Exam 2 Bio 1202

Chapter 25: Characteristics of Early Earth

• Formation of Earth

  • Earth's formation took place approximately 4.6 billion years ago.

  • Early Earth experienced heavy bombardment by rocks, which vaporized water, delaying the formation of seas until around 4 billion years ago.

• Early Atmosphere

  • The atmosphere at the time contained little oxygen and included

    • Water vapor

    • Volcanic gases such as nitrogen, carbon dioxide, methane, ammonia, and hydrogen.

• Origin of Simple Cells

  • Hypothesized chemical and physical processes may have produced simple cells through a sequence of stages:

    1. Abiotic synthesis of small organic molecules.

    2. Joining of these small molecules into macromolecules.

    3. Packaging of molecules into protocells.

    4. Development of self-replicating molecules.

• Key Figures and Experiments

  • Oparin & Haldane (1920s): Proposed the early atmosphere was a reducing environment.

  • Miller & Urey (1953): Conducted experiments demonstrating the abiotic synthesis of organic molecules in a reducing atmosphere.

• Meteorites

  • A significant source of organic molecules, notably the Murchison meteorite:

    • Weighed over 100 kg and contained 80+ amino acids, along with lipids, simple sugars, and nitrogenous bases.

    • Fell in Victoria, Australia in 1969 and was a documented event.

Geologic Record

• 5 Mass Extinctions

  1. Hadean Eon (4.6-4.0 BYA)

     • Formation of Earth

     • Intense meteorite bombardment

     • Formation of Earth's crust and early oceans

     • Minimal evidence of life; origin of simple organic molecules.

  2. Archaean Eon (4.0-2.5 BYA)

     • Formation of the first solid continents

     • Emergence of prokaryotic microbes (bacteria and archaea)

     • Photosynthesis by cyanobacteria released oxygen.

  3. Proterozoic Eon (2.5 billion-541 million years ago)

     • The Great Oxygenation Event resulted in significant oxygen buildup.

     • Appearance of eukaryotes, simple algae, and soft-bodied organisms.

  4. Phanerozoic Eon (541 MYA-present)

     • The Cambrian Explosion marked rapid diversification of life.

     • Development of hard-shelled organisms, complex plants, and animals.

     • Evolution of fish, insects, reptiles, mammals, and flowering plants.

     • Multiple mass extinctions, including the one that ended the dinosaurs.

     • Rise of humans in the Holocene epoch.

Chapter 26: Taxonomic Groups

• Hierarchy of Taxonomic Groups

  • Ranges from broad to narrow:

    • Domain

    • Kingdom

    • Phylum

    • Class

    • Order

    • Family

    • Genus

    • Species

• Maximum Parsimony and Maximum Likelihood

  • Maximum Parsimony: Posits that the simplest tree requiring the fewest evolutionary events is likely the true phylogeny.

  • Maximum Likelihood: Uses probability rules regarding DNA changes over time, inferring the evolutionary tree that reflects the most probable sequence of events.

• Orthologous vs. Paralogous Genes

  • Orthologous Genes:

    • Found as a single copy in the genome and homologous across species, diverging post-speciation.

  • Paralogous Genes:

    • Result from gene duplication, found in multiple copies within the genome, diverging within the species.

• Horizontal Gene Transfer

  • Concept triggering major genetic changes between organisms.

• Pardomorphosis

  • Refers to accelerated reproductive development compared to somatic development, where sexually mature species retain juvenile features.

Chapter 27: Bacterial Classification

• Classification Criteria

  • Shape

    • Cocci: Round shape

    • Bacilli: Rod shape

    • Spirilli: Spiral shape

  • Reproduction

    • Asexual reproduction via binary fission.

    • Genetic exchange through conjugation, transformation, and transduction.

  • Nutrition

    • Autotrophs: Produce their food (e.g., cyanobacteria via photosynthesis).

    • Heterotrophs: Consume organic material.

    • Chemotrophs: Obtain energy from inorganic compounds.

  • Oxygen Requirements

    • Obligate aerobes: Require oxygen.

    • Obligate anaerobes: Cannot survive in the presence of oxygen.

    • Facultative anaerobes: Can survive with or without oxygen.

• Gram Staining:

  • A classification method for bacteria:

    • Gram-positive: Thick peptidoglycan walls (stains purple).

    • Gram-negative: Thinner peptidoglycan and an outer membrane (stains pink).

Reproductive Processes

• Reproductive Methods

  • Binary Fission: A fast, asexual process resulting in clones; occurs every 1-3 hours under optimal conditions.

  • Conjugation: DNA transfer between bacteria through a pilus.

  • Transformation: Uptake of DNA from the environment.

  • Transduction: DNA transfer between bacteria via a virus.

• Mutation Rates

  • Low mutation rates can lead to rapid accumulation of mutations due to shorter generation times and large populations.

Plasmids and their Role in Bacterial Evolution

• Plasmids: Small, independently replicating DNA rings; often carry genes for antibiotic resistance, important for bacterial evolution.

Bacteria in Research and Technology

• Applications:

  • Used in bioremediation to remove pollutants from environments.

  • Experiments utilizing prokaryotes have advanced DNA technology.

  • Bacteria can aid in producing natural plastics.

Endospores and Structure

• Endospores: Tough, metabolically inactive spores that can survive extreme conditions for centuries.

• Fimbriae: Hair-like appendages allowing prokaryotes to adhere to substrates or other individuals.

• Pili: Longer appendages that facilitate DNA exchange between bacteria, particularly during conjugation.

Interactions and Ecological Relationships

• Symbiosis: Close ecological interactions between two species, typically including a larger host and a smaller symbiont.

  1. Mutualism: Both organisms benefit.

  2. Commensalism: One benefits without harming or helping the other significantly.

  3. Parasitism: One organism (the parasite) harms the host.

• Pathogens: Bacteria responsible for many diseases in humans.

  • Exotoxins: Secreted toxins affecting hosts even without the bacterial presence.

  • Endotoxins: Released only upon bacterial death, leading to disease symptoms.

Chapter 28: Protists

• Nutritional Diversity:

  • Protists exhibit both sexual and asexual reproduction.

  • Photoautotrophs: Contain chloroplasts.

  • Heterotrophs: Absorb organic molecules.

  • Mixotrophs: Combine traits from both nutritional modes.

Four Supergroups of Eukaryotes

1. Excavata: Unique cytoskeleton with feeding grooves.

   • Diplomonads: Reduced mitochondria, anaerobic pathways, two identical nuclei, multiple flagella.

   • Parabasalids: Mitochondrial remnants (hydrogenosomes), energy via anaerobic biochemistry.

   • Euglenozoans: Diverse clade with predatory and photosynthetic species, distinguished by spiral flagellar rods.

2. SAR:

• Stramenopiles: Photosynthetic organisms with dual flagella; includes diatoms and brown algae.

• Alveolates: Membrane-enclosed sacs (alveoli) under plasma membranes; includes dinoflagellates, apicomplexans, ciliates.

• Rhizarians: Includes amoebas; distinguishes themselves with threadlike pseudopodia.

3. Archaeplastida: Comprises red algae, green algae, and plants.

   • Red Algae: Multicellular, reddish due to phycoerythrin.

   • Green Algae: Closely related to land plants; include charophytes and chlorophytes.

4. Unikonta: Animals, fungi, and some plants.

   • Amoebozoans: Have lobe- or tube-shaped pseudopodia; includes slime molds and entamoebas.

Endosymbiosis

• Endosymbiotic Theory:

  • Proposes that mitochondria and plastids originated from engulfed prokaryotes by early eukaryotic ancestors, aligning mitochondria with alpha proteobacteria and plastids with photosynthetic cyanobacteria.

Chapter 31: Ecological Success of Fungi

• Fungi Roles:

  • Decomposers: Break down nonliving organic material for nutrient absorption.

  • Parasitic: Absorb nutrients from living hosts.

  • Mutualistic: Benefit host plants; mycorrhizae enhance nutrient absorption.

• Body Structures:

  • Common structures include multicellular filaments and single-celled yeasts.

  • Fungi develop hyphae networks for nutrient absorption, reinforced by chitin.

Reproductive Structures and Processes

• Hyphal Networks:

  • Form extensive mycelium enhancing feeding efficiency.

• Plasmogamy and Karyogamy:

  • Plasmogamy: Fusion of cytoplasm from different mycelia.

  • Karyogamy: Fusion of nuclei produces diploid cells, enabling genetic variation.

Major Groups of Fungi

• Recognized phyla:

  1. Chytrids

  2. Zygomycetes

  3. Glomeromycetes

  4. Ascomycetes

  5. Basidiomycetes

• Lichens: A symbiotic relationship between fungi and photosynthetic microorganisms (green algae or cyanobacteria).

• Ergotism: A fungal infection noted for dramatic symptoms linked to historical events.

• Fungal Infections: General term is mycosis, including common ailments like ringworm and athlete's foot.

• Practical Uses:

  • Fungi hold importance in antibiotic production and cancer research.