Key terms exam 4
Lecture 10
Asexual Reproduction: Formation of new individuals without the fusion of gametes (sperm and egg), meaning only one parent is involved. Offspring are typically genetically identical to the parent (clones).
Sexual Reproduction: Formation of embryos via the fusion of two haploid gametes (sperm and egg), typically requiring genetic contribution from two distinct individuals. This process involves meiosis and fertilization, leading to genetically diverse offspring.
Fission: Separation of an individual into two or more parts of roughly equal size, each growing into a new organism. Often occurs rapidly, allowing for quick population growth.
Fragmentation: Breaking off of a body part from an existing organism, where the fragment can then regenerate and develop into a whole new, complete individual. This requires robust regenerative capabilities in the fragments.
Budding: Formation of a new individual as an outgrowth or bud from the parent organism. The bud grows, eventually detaches, and develops into a fully independent organism.
Stolon: Structures from which new individuals can grow in certain organisms like tunicates (sea squirts), leading to colonial forms.
Parthenogenesis: Development of a new individual from an unfertilized egg. This process can be obligate (only way of reproduction) or facultative (can switch between sexual and asexual).
Gonochoristic (dioecious): Characterized by separate male and female individuals within a species, each producing only one type of gamete (sperm or egg).
Hermaphroditic (monoecious): An individual organism capable of producing both sperm and eggs (male and female gametes) at some point in its life.
Outcrossing: This term is not explicitly defined in the provided note, but it generally refers to cross-fertilization, where an individual mates with another genetically distinct individual, promoting genetic diversity. It is the opposite of self-fertilization.
Genetic Sex Determination: A system where the sex of an offspring is determined by the genes or chromosomes inherited from the parents (e.g., XX for female, XY for male in mammals; ZZ for male, ZW for female in birds; fertilized egg female, unfertilized egg male in haplodiploidy).
Environmental Sex Determination (TSD): A system where the sex of an offspring is determined by environmental factors, such as the incubation temperature of the eggs during a critical period of embryonic development, as seen in many reptiles.
Wolffian Duct: In males, stimulated by testosterone from the developing testes, this embryonic duct develops into male reproductive structures, including the epididymis, vas deferens (ductus deferens), and seminal vesicles. In females, it typically regresses.
Müllerian Duct: In females, in the presence of estrogens and the absence of Anti-Müllerian Hormone (AMH), this embryonic duct develops into female reproductive structures, including the oviducts (fallopian tubes), uterus, and the upper part of the vagina. In males, AMH causes it to regress.
Oviduct (Fallopian Tube): Part of the female reproductive tract that develops from the Müllerian Duct, functioning to transport eggs from the ovary to the uterus. Site of fertilization in many species.
Ductus Deferens (Vas Deferens): Part of the male reproductive tract that develops from the Wolffian Duct, functioning to transport sperm from the epididymis to the ejaculatory duct.
Gametogenesis: The general biological process by which diploid or haploid precursor cells undergo cell division and differentiation to form mature haploid gametes (sperm or eggs).
Oogenesis: The process of egg production in females, occurring in the ovaries. It is a discontinuous process, resulting in typically one large, nutrient-rich ovum and polar bodies.
Spermatogenesis: The process of sperm production in males, occurring continuously in the seminiferous tubules of the testes. Each primary spermatocyte leads to four equal, motile sperm.
Lecture 11
Broadcast Spawning: A reproductive strategy where many marine animals release gametes (sperm and eggs) directly into the water column for external fertilization, relying on currents for dispersion and statistical probability for successful fertilization.
Amplexus: A mating embrace, often seen in frogs, where the male clasps the female, typically around her waist or armpits, to externally fertilize the eggs as she releases them, ensuring close proximity of gametes.
External Fertilization: Fertilization that occurs outside the body of the parents, typically in an aquatic environment, such as in broadcast spawning where gametes are released into the water.
Internal Fertilization: Fertilization where sperm fertilizes eggs within the female's reproductive tract, offering advantages like protection from environmental hazards and increased fertilization efficiency.
Modes for Attracting Mates: Various strategies animals use to find and secure a mate, including coordinating signals (e.g., pheromones, lunar cycles), mate choice based on direct or indirect benefits (e.g., vocal signals, nuptial gifts, good genes), courtship displays, and the development of secondary sexual characteristics.
Sexual Dimorphism: Consistent physical differences between males and females of a species, beyond primary reproductive organs, such as differences in size, coloration, weaponry, vocalizations, and behavior, often driven by sexual selection and hormonal influences.
Sequential Hermaphroditism: A reproductive strategy where individuals are born as one sex and can change sex over their lifespan, optimizing reproductive output based on factors like size, age, social hierarchy, or environmental conditions.
Protogynous: A type of sequential hermaphroditism where individuals start as females and can subsequently change into males, often triggered by reaching a larger size or a dominant social position (e.g., purple-headed wrasse).
Protoandrous: A type of sequential hermaphroditism where individuals start as males and can subsequently change into females, often seen in social hierarchies where the breeding female is removed (e.g., clownfish).
r-strategy (r-selected species): A life history strategy characterized by producing a large number of offspring with low individual parental investment, rapid maturation, short lifespans, and typically inhabiting unstable environments. Focus is on maximizing reproductive rate (rr).
K-strategy (K-selected species): A life history strategy characterized by producing fewer offspring with high parental investment per individual, slow maturation, long lifespans, and typically inhabiting stable, predictable environments. Focus is on competitive ability near carrying capacity (KK).
Oviparity: A reproductive mode where offspring develop in eggs that are laid outside the mother's body and hatch externally (e.g., many frogs, most insects, birds).
Viviparity: A reproductive mode where offspring develop inside the mother's body and are born live, often receiving nutrition directly from the mother during gestation (e.g., caecilians, mammals).
Parental Care: Any behavior by a parent to increase the fitness of its offspring, involving protection, provisioning, or carrying offspring. This varies greatly in duration and intensity across species.
Trade-offs (in reproductive strategies): The compromises or energetic balances involved in allocating resources between different life history traits, such as investing in many small offspring with low individual care versus few large offspring with high individual care.
Gastrulation: A critical stage in early embryonic development following the formation of the blastula, during which the single-layered blastula is reorganized into a multilayered structure (the gastrula) through cell migration and rearrangement, forming the primary germ layers.
Blastopore: An indentation on the surface of the gastrula where cells invaginate during gastrulation. In protostomes, it develops into the mouth; in deuterostomes (like vertebrates), it develops into the anus.
Embryonic Germ Layers: The three primary cell layers (ectoderm, mesoderm, and endoderm) formed during gastrulation from which all tissues and organs of the adult body develop.
Ectoderm: Forms external layers like skin, nervous system, and sensory organs.
Mesoderm: Forms muscles, bone, connective tissue, circulatory system, and reproductive organs.
Endoderm: Forms the lining of the digestive and respiratory tracts, and associated glands.
Organogenesis: The process in embryonic development during which the three germ layers differentiate into specific organs and organ systems.
Determinants of Developmental Patterns: The combined influence of an organism's genetic blueprint (genotype) and environmental factors (internal and external) that intricately shape how developmental processes unfold and lead to observable traits (phenotype).
Epigenetics: Heritable changes in gene expression that occur without a change in the underlying DNA sequence. These mechanisms (e.g., DNA methylation, histone modification) can be influenced by environmental factors and regulate gene activity.
Phenotypic Plasticity: The ability of a single genotype to produce different phenotypes (observable traits) in response to varying environmental conditions, allowing for flexible adaptation.
Phenotypic Canalization: The tendency of a phenotype to remain constant or robust despite genetic or environmental variation, ensuring the consistent development of critical traits.
Significance of Transplant Experiments: Experiments (e.g., Spemann and Mangold's amphibian embryo studies) that demonstrate concepts like embryonic induction and how transplanted tissues can retain species-specific information and predetermined fates, revealing the robustness of inherent developmental instructions.
Cell Fates: The developmental destiny of a cell, referring to the specific cell type or tissue it will eventually differentiate into, often determined early in development.
Stem Cells: Undifferentiated cells that have the capacity to self-renew (divide indefinitely) and differentiate into specialized cell types.
Pluripotent Stem Cells: Stem cells that can differentiate into any cell type of the three germ layers (ectoderm, mesoderm, endoderm) but not into extraembryonic tissues (e.g., embryonic stem cells, induced pluripotent stem cells (iPSCs)).
Multipotent Stem Cells: Stem cells restricted to differentiating into specific lineages or a limited number of cell types within a particular tissue (e.g., hematopoietic stem cells).
Lecture 12
Cancer: A dangerous disease characterized by the uncontrolled proliferation and metastasis of abnormal cells, leading to the formation of tumors in various body parts.
Relationship between cancer prevalence and cell division rate: A direct correlation exists where a higher number of cell divisions in a tissue over a lifetime increases the likelihood of DNA mutations, thereby elevating the risk of cancer in that tissue.
Transmissible Cancers: Rare forms of cancer that can spread directly between individuals, such as the Tasmanian devil facial tumor disease (DFTD), through the transmission of cancerous cells themselves.
Hormones: Chemical messengers secreted by endocrine glands into the bloodstream that travel to target cells to elicit specific physiological effects, with examples including epinephrine, T3T3, and T4T4.
Endocrine System: A major regulatory system composed of glands that produce and secrete hormones, which are transported via the circulatory system to communicate signals throughout the body.
Endocrine Glands: Ductless glands that secrete hormones directly into the bloodstream, such as the thyroid gland, which produces T3T3 and T4T4.
Pathway of Hormones and their various responses in target cells: Hormones travel through the bloodstream from endocrine glands to target cells, where they bind to specific receptors. The type and quantity of these receptors determine the varied and specific physiological responses in different tissues.
Positive Feedback: A regulatory mechanism where the output of a process enhances or intensifies the initial stimulus, leading to an amplified response.
Negative Feedback: A common regulatory mechanism in hormone systems where the output of a process inhibits or reduces the initial stimulus, thereby maintaining homeostasis.
Alternate Endocrine Responses: The phenomenon where a single hormone can elicit different physiological effects in various target tissues, depending on the specific receptor types present in those cells (e.g., epinephrine causing different responses in intestinal vs. skeletal muscle blood vessels).
Thyroid hormone and effects on development and physiology: Thyroid Gland hormones (T3T3 and T4T4), requiring iodine for synthesis, are essential for regulating metabolism, growth, and development across nearly all body tissues. Insufficient iodine can lead to goiter.
Interactions among hormone pathways: Hormonal pathways interact through complex regulatory networks, including feedback mechanisms and diverse tissue-specific responses, where the outcome in one pathway can influence others, contributing to systemic physiological control.
Lecture 13
Bioenergetics: The quantifiable study of the energy flow and energy transformations (e.g., in metabolism) in living organisms.
Metabolism: The sum total of all the chemical reactions that occur within an organism to maintain life. These reactions are typically organized into metabolic pathways.
Anabolism: Constructive metabolism; processes that build complex molecules from simpler ones. These reactions typically require energy input (endergonic) to form new chemical bonds.
Catabolism: Destructive metabolism; processes that break down complex molecules into simpler ones. These reactions typically release energy (exergonic) as chemical bonds are broken.
Metabolic mechanisms that release heat: Processes, such as cellular respiration, that produce heat as a byproduct. In endotherms, this metabolic heat is crucial for maintaining internal body temperature.
Endothermic Organisms ("warm-blooded"): Organisms that maintain body temperature internally through metabolic heat production, regulating their body temperature within a narrow, optimal range largely independent of external temperatures. Traits include high energy requirements and specialized structures for heat retention/release.
Ectothermic Organisms ("cold-blooded"): Organisms that rely primarily on external environmental sources for body temperature regulation. Their internal temperature fluctuates with the ambient temperature. Traits include lower energy use compared to endotherms of similar size.
Exceptions: Certain large fish like tuna and opa fish demonstrate temporary or full endothermic capabilities (e.g., tuna use a countercurrent exchange system to retain muscle heat; opa fish uses continuous fin flapping and gill countercurrent exchange to warm its entire body).
Measuring metabolic rate and correlations: Metabolic Rate (MR) is the rate at which an organism consumes energy, typically measured as oxygen consumption or heat production over time. MR is generally inversely related to body size in endotherms when expressed per unit of body mass (mass-specific metabolic rate), meaning smaller endotherms have higher mass-specific metabolic rates.
Surface Area to Volume Ratio as it relates to body size and metabolism: As an organism's linear dimensions increase, its surface area grows by the square () while its volume (and thus mass) grows by the cube (). Consequently, the surface area to volume ratio decreases significantly with increasing size. Smaller animals have a higher ratio, leading to more rapid heat loss and thus higher mass-specific metabolic rates to compensate. Larger animals have a lower ratio, promoting heat retention and allowing for lower mass-specific metabolic rates.
Energy expenditures: The allocation of energy intake among various life processes such as maintenance (basal metabolism), growth, and reproduction. This differs dramatically based on body size, phylogenetic group, and temperature regulation needs.
Mechanisms of thermoregulation: Diverse methods organisms employ to manage body temperature, balancing heat gain and loss in various environments. These include insulation, physiological responses, and behavioral adaptations.
Insulators: Materials or structures that reduce heat transfer between an organism and its environment.
Hair/Fur: Traps a layer of air close to the body, reducing conductive and convective heat loss.
Feathers (especially down feathers): Similar to fur, they create an insulating air layer.
Adipose tissue (fat): A thick layer providing effective insulation, such as blubber in marine mammals.
Vasodilation vs. Vasoconstriction (Physiological Responses):
Vasodilation: Dilation of blood vessels near the surface of the skin, increasing blood flow and heat loss to the environment.
Vasoconstriction: Constriction of blood vessels near the skin surface, reducing blood flow and minimizing heat loss, thereby retaining heat in the body core.
Evaporative cooling: A mechanism where the evaporation of water from a surface (e.g., skin in sweating, respiratory tract in panting) carries away a significant amount of heat, thus cooling the organism.
Sweat glands: Specialized glands in the skin of some mammals that produce sweat for evaporative cooling.
Mechanisms for energy conservation: Metabolic adjustments organisms undergo to cope with environmental extremes, conserving energy during periods of scarcity or harsh conditions.
Torpor: A state of decreased physiological activity characterized by reduced body temperature and metabolic rate. It is a short-term adaptation (hours to days) to conserve energy during periods of food scarcity or unfavorable temperatures.
Hibernation: An extended state of torpor in endotherms, typically occurring in colder seasons, involving drastically lowered body temperature, respiratory rate, and metabolic rate, surviving on stored fat reserves for weeks or months.
Aestivation: A state of animal dormancy, similar to hibernation, characterized by inactivity and a lowered metabolic rate, occurring in response to high temperatures or drought conditions.
Lecture 14
Herbivory: A dietary habit where animals primarily consume plant matter, including leaves, fruits, nectar, seeds, wood, or algae.
Carnivory: A dietary habit where animals primarily eat animal matter, either by hunting live prey (predation) or scavenging dead animals.
Omnivory: A dietary habit characterized by consuming a varied diet of both plants and animals, demonstrating high dietary flexibility.
Stenophagous vs. Euryphagous:
Stenophagous (Specialized Feeders): Animals with a narrow diet, often relying on one or a few specific food sources, allowing for extreme efficiency in exploiting a particular resource but making them vulnerable to changes in food availability. Example: pandas eating bamboo.
Euryphagous (Generalist Feeders): Animals with a broad diet, consuming a wide variety of food types, which enhances their ability to survive in diverse environments or when preferred food sources are scarce. Example: black bears.
Ontogenetic Diet Switching: Significant diet changes that animals undergo throughout their developmental stages, often accompanied by morphological and physiological adaptations. Example: tadpoles (herbivores) becoming frogs (carnivores).
Suspension Feeding (Filter Feeding): A method of obtaining small particles (plankton, detritus) suspended in water by straining large volumes of water through specialized filtering structures. Examples: baleen whales, flamingos.
Fluid Feeding: A method of feeding on liquid nutrients, either from animals (blood, hemolymph) or plants (nectar, sap), using specialized piercing or sucking mouthparts. Examples: mosquitoes, aphids.
Substrate Feeding: A method where animals live in or on their food source and consume it directly, often extracting nutrients as they move through the substrate. Examples: earthworms, leaf miners.
Bulk Feeding: A method of consuming relatively large pieces of food, which may include swallowing whole prey, tearing off chunks, or crushing entire organisms. Examples: pythons, crabs.
Structures for Feeding: Diverse anatomical features adapted for an animal's specific diet and food collection method. These include jaws, teeth, beaks, mandibles, proboscises, and protrusible tongues. Examples: anteater's long sticky tongue, chameleon's rapid tongue projection.
Tooth Distributions and Variations: The varied forms and arrangements of vertebrate teeth that directly correlate with dietary preferences:
Carnivores: Scissor-like jaw movements, sharp canines for piercing, and blade-like carnassial molars for slicing flesh.
Herbivores: Square jaw angle for side-to-side grinding, broad, flat molars with ridged surfaces for pulverizing plant matter; often self-sharpening.
Humans (Omnivores): Mixed dentition with flat incisors for biting, pointed canines for tearing, and broad molars for crushing and grinding.
Venoms (Neurotoxic vs. Hemotoxic): Specialized secretions containing a complex mixture of toxins, used by certain animals (e.g., reptiles, some mammals) for subduing prey or defense:
Neurotoxic Venoms: Disrupt nervous system functions, leading to paralysis, respiratory failure, or cardiac arrest.
Hemotoxic Venoms: Damage blood cells, tissues, and blood vessels, leading to hemorrhage, clotting abnormalities, and tissue necrosis.
Digestive Tract Components: The tubular system with two distinct openings (mouth and anus) for sequential food processing. Key regions include:
Pharynx: The part of the throat behind the mouth and nasal cavity, and above the esophagus and larynx, through which food passes.
Stomach: A muscular organ for chemical digestion (acid and enzymes).
Intestine: Divided into small (for enzymatic digestion and nutrient absorption) and large (for water absorption and waste formation).
Crop (in birds): A pouch for food storage and softening.
Gizzard (in birds): A muscular stomach for mechanical grinding of food.
Variation in Digestive Tract Components: Different sections of the digestive tract are adapted for specific functions across species. Example: Ruminants have a four-chambered stomach for microbial fermentation of cellulose, while birds have crops and gizzards not present in mammals.
Villi, Microvilli: Structural adaptations in the small intestine that increase its surface area for efficient nutrient absorption.
Villi: Finger-like projections of the intestinal lining.
Microvilli: Microscopic projections on the surface of epithelial cells that line the villi, forming a 'brush border'.
Organs that Assist Digestion:
Liver: Produces bile for fat emulsification and plays crucial roles in metabolism and detoxification.
Gallbladder: Stores and concentrates bile produced by the liver before releasing it into the small intestine.
Pancreas: Produces digestive enzymes (e.g., amylases, proteases, lipases) and hormones (insulin, glucagon) for blood glucose regulation.
Glucose Homeostasis: The process of maintaining stable blood glucose levels, vital for cellular energy and physiological function. Insulin decreases blood sugar by promoting glucose uptake and storage as glycogen, while glucagon increases blood sugar by signaling the liver to release stored glucose. Potential problems include diabetes mellitus due to imbalances.
Homeostatic level: approximately glucose per blood.
Hormone Regulation of Appetite: The complex interplay of hormones, neural signals, and environmental cues influencing hunger and satiety:
Ghrelin: 'Hunger hormone' produced by the empty stomach, stimulating appetite.
Leptin: 'Satiety hormone' produced by fat cells, signaling long-term energy reserves and decreasing appetite.
GLP-1 (Glucagon-Like Peptide-1): Promotes satiety, slows gastric emptying, and enhances insulin release.
Peptide YY (PYY): Signals fullness from the intestine, reducing appetite. Potential problems involve disruptions due to stress, anxiety, or sleep deprivation.
Lecture15
Diffusion: The tendency for molecules to naturally separate evenly across a space.
Passive transport: Movement of small molecules or those with certain properties across biological membranes without requiring energy.
Active Transport: Movement of molecules across biological membranes that requires energy and specific receptors.
Osmosis: The diffusion of water across selectively permeable membranes.
Osmolarity: A measure of total solute concentration within a solution.
Isoosmotic: A state where there is equal osmolarity on both sides of a membrane.
Hyperosmotic: A state where there is a higher osmolarity on one side of a membrane.
Hypoosmotic: A state where there is a lower osmolarity on one side of a membrane.
Stenohaline: Organisms that tolerate narrow osmolarity ranges.
Euryhaline: Organisms that can tolerate broad osmolarity ranges.
How organisms (e.g., fishes) deal with different osmolarities:
Marine Fish (e.g., Codfish): Hypotonic to the ocean; actively drink seawater to prevent dehydration and excrete salt through gills while retaining water.
Freshwater Fish (e.g., Yellow Perch): Hypertonic compared to freshwater; prevent gaining excessive water by excreting large amounts of urine and actively absorbing ions across gills.
Transport epithelium: Specialized cells that manage salt and ion transport in various organisms, such as in albatrosses for salt handling.
Ways animals gain water and how this varies among species: Drinking, Eating, and Metabolism; desert rodents heavily rely on metabolic processes for hydration.
Ways animals lose water and how this varies among species: Excretion, evaporation, and desiccation.
How body size relates to water loss: Larger organisms often have specialized systems for material transport, including water, due to surface area to volume ratio challenges that small, flat organisms don't face to the same extent for direct exchange.
Anatomy of water conservation:
Coverings: Adaptations like reptile scales (keratinized) or mammalian fur/coats reduce water loss and retain hydration.
Intestines: Reabsorption processes within the intestines help recapture water lost during digestion.
Kidneys: Functional units that filter blood, remove waste, and precisely regulate water and solute balance.
Ammonia (NH3NH3): A highly toxic nitrogenous waste suitable for organisms in aquatic environments, requiring significant water for excretion.
Urea: A less toxic nitrogenous waste, energetically expensive to produce, suitable for both aquatic and terrestrial organisms, with moderate water loss during excretion.
Uric Acid: The least toxic nitrogenous waste, requires the most energy to produce, results in low water loss, and is often excreted as a paste (e.g., birds).
How nitrogenous wastes differ with respect to toxicity, energy, and water retention:
Ammonia: High toxicity, low energy cost to produce, high water loss for excretion.
Urea: Moderate toxicity, moderate energy cost, moderate water loss for excretion.
Uric Acid: Low toxicity, high energy cost to produce, low water loss for excretion.
Protonephridia: A primitive excretion system found in flatworms, featuring flame bulbs to filter waste from tissues.
Flame Bulb: A component of protonephridia that filters waste out of tissues.
Malpighian tubules: Excretion system in arthropods that extends from the digestive tract to filter nitrogenous waste and return it to the gut for expulsion.
Nephron: The functional unit of the vertebrate kidney, with millions serving to filter the bloodstream.
Glomerulus: A capillary network within Bowman's capsule where filtration occurs, allowing smaller molecules to pass but retaining larger ones.
Bowman 's Capsule: Part of the renal corpuscle where filtrate is collected after being forced out of the glomerulus.
Loop of Henle: A crucial structure in the nephron for establishing the kidney's osmotic gradient, which becomes progressively steeper towards the inner medulla and is essential for water conservation.
Proximal Tubule: The section of the nephron where a large percentage (about 60-70%) of essential nutrients, salts (NaClNaCl), and water are reabsorbed back into the bloodstream.
Distal Tubule: The section of the nephron where further selective reabsorption of ions (e.g., Na+Na+, Cl−Cl−, HCO3−HCO3−) and secretion of others (e.g., K+K+, H+H+) occur, regulated by hormones.
Concentration gradient in the kidney: An osmotic gradient established and maintained primarily in the medulla by the loop of Henle, essential for controlling water reabsorption.
Pathway of a nephron and how it assists in water conservation: The nephron's pathway, particularly the loop of Henle establishing a strong osmotic gradient in the medulla and the collecting duct utilizing this gradient under ADH regulation, allows for significant water reabsorption, thus conserving body water.
lecture #16
Role of gastrovascular cavity in respiration: A hollow, sac-like structure found in cnidarians (e.g., Hydra) that facilitates gas exchange through its external and internal surfaces, allowing efficient oxygen diffusion into cells and removal, in addition to nutrient absorption and digestion.
Basic components of a circulatory system: Generally includes a muscular pump (heart), a circulatory fluid (blood or hemolymph), and a network of vessels (arteries, capillaries, veins, or open sinuses/hemocoel).
Open vs. Closed Circulatory System:
Open Circulatory System: Found in arthropods and most mollusks; hemolymph (a mixture of blood and interstitial fluid) is pumped by a heart into a body cavity (hemocoel), directly bathing organs and tissues under lower pressure.
Closed Circulatory System: Found in vertebrates, cephalopods, and some annelids; blood is entirely confined within a continuous network of vessels (arteries, capillaries, veins) and distinct from interstitial fluid, pumped under relatively high pressure for efficient, controlled transport.
Hemolymph vs. Blood:
Hemolymph: The circulatory fluid in open circulatory systems, composed of a mixture of blood and interstitial fluid.
Blood: The circulatory fluid in closed systems, confined to vessels and separate from interstitial fluid, primarily responsible for transporting gases (oxygenated or deoxygenated), nutrients, and waste.
Components of Blood: In the context of circulation, blood is primarily characterized by its oxygenation status, being either oxygenated (rich in ) or deoxygenated (rich in and low in ) for transport within closed systems.
Arteries vs. Veins:
Arteries: Blood vessels that carry blood away from the heart.
Veins: Blood vessels that carry blood towards the heart.
Variation in vertebrate hearts: Vertebrate hearts range from two chambers (one atrium, one ventricle) in fish, to three chambers (two atria, one ventricle with some mixing of blood) in amphibians, to three chambers with a partially divided ventricle in most reptiles (or functionally four in crocodilians), and fully four chambers (two atria, two ventricles) in birds and mammals for complete blood separation.
Variation in vertebrate circulatory systems: Vertebrate circulatory systems vary from a single circuit in fish (heart gills body heart) to a double circuit (pulmonary and systemic) in tetrapods, which enhances efficiency and metabolic rates by separating blood flow to the respiratory surface and the rest of the body.
Haemodynamics: The principles of fluid dynamics that describe the physical forces and mechanisms governing blood flow, pressure, and resistance within the circulatory system.
Gill filaments and lamellae:
Gill filaments: Numerous feathery structures supported by gill arches in fish, which bear the respiratory surface.
Lamellae: Microscopic, richly vascularized folds on gill filaments that provide a vastly increased surface area and thin barrier for efficient gas exchange between blood and water.
External gills: Prominent, feathery projections extending from the body into the water, seen in certain amphibians (e.g., salamander larvae) and some fish, allowing direct gas exchange with the surrounding aquatic environment.
Lungs and swim bladders:
Lungs: Primary internal respiratory organs in many terrestrial vertebrates, providing a large, moist internal surface area for efficient gas exchange in air.
Swim bladders: Gas-filled sacs in bony fish, primarily adapted for buoyancy control, though some can function as accessory respiratory organs, illustrating an evolutionary link to lungs.
Variation in vertebrate lung surface area: The surface area of vertebrate lungs varies considerably, often increasing with metabolic demands; mammalian lungs with numerous alveoli, for instance, offer an extremely large surface area crucial for highly efficient gas exchange to support high metabolic rates.
Alveoli: Microscopic air sacs found in the lungs of mammals and birds, providing an extensively large and thin surface area for highly efficient gas exchange, facilitating rapid oxygen uptake and carbon dioxide release.
Respiratory surface plasticity: The ability of an organism to utilize multiple respiratory surfaces or adapt its mode of respiration based on environmental conditions or life stage, such as amphibians using moist skin or lungfish possessing both gills and lungs.
Multimodal Respiration: A strategy where animals use more than one type of respiratory organ or mechanism for gas exchange, either simultaneously or interchangeably, enabling survival in fluctuating environments (e.g., lungfish using gills and lungs).
Lung reduction and loss: While not explicitly detailed, the evolution of lung derivatives like swim bladders in bony fish demonstrates a modification or reduction in primary respiratory lung function in favor of buoyancy control, though some still retain accessory respiratory roles.
Respiratory surface area variation: The significant differences in the extent and structure of respiratory surfaces across diverse organisms, ranging from simple direct diffusion across body surfaces (small animals) to highly specialized and extensively folded structures (e.g., gill lamellae, alveoli) to maximize surface area for efficient gas exchange.
Lecture 17
Nervous system distribution and diversity: Animals exhibit diverse nervous system structures; sponges lack them entirely, while jellyfish and sea anemones have simple nerve nets. Bilaterians, however, display cephalization (concentration of nervous tissue at a head end) and a Central Nervous System.
Nerve Net: A diffuse network of nerves found in simpler animals (e.g., jellyfish and sea anemones) that allows for simple responses transmitted across the entire organism.
Central Nervous System (CNS): Comprises the brain and spinal cord, which are connected by peripheral nerves.
Dendrites: Branching extensions of a neuron that are specialized to receive signals from other neurons or tissues.
Axons: Long projections that carry electrical signals away from the neuron's cell body to other cells.
Neurotransmitters: Chemical messengers that facilitate communication between neurons by crossing the synapse, inducing either excitatory (stimulating) or inhibitory (suppressing) responses.
Astrocytes: A type of glial cell that provides structural support and maintains the necessary chemical environment for neuronal function.
Schwann Cells: A type of glial cell that forms a myelin sheath around axons, insulating them and significantly increasing the speed of electrical signal transmission.
White vs. Grey Matter: Not discussed in the provided notes.
Action potential: An electrical current generated in a neuron when stimulation causes sodium channels to open, leading to an influx of sodium ions (depolarization) making the cell positively charged, followed by potassium channels opening and potassium exiting the cell (repolarization), eventually returning the cell to its resting potential.
Functions of Central vs. Peripheral Nervous System:
Central Nervous System (CNS): Primarily involved in processing information and initiating responses, consisting of the brain and spinal cord.
Peripheral Nervous System (PNS): Connects the CNS to the rest of the body, including cranial and spinal nerves. It includes afferent nerves (carrying sensory signals to the CNS) and efferent nerves (transmitting motor signals from the CNS to muscles and glands).
Spinal Cord: A component of the Central Nervous System (CNS).
Cranial Nerves: Nerves within the Peripheral Nervous System (PNS) that primarily handle sensory input.
Spinal Nerves: Nerves within the Peripheral Nervous System (PNS) that primarily handle motor output.
Somatic Nervous System: Not discussed in the provided notes.
Autonomic Nervous System: Not discussed in the provided notes.
Brain size to body size relationships: Explained by the Encephalization Quotient (EQ), which is a measure of brain size relative to body size that indicates cognitive abilities across different species. Humans typically have a high EQ.
Olfactory lobe: structure in the forebrain of vertebrates involved in the perception of odors
Cerebrum: A key area of the brain involved in sensory processing and coordinated action.
Cerebellum: A key area of the brain responsible for motor control.
Medulla oblongata: A key area of the brain that regulates essential visceral functions such as heart rate and digestion.
Thalamus large, egg-shaped structure located deep within the brain, acting as a major relay station for sensory information
Hippocampus: A key area of the brain central to long-term memory and spatial navigation.
Hypothalamus: linking the nervous system to the endocrine system via the pituitary gland. It controls many bodily functions including body temperature, hunger, thirst, fatigue, sleep, and circadian rhythms
Pituitary: 'master gland' because it makes hormones that control many other glands and important body functions like growth, how your body uses energy (metabolism), and reproduction
Amygdala: processing emotions, especially fear and pleasure, and plays a role in memory.
Neuroplasticity: The ability of the nervous system to change through growth and reorganization in response to environmental stimuli, learning, hormonal changes, and synaptic activity.