Mechanisms of Evolutionary Change: (pp.501-513)24.4- Speciation can occur rapidly or slowly and can result from changes in few or many genes.- Speciation is the evolutionary process by which new biological species arise- The Time Course of Speciation:- Punctuated equilibria describes the periods of non-change punctuated by sudden change.- Punctuated patterns indicate that speciation occurred relatively rapidly. However, a change over a time period such as 50,000 years (short in geologic terms) in a species that lived 5 million years cannot be seen in the fossil record.- Other species change gradually over time.- We still can not see the species change because reproductive isolation can not be fossilized. - Speciation Rates- The punctuated pattern suggests that once speciation begins, it can be completed fairly fast. - New species can arise rapidly once divergence begins.- Millions of years may pass before a newly formed species will itself give rise to another new species.- Speciation begins only after gene flow is interrupted- by environmental conditions or unpredictable events- Studying the Genetics of Speciation- In a few cases, A change in a single gene causes the evolution of reproductive isolation. - ex. monkey flowers, fig.24.20, pg. 504(9th)- In other organisms, the speciation process is influenced by larger numbers of genes.- ex. fruit fly (pg.504)- Studies suggest that few or many genes influence the evolution of reproductive isolation and hence the emergence of new species.- From Speciation to Macroevolution- Speciation begins with small changes that eventually lead to much different groups than their ancestors. - When one group grows larger, another group could become smaller due to predators.- Cumulative effects of speciation help to shape macroevolution that are evident in the fossil records. Chapter 22: Descent with ModificationMechanisms of Evolutionary Change- Galapagos Islands: Geographical Separation of Species- Darwinʼs Focus on Adaption- characteristics of organisms that enhance their survival and reproduction in specific environments.- Galapagos Finches- Cactus-eater, insect-eater, seed-eater all had beak variations, or adaptations over time.- Natural Selection: a process in which individuals with certain inherited traits leave more offspring than individuals with other traits.BOOK NOTES: TEST 1 BIOL1108"The Origin of Species: Darwin- Darwin developed two main ideas: that descent with modification explainʼs lifeʼs unity and diversity and that natural selection brings about the match between organisms and their environment.- Descent with Modification: all organisms descended from an ancestor that lived in the remote past. As the ancestral organism lived in various habitats over the years, it changed and adapted to meet its specific needs. - Evolutionary Trees where each fork represents a common ancestorArtificial Selection, Natural Selection, and Adaptation- Darwin proposed Natural Selection to explain the observable patterns of evolution. - Artificial Selection: humans have modified other species over many generations in order to produce desired traits by selecting and breeding certain individuals.- e.g. crops, livestock, etc.- Darwinʼs Observations & Inferences from Nature- Observation #1: Members of a population often vary in their traits- Observation #2: Traits are inherited from parents to offspring- Observation #3: All species are capable of producing more offspring than their environment can support.- Observation #4: Owing to lack of food or other resources, many of those offspring do not survive.- Inference 1: Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals.- Inference 2: This unequal ability of individuals to survive and reproduce will lead to the accumulation of favorable traits in the population over generations.BOOK NOTES: TEST 1 BIOL1108"- Natural Selection: A Summary- Natural selection is a process in which individuals that have certain heritable characteristics survive and reproduce at a higher rate than other individuals.- Over time, natural selection can increase the match between organisms and their environment.- In an environment changes, or if individuals move to a new environment, natural selection may result in adaptation to these new conditions, sometimes giving rise to new species in the process.- Individuals DO NOT evolve, but populations over time.- Natural Selection only influences HERITABLE genes.- Environmental factors vary from place to place and over time.22.3Direct Observations of Evolutionary Change1. A Change in the food source of a population:BOOK NOTES: TEST 1 BIOL1108"2. A Spread of Drug Resistant Bacteria- (mRSA) Methicillin-resistant S. aureusBOOK NOTES: TEST 1 BIOL1108"- Bacteria contained enzyme penicillinase that destroyed penicillin, so scientists developed methicillin, which bacteria also eventually developed resistance to.- Methicillin works by deactivating a protein that bacteria use to synthesize their cell wall. - Resistant peoples used other protein to synthesize bacterial cell wall that was not affected by methicillin antibiotic. - These multiple strains of the bacteria are able to transfer genetic information over the years, allowing for multi-antibiotic resistant forms of the bacteria to exist.- These two examples highlight two important points about Natural Selection:- Does not create individuals, but selects them randomly, depending on time and place.3. Fossil Record- Record shows us many organisms have become extinct; Also shows evolutionary changes that have occurred over time in groups of organisms.- Ex. [Fig. 22.16] The transition to life in the sea.- fossil record shows origin of a major new group of mammals “cetaceans” and how they transitioned from land to sea.4. Homology- “analyzing similarities between different animals.”- Characteristics that were in an ancestral organism were modified to fit their environment over time.- Homologous Structures: represent variations on a structural theme that was present in their common ancestor.- e.g. (mammalian forelimbs) even though they have become adapted for different functions, the forelimbs of all mammals are constructed from the same basic skeletal elements.- Vestigial Structures: remnants of features or “leftover structures” that served important functions in the organisms ancestors.BOOK NOTES: TEST 1 BIOL1108"- ex.