Unit 8 Biodiversity Full Study Guide with Goals + Answers

Unit 8: Biodiversity Full Study Guide with Goals + Answers Section I: Vocabulary 1–15. Define 15 vocabulary terms Goal: Know and explain key terms related to biodiversity, evolution, and classification. Examples: ● Cladistics – A classification method based on evolutionary ancestry using shared derived characteristics. ● Speciation – The formation of new species due to genetic divergence. ● Gene Pool – The total set of different genes and alleles in an interbreeding population. ● Polyploidy – A condition in which an organism has more than two complete sets of chromosomes, leading to reproductive isolation. ● Hardy-Weinberg Equilibrium – A principle that states allele frequencies remain constant if no evolutionary forces act upon them. (Define at least 15 total) ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ Clade – A group of organisms that includes a common ancestor and all its descendants. ​ ● Section II: Diagrams and Charts 16. Cladogram Labeling Goal: Show understanding of evolutionary relationships through tree diagrams. Answer Guide: ● b. Node for A & B: Circle the split point that leads to both species A and B. ● c. Terminal branch: Circle one endpoint (e.g., species A). ● d. Time arrow: Add an arrow pointing from root to tips (past → present). ● e. Two clades: Box any groups that include an ancestor and all its descendants. ● f. Species placement: ​ ​ ​ ​ ​ Shark: Place lower/earlier on the tree. ○ Cat and Human: Closer together, higher up (more recent common ancestor). ​ ​ ​ ○ ​ ​ ​ ​ ​ ​ ​ a. Root: Label the base of the cladogram (common ancestor). ​ ● 17. Types of Natural Selection Goal: Distinguish between the three main types of selection and recognize their effect on traits. Answer: Stabilizing selection: Favors average traits (e.g., human birth weight); narrows trait distribution. ● Directional selection: Favors one extreme (e.g., antibiotic resistance in bacteria); curve shifts. ● Disruptive selection: Favors both extremes over the average (e.g., light and dark mice on mixed terrain); curve splits. ​ ​ ​ ​ ​ ​ ● Section III: Concepts and Processes 18. Why classify organisms? Goal: Explain the usefulness and limitations of classifying living things. ​ Answer: Classification helps organize species for easier study, naming, and communication. However, traditional taxonomy doesn’t always reflect evolutionary relationships and can be arbitrary due to convergent evolution and morphological similarities that don’t reflect ancestry. 19. Reclassification into three domains Goal: Understand how rRNA sequencing led to modern domains: Bacteria, Archaea, and Eukarya. ​ Answer: Molecular evidence from rRNA sequences showed deep differences between bacteria-like organisms. As a result, prokaryotes were split into two domains (Bacteria and Archaea), with Eukarya as the third. 20. Molecular clock Goal: Know how DNA/protein changes help estimate divergence time between species. ​ Answer: A molecular clock uses the rate of genetic mutations to estimate how long ago two species diverged. Assumes mutations accumulate at a roughly constant rate, but accuracy is affected by population size, generation time, and selective pressure. 21. Clades vs. Traditional Classification Goal: Compare evolutionary (cladistic) classification with older systems. ​ Answer: Cladistics groups organisms by common ancestry, reflecting true evolutionary history. Traditional methods often use arbitrary ranks and ignore evolutionary links. Clades predict characteristics and relationships more accurately. 22. Cladistics Case Study (Raccoon or Horseshoe Crab) Goal: Explain a reclassification using DNA evidence. ​ Answer: The raccoon was originally grouped with bears, but DNA sequencing showed it’s more closely related to weasels. This led to its reclassification, showing how molecular data can correct old assumptions based on appearance. 23. Limits of the Biological Species Concept Goal: Explain why some organisms don't fit this definition. ​ Answer: The concept requires interbreeding and fertile offspring, which doesn’t apply to asexual organisms (e.g., bacteria) or those that exchange genes horizontally, making species boundaries unclear. 24. Hybrid Sterility Example Goal: Explain why hybrids are sterile. ​ Answer: Species with different chromosome numbers produce sterile offspring (e.g., a mule) because their chromosomes can’t pair during meiosis, resulting in unviable gametes. 25. Allopatric vs. Sympatric Speciation Goal: Compare the two major forms of speciation. Answer: ● Sympatric: Occurs in the same area due to behavioral or genetic changes. ​ ​ ​ Allopatric: Occurs when a population is physically separated (e.g., islands). ​ ●