is a classic example of phototropism – growth response to light. Chemotropism is response to chemicals, gravity is geotropism, water is hydrotropism.