Class 7 Science Chapter 7 - Transportation in Animals and Plants
1. What is the main function of the
circulatory system in animals?
Answer:
The main function of the circulatory system is to transport oxygen, nutrients,
hormones, and waste products throughout the body. It helps maintain homeostasis
and supports various bodily functions.
2. Name the components of blood and
their functions.
Answer:
- Red
Blood Cells (RBCs):
Carry oxygen from the lungs to body cells and transport carbon dioxide
back to the lungs.
- White
Blood Cells (WBCs):
Play a key role in the immune system, fighting infections and foreign
invaders.
- Platelets: Help in blood clotting to
prevent excessive bleeding.
- Plasma: The liquid component that
carries nutrients, hormones, and waste products.
3. Describe the process of
transpiration in plants.
Answer:
Transpiration is the process by which water evaporates from the surface of
leaves through small openings called stomata. This loss of water creates a
suction effect that pulls water upward from the roots through the xylem,
facilitating nutrient transport and helping to cool the plant.
4. What are xylem and phloem, and
what roles do they play in plants?
Answer:
- Xylem: Transports water and dissolved
minerals from the roots to the leaves. It consists of dead cells that form
a continuous tube for efficient transport.
- Phloem: Transports food (sugars)
produced during photosynthesis from the leaves to other parts of the plant.
It is made up of living cells that allow bidirectional flow.
5. Explain the difference between an
open and a closed circulatory system.
Answer:
- Open
Circulatory System:
Blood flows freely in the body cavity (hemocoel) and directly bathes
organs. Found in organisms like insects and crustaceans.
- Closed
Circulatory System:
Blood is confined within blood vessels, allowing for more efficient
transport and regulation of blood flow. Found in vertebrates like humans.
6. How do stomata regulate gas
exchange in plants?
Answer:
Stomata are small openings on the leaf surface that can open and close to
regulate gas exchange. When stomata are open, carbon dioxide enters the leaf
for photosynthesis, and oxygen and water vapor exit. Guard cells surrounding
the stomata control their opening based on environmental conditions, such as
light and humidity.
7. What role does the heart play in
the circulatory system?
Answer:
The heart is a muscular organ that pumps blood throughout the body. It
maintains circulation by contracting and relaxing, ensuring that oxygenated
blood is delivered to tissues and deoxygenated blood is sent to the lungs for
reoxygenation.
8. Describe the significance of
photosynthesis in relation to transportation in plants.
Answer:
Photosynthesis produces glucose, which is vital for plant energy and growth.
The glucose is transported through the phloem to different parts of the plant
where it is needed. Additionally, oxygen produced during photosynthesis is
released into the atmosphere, supporting life on Earth.
9. How do plants adapt their
transportation systems in arid environments?
Answer:
In arid environments, plants may develop adaptations such as:
- Modified
stomata that close during the hottest parts of the day to reduce water
loss.
- Thickened
cuticles on leaves to minimize evaporation.
- Extensive
root systems to maximize water uptake.
10. Why is the circulatory system
important for maintaining homeostasis in animals?
Answer:
The circulatory system is essential for maintaining homeostasis as it regulates
temperature, pH levels, and the concentrations of various substances in the
body. By transporting nutrients and waste products effectively, it helps ensure
that cells function optimally, adapting to changes in the environment.
11. What is the role of capillaries
in the circulatory system?
Answer:
Capillaries are tiny blood vessels that connect arteries and veins. They have
thin walls that allow for the exchange of oxygen, nutrients, and waste products
between blood and surrounding tissues. This exchange is crucial for cellular
metabolism.
12. What is translocation in plants?
Answer:
Translocation is the process by which nutrients, primarily sugars, are moved
from the leaves (where they are produced during photosynthesis) to other parts
of the plant (like roots, stems, and fruits) through the phloem. This process
ensures that all parts of the plant receive the necessary energy for growth and
development.
13. How does blood flow in the human
heart?
Answer:
Blood flow in the human heart follows this sequence:
- Deoxygenated
blood returns from the body to the right atrium via the superior and
inferior vena cavae.
- It
moves into the right ventricle and is pumped to the lungs through the
pulmonary artery for oxygenation.
- Oxygenated
blood returns from the lungs to the left atrium via the pulmonary veins.
- It
flows into the left ventricle, which pumps it to the rest of the body
through the aorta.
14. What factors can affect the rate
of transpiration in plants?
Answer:
The rate of transpiration can be affected by several factors:
- Light
Intensity:
Higher light levels increase transpiration due to increased
photosynthesis.
- Temperature: Warmer temperatures lead to
faster evaporation of water from leaves.
- Humidity: Lower humidity levels increase
transpiration rates.
- Wind: Wind can remove moisture from
around leaves, enhancing transpiration.
15. Explain the process of blood
clotting.
Answer:
Blood clotting is a complex process involving platelets and clotting factors.
When a blood vessel is injured:
- Platelets
adhere to the site and release chemicals that attract more platelets.
- The
platelets form a temporary plug.
- Clotting
factors in plasma activate a series of reactions, ultimately converting
fibrinogen (a soluble protein) into fibrin (an insoluble protein) that
forms a mesh, stabilizing the clot and preventing further bleeding.
16. How do plants ensure efficient
water uptake through roots?
Answer:
Plants use several adaptations to ensure efficient water uptake:
- Root
Hairs:
Tiny extensions of root cells increase surface area for water absorption.
- Mycorrhizal
Fungi:
Some plants form symbiotic relationships with fungi, which extend the root
system and improve nutrient and water absorption.
- Active
Transport:
Roots actively absorb minerals, creating a concentration gradient that
helps draw water from the soil.
17. Why is oxygen important for
cellular respiration in animals?
Answer:
Oxygen is crucial for cellular respiration, a process that occurs in cells to
produce energy. During respiration, glucose is broken down in the presence of
oxygen to produce ATP (adenosine triphosphate), which is the energy currency of
the cell. Without oxygen, cells cannot efficiently produce enough energy,
leading to anaerobic respiration, which is less efficient and produces lactic
acid in animals.
18. What is the significance of
vascular tissue in plants?
Answer:
Vascular tissue (xylem and phloem) is vital for:
- Transport: Xylem transports water and
nutrients, while phloem distributes food.
- Support: Xylem provides structural
support due to lignified walls, allowing plants to grow taller and reach
sunlight.
- Growth
and Development:
Facilitates growth by moving nutrients to growing parts of the plant.
19. How does the circulatory system
contribute to thermoregulation in humans?
Answer:
The circulatory system helps regulate body temperature by adjusting blood flow
to the skin. During hot conditions, blood vessels near the skin surface dilate
(vasodilation), allowing more blood to flow and releasing heat. Conversely, in
cold conditions, blood vessels constrict (vasoconstriction) to conserve heat.
20. What adaptations do some aquatic
plants have for transportation?
Answer:
Aquatic plants often have:
- Air
Spaces:
Aerenchyma (air-filled spaces) in stems and leaves to help with buoyancy
and gas exchange.
- Flexible
Stems:
Allow movement with water currents, reducing damage.
- Floating
Leaves:
To maximize sunlight exposure and facilitate gas exchange.
21. What is the primary role of the
heart in the circulatory system?
Answer:
The primary role of the heart is to pump blood throughout the body. It
maintains circulation by contracting rhythmically to ensure that oxygenated
blood reaches the tissues and organs while returning deoxygenated blood to the
lungs for reoxygenation.
22. How do guard cells regulate the
opening and closing of stomata?
Answer:
Guard cells surround each stoma and control its size. When the plant has
adequate water, guard cells take in potassium ions, causing them to swell and
open the stomata. Conversely, when water is scarce, guard cells lose potassium,
become flaccid, and close the stomata to minimize water loss.
23. Explain the difference between
aerobic and anaerobic respiration.
Answer:
- Aerobic
Respiration:
Occurs in the presence of oxygen, producing a significant amount of energy
(ATP) from glucose, along with carbon dioxide and water as byproducts.
- Anaerobic
Respiration:
Occurs in the absence of oxygen, producing less energy and resulting in
byproducts like lactic acid (in animals) or ethanol and carbon dioxide (in
yeast).
24. Describe how the structure of
red blood cells is related to their function.
Answer:
Red blood cells (RBCs) have a biconcave shape, which increases their surface
area for gas exchange. They contain hemoglobin, a protein that binds oxygen.
The flexible and thin structure allows RBCs to navigate through tiny
capillaries and efficiently transport oxygen to tissues.
25. What is the role of the spleen
in the circulatory system?
Answer:
The spleen plays multiple roles, including filtering blood, recycling iron from
hemoglobin, and storing red blood cells and platelets. It also helps fight
infections by producing white blood cells and filtering out bacteria and other
pathogens from the blood.
26. How does water transportation
differ in trees compared to smaller plants?
Answer:
In trees, water transportation occurs through a more complex and extensive
xylem system, capable of supporting taller structures and long-distance
transport. In smaller plants, the xylem may be less developed, and water
transport relies more on capillary action and proximity to the soil.
27. Explain how nutrients are
absorbed by roots.
Answer:
Nutrients are absorbed by roots through:
- Diffusion: Passive movement of nutrients
from higher concentration in the soil to lower concentration in root
cells.
- Active
Transport:
Energy is used to move minerals against their concentration gradient into
root cells, especially for essential nutrients like nitrates and
phosphates.
28. What is the significance of
having a double circulatory system in mammals?
Answer:
A double circulatory system, consisting of the pulmonary and systemic circuits,
allows for efficient separation of oxygenated and deoxygenated blood. This
separation improves oxygen delivery to tissues, enhances metabolic efficiency,
and maintains higher blood pressure in systemic circulation, facilitating
better nutrient and gas exchange.
29. How do plants respond to excess
water in the soil?
Answer:
In response to excess water, plants may:
- Close
their stomata to reduce transpiration and water loss.
- Develop
aerenchyma to facilitate oxygen transport in waterlogged conditions.
- If
conditions persist, they may exhibit symptoms of root rot or other
stress-related responses.
30. What adaptations help desert
plants minimize water loss?
Answer:
Desert plants have several adaptations, including:
- Thick,
waxy cuticles:
Reduce water loss through evaporation.
- Deep
root systems:
Access water from deeper soil layers.
- Modified
leaves:
Often reduced to spines to minimize surface area and reduce transpiration.
- Water
storage tissues:
Some cacti store water in their stems for use during dry periods.
31. What is the function of the
lymphatic system in the human body?
Answer:
The lymphatic system helps maintain fluid balance by collecting excess fluid
(lymph) from tissues and returning it to the bloodstream. It also plays a
crucial role in the immune system by transporting white blood cells and
filtering out pathogens through lymph nodes.
32. Describe the role of hemoglobin
in red blood cells.
Answer:
Hemoglobin is a protein in red blood cells that binds to oxygen in the lungs
and transports it to tissues throughout the body. It also helps carry carbon
dioxide back to the lungs for exhalation. Hemoglobin’s iron content is what
allows it to bind oxygen effectively.
33. What are the three types of
blood vessels, and how do they differ in structure and function?
Answer:
- Arteries: Thick, muscular walls to
withstand high pressure; carry oxygenated blood away from the heart.
- Veins: Thinner walls with valves to
prevent backflow; carry deoxygenated blood back to the heart.
- Capillaries: Very thin walls (one cell thick)
that facilitate the exchange of gases, nutrients, and waste between blood
and tissues.
34. How do trees transport water
from the roots to the leaves?
Answer:
Trees transport water through the xylem using a combination of root pressure,
capillary action, and transpiration pull. As water evaporates from the stomata
in leaves, it creates negative pressure that pulls more water upward through
the xylem from the roots.
35. What is the significance of root
pressure in plants?
Answer:
Root pressure is the pressure generated in the roots due to the active
absorption of water and minerals from the soil. This pressure helps push water
up through the xylem, especially during nighttime when transpiration rates are
low, and it plays a role in the overall movement of water in the plant.
36. Explain how the circulatory
system adapts during exercise.
Answer:
During exercise, the circulatory system adapts by:
- Increasing
heart rate to pump more blood and deliver more oxygen to muscles.
- Dilating
blood vessels in active muscles to enhance blood flow.
- Redirecting
blood from less active organs to the muscles, ensuring they receive the
nutrients and oxygen needed for increased activity.
37. What are the main components of
the plant vascular system?
Answer:
The main components of the plant vascular system are:
- Xylem: Responsible for the transport
of water and minerals from roots to leaves.
- Phloem: Responsible for the transport
of organic nutrients (especially sugars) from leaves to other parts of the
plant.
38. How does the structure of leaves
facilitate photosynthesis and transpiration?
Answer:
Leaves have a large surface area, thin structure, and are often equipped with
chloroplasts for photosynthesis. The presence of stomata allows for gas
exchange, enabling carbon dioxide to enter for photosynthesis while allowing
water vapor to exit during transpiration. This design maximizes both processes.
39. What role do hormones play in
the transportation processes of plants?
Answer:
Hormones in plants regulate various growth and developmental processes,
including:
- Auxins: Promote cell elongation and
influence the direction of growth in response to light (phototropism) and
gravity (gravitropism).
- Gibberellins: Stimulate growth and
flowering.
- Cytokinins: Promote cell division and
growth, affecting nutrient transport.
40. How does the body regulate blood
sugar levels?
Answer:
The body regulates blood sugar levels primarily through the actions of hormones
such as insulin and glucagon:
- Insulin: Produced by the pancreas, it
helps lower blood sugar levels by facilitating the uptake of glucose into
cells for energy and storage.
- Glucagon: Also produced by the pancreas,
it raises blood sugar levels by promoting the conversion of stored
glycogen in the liver back into glucose when needed.
