Biology: Diversity of Living Things — Study Outline

Fundamentals of Biodiversity

Defining Biodiversity and Its Levels

Biodiversity refers to the variety of life forms within a given ecosystem, biome, or the entire planet. It is commonly described at three primary levels:

• Genetic Diversity: The variation of genes within a species. This includes differences among individuals in a population or between populations of the same species.

• Species Diversity: The variety of species within a habitat or a region.

• Ecosystem Diversity: The diversity of ecosystems, natural communities, and habitats within a particular area.

Importance of Genetic Variation: Genetic variation within a species is crucial for adaptation and survival, as it enables populations to withstand environmental changes and resist diseases.

• Example: The genetic diversity in crops like rice or wheat helps ensure food security by providing resistance to pests and diseases.

Taxonomy and the Classification of Life

Taxonomic Hierarchy

Taxonomy is the science of naming, describing, and classifying organisms. The biological ranking system, or taxonomic hierarchy, organizes living things into nested groups based on shared characteristics.

• Hierarchy (from broadest to most specific): Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.

Scientific Naming (Binomial Nomenclature)

• Rules: Each species is given a two-part Latin name: the Genus (capitalized) and the species (lowercase), both italicized (e.g., Homo sapiens).

• Formatting: The genus name is always capitalized; the species name is not.

Classification and Relatedness

• Classification helps determine evolutionary relationships; organisms sharing more taxonomic levels are more closely related.

• Example: Humans (Homo sapiens) and chimpanzees (Pan troglodytes) share the same family (Hominidae), indicating close evolutionary ties.

Diversity of Microorganisms (Viruses and Prokaryotes)

Extremophiles

Some microorganisms, especially certain prokaryotes, thrive in extreme environments (e.g., high temperature, salinity, acidity).

• Example: Thermophiles live in hot springs; halophiles in salty lakes.

Viruses: Structure and Reproduction

• General Structure: Viruses consist of genetic material (DNA or RNA) enclosed in a protein coat (capsid); some have an additional lipid envelope.

• Stages of Viral Reproduction:

  1. Attachment

  2. Entry

  3. Replication and synthesis

  4. Assembly

  5. Release

Bacteria: Structure, Shapes, and Cell Walls

• Shapes: Cocci (spherical), bacilli (rod-shaped), spirilla (spiral).

• Cell Wall Variations: Gram-positive (thick peptidoglycan layer) and Gram-negative (thin peptidoglycan layer plus outer membrane).

Bacterial Reproduction and Genetics

• Reproduction: Most bacteria reproduce asexually by binary fission.

• Oxygen Requirements: Obligate aerobes (require oxygen), obligate anaerobes (cannot tolerate oxygen), facultative anaerobes (can survive with or without oxygen).

• Genetic Exchange: Bacteria exchange genetic material via transformation, transduction, and conjugation.

Ecological Interactions

Symbiotic Relationships

Symbiosis refers to close and long-term biological interactions between two different biological organisms.

• Mutualism: Both species benefit (e.g., bees and flowering plants).

• Commensalism: One species benefits, the other is unaffected (e.g., barnacles on whales).

• Parasitism: One species benefits at the expense of the other (e.g., tapeworms in mammals).

The Eukaryotic Kingdoms

Distinguishing Eukaryotic Kingdoms

Eukaryotes are classified into several kingdoms based on cell structure, mode of nutrition, and other features.

• Kingdom Plantae: Multicellular, photosynthetic, cell walls of cellulose.

• Kingdom Fungi: Mostly multicellular, absorptive heterotrophs, cell walls of chitin.

• Kingdom Animalia: Multicellular, ingestive heterotrophs, no cell walls.

• Kingdom Protista: Mostly unicellular, diverse modes of nutrition and cell structure.

Classification of Single-Celled Eukaryotes

• Single-celled eukaryotes (protists) are classified based on cellular structures (e.g., presence of cilia, flagella) and how they obtain energy (autotrophic or heterotrophic).

• Example: Amoeba moves using pseudopodia; Euglena is photosynthetic and moves with a flagellum.

Evolution and Phylogenetics

Phylogenetic Trees

Phylogenetic trees (evolutionary trees) are diagrams that depict the evolutionary relationships among various biological species based on similarities and differences in genetic or physical traits.

• Reading Trees: Branch points (nodes) represent common ancestors; the closer two species are on the tree, the more recently they shared a common ancestor.

• Clade: A group consisting of an ancestor and all its descendants.

Tracking Evolutionary Relationships

• To find common ancestors, trace back from two species to their most recent shared node.

• Example: Birds and crocodiles share a more recent common ancestor with each other than with mammals.

Symbiotic Relationship	Effect on Species 1	Effect on Species 2	Example
Mutualism	Benefit	Benefit	Bees and flowers
Commensalism	Benefit	No effect	Barnacles on whales
Parasitism	Benefit	Harmed	Tapeworms in mammals

Additional info: Academic context and examples have been added to expand on the outline points and ensure the notes are self-contained for study purposes.