Fungal Body Plans and Regulation

Body Plans and Regulation in Multicellular Organisms

• Fungal body is called Mycelium, it's a network of thin, thread-like hyphae.
• Hyphae grow at apical tips, extending outward like roots.
• They create new tips by branching, which allows fungi to spread and absorb nutrients efficiently.
• Mycelium can be compared to an underground web that spreads out to capture food signals.
• The inner portion of the mycelium focuses on resource processing via external digestion and bulk transport of nutrients.
• The outer portion of the mycelium focuses on exploration and expansion as apical tips search for new food sources.
• Tropism is movement toward or away from a stimulus.
• Autotropism is movement in response to self.
• Positive autotropism involves dense hyphal networks that form where digestion occurs.
• Negative autotropism avoids overcrowding to explore new territory and discover new resources.
• Apical tips are the points where hyphae grow via extending forward, laying septa (walls), and branching to maximize growth.
• Fungi can adapt and grow toward food sources due to modular body plans.
• Meristems are plant growth zones, similar to stem cells in animals.
• Totipotent cells divide rapidly and become any type of plant cell.
• Auxin regulates apical dominance by controlling shoot growth and suppressing lateral buds (branches).
• High auxin prevents side branches, while removing the shoot tip initiates branching with no auxin.
• Auxin moves by polar transport (directional movement).
• Proton pumps are used to manage pH, as Auxin enters as HA (neutral) and exits as A- (charged), needing transporters.
• Bulk flow is powered by ATP.
• Phototropism is growth toward light in shoots or away from light in roots.
• Auxin moves to the shaded side of a shoot, causing cells to elongate, and the shoot bends toward the light.
• Plants absorb red and blue light and reflect green light.
• The direction of sunlight for phototropism is detected by blue-light receptors.
• Root tip zones consist of the meristem zone (cell division), the elongation zone (cells stretch), and the differentiation zone (cells specialize).
• Positive phototropism is exhibited by shoots by growing toward the light.
• Negative phototropism is exhibited by roots by growing away from the light.
• Auxin inhibits root elongation, so the top cells grow more than the bottom ones.

Body Plans and Regulation in Multicellular Organisms 2

• Bilateral symmetry is division along a single plane with two mirror-image halves that allows directional movement, stopping and turning quickly and efficiently.
• Radial symmetry is division into equal parts along any plane that enables non-moving/slow-moving organisms to distribute sensory receptors.
• Nerve nets are interconnected neurons capable of simple sensations and behavior.
• Ganglia are clusters of neurons that provide localized processing power and signal transduction efficiency.
• Brains provide complex processing, behaviors, and learning by allowing large processing and storage.
• Homeostasis is maintained with constant input and output to keep conditions stable, requiring energy.
• Cellular homeostasis is the regulation of internal cell conditions (e.g., pH, ion concentration, energy levels) on a single-cell scale using membrane transport, signaling pathways, organelle function, or gene expression.
• Cellular homeostasis aims to keep a cell functional and alive through external changes.
• Organismal homeostasis is the regulation of the internal environment of the whole organism on a multi-system scale via the nervous and endocrine systems to maintain stable conditions for all cells.
• The scope of cellular homeostasis is local, while organismal homeostasis is systemic.
• Cellular control is often autonomous, while organismal control is centrally regulated.
• Sensor detects changes, a control center determines the response, and an effector responds.
• Set Point is the range over which the function is normal.
• Positive feedback during heat stroke has a runaway effect.
• Negative feedback such as sweating and shivering is designed to bring the body back to its set point.
• The central nervous system includes the brain and spinal cord or ganglia.
• The peripheral nervous system is composed of nerves to sensory organs and muscles that control voluntary and involuntary processes.
• The autonomic nervous system maintains homeostasis.
• The parasympathetic nervous system promotes "rest and digest" to constrict pupils, slow heart rate, constrict airways, and inhibit glucose release.
• The sympathetic nervous system is for "fight or flight" and causes the pupils to dilate, inhibits salivation, increases heart rate, and relaxes the bladder.
• Hormones act as external signals to a cell.
• Signal transduction happens when a cell converts a hormone signal into a response.
• Insulin binds to its receptor and triggers glucose uptake.
• Hormones are systemic messengers released by endocrine glands into the bloodstream.
• Endocrine glands maintain organismal homeostasis by coordinating multiple cells/tissues.
• Signal transduction ensures only target cells with the correct receptors respond.
• Adrenaline triggers fight-or-flight effects via signal transduction pathways.
• Hormones are key regulators in homeostatic feedback loops.
• Negative feedback loops happen as Hormone levels adjust based on the body's needs.
• Transduction ensures a coordinated, efficient response to maintain internal balance.
• The hypothalamus is the main integrating center and releases hormones acting on other tissues.

Responding to Environmental Signals: Gravity

• Gravitropism refers to a plant's growth response to gravity.
• Negative gravitropism leads to growth against gravity (shoots go up).
• Positive Gravitropism leads to growth towards gravity (roots go down).
• High auxin causes shoots to elongate.
• Auxin facilitates elongation by creating osmosis via More salt/sugar in the vacuole that increases turgor pressure.
• This causes Auxin gene expression changes to make more proton pumps.
• Proton pumps pump protons into the cell wall that lowers pH which activates expansins and weakens crosslinks between cellulose fibers and elongates.
• Auxin inhibits root cell elongation, with "top" cells elongating and "bottom" cells inhibited.
• Fruiting bodies grow upright so spores can drop down and spread effectively.
• Fungi detect "up" by using dense particles (vacuolar crystals or lipid bodies) like plants.
• Particles act like statoliths in plant cells as they shift position when orientation changes.
• Shifts trigger a signal transduction pathway (mechanoreceptors or ion channels) that leads to growth direction changes.
• Fungi adjust hyphal growth direction and cell elongation after disturbances to restore vertical growth.
• Some fungi exhibit gravitropic bending similar to plant shoots.
• Sensory Receptors and Organs convert physical and chemical stimuli to electrical signals.
• Mechanoreceptors sense gravity and movement.

Sensory Reception

• Hair cells transduce pressure to an electrical signal.
• Bending of stereocilia projections causes pressure to open K+ channels, leading to a K⁺ influx and depolarization.
• Voltage-gated Ca2+ channels open to trigger neurotransmitter (NT) release.
• Statocysts are gravity-sensing organs that enable invertebrates to sense gravity changes.
• Gravity makes statoliths settle against certain hair cells, which respond by bending and activating mechanoreceptors.
• Nervous system signals indicate which way is "down."
• Semicircular Canals sense head movement through one canal per plane of movement that enables nodding, shaking, and tilting.
• Otolith detects horizontal and vertical movement and gravity.
• Hair cells and mechanoreceptors detect sound.

Bulk Flow 1: Nutrient Acquisition

• Increased ATP demand is first met by using stored ATP and creatine phosphate (short bursts).
• Next, anaerobic glycolysis breaks down glucose without oxygen for quick ATP and makes lactic acid.
• Lastly, aerobic respiration uses oxygen to make ATP from glucose and fat.
• Myoglobin in muscle helps store and release oxygen.
• Adrenaline spikes mobilize glucose from the liver and fatty acids from fat via Glucagon increases which promotes glucose release from glycogen stores.
• The process of digestion includes ingestion, breakdown, absorption, and elimination.
• Mechanical digestion includes grinding (teeth) and mixing (stomach) of the foregut.
• Chemical digestion includes the presence of amylase and lipase in the mouth which breaks down fats and carbohydrates.
• Enzymes such as HCl and proteases in the stomach break down proteins.
• The secretions in the small intestine and aided organs help with digestion.
• The components are absorbed via the presence of villi, microvilli, and capillaries.
• The large intestine has absorption for water, ions and essential nutrients/vitamins.
• Complete digestion happens via two openings (mouth and anus) with a one-way flow.
• Incomplete digestion happens via one opening (mouth is anus) with a two way in/out flow.
• External digestion is where fungi secrete enzymes into their surroundings to break down complex organic matter.
• The small molecules are then absorbed by the cell walls.
• Hyphal networks penetrate substrates to access resources efficiently.
• Some fungi exhibit Mycorrhizae with plants which provides them sugar in exchange for minerals, or Lichens with algae/cyanobacteria
• Decomposers break down dead matter, releasing CO2 through respiration.
• Fungi returns carbon to the ecosystem by releasing it from complex molecules.
• Some fungi store carbon in their biomass or in soil via networks.
• Mycorrhizal fungi help plants fix more carbon, indirectly supporting photosynthesis.

Bulk Flow 2: Turgor Pressure

• Acquisition happens when Fungi release enzymes, digest nutrients externally before absorbing the nutrients through hyphal tips.
• Nutrients move through the mycelium via cytoplasmic streaming, septal pores or Turgor pressure.
• Lateral roots branch from a cell layer just inside the endodermis called the pericycle which are signaled via auxin and environmental cues.
• Roots slow and proliferate to absorb surface area.
• Water and solutes are forced to pass through cell membranes for selective uptake with the endodermis.
• Strengthening by lignin allows supports to resist collapse in the xylem.

Water Movement

• Pholem is connected by plasmodesmata.
• Transpiration is evaporation of water from leaf stomata that relies on water molecules that stick to each other (cohesion) and water molecules that stick to xylem walls (adhesion).
• Tension that stems from evaporation pressure pulls water and minerals upwards.
• Plants acquire carbon via CO2 uptake and have CO2 enter chloroplasts to fix via photosynthesis.
• The carbon sink is where carbon is stored of used as seen with growing tissues, storage organs, or when they shift with season and plant stage.
• The sugars enter with the waters to build pressure in the source, and sugars unload in the sink.
• The water movement is high to low pressure.
• The source is a storage organ in the spring or a green leaf during the summer/fall time.
• The sink is growing shoots or roots during the appropriate seasons.

Bulk Flow 3: Animals

• Simple animals that are small, thin, and live in moist environments can just diffuse nutrients.
• Insects use a tracheal system to breathe, or hemolymph via an open circulatory system to move nutrients
• Animals can rely on both diffusion to get nutrients into gases, or rely on a circulation system
• Open circulatory systems work well for smaller/less active animals, and have low efficiencies/simplicities for all organisms as well

Bulk Flow 4: Animals

• Low oxygen levels, harder travel, and chance for lung collapses are challenges faced by aquatic animals.
• Aquatic animals undergo a countercurrent exchange that maximizes the oxygen uptake in the gills.
• More alveoli/thin walls allow for short diffusion paths allowing oxygen levels to dissolve.
• Contraction and expansion (down/up) happens when the diaphragm contracts and expands ribs.
• Proteins need for elastin are found in the lungs, skin, blood, and help with inhalation and recycling.
• Damage of the walls during inhalation/exhalation happens via toxins and can cause a collapse.
• Four chamber Hearts use the most O2 out of any other circulatory system.
• Gap junctions that cardiac cells function with allow signals to beat directly into all cells.
• Desmosomes are cells that connect muscle cells that connect the arteries.

Gas Exchange

• Walls of arteries are thick/elastic and maintain pressure throughout the cycle.
• Pressure in the veins is low, and high elasticity helps with muscle pump, while a Yes to pressure is a factor.
• Hemoglobin carries 4 subunits of Heme groups, while Myoglobin carries 1 with structure of cells in the lungs and tissues.
• The shapes of the charts are determined by their functions, which both bind to O2.
• Hemoglobin adjusts itself based on the tissue that's needed.
• Cooperativity helps hemoglobin to be highly responsive.
• There are two main types of CO2, which are flat loading and steep unloading.

Water Balance and Homeostasis

• Fungi maintain water balance by taking up osmosis.
• They also absorb water into the cell walls with the chitin.
• They also need to access the water with rich areas of tissues and moist environments.
• Energy connection to them includes water enzymes and functions.
• A filamentous hyphae allows the water to maximize and uptake nutrients.
• They use a resource like the water to guide the hyphal growth and uptake.

Plant Structures

• Plants are separated between Bryophytes and Vascular Plants.
• Bryophytes use no xylem/pholem while Vascular Plants do.
• Gametophytes use haploid, and sporophytes use diploid.
• Light/Carbon interactions are split into 2 functions.

C3, C4, and CAM

• C3, C4, and CAM photosynthesis are all different ways to balance carbon dioxide intake with water loss via gas exchange.
• C4 and CAM plants can close their stomata, which means less water and CO2.
• Rubisco drives up the energy, Wastes energy and carbon in the process.
• The strategies depend on climate.

Water Balance and Homeostasis 2

• Excretory systems remove waste (especially nitrogenous waste from protein breakdown, like ammonia, urea, or uric acid), maintain water and ion balance and maintain pH, volume, and composition of body fluids in a safe range.
• Interstitial fluids are the fluid between cells.
• Kidneys solve Filtration, Reabsorption, & Secretion of various fluids in systems, via 3 processes.
• Hormones play a role in helping with water balance.
• Loops of Henle, concentrate in collecting the water.
• ADH (antidiruethic) increases reabsorption in collecting duct which makes the duct water, but will leave fluids in other systems.

ADH

• Makes ducts more permeable to water in return back.
• Is realized when youre dehydrated or have a blood osmorality so high it cant be regulated naturally.
• Other gains/loses depend on urine, hormones (ADH, aldesterene)
• Stomata helps with waterloss and reglation for plants.
• Organisms also maintain a certain level of protection (cell wall or skin).
• Aquatics gain contact with their skin that maintains them.
• While land contains concentrated 500s and kidney functions to assist with the process.
• Gills must maintain some sort of osmosis for H2O that helps their bodies function to exchange H2O.

Water Balance and Homeostasis 3

• Freshwater is in Waterflow in the ions.
• Waterflows are able to also diffuse with the active gells and systems in water systems.