b3 and b4 Flashcards
Explain transpiration
Transpiration is the loss of water vapor from the leaves and stems of plants. It primarily occurs through stomata, small pores on the underside of leaves.
Steps of transpiration
- Water absorption by roots (via osmosis from soil)
- Capillary action in xylem (due to cohesion and adhesion of water molecules).
- Water moves upward in the xylem due to the transpiration pull.
- Evaporation of water from mesophyll cells into air spaces in the leaf.
- Diffusion of water vapor out through stomata.
structures involved in transpiration
- Xylem vessels: carry water from roots to leaves.
- Stomata: allow gas exchange and water vapor exit.
- Guard cells: control the opening and closing of stomata.
- Spongy mesophyll: where water evaporates into air spaces.
- Root hairs: absorb water from the soil.
what is cohesion and adhesion
Cohesion: Water molecules stick to each other via hydrogen bonds.
Adhesion: Water sticks to the walls of xylem vessels.
These properties enable capillary action and maintain continuous water columns in xylem.
What is the phloem used for?
The phloem transports organic compounds (mainly sugars) from sources (leaves) to sinks (roots, fruits, flowers). This process is called translocation.
What is the difference between the structure of phloem and xylem
look at the highlighted green question
What is the cross section of a leaf
Cuticle – Waxy layer to stop water loss.
Upper Epidermis – Protects the leaf.
Palisade Layer – Lots of chloroplasts, main site of photosynthesis.
Spongy Layer – Air spaces for gas exchange.
Vein (Vascular Bundle)
Xylem – carries water up.
Phloem – carries sugar down.
Lower Epidermis – Has stomata (tiny pores).
Stomata + Guard Cells – Control gas exchange and water loss.
cross section of a leaf diagram
look at end of page
Explain in depth how water moves up and down in roots
Upward in xylem:
Roots absorb water by osmosis.
Water moves into xylem.
Transpiration (water evaporates from leaves) pulls water up.
Cohesion + adhesion help water move upward.
Root pressure pushes water a little, especially at night.
Explain where transpiration occurs
Mainly on the underside of leaves through stomata.
What ultimately drives transpiration?
The sun — it provides the energy for water to evaporate from mesophyll cells.
Explain What are some of the factors that affects transpiration
Light – More light opens stomata → more water loss.
Temperature – Higher temp = faster evaporation.
Humidity – More humidity = slower transpiration.
Wind – Wind removes moist air → increases transpiration.
Soil Water – Dry soil = less water to lose.
Leaf Size & Stomata – Bigger leaves/more stomata = more transpiration.
Can transpiration ever go to zero?
Yes, if stomata are fully closed
Explain the Adaptations involved in gas exchange in mammals
Large surface area: Many alveoli increase surface area for diffusion.
Thin diffusion surface: Alveolar and capillary walls are one cell thick.
Moist lining: Helps oxygen dissolve and diffuse into blood.
Dense capillary network: Maintains concentration gradients.
Ventilation mechanism: Keeps fresh air moving in and out of lungs.
Explain the steps involved in gas exchanged in mammals
- Air enters alveoli during inspiration.
- Oxygen diffuses from alveoli into capillaries (down its concentration gradient).
- Carbon dioxide diffuses from capillaries into alveoli (also down its gradient).
- Gas exchange occurs via simple diffusion.
- Oxygen is transported by hemoglobin in red blood cells.
Explain the maintenance of concentration gradient
Ventilation ensures high O₂ and low CO₂ in alveoli.
Blood flow (perfusion) ensures low O₂ and high CO₂ in capillaries.
This keeps oxygen diffusing into blood and carbon dioxide out of blood.
Explain the ventilation of lungs
Ventilation = Movement of air into and out of the lungs using muscle contractions to change thoracic volume and pressure.
It ensures: O₂ is supplied to alveoli, CO₂ is removed from alveoli, Concentration gradients are maintained.
List the steps involved inspiration vs expiration
inspiration:
1. Diaphragm contracts → moves downward and flattens.
2. External intercostal muscles contract, pulling the rib cage up and out.
3. Volume of thoracic cavity increases.
4. Pressure inside lungs decreases (below atmospheric pressure).
5. Air flows into lungs from high pressure (outside) to low pressure (inside).
expiration:
1. Diaphragm relaxes → moves upward into dome shape.
2. External intercostal muscles relax, rib cage moves down and in.
3. Volume of thoracic cavity decreases.
4. Pressure inside lungs increases (above atmospheric pressure).
5. Air is pushed out of the lungs.
what is inspiration what is expeiration?
Inspiration = Active (muscle contraction)
Expiration = Passive (relaxation) at rest
During forced expiration (like blowing out), internal intercostal muscles and abdominal muscles contract.
draw a leaf diagram
end page
what do all parts of a leaf do?
Cuticle – Waxy layer, prevents water loss.
Upper Epidermis – Transparent, protects leaf.
Palisade Mesophyll – Packed with chloroplasts → photosynthesis.
Spongy Mesophyll – Air spaces → gas exchange (CO₂ in, O₂ out).
Vein (Vascular bundle): Xylem – Transports water from roots // Phloem – Transports sugars (from photosynthesis).
Lower Epidermis – Protects, contains stomata.
Stomata + Guard Cells – Gas exchange & control water loss.
Roots absorb water and minerals → sent to leaf via xylem.
Leaves perform photosynthesis → sugar sent to roots via phloem.
Identify and explain the parts of a leaf tissue
Cuticle:Waxy, reduces water loss
Epidermis: Outer layer, protection
Palisade mesophyll: Main photosynthesis site (lots of chloroplasts)
Spongy mesophyll: Air spaces for gas exchange
Vascular tissue (vein): Xylem (water) + Phloem (sugar)
Stomata & guard cells: Control gas exchange and water loss
draw and label the parts of the human heart
question 19
Right atrium: Receives deoxygenated blood from body (via vena cava)
Right ventricle: Pumps deoxygenated blood to lungs (via pulmonary artery)
Left atrium: Receives oxygenated blood from lungs (via pulmonary vein)
Left ventricle: Pumps oxygenated blood to body (via aorta)
Aorta: Carries oxygenated blood to body
Pulmonary artery: Carries deoxygenated blood to lungs
Pulmonary vein: Carries oxygenated blood from lungs to heart
Vena cava: Brings deoxygenated blood from body to right atrium
Septum: Separates left and right sides of the heart
Valves (tricuspid, mitral, semilunar): Ensure one-way blood flow – prevent backflow
