Theme 3-5 A - Terrestrial Animals PDF

Theme 3 (animals): Environment Matters: life in the water and on land TERRESTRIAL Animals Animals originated in the oceans Terrestrial (land-dwelling) animal lineages are descended from ancestors that independently left the aquatic environment to live on land Earliest recorded te...

Theme 3 (animals): Environment Matters: life in the water and on land TERRESTRIAL Animals Animals originated in the oceans Terrestrial (land-dwelling) animal lineages are descended from ancestors that independently left the aquatic environment to live on land Earliest recorded terrestrial animal 428 My old – a myriapod – but first transition must have taken place earlier 1 Terrestrial Animals Relatively few terrestrial animal taxa Gastropods, arthropods (insects, arachnids, myriapods, crustaceans) nematodes, annelids, amniote vertebrates, etc However, some of these taxa encompass many species – terrestrial environments provided many evolutionary opportunities 2 Terrestrial Animals Onychophora – the only completely terrestrial animal phylum 3  Conditions on Land The terrestrial environment makes different demands from the aquatic environment Main factors affecting terrestrial animals: Gravity – maintenance of posture, locomotion Air – obtaining oxygen, much less dense than water Locomotion sound effectively Sensory modes does - not carry Thermal properties has more thermal capacity Water – always a limiting resource -water sheild Sunlight – exposure to UV acts more bic water as exposure - 4  Life on Land Some requirements for a terrestrial life include: Desiccation avoidance water loss Mechanisms: reduce water loss - managing replace lost water hibernation * not weather Desiccation tolerance (aestivation, life cycles) Excretion with limited water loss Gas exchange with air Internalized gas exchange organs to avoid desiccation (lungs, book lungs, tracheal systems) 5  Desiccation And The Environment – Terrestrial Animals Terrestrial animals are all, to a greater or lesser extent, constrained by the availability of water This has wide-reaching effects upon their anatomy, behaviour and physiology 6  Desiccation And The Environment – Terrestrial Animals Constant water loss through ____________: evaporation Across wet respiratory membrane Across surface of skin (inevitable) Water loss in _____ urine and ______ rus Some species lose water through _____________________ thermoregulatory methods (sweating, panting) egsweating 7  Desiccation And The Environment – Terrestrial Animals Requires: _____________ Of outer layer of body waterproofing Keratin Wax Minimal exposure of gas-exchange and digestive surfaces to ___ Internal placement - taking in cold air through nose causes condensation nose runny 8  Nitrogenous Wastes Toxic _________ ammonia (NH ) produced in every cell 3 of the body by catabolism of amino acids and nucleic acids Reptiles, birds and insects convert ammonia to _______ vic acid – very low water-solubility, semi- solid nitrogenous wastes can be excreted while ______________ conserving water 9  Desiccation And The Environment – Terrestrial Animals Mammals are _______ createlic – convert ammonia to less-toxic ____, urea but must lose water in excretion ______________ Loop of Henle aids in conservation of water in mammals Produces concentrated urine – ___________ hyperosmotic to blood The longer the loop, the better for water water is taken getting conservation - back more 10 concentration solution Curines Desiccation And The Environment – Terrestrial Animals get doniek↑ Kangaroo rats: Desert-adapted rodents Very long ______ Loop of _____ Henle Produces small quantity of highly ___________ hyperosmotic urine (22.5% of daily water loss – for a human, daily water loss in urine is 57.7%) Metabolic water very important 11  Desiccation And The Environment – Insects small animal = TSA (more surface for exchange ( Must deal with small size (___________________ cube-square relationship favours desiccation by evaporative water loss from body surface) and inevitable evaporative loss from wet respiratory surfaces in _______ trachea Waxy outer layer of ______article minimizes evaporative water loss from body surface Spiracles permit closing of _____________, tracheal system cuts down on evaporative water loss - things in desserts have thicker vaxy layer 12  Desiccation Tolerance Terrestrial tardigrades live in water films in damp environments _____________ cryptobiosis – formation of resistant stage (tun) in response to environmental challenges (dehydration, sub-zero temperatures) ____________ Anhydro biosis – when slowly desiccated, resistant tun formed – when re-hydrated, tardigrade returns to active state https://www.americanscientist.org/article/tardigrades# 13  Rotifer life cycle Biology, Nelson 2013 Unstressed Environment (moist) Stressed Environment (dry) Parthenogenesis (clones) Sexual Reproduction (genetic variability) ADULT FEMALE (2N) ADULT MALE (1N) Haploid (1N) egg Haploid (1N) sperm Diploid (2N) egg Diploid (2N) zygote (desiccation resistant) 14  Aestivation Aestivation – prolonged period of ________ depressed __________ metabolism to avoid seasonal heat and drought Desert-dwelling spadefoot toads spend most of their adult lives buried deeply Metabolism depressed Only emerge when it rains, to breed https://terrestrialecosystems.com/cocoon-forming-desert-frogs/ Some desert-dwelling frogs secrete a cocoon while aestivating Only nostrils left open Metabolism depressed Can spend up to 2 yrs buried 15 More requirements for a terrestrial life:  Desiccation avoidance  Mechanisms: reduce water loss replace lost water  Desiccation tolerance (aestivation, life cycles)  Excretion with limited water loss Internal bulk flow of fluids and gasses Gravity may be a factor Gas exchange with air Internalized gas exchange organs to avoid desiccation (lungs, book lungs, tracheal systems) 16  Gas Exchange With Air Disadvantages of breathing air diffuse into air as easily as into water CO2 does not _______ Inevitable ___________________from evaporative water internal respiratory surface, which must be kept wet Advantages of breathing air 21% O2 – much greater than water Atmospheric O2 diffuses much more rapidly Bulk flow of air (ventilation) requires less muscular effort viscosity Low _________ density Low _________ 17 Gas Exchange With Air - Trachea tracheal system– Insect ______________ delivers air directly to tissues (via interstitial fluid) Moist exchange surfaces internal 18 Desiccation And The Environment - Trachea 19 Gas Exchange With Air - Trachea Form of ____ bulk ____ flow system for air Biology, Nelson 2013 20 Gas Exchange With Air Vertebrate lungs – bulk ___ __________ flow of air to respiratory membrane Moist exchange surfaces internal Requires muscular effort (__________) ventilation 21 More requirements for a terrestrial life: Protect gametes from desiccation fertilization without water (internal) Protect embryo from desiccation Aquatic larvae, thick covering on egg/embryo Amniote vertebrates ( birds/reptiles/mammals) – amniotic membrane Temperature extremes Avoid - thermoregulation Tolerate Constraints on sensory systems Chemosensors Mechanosensors – tympanal organ, vert. middle ear Support body weight Robust skeleton SA/V relationships, size, stance 22  Amphibians – Reproduction in Water In vertebrates: Amphibians lay ___________ amniotic eggs in the water Embryos can exchange gasses, wastes with aquatic environment Adult form can live on land 23 Reproduction on Land - The Amniotic Egg In vertebrates: The __________ amniotic egg provides an aqueous environment for the developing embryo Requires ________ internal _________ fertilization Requires ________ uricotely ______________ Extraembryonic ____________ membranes support developing embryo Shell porous to air, possibly to water 24 Requirements for a terrestrial life (cont’d):  Protect gametes from desiccation  fertilization without water (internal)  Protect embryo from desiccation  Aquatic larvae, thick covering on egg/embryo  Amniote vertebrates ( birds/reptiles/mammals) – amniotic membrane Temperature extremes Avoid - thermoregulation Tolerate Constraints on sensory systems Chemosensors Mechanosensors – tympanal organ, vert. middle ear Support body weight Robust skeleton SA/V relationships, size, stance 25  Reasons For Thermoregulation Most terrestrial animals ______ regulate their body temperature when possible Through _________________ metabolic activity Through __________ behaviour · Animal body temperature range ~4°C - 40°C 26  Reasons For Thermoregulation Thermoregulation can be quite expensive within that 4°C - 40°C range – why expend the energy? The formation of ice crystals (< 0°C) within a cell kills it __________________: Enzyme effectiveness Active site changes shape outside of narrow range of temperature and ph, enzyme loses ability to catalyze metabolic reactions > 45°C – proteins denature 27 Reasons For Thermoregulation Performance depends upon _________________ biochemical processes Animals regulate body temperatures within rangeS allowing ________________ optimal performance 28  Ways Of Thermoregulation _________ Endother my – the production of sufficient metabolic heat to warm the tissues significantly __________ Ectother my – insufficient heat from metabolic activities to warm tissues significantly; heat must be exchanged with the environment 29  Ways Of Thermoregulation ________ – allowing body temperature to vary Heterothera any __________ – tightly regulating body temperature around an unvarying mean These define two axes across which thermoregulatory strategies form a continuum 30 Ways Of Thermoregulation _________ – Endotherms metabolic rate changes with temperature in order to maintain a constant body temperature – an energetic cost _________ – Ectotherms metabolic rate changes directly with body temperature, which changes with environmental temperature – a potential ________ liability (loss of performance) 31  Heat Exchange With The Environment ________ Conduction – direct heat transfer by contact – air conducts heat poorly, water well, so gill-breathing aquatic organisms tend to be _________ isothermic with the water in which they swim _______ Radiation – transfer of heat as long-wave light – not very effective as a heat sink at biological temperatures, but radiative sources (the sun) very effective for heating up 32  Heat Exchange With The Environment _________ Convection – transfer of heat by a moving medium – air or water flowing over an organism carries heat away or delivers it _________ Evaporation – energy consumed by change from liquid to gas; effective way to carry heat away 33 Heat Exchange With The Environment _________ Ectothermic animals can thermoregulate by using these modes for ____ heat ______ with the exchange environment Basking lizard regulates body temperature largely through exposure to radiation, convection, conduction Metabolically _____ cheap 34 Countercurrent Heat Exchange Cold-climate terrestrial endotherms can conserve heat by using _____ counter- __________ current heat ________ exchange ________ structures – warm blood in efferent vessels heats cool blood in afferent vessels Regional heterothermy - colder extremities losesheat totherbloodresa - 35  Torpor And Hibernation Torpor reduces energy demands in small endotherms during periods of low or high environmental temperatures, or resource unavailability Body temperature set point _____________________________ drops ______________ Metabolism depressed un torpor 36  Torpor And Hibernation I- Chipmunk _________ is Hibernation a seasonal version of ______, torpor undertaken during seasonal periods of low temperature 37  Endothermy In Insects Bees and some other flying insects are _____________ heterothermic _________ endotherms – generate sufficient heat by the action of the flight muscles to maintain a high constant temperature in the thorax Tend to be furry 38 Freeze Tolerance and Freeze Avoidance ______________ Freeze avoidance - some ectotherms can _______ supercool their ECF – goes below 0° C without freezing (mainly to be marine) environment artic fish has I - stable Normally ______________ Freeze tolerance - some terrestrial ectotherms canextracellra allow the bulk of their ECF to freeze for extended periods High intracellular osmolality depresses freezing point Control of ice nucleation in ECF prevent large i crystals - fom forming 39 Requirements for a terrestrial life (cont’d):  Protect gametes from desiccation  fertilization without water (internal)  Protect embryo from desiccation  Aquatic larvae, thick covering on egg/embryo  Amniote vertebrates ( birds/reptiles/mammals) – amniotic membrane  Temperature extremes  Avoid - thermoregulation  Tolerate Constraints on sensory systems Chemosensors Mechanosensors – tympanal organ, vert. middle ear Support body weight Robust skeleton SA/V relationships, size, stance 40  The Senses in Air and Water Air and water have different physical properties – sense organs must evolve to accommodate this Air ________ transmits _____more light effectively than water Water conveys _________ chemical _______more signals effectively than air The ______ speed __ of _____is sound far greater in water than in air Being able to sense _____ which ___ way __ is ____ down is very important in terrestrial environments 41  Chemosensors Chemosensory organs – require ___wet _____ surface for adsorption of air-borne chemical particles Insect antennae have minute channels lined with moist adsorptive tissue -wet - pick up scent particles 42 Chemosensors Terrestrial vertebrates have moist _______________ olfactory epithelium and taste buds in oral cavity 43 Hearing Sound does not transmit easily from air to water (___) EOF Sensing soundwaves by terrestrial animals must take this into account Insects – ________ tympanal ______ organs – air on both sides, nerves (mechanoreceptors) pick up vibrations 44 Hearing and Balance Vertebrates: Organs for _______, hearing and for sensing __________ acceleration and which direction is ____ (vestibular down labyrinth) are located in the inner ear It’s very important to be able to tell which way is down on land  Hearing Hearing in fish – inner ear can pick up vibrations through tissues In fish, hyomandibular bone suspends lower jaw 46  Hearing In tetrapods, middle-ear bone(s) transform large amplitude eardrum ____________ vibrations (from air) to low-amplitude high-force vibrations transmitted to oval window of inner ear – amplifies vibrations so that waves are produced in fluid-filled cochlea 47  Support Body Weight Terrestrial animals are subject to gravity Volume (mass) of a terrestrial organism is a function of (linear dimension)3 Cross-sectional area of limb (support and strength) is a function of (linear dimension)2 All else being equal, as animals get biggerf body MASS would increase faster than the cross-sectional AREA of the limbs for support Thus, in terrestrial animals, if body and limbs scale proportionately/linearly with size........ at some point body mass exceeds the ability of the limbs to support it THUS, limbs must change disproportionately to body size as terrestrial animals get larger – allometric growth Aquatic animals are largely freed of this constraint -water supports the body mass (neutral buoyancy) 48 Support Body Weight - thicker limbs 49  Allometry Allometric (differential) growth is characteristic of most animals _______________________ Different parts of the body grow at _________ different _____ rates with increase in overall ____ Size It is also an evolutionary phenomenon associated with trends in increasing or decreasing body size in a lineage 50  Allometric Relationships By Charles J. Sharp - Own work, from Sharp Photography, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=38260517 52  Support Body Weight - Allometry From Brennan et al. 2021 - Syst. Biol. 70(1):120–132, 2021 Example: evolutionary allometric increase of humerus thickness in Varanus V. komodoensis – 3 m, 70 kg V. acanthurus – 0.7 m, 0.34 kg Humerus thickness in the species of Varanus displays positive allometry – the humerus of V. komodoensis is thicker than we would expect from a simple linear increase in thickness with increase in length 53 Support Body Weight - Allometry The ant is exhibiting In the real world, the isometric growth limbs of the larger specimen would not be of sufficient thickness for efficient locomotion Limbs must grow allometrically to support increasing body weight with increasing size 54 Support Body Weight The ant is exhibiting ________ isometric growth in the real world, the limbs of the larger specimen would not be of sufficient thickness for efficient locomotion Limbs must grow ___________to allometrically support increasing body weight with increasing size 51  Support Body Weight Fred the Oyster (CC BY-SA 4.0) Sprawling limb Erect limb configuration configuration requires less energy associated with to maintain - endothermy ectotherms Supports weight more efficiently Wikimedia commons 55 Iker Cortabarria (CC BY-SA 2.0)  Hard Skeletons Skeletons found in aquatic and terrestrial animals Two types of hard skeleton: _________ exoskeletons (external) and ________________ endoskeletons (internal) Functions: Provide attachments and leverage for ______ muscles – force transmission Transmit _______________ compressive stress to substrate Provide framework for tissues of body Act as ____________ mineral bank for physiological requirements (vertebrates) Protection for delicate organs or whole body 56  Endoskeletons In vertebrates, composed of bone and cartilage ____ Bone – collagenous matrix mineralized by CaPO4 crystals dynamic and - in it well is alive Highly vascularised, matrix architecture supports scattered osteocytes Metabolically active Bears compressive stress well, shear stress not so well 57  Exoskeletons The arthropod exoskeleton: Consists of Chitin ____ – complex polysaccharide May be impregnated with calcium carbonate Composed of plates (______) tergal with joints between them Tergae mark segmentation of limbs and body Limb joints mobile Muscles are within the skeleton 58 Exoskeletons 59  Hydrostatic Skeletons Hydrostatic skeleton: 2 layers of muscle Volume of fluid enclosed by ________________ Longitudinal and circular thicker ~ - thinner incompressible but pressurized when muscle contracts Fluid _______________ Muscular “container” changes shape with contraction of different muscle layers Organ Animal’s whole body 60  AQUATIC Animals Advantages Water supports the body Affects size, stance and skeleton C gravity l does not affect do not have much weight to carry Desiccation is a lesser threat Stable and mild temperatures Metabolic waste removed by water ↳ a ammonia diffused into water Sound transmits well from water to body 61  Challenges of living in aquatic environments: Water is _____ dense Takes energy to displace harder for smaller Water is _________ viscous ; animals A layer clings to the body Water has __________ low oxygen content (~1 – 2%) compared to air (~21%) Oxygen levels in water vary greatly with other parameters Water has high ________ thermal ____________ conductance 25x that of air ↳ hard to stay warm b/c heat into water dissipates 62  - Endoskeletons - terrestrial & Firmly attached girdles Enclosed ribcages - Sternum · ~ not connected not attached Endoskeletons - aquatic Ribcages not enclosed Loosely attached girdles ·b cage a 63 Wikimedia commons public domain dig ou Aquatic animals can become much bigger than terrestrial animals The biggest aquatic animals are _____________ air-breathers ; access to a more rich resource oxygen 64  Salt and Water Balance Excess salt in the diet is a problem for marine tetrapods Marine birds and reptiles excrete excess salt through ____ salt ______ glands associated with upper respiratory tract or eyes Marine mammals can produce highly _____________ hyperosmotic _______ Urine 65  Being warm in aquatic environments Water is a good heat conductor – aquatic organisms are mostly ____________ heterothermic __________ ecto therms Aquatic homeothermic endotherms must (fat) ________ insulate with blubber or a waterproof pelage car hair or I , , wool blubber 66  Being warm in aquatic environments __________ Insulation– fur, feathers, fat Respiratory medium – breathe air___ – allows higher metabolic rate; also, air is poor conductor of heat from body Aquatic endotherms utilize ____________________ counter-current heat exchange – allows outbound blood to heat inbound blood – retains heat by maintaining gradient along length of organ 67  Theme 3II recap Terrestrial environments impose new challenges Desiccation, gas exchange, reproduction, support/locomotion, bulk flow, sensory, temperature extremes, light/UV, excretion.... Aquatic environments also impose challenges Density/viscosity, O2 content, thermal conductance 68  Theme 4: Homeostasis to Thrive and Survive Osmoregulation, Circulation, Gas exchange and pH Homeostasis – the maintenance of a ______ stable ________ internal ___________ environment suitable for metabolic processes, through responses to deviations from this stable state Significance Biochemical reactions sensitive to: __________, temperature __, pH [______], solute [_____], water _______ pressure Organisms must regulate many internal variables 6 02 CO2 nutrients, gasses, pH, waste products, water/solutes, volume, pressure, , temperature Conitrogenous ↳ now salty is ↳ gas exchange waste insidethe cell 1  Homeostasis – Negative Feedback Loops Negative Feedback __________________– homeostasis is maintained by regulating physiological variables with reference to a __________ setpoint (generally in the integrator) 2 Homeostasis – Negative Feedback Loops 3 Homeostasis – Cell Location __________– Cell location implications for how homeostasis is approached ___________ External cells must face the environment: Sometimes dead (i.e. superficial layers of skin) Sometimes produce protected by an - daughter cells older acellular cuticle push wells - Calve( daughter up as new daughter alls are formed - ell s older daughter 4 becomes dead cells (dandwff) Homeostasis – Cell Location Cells of exchange surfaces must be alive – control access to _______ internal _________ environment Found inside the body, but dealing with aspects of the ________ external __________ environment Deal with wear and tear by Rapid __________ turnover Produce ___________ letual ________ to microbes environment Covered by ________ secretions to isolate them from the environment 5  Homeostasis – Cell Location Internal cells: homeostasis by organism regulates the ______ ____________ internal environment i.e. regulation of extracellular fluid _____________ solute content 3 ______ volume (circulating extracellular fluid) Reduces amount of work cells have to do to maintain homeostasis, if internal cells are not isoosmotic with the environment Enables them to specialize 6  Homeostasis topics _____________: Osmo regulation regulation of the internal osmotic (water/salt/waste) environment _________: circulation bulk flow of fluid within the body (water, solutes, nutrients, gasses) ____________: basexchange betweenbody and environment , fluid in bulk exchanging gasses with the environment flows alls ______________ pH regulation controlling the [proton H+] of body fluids 7  HOMEOSTASIS and OSMOREGULATION --concepts-- Diffusion – short distances, dissolved solutes __________- Fick's Law Diffusion Rate = D A dC/dX Osmosis and Water Potential _______________vs osmotic potential ___________ pressure ______________ water potential – tendency of water to move Due to osmosis, hydrostatic pressure, gravity, humidity, etc Hyperosmotic, hyposmotic, isosmotic Bulk flow – mass movement over long distances due to ___________ mechanical (__________) hydrostatic _________ pressure 8  Diffusion molecules Spread out (high to 102 ( _________________- Concentration gradient a spatial difference in the relative abundance of one type of molecule (or atom) ________ Diffusion - the tendency of molecules or atoms of one kind (say, a solute) to move from a volume in which they are relatively abundant to one in which they are relatively rare This is the same as moving down a concentration gradient It is due to random movement of the particles involved It results in the diminution of the concentration gradient and the establishment of an equilibrium 9  Diffusion Fick’s Law - Diffusion Rate Across a Membrane = D A dC/dX D = _____________– diffusion coefficient depends upon characteristics of solute and solvent, temperature etc. dX A = ____________ surface area of the membrane -membrane dC/dX: A dC – ___________ concentration difference across membrane dX – _________ thickness of membrane dC/dX is the force driving diffusion The ________ quantity of particles moving across dC the membrane varies with A, all else being equal 10  Osmolality ______ – total number of dissolved particles of osmoles solute per kg of solute solvent 1 mole NaCl dissolved in 1 kg of water yields _______ 2 moles of particles – ______Na Imole +, ______Cl 1 mole - ________ Osmolality – osmotic concentration of a solution, measured in osmoles 11  Tonicity Terms _________ hypoosmotic - of a solution, having a lower ________ osmolality than the reference solution pure water is __________ hypoosmotic to the red blood cell placed in it, which bloats 12  Tonicity Terms _____________ hyperosmotic - of a solution, having a higher ________ osmolality than the reference solution a strong saline solution is ____________ hyperosmotic to the red blood cell placed within it, which shrivels 13 Tonicity Terms __________ Iso osmotic - of a solution, having the same __________ osmolality as the reference solution a bath of physiological saline is _________ iso osmotic to the red blood cell placed within it, which stays the same 14  Osmosis The tendency of water to diffuse across a selectively permeable membrane towards the side of ______ greater ______ solute _________ concentration when the membrane is impermeable to the ______ solute * water follows salt 15 Semi-permeable membrae Osmotic potential ______________ (solute potential in plants) – force exerted on water generated by differences in solute concentration across a semi-permeable membrane Pure water has an ______________ osmotic potential of zero – highest osmotic potential possible Lower osmotic potential is a negative number (the more solute, the more negative the osmotic potential) Water moves from ___________to less negative __________ more negative volumes 16 Semi-permeable membrae ______________ pressure potential – hydrostatic (=_________) mechanical pressure affecting how water crosses membrane from volume of high osmotic potential to volume of low osmotic potential Pressure potential _______ opposed to low osmotic potential – flow of water across membrane decreased, reversed or stopped Pressure potential _________ added low osmotic potential – flow of water across membrane increased Pressures measured in Pascals (Pa - animals) or in Ψ (Psi – plants) 17 _____________ water potential – sum of osmotic potential, pressure potential, gravity etc. across a membrane Water moves from volumes of high ______________ water potential to volumes of low ____________ water potential HI POT LO POT SPM Water movement 18  Osmosis and the living cell OSASISS Fresh water (high osmotic potential) Significance to animals causes cells to swell Cells will _____________if shrink orswell not in an isoosmotic environment (without work on the cell’s part) Significance to plants Fresh water causes Cells will develop ______ turgor ________ pressure hydrostatic/turgor (hydrostatic) due to cell swelling Cell wall pressure, preventing further influx of and pressing against cell wall as water water enters, which limits further influx of water Se  Bulk Flow and Water Bulk flow of transport fluids in ________ animals requires application of _________________ hydrostatic pressure Affects exchange of water and solute between the bulk transport system and the extracellular fluid in ______________ closed circulatory systems 20  Bulk Flow and Water Animal example: _______________ Pressure potential exerted on blood in upstream side of capillary bed exceeds ________ osmotic ________ potential of extracellular fluid – water and solutes leave capillaries ______________ osmotic potential of blood in downstream side of capillary bed exceeds _______________ hydrostatic pressure of extracellular fluid – water and solutes re-enter capillaries 21  Osmoregulation in ANIMALS Fresh water (1 mOsm) vs salt water (1000 mOsm) vs extracellular fluid (300 mOsm) vary animals a in Osmoconformers vs Osmoregulators _____________ Osmoconformer strategies [Y] = [X] = [Z] Adjust osmotic potential of cells [Y] and extracellular fluid [X] to match environment [Z] [X] [Y] Examples: marine inverts, hagfish, elasmobranchs ↳ invertebrates jo [Z] cell _____________ Osmoregulator strategies: Alsomotic with the call Adjust osmotic potential of extracellular fluid [X] to match cells [Y] and regulate or protect [X] against the external [Z] Generally requires thick outer layer [Y] = [X] ≠ [Z] Examples: freshwater inverts and most vertebrates [X] [Y] 22 [Z]  Osmoregulation in ANIMALS The challenge of water/salt loss and gain Terrestrial animals (water loss) water dry lose water to environment Aquatic animals Marine (water loss) water salt Hyperosmotic (dry!) living in dry environment a ions penetrating if surrounded water your body even by Fresh water (water gain) to lose ions water to the salt Hyposmotic environment 23  Tonicity And The Environment – Water Dwellers Body fluid _______ osmolality varies among (bony fish) aquatic organisms Some marine groups are ________ isoosmotic with seawater – osmotically stable environment 24  Tonicity And The Environment – Water Dwellers not as salty as Marine bony fish - __________ o their environment hypoosmotic to environment, lose water and gain ions, especially through the ____ gills Drink _________ seawater to offset water loss ____________ Chloride cells in gills eliminate * uses energy Na+, K+ and Cl- from blood Produce ___________ small amounts of urine, conserving water, eliminating excess solute in faeces 25  Tonicity And The Environment – Water Dwellers Freshwater bony fish – ___________ hyperosmotic to environment, lose ions and gain water, especially through the gills Do not drink Produce large amounts of ____________ dilute vrine Must replace ions from food or from ________ transport across _____________ gill membrane 26  Tonicity And The Environment – Water Dwellers Elasmobranchs - __________ isoosmotic to seawater, but concentrations of Na+, K+, Cl- all less than seawater – difference made up by ____ crea Still must deal with inward diffusion of Na+, K+, Cl- through gills __________ Rectal gland secretes a highly concentrated salt solution ↳ internal 27 Tonicity And The Environment – Land Dwellers A dry environment - constant water loss through evaporation _________: Across wet respiratory membrane ↳needsIsweet Across surface of skin Water loss in urine and faeces Requires: ___________ waterproofing of outer layer of body ______________of Minimal exposure gas- exchange and digestive surfaces to air tortoise ↳ Minimizing _______________ electrolyte in take not eating salty foods We will deal with this in more depth when we examine adaptations to life on land 28  Summary of responses to the osmotic environment Terrestrial environments are dry: _________to Lose water the environment Consume/produce/conserve water Limit salt intake Marine environments are hyperosmotic (dry): ________to lose water and _______from gain salt the environment Eliminate salt and consume/produce/conserve water Limit salt intake Freshwater environments are hypoosmotic: _______from Gain water and __________ lose salt to the environment Eliminate water and consume/conserve salt Limit water intake 29  Osmoregulation in ANIMALS Active _________ regulation of water loss and gain __________: Excretion elimination of waste/toxins Aids in controlling content of ______________ extracellular fluid (salt/water/pH) Major means: _________ Diffusion into water (only in aquatic habitats) Actions of _______________ excretory tubule (liquid waste): __________ Filtration (non-selective) ___________ Secretion (selective) -moves ions using energy ____________ Reabsorption (selective) ions to the "filtrate - are pumped back in 30 Osmoregulation in ANIMALS Ion Ion pump X exchanger solutes Z X (against conc. gradient ( ADP filtrate against conc. gradient ATP x z x Z ECF x (against conc. gradient( filtrate z X water Co- transporter Excretory tubule composed of _________________– transport epithelium allows ______________of active transport ions between ECF and filtrate Other solutes and water diffuse in either direction 31 Filtration, reabsorption, secretion result in production of urine/filtrate Water permeable Water impermeable membrane membrane Filtration Secretion Concentrated (isosmotic) Resorption (hyperosmotic) urine Different ECF/plasma unwanted Ions Ions Water functions of Sugars (hyperosmotic) excretory tubule localized along its length 32  Ammonia (NH3) excretion ________ Ammonia is Toxic, we must get rid of it Aquatic ________ Diffusion into the environment (across body / gills) ________ Excretion in filtrate/urine Ammonium (NH+4) / sodium exchangers Na+ water NH3 + H+ NH4+ plasma Terrestrial (and some aquatic) Terrestrial cannot use diffusion or ion exchange with air only ________ excretion in filtrate in the 0 a soware Produce ____ Ured (mammals, amphibians, sharks) semisolid ; snot soluble in H20 Produce ________(land Uric acid snails, insects, reptiles/birds) Key for animals that develop in terrestrial eggs 33 Ammonia (NH3) excretion 34 Protonephridium Filters extracellular fluid, eliminates waste by means of current produced by ciliated flame cell Drains into series of ducts Reabsorption takes place in the ducts 35  Metanephridium Filters coelomic fluid, __________ resorption into circulatory system through blood vessels Associated with closed __________________ circulatory system 36 Malpighian Tubules Large absorptive surface area in contact with ____________ haemolymph Active secretion of uric acid, ions into lumen of tubule Water follows through osmosis Filtrate released into gut Na+ and K+ actively transported out, water follows Solid uric acid released with faeces 37 Nephron Found in __________ vertebrates Filters water and solutes from blood, reabsorbs water and solutes to produce concentrated urine _____________ Loop of Henle – important in formation of concentrated urine 38  HOMEOSTASIS and CIRCULATION Why circulate fluids? _____________ Processing Regulate pH, osmolarity, waste, add nutrients, gas exchange _______________________________ Transportation / communication hormones, heat, gasses, nutrients, immune components, solutes __________ Diffusion is adequate in small (>1 mm thick) simple organisms, larger require a circulatory system Plants vs Animals both use a series of tubes, but differ in: Nutrient, energy and water sources Metabolic rates Cell structure Presence or absence of muscle 39 Types of Circulation in Animals 40  CIRCULATION in Animals Animals: Heterotrophs with extracellular digestion High metabolic rates demand rapid circulation Tissues require _______ oxygen and ___________ nutrients ______________must Respiratory wastes be carried away Move – vessels of system must be _______ flexible 41  CIRCULATION in Animals ____________ Muscular pump and ______ flexible ______ tubes (vasculature) for circulation Fluids must be _____________ forced through the vessels a cardiovascular system Pump (cardio) and vessels 42  CIRCULATION in Animals __________________: open circulatory system _________, ____ Low-pressure slow – suitable for taxa with slow metabolic rates May be supplemented with faster specialized transport systems, ie. tracheae in insects _________ Hemolymph – transport fluid in open circulatory systems, comes into ________________________ direct contact with the tissues - extracellular fluid pool 43  CIRCULATION in Animals Open circulatory system: Heart(s) sit in haemolymph-filled _________ naemocoel On contraction, haemolymph expelled from heart via major arteries to other haemolymph- filled spaces On relaxation, haemolymph enters heart from haemocoel Valves in heart wall maintain unidirectional flow Further distributed by body movements – directed flow to active tissues not possible Accessory hearts may supply limbs 44  CIRCULATION in Animals _______________________: closed circulatory system Blood under __________ pressure continuous closed circuit Blood vessels and heart form ___________________ Found in forms able to sustain prolonged high activity rates – annelids, cephalopods, some crustaceans, all vertebrates 45  CIRCULATION in Animals Closed circulatory system: Blood contained within heart and vessels of circulatory system, not coming in direct contact with any of the tissues of the body extracellular fluid pool Blood plasma is part of the _____________________________ Capillary beds connect veins and arteries, permeating tissues Confinement makes _______________, pressure regulation ___________and direction flow of _____________ high flow rates possible 46  The Heart Muscular pump – creates ________ pressure and directional flow in vasculature in closed circulatory systems, creates directional flow in open circulatory systems - bloodflows in one direction through the > - out Ein -in out & - lots of force from muscles to move blood 47  The Heart and Blood Vessels In closed circulatory systems, heart maintains bulk flow of fluids in the face of ___________ resistance do not Ohm’s law: flow____ = ________ Pressure / _________ Resistance C 3 Low pressure need to calculate High pressure Resistance in blood vessels (function of vessel length, diameter, smoothness) · smaller vessels = & resistance resistance · smooth vessels ↓ friction , : vessels = ↑ resistance/force · longer 48  leaving [T The Heart and Comingt If Blood Vessels In a closed circulatory system: From heart to capillaries: (capillaries ( Blood pressure ____ drops with - spread out , slowsdowquality blood exchange distance from heart, due to greater total volume occupied, ___________ resistance ↑ Blood velocity decreases ________ with distance from heart, due to T > - smaller diameters of vessels occupied, due to resistance, & decreasing diameters of vessels T From capillaries to heart: 3 volume increasing Blood pressure continues to ____ drop Blood velocity _________ increases due to increasing diameters of fewer vessels 49  Blood Vessels and Blood Blood Vessels (in closed system): exit the of _______ Arteries (efferent vessels) carry fluid away from heart control blood distribution to the body by controlling vessel diameter (resistance!) depulsate pressure waves from the beating heart (elastic – expand/contract) - to _____ Veins (afferent vessels) carry fluid back to heart store blood (easily expand) 50 Blood Vessels and Blood Capillaries Exchange of substances between blood and tissues (gas, fluids, solutes, nutrients, waste) Morphology of wall permits _________ diffusion Huge cumulative _______ surface _______ area 51  Blood Vessels and Blood Blood (ECF) in vertebrates: ① _______ Plasma (ECF - water, ions, proteins, nutrients, gas) Key ions are Na+, K+, Cl-, HCO3-, Ca++, H+ Key proteins are globulins, albumin, fibrinogens Key gasses are O2 and CO2 3 custnoa dea ② ___________ Erythrocytes (contain respiratory pigments – haemoglobin, haemocyanin, etc.) RBCs ↳ turns blood red Increase capacity of fluid to carry O2 and CO2 ⑤ _________ Leukocytes (white blood cells) – immune system ⑱ _________ Platelets 52 Blood Vessels and Blood 53  Vertebrate Circulatory Systems Variation in circulatory system in vertebrates associated with: Whether or not _______ gravity is a factor affecting blood flow (requiring higher pressure) Where ___gas __________ exchange takes place (gills, lungs, or lungs and skin) ____________ Thermoregulatory ________(endothermy mode or ectothermy) 54  Vertebrate Circulatory Systems Basal condition in vertebrates (“fish”) – 2 chambers: _____ Atrium – thin-walled, receives o2-poor blood from systemic circulation _______ – thick-walled, Ventricle muscular, sends o2-poor blood through aorta to gills Circulatory system forms ___________ single loop Low-pressure – effects of gravity negligible 55  Vertebrate Circulatory Systems Tetrapods evolved two separate circuits: Low-pressure ___________ pulmonary circuit between heart and lungs High-pressure ____________ between heart and rest of the body Each of these circuits required its own atrium, and increasing separation of the _________ ventricles into two chambers ________ Gravity becomes a factor 56 Vertebrate Circulatory Systems Many ectothermic tetrapods can bypass pulmonary circuit While ______ diving Cutaneous respiration Ectotherms tolerate some mixture of deoxygenated blood and oxygenated blood due to low ____________– metabolic rate thus incomplete separation of ventricle 57  Vertebrate Circulatory Systems Mammals and birds have _________________ complete separation between ventricles Blood can only pass blood between pulmonary and systemic circuits at the ______ heart ___________ Endother my requires efficient delivery of O2 to tissues mixing allowed - no 58  HOMEOSTASIS and GAS EXCHANGE Why is it needed? Krebs cycle and Oxidative phosphorylation Consume oxygen and produce carbon dioxide Photosynthesis Consumes carbon dioxide and produces oxygen pH regulation (via CO2 regulation, forms carbonic acid) All Plants and Animals must breathe! 59  O2 consumption and CO2 production Acetyl-CoA CO2 + NADH 60 RegisFrey/CC BY-SA 3.0 Gas Exchange with the environment Ventilation (breathing): ___________ ________between Bulk flow the respiratory medium (air/water) and the gas exchange surface (body surface/lungs/gills/etc.) Must move large quantities of air/water over respiratory membrane Gas enters/exits extracellular fluid bulk flow system by _______ diffusion ↳ in lungs , diffusion is used to move CO23 Of across membrane arachnids & expo at - pocketsoftissue Book lung By John Henry Comstock - Scanned from the 1920 edition of The Spider Book, published by Doubleday, Page & Company in the United States (originally published in 1912), Wikimedia Public Domain, https://commons.wikimedia.org/w/index.php?curid=8754431 61 Gas Exchange and Gas Transport ____________ bas exchange takes place between blood and air or water (at the respiratory membrane) and between tissues and blood - __________ diffusion in both exchanges _____________is Gas transport carried out by the blood (circulatory system) 62  Atmospheric Composition and Pressure Atmospheric pressure Jar as you decreases with ______ altitude The _________ composition of the % [ atmosphere remains the same Each gas making up the atmosphere contributes towards total atmospheric pressure - has a _______ partial ________ pressure ,P +P2 = Ptotal 63  Partial Pressure Gradients in the Body Diffusion in gas exchange is based on _______ partial ________ pressure _________ gradients gradients = concentration Oxygen and carbon dioxide partial pressures differ ____ throughout the body Atmospheric oxygen = 21% Atmospheric carbon dioxide = 0.03% CO2 produced in tissues (high partial pressure) O2 consumed in tissues (low partial pressure) Gradients maintained by __________ circulatory _________ system - different partial pressure drive diffusion of gas high low CARBON OXYGEN DIOXIDE partial Partial pressure pressure low high 64 Biology, Nelson 2013  Gas Exchange with the ECF Gas Exchange Surface: ________ Diffusion between air/water and the ECF Surface area of gas exchange surface is proportional to mass and metabolic rate - highly folded Surface area / volume relationships are important etc lungs - large animals need specialized gas exchange structures , ↓ - lungs, gills, book lungs/gills, trachea (not just body surface) Characteristics of a good gas exchange structure: reflected in Fick’s Law of Diffusion (Rate = D A dC/dX) Large ____________ surface are a Moist esp if terrestrial - ↳dry in gasthe will bounce off Thin , 65  Gas Exchange with the ECF and Tissues ECF / cell interface: Diffusion at capillaries Small diameter (blood is never far from the walls), high total surface area, thin walls Single large blood vessel Multiple small blood vessels blood closer to - volume that isn't readily surface available to surface for - diffusion 66  Gas Exchange with the ECF Short distance across membrane to ECF necessary 67  Gas exchange surface area is Gas exchange surface proportional to body mass Animals with high metabolic rate (e.g. bird, mammal) endotherm Area of Animals with low metabolic rate (e.g. fish, amphibians) ectotheme but same scaling Body mass (size cubed) 68  Gas Exchange with the ECF Circulation: ____ ____of ECF within Bulk flow the animal Circulatory system must interact effectively with the gas exchange surface Mammals – ______ uniform _____ pool Gas partial pressure gradient maintained by movement of blood Relatively poor gas exchange 69 Gas Exchange with the ECF fish Countercurrent exchange Water and blood move in opposing directions Maintains ________ constant _____ partial _______ pressure ________ gradient along exchange surface Highly effective gas exchange Buffin 2019, Phys. Chem. Chem. Phys., 21, 2186-2195 70 Gas Exchange with the ECF water - & blood 71  Gas Exchange with the ECF ____________ crosscurrent ________ exchange in birds Air flows in ___ one __________ direction through the rigid lungs Air sac system Two cycles of ventilation necessary for one breathe to clear system Much more effective gas exchange than in uniform pool exchange 72 Gas Exchange with the ECF - I breaths to clear old gas One-way bulk flow of air through a bird’s respiratoryexpand - system bird lougs don't or contract - two sacs that do 73  HOMEOSTASIS and ACID-BASE (pH) REGULATION pH is a measure of [H+] = -log10[H+] [H+] is moles H+/litre Log10 scale – [H+] changes by 10X with each successive integer on the scale H+ is continuously produced in aerobic respiration (among other metabolic activities) 74  HOMEOSTASIS and ACID-BASE (pH) REGULATION pH affects proteins involved in most cellular biochemical pathways H+ interact with charged regions, changes protein shape Tight regulation (human ECF pH = 7.4 (6.8-7.7)) 150 nM – 20 nM - small quantities Regulation involves production, retention, and removal of _____ H + - mainly through _______ bicarbonate _____________ buffering mechanism CO2 + H2O H2CO3 HCO -3 + H+ Carbonic acid Sensors monitor ECF Feedback system 75  HOMEOSTASIS and ACID-BASE (pH) REGULATION 76  HOMEOSTASIS and ACID-BASE (pH) REGULATION Bicarbonate (pulmonary) buffering system: CO2 reacts with H2O to form carbonic acid - H2CO3 In vertebrates, carbonic anhydrase in red blood cells reversibly facilitates this reaction In plasma, H2CO3 readily dissociates into HCO3- (bicarbonate) and H+ - easily reversible reaction 77  Acid-Base Regulation CO2 + H2O H2CO3 HCO -3 + H+ either can go way ventilation(and thus plasma CO ) - Regulation of _________ 2 very important route of pH control in terrestrial animals breathe into Hyperventilation – gets rid of CO2 faster than it’s Coaper ______________ bag to get 12 back produced, shift reaction to left, lowers [H+] – alkylosis ____________ Hypoventilation – conserves CO2, shifts equation to right, increases [H+] – acidosis 78  Acid-Base Regulation CO2 + H2O H2CO3 HCO -3 + H+ Renal and chemical buffering systems: Excretion/diffusion of HCO -3 or H+ through _________ excretory ______or tubules across gills, skin Proton or bicarbonate pumps – eliminate bicarbonate, shifts reaction to right, [H+] goes up – reverse pump – shifts reaction to left Chloride for bicarbonate pump major way - to regulate pH Sodium for H+ pump, sodium for ammonium pump is through bicarborate Binding of protons to other _________ molecules 79  Y Recap of Theme 3 G I (animals) Why is homeostasis important? Roles of osmoregulation, circulation, gas exchange, pH OSMOREGULATION Bulk flow, diffusion and osmosis/water pot. Osmosis and animal vs plant cells. environment to different have a came environment) as # against work Osmoconformers and osmoregulators. Internal Water balance in terrestrial, marine and fresh-water environments. Excretory organs, osmoregulation and metabolic waste (ammonia excretion). 80  4 Recap of Theme 3 ↳ I (animals) CIRCULATION Moving the fluid (ECF) environment around the body around Plants vs Animals L bUIK Pow (not passing all cell) to Demands for animal circulation Hearts, blood vessels, blood Open and closed circulatory systems GAS EXCHANGE Why do plants and animals need to? Characteristics of a good gas exchange structure. Movements of gasses between cells and atmosphere: diffusion/partial pressures, and bulk flow 81  Recap of Theme 3 I (animals) pH REGULATION Importance of controlling [H+] Role and regulation of CO2, HCO3- (bicarbonate buffer), excretion and proton buffers. 82  Theme 5: Animal Reproduction and Development In animal reproduction, new individuals are produced by _______ existing __________ individuals Generally involves dominant _______ diploid stage producing ______ haploid gametes, which fuse to produce new ___________ diploid zygote But not always Zygote must undergo ______ and ___________ Cells that give rise to gametes isolated early in development 1  Asexual Reproduction Asexual Reproduction – genes from one parent _______ Fission – genetically-controlled, two identical individuals result _______ Budding – smaller offspring arises from parent ____________ Fragmentation– each fragment gives rise to a new organism _____________ Parthenogenesis – new individual develops from unfertilized egg Based upon mitosis Pros Cons Don’t need males Lack of genetic Rapid reproduction variability Saves energy 2 Asexual Reproduction bodings par 3 Asexual Reproduction Fission - planarian 4 Asexual Reproduction  Sexual Reproduction Sexual Reproduction – genes from two parents Eggs (oogenesis) and sperm (spermatogenesis) - the _______ gametes - produced by _________ meiosis Always involves fertilization and development female male or - ________ (gonochoristic) Dioecious – two separate sexes and -male _______________________ Monoecious/hermaphrodite (simultaneous vs sequential female hermaphrodites) ) – an individual has male and female reproductive organs (simultaneously or at different life stages) Pros Cons Generates genetic Fertilization necessary - variation complicated Development must proceed from zygote start from single - a cell Costs of eggs and sperm Males don’t produce offspring 6  Gametes Cells that give rise to gametes (germ cells) ____________________from developmentally isolated somatic cells Development and differentiation of somatic cells do not affect germ cells – experiences of organism do not affect ________ genome of sex cells 7  Gametogenesis Takes place in primary reproductive organ or ______ gonad Consists of mitosis, meiosis, and cell differentiation to produce gametes – haploid sex cells which must combine to give rise to zygote – new diploid individual Gametes are the only haploid stage of an animal’s life cycle (as a rule)  Sperm Produced by spermatogenesis Sperm cells are highly __________________ modified and simplified Mitochondria provide ATP for flagellum Head consists of acrosome, nucleus, centrioles Few or no stored nutrients Male strategy is to produce abundant small, motile, cheap gametes Note opisthokont characteristic  Oogenesis Produced by oogenesis Egg contains large amount of _________, cytoplasm ________, organelles ______ stored ________ nutrients (yolk) Contained within vitelline membrane (zona pellucida) – carries receptors for sperm May be wrapped within jelly layer, hard shell Female strategy is to produce few large, non- motile, well-provisioned gametes Reciprocal of male strategy Reproductive Systems Males ______ testes produce sperm ___________Carry Sperm ducts sperm to genital opening Females ______ ovaries Produce eggs _______ oviducts Carry them to genital opening External reproductive structures depend upon whether fertilization is external or internal  Hermaphroditism Adult organism possesses functional reproductive systems of ________, both sexes either simultaneously or sequentially Common in some taxa (annelids, gastropods) 12  Fertilization and Early Development Bringing sperm and egg together The one, right sperm, for the egg Protection of the developing embryo Events in early development Cleavage, blastula, gastrula (tissue layers) ____________ Pattern formation – basic body plan ______________ Organogenesis – formation of organ rudiments 13  Fertilization 1 bringing sperm and egg together Dominant life cycle stage diploid (usually) Fertilization: External fertilization (e.g. broadcast spawning) Internal fertilization Aquatic and terrestrial environments 14  External Fertilization Only in aquatic animals Gametes generally _____ small (egg still larger)than sperm Frequently high egg mortality Number of eggs released varies greatly among species usually lot - a Coordinated gamete release may be due to stimulus through courtship movements, calls, or pheromone release, or in response to seasonal environmental cues 15 Internal Fertilization Found universally in terrestrial and in some aquatic animals Large differences in gamete size Number of eggs relatively _____ small ________ copulation- generally requires copulatory organ ___________ spermatophore - alternate to copulation – package of sperm and mucus introduced into female’s reproductive tract 16  Internal Fertilization Internal fertilization allows different ways of protecting the developing embryo 17  Fertilization 2 One Sperm And The Right Sperm For The Egg Challenges for fertilization – making sure that the right sperm encounters the egg, and that ________________fertilizes only one sperm it The wrong sperm: interspecific External fertilization – possibility of _____________ sperm-egg encounters Internal fertilization - possibility of mating with an individual of the wrong species ___________ reproductive _______ ___________ are required isolating mechanisms 18  Fertilization 2 Preventing Polyspermy _______________(____ Acrosomal Reaction fast _____) block – sperm cell membrane fuses with egg cell membrane, initiates wave of depolarization – subsequent sperm can’t fuse with egg ___________ Cortical Reaction(____ slow _____) block – cortical granules fuse with egg membrane, vitelline coat becomes impenetrable to sperm – external and internal fertilization 19  Fertilization 2 Preventing Polyspermy 20 Reproductive Isolating Mechanisms There are a variety of isolating mechanisms that prevent species from interbreeding and producing hybrids ________________ Prezygotic barriers – eggs and sperm never encounter one another, or if they do, fertilization does not take ↳ stop gene flow place - steule already waste Postzygotic barriers – gametes _________________ fertilization can take place, but hybrids unlikely to reproduce in turn 21  Protection of the embryo - Aquatic Eggs Protected by jelly layer __________ 22 The Amniota shared derived _______________ __________ character – the amniotic egg 23  Protection of the embryo - Amniotes _____________: Amniotic egg Variations found in all ________ amniote vertebrates ________________ Extraembryonic ______ membranes carry out life-support functions for embryo Shell protects internal environment Requires internal fertilization 24  Viviparity Exchange of _______, gasses __________________ nutrients and wastes exchangee ~ between mother and developing embryo Requires development of some form of _______ placenta for exchange – in vertebrates, derived from extraembryonic membranes  Ovoviviparity Retention of the __________ fertilized egg within the mother’s body, with varying degrees of exchange of gasses, nutrients or wastes between mother and developing embryo Frequently seen as intermediate step between oviparity and viviparity – actually a continuum 26  Early Development (ontogeny) Cleavage – gastrulation – morphogenesis – organogenesis – growth mitosis, gene activation/expression, differentiation zygote must give rise to a complex multicellular body 27 Ovum Structure vegetal pole-zone ____________ primarily yolk – nutrient rapid supply slow cle