Gas Exchange Systems Exam Prep PDF

Topic 2, 3 & 4 Concept 7 Online: Respiration: Gas echange systems This concept explores respiration and the important structures that have evolved to aid in gas exchange across different groups of organisms. Watch the videos and interactive activities located on canvas. Use this document to genera...

Topic 2, 3 & 4 Concept 7 Online: Respiration: Gas echange systems This concept explores respiration and the important structures that have evolved to aid in gas exchange across different groups of organisms. Watch the videos and interactive activities located on canvas. Use this document to generate notes and answer questions. The purpose of this worksheet is to assist you in identifying the key points of each concept. Throughout this concept you will explore: Concept Title Intended Learning Outcomes Define and contrast anaerobic and aerobic respiration. Respiration & Gas 7.1 Explain why gas exchange is important and what features Exchange of gas exchange surfaces increase the rates of diffusion. Describe the main structure used by plants & fungi for Gas Exchange Systems: 7.2 gas exchange and explain other features of plants that Plants & Fungi assist with the process. Describe the main structures of the gas exchange Gas Exchange Systems: 7.3 systems of animals, and compare and contrast them in Animals water and air. Concept 7.1: Respiration & Gas Exchange - Review Question Answer List two advantages of aerobic - Releases more atp molecules than anaerobic respiration respiration (32-38 vs 2 ATP) - May have allowed for the evolution of multicellularity and larger organism size Explain how these advantages may - have led to the evolution of multicellularity  Describe the features of gas exchange surfaces that maximise diffusion in relation to Fick’s Law - Specialised gas exchange surfaces must maximise membrane area and minimize membrane thickness in order to match the volume of the organism and its oxygen requirements. Therefore many gas exchange surfaces are made up of thin branches or folded membranes Concept 7.2: Gas exchange systems in fungi & plants Question Answer Describe one physical characteristic and - Different plants have different shapes of their one physiological mechanism that stomata and their guard cells which changes the enables plants to adjust their rates of degree of which their stomata can open (kidney gas exchange shaped vs dumbbell shaped) - Provide an example of structures with - Large mycelium which possesses microscopic high surface area to volume ratios that hyphae that extend into small crevices in the soil aid in gas exchange in fungi or other substrates to interact with small air pockets. Mycelium has a very large surface area to volume ratio and can form colonies which produce fruiting bodies that extend above the substrate into the air. Fruiting bodies exchange gas via their thin body walls which can be porous and rely on diffusion between cells for supplying oxygen throughout the body. Worksheet booklet Page of 78  Label the leaf cells/tissues that you know already and draw the path of gasses as move through the plant for gas exchange. Describe two structural features of - Epidermis of leaf plants that aid in gas transport - stomata Concept 7.3: Gas exchange systems in animals Question Answer Identify structural differences in - in moist/aquatic environments animals with thin tissues can avoid the the lungs of different vertebrates need for specialized gas exchange structures by simply relying on oxygen that are related to oxygen diffusion across their body wall (annelid, nematode and platyhelminth requirements wors) who increase the surface area for gas exchange by having long thin bodies and by co-opting other structures with large surface areas to aid in gas exchange. Such as their projecting feet like parapodia or in the case of sedentary worms that live in burrows, their feeding tentacles. - In larger more active species, specialized gas exchange structures have evolved, and each serve specific purposes based on the habitat and lifestyle of the animal in question. - There are two main processes involved to ensure that sufficient gasses are moved across the gas exchange surface, either via body movement, or the respiratory structure itself. This ensures that the pressure gradient for diffusion is optimized and increases the rate of diffusion across the gas exchange surface. - The second is circulation where gas is moved to and from the gas exchange surface and the body tissues, Worksheet booklet Page of 78  this can occur via dissolution into a circulatory fluidlike blood Explain the key difference - In terrestrial environments, the availability of oxygen between gas exchange in water is high but the water loss is the problem, to ensure and air respiratory surfaces stay moist terrestrial animals have internal gas exchange structures. - Explain why trachea are so - Insects have a specific gas exchange structure for their efficient at gas transport terrestrial environment, utilizing a network of tubes called trachea. Allows direct oxygen delivery to tissues and cells. Air opens through small openings called spiracles located along side of thorax and abdomen from spiracles air is transported into finer tubes called tracheoles that extend to individual cells. - Trachea provides large surface area for gas exchange, allowing oxygen to diffuse directly into cells while co2 diffuses out. - In order to balance the opposing needs for conserving water and obtaining oxygen, insects are able to close their spiracles to prevent water loss, as well as contact their abdomens, which is a form of ventilation, that sucks more air and oxygen inside body. - In larger terrestrial animals the internal gas exchange system is made up of highly vascularized lungs, air enters through nose or mouth, through the trachea and into bronchi. Depending on the O2 requirements of the animal, lung may also be further divided into bronchioles which end in alveoli - Walls of lung are thin and surrounded by many small capillaries to transport O2 to and CO2 from body tissues. Branching network of the lungs provides a vast surface area for gas exchange and is kept moist by surfactants. Worksheet booklet Page of 78  - Special molecules with a hydrophilic and hydrophobic end secreted by pneumocyte cells in the lung. - Surfactants reduce surface tension of the lung to aid in the diffusion of gasses - Birds must be capable of high rates of gas exchange, because their oxygen at rest is highest of all other vertebrates, including mammals, and these requirements increase drastically during flight, - Unidirectional air, lungs don’t move but are ventilated through air sacs indifferent specific order. Bronchi have large surface area - Gills (fish) are made up of many individual filaments covered in lamellae to increase the SA for gas exchange - As water flows over gill surfaces, oxygen diffuses from water into blood through gill capillaries, internal gills are very efficient because employ countercurrent exchange mechanism where water and blood flow in opposite directions, maintaining a conc. Gradient that maximises O2 uptake and CO2 removal Worksheet booklet Page of 78 Concept 8 Online: Nutrition, Digestion & Excretion This concept introduces you to how different organisms acquire & digest essential nutrients and excrete waste by-products. Watch the videos and interactive activities located on canvas. Use this document to generate notes and answer questions. The purpose of this worksheet is to assist you in identifying the key points of each concept. Throughout this concept you will explore: Concept Title Intended Learning Outcomes Explain the key adaptations related to autotrophic and 8.1 Nutrient acquisition heterotrophic resource acquisition (feeding). Explain the key adaptations of transporting nutrients, 8.2 Plant nutrition & excretion assimilation and excretion in plants. Animal nutrition & Explain the key adaptations of transporting nutrients, 8.3 excretion assimilation and excretion in animals and fungi. Concept 8.1: Nutrient acquisition Question Answer Define the differences between Cellular Respiration: autotrophs and heterotrophs. Purpose: Converts food into usable energy for organisms. Gas Exchange: Systems have evolved to ensure a continuous supply of oxygen for cellular respiration. Nutrient Acquisition: Autotrophs: o Photosynthetic Autotrophs: ▪ Examples: Plants, algae, photosynthetic bacteria. ▪ Process: Capture sunlight using chlorophyll in chloroplasts. Convert carbon dioxide and water into glucose through the Calvin cycle. Worksheet booklet Page of 78  ▪ Role: Primary producers that support most life forms by producing organic compounds from sunlight. o Chemosynthetic Autotrophs: ▪ Examples: Certain bacteria and archaea living in extreme environments (e.g., deep-sea hydrothermal vents). ▪ Process: Oxidize inorganic compounds like hydrogen sulfide to obtain energy. Convert carbon dioxide, oxygen, and hydrogen sulfide into carbohydrates. ▪ Symbiotic Relationships: Live in association with heterotrophic organisms (e.g., giant tube worms), providing nutrients through chemosynthesis. ▪ Key Pathways: ▪ Sulfur Oxidation: Hydrogen sulfide is oxidized to sulfite, thiosulfate, and elemental sulfur, releasing ATP. ▪ Carbon Fixation Pathways: Includes the Calvin-Benson-Bassham cycle and the reductive carboxylic acid cycle. Heterotrophs: o Definition: Obtain nutrients by consuming other organisms or organic matter. o Types: Worksheet booklet Page of 78  ▪ Consumers: Feed on autotrophic or other heterotrophic organisms. ▪ Decomposers: Break down dead organic matter into simpler compounds. o Adaptations: ▪ Food Capture and Collection: ▪ Animals: ▪ Modified Mouth Parts: Vertebrates have teeth with specific shapes for capturing or digesting food (e.g., carnivores with sharp teeth, herbivores with flat teeth). Insects have diverse mouthparts for siphoning, sucking, or capturing prey. ▪ Modified Limbs: Adaptations for manipulating or capturing prey, such as claws or specialized appendages. ▪ Digestive Systems: ▪ Mechanical Digestion: Physical breakdown of food into smaller pieces (e.g., chewing in mammals). ▪ Chemical Digestion: Enzymatic breakdown of food into soluble Worksheet booklet Page of 78  nutrients (e.g., stomach acids and enzymes). ▪ Specialized Digestive Tracts: Different organisms have unique adaptations for digestion, such as extended digestive tubes or specialized compartments. ▪ Plants and Fungi: ▪ Partial Heterotrophy: Some plants and fungi obtain nutrients from organic matter. ▪ Fungi: Decompose dead or decaying matter, aiding in nutrient cycling. ▪ Parasitic Plants: Obtain nutrients from other living plants (e.g., dodder, mistletoe) and can transfer RNA or pathogens to hosts. ▪ Carnivorous Plants: Capture and digest living organisms to supplement nutrient intake (e.g., Venus flytrap, pitcher plants). They produce digestive enzymes and attractants (e.g., nectar). Worksheet booklet Page of 78  Explain why nutrients are important for life. List the 4 main mechanisms by which heterotrophs obtain the nutrients they require. Concept 8.2: Plant Nutrition & Excretion Question Answer List two adaptations of heterotrophic 1. Metabolic Processes and Excretion: plants that enable the acquisition of nutrients o Metabolism: All organisms perform metabolic processes essential for growth and survival, generating by-products that can be toxic. o Excretion: By-products must be eliminated to avoid toxicity. 2. Cellular Respiration in Plants: o By-Products: Cellular respiration produces carbon dioxide and water. o Photosynthesis: Plants are autotrophic and produce their own food via photosynthesis, which generates oxygen Worksheet booklet Page of 78  and glucose, and these products are used in cellular respiration. o Waste Management: Plants recycle many of these by-products, but excess gases and water must be removed to maintain homeostasis. 3. Waste Removal Mechanisms: o Stomata and Transpiration: ▪ Function: Stomata on leaves allow for the evaporation of water vapor, which helps draw water up through the xylem and facilitates water absorption from roots. ▪ Regulation: Stomatal opening is controlled by environmental factors (light, carbon dioxide, humidity) and stress hormones (e.g., abscisic acid). o Lenticels: ▪ Function: Permanently open pores on stems and woody plant bark that contribute to the removal of excess water and gases, though to a lesser extent compared to stomatal transpiration. 4. Nitrogenous Waste Management: o Nitrogen Uptake: Plants absorb nitrogen from soil (ammonia and nitrates) through xylem sap. o Waste Conversion: Nitrogenous waste (like urea) from protein metabolism is either excreted or converted into reusable forms for protein synthesis. o Fertilizers: Nitrogenous wastes are also used as fertilizers to support plant growth. 5. Storage and Guttation: Worksheet booklet Page of 78  o Vacuole Storage: Plants can store unwanted metabolic by-products in vacuoles, such as amino acids, mineral salts, and water, which can accumulate in tissues like fruit, leaves, and bark. o Guttation: ▪ Process: Occurs at night when the stomata are closed. Excess water and minerals are excreted as droplets of xylem sap from leaf margins. ▪ Hydathodes: Specialized cells (likely evolved from stomata) facilitate this process when root pressure exceeds transpiration, playing a key role in waste excretion in some plants. Describe the symbiotic relationship between fungi and plants that aids in nutrient acquisition Describe two mechanisms by which plants excrete unwanted by- products/wastes Worksheet booklet Page of 78  Provide a brief explanation of why plants have no need for a centralised system to excrete nitrogenous waste Worksheet booklet Page of 78 Concept 8.3: Animal/Fungi Nutrition & Excretion Question Answer Describe the common features of 1. Fungi: the gastrovascular cavity of some animals o Role in Ecosystems: Fungi act as detritivores or decomposers, recycling nutrients and supporting plant growth by returning essential nutrients to the soil. o Nutrient Acquisition: ▪ Sources: Obtain carbon compounds from non-living organic material or living organisms. ▪ Absorption: Nutrients are absorbed through the cell walls. ▪ Feeding Mechanisms: ▪ Multicellular Fungi: Grow hyphae into food sources. ▪ Unicellular Yeasts: May form colonies to exploit food sources. ▪ Nutrient Breakdown: ▪ Small Molecules: Diffuse through the cell wall from a surrounding watery film. ▪ Macromolecules: Require extracellular digestion facilitated by enzymes released from hyphae or yeast, which break down substrates before absorption. 2. Animals: o Digestive System: ▪ Purpose: Breaks down food into absorbable components and transports nutrients throughout the body. Worksheet booklet Page of 78  ▪ Digestive Tract: Highly vascularized, essential for nutrient transport. ▪ Digestive Tract Sections: ▪ Foregut: Involves food intake, storage, and initial digestion. ▪ Midgut: Main site for chemical digestion and nutrient absorption. ▪ Hindgut: Involved in further digestion and waste excretion. ▪ Digestive Adaptations: ▪ Herbivores: ▪ Mechanical Digestion: Begins in the mouth with grinding or shredding, continues in a muscular stomach or crop. ▪ Specialized Stomachs: Ruminants have a four- compartment stomach for fermentation (rumen, reticulum, omasum, abomasum). Non-ruminants may have a long hindgut with a caecum for fermentation. ▪ Carnivores: ▪ Adaptations: Mouthparts are adapted for capturing and cutting prey (e.g., curved, serrated teeth). Less reliance on mechanical digestion; more emphasis on chemical digestion. Worksheet booklet Page of 78  ▪ Digestive Tract: Typically shorter and simpler, with a highly acidic stomach for efficient protein digestion. 3. Nutrient Absorption: o Surface Area Optimization: Increased surface area for absorption is achieved through: ▪ Inward Folding: Structures like the typhlosole in earthworms. ▪ Additional Structures: Spiral valves in sharks. ▪ Villi and Microvilli: Tiny projections on absorptive cells increase surface area and enhance nutrient absorption, interacting with a dense capillary network for efficient transport. This summary highlights the key mechanisms by which fungi and animals obtain, digest, and absorb nutrients, as well as the specialized adaptations in their digestive systems. Concept 9.1 sensory systems 1. Environmental Change: o Temporal and Spatial Scales: Environmental changes can occur on daily, seasonal, or long-term scales and affect abiotic factors (temperature, humidity, sunlight) and biotic factors (food abundance, competitors, threats, reproductive partners). 2. Signals and Cues: o Signals: ▪ Definition: Acts or structures created by organisms to influence others' behavior. ▪ Evolution: Signals evolve to affect receivers intentionally and may sometimes be repurposed. For instance, bioluminescence in fireflies evolved from a predatory warning to a mating signal. o Cues: ▪ Definition: Incidental sources of information that influence behavior but were not evolved specifically for this purpose. ▪ Sources: Can be abiotic (e.g., sunlight, temperature) or biotic (e.g., feces indicating predator presence). 3. Detectability and Reliability: Worksheet booklet Page of 78  oCriteria for Useful Cues: Cues must be reliably discernible from background noise and consistently provide the same type of information. o Sensory Modalities: ▪ Types: Chemical, electrical, mechanical, visual (photo), magnetic, and auditory. ▪ Example: Bats use ultrasonic hearing to detect prey, which is effective within their hearing range but not for lower frequency sounds like car engines. 4. Sensory Modalities and Detection: o Adaptation: The sensory modalities an organism uses depend on its environment and lifestyle. o Example: Bats’ sensitivity to specific frequencies helps them detect prey sounds effectively. 5. Examples: o Bioluminescence: In elateroid beetles, initially evolved as a predatory warning and later co-opted as a mating signal. o Odor Cues: Red-necked wallabies avoid foraging in areas with the odor of dog feces, which might indicate the presence of predators. This summary highlights the ways organisms perceive and react to environmental changes, focusing on the role of signals and cues, their detectability, and the adaptations in sensory modalities. 1. Types of Sensory Receptors: o Chemoreceptors: Detect chemical compounds through a "lock and key" mechanism. Molecules bind to specific receptors, which can either: ▪ Direct Activation: Open a channel in the cell membrane directly. ▪ Indirect Activation: Trigger a signal transduction pathway that opens a different channel. o Thermoreceptors: Modified chemoreceptors that respond to temperature changes. They change shape with temperature variations, altering ion flow across the cell membrane. o Mechanoreceptors: Respond to mechanical stimuli such as movement, stretch, or vibration. They typically involve channels that open when stretched or moved, allowing ions to pass through. o Photoreceptors: Detect specific wavelengths of light. Photons interact with photoreceptor proteins (like opsins, which contain vitamin A), causing these proteins to change shape and initiate a signaling cascade. 2. Basic Receptor Functions: o Chemoreceptors: Involved in detecting chemical signals, like taste and smell. o Thermoreceptors: Involved in sensing temperature changes. o Mechanoreceptors: Involved in detecting physical changes like pressure or vibration. o Photoreceptors: Involved in vision, detecting light and color. 3. Specialized Receptor Modifications: o Baroreceptors: Modified mechanoreceptors that detect pressure changes. Found in blood vessels for monitoring blood pressure and in the inner ear for detecting barometric pressure and altitude changes. o Ultraviolet (UV) Photoreceptors: Modified photoreceptors in many insects that detect UV light. Used for locating food and mates, and also present in plants to adjust growth and opening based on light conditions. 4. Sensory Systems and Signal Processing: o Signaling Cascades: Receptor activation often initiates a signaling cascade that can lead to responses in central sensory organs or control centers like the brain. Worksheet booklet Page of 78  Receptor Adaptation: Receptors are modified to broaden and specify the types of o stimuli they respond to, allowing organisms to detect a wide variety of environmental changes. This summary outlines the primary sensory receptors—chemoreceptors, thermoreceptors, mechanoreceptors, and photoreceptors—and their specialized functions and adaptations in different organisms. Concept 9.2 - Plants have a wide variety of photoreceptors that enable them to detect many wavelengths of light, ranging from ultraviolet B (280-315 nanometers) to far-red (700-750 nanometers). Photoreceptors in plants contain photopigments, which consist of a protein component bound to a non-protein, light-absorbing pigment called the chromophore. Phytochromes are a class of photoreceptors that sense red and far-red light. The phytochrome system acts as a natural light switch, allowing plants to respond to the intensity, duration, and color of environmental light. - For example, bright direct sunlight contains more red light than far-red light, and plants use phytochromes to adapt their growth in response to levels of direct sunlight or shade. Exposure to far-red light in shaded regions triggers the elongation of stems and petioles in search of light. On the other hand, exposure to red wavelengths from unfiltered sunlight enhances lateral growth and branching. - The circadian—or biological—clock is an intrinsic, timekeeping, molecular mechanism that allows plants to coordinate physiological activities over 24-hour cycles called circadian rhythms. Photoperiodism is a collective term for the biological responses of plants to variations in the relative lengths of dark and light periods. - The phytochrome system enables plants to compare the duration of dark periods over several days. Phytochromes exist as two interconvertible forms: Pr and Pfr. Pr is converted into Pfr during the day, so Pfr is more abundant in daylight hours. Pfr is converted into Pr at night, so there is more Pr at nighttime. Therefore, plants can determine the length of the day- night cycle by measuring the Pr/Pfr ratio at dawn. The long nights of winter reduce Pfr levels at dawn, while the shorter nights of spring result in higher Pfr levels at sunrise. - Even though plants are sedentary, they can adjust their position in relation to their surroundings by changing the rate of growth/elongation in different tissues and in assymetrical ways. Plants do this based on a number of external stimuli. Concept 9.3 Sensory Modalities Sensory modalities are channels through which animals detect and interpret sensory information from their environment. These modalities rely on various types of sensory receptors, each specialized to detect specific stimuli. The primary sensory receptors include: 1. Chemoreceptors: Detect chemical compounds. 2. Thermoreceptors: Respond to temperature changes. 3. Mechanoreceptors: Sense mechanical changes like pressure, stretch, or vibration. 4. Photoreceptors: Respond to light. Sensory Processing Action Potentials: Sensory receptors convert environmental stimuli into action potentials. These electrical signals travel along the nervous system to the brain. Worksheet booklet Page of 78  Perception: The brain processes these signals in different areas, such as the visual cortex for light and the auditory cortex for sound. The perception of stimuli (like heat or pressure) depends on which part of the brain receives and processes these action potentials. Sensory Receptor Adaptations Intensity of Stimuli: The strength of perception can vary based on receptor activation. Factors include: o Range: For example, hearing is effective within specific frequency ranges. o Number of Receptors: More receptors activated can lead to a stronger perception. o Rate of Action Potentials: Higher frequency of action potentials can signal stronger stimuli. Chemical Sensing Olfaction: The sense of smell relies on chemoreceptors in the nasal cavity. Odorant molecules bind to olfactory receptors, triggering signals sent to the olfactory bulb and then to the brain. Complex odors activate unique combinations of receptors, allowing for the discrimination of many odors. Humans have around 350 receptor types, while mice have over 1000. Pheromones: Chemical signals used for communication between individuals of the same species. Pheromones can attract mates, signal alarm, mark trails, or define territories. Detection varies by species: o Insects: Often detected by antennae. o Mammals: Primarily detected by the olfactory system. Light Detection Photoreceptors: Detect different wavelengths of light. Light detection is crucial for various processes, including circadian rhythms and seasonal changes. Animal eyes and light-sensitive structures have evolved independently across species. Vertical Migration: Many marine animals, from zooplankton to fish and mammals, migrate vertically in the ocean based on light cues. For example, zooplankton and jellyfish have photoreceptors that help them move according to light intensity. Complex Eyes: Vertebrates have more complex eyes with photoreceptors that influence circadian rhythms. The suprachiasmatic nucleus (SCN) in the hypothalamus receives light information from the eyes via the retinohypothalamic tract, regulating sleep, digestion, and thermoregulation. Summary Sensory modalities allow animals to perceive and respond to environmental changes through specialized receptors. These receptors translate stimuli into action potentials that are processed by the brain, leading to different perceptions. Sensory systems, such as olfaction and vision, are adapted to detect and interpret a wide range of stimuli, influencing behaviors and physiological processes. Concept 10.1 Homeostasis - Temperature & Biological Systems Temperature and Reaction Rates 1. Effect of Temperature on Reaction Rates o Kinetic Energy: As temperature increases, the kinetic energy of molecules also increases. This makes molecules move faster, which enhances the likelihood of collisions and interactions between them. Consequently, the rate of biochemical reactions generally increases with rising temperature. o Optimal Temperature: Most biochemical reactions have a temperature-dependent rate that increases up to an optimal temperature and then declines if the temperature Worksheet booklet Page of 78  continues to rise. This forms a characteristic thermal response curve for each reaction. 2. Thermal Response Curves o Definition: Thermal response curves plot how a physiological variable, such as reaction rate, changes with temperature. These curves can vary significantly between different organisms and their environmental conditions. 3. Q10 Temperature Coefficient o Calculation: Q10 measures how the rate of a reaction changes with a 10°C increase in temperature. It is calculated by dividing the reaction rate at a higher temperature by the rate at a lower temperature (e.g., rate at 30°C / rate at 20°C). o Interpretation: ▪ Q10 = 1: No change in reaction rate with temperature. ▪ Q10 = 2: Reaction rate doubles with each 10°C increase. ▪ Q10 = 3: Reaction rate triples with each 10°C increase. o Typical Values: Most biochemical reactions and physiological processes have a Q10 between 2 and 3. 4. Examples of Temperature-Dependent Reactions o Photosynthesis: ▪ Variation: The rate of photosynthesis varies with temperature among different plant types. For example, C4 plants have a higher optimal temperature range compared to C3 or CAM plants, which typically have a narrower optimal temperature range. ▪ Acclimation: Plants can adjust their optimal temperature range through acclimation, meaning they can grow and adapt to higher temperatures over time. o Cellular Respiration: ▪ Across Species: Cellular respiration rates vary with temperature across different organisms, from microbes in soil to fish like sockeye salmon and reptiles like iguanas. Each species has an optimal temperature range suited to its ecological niche and metabolic needs. 5. Organismal Strategies for Temperature Adaptation o Acclimation and Adaptation: Organisms may acclimate (adjust physiological processes to new temperature ranges) or adapt (evolve to have a broader range of optimal temperatures) to ensure their biochemical reactions remain efficient despite temperature fluctuations. o Thermoregulation: ▪ Sedentary Organisms: Plants, fungi, and unicellular organisms often rely on acclimation and adaptation since they have limited mobility and control over their internal temperatures. ▪ Mobile Organisms: Animals use physiological and behavioral strategies for thermoregulation to maintain an optimal internal temperature, balancing heat gain and loss. In summary, temperature profoundly influences biochemical reaction rates, with a general trend of increased rates at higher temperatures up to an optimal point. Various organisms have evolved different strategies to cope with temperature changes, including acclimation, adaptation, and thermoregulation. Concept 10.2 Thermoregulatory Strategies and Metabolism Worksheet booklet Page of 78 Thermoregulation in Animals: An Overview Thermoregulation refers to how organisms maintain their internal body temperature within a range that supports optimal physiological function. Given the wide range of environmental conditions and biological diversity, animals have evolved various strategies to manage their body temperature. These strategies can be broadly classified into physiological and behavioral mechanisms, as well as further distinguished by their thermoregulatory strategies. Heat Transfer Mechanisms 1. Heat Gain: o Radiation: Heat absorption from the sun, ground, or sky. 2. Heat Loss: o Conduction: Heat transfer through direct contact with surfaces. o Convection: Heat transfer through the movement of air or water around the organism. o Evaporation: Loss of heat through the conversion of liquid water to vapor. Thermoregulatory Strategies 1. Thermoregulation Mechanisms: o Physiological: Internal mechanisms to regulate body temperature, including altering blood flow, metabolic rates, and behavioral adjustments. o Behavioral: Adjustments in behavior, such as seeking shade or basking in the sun, to regulate body temperature. 2. Types of Thermoregulators: o Endotherms: ▪ Definition: Organisms that generate most of their body heat internally through metabolic processes. ▪ Homeothermic Endotherms: Maintain a stable body temperature despite external temperature fluctuations (e.g., mammals like mice). ▪ Heterothermic Endotherms: Can drop their body temperature significantly during periods of inactivity or extreme cold (e.g., animals that hibernate or enter torpor). o Ectotherms: ▪ Definition: Organisms that rely on external sources of heat to regulate their body temperature. ▪ Heterothermic Ectotherms: Body temperature fluctuates with environmental temperatures (e.g., many reptiles and insects). ▪ Homeothermic Ectotherms: Maintain a relatively stable body temperature in environments where external temperatures are stable (e.g., some fish and amphibians). Examples and Adaptations 1. Ectothermic Lizard: o Thermoregulation: Body temperature closely tracks environmental temperature, demonstrating heterothermic ectothermy. These lizards use behavioral strategies such as basking to increase body temperature and seeking shade to cool down. 2. Endothermic Mouse: o Thermoregulation: Maintains a stable internal temperature over a wide range of environmental temperatures, demonstrating homeothermic endothermy. Uses physiological mechanisms such as shivering and vasoconstriction to manage temperature. 3. Marine Iguanas: Worksheet booklet Page of 78  Behavioral Thermoregulation: When diving into cold waters, their body temperature o and heart rate drop due to conductive cooling. They bask on warm rocks to regain heat via radiation and convection, balancing their body temperature for efficient swimming and digestion. Special Considerations 1. Torpor and Hibernation: o Endotherms: Some endotherms enter states of torpor or hibernation to survive extreme temperatures by lowering their body temperature to near ambient levels. This allows them to conserve energy during periods when external conditions are not favorable. 2. Acclimation and Adaptation: o Acclimation: Short-term physiological adjustments to environmental changes (e.g., adjusting to a gradual increase in temperature). o Adaptation: Long-term evolutionary changes that enhance survival in specific temperature ranges. 3. Behavioral Thermoregulation in Ectotherms: o Ectotherms rely heavily on behavioral adaptations to regulate body temperature, often moving between different microclimates to optimize their thermal balance. Understanding these strategies helps illustrate how diverse organisms manage thermal stress and maintain their physiological functions across varying environmental conditions. Metabolic Rate and Thermoregulation in Animals Understanding how animals regulate their metabolic rate in response to external temperatures provides insight into their survival strategies and adaptations. Metabolic rate, which represents the rate of cellular respiration and energy expenditure, is closely linked to body temperature and environmental conditions. Metabolic Rate and Temperature 1. Ectotherms: o Definition: Animals that rely on external sources of heat to regulate their body temperature (e.g., lizards). o Metabolic Rate Response: For ectotherms, metabolic rate increases with environmental temperature, following a Q10 value typically between 2 and 3. This means that for every 10°C rise in temperature, their metabolic rate approximately doubles or triples. o Temperature Response Curves: Ectotherms exhibit thermal performance curves where their metabolic rate increases with temperature up to an optimal point before declining. This relationship reflects their dependence on environmental temperatures for metabolic function. o Thermal Tolerance: Ectotherms have critical thermal minimum (CT_min) and critical thermal maximum (CT_max), beyond which their metabolic performance declines. These limits define their thermal tolerance and optimal performance ranges for growth and reproduction. 2. Endotherms: o Definition: Animals that maintain their body temperature internally through metabolic heat production (e.g., mice). o Metabolic Rate Response: Endotherms exhibit a more complex relationship with environmental temperature. They have a thermoneutral zone where their metabolic rate remains relatively stable because the cost of maintaining optimal body temperature is minimized. Worksheet booklet Page of 78  Thermoneutral Zone: This zone represents a range of environmental temperatures o where endotherms do not need to expend extra energy to regulate body temperature. Outside this zone, they must increase metabolic heat production to maintain warmth or to dissipate excess heat. o Thermal Conductance: Thermal conductance, which refers to the rate of heat exchange between an animal and its environment, influences how metabolic rate responds to temperature. It is affected by the animal's size, shape, and insulation (e.g., fur, fat). Key Concepts 1. Q10 Value: o Definition: A measure of how the rate of a biochemical reaction changes with a 10°C change in temperature. o Ectotherms: Typically have Q10 values between 2 and 3, indicating that their metabolic rate doubles or triples with each 10°C rise in temperature. 2. Thermal Conductance: o Definition: The ability of an animal to transfer heat with its environment. o Influence: Higher thermal conductance leads to a steeper relationship between metabolic rate and temperature, making it more challenging for animals to maintain a stable internal temperature. Lower thermal conductance results in a more gradual relationship, allowing for a wider thermoneutral zone. 3. Size and Shape: o Smaller Animals: Generally have higher thermal conductance due to their larger surface area-to-volume ratio. They often have a narrower thermoneutral zone. o Larger Animals: Tend to have lower thermal conductance, resulting in a broader thermoneutral zone. 4. Adaptations: o Behavioral: Both ectotherms and endotherms may adjust their behavior to regulate body temperature, such as seeking shade or basking. o Physiological: Endotherms may use mechanisms like shivering or sweating to regulate body temperature, while ectotherms rely more on environmental heat sources. Examples Ectothermic Lizard: o Metabolic Rate: Fluctuates with environmental temperature in a predictable manner based on the Q10 value. o Behavioral Thermoregulation: The lizard moves between sun and shade to maintain an optimal body temperature. Endothermic Mouse: o Metabolic Rate: Remains relatively constant within the thermoneutral zone but increases outside this range to maintain body temperature. o Thermoregulatory Adaptations: Uses physiological mechanisms such as vasoconstriction and shivering to regulate body temperature in response to extreme temperatures. Understanding these dynamics helps in predicting how animals might cope with changes in their environment, such as those brought about by climate change or seasonal variations. Concept 10.3 Body Size, Metabolic Rate, and Allometry Worksheet booklet Page of 78 Understanding how body size influences metabolic rate involves exploring the relationship between mass, metabolic processes, and various physiological parameters across different species. This relationship is crucial for comparing metabolic rates accurately and has been the focus of significant biological research. Key Concepts 1. Basal Metabolic Rate (BMR) and Standard Metabolic Rate (SMR): o BMR (Endotherms): The metabolic rate of endotherms (e.g., mammals and birds) measured under specific conditions: resting state, post-absorptive (not digesting food), and not in a reproductive state. It reflects the minimum energy required to maintain basic physiological functions. o SMR (Ectotherms): The metabolic rate of ectotherms (e.g., fish, reptiles) measured under similar resting conditions but at a consistent environmental temperature. It represents the energy expenditure at rest. 2. Allometry: o Definition: The study of the relationship between body size and various biological variables such as anatomy, physiology, and behavior. Allometric scaling helps understand how metabolic rate changes with body size. o Kleiber's Law: Formulated by Max Kleiber in 1932, this law states that metabolic rate scales with body mass to the 0.75 power. This means that as body size increases, the metabolic rate does not increase proportionally but rather at a slower rate. 3. Metabolic Scaling: o Exponent of 0.75: Kleiber's Law suggests that larger animals have a lower metabolic rate per unit of body mass compared to smaller animals. For example, an elephant has a much higher total metabolic rate than a shrew, but its metabolic rate per gram of tissue is lower. o Surface Area-to-Volume Ratio: Initially, it was expected that metabolic rate would scale with body size based on this ratio, but Kleiber’s Law showed a different exponent, indicating a more complex relationship. 4. Recent Theories: o Fractal Geometry: Some researchers propose that the scaling relationship is related to the fractal-like structure of vascular networks that supply oxygen and nutrients to cells. As body size increases, the complexity and branching of these networks change, impacting metabolic rates. o Growth and Reproduction: It is also suggested that metabolic scaling is influenced by the interplay between metabolic rate, growth, and reproduction. Larger organisms may have optimized physiological traits that balance energy expenditure for growth, maintenance, and reproduction. Examples 1. Small vs. Large Mammals: o Elephant Shrew vs. Elephant: An elephant shrew (small mammal) and an elephant (large mammal) exhibit a vast difference in total metabolic rate, with the elephant’s rate being around 1000 times greater. However, when normalized for body mass, the metabolic rate per unit body weight is much higher in the elephant shrew. 2. Application Across Species: o Unicellular Organisms to Plants: Kleiber’s Law and similar scaling principles apply across a wide range of organisms, from unicellular protists to multicellular plants and animals. The general pattern is that larger organisms have a slower metabolic rate per unit mass compared to smaller ones. Implications Worksheet booklet Page of 78  Ecological and Evolutionary Insights: Understanding metabolic scaling helps explain energy requirements and survival strategies across species and environments. For example, it can shed light on how energy is allocated in different-sized organisms and how they adapt to their habitats. Practical Applications: Knowledge of metabolic rate scaling is crucial in fields like conservation biology, where energy budgets and metabolic needs must be considered for species conservation and management. In summary, the relationship between body size and metabolic rate, as explored through allometric scaling and Kleiber’s Law, provides valuable insights into the energy dynamics of living organisms. It highlights how body size affects metabolic processes and offers a framework for understanding metabolic rates across a wide range of species. Concept 11.1 Reproduction in Organisms: A Overview Reproduction is fundamental for the continuation of life, allowing organisms to pass on their genetic material to the next generation. This process can be broadly classified into two main categories: asexual and sexual reproduction. Each method has distinct advantages and disadvantages and is adapted to different ecological niches and evolutionary pressures. Asexual Reproduction Definition: Asexual reproduction involves a single organism producing offspring without the need for a partner. The offspring are genetically identical to the parent, resulting in clones. Types of Asexual Reproduction: 1. Fission: o Binary Fission: Common in prokaryotes (e.g., bacteria) and some protists (e.g., amoebas). The organism divides into two equal-sized daughter cells. o Multiple Fission: Involves the division of one cell into multiple offspring simultaneously. Seen in some protists like Plasmodium. 2. Fragmentation: o Organisms break into pieces, and each piece can grow into a new individual. Common in certain invertebrates like starfish (Echinoderms). 3. Budding: o New individuals develop as outgrowths from the parent organism. Common in single- celled fungi (e.g., yeast) and some invertebrates. 4. Vegetative Propagation: o Plants produce new individuals from vegetative parts such as stems, leaves, or roots. Examples include strawberries and potatoes. 5. Parthenogenesis: o Development of embryos without fertilization. Found in some invertebrates (e.g., aphids), reptiles (e.g., Komodo dragons), and amphibians (e.g., certain frogs). Advantages of Asexual Reproduction: Efficiency: Requires only one parent and no need for finding a mate, which saves time and energy. Rapid Population Growth: Offspring are produced quickly and in large numbers when conditions are favorable. Stability: Effective in stable environments where adaptation is less crucial. Disadvantages of Asexual Reproduction: Lack of Genetic Variation: All offspring are genetically identical, which can be a disadvantage in changing environments or in the presence of diseases. Worksheet booklet Page of 78 Sexual Reproduction Definition: Sexual reproduction involves the combination of genetic material from two parents, resulting in offspring with genetic variation. Types of Sexual Reproduction: 1. Dioecious: o Individuals are either male or female. Examples include most animals, including mammals and birds. 2. Monoecious (Hermaphroditic): o Individuals possess both male and female reproductive organs. This can occur simultaneously or at different life stages. Common in many plants, some invertebrates, and certain fish. Modes of Fertilization: 1. Internal Fertilization: o Fertilization occurs inside the body of the female. This is common in most terrestrial animals and some aquatic species. 2. External Fertilization: o Fertilization occurs outside the body, usually in water or on a substrate. Common in many fish and amphibians. Embryonic Development: 1. Oviparity: o Embryos develop within eggs laid outside the body. Examples include birds, reptiles, and many insects. 2. Viviparity: o Embryos develop inside the body of the parent, receiving nourishment directly from the parent. Common in mammals and some reptiles. Advantages of Sexual Reproduction: Genetic Variation: Offspring have a mix of genetic material from both parents, which increases the potential for adaptation and evolution. Disease Resistance: Increased genetic diversity can make populations more resilient to diseases and environmental changes. Disadvantages of Sexual Reproduction: Energy and Time: Requires finding and attracting a mate, which can be time-consuming and energetically costly. Slower Reproduction: Generally involves longer generation times and fewer offspring compared to asexual reproduction. Historical Context Early Life: For the majority of Earth's history (from about 4 billion years ago to 1.2 billion years ago), life forms reproduced asexually. Sexual reproduction evolved later and has since diversified across many lineages. Evolutionary Trends: Sexual reproduction likely evolved as a strategy to enhance genetic diversity and adaptability, which provides a significant evolutionary advantage. Summary Reproduction, whether asexual or sexual, is essential for the survival and continuation of species. Asexual reproduction offers efficiency and rapid population growth, but lacks genetic diversity. Sexual reproduction, while more energy-intensive, introduces genetic variation, allowing for greater adaptability and resilience. The diversity in reproductive strategies across the tree of life reflects the varying ecological pressures and evolutionary pathways of different organisms. Worksheet booklet Page of 78 Concept 11.2 Types of Asexual Reproduction Asexual reproduction is a fundamental biological process where organisms replicate without the involvement of another organism. This method of reproduction allows for rapid population growth and can occur across various domains of life. Here’s a closer look at different types of asexual reproduction and their benefits: 1. Fission Definition: Fission is the process where a parent organism divides into two or more equally sized offspring. Types: Binary Fission: o Description: In binary fission, the parent cell enlarges, duplicates its nucleus, and then divides into two equal-sized daughter cells. This process is common in prokaryotes (bacteria and archaea) and some protists. o Examples: Bacteria (e.g., E. coli), Archaea, and protists like amoebas. Multiple Fission: o Description: Multiple fission results in the formation of several offspring from a single parent. The nucleus divides multiple times before the cytoplasm surrounds each nucleus to form new cells. o Examples: Certain protists like Plasmodium (causes malaria) and multinucleate organisms such as Planctomyces. Benefits: Rapid Reproduction: Multiple fission allows for the rapid production of numerous offspring, making it advantageous in stable environments with ample resources. Applications: Model Organisms: Organisms that reproduce via fission, like E. coli, are used in scientific research to study the cell cycle and cellular processes. 2. Budding Definition: Budding involves the formation of a new individual from a small outgrowth or bud on the parent organism. The bud eventually detaches and grows into a new organism. Description: The new individual develops as an outgrowth from the parent, which is different from fission where the parent cell divides into equal parts. This process can occur in both unicellular and multicellular organisms. Examples: Unicellular: Yeast. Multicellular: Hydra, some cnidarians, and sponges. Benefits: Resource Efficiency: Allows organisms to reproduce without the need for mating, which can be advantageous in environments where finding a mate is difficult. 3. Fragmentation Definition: Fragmentation is a form of asexual reproduction where a parent organism breaks into pieces, each of which can develop into a new individual. Description: The fragments can grow into complete organisms, genetically identical to the parent. Can be intentional (for reproduction) or unintentional (as a result of damage). Examples: Worksheet booklet Page of 78  Intentional: Starfish, which can regenerate lost arms. Unintentional: Some worms and flatworms. Benefits: Survival Strategy: Allows organisms to regenerate lost body parts and reproduce even if a portion of the body is lost. 4. Vegetative Propagation Definition: Vegetative propagation involves the production of new plants from vegetative parts of the parent plant. Description: Involves structures like runners, suckers, or tubers that can grow into new plants. Often occurs in sedentary plants and helps them spread and colonize new areas. Examples: Runners: Strawberry plants. Tubers: Potatoes. Benefits: Efficient Spread: Enables plants to cover large areas quickly and reduce competition with parent plants by moving offspring away from the original site. 5. Parthenogenesis Definition: Parthenogenesis is the development of offspring from an unfertilized egg or gamete. Description: Often occurs in species that can also reproduce sexually, allowing them to switch between reproductive strategies based on environmental conditions. In some species, parthenogenesis determines sex, with males arising from unfertilized eggs and females from fertilized eggs. Examples: Invertebrates: Aphids, which use parthenogenesis during favorable conditions and switch to sexual reproduction when conditions worsen. Vertebrates: Some reptiles and amphibians. Benefits: Flexibility: Allows organisms to reproduce quickly and efficiently when conditions are favorable, while still having the option for genetic variation when needed. Summary Asexual reproduction allows for the rapid production of offspring and is highly efficient in stable environments. The various forms of asexual reproduction, including fission, budding, fragmentation, vegetative propagation, and parthenogenesis, provide different evolutionary advantages depending on the organism's ecological niche and environmental conditions. While asexual reproduction is advantageous for its speed and efficiency, sexual reproduction, which introduces genetic variation, plays a crucial role in adapting to changing environments and enhancing evolutionary potential. Concept 11.3 Sexual Reproduction and Life Cycle Phases Sexual reproduction involves the production of gametes through meiosis, where diploid cells divide to form haploid gametes. Fertilization of these gametes produces a diploid zygote, which develops into a new organism. The life cycle of sexually reproducing organisms can vary significantly between species, with some spending most of their lives in the diploid phase and others in the haploid phase. 1. Diploid-Dominant Life Cycles Description: Worksheet booklet Page of 78  Most animals, including humans, are primarily diploid. The majority of their life cycle is spent in the diploid phase, with gametes being the only haploid cells. Process: Gametes (sperm and eggs) fuse during fertilization to form a diploid zygote, which then grows into a multicellular diploid organism. Examples: Animals: Humans, mammals, birds. Benefits: Stable Genetics: Maintaining a diploid state provides stability in genetic material and allows for complex multicellular structures and functions. 2. Haploid-Dominant Life Cycles Description: Fungi and some protists spend most of their lives in a haploid state. The diploid phase is usually short-lived and often occurs only during sexual reproduction. Process: Haploid individuals produce gametes that fuse to form a diploid zygote. This zygote quickly undergoes meiosis to produce haploid spores, which then develop into new haploid individuals. Examples: Fungi: Many fungi, such as yeast and molds. Protists: Certain algae and slime molds. Benefits: Rapid Reproduction: Haploid stages can quickly adapt to environmental changes and reproduce efficiently. 3. Alternation of Generations Description: Plants and some algae and protists exhibit a life cycle that alternates between two multicellular stages: the diploid sporophyte and the haploid gametophyte. Process: Spores produced by meiosis grow into haploid gametophytes, which produce gametes. These gametes fuse to form a diploid sporophyte, which then produces spores through meiosis. Examples: Plants: Ferns, mosses. Algae: Certain types of green and brown algae. Benefits: Genetic Diversity: Alternation of generations allows for both asexual and sexual reproduction, maximizing genetic diversity and adaptability. Sexual Reproduction in Fungi Description: Fungi often spend most of their life cycle in a haploid state, with sexual reproduction involving complex processes. Process: o Plasmogamy: Fusion of the cytoplasm of two haploid individuals, forming a dikaryotic (two-nuclei) stage. o Karyogamy: Fusion of the nuclei within the dikaryotic stage, leading to a diploid zygote. o Meiosis: Produces haploid spores that disperse and grow into new haploid mycelium. Examples: Club Fungi: Mushrooms, where the fruiting body (mushroom) is the dikaryotic stage and produces spores through meiosis. Benefits: Worksheet booklet Page of 78  Genetic Variation: The complex lifecycle and various mating types contribute to high genetic diversity and adaptability. Monoecious and Dioecious Systems Monoecious (Hermaphroditic): Definition: Organisms possess both male and female reproductive structures in the same individual. Examples: o Plants: Many flowering plants, such as those with perfect flowers that have both stamens and pistils. o Invertebrates: Earthworms, which produce both eggs and sperm simultaneously. Benefits: o Efficient Reproduction: Increases the likelihood of finding a mate and can reproduce with any other individual of the same species. Dioecious: Definition: Organisms have separate male and female individuals. Examples: o Animals: Most vertebrates, such as mammals and birds. o Plants: Some plants, like holly, where separate plants produce either male or female flowers. Benefits: o Genetic Variation: Promotes genetic diversity through cross-fertilization and reduces self-fertilization risks. Evolution of Sexes and Gamete Size Isogamy vs. Anisogamy: Isogamy: Gametes are similar in size and function, found in some primitive organisms. Anisogamy: Gametes differ in size; typically, females produce larger, nutrient-rich eggs, while males produce smaller, mobile sperm. Evolutionary Insights: Anisogamy: The evolution of anisogamy likely resulted from different selective pressures on males and females, such as differing investments in offspring and parental care. Benefits: Adaptive Strategies: Different gamete sizes and reproductive roles enhance reproductive success and evolutionary fitness. Summary Sexual reproduction exhibits a rich diversity of strategies across different organisms, each adapted to specific environmental pressures and life histories. From the predominance of diploid stages in animals to the complex alternation of generations in plants, and the varied reproductive systems in fungi, these strategies ensure genetic variation and adaptability. The evolution of separate sexes and anisogamy further illustrates the intricate balance between reproductive efficiency and genetic diversity, driving the continuous evolution of life on Earth. Concept 12.1 The immune system has evolved complex mechanisms to protect organisms from pathogens and manage their microbiota. This evolution can be traced through plants, animals, and fungi, revealing significant convergent and parallel developments. Here’s an overview of the immune system’s evolutionary trajectory and the fundamental phases it shares across these domains: Origins and Evolution of the Immune System 1. Theories of Immune System Origin: Worksheet booklet Page of 78  Defensive View: The immune system evolved primarily to protect against invasive microorganisms. Microbiota Management View: Alternatively, the immune system may have originated to manage and balance the microbiota— the community of microorganisms living in or on an organism. Both views acknowledge that the immune system has evolved to distinguish between self and non-self entities, though the specifics of its origins may differ. Phases of the Immune Response 1. Recognition Phase: Purpose: To identify and differentiate between self and non-self entities. Mechanism: Utilizes pattern recognition receptors (PRRs) to detect microbe-associated molecular patterns (MAMPs) or pathogen-associated molecular patterns (PAMPs). PRRs: Found on cell surfaces and recognize broad features of pathogens rather than specific species. Examples: o Flagellin: A protein found in bacterial flagella, recognized by both plants and animals. o Lipopolysaccharides and Peptidoglycans: Glycan compounds found in bacterial cell walls. o Viral Coat Proteins and ssRNA: Unique to viruses, allowing detection by host cells. 2. Activation Phase: Purpose: To mobilize cells and molecules to respond to the identified pathogen. Mechanism: Triggered by the binding of MAMPs/PAMPs to PRRs. Responses: o Defensins: Antimicrobial peptides that disrupt pathogen membranes, found in both plants and animals. o Cytokines: Small proteins released by cells to signal and coordinate the immune response. They can activate additional immune cells and responses. 3. Effector Phase: Purpose: To eliminate the invading pathogen. Mechanism: Involves either direct destruction or death of affected cells. Responses: o Phagocytosis: In animals, macrophages engulf and digest pathogens within a phagosome. This can lead to inflammation and activation of the adaptive immune system. o Regulated Cell Death: In plants and fungi, infected cells undergo programmed cell death to limit pathogen spread. In animals, this can involve apoptosis or other cell death mechanisms. Detailed Phases Across Domains **1. In Animals: Recognition: PRRs detect PAMPs and MAMPs on pathogens. Activation: Defensins and cytokines are produced. Phagocytic cells, like macrophages, engulf and destroy pathogens. Effector: Pathogens are destroyed by phagocytosis or via apoptosis. **2. In Plants: Recognition: Similar PRR-MAMP interactions as in animals. Activation: Production of antimicrobial peptides and signaling molecules. Effector: Infected cells often undergo programmed cell death to prevent pathogen spread. **3. In Fungi: Recognition: PRRs detect PAMPs specific to fungi. Worksheet booklet Page of 78  Activation: Defensins and other antimicrobial compounds are produced. Effector: Pathogens are often eliminated through cell death mechanisms involving reactive oxygen species, membrane disruption, or apoptosis. Convergence and Parallel Evolution The immune systems in plants, animals, and fungi exhibit convergent evolution in several aspects: PRRs and Recognition: Similar mechanisms for detecting and responding to pathogens, despite differences in evolutionary history. Defensins and Antimicrobial Compounds: The production of antimicrobial peptides to disrupt pathogen membranes is a shared feature. Regulated Cell Death: Programmed cell death to limit pathogen spread, present in various forms across different organisms. Conclusion The immune systems of plants, animals, and fungi, despite their evolutionary divergence, share fundamental principles and phases. These include recognizing non-self entities, activating immune responses, and effecting the destruction of pathogens. This convergence highlights the efficiency and adaptability of immune responses across different life forms, reflecting their shared evolutionary pressures and strategies to cope with pathogenic threats. Concept 12.2 The innate immune system serves as the first line of defense against pathogens and is found across plants, animals, and fungi. Here’s a breakdown of its mechanisms and how it compares to the adaptive immune system, which is found primarily in higher animals like mammals. Innate vs. Adaptive Immune Systems 1. Innate Immune System: Characteristics: o Non-Specific: Acts against a broad range of pathogens without specific targeting. o Immediate Response: Activated quickly upon detection of a threat. o Components: Includes physical barriers, cellular responses, and molecular signals. 2. Adaptive Immune System: Characteristics: o Specific: Targets specific pathogens based on memory and recognition. o Delayed Response: Slower to develop but provides a targeted response. o Components: Involves immune cells that remember past infections for faster response upon re-exposure. Components of the Innate Immune System 1. Physical Barriers: Plants: o Waxy Cuticle: Composed of cutin and waxes, protects against microbial invasion and aids in water retention. o Bark: Provides additional protection in larger trees. Animals: o Cuticle: Invertebrates like insects have an exoskeleton made of chitin that provides protection. o Keratin: In vertebrates, scales, feathers, and fur are made of keratin, offering a barrier to pathogens. o Mucus and Cilia: In respiratory and digestive tracts, mucus traps pathogens, while cilia help expel them. o Eyelids and Tears: Protect the eyes from pathogens and debris. Worksheet booklet Page of 78 2. Cellular and Molecular Responses: Phagocytes: o Function: Engulf and digest pathogens and debris. o Examples: Macrophages and neutrophils in animals; similar cells exist in fungi and some plants. Cytokines: o Function: Signaling molecules that attract immune cells to the site of infection and modulate immune responses. Inflammation: o Purpose: Isolates damaged areas, recruits immune cells, and promotes healing. o Mechanism: Involves mast cells releasing cytokines, increasing blood flow, and enhancing vessel permeability. Response Mechanisms Across Different Kingdoms **1. Plants: Physical Barriers: Wax, cuticles, and bark. Cellular Responses: Cells can undergo programmed cell death to limit pathogen spread, similar to apoptosis in animals. **2. Animals: Physical Barriers: Skin, mucus, and cilia. Cellular Responses: Phagocytosis, inflammation, and release of antimicrobial peptides. Inflammation: Involves mast cells and a cascade of immune responses to manage infection and injury. **3. Fungi: Physical Barriers: Cell walls made of chitin. Cellular Responses: Similar to animals, fungi can use antimicrobial compounds and programmed cell death to manage infections. Mechanisms in Action Phagocytosis: Phagocytes engulf and digest pathogens, isolating them and preventing further spread. Insects and invertebrates use similar mechanisms, with cells that produce clots to counteract physical damage. Encapsulation: Involves surrounding pathogens to limit their spread, seen in both animals and fungi. Inflammation: Activated by mast cells in vertebrates, leading to increased blood flow, cell recruitment, and healing processes. Integration with Adaptive Immunity In vertebrates, the innate immune response often triggers the adaptive immune system, which provides a more targeted response to specific pathogens. Cytokines released during the innate response help activate adaptive immune cells, setting up a more precise defense mechanism. Conclusion The innate immune system is fundamental to all multicellular organisms, providing immediate and broad-spectrum protection against pathogens. While plants, animals, and fungi have developed similar strategies for defense, the specific mechanisms and responses can vary significantly. The integration of innate and adaptive immune responses in vertebrates highlights the complexity and efficiency of immune defense across different life forms. Concept 12.3 In animals the adaptive immune system is activated by the innate immune system. Phagocytic cells of the innate immune system, such as macrophages or dendritic cells, are the first to recognize a Worksheet booklet Page of 78 foreign particle. Proteins of the major histocompatibility complex (MHC) binds to the antigens of the foreign body and protrude from the phagocyte. The MHC-antigen complex activates cells of the adaptive immune system, which eventually fight the source of the foreign particle. T- cells form the main cellular response of the adaptive immune system in animals, sometimes referred to as the cell-mediated immune response. Each T cell is only set into action by a single, specific antigen. Likewise, memory T cells will only activate when this particular antigen is reencountered. The more antigens an organism encounters during its lifetime, the larger becomes its arsenal of different T cells that fight successive infections. The humoral immune response, also known as the antibody-mediated immune response, targets pathogens circulating in “humors,” or extracellular fluids, such as blood and lymph. Antibodies target invading pathogens for destruction via multiple defence mechanisms, including neutralization, opsonization, and activation of the complement system. Neutralization: Antibodies “neutralize” a pathogen by interfering with its ability to infect host cells. For example, when an antibody binds to the surface of a virus, it may impair the ability of the virus to attach to or gain entry into target cells, effectively inhibiting the infection. Opsonization: Antibodies function as opsonins, which “tag” pathogens for destruction. Specifically, the formation of the antigen-antibody complex attracts and stimulates phagocytic cells that engulf and destroy the pathogen. Complement: Antibodies can activate the complement system, which plays a role in both innate and adaptive immunity. The complement system is a sequential cascade of more than 30 proteins. With the help of antibodies, these proteins opsonize pathogens for destruction by macrophages and neutrophils, induce an inflammatory response with the recruitment of additional immune cells, and promote lysis (destruction) of the pathogen. Concept 13.1 Life History Strategies - Life history is the patterns of survival and reproductive events for a species - Basic demographics - Also known as the life cycle features of reproduction Worksheet booklet Page of 78  - Simplified life history Categories of life histories - Number of reproductive events: o Semelparous – individuals breed once in their life o Iteroparous – individuals (potentially) breed multiple times in their life - Duration of a generation o Several generations per year o One generation per year (annuals) o One generation over several years (perennials) - Timing of reproductive events o Defined seasons vs resource availability *These features are not exclusive (can find semelparous and iteroparous in annuals and perennials) Semelparity and iteroparity: Semelparous: - Death after reproduction is part of an overall strategy that includes putting all available resources into maximising reproduction at the expense of future life. - One individual will have an initial growth phase and then only a single reproductive event (e.g pacific salmon) Worksheet booklet Page of 78  - Agaves grow in arid climates with unpredictable rainfall and poor soils, agaves grow for years accumulating nutrients in its tissues. Until there is an unusually wet year. It then sends up a large flowering stalk, produces seeds, and dies. - In many other semelparous species (insects, some butterflies, cicadas and mayflies, arachnids, mullocks) Iteroparous: - Have multiple reproductive cycles and can therefore mate more than once in a lifetime (Human, female flatback turtle, eucalyptus trees, birds, most reptiles, virtually all mammals, and most fish, mollusks and other insects such as cockroaches) - Most perennial plants are iteroparous. Annuals: - Complete their life cycle in a year or less in strongly seasonal temperate latitudes, most annuals germinate or hatch as temp starts to rise in spring, grow rapidly, reproduce and then die before the end of summer (wildflowers, staple food crops (legumes, cereal grains)) - Can have other semelparous annuals (gypsy moth) - Can also have iteroparous annuals as well (European common field grasshopper) which breed multiple times within is short lifespan Perennials - Life cycle extended over several or many years - May have repeated breeding seasons at a predictable time each year Iteroparous perennials Semelparous perennials - Worksheet booklet Page of 78 Concept 13.2 Life history Trade-offs Fecundity and parental investment: - Fecundity is an organism’s reproductive capacity) the number of offspring it’s capable of producing) - Parental investment is the energetic investment into each offspring (e.g. egg size, seed size, amount of parental care) Inversely related - “Quantity vs quality” trade-off between number of offspring and a parent’s energetic investment in the individual offspring. - Organisms can have many offspring with a small energy investment, or few offspring with a large energy investment. - *general trend and not a universal rule* Growth and Reproduction: - Early reproduction strategy: o Short-lived, small in body size o Strategy is geared towards early energy going toward reproduction rather than growth o Reduces risk of not reproducing at all - Late reproduction strategy: Worksheet booklet Page of 78  o Long-lived, larger in body size o Strategy is geared toward putting energy into growth to a larger size where mortality rates are lower, than later in life in setting energy in reproduction. o Strategy carries a higher risk of not reproducing at all or to maximum capacity if death occurs early - Both growth and reproduction require a lot of energy - Trade-off between growth and reproduction - Growth is usually greatly slowed (if all energy is spent on growth) in the reproductive phase and vice versa Concept 13.3 R and k selected species: - K selection is the selection for traits that are advantageous in high density populations - R selection is the selection for traits that maximise reproductive success in uncrowded or low density populations (Births – deaths) - R and K selection species ( population growth ) follows logistic growth equation (see later in course) - - Worksheet booklet Page of 78  Population stability and functions: o Fluctuations can occur for biotic and abiotic reasons (e.g. first moose crash likely due to high predation by wolves o Second major highest crash due to harsh winter and food limitation Concept 14.1 Population - Understanding populations is critical across a broad range of ecology disciplines, both for fundamental understanding but also thinking about how we can better manage species environments. What is a population? A population is a group of individuals of the same species living in the same location. - These individuals will rely on the same resources. They’ll be influenced by similar environmental conditions - They’ll be interacting with one another. E.G. Over a large scale the Sierra cactus in Arizona - Can think of population of cacti as being within this environment or extending right across the Sa desert Over a medium scale, population of kangaroos (national park in Australia) Over a small scale, population of species of gut microbes living within your gut Boundary: The spatial extent of that population - Natural (e.g. lake, island) - Arbitrary (e.g. national park) - Match to the purpose of the study and the organism. When defining a boundary, we both need to think about the purpose of the study, but also the biology of the organism Properties of a population: - Size (Dynamic): How many individuals are in that population/ how that number of individuals changes overtime o Four basic processes that lead to changes in the abundance within a population ▪ Births ▪ Deaths ▪ Immigration Worksheet booklet Page of 78  ▪ Emigration - These four processes are fundamental to understanding the dynamics of populations. - Distribution: The extent to which individuals are spaced within a po