Chapter 13: Adaptation and Species PDF

Chapter 13: Adaptation and Species SCB 101 Professor Calkins Adaptation Adaptation: The evolutionary process by which an organism becomes better able to live in it’s habitat Can be a trait that is advantageous to an individual or a population Limit...

Chapter 13: Adaptation and Species SCB 101 Professor Calkins Adaptation Adaptation: The evolutionary process by which an organism becomes better able to live in it’s habitat Can be a trait that is advantageous to an individual or a population Limits of Natural Selection Natural selection is not goal- oriented Only acts upon the variation present in population Only operates within historical constraints inherited from ancestors Therefore, adaptations also act within the confines of the genetics that an individual has to pass on. Remember, mutations enable variations to occur What is a Species? Species: members of a group that can and do mate with one another and produce fertile offspring According to the biological species concept, a species is a group of natural populations that can interbreed to produce fertile offspring, but cannot interbreed with other species. They are reproductively isolated from other populations. Defining “species” The Biological Species Concept: Defines species as being able to interbreed AND produce VIABLE offspring Hybridization shows the close relatedness of species, but because hybrids are not viable, they are not considered a species. One Species or Two? Scientists may use biogeographical information, DNA sequence similarity, and morphology to identify and distinguish species. Morphology: the form and structure of an organism or any of its parts  Speciation Scientists have evidence that species branch off from existing species, a process called speciation Even though speciation can take thousands of years or more, evidence is left behind that allows scientists to reconstruct these ancestral relationships  What types of evidence for speciation are left behind in modern-day organisms? (hint: think Chapter 11) Shared characteristics among living organisms (Homologous traits) Review: Similarities and differences in DNA Vestigial traits Common patterns of embryo development  Speciation occurs in three stages: 1. Genetic isolation 2. Genetic divergence Speciatio Through Natural Selection Through Genetic Drift n or Mutations 3. Secondary contact Confirms speciation  Geographic isolation: when a Genetic Isolation geographic barrier prevents populations from getting together to mate, blocking gene flow  Mountains, rivers, valleys, and canyons Genetic Genetic divergence: the accumulation Divergenc of differences in the DNA sequences of genes in two or more populations of Results organisms over time in the populations becoming e more and more genetically dissimilar This occurs via Natural Selection, Mutations, and Genetic Drift Since these populations are isolated, they are evolving separately, and slowly becoming different enough to be considered a separate species. Allopatric Speciation Allo = “other” -patric = “country” Allopatric speciation: the formation of new species from geographically isolated populations A population gets separated and evolves to different environments. Sympatric Speciation Sympatric speciation: the formation of new species in the absence of geographic isolation sym = “together” patric = “country” Members of the same species start to diverge in their predation behavior Like a ‘clique’ these individuals face a reproductive barrier Reproducti ve Barriers Coevolution Coevolution: when the interaction between two species so strongly influences their survival that they have evolved in tandem An adaptation in one species evolves alongside a complementary adaptation in another species. Recap: Buff-tailed sicklebill hummingbirds have a strongly recurved bill that exactly matches the species’ favorite food flower. This is an example of a. coevolution b. speciation c. genetic divergence d. geographic isolation Recap: What is a species? a. a group of individuals who share the same habitat b. a group of similar individuals who live in and interact with a particular geographic area c. a group of populations that interbreed and produce fertile offspring Recap: Which of the following can create reproductive isolation? a. mating rituals b. rapid and severe changes in geographic features c. gamete incompatibility d. all of the above Recap: Horses and donkeys can reproduce and have viable offspring, a mule. Mules are not fertile and cannot reproduce. Why are they considered different species? a. They actually are the same species b. In order to be a different species, they must produce viable offspring, and a mule is sterile c. They are different species because they have different adaptations d. They are different species because they live separately