BIO 112 Lecture Notes Reproductive Systems Types of Reproduction Asexual Reproduction : Budding or fission.Sexual Reproduction : Fusion of haploid gametes, increases genetic variability.Hermaphroditism : Each individual fertilizes the other's eggs, maximizing the number of offspring per copulation.Fertilization External Fertilization : Occurs outside the body, e.g., fish and amphibians.Internal Fertilization : Occurs inside the body, involves eggs.Female Reproductive System Components : Follicles, oviduct, ovaries, corpus luteum, wall of uterus, endometrium (lining of uterus), vagina, uterus, cervix (neck of uterus).Ovaries : Produce oocytes and hormones.Uterine tube : Carries oocyte to uterus.Uterus : Site where embryo develops.Cervix : End of the uterus that opens to the vagina.Vagina : Site for sperm delivery and serves as the birth canal.Female Reproductive System - External Features Features : Mons pubis, clitoris, urethral opening, labium majora, vaginal opening, labium minora, anus.Oogenesis Diploid cell (2n) in embryo undergoes oogenesis.Primary oocyte (2n) : Arrested in prophase of Meiosis I, present at birth.Secondary oocyte (n) : Arrested at metaphase of Meiosis II, released from ovary.Entry of sperm triggers completion of Meiosis II, resulting in an ovum (haploid, n) and a second polar body. First polar body is also produced during Meiosis I.Ovarian Cycle Primary oocyte within follicle → Growing follicles → Mature follicle → Secondary oocyte. Ovulation : Ruptured follicle releases the secondary oocyte.Corpus luteum forms and eventually degenerates if fertilization doesn't occur.Hormonal Control of the Menstrual Cycle Hypothalamus releases GnRH.Anterior pituitary releases FSH and LH.FSH promotes follicle growth.LH surge triggers ovulation.Ovary produces estrogen and progesterone.Estrogen and Progesterone affect the endometrium of the uterus.Ovarian Cycle Phases : Menstrual phase, proliferative phase, secretory phase.Male Reproductive Structures Components : Penis, vas deferens, seminal vesicle, ejaculatory duct, urethra, prepuce (foreskin), testis, scrotum, glans penis, prostate, bulbourethral gland, epididymis.Testes : Produce sperm and hormones.Epididymis : Stores sperm as they finish maturing.Vas deferens : Carries sperm to the urethra.Seminal vesicle : Secretes a fructose-rich fluid (main component of semen).Prostate : Secretes an alkaline fluid that helps activate sperm.Bulbourethral gland : Secretes fluid that neutralizes acid in residual urine.Male Reproductive Structures (Simplified) Testes → Epididymis → Vas deferens → Seminal vesicle → Ejaculatory duct → Urethra. Spermatogenesis Diploid cell (2n) in testis undergoes differentiation and Meiosis I to become a primary spermatocyte (2n).Meiosis I completes, forming secondary spermatocytes (haploid, double chromatids). Meiosis II produces developing sperm cells (haploid, single chromatids), which differentiate into sperm cells (haploid) in the seminiferous tubule. Hormonal Control of Sperm Production Hypothalamus releases releasing hormone.Anterior pituitary releases FSH and LH.FSH stimulates sperm production.LH stimulates androgen production in the testis.Androgens negatively feedback to the hypothalamus and anterior pituitary.Sperm Cell Components : Head (nucleus, acrosome), neck, middle piece (mitochondrion), tail.Fertilization and Implantation Ovulated secondary oocyte is fertilized in the uterine tube by sperm, forming a zygote. Cleavage : Zygote undergoes cleavage (cell division) as it moves towards the uterus.Morula : A solid ball of cells forms.Blastocyst : A hollow ball of cells with an inner cell mass forms and implants in the endometrium around day 7.Implantation and Early Development Trophoblast invades the endometrial epithelium. Inner cell mass develops into the embryonic disc, composed of germ layers: endoderm, mesoderm, and ectoderm. Amnion, amniotic cavity, yolk sac, and chorion develop. Digestion Food Processing Ingestion Digestion : Mechanical and enzymatic breakdown of polymers to monomers.Absorption Elimination Types of Digestion Intracellular Digestion : Food vacuoles.Extracellular Digestion : Gastrovascular cavity.Digestive Systems Incomplete Digestive System : Gastrovascular cavity with a single opening (mouth).Complete Digestive System : A tube with two openings (mouth and anus) and specialized regions.Vertebrate Digestive System Components : Mouth, tongue, salivary glands, oral cavity, pharynx, esophagus, liver, stomach, gall bladder, pancreas, pyloric sphincter, small intestine, large intestine, rectum, anus.Digestive Systems in Different Organisms Earthworm : Mouth, pharynx, esophagus, crop, gizzard, intestine, anus.Grasshopper : Mouth, esophagus, crop, stomach, gastric pouches, intestine, anus.Bird : Mouth, esophagus, crop, stomach, gizzard, intestine, anus.Diet and Digestive System Herbivores : Longer alimentary canal, large cecum.Carnivores : Shorter alimentary canal, small cecum.Herbivore Digestive Systems Nonruminant Herbivore : Esophagus, stomach, small intestine, large intestine, cecum, anus.Ruminant Herbivore : Four-chambered stomach (rumen, reticulum, omasum, abomasum), long small intestine and colon.Nervous Systems Function of Nervous Systems Regulate internal and external responses.Internal : Temperature regulation, ion balance.External : Respond to stimuli (sights, sounds, etc.), movement. Cells of the Nervous System Neurons : Send messages from one to another, transfer signals.Neuroglial (glial) cells : Support and protect neurons.Diversity of Nervous Systems Cnidarian (Hydra) : Nerve net.Flatworm : Brain, nerve cords, associative neurons.Earthworm : Brain, ventral nerve cords.Mollusk : Brain, giant axon.Arthropod : Brain, ventral nerve cords.Echinoderm : Nerve ribs, radial nerve, peripheral nerves.Nerve Net Nerves spread throughout the body. Nerve Ladder Central ganglia (brain) connected to major nerve cords. Transverse cords connect the two nerve cords. Can coordinate movements in certain parts of body (e.g., gliding). Ventral Nerve Cord More centralized nerve cord connected to the brain. Branches occur out from the central nerve cord. Mollusk Nervous System (Octopus) Larger brain, complex eye, more sensory information from extremities. Ganglia in addition to the brain. Vertebrate Nervous System Components : Brain and dorsal nerve cord (spinal cord).Divisions : Central Nervous System (CNS) and Peripheral Nervous System (PNS).Types of Neurons Sensory Neuron : Carries sensory information to the CNS.Relay Neuron (Interneuron) : Connects sensory and motor neurons within the CNS.Motor Neuron : Carries motor commands from the CNS to muscles or glands.Synapses Place where two nerve cells meet. Message has to be passed across the space using neurotransmitters. Respiratory Systems Respiration Overview Breathing: Exchange of O2 and CO 2 in the lungs. Transport of gases by the circulatory system. Servicing of cells within the body tissues. Cellular respiration in mitochondria. Cellular Respiration Equation C6H {12}O6 + 6O 2 \rightarrow 6CO2 + 6H 2O + ATPs Glucose + Oxygen gas yields Carbon dioxide + Water + Energy The Electron Transport Chain is responsible for ATP production Respiratory Surface Characteristics Gas exchange happens between cells (capillary and tissue cells). Surface must be moist (gases dissolve in water before entering the cell). Surfaces must have a large surface area. Types of Respiratory Surfaces Skin (cutaneous) Gills Tracheae Lungs Cutaneous Respiration Gas exchange occurs through the skin. Requires moist skin and capillaries. Tracheal System Network of branching tubes (tracheae) that deliver air directly to body cells (no capillaries needed). Gills Evaginations of the body surface specialized for gas exchange in water. Require efficient ventilation because dissolved oxygen is lower in water than in air. High temperature reduces the amount of dissolved oxygen. Gill Structure and Function Fish ventilate their gills by actively passing water over their gill surfaces. Countercurrent exchange : Blood flows in the opposite direction of water flow, maximizing oxygen uptake.Countercurrent Exchange Countercurrent Flow : Maintains a constant exchange gradient, maximizing oxygen extraction.Concurrent Flow : Exchange gradient diminishes, resulting in less efficient oxygen extraction.Lungs Invaginations of the body surface specialized for gas exchange. Lung Evolution Lungs have increased in complexity from amphibians to mammals. Amphibians : Simple sacs.Mammals : Highly branched with alveoli.Mammalian Respiratory System Components : Nasal cavity, pharynx, larynx, trachea, bronchi, bronchioles, lungs, diaphragm.Alveoli Tiny air sacs in the lungs surrounded by capillaries where gas exchange occurs. Thin layer of water lining the alveolus facilitates gas exchange. Mammalian Breathing Inhalation : Diaphragm contracts (moves down), rib cage expands.Exhalation : Diaphragm relaxes (moves up), rib cage gets smaller.Avian Breathing Air sacs (anterior and posterior) and lungs facilitate unidirectional airflow. Inhalation: Air sacs fill. Exhalation: Air sacs empty; lungs fill. Immunity Immune System Function Allows the body to recognize foreign cells and viruses and defends the body against these. Components of the Immune System Adenoid, tonsil, thymus, lymph nodes, bone marrow, spleen, lymphatic vessels, skin, appendix. Types of Defenses Innate : Always present and ready to function, short response time (hours).Adaptive : Depends on what the body is exposed to, timescale of days.Innate and Adaptive Responses Innate Responses : Physical and chemical barriers, resident microorganisms, phagocytosis, antimicrobial proteins, inflammatory response, fever.Adaptive Responses : Macrophages present antigens, cellular response (helper T cells, cytotoxic T cells), humoral response (B cells, plasma cells, antibodies), memory B cells, memory T cells.Endocrine System Components of the Endocrine System Hypothalamus, pituitary gland, pineal gland, thyroid gland, parathyroid glands, thymus gland, heart, adrenal glands, ovaries (female), testes (male), stomach, pancreas, kidneys, intestines. Endocrine System Function Produces hormones, mostly from endocrine glands, also from parts of the body (e.g., pancreas, hypothalamus). Glands secrete hormones into interstitial fluid, lymph, blood. Hormones are messages. Target Cells All cells are exposed to hormones, but not all cells respond. Only target cells respond due to the presence of receptors that bind to the hormone. Steroid Hormones Derived from cholesterol. Lipid soluble. Enter the cell and bind to an intracellular receptor, forming a hormone-receptor complex. This complex activates a gene, leading to protein synthesis. Mechanism of Steroid Hormone Action Steroid hormone diffuses into the cell. Binds to a receptor in the cytoplasm. Hormone-receptor complex enters the nucleus. Gene activated, leading to RNA and protein synthesis. New protein alters cell activity. Non-Steroid Hormones Made from amino acids/proteins. Not lipid soluble. Bind to a receptor on the outside of the cell. Causes ion channels to open or close, or enzymes to be activated. Mechanism of Non-Steroid Hormone Action Nonsteroid hormone (first messenger) binds to a receptor on the cell membrane. This activates an enzyme that produces cyclic AMP (second messenger). Cyclic AMP activates other enzymes, leading to a final product that alters cell activity. Osmoregulation and Excretion Osmoregulation Organisms actively regulate the amount of solutes in the cells compared to the external environment (osmoregulators). Osmoconformers do not regulate solutes and have the same solute concentration as the environment. Osmoregulation in Freshwater Fish Uptake of water and some ions in food. Osmotic water gain through gills and other parts of the body surface. Uptake of salt ions by gills. Excretion of large amounts of water in dilute urine from kidneys. Osmoregulation in Marine Fish Gain of water and salt ions from food and by drinking seawater. Osmotic water loss through gills and other parts of the body surface. Excretion of salt ions from gills. Excretion of salt ions and small amounts of water in scanty urine from kidneys. Osmoregulation in Terrestrial Organisms Water loss is an issue (respiration, perspiration, urination). Gain water through eating and drinking. Prevent water loss through exoskeleton or skin, and by staying in moist environments. Solute Balance in Humans Salts (Na+, Ca2+, K+, Cl-) determine the movement of water (osmosis) in and out of cells. Perspiration causes water loss and a bit of salt loss. Best way to rehydrate = drink water. Excretion Removal of nitrogenous waste. Breakdown of proteins and nucleic acids produces nitrogenous waste (ammonia). Ammonia build up is toxic. Ammonia Excretion Ammonia is released by aquatic animals (fish, tadpoles, salamanders). Water dilutes and carries the ammonia away. Nitrogenous Waste Products Ammonia (NH_3): Most aquatic animals, including many fishes.Urea (NH2CONH 2): Mammals, amphibians, sharks, some bony fishes. Made in the liver, moved in blood to kidneys.Uric Acid (C5H 4N4O 3): Birds, insects, many reptiles, land snails.Human Excretory System Components : Kidneys, renal artery, renal vein, inferior vena cava, aorta, ureters, urinary bladder, urethra, adrenal glands.Kidneys Blood is pumped to kidneys from heart. Kidneys extract filtrate containing nutrients, O2, salts, glucose, urea. Urea is removed, and most of the other substances are put back into the blood. Kidney Structure Renal cortex, renal medulla, renal pelvis. Nephron : Functional unit of the kidney.Components : Glomerulus, proximal convoluted tubule, distal convoluted tubule, peritubular capillaries, descending limb, ascending limb, nephron loop, collecting duct.Circulatory Systems Function of Circulatory System Transport blood (containing nutrients and oxygen) to cells that need it. Take away waste products and CO2. Open Circulatory System Heart pumps blood out through open vessels to cells. Muscle contractions pump blood around cells. When heart is relaxed, blood enters back into heart. Closed Circulatory System Blood is always kept separate from cells – never direct contact. Blood pumped by heart, through blood vessels, nutrients diffuse out of blood into surrounding cells. Capillary Exchange Diffusion of molecules between blood and tissue cells with interstitial fluid. Components of a Closed Circulatory System Heart, arteries, arterioles, veins, venules, and capillaries. Arteries carry blood away from the heart towards the capillaries. Veins carry blood toward the heart, away from the capillaries. Capillaries facilitate exchange of O2, CO2, and nutrients. Structure of Blood Vessels Artery : Thick walls with endothelium, connective tissue, and smooth muscle.Vein : Thinner walls than arteries, with valves to prevent backflow.Capillary : Thin walls composed of endothelium for easy exchange.Single Circuit Circulatory System 2-chambered heart. Both chambers pump oxygen-poor blood. Fish have gills where blood picks up O2 and drops off CO2. Blood Flow in Fish Heart → Gills (O2 uptake, CO2 release) → Body → Heart. Double Circuit Circulatory System Pulmocutaneous and Systemic system. 3-chambered heart. Amphibians and Reptiles experience some mixing of oxygenated and deoxygenated blood in the ventricle. Double Circuit Circulatory System (Mammals) Two circuits : Pulmonary circuit and Systemic Circuit.Mammals have lungs. 4-Chambered Heart: Atria (receive blood) and Ventricles (pump blood out). Blood Flow in Mammals (simplified) The path of blood flow through the heart is as follows:1. Superior Vena Cava 2. Right Atrium 3. Right Ventricle 4. Pulmonary Artery 5. Capillaries of the Right Lung 6. Capillaries of the Left Lung 7. Pulmonary Vein 8. Left Atrium 9. Left Ventricle 10. Aorta 11. Inferior Vena Cava Pulmonary circuit: Heart → Lungs → Heart. Systemic circuit: Heart → Body → Heart. Musculoskeletal System Skeletons Wide variety of animals have different types of skeletons, but all provide support. Types : Hydrostatic skeleton, Exoskeleton, Endoskeleton.Hydrostatic Skeleton Uses fluid to support the body and for movement. Examples: Earthworms, Cnidarians. Exoskeleton ‘Outside Skeleton’. Arthropods (crayfish, insects……) have exoskeletons made of chitin.Molluscs (snails, clams) have exoskeletons made of calcium carbonate.Exoskeleton grows with organism after molting. Endoskeleton ‘Inside Skeleton’. Hard or Leathery parts of the body inside tissues. Sponges have spicules. Vertebrates have bone or cartilage or both. Muscles and Skeletons Muscles push against skeletal components to create movement. Hydrostatic skeleton : Muscles push on this.Exo/Endoskeleton : Skeletal muscles pull on skeleton.Hydrostatic Skeleton Movement A : Contraction of longitudinal muscles and relaxation of circular muscles to make the setae protrude. This is for adheringB : Contraction of circular muscles and relaxation of longitudinal muscules to withdraw the setae. This is for movementExoskeleton Movement Contraction and Relaxation of joint muscles to move Control of Muscle Contraction Nervous system has to send a message to the muscle (sarcomere) to tell it to contract. Long neurons (axons) run from the spinal cord to the muscle. Neuromuscular Junction Motor neuron axon releases acetylcholine. Acetylcholine binds to receptors on the muscle cell membrane. This generates an action potential that causes muscle contraction. Calcium enables the action potential Synaptic vesicles deliver acetylcholine Knowt Play Call Kai