Nutrition in Animals Practice Questions

Correct answer: Ingestion → Digestion → Absorption → Assimilation → Egestion

Holozoic nutrition systematically begins with ingestion, where food is taken into the body. This is followed by digestion to break down complex molecules, absorption into body fluids, assimilation where cells utilize these nutrients, and finally egestion to expel undigested waste.

Correct answer: Pseudopodia

Amoeba utilizes pseudopodia, also known as 'false feet', which are temporary extensions of its cell membrane and cytoplasm. These structures encircle a food particle, fusing together to engulf it into a specialized compartment called a food vacuole. Once inside, intracellular enzymes break down the trapped food.

Correct answer: Parasitic nutrition

Parasitic nutrition involves an organism living on or inside another host organism to obtain ready-made food, often causing harm to the host in the process. Saprotrophs feed on dead and decaying matter, while holozoic organisms ingest solid organic food material. Ticks are ectoparasites, whereas tapeworms function as endoparasites.

Correct answer: Food vacuole

In Paramecium, food is swept into a specific cell mouth called the cytostome by cilia and is enclosed within a food vacuole. Inside this vacuole, digestive enzymes break down complex nutrients into simpler compounds that diffuse directly into the cytoplasm. The contractile vacuole, by contrast, is purely responsible for osmoregulation.

Correct answer: Abomasum

The abomasum is the fourth and final chamber of the ruminant stomach, functioning analogously to the monogastric human stomach by secreting hydrochloric acid and proteases like pepsin. The rumen and reticulum host symbiotic microbes that ferment complex plant fibers. The omasum primarily absorbs water and recycled minerals from the fermented food.

Correct answer: The rumen contains symbiotic bacteria and protozoa that produce the enzyme cellulase.

Humans lack the specific enzyme cellulase required to break down the beta-glycosidic bonds found in cellulose, meaning it passes through our tracts as dietary fiber. Ruminating animals harbor a massive ecosystem of symbiotic anaerobic microorganisms in their rumen that ferment cellulose into volatile fatty acids. This process allows them to extract substantial energy from fibrous plant matter.

Correct answer: Long, sharp canines

Carnivores have highly developed, pointed canine teeth adapted for gripping, piercing, and tearing tough muscle tissue. Their incisors are used for stripping flesh from bone, while specialized premolars and molars called carnassial teeth slice food like scissors. Herbivores, by contrast, feature flat molars designed to grind tough plant cell walls.

Correct answer: Caecum

The caecum is a pouch-like structure located at the junction of the small and large intestines. In hindgut fermenters like rabbits and horses, a massive, functional caecum houses the symbiotic bacteria needed to ferment cellulose. In humans, who do not rely on hindgut fermentation, the caecum is highly reduced, and its blind end forms the vermiform appendix.

Correct answer: Body cells using absorbed nutrients to build protoplasm, repair tissue, and make energy

Assimilation is the intracellular process where simple, absorbed nutrients (like amino acids and glucose) are taken up by body cells and incorporated into their own structures or oxidized for energy. Absorption simply describes the transport of nutrients out of the gut lumen and into circulation. Digestion is the breakdown phase, and egestion is the elimination of solid wastes.

Correct answer: Removal of undigested waste from alimentary canal

Egestion is strictly the elimination of undigested, unabsorbed dietary residue from the digestive tract as feces. Excretion, conversely, is the metabolic removal of chemical waste products generated inside cells, such as urea or carbon dioxide. Bile secretion is a functional digestive process rather than a waste elimination step.

Correct answer: Typhlosole

The typhlosole is a prominent internal dorsal fold of the intestinal wall found in earthworms that significantly increases the surface area available for nutrient absorption. Humans use villi and microvilli to achieve the same surface-area expansion. Malpighian tubules are excretory organs found in insects, not absorptive structures.

Correct answer: Spider

Spiders capture prey, immobilize it with venom, and then inject powerful digestive enzymes directly into the victim's body tissues. These enzymes liquefy the prey's internal organs externally, allowing the spider to suck up the pre-digested fluid nutrient soup. Hydra performs a combination of extracellular and intracellular digestion within its central gastrovascular cavity.

Correct answer: Grinding food mechanically in place of teeth

Because birds and earthworms lack teeth, they rely on a heavily muscularized organ called the gizzard to crush and grind down coarse food particles. Birds often swallow tiny pebbles or grit that remain in the gizzard to assist this mechanical milling process. The crop is the separate structure utilized for temporary food storage.

Correct answer: Pancreas

The pancreas exhibits a dual functional design. Its exocrine tissue produces pancreatic juice rich in enzymes like trypsin, lipases, and amylases delivered to the duodenum via ducts. Its endocrine tissue, organized into the Islets of Langerhans, secretes hormones like insulin and glucagon directly into the bloodstream.

Correct answer: Hepatic juice

Hepatic juice (bile) is an alkaline, green-yellow fluid synthesized by hepatocytes and stored in the gallbladder. Although it lacks chemical digestive enzymes, its component bile salts act as natural detergents to break large lipid globules down into micro-droplets. This mechanical emulsification exponentially expands the surface area for water-soluble lipases to operate.

Correct answer: Cyclosis

Cyclosis, or cytoplasmic streaming, is the continuous, directed rotation of the fluid cytoplasm within a cell. In Amoeba, this movement transports the digesting food vacuole along a regular path through the cell body, allowing absorbed nutrients to distribute evenly to all cellular regions. Exocytosis is the terminal step where the vacuole dumps indigestible waste at the cell periphery.

Correct answer: Starches

Human saliva contains the enzyme salivary amylase (ptyalin), which initiates the chemical breakdown of complex starches into simpler disaccharides like maltose while food is being chewed. Protein digestion does not begin until food encounters gastric juices in the stomach, and primary lipid breakdown occurs in the small intestine.

Correct answer: Chief cells

Chief cells (zymogenic cells) located within the gastric pits secrete the zymogen pepsinogen. When pepsinogen encounters the highly acidic environment created by the hydrochloric acid from parietal cells, it cleaves into its active, protein-cutting form, pepsin. Goblet cells focus on secreting protective mucus lines.

Correct answer: Large intestine

While the small intestine absorbs virtually all organic nutrients and the bulk of water, the large intestine is responsible for absorbing remaining water, mineral salts, and certain vitamins (like Vitamin K) synthesized by resident microflora. This continuous extraction transforms liquid waste into compacted, solid feces ready for elimination.

Correct answer: Fluid-feeding nutrition

Fluid feeders extract liquid nutrients directly from a host plant or animal source, utilizing specialized piercing or sucking mouthparts (like a mosquito's proboscis). Frugivores consume whole fruits, detritivores feed on dead particulate organic matter, and macrophagous organisms ingest large, solid food masses.