General Biology Study Guide: Bacteria, Archaea, Protists, Fungi, and Animal Diversity

Chapter 27: Bacteria and Archaea

Cell Wall Traits and Types

Bacteria and Archaea are prokaryotic microorganisms with distinct cell wall structures that are critical for their survival and classification.

• Bacterial Cell Wall: Composed primarily of peptidoglycan, which provides structural support and shape.

• Archaean Cell Wall: Lacks peptidoglycan; instead, contains pseudopeptidoglycan or other unique polymers.

• Gram-Positive vs. Gram-Negative Bacteria: Gram-positive bacteria have thick peptidoglycan layers; Gram-negative bacteria have a thin peptidoglycan layer and an outer membrane.

Metabolic Diversity

Bacteria and Archaea exhibit a wide range of metabolic strategies, allowing them to inhabit diverse environments.

• Photoautotrophs: Use light as an energy source and CO2 as a carbon source (e.g., cyanobacteria).

• Chemoautotrophs: Obtain energy from inorganic chemicals and use CO2 as a carbon source (e.g., some Archaea).

• Photoheterotrophs: Use light for energy but require organic compounds for carbon.

• Chemoheterotrophs: Obtain both energy and carbon from organic compounds (e.g., most bacteria).

Oxygen Relationships

• Obligate Aerobes: Require oxygen for survival.

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

• Facultative Anaerobes: Can survive with or without oxygen.

Structural Features

• Plasmids: Small, circular DNA molecules independent of the chromosomal DNA; often carry genes for antibiotic resistance.

• Surface Structures: Capsules, pili, endospores, flagella, and fimbriae aid in protection, attachment, and motility.

Genetic Exchange and Adaptation

• Transformation: Uptake of naked DNA from the environment.

• Transduction: Transfer of DNA by bacteriophages (viruses that infect bacteria).

• Conjugation: Direct transfer of DNA between bacteria via a pilus.

Antibiotic Resistance and Pathogenicity

• Antibiotic Resistance: The ability of bacteria to survive and multiply despite the presence of antibiotics, often due to genes carried on plasmids.

• Opportunistic Pathogens: Microorganisms that cause disease primarily in hosts with weakened immune systems.

Table: Comparison of Bacteria and Archaea

Feature	Bacteria	Archaea
Cell Wall	Peptidoglycan	No peptidoglycan; various polymers
Membrane Lipids	Ester-linked	Ether-linked
RNA Polymerase	One type	Several types, more similar to eukaryotes
Habitat	Ubiquitous	Often extreme environments

Chapter 28: Protists

Definition and Diversity

Protists are a diverse group of mostly unicellular eukaryotic organisms that do not fit into the other eukaryotic kingdoms (plants, animals, fungi).

• Examples: Amoebas, algae, paramecia, diatoms, dinoflagellates, euglenids.

• Habitats: Aquatic and moist terrestrial environments.

Classification and Nutrition

• Autotrophic Protists: Photosynthetic (e.g., algae, diatoms).

• Heterotrophic Protists: Ingest or absorb organic material (e.g., amoebas, ciliates).

• Mixotrophs: Can switch between autotrophy and heterotrophy (e.g., Euglena).

Ecological Roles and Impact

• Primary Producers: Many protists form the base of aquatic food webs.

• Pathogens: Some cause diseases in humans, animals, or plants (e.g., Plasmodium causes malaria).

• Influence on Climate: Diatoms and other phytoplankton play a role in carbon cycling and climate regulation.

Table: Major Protist Groups and Features

Group	Key Features	Examples
Diplomonads	Two nuclei, multiple flagella	Giardia
Dinoflagellates	Cellulose plates, two flagella	Red tide organisms
Diatoms	Silica cell walls	Phytoplankton
Euglenids	Flexible pellicle, mixotrophic	Euglena

Chapter 31: Fungi

Fungal Structure and Life Cycles

Fungi are eukaryotic organisms that absorb nutrients from their environment and have unique structural and reproductive features.

• Hyphae: Thread-like filaments forming the mycelium, the main body of a fungus.

• Mycelium: A network of hyphae that increases surface area for absorption.

• Cell Walls: Composed of chitin, not cellulose.

• Life Cycles: May include sexual and asexual reproduction; spore formation is common.

Fungal Groups

• Zygomycota: Bread molds; produce zygospores.

• Ascomycota: Sac fungi; produce ascospores in asci (e.g., yeasts, morels).

• Basidiomycota: Club fungi; produce basidiospores (e.g., mushrooms).

• Deuteromycetes: Fungi with no known sexual stage ("imperfect fungi").

• Glomeromycota: Form arbuscular mycorrhizae with plants.

Fungal Ecology and Symbiosis

• Decomposers: Break down dead organic matter, recycling nutrients.

• Mutualists: Form beneficial relationships (e.g., mycorrhizae with plants, lichens with algae/cyanobacteria).

• Pathogens: Cause diseases in plants and animals.

Table: Comparison of Fungi and Plants

Feature	Fungi	Plants
Cell Wall	Chitin	Cellulose
Nutrition	Absorptive heterotroph	Photosynthetic autotroph
Storage Carbohydrate	Glycogen	Starch
Body Structure	Hyphae/mycelium	Tissues/organs

Chapter 32: Introduction to Animal Diversity

Animal Body Plans and Evolution

Animals are multicellular, heterotrophic eukaryotes with diverse body plans and evolutionary histories.

• Cephalization: Development of a head region with sensory organs.

• Symmetry: Bilateral (single plane of symmetry) or radial (multiple planes).

• Germ Layers: Diploblastic (two layers) vs. triploblastic (three layers).

• Body Cavities: Coelomate (true coelom), pseudocoelomate, acoelomate.

Major Animal Phyla and Evolutionary Trends

• Protostomes vs. Deuterostomes: Differ in embryonic development; protostomes develop mouth first, deuterostomes develop anus first.

• Segmentation: Repetition of body segments (e.g., annelids, arthropods).

• Coral Bleaching: Loss of symbiotic algae from corals, often due to environmental stress.

Chapter 33: Invertebrates

Exoskeletons and Segmentation

Invertebrates are animals without a backbone, exhibiting a variety of body plans and adaptations.

• Exoskeleton: External skeleton that provides protection and support (e.g., arthropods).

• Advantages: Protection, prevention of desiccation, muscle attachment.

• Disadvantages: Limits growth (requires molting), can be heavy.

• Segmentation: Division of the body into repeated segments, allowing specialization.

Relative Ages of Animal Phyla

• Some phyla (e.g., sponges, cnidarians) are ancient, while others (e.g., arthropods, chordates) appeared more recently in evolutionary history.

Additional info: These notes are based on a list of exam topics and have been expanded with academic context to provide a comprehensive study guide for General Biology students.