BIOL1070 Evolution Quiz 3 PDF

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Quiz 3 ADAPTATION AND SPECIALIZATION ● There is an enormous diversity of species occupying a wide range of very different habitats, relates to processes that generate new biological diversity + those that eliminate existing diversity ● Organisms are generally well-suited to life in their particular habitat, result of long periods of evolution by natural selection ● Mutation - Origin of new genetic variation ● Genetic Drift - Changes due to chance, specifically founder effects and population bottlenecks ● Gene Flow - Movement of genes among populations, form one population to another ● Natural Selection - Non-random differences in survival/reproduction among individual entities on the basis of differences in heritable characteristics ● Adaptation - A characteristic that enhances the survival/reproduction of organisms that bear it, relative or alternative character states ○ A physical, physiological, behavioural or other characteristic evolved through natural selection. ○ NOT the change undergone by an individual organisms during its lifetime in response to external conditions ● Population - A group of interbreeding individuals and their offspring ● Alleles - Alternate forms of a gene (brown and blue for eyes) ● Genotype - The set of genes possessed by an organism ● Phenotype - The physical expression of the genotype (in combination with the environment) ● Frequency - Proportional representation of a phenotype, genotype, gamete, or allele in a population (6/10 have blue eyes = 60% = 0.6 frequency) THE BASIS OF NATURAL SELECTION ● Darwin 2 major objectives: ○ Provide convincing evidence that species are related through common ancestry ○ Argue that his mechanism of natural selection could account for changes through time and the resulting differences among species ● Natural Selection is unlike Artificial selection in that it involves no choice by any particular agent

● How does natural selection occur? ○ Individuals within populations are variable - Not every individual is identical in a population ○ This Variability among individuals is at least partly heritable Offspring look like their parents and not strangers because of the existence of a mechanism of inheritance by which traits are passed on from parent to offspring. ○ Not everyone survives and reproduces, and some individuals are more successful than others ■ Overproduction - More offspring are produced in each generation than could possibly survive ○ The differential survival and reproduction of individuals is associated with the heritable variation among individuals (it is non random) - Individuals who do manage to reach adulthood and have offspring are on average better suited to surviving and reproducing in their particular environment because of the traits they inherited from their parents. ● Ecology says populations have the potential to increase exponentially BUT populations generally remain stable once they reach a certain size AND natural resources are limited ● Hereditary says individuals in a population are not identical, they vary in many characteristics AND many characteristics are heritable ● Together, not all offspring that are produced survive and reproduce, because of a struggle for resources AND some individuals are more likely to survive and reproduce than others because of their heritable traits ● Finally, Differences in survival and reproduction among individuals are non-random, with some traits being passed on at a higher rate than others and increasing in proportion in the population from one generation to the next HOW NATURAL SELECTION WORKS ● Evolution of Antibiotic Resistant Bacteria - Individual bacteria vary in sensitivity to antibiotic treatment, the most susceptible are killed early in treatment whereas more resistant ones survive and reproduce. Eventually the population is composed of only resistant individuals. ○ Exposure to antibiotics does NOT cause individual bacteria to become resistant, resistance does NOT develop in bacteria, it EVOLVES in a population of bacteria

○ Resistance genes can move from one population of bacteria to another though gene flow TEN REALLY IMPORTANT POINTS ABOUT NATURAL SELECTION 1. Natural Selection doesn’t create new traits by itself, it just changes the amount of variation that is already present in a population. It often reduces the amount of variation because some are eliminated 2. Mutations are the source of new variation. The repeated interaction between mutation and natural selection is what leads to evolution and new adaptive features 3. Mutations are random and they do not care what happens to the organism as a result, it’s literally just genetic error (misconception that adaptation happens by chance) 4. Mutations have three outcomes: ○ Neutral (no phenotypic effect) ○ Deleterious (bad effects) ○ Beneficial (positive effects) ■ Rare, and deliver only minor advantages that can increase the proportion in the population over many generations, 5. No organism changes as the population adapts, what we see is changes in the proportion of beneficial traits across multiple generations 6. Direction in which change happens is dependent on the environment, the environment can make previously beneficial traits neutral or detrimental vise versa 7. Adaptation does not result in optimal characteristics it is limited by historical, genetic and developmental limitations and by trade-off among features 8. Variants that happen to result in a greater survival and reproduction rate compared to other variants are passed on more frequently. 9. Natural Selection and Adaptation can’t predict the future, it does not produce features on the grounds that they might become beneficial in the future, adaptations are always a result of experiences by generation in the past 10. Natural Selection is NOT the only mechanism of evolution, mutations, genetic drift and gene flow can also change the proportion of variants in a population

NATURAL SELECTION AND ADAPTATION ● Shell Morphology, Thames River, Ontario ○ Shells adapt to high energy and low energy river systems ● Byssal Threads in Juveniles and in species with Small Adults, Belle River, Michigan ○ Byssal threads keep mussels in place in the substrate till they are developed enough to hold their own ○ The ray bean maintains the byssal thread because it’s still significantly small even as an adult ○ Juvenile snuffbox, byssal thread is literally a string that holds it to rocks, snuffbox is endangered THE EVOLUTION OF COMPLEX ADAPTATION ● Mantle Lured in Unionid Mussels (variability among species) Thames River ○ Genus Lampsilis are the ones with special lures (pocketbook) but there are sooo many other kinds! ● Mantle tissues aid in making shells in a process of co-option (a feature that serves one function takes on a new function while still serving original function) ● Tissue was modified (co-opted) to from lures and it continues to fulfill its original function while being used to attract fish hosts and complexity varies among species ORIGINS AND LOSSES OF BIOLOGICAL DIVERSITY ● Speciation (origin of new species); Extinction (loss of existing species) WHAT IS A SPECIES? ● Genetic Isolation - species are groups of organisms that are genetically separate from other such groups. ○ Species are essentially groups of organisms that share genes with each other, but for which there is little or no gene flow to or from other groups ● We get more species when populations become genetically separated and go on to form two or more species from an ancestral species ● We lose species when these genetically separate groups dissapear GENE FLOW AND GENETIC ISOLATION ● The net effect of gene flow is to cause two populations to become more similar to each other since their gene pools mix ● On the flipside, new species that are genetically isolated can only form is some factor prevents gene flow between populations ● Barriers that can affect gene flow:

○ Geographical Barriers - New mountain ranges rising, an uncrossable river forming, a new population being founded on a distant land ○ Ecological Specialization - eating different foods, being nocturnal/diurnal, living in different parts of a lake, parasites specializing in different hosts ● Conservation Implications of information about gene flow: ○ If stream genetics are mixing with lakes genetics, if the populations are distinct or not to protect. ● Knowing how and when genetic isolation (gene flow stopping) is also central to evolutionary investigations. ○ When a formerly united ancestral population split into 2 distinct lineages that then continued to evolve separately. EXTIRPATION AND EXTINCTION ● Extinction is forever, once a unique evolutionary lineage disappears, it does not return, unique genetic combinations that occur are unlikely to ever happen again ● Endangered Species: abundance has dwindled severely, will be lost without some action to protect it ● Extinct Species - Gone from earth, no living representative found any longer ● Extirpation - Individuals of a species still exist but are no longer found in an area where they were once common ● Human activity plays a larger role in affecting mussel species survival MASS EXTINCTION ● In these events, 50% or more of an existing species may be lost in a relatively short period of time (tents to hundred of thousands of years) ● Background Extinction - loss of small numbers of miscellaneous species ● Mass Extinction - affect entire groups of species, losing not just one individual species but entire clades ● Mass Extinction Events: ○ Cretaceous-Tertiary (K-T) - 65 million years ago, dinosaurs disappeared after more than 150 million years of success. ■ Caused by a meteorite near the Gulf of Mexico which set off a variety of environmental changes that affected the entire planet ○ End Permian Event (The Great Dying) - 250 million years ago, 95% of species are thought to have vanished during the event, nearly all multicellular life disappeared. Tokk 100 million years for biodiversity to recover

BIODIVERSITY RECOVERY AND FAUNAL TURNOVERS ● Mussels are bivalve molluscs, today bivalves (mussels, oysters, clams, scallops) are the most common form of aquatic animals with external two-part shells. ● 100 million years ago, the phylum Brachiopoda was dominant, they are not closely related to bivalve mussels they represent convergent evolution ● Mass Extinctions are typically followed by a spike in diversification as new niches are opened and surviving lineages diversify ● Faunal Turnover - substantial reorganization of biodiversity ○ Dinosaurs disappearing and mammals diversifying after the K-T event, Brachiopods vanishing and bivalve molluscs becoming diverse after The Great Dying THE HOLOCENE EXTINCTION EVENT ● Caused entirely by anthropogenic factors ● Pollution, Climate Change, Habitat Destruction, Overharvesting, Deforestation, Transmission of invasive species and Competition for resources impact the world’s biodiversity ○ What has taken millions of years of diversification to arise is now being eliminated in decades...