Topic 3 Organisms exchange substances with their environment

Question 1

How does the size and structure of an organism relate to its surface area to volume ratio (SA)?

Answer 1

As size increases, the surface area to volume ratio (SA) decreases.
Thin, flat, folded, or elongated structures increase the SA.

Question 2

How is the surface area to volume ratio (SA) calculated?

Answer 2

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.

Question 3

Why might calculating SA
be advantageous over SA?

Answer 3

Easier and quicker to find.
More accurate for irregularly shaped organisms.

Question 4

Explain the relationship between SA and metabolic rate.

Answer 4

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.

Question 5

What adaptations help facilitate exchange as SA
reduces in larger organisms?

Answer 5

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.

Question 6

How is the body surface of a single-celled organism adapted for gas exchange?

Answer 6

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.

Question 7

Describe the tracheal system in insects.

Answer 7

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.

Question 8

How is the insect tracheal system adapted for gas exchange?

Answer 8

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.

Question 9

: What are the structural and functional compromises in terrestrial insects to balance gas exchange and water loss?

Answer 9

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.

Question 10

How are fish gills adapted for gas exchange?

Answer 10

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.

Question 11

How are the leaves of dicotyledonous plants adapted for gas exchange?

Answer 11

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.

Question 12

What adaptations do xerophytic plants have to balance gas exchange and water loss?

Answer 12

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.

Question 13

Describe the gross structure of the human gas exchange system.

Answer 13

Includes the trachea, bronchi, bronchioles, and alveoli.
Alveoli are the primary site of gas exchange, surrounded by capillaries.

Question 14

What are the essential features of the alveolar epithelium that make it an efficient gas exchange surface?

Answer 14

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.

Question 15

How does gas exchange occur in the lungs?

Answer 15

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.

Question 16

Why is ventilation important in gas exchange?

Answer 16

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.

Question 17

Explain how humans breathe in (inspiration) and breathe out (expiration).

Answer 17

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.

Question 18

How do different lung diseases reduce the rate of gas exchange?

Answer 18

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.

Question 19

How do lung diseases affect ventilation?

Answer 19

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.

Question 20

Why do people with lung disease experience fatigue?

Answer 20

Cells receive less oxygen, reducing the rate of aerobic respiration and the production of ATP, leading to fatigue.

Question 21

How can you analyze and interpret data on the effects of pollution, smoking, and other risk factors on lung disease incidence?

Answer 21

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).

Question 22

How do you evaluate the experimental data leading to statutory restrictions on risk factors for lung diseases?

Answer 22

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.;

Question 23

What is the difference between correlation and causation?

Answer 23

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.

Question 24

What happens during digestion?

Answer 24

Large, insoluble biological molecules are hydrolyzed into smaller, soluble molecules that can be absorbed across cell membranes into the blood.

Question 25

Describe the digestion of starch in mammals

Answer 25

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.

Question 26

How are disaccharides digested in mammals?

Answer 26

Membrane-bound Disaccharidases: Hydrolyze disaccharides into monosaccharides.
Maltase: Maltose → Glucose + Glucose.
Sucrase: Sucrose → Fructose + Glucose.
Lactase: Lactose → Galactose + Glucose.

Question 27

How are lipids digested in mammals, including the role of bile salts?

Answer 27

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).

Question 28

Describe the digestion of proteins in mammals.

Answer 28

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.

Question 29

Why are membrane-bound enzymes important in digestion?

Answer 29

Located on the cell membranes of epithelial cells lining the ileum, they hydrolyze molecules at the site of absorption, maintaining concentration gradients.

Question 30

How are amino acids and monosaccharides absorbed in mammals?

Answer 30

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.

Question 31

How are lipids absorbed in mammals, including the role of micelles?

Answer 31

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.

Question 32

What precautions should be followed when performing a dissection of an animal or plant system?

Answer 32

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.

Question 33

What ethical considerations should be taken into account when dissecting animals?

Answer 33

Consideration: It is morally wrong to kill animals solely for dissection, so use animals already humanely killed for other purposes (e.g., meat production).

Question 34

How do you prepare a temporary mount of plant tissue for observation with an optical microscope?

Answer 34

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.

Question 35

What are the rules for scientific drawings?

Answer 35

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.

Question 36

How do you set up a potometer to measure the rate of transpiration?

Answer 36

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.

Question 37

How is a potometer used to measure the rate of transpiration?

Answer 37

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.

Question 38

What are the limitations of using a potometer to measure the rate of transpiration?

Answer 38

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.

Question 39

How do different environmental variables affect the rate of transpiration?

Answer 39

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.

Question 40

What are the key rules for dissection in biological studies?

Answer 40

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.