Chapter 5 Quiz 1 (2nd Secondary Biology)

When the potted plant was placed horizontally in a dark room, the root of the plant bent downwards in response to gravity, while the stem of the plant bent upwards in search of light. This phenomenon is known as gravitropism, where the root grows in the direction of gravity and the stem grows against it. The aluminium foil covering the tip of the stem prevented it from receiving any light, causing it to grow in a direction opposite to gravity.

The Mimosa plant has a unique response to touch called thigmonasty, where its leaflets and pulvini (small swollen structures at the base of each leaflet) undergo rapid movement when touched. This movement is a defensive mechanism to protect the plant from potential threats. However, the stem does not undergo any significant movement in response to touch. Therefore, the correct answer is stem.

The correct answer is compound and pinnate with four secondary rachises. This means that the leaves of a Mimosa plant are composed of multiple leaflets arranged in a feather-like pattern along a central axis (primary rachis). Each leaflet is further divided into smaller leaflets (secondary rachises), with a total of four secondary rachises branching off from the primary rachis.

Sensation is the process by which organisms detect and respond to stimuli in their environment. In the case of flowers opening in the morning and closing in the evening, this is a response to the stimulus of light. Flowers have specialized cells called photoreceptors that detect changes in light intensity. When light levels are high in the morning, the flowers open to maximize their exposure to sunlight for photosynthesis. As the day progresses and light levels decrease, the flowers close to protect their reproductive organs and conserve energy. This opening and closing of flowers is a sensory response to the changing light conditions.

Water moves to the cells in the lower half of primary pulvini, causing these cells to become turgid. This is true because the movement of water in the Mimosa plant is responsible for the plant's ability to fold and unfold its leaves in response to stimuli. The primary pulvini are specialized structures at the base of each leaflet that control leaf movement. When water moves into the cells in the lower half of the primary pulvini, it causes these cells to swell and become turgid, which results in the folding or closing of the leaf.

The correct answer is A because it shows that the growth rate of the growing tip cells of the part away from light in the stem of the plant is slower compared to the other options. This suggests that light is necessary for the optimal growth of the plant, and without it, the growth rate is reduced.

The attitude of Venus Flytrap plant towards insects is described as nastic movement. Nastic movement refers to the non-directional response of a plant to a stimulus, such as the closing of the Venus Flytrap's leaves when an insect touches its trigger hairs. This movement is not dependent on the direction of the stimulus, but rather a general response to it.

The movement of sunflowers in accordance with the path of the sun is due to heliotropism. Heliotropism is the ability of plants to track the movement of the sun throughout the day. Sunflowers are known for their heliotropic behavior, as they face east in the morning and follow the sun as it moves across the sky, eventually facing west in the evening. This movement is controlled by specialized cells in the stem that respond to light and help the plant optimize its exposure to sunlight for photosynthesis.

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Geotropism is the correct answer because it refers to the growth or movement of a plant in response to gravity. When the root of a plant grows downwards, it is exhibiting positive geotropism, as it is growing in the direction of gravity. This phenomenon allows the roots to anchor the plant in the soil and absorb water and nutrients effectively. Phototropism refers to the growth or movement of a plant in response to light, haptotropism refers to the growth or movement of a plant in response to touch, and hydrotropism refers to the growth or movement of a plant in response to water.

The correct answer is touch movement in the leaves of the Mimosa plant. This plant exhibits a rapid response to touch, where its leaves fold up or droop when touched. This movement can be easily observed and is a clear example of a plant part moving quickly in response to a stimulus.

The figure shows an experiment where two coleoptiles, A and B, are placed next to mica and gelatin blocks. The question asks why coleoptile A bends while coleoptile B does not bend. The correct answer is that auxins, which are plant hormones responsible for bending growth, can diffuse through the gelatin block but not through the mica block. This suggests that the presence of auxins on one side of the coleoptile, diffusing through the gelatin block, causes it to bend towards that side. However, since auxins cannot diffuse through the mica block, coleoptile B does not receive auxins and therefore does not bend.

The diagram shows the effect of auxins on a structure, which is represented by X. Auxins are plant hormones that promote root growth. Therefore, the structure X in the diagram represents the root of the plant.

Positive phototropism is the correct answer because it refers to the phenomenon where a plant grows towards a light source. Plants exhibit positive phototropism as they bend or grow towards the light in order to maximize their exposure to sunlight for photosynthesis.

Auxin hormone is produced at the tip of the stem in plants. This hormone plays a crucial role in plant growth and development, including cell elongation, root formation, and phototropism. It is synthesized in the apical meristem, which is present at the tip of the stem. From there, it is transported downwards to other parts of the plant, where it regulates various physiological processes.

The correct rate of growth for the root parts when subjected to water from only one direction would be represented by graph C. This graph shows a gradual increase in growth over time, indicating that the root is receiving a steady supply of water. The other graphs either show no growth or inconsistent growth, which would not be expected when water is provided from one direction.

Positive haptotropism is the correct answer because haptotropism refers to the directional growth or movement of an organism in response to touch or contact stimuli. In this example, the plant is coiling around another type of plant in response to physical contact, which is an example of positive haptotropism.

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The folding up of the leaves of a sensitive plant on touching with a finger is not a tropism because there is no change in the growth of the plant. Tropism refers to the directional growth response of a plant towards or away from a stimulus, such as light or gravity. In this case, the folding up of the leaves is a touch-induced movement, but it does not involve any growth or change in the overall direction of growth of the plant.

Tropism is the correct answer because it refers to the growth movement of a plant part in response to an external stimulus, where the direction of the stimulus determines the direction of the plant's response. This can include movements such as phototropism (response to light), geotropism (response to gravity), and hydrotropism (response to water). Sleeping movement, turgidity, and touch movement do not accurately describe this specific type of growth response.

Roots respond positively to gravity by growing downwards. This is known as geotropism or gravitropism. The roots have specialized cells called statocytes that contain dense starch grains, which settle under the influence of gravity. This helps the roots sense the direction of gravity and grow in the opposite direction, towards the center of the Earth. This allows the roots to anchor the plant in the soil and absorb water and nutrients from the ground.

Diagram D shows a negative geotropism because the plant is growing in an upward direction, against the force of gravity. This can be observed by the stem and leaves extending vertically upwards. In contrast, diagrams A, B, and C show positive geotropism, as the plants are growing in the direction of gravity, with their stems and leaves bending downwards.

Phototropism is the growth or movement of an organism towards or away from light. Positive phototropism refers to the growth towards light. In plants, the stem and leaves are the parts that display positive phototropism. The stem grows towards the light source to maximize light absorption for photosynthesis, while the leaves adjust their position to receive optimal sunlight. The roots, on the other hand, exhibit negative phototropism, growing away from light sources, as they are responsible for anchoring the plant and absorbing water and nutrients from the soil.

The pad-like swelling at the base of each leaf of a sensitive plant is called pulvini. Pulvini are specialized structures found in certain plants that allow for rapid leaf movement. They are responsible for the plant's ability to fold its leaves in response to touch or other stimuli. This folding action is a defense mechanism that helps protect the plant from potential harm. The pulvini contain motor cells that respond to electrical signals, causing the leaves to move.

In the experiment, coleoptile (1) bends towards coleoptile (2) because coleoptile (1) is subjected to a unilateral light source. This bending is known as phototropism, where plants grow towards the light source. Coleoptile (2) grows vertically upwards because it is not subjected to any light source. This is the natural growth pattern of plants in the absence of light. Therefore, after some hours of the experiment, coleoptile (1) will bend towards coleoptile (2), and coleoptile (2) will grow vertically upwards.

If the tip of the oat coleoptile is separated by a glass sheet and then exposed to light from one direction, nothing will happen. This is because the tip of the coleoptile is responsible for sensing light and initiating phototropism, which is the growth or movement of an organism in response to light. However, when the tip is separated by a glass sheet, it is unable to detect the light and therefore cannot initiate phototropism.

The cress seedlings in Pot (2) were placed in a cupboard with no light. As a result, they grew straight up towards the only available light source, which is the opening of the cupboard. This is an example of positive phototropism, where the plants grow towards the light.

Graph B represents the effect of auxin on the growth of the growing tip cells of both the stem and the root of the seedling. This is because the graph shows an increase in growth rate initially, followed by a decrease in growth rate. This is consistent with the known effects of auxins, which promote cell elongation and division in the early stages of growth, but inhibit growth at higher concentrations.

High concentrations of auxins inhibit the elongation of root cells. Auxins are plant hormones that regulate various growth processes, including cell elongation. At low concentrations, auxins promote cell elongation, but at high concentrations, they have an inhibitory effect. This is because high levels of auxins can disrupt the balance of other hormones and signaling pathways involved in cell growth, leading to the inhibition of root cell elongation.

In the experiment, the coleoptiles (A) and (B) are exposed to light. Coleoptile (A) will not bend because it has been covered with an opaque cap, preventing light from reaching it. On the other hand, coleoptile (B) is exposed to light, causing it to bend towards the light source. This is known as phototropism, a plant's growth response to light. Therefore, the correct answer is that (A) will not bend, while (B) will bend towards light.

By removing the tip from one of the plant shoots and leaving the other intact, the student can observe the changes in growth. If the hormone responsible for the response to directional light is found in the tip, the plant shoot with the removed tip would not show the expected response to light, while the intact shoot would continue to respond. This would indicate that the hormone is indeed located in the tip of the plant shoot.

In diagram D, the root is bending towards the water source (hydrotropism) and also towards the light source (phototropism). This suggests that phototropism is enhancing the hydrotropism of the root, as it is guiding the root towards both the light and water sources.

Gravitropism is the growth or movement of a plant in response to gravity. In this example, the potted plant falls on its side, but its roots still grow downward, showing the effect of gravitropism. The plant is able to sense the direction of gravity and adjust its growth accordingly, ensuring that its roots continue to grow in the downward direction.

Haptotropism is the correct answer because it refers to the plant's response to touch or contact. In this case, the ivy plant is exhibiting haptotropism by wrapping itself around a stick or string, which is a form of contact. The plant is able to sense the presence of the object and responds by growing and wrapping around it, using it for support. This behavior allows the ivy plant to climb and reach higher positions for better access to sunlight.

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The rapid movement of leaves of mimosa on touching is an example of turgor movement. Turgor movement is a type of movement in plants that occurs due to changes in turgor pressure within plant cells. When the leaves of mimosa are touched, there is a rapid loss of turgor pressure in the cells of the leaflets, causing them to fold and droop. This response is a protective mechanism to defend against potential harm or damage.

The shoot (R) is going to take responses 2 and 4 with respect to the direction of light falls on it.

The experiment in the figure shows that the root is positively hydrotropic. This means that the root is growing towards the water source. The root is bending and growing in the direction of the water, indicating a positive response to the presence of water.

The correct answer is B because the question asks which area of the stem has cells that are elongated more than the others due to the effect of IAA produced in the meristems. Since IAA is a plant hormone that promotes cell elongation, the area where the cells are elongated the most would be where the IAA is most concentrated. In the given stem, area B is located closest to the meristems where IAA is produced, so it is likely to have the highest concentration of IAA and therefore the most elongated cells.

From the given information, we can infer that the photo was taken at night. The fact that the photo was taken at night is explicitly mentioned in the options and none of the other options provide any indication about the time of day or the position of the plant. Therefore, the only inference that can be made is that the photo was taken at night.

Auxin is a plant hormone that plays a crucial role in regulating growth and development. In roots, a high concentration of auxin inhibits cell elongation. This is because auxin promotes the growth of root hairs and lateral roots, rather than elongation of the main root. Therefore, the correct statement is that a high concentration of auxin inhibits the cell elongation in roots.

In both examples, the root and the stem bend towards the stimulus because auxins accumulate on the side of the root and stem facing the stimulus. This accumulation of auxins causes the cells on that side to elongate and grow faster, resulting in bending towards the stimulus. Therefore, the correct statement is that the root and the stem bend towards the stimulus.

Roots of a plant exhibit negative phototropism, which means they grow away from light, and positive geotropism, which means they grow towards gravity. This is because roots need to anchor the plant in the soil and absorb water and nutrients, which are typically found in the ground. Therefore, they grow in the opposite direction of light and towards the force of gravity.

The correct answer is B because in the figure, the coleoptile is bending away from the light source, indicating a positive phototropic response. Placing a foil collar below the tip of the coleoptile blocks the light from reaching the lower side, causing the coleoptile to bend towards the light source. This experiment demonstrates that light plays a role in the direction of coleoptile growth.

Drooping of leaves in response to touch is not a growth dependent response because it is not influenced by the growth of the plant. The movement of roots towards gravity and movement of shoots towards light are growth dependent responses as they involve the growth of plant tissues in response to external stimuli. Similarly, the movement of shoots away from gravity is also a growth dependent response as it involves the growth of plant tissues in the opposite direction of gravity.

The pulvinus is a joint-like structure found at the base of the leaflet that allows it to fold upward. In the given diagram, letter W represents the pulvinus as it is located at the base of the folded leaflet.

Hydrotropism is the growth or movement of a plant in response to water. In this case, the concentration of auxin, a plant hormone that regulates growth, is equal on both sides of the plant's coleoptile. This is because the plant is actively seeking water and therefore there is no concentration gradient of auxin that would cause differential growth. In contrast, geotropism is the growth or movement of a plant in response to gravity, and phototropism is the growth or movement of a plant in response to light. In both of these cases, there is a concentration gradient of auxin that causes differential growth, resulting in unequal concentrations of auxin on both sides of the coleoptile. Therefore, the correct answer is hydrotropism.

Gravitropism is the growth or movement of a plant in response to gravity. In this case, the appropriate stimulus for gravitropism is gravity, as it is what triggers the plant's response. The response, on the other hand, is the stem growing up. This is because plants exhibit positive gravitropism, meaning they grow in the direction of gravity. Therefore, when the stimulus of gravity is present, the stem will grow in an upward direction.

Phototropism is the growth response of plants towards light, while hydrotropism is the growth response towards water. When one side of the root faces water while the other side faces light, the root will exhibit both phototropism and hydrotropism simultaneously. The root will grow towards the water side due to hydrotropism and towards the light side due to phototropism, enhancing the hydrotropic response. This is because the presence of light on one side of the root stimulates the growth towards that side, while the presence of water on the other side attracts the root towards it.

The growth of roots is often associated with their response to water. When roots sense the presence of water, they elongate and grow towards the source of water, allowing the plant to absorb more water and nutrients. This growth response is crucial for the plant's survival and overall development. On the other hand, the other options mentioned in the question involve movement or responses that are not directly related to growth.