Biology Revision Notes PDF

Classification of animals - Arboreal – is primates that live in trees What is Vertebrate - Vertebrates are animals that have a backbone or spinal column. This group includes a wide variety of animals, such as mammals, birds, reptiles, amphibians, and fish. The backbone is made up of individu...

Classification of animals - Arboreal – is primates that live in trees What is Vertebrate - Vertebrates are animals that have a backbone or spinal column. This group includes a wide variety of animals, such as mammals, birds, reptiles, amphibians, and fish. The backbone is made up of individual vertebrae that encase and protect the spinal cord, which is a crucial part of the nervous system. Vertebrates are part of the subphylum Vertebrata within the phylum Chordata. The backbone provides structural support and allows for greater mobility and flexibility compared to invertebrates (animals without a backbone). Vertebrates also typically have a well-developed brain enclosed in a skull, and they often exhibit complex behaviours and adaptations that contribute to their survival and reproduction. What is Invertebrate - Invertebrates are animals that lack a backbone or spinal column. This group encompasses a vast diversity of species, including insects, arachnids (like spiders and scorpions), crustaceans (such as crabs and shrimp), mollusks (like snails and octopuses), annelids (earthworms and leeches), and many others. Invertebrates make up the majority of animal species on Earth and exhibit a wide range of forms and lifestyles. They can be found in almost every environment, from deep ocean floors to the highest mountain peaks. Unlike vertebrates, invertebrates may have various other structures for support and protection, such as exoskeletons (as in insects and crustaceans) or hydrostatic skeletons (as in worms). Their adaptability and diversity are key reasons why invertebrates are so successful in different habitats What is Endothermic - Endothermic refers to organisms that regulate and maintain their body temperature internally through metabolic processes. These organisms are often called "warm-blooded" because they can generate heat internally and keep their body temperature relatively constant, regardless of the external environment. In endothermic animals, such as mammals and birds, this temperature regulation is achieved through various physiological mechanisms, including shivering to generate heat, sweating or panting to cool down, and adjusting metabolic rates. This ability to maintain a stable internal temperature allows them to inhabit a wide range of environments and remain active even in extreme conditions. The term "endothermic" can also be used in chemistry to describe reactions that absorb heat from their surroundings. However, when referring to animals, it specifically pertains to their internal temperature regulation What is Exothermic - Exothermic organisms, also known as ectotherms or cold-blooded animals, rely on external sources of heat to regulate their body temperature. Unlike endotherms (warm-blooded animals) that generate their own heat, ectotherms, such as reptiles, amphibians, and fish, depend on external heat sources like the sun or their surroundings to maintain a suitable body temperature. Their body temperature fluctuates with environmental conditions Endoskeleton Exoskeleton Fish - vertebrate 3 groups of fish - Agnatha (don't worry about them) - Cartilage fish (sharks, dog fish) science term: Chondrichthyes - Bony fish science term: Osteichthyes The Circulatory System 1. Overview of the Circulatory System Primary Role: The circulatory system is responsible for transporting oxygen and nutrients to cells, as well as removing waste products like carbon dioxide and urea. Number of Cells in Mammals: An average mammal has about 30 trillion cells. Cell Needs: Each cell requires oxygen to process nutrients and eliminate waste. Over 93% of cells rely on the circulatory system to achieve this. Proximity to Blood Vessels: For cells to exchange gases and waste, they must be within millimetres of blood vessels. Interstitial Fluid Definition: Interstitial fluid is the liquid that fills the spaces between cells in tissues. Functions: ○ Acts as a medium for the exchange of nutrients, gases, and waste between blood vessels and cells. ○ Part of extracellular fluid, which also includes blood plasma and lymph. ○ Helps maintain fluid balance, supports cellular function, and allows the diffusion of substances. Lymphatic System Role in Fluid Balance:  ○ The lymphatic system returns excess interstitial fluid to the bloodstream, preventing tissue swelling (edema). Immune Function: ○ Filters lymph through lymph nodes and other lymphoid organs. ○ Detects and responds to pathogens and harmful substances, supporting the immune system. Nutrient Absorption: ○ Aids in the absorption of fats and fat-soluble vitamins (A, D, E, K) from the digestive system via lacteals (specialized lymphatic vessels). ○ Transports these nutrients into the bloodstream. Immune Response: ○ Facilitates the movement of immune cells (like lymphocytes) throughout the body, enabling a coordinated immune response. The human heart 1. Heart Structure and Function Atria (Upper Chambers): ○ Right Atrium: Receives deoxygenated blood from the body via the superior and inferior vena cavae. ○ Left Atrium: Receives oxygenated blood from the lungs via the pulmonary veins. Ventricles (Lower Chambers): ○ Right Ventricle: Pumps deoxygenated blood to the lungs via the pulmonary artery for oxygenation. ○ Left Ventricle: Pumps oxygenated blood to the body via the aorta. It has thicker walls because it needs to generate higher pressure to pump blood throughout the entire body. Valves: ○ Tricuspid Valve: Between the right atrium and right ventricle, prevents backflow into the atrium during ventricular contraction. ○ Pulmonary Valve: Between the right ventricle and pulmonary artery, prevents backflow into the ventricle after blood is pumped to the lungs. ○ Mitral (Bicuspid) Valve: Between the left atrium and left ventricle, prevents backflow into the atrium during ventricular contraction. ○ Aortic Valve: Between the left ventricle and aorta, prevents backflow into the ventricle after blood is ejected into the aorta. 2. Conduction System of the Heart Sinoatrial (SA) Node: The natural pacemaker of the heart, located in the right atrium. It initiates electrical impulses that set the rhythm of the heartbeat.  Atrioventricular (AV) Node: Located at the junction between the atria and ventricles. It receives electrical signals from the SA node and delays them slightly to ensure the atria have time to empty before the ventricles contract. Bundle of His & Purkinje Fibers: Specialized fibers that carry electrical impulses from the AV node through the ventricles, ensuring coordinated contraction. 3. Cardiac Muscle Specialized Muscle: Cardiac muscle is involuntary, striated, and fatigue-resistant. Cells are interconnected by intercalated discs, which contain gap junctions for rapid impulse transmission and desmosomes for structural support. Autorhythmicity: Cardiac muscle cells can generate their own electrical impulses, maintaining the heart’s rhythm. 4. Blood Flow through the Heart Superior Vena Cava: Returns deoxygenated blood from the upper body to the right atrium. Inferior Vena Cava: Returns deoxygenated blood from the lower body to the right atrium. Aorta: Carries oxygenated blood from the left ventricle to the rest of the body. Pulmonary Artery: Carries deoxygenated blood from the right ventricle to the lungs for oxygenation. 5. Cardiac Cycle Phases Systole (Contraction Phase): ○ Atrial Systole: The atria contract, pushing blood into the ventricles. ○ Ventricular Systole: The ventricles contract, pumping blood into the pulmonary artery (right ventricle) and aorta (left ventricle). Diastole (Relaxation Phase): ○ The heart muscle relaxes, allowing the chambers to refill with blood. 6. Heart's Electrical Conduction and Control Pacemaker: The SA node initiates the electrical impulses. AV Node Delay: Slight delay in the AV node ensures that the atria empty completely before ventricular contraction. Impulse Pathway: SA Node → Atria → AV Node → Bundle of His → Purkinje Fibers → Ventricles. 7. Blood Flow Regulation through Valves Atrioventricular (AV) Valves: Tricuspid and Mitral valves ensure blood flows from atria to ventricles.  Semilunar Valves: Pulmonary and Aortic valves ensure blood is pumped out of the ventricles without backflow. 8. Ventricle to Pulmonary Artery Right Ventricle: Contracts and pumps deoxygenated blood into the pulmonary artery for oxygenation in the lungs. 9. Heart Valve Functions Tricuspid & Mitral Valves: Prevent backflow from ventricles into atria. Semilunar Valves (Pulmonary & Aortic): Prevent backflow into the ventricles during diastole. 10. Heart Contraction Control (Summary) SA Node: Initiates electrical impulses causing atrial contraction. AV Node: Delays impulse before passing it to the ventricles. Bundle of His & Purkinje Fibers: Coordinate ventricular contraction. Systole: Ventricular contraction pumps blood to lungs and body. Diastole: Heart relaxes, chambers refill with blood. Blood, Blood Vessels, and Other Systems (Open,Closed) Blood Red Blood Cells (Erythrocytes): ○ Main function: Transport oxygen from the lungs to the tissues and carry carbon dioxide away from tissues to the lungs for exhalation. ○ Haemoglobin: A protein inside red blood cells that binds with oxygen and carbon dioxide, facilitating gas exchange. ○ Enucleate: Red blood cells are enucleate (lack a nucleus), which allows more room for haemoglobin and enables a larger surface area for gas exchange. Mammals are the only animals with enucleate red blood cells. Leukocytes (White Blood Cells): ○ Granulocytes: White blood cells with granules that contain enzymes to fight infections (e.g., bacteria). They are involved in immune responses during infections and allergic reactions. ○ Agranulocytes: White blood cells that mediate immunity by releasing antibodies, targeting cancerous or infected cells, and removing dead cells. Vacuole: Small air pocket (gap) inside a cell. Often involved in storage and transport functions.  Antibodies (Immunoglobulins): Y-shaped proteins produced by the immune system to neutralize harmful pathogens like bacteria and viruses by binding to them and facilitating their elimination. Summary: Blood consists of water, plasma, and cells. Erythrocytes (red blood cells) contain haemoglobin and transport oxygen. Leukocytes (white blood cells) provide defense against pathogens through phagocytosis and antibody production. Blood Vessels Types of Blood Vessels: ○ Arteries: Carry oxygenated blood away from the heart (except pulmonary artery). ○ Arterioles: Smaller arteries that lead into capillaries. ○ Capillaries: Tiny blood vessels where gas, nutrient, and waste exchange occurs. ○ Venules: Small veins that collect blood from capillaries. ○ Veins: Carry deoxygenated blood back to the heart (except pulmonary vein). Vasodilation and Vasoconstriction: ○ Vasodilation: Blood vessels widen when the body is too warm to release heat. ○ Vasoconstriction: Blood vessels constrict when the body is too cold to conserve heat. Capillary Structure: ○ Thin walls: One cell thick endothelium, allowing efficient exchange of gases, nutrients, and waste. ○ Fenestrations (gaps): Increase the exchange rate by allowing substances to pass more easily between blood and tissues. ○ Low blood pressure: Results in slow blood flow, facilitating the exchange of gases and nutrients. Urea: A waste product formed from the breakdown of proteins in the liver. It is filtered by the kidneys and excreted in the urine. Avascular vs Vascular: ○ Avascular: Areas with no blood vessels (e.g., cartilage), which heal more slowly. ○ Vascular: Areas with blood vessels (e.g., skin), which heal faster. Venous Flow: ○ Veins carry blood at low pressure and velocity. ○ Venous walls are thinner than arterial walls because they don't need to withstand high pressure. ○ One-way valves in veins prevent backflow, ensuring blood flows only toward the heart. ○ Muscle Contractions: Muscles surrounding veins help push blood through them by increasing local pressure. Summary: Arteries, arterioles, and veins have similar structures, with different proportions of muscle, elastic, and endothelial tissue to suit their functions. Arterial flow is driven by ventricular pressure. Venous flow is generated by muscle contractions. Capillaries have very thin walls to enable efficient exchange. Pulmonary Circulation Pulmonary Vein: Carries oxygen-rich blood from the lungs to the heart. Closed Circulatory Systems: ○ Blood circulates within blood vessels and doesn't leave the system. ○ Double Circulatory System: Humans have a double circulatory system, meaning blood passes through two circuits: one for oxygenation (pulmonary circuit) and one for systemic circulation (delivering oxygen to tissues). Circulatory Systems in Different Organisms - all closed circulatory systems Fish (Single Circulation): ○ Fish have a single circulatory system, where blood passes through the heart once per cycle. ○ Blood is pumped through the ventral aorta to the gills for oxygenation, then to the dorsal aorta to the rest of the body. ○ Active species, such as salmon and tuna, have larger hearts for higher oxygen demand. ○ Lungfish: Have a double arrangement for oxygenating blood through both gills and lungs, but still have a two-chambered heart. Amphibians (Three-Chambered Heart): ○ Amphibians like frogs have a three-chambered heart, with two atria and one ventricle. ○ They use skin and lungs for gas exchange. Oxygenated blood from the lungs or skin is returned to the left atrium, and deoxygenated blood from the body returns to the right atrium. ○ The mixed blood (oxygenated and deoxygenated) enters the single ventricle. Cephalopods (Octopus and Squid): ○ Cephalopods have three hearts: two branchial hearts pump blood to the gills for oxygenation, while the systemic heart pumps oxygenated blood to the body. Open Circulatory System Invertebrates: Many invertebrates, such as arthropods (e.g., insects, spiders), have an open circulatory system.  ○ Blood (called hemolymph) is pumped into open spaces (hemocoel), bathing the organs directly. ○ Pores (Ostia): In arthropods, blood enters the heart through these pores and is pumped into the body cavity. ○ Blood flows freely between tissues and organs without being confined to vessels. Closed circulatory system A closed circulatory system efficiently transports blood through a network of vessels, supporting higher metabolic needs. It consists of heart, arteries, veins, and capillaries, with blood being pumped through a series of loops (single or double). It ensures efficient oxygenation, precise regulation of blood flow, and rapid nutrient and waste exchange. Double circulation is typical in mammals, birds, and amphibians, with separate circuits for the lungs (pulmonary) and the rest of the body (systemic). Lung structure and function - Why Do We Have Lungs? Adaptation for Efficient Gas Exchange: Mammals, unlike many simpler organisms, have evolved to have skin that minimizes water loss, making it unsuitable for gas exchange via diffusion across the surface. The internal organs, including the lungs, evolved as specialized gas exchange surfaces. These allow efficient oxygen supply to cells while minimizing water loss through evaporation. The lungs are designed to bring oxygen to the bloodstream and remove carbon dioxide effectively. Structure of the Respiratory System: 1. Nasal Cavity: ○ Air enters through the nose, where it is filtered, warmed, and moistened by the goblet cells secreting mucus. ○ This helps trap dust and pathogens, preventing them from reaching the lungs. 2. Trachea: ○ The trachea (windpipe) is a rigid tube that carries air to the lungs. ○ It is reinforced with C-shaped cartilage rings that prevent it from collapsing.  ○ Ciliated epithelium lines the trachea, and cilia beat in a coordinated manner to move mucus, dust, and microorganisms up and out of the respiratory tract (a process known as the mucociliary escalator). 3. Bronchi: ○ The trachea divides into the left and right bronchi, which lead to each lung. ○ The bronchi further divide into smaller bronchioles, ending in the alveoli. 4. Alveoli: ○ Tiny air sacs where gas exchange occurs. ○ Alveoli are surrounded by a dense network of capillaries to facilitate the exchange of gases (oxygen and carbon dioxide). Alveoli Adaptations for Gas Exchange: 1. Large Surface Area (SA): ○ The millions of alveoli in the lungs provide an enormous surface area for gas exchange, maximizing the area where oxygen and carbon dioxide can diffuse. 2. Thin Walls (One Cell Thick): ○ The alveolar walls are made up of a single layer of epithelial cells, reducing the diffusion distance between the air and blood, thus speeding up gas exchange. 3. Moist Lining: ○ The inner surface of the alveoli is covered in moist fluid (from the cytoplasm of alveolar cells), allowing gases like oxygen and carbon dioxide to dissolve and diffuse more easily. 4. Good Blood Supply: ○ Each alveolus is surrounded by capillaries that maintain a constant flow of blood, ensuring that oxygen is rapidly transported away from the lungs and carbon dioxide is brought to the alveoli for removal. This helps to maintain a steep diffusion gradient The Role of Red Blood Cells (RBCs) in Gas Exchange: Red blood cells are roughly the same size as the diameter of capillaries, ensuring that they pass through capillaries in a single file, maximizing contact with the alveolar wall. This close contact allows for efficient oxygen diffusion from the alveoli into the red blood cells (RBCs), as the similar diameters: ○ Increase surface area for gas exchange. ○ Minimize the diffusion distance. ○ Slow down blood flow, allowing more time for gas exchange. ○ Maintain a concentration gradient for both oxygen (in the alveoli) and carbon dioxide (in the blood). Lung Ventilation: Ventilation refers to the movement of air into and out of the lungs. It is driven by muscular activity and the inspiration and expiration phases. Inspiration (Breathing In): External intercostal muscles contract, lifting the ribs upwards and outwards. The diaphragm contracts and flattens, increasing the volume of the thoracic cavity. As the volume of the chest increases, the pressure inside the lungs drops below atmospheric pressure, causing air to flow in through the airways. Expiration (Breathing Out): External intercostal muscles relax, and the ribs move downwards and inwards. The diaphragm relaxes and moves upwards into a dome shape. As the volume of the thoracic cavity decreases, the air pressure inside the alveoli becomes greater than atmospheric pressure, causing air to flow out of the lungs. Role of External Intercostal Muscles in Inspiration: The external intercostal muscles contract during inspiration, pulling the ribs upwards and outwards. This increases the volume of the thoracic cavity, which lowers the pressure inside the lungs, allowing air to flow in from outside the body. How Ventilation Increases the Rate of Gas Exchange: Ventilation helps to maintain a high concentration of oxygen in the alveoli and a low concentration of carbon dioxide, creating a steep diffusion gradient. This ensures that oxygen continues to diffuse into the blood and carbon dioxide is rapidly removed from the blood into the alveoli to be exhaled. Other Mechanisms that Maintain a Diffusion Gradient in the Lungs: 1. Blood Circulation: ○ The constant blood flow through the capillaries ensures that oxygen is continuously carried away from the alveoli, and carbon dioxide is brought to the alveoli for removal. ○ This keeps the concentration gradient for oxygen and carbon dioxide high, allowing for efficient gas exchange. 2. Alveolar Wall (One Cell Thick): ○ The one-cell-thick walls of the alveoli minimize the distance gases have to diffuse, allowing for more efficient exchange of gases between the alveolar air and the blood. Summary The lungs provide a large surface area for gas exchange, which is crucial for maintaining oxygen and carbon dioxide levels in the body.  Alveoli, with their thin walls, moist surface, and dense capillary network, are perfectly adapted for this exchange. Ventilation (air moving in and out of the lungs) and blood flow through the capillaries ensure that the necessary concentration gradients for oxygen and carbon dioxide are maintained for efficient gas exchange. Gas exchange surfaces Microscopic organisms: e.g Amoeba Very large surface area to volume ratio Can exchange gases with environment sing their external Large multicellular organisms: e.g Human/Fish Much smaller surface area to volume ratio Additional gas exchange surface area required: ○ Lungs ○ Gills ○ Tracheae Have four things in common: Large surface area to volume ratio Thin Short diffusion pathways Steep concentration gradients Short diffusion pathway - Alveolar and blood capillary walls only 1 cell thick Squamous epithelium cells - very thin - used to form alveolar and blood capillary walls Steep concentration gradient - Partial pressure of O2 in lungs > in capillaries Partial pressure of CO2 in lungs < in capillaries Therefore O2 diffuses into blood CO2 diffuses into lungs Blood constantly moving so oxygenated blood taken away from the lungs and deoxygenated blood taken to the lungs Fish gills are structures at the base of their skulls on both sides. These are often buccal powered. The fish swallows water which is then passed over the gill surfaces. Bony fish - the water goes in to the mouth when opened and then squeezed past the gill surfaces as the mouth is closed Gills have a large surface area - (many lamellae with lots of gill plates) with a short diffusion pathway - walls of lamellae made for squamous epithelium. Large blood supply to the surface of lamellae. Steep concentration gradient - pp of O2 in water always higher than in capillaries & pp of CO2 in water always lower than in capillaries. Many fish use a countercurrent system to achieve this. Amphibian - Anura oxygen uptake Amphibian - Anura CO2 removal So what does this mean? The skin is the main organ to eliminate carbon dioxide throughout the lifespan of the frog while the lungs take up most of the oxygen in the adult but this varies. Gills start off as important, giving 40% of the oxygen but decrease with each stage of life Amphibians - The skin, gills and lungs are all major gas exchange systems depending on the different stages of a frog’s life. This fits their life cycle of starting off entirely aquatic before moving onto land.. Frog lungs Aves respiratory system - Birds have large air sacs that then collect the air that comes in before then passing it through the respiratory system The air passes down the trachea and bronchus to the posterior air sac. From there it is pumped to the anterior air sac and expelled. The exchange occurs through the parabronchi The Kidneys The kidneys play a crucial role in maintaining homeostasis by regulating the balance of water, salts, and waste products in the body. They achieve this through a series of highly efficient processes, ensuring the blood remains free of toxins and excess substances. Structure of the Kidney: Kidneys are always found in pairs. Renal refers to the kidney (e.g., renal artery, renal vein). Ureter: A tube that transports urine from the kidneys to the bladder for storage, then it is expelled through the urethra. The kidney is divided into several key regions: Renal Pelvis: The central cavity that collects urine from the collecting ducts and funnels it to the ureter. Renal Medulla: The inner region of the kidney, made up of renal pyramids, which contain the loops of Henle and collecting ducts. Renal Cortex: The outer region of the kidney, containing the Bowman’s capsule, proximal tubules, and distal tubules. The nephron is the functional unit of the kidney. Each kidney contains around 1 million nephrons, which are responsible for filtering blood and producing urine. Nephron Structure: 1. Glomerulus: A tangled knot of capillaries where blood is filtered under high pressure. 2. Bowman's Capsule: A cup-like structure surrounding the glomerulus where the filtered fluid (filtrate) collects. 3. Proximal Tubule: The first segment after the Bowman’s capsule, responsible for reabsorbing essential substances like glucose, amino acids, and 65% of water and ions. 4. Loop of Henle:  ○ Descending Limb: This section of the loop is permeable to water, but not to ions, leading to water reabsorption. ○ Ascending Limb: Impermeable to water, but actively pumps ions like sodium and chloride into the surrounding tissues, creating an ion gradient. 5. Macula Densa: A group of specialized cells that detect the sodium chloride content in the distal convoluted tubule, helping regulate kidney function. 6. Distal Tubule: Plays a role in reabsorbing ions and regulating pH, often under the influence of hormones like aldosterone. 7. Collecting Duct: Receives filtrate from multiple nephrons and adjusts the final composition of urine, including its water content. It is influenced by Antidiuretic Hormone (ADH). Kidney Function Overview: The main function of the kidneys is waste removal, water regulation, and maintaining homeostasis. The blood supply to the kidneys ensures that waste materials are filtered out of the blood at a high rate. Four Main Stages of Kidney Function: 1. Ultrafiltration: Filtering blood under pressure. 2. Selective Reabsorption: Reabsorbing useful substances back into the blood. 3. Production of Ion Gradient: Creating a hypertonic environment in the medulla to allow for efficient water reabsorption. 4. Adjustment of Water and Ion Content: Maintaining the balance of water and ions in the blood, which helps regulate blood pressure and volume. Key Processes in the Kidneys: 1. Ultrafiltration: Glomerulus: Blood enters the glomerulus via an afferent arteriole. Due to the narrower efferent arteriole, high hydrostatic pressure builds up inside the glomerulus. This pressure forces small molecules (like glucose, water, urea, and salts) through the capillary walls into the Bowman's capsule, forming the filtrate. Large molecules like proteins and blood cells are too large to pass through and stay in the bloodstream. 2. Selective Reabsorption: The proximal tubule is the main site of selective reabsorption, where the majority of the filtrate is reabsorbed back into the bloodstream. About 65% of filtered water, along with all glucose, amino acids, and essential ions, is reabsorbed here.  This process is active and involves specific transport proteins and channels that transport substances from the filtrate into the blood. 3. Production of Ion Gradient in the Medulla (Loop of Henle): The loop of Henle plays a critical role in creating an osmotic gradient in the renal medulla. ○ Descending limb: Permeable to water, allowing it to leave the filtrate and enter the surrounding tissue, making the filtrate more concentrated. ○ Ascending limb: Impermeable to water but actively pumps out sodium and chloride ions into the surrounding tissue, creating a concentration gradient in the medulla. The gradient established in the medulla allows the kidney to produce concentrated urine when needed. 4. Adjustment of Water Content (Collecting Duct and Distal Tubule): Distal Tubule: In the distal tubule, the filtrate is further adjusted, and ions such as sodium and potassium are reabsorbed or secreted depending on the body's needs. Collecting Duct: The final site for adjusting the water content of urine. ○ The permeability of the collecting duct to water is regulated by Antidiuretic Hormone (ADH): When ADH is present, the collecting duct becomes more permeable to water, allowing for more water to be reabsorbed into the blood. When ADH is absent, the duct is less permeable, leading to more water being excreted in the urine. Summary: The kidneys filter blood through the glomerulus, reabsorb useful substances like glucose and ions in the proximal tubule, and adjust water content and ion concentrations in the distal tubule and collecting duct. The kidneys are essential for water and waste regulation, maintaining homeostasis by filtering out waste products like urea and excess salts while conserving water. Hormones like ADH and aldosterone play crucial roles in regulating the water and ion balance of the body, ensuring the kidneys can adjust urine composition to maintain optimal blood pressure and volume. Reproductive Strategies to reproduce - - Semelparous - reproduces then dies “frogs or squids” have their babies then leave them to it  - Iteroparous - reproduce often “humans” have small amounts therefore will look after them Ovipary - refers to the development of an embryo within an egg outside the mother’s body. This occurs in most amphibians and reptiles and in all birds (egg laying) Ovovivipary - refers to the development of an embryo inside an egg within the mothers body until it hatches. The mother provides no nourishment to the developing embryo inside the egg. This occurs in some species of fish and reptiles. (combo of both) Vivipary - refers to the development of nourishment of an embryo within the mother’s body. Birth may be followed by a period of parental care of the offspring. This reproductive strategy occurs in almost all mammals. (live birth) Organs mammals male - Penis – In mammals this is the organ used to deliver sperm. It is made of erectile tissue that fills with blood during copulation Urethra – This is a tube encased in the penis which connects to the bladder to also allow the elimination of urine Epididymis – This is a set of tubes that connect to the testes. It is where sperm is stored before release Vas deferens – Tubes that transport sperm from the epididymis to the prostate gland. The prostate gland – This creates a fluid that protects the sperm and expels the sperm on ejaculation. Testes – The organ that produces sperm. (34-35C) Female reproduction - Vulva – The entrance to the vagina Vagina – the tube that receives the penis during copulation Cervix - the entrance to the uterus Uterus (womb)– Mostly called the womb. This is where zygotes (sperm and egg combined) are formed from a combination of sperm and egg. Oviducts – The ducts by which eggs are wafted down from the ovaries Ovaries – The storage and maturation of ova. These were all produced in utero within the female Reproductive Variations in Different Species: 1. Whales: ○ Testes are internal for streamlined body shape. ○ Blood cooling system: Blood is directed to the skin to cool before flowing to the testes, maintaining a temperature lower than the whale's body temperature. 2. Elephants: ○ Similar to whales, testes are internal and cooled via a blood cooling mechanism that passes through the skin before reaching the testes. 3. Pigs: ○ The cervix of a pig has interlocking folds, which help “trap” the male's corkscrew-shaped penis during copulation. This ensures prolonged mating (around 20 minutes), enhancing the chances of successful fertilization. Induced Ovulation: Induced Ovulation occurs in some mammals, where the act of mating triggers ovulation (release of eggs). ○ Example: Cats have a barbed penis, which stimulates ovulation during copulation. ○ Rabbits also ovulate during mating, which is why they are highly reproductive and capable of breeding quickly. Uterine Variations: 1. Pigs: ○ Uterus is heart-shaped and bicornuate, allowing them to carry multiple fetuses at once. This is why pigs can give birth to large litters (up to 20 piglets). Summary of Reproductive Strategies: Semelparous species reproduce once and die (e.g., frogs, squids). Iteroparous species reproduce multiple times throughout life (e.g., humans). Ovipary: Egg laying, with external development (e.g., birds, reptiles). Ovovivipary: Embryo develops inside an egg within the mother’s body (e.g., some fish, reptiles). Vivipary: Embryo develops inside the mother’s body with nourishment provided (e.g., mammals) Oestrus cycle - every animal but apes pg 21 - 23 Oistros - sex season Explanation - The oestrous cycle is a series of physiological changes that occur in female mammals, preparing the body for potential pregnancy. It is crucial for reproduction and influences behaviours associated with mating. Importance of the oestrus cycle - The oestrus cycle is important for several reasons, primarily because it regulates reproductive timing, ensuring that females are receptive to mating only during specific periods, which maximises the chances of successful conception. This cycle is crucial for population management, as it helps synchronise breeding within a population, maintaining genetic diversity and overall health, especially in wildlife conservation. Also the regularity and characteristics of the oestrus cycle serve as indicators of female reproductive health, irregularities can signal underlying health issues that may require medical attention from a vet. In an agricultural setting understanding the cycle enables farmers to optimise breeding schedules, improving productivity and ensuring healthier offspring. Overall the cycle influences behavioural patterns, such as increased vocalisation and restlessness during oestrus, which are important for mating success. For endangered species, knowledge of the oestrus cycle is essential for developing effective breeding programs and supporting population recovery. Overall, the oestrus cycle plays a critical role in reproductive success, population dynamics, and effective animal management practices. What are the phases of the oestrus cycle - - Phase 1 Proestrus: (bloody phase) This is the preparatory phase where the reproductive system gets ready for mating. Follicle-stimulating hormone (FSH) stimulates the growth of ovarian follicles, leading to an increase in oestrogen levels. This phase often includes physical changes, such as swelling of the vulva and changes in behaviour - Phase 2 Oestrus (Heat): During this phase, the female is receptive to mating. Ovulation typically occurs at the end of this phase, triggered by a surge in luteinizing hormone (LH). Behavioural signs of oestrus include increased restlessness, vocalisation, and a willingness to mate - Phase 3 Metoestrus (or Diestrus): (no reproductive phase) After ovulation, the body enters this phase, characterised by the formation of the corpus luteum, which produces progesterone. This hormone helps prepare the uterine lining for potential implantation of a fertilised egg. If fertilisation does not occur, the corpus luteum degenerates. - Phase 4 Anoestrus: (sexual rest, inactive) This is a period of reproductive inactivity that can occur between cycles. During anoestrus, the ovaries are inactive, and the female is not receptive to mating. The duration of this phase varies widely among species and can be influenced by factors such as age, health, and environmental conditions. These 4 phases work together to regulate the reproductive cycle, ensuring that animals can conceive and produce offspring at optimal times. The different hormones involved in the oestrus cycle -  1. Gonadotropin-Releasing Hormone (GnRH): Released by the hypothalamus, GnRH stimulates the pituitary gland to produce FSH and LH. 2. Follicle-Stimulating Hormone (FSH): Produced by the anterior pituitary, FSH promotes the growth and maturation of ovarian follicles. 3. Luteinizing Hormone (LH): Also produced by the anterior pituitary, LH triggers ovulation and the formation of the corpus luteum. 4. Oestrogen: Primarily produced by developing follicles, oestrogen is responsible for the estrus phase, stimulating behavioural changes and preparing the reproductive tract for mating. 5. Progesterone: Secreted by the corpus luteum, progesterone prepares the uterine lining for potential implantation and helps maintain pregnancy if fertilisation occurs. 6. Prostaglandins: These are involved in luteolysis, the breakdown of the corpus luteum, leading to a decrease in progesterone and the start of a new cycle 7. Inhibin: Produced by the ovaries, inhibin provides negative feedback to the pituitary gland to inhibit FSH production once enough follicles have developed Difference between the oestrus and the menstrual cycle Oestrous cycle Menstrual cycle;e Oestrous cycle occurs in Infra-primate female mammals Menstrual cycle occurs In human female and primates only, for example rats, mice, cat, dog, cow, horse, pig etc. Oestrous cycle has its four distinct phases, prostrus, Menstrual cycle has no such type of prostrus, estrus, estrus, metestrus and diestrus, where receptivity to metestrus or diestrus phases and females can mate males is limited to estrus phase only. with male during the entire cycle period. Oestrous cycle is normally of short duration starting Menstrual cycle duration is always of about a months from 4-days (28+2 days) Oestrous cycle has no distinct bleeding phase Menstrual cycle has a distinct bleeding phase towards the end of each cycle Types of Oestrus cycle - - In different mammals during their reproductive life, Estrous cycles vary between species - Polyestrous Animals (only once a year): Estrous cycles occurring throughout the time of the year (e.g, cattle, pigs, mice, rats). They can become pregnant without regard to the season of the year - Seasonally Polyestrous Animals (might be more than once a year): Animals that have multiple estrous cycles only during certain periods of the year (e.g, horses, sheep, goats, deer, cats). They are classified as “short day breeders” when they present estrous cycles during autumn when day length is decreasing (goats and ewes) and “long day breeders” (mares and queens) when they show estrous mainly during spring, when day length increases. - Monestrous Animals: Animals that have one estrous cycle per year (e.g, dogs, wolves, foxes, and bear) Musculoskeletal Skull Cranium – enclose and protect the brain Facial bones and jaw – protect the eyes and ears, upper jaw is fixed. Skull is joined to the vertebral column at the base of the cranium. Rib Twelve pairs of ribs Articulate with thoracic cavity, dorsally and sternum ventrally Cervical vertebrae – supports head and neck Thoracic vertebra – sentrum is short and thick Lumbar vertebra – large and thick sentrum Horses - The distal limb bones are the foundation of the equine lower leg. There are nine bones total and each plays a vital role in movement and stability. The distal limb is everything below the knee and the hock. It includes these regions: cannon fetlock joint  pastern hoof There is no muscle below the knee and hock. The nine bones are: Cannon Bone 2 Splint Bones 2 Sesamoid Bones Long Pastern Short Pastern Navicular Bone Coffin Bone In the young horse, there are three separate bones in the cannon region of the leg. It is very common for the splint bones to fuse with the cannon. In this example, one splint bone is fused and the other is not. This is the same cannon bone in each photo. 1. One of the splints has fused and the other has not. 2. The splint bone has been placed properly. 3. Lateral (side) view of the cannon bone and splint The Suspensory Ligament attaches to the proximal (top) back side of the cannon bone. It is nestled between the natural groove created by the splint bones. There are four bones in this area: Cannon 2 Sesamoid Bones Long Pastern The reason why horses have less bones and muscle in the lower part of their legs is so they can run faster for longer, their main predators were wolves. Wolves can run fast for a long amount of time so the horses adapt to keep away. Long bones are usually cylindrical and found in the appendicular system generally. The humerus, radius and ulna are all long bones. They are often longer than they are wide. Short bones are often cuboid in shape and equal in all dimensions. Carpals and tarsals are often short bones. Flat bones are thin but are often actually curved rather than flat like the scapular and the sternum. The ribs are also considered flat bones.  Sesamoid bones are the shape of sesame seeds and are found within tendons and help the movement of joints. One example being the kneecap. Irregular bones have an odd shape, such as the lower jaw (mandible) or the vertebrae Evolution and Movement (How the musculoskeletal system ties in with movement) Muscles, Tendons, Bones & Ligaments - ​A tendon is a tough yet flexible fibrous connective tissue which attaches muscle to bone. Tendons may also attach muscles to structures such as the eyeball. When a muscle contracts it shortens, pulling the tendon, and therefore moving the bone or structure. A ligament is a fibrous connective tissue, mainly collagen, which attaches bone to bone, and usually serves to hold structures together and keep them stable. Muscle action - Muscles are either relaxed or contracted. In the relaxed state muscle is compliant (it can be stretched), while in the contracted state muscle exerts a pulling force. Muscles can only pull (not push), they often work in pairs called antagonistic muscles. The muscle that bends (flexes) the joint is called the flexor muscle and the muscle that straightens (extends) the joint is called the extensor muscle. An example of antagonistic muscles are the biceps and triceps, which move the elbow joint. Relaxed muscle is never completely relaxed. It remains slightly contracted to provide resistance to the antagonistic muscle and so cause a smoother movement Human Musculoskeletal system - The human musculature is quite generalised. The most powerful muscles being the gluteus maximus which keeps us upright by keeping our hip bones extended. Most of the rest of our musculature is not particularly well developed. The Endocrine system - Coordination and control The nervous system translates information needed about the environment and uses it to work out what we need to do. The endocrine system on the other hand is slow, the effects of the majority of hormones takes hours, even years to take effect. This is done through the use of chemicals called ‘hormones’. Hormones come in several major types and several effects. Two types of systems: - The endocrine system - The endocrine system uses the release of specialised hormones directly into the blood. The blood acts as the vector of the hormones transporting them to the cell that needs to be affected. When the hormone reaches the cell it will enter it and make the adjustments required. There are two major forms of endocrine hormone. Peptide hormones – Made up of amino acids. Steroid hormones – made up of fatty acids. - The paracrine system - These hormones are released directly into the interstitial fluid around cells and affect the other cells around the releasing cell. These are often called ‘local’ hormones since they never leave the tissue they are released into. They do not reach the blood, they also are effectively very localised in effect and that’s the last I’ll mention these during this unit Hypothalamus - - Location - base of brain case. - Functions - regulation of primitive of Basal activities such as sex drive and water balance - 9 hormones - 7 act on anterior lobe of pituitary gland (Tropic) - 2 stored in posterior lobe The pituitary - master gland  What is the endocrine system? The endocrine system is made up of glands and the hormones they secrete. Although the endocrine glands are the primary hormone producers, the brain, heart, lungs, liver, skin, thymus, gastrointestinal mucosa, and placenta also produce and release hormones Primary endocrine glands Hormone produced What is its function Pituitary gland (the master Adrenocorticotropic hormone It regulates various body glands) (ACTH) functions and plays an important Thyroid-stimulating hormone role in controlling hormone levels (TSH) in the body. Luteinising hormone (LH) Follicle-stimulating hormone (FSH) Prolactin (PRL) Growth hormone (GH) Melanocyte-stimulating hormone (MSH) Pineal gland Melatonin Help control the circadian cycle of sleep and wakefulness by secreting melatonin. The pineal gland is shaped like a tiny pinecone, which is how it got its name (“pine”-al gland). Thyroid gland Thyroxine (T4), Control the speed of your Triiodothyronine (T3) metabolism (metabolic rate) Calcitonin. Parathyroid gland Parathyroid hormone To make the parathyroid hormone Calcitonin (PTH). This chemical regulates Calcitriol the amounts of calcium, phosphorus and magnesium in the bones and blood. Islets of Langerhans Insulin Produces hormones (e.g., insulin Glucagon and glucagon) that are secreted Somatostatin into the bloodstream  Ghrelin Pancreatic polypeptide (PP) Adrenals gland Aldosterone (a mineralocorticoid), Adrenal glands produce Cortisol (a glucocorticoid), hormones that help regulate your Androgens and estrogen (sex metabolism, immune system, hormones). blood pressure, response to stress and other essential functions. Ovary in the female Oestrogen Produce hormones that help with Progesterone your menstrual cycle and Androgens. pregnancy. Testes in the male Testosterone Making sperm and are also Androgenic hormone involved in producing a hormone called testosterone. Hypothalamus Corticotropin Helps manage your body Dopamine temperature, hunger and thirst, Growth hormone mood, sex drive, blood pressure Somatostatin and sleep. Gonadotropin Thyrotrophin Pituitary gland Adrenocorticotropic hormone Regulates various body functions (ACTH) and plays an important role in Thyroid-stimulating hormone controlling hormone levels in the (TSH) body. The pituitary gland does Luteinising hormone (LH) that by making a number of Follicle-stimulating hormone hormones that either regulate (FSH) most of the other Prolactin (PRL) hormone-producing glands in the Growth hormone (GH) body or have a direct effect on Melanocyte-stimulating hormone specific organs. (MSH) Heart Atrial natriuretic peptide (ANP), To pump blood and oxygen Brain (or B-type) around the body and deliver Natriuretic peptide (BNP), waste products (carbon dioxide) C-type natriuretic peptide (CNP) back to the lungs to be removed Kidney Erythropoietin remove waste from the blood and Renin return the cleaned blood back to Calcitriol. the body. Stomach Gastin - stimulates Protein in the The stomach is a J-shaped organ stomach that digests food. It produces Secretin - Acid in the duodenum enzymes (substances that create Cholecystokinin - Fat/protein in chemical reactions) and acids  duodenum (digestive juices). This mix of GIP (glucose-dependent enzymes and digestive juices insulinotrophic peptide.) - breaks down food so it can pass Duodenal chyme to your small intestine. Pancreas Insulin produces enzymes that help to Glucagon digest food, particularly protein. Intestines Gastrin. breaks down food and fluid to Somatostatin. absorb nutrients and water Secretin. Cholecystokinin (CCK) Fibroblast Growth Factor 19 (FGF19) Incretins. Ghrelin. Neuropeptide Y (NPY)