Biology 3305 Past Paper PDF

Biology 3305 Human and Comparative Physiology “Nothing in biology makes sense except in the light of evolution” Theodosius Dobzhansky Russian-American geneticist and evolutionary biologist Animals are t...

Biology 3305 Human and Comparative Physiology “Nothing in biology makes sense except in the light of evolution” Theodosius Dobzhansky Russian-American geneticist and evolutionary biologist Animals are typically matched to their environmental challenges. The meaning of adaptation: 1. A short-term compensatory change (phenotypic plasticity) acclimation: persisting change because of induced exposure to high/in temp acclimatization: persisting change because of environmental exposure tolugh/low temp 2. A character trait hemoglobin 3. A process evolution The meaning of adaptation: 1. A short-term compensatory change (phenotypic plasticity) acclimation acclimatization 2. A character trait hemoglobin 3. A process evolution Acclimatization: The persisting spectrum of changes due to prolonged exposure to environmental conditions such as high or low temperature. Acclimation: The persisting change in a specific function due to prolonged exposure to an environmental condition such as high or low temperature. This is often induced experimentally (i.e. in a laboratory). *Particular acclimatisations or acclimations are not adaptations, but the capacity for acclimatisation or acclimation is an adaptation. The meaning of adaptation: 1. A short-term compensatory change (phenotypic plasticity) acclimation acclimatization 2. A character trait hemoglobin 3. A process evolution Adaptation (or Evolutionary Adaptation): Evolution through natural selection leading to an organism who’s physiology, anatomy and behaviour are matched to the demands of it’s environment. So… we must be careful. Process that leads to changes in allele frequency coding for traits that affect fitness. Occurs over many generations; a slow process; not reversible. A trait is an adaptation only if there is evidence it has evolved as a consequence of selection Traits do not evolve for a reason Traits appear by chance , mutation Persistence of a trait is due to- selection and the relative benefit that trait confers to ansequences) - the bearer of the trait (fitness). ↳ abulty to pass to thenext generations genes Phylogenetic inertia  The interaction between ancestral traits and selection, in the context of ancestral environments. The fundamental genetic code that makes an organism that organism ex diff speciesof bats but they all have wings a , Therefore… We often do not see optimal or best “solution” to a challenge. “Evolution is a tinkerer, not an engineer.” Francois Jacob Nobel Prize in Physiology or Medicine 1965 “…for their discoveries concerning genetic control of enzyme and virus synthesis…” Shared with: André Lwoff, Jacques Monod Adaptation An adaptation is a mechanism or trait that is a product of natural selection Adaptive significance Answers the question of why a mechanism or trait is an asset Why did natural selection favour the evolution of the trait or mechanism? Mechanism and adaptive significance are distinct concepts. for evolution now it work I its value e.g. What is the adaptive significance of hemoglobin? Wong (poor) answer – hemoglobin binds oxygen and allows blood to deliver oxygen to tissues. Correct (better) answer – the adaptive significance is that animals with hemoglobin are able to engage in sustained aerobic activity which increases chance of survival. Mechanism does not imply adaptive significance, and, adaptive significance does not imply mechanism. e.g. What is the adaptive significance of hemoglobin? Wong (poor) answer – hemoglobin binds oxygen and allows blood to deliver oxygen to tissues. This answer explains a mechanism (binding of oxygen molecules to molecules of hemoglobin is HOW blood uses hemoglobin to carry oxygen to tissues.) Does not answer why hemoglobin confers a survival advantage. Correct (better) answer – the adaptive significance is that animals with hemoglobin are able to engage in sustained aerobic activity which increases chance of survival. This answer isn’t rooted in mechanism – there are several ways to get more oxygen to tissues (e.g. increase heart rate, vasodilate capillary beds to increase amount of blood at the tissues, increase respiration rate, etc…) This answer explains why animals with hemoglobin might have a greater survival advantage over those without hemoglobin. Not all traits (differences) are adaptations Adaptationist programme Gould and Lewontin, 1979 “The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist programme” The adaptationist programme is the notion is that if a trait exists then it must be an adaptation and have adaptive significance. This notion led to unsubstantiated, sometimes wild, ‘just so’ type stories and explanations to try to account for why a trait might be adaptive – despite a lack of evidence. A real problem for physiology! For a trait to be considered an adaptation… Must have evidence that a character or trait (adaptation) came about by natural selection … otherwise… it’s a ‘putative’ or ‘possibly an’ adaptation.  Reasons, other than selection, that explain why traits persist - Genetic drift straits - Genetic linkage and pleiotrophy Gene affecting morethan - A trait may persist because it does no harm (or is low in ‘cost’) ~ A trait may persist despite the current selective regime (phylogenetic inertia) ~ Traits may have been selected for in a past environment that no longer exists -preadaptation / exaptation a not is necan Predapbatmexaptadded that pastement appendix S Humans have many vestigial characters *pleiotrophy – a gene that has an effect on more than one trait  exampleof exaptation trants The freshwater Mexican cavefish is the same species as the surface-dwelling Mexican tetra, although their appearance varies wildly. While the Mexican tetra has eyes and a silvery-gray body, the Mexican cavefish has lost its pigmentation and grown skin over its now useless eyes as it gradually adapted to living in complete darkness. https://www.livescience.com/18069-evolution-blind-cavefish-image-gallery.html helps to answer adaptive significance questions The importance of the comparative method (comparative approach). A phylogeny* gives us information about evolutionary history that can be important in determining if a trait or character is an adaptation. It can provide information about the ‘direction’ of evolutionary change, provided an appropriate outgroup is chosen. *A phylogeny provides the ‘history’ of the evolution of an organism by showing relationships to other organisms. Phylogenies can be constructed using a variety of techniques (molecular techniques and morphological/taxonomic techniques). NN-RBC : non nucleated red blood cell NN-RB3C N-RB : nucleated red blood cell N-RBC NW-RBC N-RBC N-RBC N-RBC ↑ => Loss of nudei has N-RBC ansm red blood org cells with nuclei organism RBC without a nucleis adaptive significance of RBC to nuclei using comparatue approach to answer : at the tree Nucleated RBC came first looking - so allaganisms has nucleated RBC exceptfrom evolution cats s human (mammal) which got losts throughstill have - phylogenetic Inertia can be the reason why the organisms their W-RBC's - loss of nudeifor mammals could be a front of chance. Has nucleated RBC’s Has nucleated RBC’s Loss of nuclei Approaches to studying adaptation Biologists can’t observe evolution directly… but we can… Use the comparative method Use phylogenetic reconstructions Look for independent evolution in the context of different environments Use statistical and analytical methods that use data from appropriately chosen related species to make inferences Use lab populations followed over many generations Directly observing changes in allele frequencies in response to imposed stressors Use single generation studies of individual variation Capturing animals and analyzing the frequency of alleles in the sample then releasing them and following them to see which survive in relation to the environment. Genetic studies of natural populations Observing the frequency of alleles in relation to populations with different environmental conditions. Create variation and examine its effect w molecular Genetic manipulation biology Gene substitutions, knockouts, etc… Manipulate structures on organisms to determine the effect Relationship between Phenotype and Genotype