Lecture 2 (Part 2) Animal Forms and Functions.pdf

LECTURE 2 (PART 2) ANIMAL FORM: STRUCTURE AND ANATOMY 01 Levels of Organization 02 Body Plans Cellular Level Symmetry Tissue Level Segmentation Organ Level Body Cavity Organ System Level ANIMAL FUNCTION: PH...

LECTURE 2 (PART 2) ANIMAL FORM: STRUCTURE AND ANATOMY 01 Levels of Organization 02 Body Plans Cellular Level Symmetry Tissue Level Segmentation Organ Level Body Cavity Organ System Level ANIMAL FUNCTION: PHYSIOLOGY 01 Homeostasis 05 Excretion 02 Respiration 06 Reproduction: 03 Circulation 04 Digestion HOMEOSTASIS ability of an organism to maintain a stable internal environment despite changes in external conditions Internal environment of the body – refers to the extracellular fluid (interstitial fluid and plasma) that surrounds body cells CONTROL OF HOMEOSTASIS: Feedback system (feedback loop) – a cycle of events in which the status of a body condition is monitored, evaluated, changed, re-monitored, and re-evaluated. Controlled variable – monitored variable (controlled condition), such as body temperature, blood pressure, blood glucose level Stimulus – any disruption that changes a controlled condition FEEDBACK SYSTEM: BASIC COMPONENTS Receptor – a body structure that monitors changes in a controlled condition and sends input to a control center. AFFERENT PATHWAY – information flows toward the control center Control center – sets the narrow range or set point within which a controlled condition should be maintained, evaluates the input it receives from receptors, and generates commands when they are needed. EFFERENT PATHWAY – information flows away from the control center Effector – a body structure that receives output from the control center and produces a response or effect that changes the controlled condition. FEEDBACK SYSTEM: TYPES OF RESPONSE 1. Negative feedback system – reverses a change in a control condition blood pressure (BP) (controlled condition) – force exerted by blood as it presses against the walls of blood vessels baroreceptors (receptor) – pressure- sensitive nerve cells located in the walls of certain blood vessels, detect the higher pressure send nerve impulses (input) to the brain brain (control center) – interprets the impulses and responds by sending nerve impulses (output) to the heart and blood vessels (the effectors) heart and blood vessels (effectors) – heart rate decreases and blood vessels dilate (widen) FEEDBACK SYSTEM: TYPES OF RESPONSE 2. Positive feedback system – strengthen or reinforce a change stretching of the cervix (controlled condition) – force exerted by blood as it presses against the walls of blood vessels stretch-sensitive nerve cells in the cervix (receptor) – monitor the amount of stretching of the cervix send more nerve impulses (input) to the brain brain (control center) – causes the pituitary gland to release the hormone oxytocin (output) into the blood muscles in the wall of the uterus (effectors) – contract more forcefully RESPIRATION process of supplying the body with oxygen, and removing carbon dioxide Three (3) basic steps: Pulmonary ventilation – Breathing process involving the exchange of air between the atmosphere and lungs (O2 in, CO2 out). External (pulmonary) respiration – Gas exchange between alveoli and blood, where blood gains O2 and loses CO2. Internal (tissue) respiration – Gas exchange between blood and tissue cells, where blood loses O2 and gains CO2 during ATP production (cellular respiration). CIRCULATION responsible for transporting nutrients, gases, hormones, and waste products throughout the body. Invertebrates Open Circulatory System – arthropods (insects, spiders) and mollusks (snails), the heart pumps hemolymph (a mix of blood and interstitial fluid) into open cavities where it bathes the organs directly; no veins or capillaries Closed Circulatory System – annelids (earthworms), the blood is enclosed in vessels, flowing in a continuous circuit driven by a heart CIRCULATION Vertebrates Fish – single-loop circulatory system where blood flows from the heart to the gills for oxygenation and then to the rest of the body; two-chambered heart Amphibians – double-loop system where blood is pumped from the heart to the lungs (pulmonary circulation) and then back to the heart before being pumped to the rest of the body (systemic circulation); three-chambered heart CIRCULATION Vertebrates Reptiles – double-loop system; three- chambered heart (except crocodile) with a partially divided ventricle; right and left systemic aortas Mammals – double-loop system; four- chambered heart, supporting higher metabolic rates and sustained energy for complex activities DIGESTION breaking down food into forms that can be absorbed and used by body cells. It also absorbs water, vitamins, and minerals, and it eliminates wastes from the body. Six (6) Digestive Process Ingestion – involves taking foods and liquids into the mouth (eating). Secretion – process by which cells in the walls of GI tract and accessory digestive organs release substances (water, acid, buffers, and enzymes) into the lumen of the GI tract. Motility – ability of the GI tract to mix food and secretions and move them toward the anus through alternating contractions and relaxations of smooth muscle in its walls. Digestion – breaking down ingested food into small molecules for use by body cells. It consists of two parts: Mechanical Digestion – involves cutting and grinding food with teeth and churning in the stomach and small intestine to mix food with digestive enzymes. DIGESTION Chemical Digestion – hydrolysis, where large molecules (carbohydrates, lipids, proteins, and nucleic acids) are split into smaller molecules by digestive enzymes produced by salivary glands, the stomach, pancreas, and small intestine. Absorption – movement of digested products from the lumen of the GI tract into the blood or lymph. Once absorbed, these substances circulate to cells throughout the body. Some substances, such as vitamins, ions, cholesterol, and water, can be absorbed without digestion. Defecation – process by which wastes, indigestible substances, bacteria, cells from the GI tract lining, and unabsorbed digested materials are expelled from the body through the anus. The eliminated material is known as feces or stool.  EXCRETION process by which waste products, particularly nitrogenous wastes, are removed from the body to maintain homeostasis and prevent toxic build-up. Simpler organisms rely on diffusion, while more complex animals use specialized organs like kidneys, Malpighian tubules, or nephridia to manage and excrete waste efficiently. REPRODUCTION the biological process involved in the formation of offspring, ensuring the continuation of a species. Asexual, single parent produces offspring that are genetically identical to the parent Sexual, involves the fusion of male and female gametes (sperm and egg) to create genetically diverse offspring Automixis, where the egg undergoes a form of meiosis, leading to the production of diploid offspring from a diploid egg without fertilization by sperm Apomixis, does not involve meiosis; the egg develops directly into an embryo