Topic 22- Respiration/Excretion

What is the difference between cellular respiration and organismic respiration?

Cellular respiration uses O₂ to produce ATP inside cells; organismic respiration moves O₂ into cells and CO₂ out.

How do small organisms (<1 mm thick) exchange gases?

By simple diffusion, no special transport systems needed.

What four respiratory structures have evolved in larger animals?

Skin, gills, tracheal tubes, lungs.

What are the three key requirements for all respiratory surfaces?

Thin walls, large surface area, moist environment (plus blood supply except in insects).

How do bony fish maximize O₂ extraction from water?

By using countercurrent exchange in their gills.

How does the insect tracheal system deliver gases?

Through trachea and tracheoles, delivering O₂ and CO₂ directly to each cell.

What is the main downside of the tracheal system in insects?

High water loss.

What is the pathway of air during mammalian respiration?

Nostrils → Nasal cavity → Pharynx → Larynx → Trachea → Bronchi → Bronchioles → Alveoli.

What role does the diaphragm play in breathing?

It contracts during inhalation (creating negative pressure) and relaxes during exhalation.

What is the function of alveoli?

Site of gas exchange; surrounded by capillaries for efficient O₂/CO₂ diffusion.

Which brain structures control breathing, and what do they regulate?

Medulla oblongata (depth and rhythm, based on CO₂ levels), and Pons (rate of breathing).

How does CO₂ concentration affect breathing?

High CO₂ → low pH → deeper breathing to expel more CO₂.

What are osmoconformers?

Organisms that are isosmotic with their environment (mostly marine invertebrates).

What are osmoregulators?

Organisms that maintain internal osmolarity different from the environment (freshwater/terrestrial animals, marine vertebrates).

What is the biggest water challenge for terrestrial vertebrates?

Preventing dehydration.

What are three ways terrestrial animals obtain water?

Drinking water, eating moist food, producing metabolic water through cellular respiration.

What adaptations help reduce water loss in terrestrial animals?

Body coverings, nocturnal behavior, concentrating urine.

What process breaks down proteins and nucleic acids?

Deamination in the liver.

Why is ammonia toxic?

It disrupts cellular functions even at low concentrations.

What are the three forms of nitrogenous waste?

Ammonia, urea, and uric acid.

Which organisms excrete ammonia, and what are its properties?

Aquatic animals; very toxic, requires lots of water, low energy to produce.

Which organisms excrete urea, and what are its properties?

Mammals, amphibians, marine fish; moderately toxic, water-soluble, moderate energy cost.

Which organisms excrete uric acid, and what are its properties?

Birds, insects, land snails; low toxicity, water-insoluble, very high energy cost.

What are the four basic steps of excretion at the nephron?

Filtration → Reabsorption → Secretion → Excretion.

What happens during filtration at the nephron?

Blood plasma is filtered; small molecules pass into nephron, large molecules stay in blood.

What happens during reabsorption in the nephron?

Useful substances like glucose and ions are reabsorbed back into the bloodstream.

What happens during secretion in the nephron?

Ions, toxins, and wastes are actively transported into the nephron for removal.

What happens during excretion from the nephron?

The processed filtrate (urine) leaves the body.

What is the path of urine through the human excretory system?

Kidney → Ureter → Urinary bladder → Urethra.

What is the main structural organization of a nephron?

Glomerulus → Bowman’s capsule → Proximal tubule → Loop of Henle → Distal tubule → Collecting duct.

How does the Loop of Henle conserve water?

Longer loops allow more water reabsorption.

Compare and contrast types of respiratory systems.

Feature	Skin/Surface Respiration	Gills (Bony Fish)	Tracheal System (Insects)	Lungs (Mammals)
Main Organ	Body surface	Gills	Tracheal tubes	Lungs
Environment	Moist	Aquatic	Terrestrial	Terrestrial
Mechanism	Diffusion through skin	Countercurrent exchange	Direct delivery to cells	Bulk air flow
Special Structures	Thin skin + capillaries	Gill lamellae + blood vessels	Trachea, tracheoles	Bronchi, alveoli, diaphragm
Water Loss	High (moisture needed)	Moderate	High	Controlled
Efficiency	Low (small animals only)	High (very efficient)	Moderate	Very high

Sequence mammalian respiration.

Pathway of Air:

1. Nostrils →

2. Nasal cavity →

3. Pharynx →

4. Larynx →

5. Trachea →

6. Bronchi →

7. Bronchioles →

8. Alveoli →

9. Bloodstream.

Inhalation: Diaphragm contracts → negative pressure pulls air in.
Exhalation: Diaphragm relaxes → air pushed out.

Hypothesize and diagnose the impact of variability on mammalian respiration.

Variable/Change	Hypothesized Impact	Diagnosis/Effect
High CO₂ concentration	Blood pH drops → breathing depth increases	Hyperventilation to expel CO₂
Damage to diaphragm	Inhalation impaired → difficulty breathing	Respiratory distress
Punctured pleural membrane	Lung collapses → reduced oxygen intake	Pneumothorax
Obstructed trachea	Blocked airflow → no gas exchange	Asphyxiation risk
Cold/dry air exposure	Drying out of airways → irritation/infection	Increased mucus production

Compare and contrast types of osmoregulation.

Feature	Osmoconformers	Osmoregulators
Definition	Internal osmolarity matches environment	Maintain internal balance regardless of environment
Typical Organisms	Most marine invertebrates	Freshwater animals, terrestrial animals, marine vertebrates
Energy Cost	Low	High
Strategy	Passive	Active (energy expenditure)
Challenge	Fluctuating external osmolarity	Maintaining homeostasis in different environments

Compare and contrast types of nitrogenous waste.

Type of Waste	Produced By	Toxicity	Energy Cost	Water Solubility	Notes
Ammonia (NH₃)	Aquatic animals (e.g., fish)	Very high	Low	Very high	Requires lots of water for dilution
Urea	Mammals, amphibians, marine fish	Moderate	Moderate	High	Safer form, needs some water
Uric Acid	Birds, insects, land snails	Low	Very high	Insoluble	Excreted as a paste, conserves water

Sequence the process of excretion.

Steps in Excretion (at Nephron):

1. Filtration: Plasma filtered into nephron; small molecules pass, large stay.

2. Reabsorption: Nutrients and useful ions reabsorbed into bloodstream.

3. Secretion: Active transport of wastes into nephron.

4. Excretion: Urine exits body through kidneys → ureters → bladder → urethra.

"Fresh Rain Soaks Earth."

Hypothesize and diagnose the impact of variability on excretion.

Variable/Change	Hypothesized Impact	Diagnosis/Effect
Dehydration	Increased water reabsorption → concentrated urine	Risk of kidney stones, low urine output
High salt intake	Need to excrete more ions → increased workload on kidneys	Hypertension, kidney stress
Kidney failure	Filtration impaired → waste accumulation in blood	Uremia, death without dialysis
Damage to Loop of Henle	Less water reabsorption → dilute urine	Risk of dehydration
Obstruction in ureter	Urine backs up into kidneys → pressure damage	Hydronephrosis