Animal Form, Function, and Physiology: Study Notes

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Animal Form and Function

Convergent Evolution and Body Form

Animals living in similar environments often evolve similar body forms, even if they are not closely related. This phenomenon is known as convergent evolution.

Example: Penguins (birds), seals (mammals), and tuna (fish) all have streamlined bodies that reduce drag while swimming, despite their different evolutionary origins.

Structural Adaptations for Absorption

Efficient absorption in the digestive system is achieved through increased surface area.

Key Features: Branching, folds, and villi in the intestines maximize surface area for nutrient absorption.

Coordination of Body Functions

The endocrine system coordinates vertebrate body functions via chemical signals (hormones).

Hormones are released into the bloodstream and affect distant target organs.

Tissues and Exchange Surfaces

Most exchange surfaces in multicellular organisms are lined by epithelial tissue.

Simple squamous epithelium is a flat, single layer ideal for rapid diffusion (e.g., alveoli, glomerulus).

Muscle Tissue Types

All muscle types contain actin (thin filament) and myosin (thick filament) for contraction. They differ in structure and function:

Muscle Type	Striation	Control	Nuclei	Special Features
Skeletal	Striated	Voluntary	Multinucleated	Not intercalated
Smooth	Non-striated	Involuntary	Uninucleate	Not intercalated
Cardiac	Striated	Involuntary	Uninucleate	Intercalated discs

Adipose Tissue

Adipose cells are specialized for storing fats in animals.

Heat Exchange Mechanisms

Evaporation: Animals cool themselves by jumping into water or splashing water, promoting heat loss via evaporation.

Thermoregulation: Ectotherms vs. Endotherms

Ectotherms (e.g., lizards, snakes) gain heat from the environment and are more active at higher temperatures.
Endotherms generate heat via metabolism.
In cold environments, ectotherms become less active.

Homeostasis and Temperature Regulation

Homeostasis maintains stable internal conditions. Blood vessels respond to temperature changes:

Vasoconstriction: Reduces blood flow to the skin in cold, minimizing heat loss.
Vasodilation: Increases blood flow to the skin in heat, promoting cooling via evaporation.

Nervous System Signals

Signals are fast, rapid, and travel via dedicated routes (neurons).

Bone Structure

Composed of thick ground substance, 100% collagen fibers, and minerals (mainly calcium).

Animal Nutrition and Digestion

Basal Metabolic Rate (BMR) and Energy Balance

BMR is the energy expended at rest over 24 hours. Additional calories are used for activities.

To avoid weight gain: Calories intake = Calories expenditure
If intake > expenditure: Excess stored as fat (weight gain)
If intake < expenditure: Weight loss

Calculation Example:

Total calories consumed: 3,600
BMR: 2,000
Calories available for activity: 1,600
If activity burns 400 cal/hr: hours
If activity burns 200 cal/hr: hours
If activity burns 20 cal/hr: hours (excess stored as fat)

Vitamins and Minerals

Vitamin K is synthesized in the small intestine by Escherichia coli (mutualistic bacteria).
Vitamins are organic; minerals are inorganic nutrients.
Folic acid is required during pregnancy to prevent neural tube defects.

Absorption in the Digestive System

Absorption: Movement of digested nutrients across membranes into the body.
Highest in the small intestine due to large surface area (villi and microvilli).

Digestive Enzymes and Processes

Region	Carbohydrate Digestion	Protein Digestion	Fat Digestion
Mouth	Amylase: starch to glucose/disaccharides	No digestion	No digestion
Stomach	Paused	Pepsin: proteins to di/tripeptides	No digestion
Duodenum	Amylase/disaccharidases: disaccharides to monosaccharides	Dipeptidases: peptides to amino acids	Lipase: fats to fatty acids & glycerol

Pepsin is secreted as inactive pepsinogen to prevent self-digestion of stomach tissue.
Lipase digests fats; inhibitors can treat high blood fat levels.
Megaloblastic anemia is caused by low vitamin B12.
Constipation results from excess water absorption in the large intestine.
Stomach cells are protected from acid by thick mucus and rapid cell division.

Peristalsis

Propulsion of food through the gastrointestinal tract by smooth muscle contractions.

Hepatic Portal Vein

After absorption, nutrients enter the bloodstream via the hepatic portal vein (not an artery).

Saliva and Mucus

Mucus in saliva contains glycoproteins, making food slippery for easier swallowing.

Circulation and Gas Exchange

Blood Pressure and Cardiac Function

Blood pressure in the aorta is highest due to left ventricular contraction (systole).
Systole: Contraction phase; Diastole: Relaxation phase.
When atria contract (systole), ventricles relax (diastole), and vice versa.
Cardiac Output (CO): Amount of blood pumped per minute.

Formula:

Cardiac Output = Stroke Volume × Heart Rate

Example calculation:

Stroke Volume = 50 ml
Heart Rate = 80 beats/min
Cardiac Output = ml/min

Hormonal Regulation

Aldosterone: Maintains homeostasis (especially salt and water balance).
Erythropoietin: Stimulates red blood cell production.

Surfactant and Respiratory Distress Syndrome (RDS)

Surfactant prevents alveolar collapse during exhalation.
Premature infants may lack surfactant, leading to RDS.

Blood Flow and Capillaries

Capillaries have the slowest blood velocity due to their large total cross-sectional area (arranged in parallel).
Capillaries are not damaged by high arterial pressure because of this parallel arrangement.
The left ventricle has the thickest wall to pump blood throughout the body.

Electrocardiogram (ECG)

ECG records the electrical activity of the heart, used to assess heart rhythm.

Hypertension

Defined as blood pressure > 140 mmHg systolic and > 90 mmHg diastolic.

Additional Info

Master the route of blood flow: Superior/inferior vena cava → right atrium → right ventricle → pulmonary artery → lungs → pulmonary vein → left atrium → left ventricle → aorta → body capillaries.
Magnesium trisilicate can relieve acid reflux pain; omeprazole blocks acid production for long-term relief.