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1/25/2017 Homeostasis External vs. Internal conditions • Regulation of internal body conditions • Often regulated via negative feedback system Thermostat Input feedback Furnace Air Conditioner • Three general types of managing internal conditions – Avoiders – Conformers – Regulators • Prefix: Homeo or poikilo • Suffix: thermo, haline etc… Internal Environment Hot or cold air External Environment Avoiders, Conformers and Regulators Various methods for regulating, conforming or avoiding Icefish: Stenothermal or eurythermal? Oligothermal or polythermal? Homeothermic or poikilothermic? Ectothermic or endothermic? Avoider, conformer or regulator? 1 1/25/2017 Mechanisms of Adaptation • DNA – genotype • Phenotype – what selection acts on. • Review basics of protein synthesis. • Genes are expressed to produce proteins. Proteins perform most functions, make up what the phenotype is. Overview - Control of Gene Expression + environment = Proteins • Protein diversity – Number proteins= 20n (n=# AA) – Sequence of 10 AA -> ~10 trillion different proteins • Structure and shape of proteins • Ligand • Allosteric effect • Protein actions – Pump – Motor – Enzyme – Etc… Gene Regulation • Gene regulatory proteins (activators and repressors) • Promoter region and transcription factors 2 1/25/2017 RNA Processing Protein Evolution • Point mutations -> fine tuning of existing proteins • Duplications – Pseudogenes – Gene families • Intron-exon system – one gene can produce multiple proteins through different splicing (alternative splicing) Protein Evolution • Recombination – Homologous (crossing over) or non-homologous • Protein complexes – Form of quaternary structure Hemoglobin is also a well known gene family… • Multiple forms: – Maternal vs. fetal forms – Can evolve independently • Expected to be under strong selection 3 1/25/2017 Feedback loops • Key course concepts: – Homeostasis – Energetics – Optima Allometry Allometry • “The structural and functional consequences of changes in size or scale among otherwise similar organisms” – Schmidt-Nielsen • Isometric geometric shapes: Head width ~ 13% of height Head width ~ 9% of height 4 1/25/2017 1000 1200 500 1000 200 50 100 Surface Area Vol 1436.8 SA 615.8 400 – Very basic functionality (exchange with the environment) works differently at those scales 800 • Bacteria – 10-13 grams • Blue whale – 108 grams • For a sphere (by definition, an isometric shape) – Surface Area = 4πr2 – Volume = 4/3πr3 – As length increases, volume increases at greater rate than total surface area – Slope of the double log plot is 2/3 600 • Anything that does not change isometrically, changes allometrically – Isometry, negative and positive allometry • Why it matters: – Organisms vary in size over 21 magnitudes Allometry Surface Area Allometry 20 200 Vol 523.6 SA 314.2 0 Vol 33.5 SA 50.3 0 1000 2000 3000 4000 5 10 20 50 Volume • Surface area to volume ratio shows negative allometry • Cellular level – physiological constraint on cell size • Organism level - the rate of exchange with the environment changes dramatically with size. 200 500 1000 2000 5000 Volume Allometry • Relationships can be easily described mathematically • Comparing lines tells us a lot about species Morphological or Physiological Trait Allometry of surface area 100 Body Size 5 1/25/2017 Allometry Example allometric relationships • Most of the time we will examine allometry in terms of body size • Power function: – Y=a Mb • Not always linear • Log form of equation – Log Y = log a + b log M 20.0 10.0 2.0 log Y 5.0 • Hemoglobin concentration, cell size – If something is isometric, b=1.0 • Eg. blood or lung volume in mammals 1.0 a=1.0 b=0.67 a=10 b=0.67 a=1.0 b=1.15 a=1.0 b=0.25 – Positive allometry (b>1) – mammal bone thickness b= 1.08 0.5 – – – – Y = trait of interest a = proportionality constant b = slope M = mass • Why? What does this mean biologically? 0.2 • • • • • The proportionality constant and mass exponent describe allometric relationships. • b – how something changes with size – No relationship to size (technically, negative), b=0 0.1 0.5 1.0 5.0 log Mass 10.0 50.0 100.0 – Negative allometry (b<1) – human skull size, mammal heart rate • a – how the intercept changes among lines 6