Species and Speciation Study Guide PDF

Unit 8: Species and Speciation Study Guide Name: _________________________ Biological species concept ​ Define species according to the biological species concept. ​ Describe limitations of the biological species concept, with mention of hybrids and...

Unit 8: Species and Speciation Study Guide Name: _________________________ Biological species concept ​ Define species according to the biological species concept. ​ Describe limitations of the biological species concept, with mention of hybrids and geographical separation. Speciation by splitting of pre-existing species ​ Define speciation. ​ Compare the process of speciation with that of gradual evolutionary change in an existing species. ​ State the impact of speciation and extinction on the total number of species on Earth. Difficulties distinguishing between populations and species due to divergence of non-interbreeding populations during speciation ​ Explain the difficulties in distinguishing between populations and species during speciation. Roles of reproductive isolation and differential selection in speciation ​ List two processes required for speciation to occur. ​ Define reproductive isolation. ​ Outline how reproductive isolation and differential survival lead to speciation. ​ Outline the speciation between chimpanzees and bonobos. Adaptive radiation as a source of biodiversity ​ Outline the cause and consequence of adaptive radiation. ​ Outline an example of adaptive radiation as a source of biodiversity. Differences and similarities between sympatric and allopatric speciation ​ Compare allopatric and sympatric speciation. ​ Explain temporal, behavioral and geographic isolation as mechanisms of reproductive isolation. ​ Describe an example of temporal, behavioral and geographic reproductive isolation. Biological species concept Linnaeus’s system of classification was the first formally recognized system of grouping organisms into species. In this system, organisms are grouped and subdivided into smaller and smaller categories of organisms, with species as the smallest, most exclusive grouping. The concept of species in biology has evolved over time and biologists have developed numerous definitions for “species,” none of which are fully agreed upon or without limitations. Linnaeus and other naturalists of the time period grouped organisms into species based strictly on “morphology” which is… The "biological species concept", championed by ornithologist Ernst Mayr (1942), has become a predominant way to define many species. A species is a: In other words, a species is a group of organisms that can breed and produce fertile offspring with each other but not with other groups. The biological species concept presents some challenges and limitations: Naturally and artificially A hybrid is …. produced hybrids ​ If they are not a species, how should one classify hybrids? ​ Since the parent organisms can successfully breed within captivity, are they actually separate species? A fixed definition of “species” may be arbitrary because…. Variation across geographical ranges In reality, species are often … Practical challenges of Determining if two individuals are the same or different species can be challenging. The testing if reproduction is standard involves observing natural breeding and the production of fertile offspring, but this possible between groups approach is often impractical in many ecosystems. ​ There are: ​ There are: Testing whether individuals are capable of interbreeding is not possible for: As a result, extinct life forms must usually be classified into species based on: Chronospecies are different stages in the same evolving lineage that existed at different points in time without splitting or branching. Given how this evolutionary change occurs… Divergence during See A3.1.5 speciation ↓↓↓ Speciation by splitting of pre-existing species Speciation is the process by which … Speciation is often depicted using a branching line diagram. In these diagrams, a common ancestral species is inferred at the branch point (〇 the “node”) and the new species that evolve from the ancestor are inferred at the tips of the branches (〇). The pattern can be repeated to create a tree pattern. Speciation through divergent evolution has resulted in an immense diversity of life on Earth. However, because of common ancestry… Gradual evolutionary change in a species over time is not speciation. ​ The alterations of a single species over time eventually produces a….. ​ However, throughout the change, there is …. ​ This type of change is often the result of … Total Number of Species on Earth Speciation __________________the number of species on Earth while extinction __________________ the number of species. While there is a high degree of uncertainty, there are estimates that more than 99% of all species that ever lived on Earth have gone extinct. Difficulties distinguishing between populations and species due to divergence of non-interbreeding populations during speciation Speciation usually happens _______________________, with populations becoming more and more different in their traits. However, genetically diverging populations may be hard to distinguish as unique species as the speciation process is occurring because … It can therefore be an arbitrary decision whether two populations are regarded as the same or different species. Roles of reproductive isolation and differential selection in speciation Speciation involves two processes: ① Reproductive Isolation ② Differential Selection In the first step of speciation, populations stop Once isolated, the populations may experience different interbreeding with each other. For speciation to occur selection pressures, such as: there must be barriers that … ​ ​ ​ ​ If natural selection results in selection for different traits in each population, then the populations will become … If the divergence results in the populations not being able to interbreed should they once again overlap, then the populations are now … Example: Chimpanzee and Bonobo Approximately 1.8 million years ago, the ancestors of modern bonobos and chimpanzees were a single species that lived in the rainforests of the Congo. Speciation occurred and today bonobos and chimpanzees are different species. ① Reproductive Isolation ② Differential Selection North of the river = CHIMPANZEES South of the river = BONOBOS Differences and similarities between sympatric and allopatric speciation The barrier to interbreeding can occur because populations become geographically separated (allopatric speciation) or can occur within the same geographic area (sympatric speciation). Allopatric Speciation Examples: Geographic Barrier Species ① ② Sympatric Speciation Non-Geographic Barrier Example ① Behavioral ② Temporal Adaptive radiation as a source of biodiversity Definitions: Biodiversity Ecological Niche Adaptive radiation is a pattern of speciation in which … ​ An event opens new niches or frees up previously occupied environmental niches, making way for evolution of new species that adapt to the vacant living spaces. ​ Starting with a single ancestor, natural selection results in multiple related species exhibiting different morphological, physiological and behavioral adaptations to the new niches. Niches may become available when: Mass Extinctions Island Formation What caused the How many species How many years did it What was the Example niches to be available were formed from the take for the adaptive ancestral species? for new species? ancestral species? radiation to occur? Extinction of Dinos Island Formation