Nutrition in Living Beings – Long Answer Questions

Medium Level (Application & Explanation)

Answer:

Living beings need energy for every life process.
Even at rest, the body does breathing, circulation, and digestion.
These processes use chemical energy from food or stored materials.
An athlete needs extra energy for training and repair of muscles.
A growing child needs energy for growth, movement, and brain work.
Plants also need energy for photosynthesis, transport of food, and making new cells.

Answer:

Autotrophs make their own food using inorganic substances.
Plants, algae, and some bacteria are autotrophs.
Heterotrophs cannot make food. They depend on other organisms.
Herbivores eat plants. Carnivores eat animals. Decomposers break dead matter.
Energy flows from sun → autotrophs → heterotrophs → decomposers.
Thus, autotrophs are the primary source of food and energy for all life.

Answer:

In photosynthesis, plants make glucose from carbon dioxide and water.
Chlorophyll absorbs sunlight and powers the reaction.
Oxygen is released as a byproduct.
The glucose may be used at once or stored as starch.
Leaves, stems, and roots can store this starch for later use.
This process turns light energy into chemical energy essential for life.

Answer:

Stomata are tiny pores on the leaf surface.
They allow carbon dioxide to enter and oxygen to exit.
Guard cells control the opening and closing of stomata.
When water is plenty, stomata open; when water is low, they close.
Open stomata help photosynthesis but cause water loss by transpiration.
Plants in arid regions often have fewer stomata or sunken stomata to save water.

Answer:

Plants need minerals for healthy growth and functions.
Nitrogen helps make proteins, amino acids, and chlorophyll; absorbed as nitrates.
Phosphorus supports ATP energy transfer and root and seed development.
Potassium regulates enzymes, water balance, and stomatal movement.
Calcium strengthens cell walls and helps in cell division.
Without these, plants show deficiencies like poor growth, yellow leaves, and weak stems.

Answer:

Green areas have chlorophyll; white areas do not.
Only chlorophyll can capture sunlight for photosynthesis.
Photosynthesis makes glucose, which is stored as starch in the leaf.
Iodine turns blue-black where starch is present.
So, only green parts turn blue-black; white parts stay brown.
This proves that chlorophyll is essential for making starch in photosynthesis.

Answer:

KOH absorbs carbon dioxide from the air in the bell jar.
The plant with KOH gets no CO2, so photosynthesis cannot make starch.
The control plant gets normal air and performs photosynthesis.
On iodine testing, control leaves turn blue-black; KOH plant leaves do not.
This shows that CO2 is necessary to form glucose and starch.
Conclusion: Carbon dioxide is a must for photosynthesis.

Answer:

Dark keeping causes destarching; stored starch gets used up.
The plant still respires in the dark, using stored food.
After 3 days, leaves have little or no starch left.
Placing it in sunlight allows new photosynthesis to occur.
The new starch formed can be clearly tested with iodine.
This step makes experiments accurate by removing the effect of old starch.

Answer:

High heat increases transpiration and water loss.
To save water, guard cells make stomata close.
Closed stomata reduce CO2 entry, so photosynthesis slows down.
The plant wilts due to low turgor in cells.
Remedies: Give adequate water in the morning; use mulch or shade to reduce water loss.
These steps help reopen stomata and restore photosynthesis.

Answer:

Dust can block stomata, reducing gas exchange.
Less CO2 enters the leaf; photosynthesis becomes slower.
Dust also reduces light reaching chlorophyll.
With less glucose made, there is poor energy and growth.
Plant may show yellowing, weak stems, and fewer flowers/fruits.
Cleaning leaves or reducing pollution helps restore stomatal function and growth.