Macroevolution PDF

Macroevolution Differences in Macro- and Microevolution Characteristics Microevolution Macroevolution 1. Definition Small-scale changes in gene Major or large-scale frequencies of a population evolutionary changes over a over a shor...

Macroevolution Differences in Macro- and Microevolution Characteristics Microevolution Macroevolution 1. Definition Small-scale changes in gene Major or large-scale frequencies of a population evolutionary changes over a over a short period of time large period of time 2. Level Occurs at intraspecific level Occurs at interspecific level 3. Range Within species or population Above the level of a species/ population 4. Causes Mutation, selection (natural or Occurs due to extended artificial), genetic drift, gene microevolution flow 5. Detection Directly observable through Not directly observable; may experimental evidence need to consider fossil evidence 6. Example Bacterial strains that have Evolution of bat wings and loss acquired antibiotic resistance of limbs in snakes and lizards  Macroevolution Difference in macro- and microevolution The changes are spread over large time periods These changes are observable as a result of evolutionary phenomena, leading to formation of new species  Macroevolution What happens in the macroevolution? It may involve evolutionary changes in two interacting species, as in coevolution, or it may involve the emergence of one or more brand new species It generates entirely new species that must adapt to a substantially different landscape It occurs over a significantly long period of time (millions of years)  Macroevolution Mechanism of Macroevolution Mutation Migration or Gene Flow Genetic Drift Natural Selection  Macroevolution Mechanism of Macroevolution a. Mutation Homeotic (Hox) genes expression patterns correlate with transitions in animal axial pattern Mutations in Hox genes have long been suggested as potential causes of morphological evolution In metazoans about 400 million years ago, six-legged insects diverged from crustacean-like arthropod ancestors with multiple limbs Gain and loss of transcriptional activation and repression functions in Hox proteins was a plausible mechanism to diversify morphology during animal evolution  Macroevolution Mechanism of Macroevolution using HOX genes Hox genes in different organisms  Macroevolution Mechanism of Macroevolution Hox genes in different organisms Cluster Human Chromosome Genes HOXA1, HOXA2, HOXA3, HOXA4, H HOXA@ chromosome 7 OXA5, HOXA6, HOXA7, HOXA9, HOX A10, HOXA11, HOXA13 HOXB1, HOXB2, HOXB3, HOXB4, HO HOXB@ chromosome 17 XB5, HOXB6, HOXB7, HOXB8, HOXB 9, HOXB13 HOXC4, HOXC5, HOXC6, HOXC8, HO HOXC@ chromosome 12 XC9, HOXC10, HOXC11, HOXC12, H OXC13 HOXD1, HOXD3, HOXD4, HOXD8, H HOXD@ chromosome 2 OXD9, HOXD10, HOXD11, HOXD12, HOXD13  Macroevolution Mechanism of Macroevolution a. Mutation  Macroevolution Mechanism of Macroevolution a. Mutation Ubx patterns T3 largely by repressing genes involved in wing formation In Ubx loss-of-function mutants, Ubx no longer represses wing genes, and the halteres WT develop as a second pair of wings, resulting in the famous four-winged flies. When Ubx is mis-expressed in the second thoracic segment, such as occurs in flies with Mutant the "Cbx" enhancer mutation, it represses wing genes, and the wings develop as halteres, resulting in a four-haltered fly.  Macroevolution Mechanism of Macroevolution b. Migration or Gene Flow Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies Any movement of individuals, and/or the genetic material they carry, from one population to another. Gene flow includes lots of different kinds of events, such as pollen being blown to a new destination or people moving to new cities or countries  Macroevolution Mechanism of Macroevolution b. Migration or Gene Flow  Macroevolution Mechanism of Macroevolution b. Migration or Gene Flow  Macroevolution Mechanism of Macroevolution c. Genetic Drift The hypothesis that Genetic Drift plays a role in the evolution of new species: It can result in the loss of rare alleles and decrease the gene pool. It can cause a new population to be genetically distinct from its original population  Macroevolution Mechanism of Macroevolution c. Genetic Drift Initial population shows almost equal number of alleles existing among them. As a result of genetic drift in the initial population, the latter populations showed the disappearance of gene variants from the population  Macroevolution Mechanism of Macroevolution c. Genetic Drift Genetic drift in a population can lead to the elimination of an allele from a population by chance. For instance, Rabbits with the brown coat color allele (B) are dominant over rabbits with the white coat color allele (b). In the first generation, the two alleles occur with equal frequency in the population, resulting in p and q values of 0.5. Only half of the individuals reproduce, resulting in a second generation with p and q values of 0.7 and 0.3, respectively. Only two individuals in the second generation reproduce, and by chance these individuals are homozygous dominant for brown coat color. As a result, in the third generation the recessive b allele is lost.  Macroevolution Mechanism of Macroevolution d. Natural Selection Natural selection is the process through which species adapt to their environments. It is the engine that drives evolution English naturalist Charles Darwin developed the idea of natural selection after a five-year voyage to study plants, animals, and fossils in South America and on islands in the Pacific. In 1859, he brought the idea of natural selection to the attention of the world in his best-selling book, On the Origin of Species.  Macroevolution Mechanism of Macroevolution d. Natural Selection Natural selection can lead to speciation, where one species gives rise to a new and distinctly different species. It is one of the processes that drives evolution and helps to explain the diversity of life on Earth. Natural selection explained how a wide variety of life forms developed over time from a single common ancestor. If the environment changes rapidly, some species may not be able to adapt fast enough through natural selection. Through studying the fossil record, we know that many of the organisms that once lived on Earth are now extinct.  Macroevolution Mechanism of Macroevolution d. Natural Selection Darwin’s finches evolved new traits by natural selection  Macroevolution Mechanism of Macroevolution d. Natural Selection Types of color vision among major primate groups. Apes and Old World monkeys have three types of visual pigments, whereas nearly all male New World monkeys and prosimians have two types of visual pigments. Howler monkeys are unusual New World monkeys who have ‘re-evolved’ a third visual pigment through a gene duplication event.  Macroevolution Mechanism of Macroevolution d. Natural Selection