Topic 3 Organisms exchange substances with their environment Flashcards
How does the size and structure of an organism relate to its surface area to volume ratio (SA)?
As size increases, the surface area to volume ratio (SA) decreases.
Thin, flat, folded, or elongated structures increase the SA.
How is the surface area to volume ratio (SA) calculated?
Divide surface area (side length x side width x number of sides) by volume (length x width x depth).
Example: A cube with sides of 2 cm has a surface area of 24 cm² and a volume of 8 cm³, giving an SA of 3:1.
Why might calculating SA
be advantageous over SA?
Easier and quicker to find.
More accurate for irregularly shaped organisms.
Explain the relationship between SA and metabolic rate.
As SA increases (in smaller organisms), metabolic rate increases because:
Rate of heat loss per unit body mass increases.
Organisms need a higher rate of respiration to release enough heat to maintain a constant body temperature.
What adaptations help facilitate exchange as SA
reduces in larger organisms?
Changes in body shape (e.g., elongated, thin) increase SA
and reduce diffusion distance.
Development of specialized systems (e.g., lungs) increases internal SA, reduces diffusion distance, and maintains a concentration gradient for diffusion through ventilation or good blood supply.
How is the body surface of a single-celled organism adapted for gas exchange?
Thin, flat shape with a large SA
.
Short diffusion distance to all parts of the cell, leading to rapid diffusion of gases like O2 and CO2.
Describe the tracheal system in insects.
Spiracles: Pores that open/close to allow gas exchange.
Tracheae: Large tubes allowing air diffusion.
Tracheoles: Smaller branches permeable to gases, facilitating exchange with cells.
How is the insect tracheal system adapted for gas exchange?
Thin walls of tracheoles for short diffusion distance.
High number of branched tracheoles increase surface area and reduce diffusion distance.
Air-filled tracheae allow fast diffusion.
Abdominal pumping maintains a concentration gradient by changing body pressure.
: What are the structural and functional compromises in terrestrial insects to balance gas exchange and water loss?
Thick waxy cuticle increases diffusion distance, reducing water loss.
Spiracles can open for gas exchange and close to minimize water loss.
Hairs around spiracles trap moist air, reducing the water potential gradient and evaporation.
How are fish gills adapted for gas exchange?
Filaments and Lamellae: Increase surface area for diffusion.
Thin Lamellae Walls: Short diffusion distance between water and blood.
Counter Current Flow: Blood and water flow in opposite directions, maintaining a concentration gradient along the entire length of the gill, ensuring continuous oxygen diffusion.
How are the leaves of dicotyledonous plants adapted for gas exchange?
High density of stomata increases surface area for gas exchange.
Spongy mesophyll contains air spaces, increasing surface area for gas diffusion.
Leaves are thin, reducing diffusion distance.
What adaptations do xerophytic plants have to balance gas exchange and water loss?
Thicker waxy cuticle increases diffusion distance, reducing evaporation.
Sunken stomata in pits, rolled leaves, and hairs trap water vapor, reducing the water potential gradient.
Spines or needles reduce surface area to volume ratio, minimizing water loss.
Describe the gross structure of the human gas exchange system.
Includes the trachea, bronchi, bronchioles, and alveoli.
Alveoli are the primary site of gas exchange, surrounded by capillaries.
What are the essential features of the alveolar epithelium that make it an efficient gas exchange surface?
Flattened cells and one-cell-thick epithelium for short diffusion distance.
Large surface area due to folded structure.
Moist surface allows gases to dissolve and diffuse more efficiently.
Extensive capillary network maintains a concentration gradient.
How does gas exchange occur in the lungs?
Oxygen diffuses from the alveolar air space into the blood, crossing the alveolar epithelium and capillary endothelium, following a concentration gradient.
Carbon dioxide diffuses in the opposite direction, from the blood to the alveolar air space.
Why is ventilation important in gas exchange?
Brings in air with a higher oxygen concentration and removes air with a lower oxygen concentration, maintaining the concentration gradient necessary for efficient gas exchange.
Explain how humans breathe in (inspiration) and breathe out (expiration).
Inspiration: Diaphragm contracts (flattens), external intercostal muscles contract, ribcage moves up/out, thoracic cavity volume increases, pressure decreases, and air moves into lungs.
Expiration: Diaphragm relaxes (moves up), external intercostal muscles relax, ribcage moves down/in, thoracic cavity volume decreases, pressure increases, and air is expelled from lungs.
How do different lung diseases reduce the rate of gas exchange?
Fibrosis: Thickened alveolar tissue increases diffusion distance.
Emphysema: Breakdown of alveolar walls reduces surface area.
Reduced Lung Elasticity: Reduces lung expansion/recoil, lowering oxygen concentration gradients.
How do lung diseases affect ventilation?
Reduced Lung Elasticity (e.g., fibrosis): Lungs expand/recoil less, reducing tidal volume and forced vital capacity.
Narrow Airways (e.g., asthma): Reduces airflow, decreasing forced expiratory volume.
Increased Ventilation Rate: Compensates for reduced oxygen levels in the blood.
Why do people with lung disease experience fatigue?
Cells receive less oxygen, reducing the rate of aerobic respiration and the production of ATP, leading to fatigue.
How can you analyze and interpret data on the effects of pollution, smoking, and other risk factors on lung disease incidence?
Describe overall trends (e.g., correlation between risk factors and disease incidence).
Manipulate data (e.g., calculate percentage change).
Interpret standard deviations (overlap suggests differences are likely due to chance).
Use statistical tests (e.g., correlation coefficient, Student’s t-test, chi-squared test).
How do you evaluate the experimental data leading to statutory restrictions on risk factors for lung diseases?
Analyze data (as above) and assess support for or against restrictions.
Evaluate data collection methods (sample size, participant diversity, control groups, study duration, and context).
Consider other potential risk factors influencing the results.;
What is the difference between correlation and causation?
Correlation: A change in one variable reflects a change in another, identified on a scatter diagram.
Causation: A change in one variable directly causes a change in another.
Note: Correlation does not imply causation; other factors may be involved.
What happens during digestion?
Large, insoluble biological molecules are hydrolyzed into smaller, soluble molecules that can be absorbed across cell membranes into the blood.