9.1: Animal Resources

Question 1

Why do animals need to feed?

Answer 1

Animals need to feed to:
1. Obtain chemical energy for cellular processes (e.g., ATP production).
2. Acquire organic molecules as building blocks for biosynthesis.
3. Gain essential nutrients that the body cannot synthesize (e.g., some amino acids, fatty acids, vitamins, and minerals).

Question 2

What are the modes of animal nutrition?

Answer 2

1. Partial Autotrophy: Some invertebrates rely on symbiosis with photosynthetic protists (e.g., corals and zooxanthellae).
   
   2. Herbivory: Eating plants or algae.
   3. Carnivory: Eating other animals.
   4. Omnivory: Consuming both plants and animals regularly.

Question 3

: What are the four stages of food processing in animals

Answer 3

1. Ingestion: Taking in food (e.g., bulk feeding, filter feeding, substrate feeding, fluid feeding).
   
   2. Digestion:
      ○ Mechanical digestion (e.g., chewing).
      ○ Chemical digestion (e.g., breaking down polymers into monomers: proteins → amino acids, carbohydrates → sugars).
   3. Absorption: Nutrients are absorbed into cells from the digestive tract.
   4. Excretion: Undigested materials and waste are eliminated.

Question 4

How is the mammalian digestive system organized

Answer 4

1. Mouth: Ingestion and initial digestion (mechanical and chemical).
   
   2. Stomach: Chemical digestion with gastric juice (HCl and pepsin).
   3. Small Intestine: Main site of digestion and nutrient absorption; enzymes from pancreas and bile from the liver aid digestion.
   4. Large Intestine: Absorbs water; contains symbiotic bacteria that ferment undigested polysaccharides.
   5. Rectum: Stores and expels waste.

Question 5

What are the differences between open and closed circulatory systems?

Answer 5

Open Circulatory System:
○ Fluid (hemolymph) bathes body cells directly.
○ Found in arthropods and some mollusks.
○ Less efficient at transporting nutrients and oxygen.
2. Closed Circulatory System:
○ Blood is confined to vessels, separate from interstitial fluid.
○ Found in annelids, cephalopods, and vertebrates.
○ More efficient for high metabolic demands.

Question 6

What are the advantages and disadvantages of water and air as respiratory media?

Answer 6

1. Water:
   ○ Advantages: Supports gills and helps dissolve gases.
   ○ Disadvantages: Low oxygen concentration; requires more energy to move water over respiratory surfaces.
   
   2. Air:
      ○ Advantages: Higher oxygen concentration; easier to ventilate.
      Disadvantages: Risk of water loss through evaporation; requires internal respiratory surfaces to conserve moisture.

Question 7

: What are some respiratory organs in animals?

Answer 7

1. Gills: Found in aquatic animals (e.g., fish, marine worms); large surface area for gas exchange in water.
   
   2. Tracheae: Found in insects; network of tubes delivering air directly to tissues.
   3. Lungs: Found in terrestrial vertebrates; localized respiratory organs with large surface areas for gas exchange.
      Skin: Some amphibians and earthworms use their skin as a respiratory surface.