Theme 3 (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 Sensory modes Thermal properties Water – always a limiting resource Sunlight – exposure to UV 4  Life on Land Some requirements for a terrestrial life include: Desiccation avoidance Mechanisms: reduce water loss replace lost water 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 ____________: Across wet respiratory membrane Across surface of skin Water loss in _____ and ______ Some species lose water through _____________________ (sweating, panting) 7  Desiccation And The Environment – Terrestrial Animals Requires: _____________ Of outer layer of body Keratin Wax Minimal exposure of gas-exchange and digestive surfaces to ___ Internal placement 8  Nitrogenous Wastes Toxic _________ (NH3) produced in every cell of the body by catabolism of amino acids and nucleic acids Reptiles, birds and insects convert ammonia to _______ – very low water-solubility, semi- solid nitrogenous wastes can be excreted while ______________ 9  Desiccation And The Environment – Terrestrial Animals Mammals are _______ – convert ammonia to less-toxic ____, but must lose water in excretion ______________ aids in conservation of water in mammals Produces concentrated urine – ___________ to blood The longer the loop, the better for water conservation 10 Desiccation And The Environment – Terrestrial Animals Kangaroo rats: Desert-adapted rodents Very long ______ _____ Produces small quantity of highly ___________ 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 Must deal with small size (___________________ favours desiccation by evaporative water loss from body surface) and inevitable evaporative loss from wet respiratory surfaces in _______ Waxy outer layer of ______ minimizes evaporative water loss from body surface Spiracles permit closing of _____________, cuts down on evaporative water loss 12  Desiccation Tolerance Terrestrial tardigrades live in water films in damp environments _____________ – formation of resistant stage (tun) in response to environmental challenges (dehydration, sub-zero temperatures) ____________ – 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 ________ __________ 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 CO2 does not _______ into air as easily as into water Inevitable ___________________from 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 Low _________ Low _________ 17 Gas Exchange With Air - Trachea 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 ____ ____ system for air Biology, Nelson 2013 20 Gas Exchange With Air Vertebrate lungs – ___ __________ to respiratory membrane Moist exchange surfaces internal Requires muscular effort (__________) 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 ___________ 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 __________ provides an aqueous environment for the developing embryo Requires ________ _________ Requires ________ ______________ ____________ 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 ______ their body temperature when possible Through _________________ Through __________ 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 __________________: 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 _________________ Animals regulate body temperatures within range allowing ________________ 28  Ways Of Thermoregulation _________ – the production of sufficient metabolic heat to warm the tissues significantly __________ – 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 __________ – tightly regulating body temperature around an unvarying mean These define two axes across which thermoregulatory strategies form a continuum 30 Ways Of Thermoregulation _________ – metabolic rate changes with temperature in order to maintain a constant body temperature – an energetic cost _________ – metabolic rate changes directly with body temperature, which changes with environmental temperature – a potential ________ (loss of performance) 31  Heat Exchange With The Environment ________ – direct heat transfer by contact – air conducts heat poorly, water well, so gill-breathing aquatic organisms tend to be _________ with the water in which they swim _______ – 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 _________ – transfer of heat by a moving medium – air or water flowing over an organism carries heat away or delivers it _________ – energy consumed by change from liquid to gas; effective way to carry heat away 33 Heat Exchange With The Environment _________ animals can thermoregulate by using these modes for ____ ______ with the environment Basking lizard regulates body temperature largely through exposure to radiation, convection, conduction Metabolically _____ 34 Countercurrent Heat Exchange Cold-climate terrestrial endotherms can conserve heat by using _____ __________ ________ ________ – warm blood in efferent vessels heats cool blood in afferent vessels Regional heterothermy 35  Torpor And Hibernation Torpor reduces energy demands in small endotherms during periods of low or high environmental temperatures, or resource unavailability _____________________________ drops ______________ depressed 36  Torpor And Hibernation _________ is a seasonal version of ______, undertaken during seasonal periods of low temperature 37  Endothermy In Insects Bees and some other flying insects are _____________ _________ – 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 ______________ - some ectotherms can _______ their ECF – goes below 0° C without freezing (mainly marine) ______________ - some terrestrial ectotherms can allow the bulk of their ECF to freeze for extended periods High intracellular osmolality depresses freezing point Control of ice nucleation in ECF 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 ________ _____more effectively than water Water conveys _________ _______more effectively than air The ______ __ _____is far greater in water than in air Being able to sense _____ ___ __ ____ is very important in terrestrial environments 41  Chemosensors Chemosensory organs – require ___ _____ for adsorption of air-borne chemical particles Insect antennae have minute channels lined with moist adsorptive tissue 42 Chemosensors Terrestrial vertebrates have moist _______________ and taste buds in oral cavity 43 Hearing Sound does not transmit easily from air to water (___) Sensing soundwaves by terrestrial animals must take this into account Insects – ________ ______ – air on both sides, nerves (mechanoreceptors) pick up vibrations 44 Hearing and Balance Vertebrates: Organs for _______, and for sensing __________ and which direction is ____ (vestibular 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 ____________ 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 bigger 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 49  Allometry _______________________ is characteristic of most animals Different parts of the body grow at _________ _____ with increase in overall ____ It is also an evolutionary phenomenon associated with trends in increasing or decreasing body size in a lineage 50 Support Body Weight The ant is exhibiting ________ growth in the real world, the limbs of the larger specimen would not be of sufficient thickness for efficient locomotion Limbs must grow ___________to support increasing body weight with increasing size 51  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 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: _________ (external) and ________________ (internal) Functions: Provide attachments and leverage for ______ – force transmission Transmit _______________ to substrate Provide framework for tissues of body Act as ____________ for physiological requirements (vertebrates) Protection for delicate organs or whole body 56  Endoskeletons In vertebrates, composed of bone and cartilage ____ – collagenous matrix mineralized by CaPO4 crystals 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 ____ – complex polysaccharide May be impregnated with calcium carbonate Composed of plates (______) 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: Volume of fluid enclosed by ________________ Longitudinal and circular Fluid _______________ but pressurized when muscle contracts Muscular “container” changes shape with contraction of different muscle layers Organ Animal’s whole body 60  AQUATIC Animals Water supports the body Affects size, stance and skeleton Desiccation is a lesser threat Stable and mild temperatures Metabolic waste removed by water Sound transmits well from water to body 61  Challenges of living in aquatic environments: Water is _____ Takes energy to displace Water is _________ A layer clings to the body Water has __________ content (~1 – 2%) compared to air (~21%) Oxygen levels in water vary greatly with other parameters Water has high ________ ____________ 25x that of air 62 Endoskeletons - terrestrial Firmly attached girdles Enclosed ribcages Endoskeletons - aquatic Ribcages not enclosed Loosely attached girdles 63 Wikimedia commons public domain Aquatic animals can become much bigger than terrestrial animals The biggest aquatic animals are _____________ 64  Salt and Water Balance Excess salt in the diet is a problem for marine tetrapods Marine birds and reptiles excrete excess salt through ____ ______ associated with upper respiratory tract or eyes Marine mammals can produce highly _____________ _______ 65  Being warm in aquatic environments Water is a good heat conductor – aquatic organisms are mostly ____________ __________ Aquatic homeothermic endotherms must ________ with blubber or a waterproof pelage 66  Being warm in aquatic environments __________ – fur, feathers, fat Respiratory medium – breathe ___ – allows higher metabolic rate; also, air is poor conductor of heat from body Aquatic endotherms utilize ____________________ – 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