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.
Describe the digestion of starch in mammals
Amylase: Produced by salivary glands/pancreas, hydrolyzes starch into maltose.
Maltase: Membrane-bound enzyme in the ileum hydrolyzes maltose into glucose.
Reaction: Hydrolysis of glycosidic bonds.
How are disaccharides digested in mammals?
Membrane-bound Disaccharidases: Hydrolyze disaccharides into monosaccharides.
Maltase: Maltose → Glucose + Glucose.
Sucrase: Sucrose → Fructose + Glucose.
Lactase: Lactose → Galactose + Glucose.
How are lipids digested in mammals, including the role of bile salts?
Bile Salts: Produced by the liver, emulsify lipids into smaller droplets, increasing the surface area for lipase activity.
Lipase: Made in the pancreas, hydrolyzes triglycerides into monoglycerides and fatty acids (hydrolysis of ester bonds).
Describe the digestion of proteins in mammals.
Endopeptidases: Hydrolyze internal peptide bonds, producing smaller peptides.
Exopeptidases: Hydrolyze terminal peptide bonds, releasing single amino acids.
Dipeptidases: Hydrolyze peptide bonds in dipeptides into two amino acids.
Why are membrane-bound enzymes important in digestion?
Located on the cell membranes of epithelial cells lining the ileum, they hydrolyze molecules at the site of absorption, maintaining concentration gradients.
How are amino acids and monosaccharides absorbed in mammals?
Co-transport Mechanism:
Na+ actively transported from epithelial cells to blood by Na+/K+ pump.
Na+ enters epithelial cells down its concentration gradient, bringing glucose against its concentration gradient via a co-transporter protein.
Glucose moves into the blood by facilitated diffusion.
How are lipids absorbed in mammals, including the role of micelles?
Micelles: Contain bile salts, monoglycerides, and fatty acids, making them more soluble in water and facilitating their transport to epithelial cells in the ileum.
Absorption: Monoglycerides and fatty acids diffuse into epithelial cells, where triglycerides are reformed, coated with proteins to form chylomicrons, and then exocytosed into lymphatic vessels.
What precautions should be followed when performing a dissection of an animal or plant system?
Precautions:
Cover cuts with waterproof dressing.
Cut away from the body on a hard surface.
Use sharp blades and carry scalpels with the blade protected/pointing down.
Wear disposable gloves, disinfect hands, surfaces, and equipment.
Dispose of gloves, towels, and organs in separate bags/bins.
Work in well-ventilated areas if dealing with poisonous chemicals/toxins.
What ethical considerations should be taken into account when dissecting animals?
Consideration: It is morally wrong to kill animals solely for dissection, so use animals already humanely killed for other purposes (e.g., meat production).
How do you prepare a temporary mount of plant tissue for observation with an optical microscope?
Steps:
Add a drop of water to a glass slide.
Obtain a thin section of the specimen and place it on the slide.
Stain with iodine/potassium iodide for starch observation.
Lower the coverslip at an angle using a mounted needle, avoiding air bubbles.
What are the rules for scientific drawings?
Drawings should be accurate, clear, and to scale.
Use clear, continuous lines without shading.
Include a magnification scale (e.g., x400).
Label with straight, uncrossed lines.
How do you set up a potometer to measure the rate of transpiration?
1.Cut a shoot underwater at a slant to prevent air entering the xylem.
2.Assemble the potometer with the capillary tube submerged in water.
Insert the shoot underwater, ensuring the apparatus is airtight.
Dry the leaves, acclimatize the shoot, and shut the reservoir tap.
Form an air bubble by briefly removing the capillary tube from the water.
How is a potometer used to measure the rate of transpiration?
Record the initial position of the air bubble.
Measure the distance moved by the bubble in a set time (e.g., 1 minute).
Calculate the volume of water uptake using the formula πr² (cross-sectional area) x distance moved.
Calculate the rate of water uptake by dividing the volume by time.
What are the limitations of using a potometer to measure the rate of transpiration?
Water uptake may not equal transpiration as water is also used for support/turgidity and photosynthesis, and produced during respiration.
The rate of water movement in the shoot may differ from the whole plant, as the shoot lacks roots and the xylem cells are very narrow.
How do different environmental variables affect the rate of transpiration?
Light Intensity: Increases transpiration as stomata open for photosynthesis.
Temperature: Increases transpiration by providing kinetic energy to water molecules.
Wind Intensity: Increases transpiration by blowing away water molecules, lowering the water potential of air around stomata.
Humidity: Decreases transpiration by raising the water potential of the surrounding air.
What are the key rules for dissection in biological studies?
Always use sharp, clean instruments.
Cut away from your body.
Wear protective equipment and ensure proper disposal of biological waste.
Be mindful of ethical concerns when selecting specimens.
