Module 2 Bio 121 PDF

What is life ? How to distinguish life from non-living entities ? Non-living components of the environment (water, fire, wind, gases, pH, salts, etc.) living organisms influence (e.g. survival) = _____________ factors What do they have in common ? 7 characteristics of life Representative Organisms [...

What is life ? How to distinguish life from non-living entities ? Non-living components of the environment (water, fire, wind, gases, pH, salts, etc.) living organisms influence (e.g. survival) = _____________ factors What do they have in common ? 7 characteristics of life Representative Organisms [RO’s Image source; U of S 7 Characteristics of life 1. Living organisms consists of one or more cells Cells : I. are the basic structural & functional (physiological) units of all living organisms II. contain DNA (hereditary material), cell membranes and ribosomes protein-producing factories of cells barrier between the living cell and the outside environment Heredity information of all living things is coded in only two chemically related substances: DNA and RNA. A T ----> genetic code is simple but it is universal G Only four genetic letters in DNA AT G C C Uracil (U) replaces thymine (T) in RNA DNA - the means to store genetic information The entire evolutionary development of the living world has taken place not by invention of new "letters" in the genetic "alphabet" but by elaboration of ever-new combinations of these letters. Image from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings The cell(s) of all living things contain DNA (hereditary material) = blueprint of life ------> ________ OF LIFE (share a common ancestor) ___________ OF LIFE Phylogenetic (evolutionary) relationships of organisms first life DNA – relatively stable inside individual cells – however, sequence of DNA molecule can change by mistakes in DNA replication/effects of environmental agents mutations ---------> biological evolution Life adapts through evolution Image from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings Life adapts through evolution the physical, chemical & behavioural characteristics of life change populations (of living organisms) change over the course of many generations evolution results in traits that promote survival & reproductive success evolution is possible only because of the numerous variations that exist within each species e.g. Dalmatian Wall Lizard: several colour morphs in males ** morphs of a single species = polymorphs (polymorphism) Cells (continued) : III. are only produced from the division of pre-existing cells IV. have basically the same chemical composition ______________unity of cells 80-90% of the body mass of plants & 50-60% of the body mass of mammals are composed of water Four elements comprise the bodies of these organisms: water major building block of all living matter vital element in all proteins % of mass % atoms Oxygen (O) 65.0% 24.0% Hydrogen (H) 9.5% 62.0% Carbon (C) 18.5% 12.0% Nitrogen (N) 3.2% 1.1% Human body other vital elements (< 2% of body mass): key regulators of water movement & electrical currents that occur across the surfaces of many cells calcium (Ca) phosphorus (P) chlorine (Cl) sodium (Na) potassium (K) magnesium (Mg) sulfur (S) components of skeletons & shells of animals All living organisms require trace elements (< 0.01 % of body mass) Examples: chromium (Cr) iodine (I) cobalt (Co) iron (Fe) copper (Cu) flourine (F) manganese (Mn) selenium (Se) Aluminium (Al) Bears : possible co-factor for chemical reactions Plants : toxic Chemical uniqueness of life Living organisms have many types of highly specialized [large] macromolecules (“__________________”), that include: i) Carbohydrates ii) Lipids iii) Proteins not normally found in inanimate matter iv) Nucleic Acids - cells are both distinct entities & building blocks of more complex organisms _____________________ of life (= levels of biological organization) 1. Atoms & Elements 2. Molecules & macromolecules 5. Organ & 6. Organ systems 3. Cells 4. Tissues 7. Organism 12. Biosphere 11. Ecosystem 8. Species 9. Populations 10. Community Image from Biology 7th Edition, by Campbell and Reece. 2005. PearsonBenjamin Cummings ___________________ = a localized group of individuals of the same species that can interbreed and produce fertile offspring ____________________ = all organisms (an assemblage of populations of different species) that live in a particular area ________________________ = all organisms in a specific area as well as the abiotic factors (e.g. water, soil etc): ≥ 1 community + physical environment ________________= the sum of all ecosystems Characteristics of life All forms of life can be divided based on their cellular structure : a) unicellular vs multicellular 1. Living organisms consist of ______________ cells unicellular organism (all functions performed) Images from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings multicellular organism (some cells have specialized functions) 25 representative organisms Unicellular Image source; U of S algae yoghurt bacterium Dead Sea bacterium green alga amoeba paramecium Multicellular Image source; U of S unicellular multicellular Common filamentous alga green algae https://en.wikipedia.org/wiki/Spirogyra colonial brown algae https://en.wikipedia.org/wiki/Volvox Image source; U of S Unicellular Size of unicellular organisms ? How big can they get? green algae (protist) bacteria Unicellular Unicellular organisms organisms are are small small Most Most bacteria bacteria are are 0.2 0.2µm µm in in diameter diameter and and 2-8 µm in length length Image: Principles of Biology (ISBN: 978-1-942310-72-3) Nature Publishing Protists Protistslarger larger than than bacteria bacteria 0.8 - 100’s µm (a few (a as fewlarge as large as 2,000 as 2,000 µm [=2mm]) µm [=2mm]) Why are unicellular organisms small in size ? - size of organism is limited (in part) because cell’s are subject to the surface area to voulme ratio diffusion Image source; unknown e.g., Bacteria: Staphylococcus aureus Image: Principles of Biology (ISBN: 978-1-942310-72-3) Nature Publishing Image source; unknown Ratio of Surface Area to Volume in cells r = 1 μm r = 2 μm r = 3 μm r = 1 µm r = 2 µm r = 3 µm Surface area (4πr2) = 12.6 µm2 Surface area = 50.3 µm2 Surface area = 113.1 µm2 Volume (4/3πr3) = 4.2 µm3 Volume = 33.5 µm3 Volume = 113.1 µm3 Surface Volume = 3 Surface = 1.5 Volume Surface = 1.0 Volume As cells increase in size, there is a point where the plasma membrane/cell wall can not pass enough material across it to meet the needs of the increased cytoplasmic volume __________________ modification of shape same volume but greater surface area Multicellular Image source; unknown Not all single-celled organisms are circular in shape Bacteria cell elongation Image source: unknown Protists cell elongation, extensions of the cytoplasm ---------> limit to cell size (most unicellular organisms are ___________) Image: Principles of Biology (ISBN: 978-1-942310-72-3) Nature Publishing Most bacteria are 0.2 µm in diameter and 2-8 µm in length Exception: Sulphur proteo-bacterium Thiomargariata namibiensis 750 µm in diameter Protists larger than bacteria: 0.8 - 100’s µm (some 2mm) e.g., Micrasterias green alga (protist) ≈ 100 x 160 µm Exception: “bubble algae” Valonia ventricosa - diameter 1-4 cm occurs in tropical/subtropical oceans Exception: green alga Caulerpa taxifolia (“killer” alga: seaweed) 65 cm (fronds) Some spp.: several feet Image: http://www.wetwebmedia.com/ca/volume_6/ volume_6_4/caulerpa.html Wikiipedia Valonia ventricosa ("bubble algae”) Diameter: 1-4 cm (0.4 to 1.6 in) nucleus Oceans - Tropical / subtropical chloroplasts & vacuoles cytoplasmic compartments (membrane) = single celled organism with multiple nuclei cell wall cytoplasm single celled organisms with multiple nuclei Giardia intestinalis two nuceli Paramecium caudatum macronucleus macronucleus several macronuclei All forms of life can be divided based on their cellular structure : b) prokaryote vs eukaryote Prokaryotes GK: pro = “before” and karyon = “kernel” or nucleus ----> lack a membrane-enclosed _______________ e.g., bacteria DNA organized in a single chromosome. No mitosis Eukaryotes DNA organized in multiple chromosomes inside nucleus. Mitotic division. GK: Eu = “true” or “real” ----> true nucleus ----> with a membrane-enclosed nucleus Images: Principles of Biology (ISBN: 978-1-942310-72-3) Nature Publishing membrane-bound organelles (nucleus, mitochondria, etc) e.g., protist Prokaryotes 25 Representative organisms Image source; U of S yoghurt bacterium: blue-green algae: Dead Sea bacterium: Eukaryotes Eukaryotes Prokaryotes Bifidobacterium Anabaena Spirogyra Micrasterias Multicellular Unicellular Image source; U of S ∴ life is highly organized Maintaining a highly ordered state is costly ∴ ------> _______________ Characteristics of life 2. Life requires a constant input of energy and raw materials a) Autotrophs _____________ their own food (“self-feeders”) - use an external energy source to produce organic matter from ______________ raw materials b) Heterotrophs = require ________________________ molecules - use energy in _________________matter obtained (eaten) from other organisms i) Photoautotrophs: use light from sun (energy) and inorganic materials (H2O and CO2) photosynthesis 6CO2 + 6H2O Carbon dioxide Light Water C6H12O6 + 6O2 Sugar Oxygen ii) Chemoautotrophs: use inorganic compounds (H gas; S, NH3, nitrites, Fe) as energy sources chemosynthesis 6CO2 + 12H2S Carbon dioxide C6H12O6 + 6H2O + 12S Hydrogen sulphide Sugars 6CO2 + 6H2O + 6H2S + 6O2 Carbon dioxide Water Hydrogen sulphide Oxygen Water Sulphur C6H12O6 + 6H2SO4 Sugars Sulphuric acid Two types of Heterotrophs: i) Photoheterotrophs: use light from sun to generate ATP, but need to take in organic compounds from their environment Example: bacteria - Chloroflexus, Halobacterium ii) Chemoheterotrophs: must obtain organic compounds for both energy and as a carbon source most heterotrophs Example: bacteria - Propionibacterium - genes that allow it to break down skin cells & consume products 25 representative organisms Heterotrophs Autotrophs prokaryotes eukaryotes source; U of S Image Prokaryotes - diversity of types of nutrition autotrophs photoautotrophs Cyanobacteria (e.g. Anabaena) heterotrophs Image source; U of S chemoautotrophs Sulphur bacteria photoheterotrophs chemoheterotrophs Dead sea bacterium (Halobacterium) Yoghurt bacterium (Bifidobacterium) Protists - diversity of types of nutrition Photoautotrophs Micrasterias Chemoheterotrophs Amoeba Fucus ciliate eating diatoms (phagotrophy) Images: U of S & Wikipedia Paramecium Didinium nasutum (predators of Paramecium) - uses specialized structures (toxicysts) to attached to prey and paralyze it. Then ingest its prey through a cytosome (= cell mouth) Images: Wikipedia Are all plants autotrophic ? Polytrichium (moss) RO Picea (Gymnosperm = cone-bearing plant) RO Lycopodium (clubmoss) RO Polypodium (fern) RO Lilium (Angiosperm = flowering plant) RO Images: U of S Are these plants autotrophic ? sundews Pitcher plants These are all ______________ Images from Campbell and Reece. 2005. Pearson-Benjamin Cummings and Wikipedia Venus flytrap What about parasitic plants ???? autotrophic or heterotrophic ? mistletoe a parasitic plant evergreen leaves photosynthesis ∴ autotrophic host mainly for water & mineral nutrients silver birch Image source: https://en.wikipedia.org/wiki/Mistletoe Are all plants autotrophic ? Indian pipe Bird's-nest Orchid Snow plant - _______________ chlorophyll or a functional photosystem pigment -------> p/s - need to get organic molecules from another organism : parasitizes mycorrhizal fungus Image from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings Monotropa uniflora (parasitic plant) Indian pipe , ghost plant or corpse plant ∴ heterotrophic mycorrhizal fungi = symbiotic association between a fungus & the roots of a photosynthetic plant [tree] Parasitizes fungi (gets organic molecules from plant) ∴ ________________ Photo: R. Rude B121 2020 Benefit to plant: Fungus extends reach of the roots, ñ water & nutrient uptake Benefit to fungus: Plant provides products of p/s [organic molecules: carbohydrates (e.g. glucose, sucrose)] Image from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings All fungi are ___________________ Allomyces Rhizopus Sordaria Agaricus (water mold) (bread mold) (plant saprobe) (mushroom) - nutrients are acquired by absorption (absorptive heterotrophy) extracellular digestion - some fungi use enzymes to digest large molecules directly, breaking them down into less complex compounds they can then absorb - other fungi use enzymes to break through the cell walls of other organisms allowing them access to the nutrients inside those cells Images: U of S All are heterotrophic Hydra Cnidarian Dugesia Flatworm Lumbricus earthworm Ampullaria snail Pisaster starfish Turbatrix roundworm Animals 8 ROs Cambarus crustacean Perca Fish Images: U of S Are all multicellular animals heterotrophic ? Elysia chlorotica - green sea slug (Atlantic seaboard of the USA) - relative of the nudibranchs Image: http://geek-prime.com/solar-powered-animals/ Characteristics of life Images from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings 3. Life conducts metabolism GK: metabolē = “change” all chemical reactions occurring within an organism (e.g., photosynthesis; breakdown of food into energy, etc.) 4. Organisms grow / develop All organisms increase their size (by increasing cell size and/or the number of cells). Many organisms change over time. metamorphosis (change in body structure) Characteristics of life 5. Images from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings Living organisms exhibit _______________________ ∴ regulate their internal environment Homeostasis = maintain an internal steady state (relatively constant): chemical & physical consistency in the face changes in surroundings Body heat - generated by using Energy from its food thick, insulating coat of down feathers White tailed ptarmigan (B.T. 40°C) compared to large changes in external temperature Characteristics of life 6. Life makes short-term _____________ to stimuli in the surroundings Common stimuli = heat, cold, light, sound, movement, touch, and other organisms The ability to respond to stimuli is essential to all aspects of life Protists have short-term responses to certain stimuli: Amoeba proteus (RO) Reaction Thermotaxis (temperature) Phototaxis (light) Chaemotaxis (chemicals) Negative moves away from low (10°C) and high (35°C) temperatures moves away from strong light and darkness quickly moves away acetic acid Positive does not move at 25°C (optimum temperature moves to low light is attracted to food Example: Living organisms can regulate their internal environment cichlid fish cichlid fish Astatotilapia burtoni (Burton’s Mouthbrooder) “macho” [dominant] “whimpy” [subdominant] Chemical signals (hormones): co-ordinates developmental, physiological & behavioral changes in an animal, in response to stimuli Images from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings What about plants ? Sensitive plant Mimosa pudica If only one leaflet touches, electric signals travel throughout plant causing the entire leaf to fold Venus flytrap Characteristics of life 7. Life reproduces itself - most obvious & unique characteristic of life Reproduction = production of new individual organisms (“offspring”) from living organisms (“parent” or “parents”) ___________________ = the duplication of genetic material - perpetuation is key to survival - all of the chemical & physical qualities of life, or those which characterize and define each life form are passed onto a new generation of cells & individuals - living organisms can reproduce by asexual reproduction and/or sexual reproduction 4 types of asexual reproduction 1. Fission: (a) one individual separates into 2 individuals of equal size = binary fission e.g., Bacteria - Escherichia coli Animal (Cnidarian) – sea anemone Protists – e.g. Euglena, Paramecium (RO) and Micrasterias (RO) Image: Principles of Biology (ISBN: 978-1-942310-72-3) Nature Publishing (b) one individual separates into __________________ of equal size = multiple fission e.g., Protist – Plasmodium (causative agent of malaria) Protist – Amoeba proteus (RO) : two modes of asexual reproduction Binary Fission Multiple Fission (in unfavourable conditions) Image: https://davidwangblog.wordpress.com/ life-cycle-and-reproduction/ 2. ___________ = new individual arises from an outgrowth of another (e.g., Hydra –RO) - “daughter” individual is of a different size Image: Principles of Biology (ISBN: 978-1-942310-72-3) Nature Publishing e.g., Pedomicrobium (bacterium) - flagellum to help new individual to swim away to find food (etc.) 3. _____________ and Regeneration = parent breaks off into pieces, each piece gives rise to a new individual (e.g. echinoderm; and Anabaena (blue-green alga) - RO ) Reports of this are not common in the common earthworm [Lumbricus terrestris (RO)] which uses sexual reproduction; but fragmentation & regeneration is common in its relative; the mudworm (Lumbriculus variegatus) 4. Parthenogenesis (animals) = development of an individual from an unfertilized egg (e.g., many insects; reptiles) For example: Desert-grassland whiptail lizards: There are parthenogenetic animals [parthenogenic animals] Colonial bees – e.g. Honey bee (Apis mellifera) Worker diploid ™ major function (mating) Queen stores sperm (several drones, < 2yrs) --->1000’s eggs Queen diploid ™ Sexual reproduction Drone haploid ¢ as sperm runs out eggs ----> drones parthenogenesis Image from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings Reproduction (a fascinating example) Amazon molly (Poecilia formosa) The “Amazon” molly is named after ______________________________ Amazon molly was first vertebrate in which unisexuality was recognized All individuals are ________________________. What is an important requirement for parthenogenic reproduction in this species? Parthenogenesis occurs when females mating with, and receiving sperm transfer from, a male molly but there are _______________________________. So, how can this be ? What is its evolutionary history (origins of the Amazon molly) ? Ancestor of molly produced from hybridization (125,000 years ago) between: ♂ Poecilia latipinna (sailfin molly) X ♀ Poecilia mexicana (shortfin molly) based on mtDNA derived from the _________________ zone of sympatry (coexistence) sailfin molly (Poecilia latipinna) X shortfin molly (Poecilia mexicana) Amazon molly (P. formosa) Parthenogenesis occurs when female Amazon mollies mate with, and receive sperm transfer from, a male sailfin molly or a male shortfin molly But it is parthenogenesis not sexual reproduction because the sperm _____________ fertilize the eggs, it only serves to activate the diploid eggs to develop - hence all offspring produced are females that are clones (= genetic copy) of their mother !!! Females Amazon mollies are dependant on the sperm for egg development hence their _______________ range is limited to where you find sailfin or shortfin mollies. ™ Ancestor -----> parthenogenesis AB heterozygous Genetic locus 1 Gametes A B only parthenogenesis Mitosis (doubling chromosomes) Progeny Genetic locus 1 AA AA homozygous for this & all loci Progeny *** clones of mothers BB BB asexual reproduction sexual reproduction parthenogenetic animals Desert-grassland whiptail lizards No Recombination -------> clones ** parthenogenetic diploid species adult females are homozygous at all gene loci therefore all their progeny are also homozygous (= clones) but this does not mean that there is no genetic variation in these species (many ‘maternal lineages’ & mutational changes) Green plated lizards Recombination -------> > genetic variation parthenogenesis animals = ____________ (in plants): asexual reproduction without fertilization [300 spp.] Dandelion seeds production without pollination 50-170 seeds/head single plant --> 2000 seeds sexual reproduction Definition [for plants & animals] = production of new individual by the joining of gamete to form a cell (zygote) by the process of _______________________. Flowering plants self-fertilization cross-fertilization pollination Image: Principles of Biology (ISBN: 978-1-942310-72-3) Nature Publishing Animals ______________-fertilization each individual is either male or female frogs external fertilization Planaria (RO) is also hermaphroditic Image source: U of S Mammals (e.g., Rhinoceros) Common earthworms (RO) are hermaphrodites (both male & female sex organs) internal fertilization Parasitic trematodes [flatworms] relatives of Planaria are hermaphrodites - mainly cross-fertilization but some species can use self-fertilization [but rare] For most organisms, establishment of an individual as either female or male begins in early embryonic development and remains fixed throughout its life. However, in some plant and animal species, individuals begin life as one sex, changing sometime later to the other in a process called _____________________________. Example: clown fish Individuals begin life as males, and some then change to become females live in small social groups but - a single mating pair consists of a large dominant female and a small male plus smaller subordinate non-breeders. Loss of the dominant female prompts [= provides the stimulus for] a sex change in her male partner and maturation of the most dominant immature fish as the new breeding male. sexual reproduction Definition [for bacteria, protists & fungi] i.e. where there are no separate sexes or individuals with “male” & “female” reproductive structures; they just have different mating types (+/- or donor/recipient cells) = production of new individual by the exchange of genetic material from two individuals of different mating types. _______________ : two organisms fuse along a common surface & exchange genetic material (gene transfer ------> genetic variation). There is no increase in the number individuals. bridge-like connection between two cells or sometimes direct contact between two cells e.g. BACTERIA - E. coli PROTISTS – Spirogyra and Paramecium (RO) Images from Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings Asexual reproduction Advantages - Large #’s of offspring produced rapidly - Only one individual required Disadvantage - Little or no genetic variation Sexual reproduction Advantages - Increases genetic variation new genotypes - Enhances reproductive success in changing environments Disadvantage - Locate a mate High genetic diversity means greater ability of some individuals to survive in a changing environment Some organisms use both sexual and asexual reproduction Paramecium (RO) Binary Fission (asexual reproduction) Can reproduce asexually 2-3 times a day. Image sources uncertain Conjugation (sexual reproduction) When there is overcrowding or environmental stress. Summary: Characteristics of life Living things............. 1. consists of one or more cells (that contain DNA ) 2. requires a constant input of energy and raw materials 3. conduct metabolism 4. grow / develop 5. exhibit homeostasis 6. make short-term responses to stimuli 7. reproduce Viruses (Latin word virus = toxin or poison) sub-microscopic particles [20-300 nm] smaller than a bacterium consist of genetic material (nucleic acid [ss or ds; DNA or RNA]) contained within a protective protein coat called a capsid - do not contain all 4 _________________ do not have a cellular structure (= basis for life) unable to replicate outside of a living system [Viruses do not _________________] they infect the cells of living organisms [incl. bacteria] = “infectious agents” because they cause disease Viroids - infectious particle of plants - do not have a cellular structure - depend upon enzymes of plant host for replication - lack ____________________ - consist of a small RNA molecule (usually single-stranded circular RNA molecule of several 100 nucleotides in length) - unlike viruses, RNA of viroids do not code for any proteins Prions – non-living entities - more simple than viruses - are __________________ - lack hereditary material (i.e., no DNA or RNA) - do not have a cellular structure - another infectious agent: BSE bovine spongioform encephalopathy - brain disorder - first diagnosed UK 1985 - prion induces abnormal folding in normal protein molecules - brain full of holes (“sponge”) eating infected beef causes Croutefeldt-Jacob Disease (CJD) & other diseases in humans Viruses, viroids and prions are non-living entities lack ____________________ Considered as replicators: not capable of reproduction or “independent” metabolism Water is the “matrix of life” H2O: ~ 60% body mass of most animals & > 95% of some plants - suspends the red blood cells to carry O2 to cells (animals) - for electrolytes & nutrients needed by cells - carries metabolic waste from cells - maintains osmotic pressure in cells - involved in transport of molecules in/out of cells Hypertonic and Hypotonic Hyper = greater Hypotonic solution Hypertonic solution H2O selectively permeable membrane Image: Biology 7th Edition, by Campbell and Reece. 2005. solute molecule (e.g., NaCl) Movement of water, constant problem for animal cells & some protists [but not for bacteria, some protists, plants and fungi] Animal cells & some protists Isotonic [solute] outside = inside cell no change Hypotonic lower [solute] outside cell Hypertonic higher [solute] outside cell cells rupture cells shrink as water enters as water exits freshwater animals/protists Bacteria, fungi, algae & plants have rigid cell walls - affects reduced Image: Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings Contractile vacuole Paramecium Amoeba Organelles : pump out excess water via pores in cytoplasm Images: Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings structural (= anatomical or morphological) adaptation Adaptation – is the evolutionary process [takes time] whereby a population becomes better suited to its habitat. – inherited characteristic of living organisms that enhances their chance of survival & reproduction in specific environments Water is the “_____________ of life” Each species is adapted to a set of environmental conditions Dehydration - loss of body fluids (water) below normal range Respiration can be a significant cause of water loss Marine mammals (e.g., polar bears, elephant seals), some terrestrial mammals and birds that live in environments where freshwater is infrequent (e.g., camels and penguins) main water source is by metabolizing fat stores “counter-current exchange” mechanism that minimizes water loss from respiratory system cold warm counter-current Heat: moves from warmer to colder temperature Nasal passages – bony shelf-like structures (turbinates) covered in a well vascularized layer of moist tissue & mucus [mucus: prevents drying of surface] _______________: As an animal inhales, air from the environment (cooler) passes across the nasal turbinates........ it is warmed and moistened, Then the surfaces of the turbinates cool due to evaporation (liquid ----> gas). _________________: When animal exhales, warm water-saturated air from the lungs passes across the cool nasal turbinates.............. water condenses (gas ----> liquid) rather than exiting to the external environment. Water stored in sinuses then swallowed. Image: https://www.richardzoumalan.com/rhinopedia/turbinates/ same mechanism for camels – in desert environments Nasal turbinates are highly ______________ -----> surface area of 1000 cm2 (humans: 160-180 cm2) “counter-current exchange” mechanism that minimizes water loss from respiratory system Camels - well adapted to its environment - ___________ on feet for walking on hot soft sand toes spread out for better grip - long strong legs for carrying load on back & keeping body further away from sand - a hard fat layer of skin around stomach and thick leathery patches on knee protects camel from the extreme heat while seating on the sand - long thick eye lids with double lashes reduce sand in eyes - ___________ (tough) split lips to eat thorny desert plants Adaptation to avoid dehydration Camels - well adapted to its environment Hump; storage area for ______________supply in times of need ------> metabolic water Other adaptations to avoid dehydration - thick fur insulates body against extremes of heat [during day] & cold [at night] - camels regulate their ____________________________ - can rehydrate very quickly [> 200 liters in 3 mins; lethal intake for most animals] - extremely __________ intestine (colon) for reabsorbing water - concentrated urine (preventing water loss) Camels regulate their body temperature: as environmental temperature increase, the camel can raise its body temperature, prevent sweating and thus prevents water loss Q: Why does a camel raise its body temperature in hot conditions (i.e. during the day)? Would it not want to lower its body temperature providing the same result as sweating in humans (lowers our temperature) when the external environment is warmer? Important: Air that is warmer than the body tends to heat an animal because heat always flows from a higher to lower temperature. 41°C heat 39°C heat camel environment camel does not overheat reduces water loss & energy At night: 39°C -----> 34°C heat --------> 5°C heat camel environment - thick fur insulates body against extremes of cold [at night] - camels regulate their body temperature (declines slowly at night) – so that there is not excessive cooling at night; therefore, no need to metabolize fat (reduces water loss & energy) At daybreak and during day: 34°C -----> 41°C heat 5°C --------> 39°C heat camel keeps the body cool camel does not overheat reduces water loss & energy environment Camels: adaptations to avoid dehydration Camels need to minimize water loss Can go ≈ 2 weeks without drinking water camels have reduced capability of regulating their body temperature (homeostasis) when they are dehydrated - can rehydrate very quickly [> 200 pints in 10 mins; lethal intake for most animals] - can tolerate 40% loss of body mass when food/water scarce [15% lethal for many _____________] Adaptations to avoid dehydration dormant for > 10 yrs 1mm long Tardigrades (water bear) can lose up to _____% of its body water live on water droplets on mosses and moist plants Many frogs behavioural Nocturnal (sleep during day – hide from sun) evaporation ↓ Waxy Monkey Frog (physiological) Seal in moisture - rub a waxy substance secreted by skin glands Images: Biology 7th Edition, by Campbell and Reece. 2005. Pearson-Benjamin Cummings