Unit 2 The Living World Biodiversity Ap Exam Review

Unit 2: The Living World & Biodiversity - AP Exam Review

This comprehensive guide provides a thorough review of Unit 2: The Living World and Biodiversity for the AP Biology exam. We will delve into the key concepts, essential vocabulary, and likely exam question types to ensure you're fully prepared. This guide emphasizes understanding the interconnectedness of concepts, making it easier to navigate the complexities of this unit.

I. What is Biodiversity? Understanding the Scope

Biodiversity, short for biological diversity, encompasses the variety of life at all levels of biological organization. This includes:

• Genetic diversity: The variations in genes within a species. This fuels adaptation and evolution. Think about the differences in dog breeds – all Canis familiaris, but with vast genetic differences resulting in diverse phenotypes.
• Species diversity: The number and abundance of different species in a particular area. A rainforest boasts much higher species diversity than a desert.
• Ecosystem diversity: The variety of habitats, communities, and ecological processes within and between ecosystems. This includes the interactions between different species and their environment.

Measuring Biodiversity: Key Indices

Several indices help quantify biodiversity. Understanding these is crucial for the AP exam.

• Species richness: Simply the number of species present in a given area. Higher richness generally indicates higher biodiversity, but doesn't account for abundance.
• Species evenness: The relative abundance of each species. A community with even species evenness has similar numbers of each species, while unevenness indicates dominance by a few species.
• Shannon Diversity Index: A more sophisticated measure combining richness and evenness, providing a more accurate representation of biodiversity than richness alone. It's a commonly used metric in ecological studies and may appear in AP exam questions.

II. Phylogenetic Trees and Evolutionary Relationships

Understanding phylogenetic trees (also called cladograms) is fundamental to this unit. These diagrams represent the evolutionary relationships among organisms.

Interpreting Phylogenetic Trees: Key Features

• Branches: Represent evolutionary lineages.
• Nodes: Represent common ancestors where lineages diverge.
• Root: Represents the most recent common ancestor of all organisms on the tree.
• Clades: Groups of organisms that share a common ancestor. Identifying clades is critical for understanding evolutionary relationships.
• Outgroups: Organisms used for comparison to determine which traits are ancestral and which are derived.

Phylogenetic Tree Construction Methods

Phylogenetic trees are constructed using various methods, including:

• Morphological data: Comparing physical characteristics (anatomy, morphology).
• Molecular data: Comparing DNA, RNA, or protein sequences. Molecular data is generally considered more reliable for constructing accurate phylogenetic trees due to its quantifiable nature.

Phylogenetic Trees and Classification: Taxonomy

Taxonomy is the science of classifying organisms. Phylogenetic trees inform modern taxonomic classification systems, aiming to reflect evolutionary relationships. The hierarchical system (Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species) is a key concept to master.

III. Three Domains of Life

The current system of classification recognizes three domains: Bacteria, Archaea, and Eukarya.

Bacteria

• Prokaryotic: Lacking membrane-bound organelles and a nucleus.
• Diverse metabolisms: Including autotrophs (producing their own food) and heterotrophs (consuming other organisms).
• Importance: Crucial roles in nutrient cycling, decomposition, and some are pathogenic (disease-causing).

Archaea

• Prokaryotic: Like bacteria.
• Extremophiles: Many thrive in extreme environments (high temperatures, salinity, acidity).
• Unique cell walls: Distinct from bacterial cell walls in composition.
• Metabolic diversity: Similar to bacteria, demonstrating a wide range of metabolic capabilities.

Eukarya

• Eukaryotic: Possessing membrane-bound organelles and a nucleus.
• Four Kingdoms: Protista, Fungi, Plantae, and Animalia (though this classification is constantly evolving and debated).
  • Protista: A diverse group of mostly unicellular organisms.
  • Fungi: Heterotrophic organisms that obtain nutrients by absorption.
  • Plantae: Autotrophic organisms that perform photosynthesis.
  • Animalia: Heterotrophic multicellular organisms.

IV. Evolutionary Processes Driving Biodiversity

Several evolutionary processes contribute to biodiversity:

Natural Selection

• Differential reproductive success: Organisms with advantageous traits are more likely to survive and reproduce, passing those traits to their offspring.
• Adaptation: The process by which organisms become better suited to their environment.
• Fitness: A measure of an organism's reproductive success.

Genetic Drift

• Random changes in allele frequencies: Especially impactful in small populations.
• Bottleneck effect: A drastic reduction in population size leading to reduced genetic diversity.
• Founder effect: A small group establishes a new population, carrying only a subset of the original population's genetic variation.

Gene Flow

• Movement of alleles between populations: Can increase genetic diversity within a population but reduce differences between populations.

Mutation

• Changes in DNA sequence: The ultimate source of new genetic variation. Mutations can be beneficial, harmful, or neutral.

Speciation: Formation of New Species

Speciation is the process by which one species splits into two or more distinct species. Key mechanisms include:

• Allopatric speciation: Geographic isolation leads to reproductive isolation and the evolution of distinct species.
• Sympatric speciation: Speciation occurs within the same geographic area, often driven by mechanisms like polyploidy (changes in chromosome number) or sexual selection.

V. Threats to Biodiversity: Conservation Biology

Human activities significantly impact biodiversity. Understanding these threats is critical for conservation efforts.

Habitat Loss and Fragmentation

• Deforestation, urbanization, agriculture: Destroy habitats and reduce the available space for organisms.
• Fragmentation: Breaks up continuous habitats into smaller, isolated patches, reducing genetic diversity and increasing vulnerability to extinction.

Invasive Species

• Non-native species: Outcompete native species for resources, disrupt ecosystems, and can introduce diseases.

Overexploitation

• Overfishing, poaching, unsustainable harvesting: Reduce populations to unsustainable levels, threatening species with extinction.

Pollution

• Air, water, and soil pollution: Harms organisms directly and indirectly through habitat degradation.

Climate Change

• Altering habitats, disrupting ecosystems, and shifting species ranges: A significant and growing threat to global biodiversity.

VI. Conservation Strategies

Effective conservation strategies are crucial for mitigating biodiversity loss.

Protected Areas

• National parks, wildlife reserves: Provide safe havens for endangered species and maintain ecosystem integrity.

Habitat Restoration

• Reforestation, wetland restoration: Rehabilitating degraded habitats to support biodiversity.

Sustainable Practices

• Sustainable agriculture, forestry, and fishing: Minimizing environmental impact and promoting long-term resource availability.

Captive Breeding Programs

• Breeding endangered species in captivity: Maintaining genetic diversity and potentially reintroducing them into the wild.

Legislation and Policy

• International treaties, national laws: Protecting endangered species and regulating activities that harm biodiversity.

VII. Preparing for the AP Exam: Strategies and Practice

The AP Biology exam assesses your understanding of these concepts through multiple-choice questions and free-response questions (FRQs). Preparation should include:

• Reviewing key terms and definitions: Mastering the vocabulary is essential for understanding the concepts.
• Practicing multiple-choice questions: Familiarize yourself with the question format and identify areas where you need further study.
• Working through free-response questions: Develop your ability to synthesize information and answer complex questions in a concise and organized manner.
• Understanding the interconnectedness of concepts: Don't learn the topics in isolation; understand how they relate to each other.
• Using diagrams and visuals: Phylogeny trees, food webs, and other diagrams are often used in the exam. Practice interpreting and constructing them.
• Seeking feedback on practice questions and essays: Identifying weak areas early on allows for focused revision and improvement.

This comprehensive review covers the major themes of Unit 2. Remember to consult your textbook, class notes, and other resources to reinforce your understanding and address any remaining questions. Good luck with your AP Biology exam preparation!