General Biology Study Guide: Bacteria, Archaea, Protists, and Plant Diversity

Chapter 27: Bacteria and Archaea

Differences Between Bacteria, Archaea, and Eukarya

Bacteria, Archaea, and Eukarya represent the three domains of life, each with distinct evolutionary relationships and cellular characteristics.

• Bacteria: Prokaryotic cells with peptidoglycan cell walls, diverse metabolic pathways, and found in many environments.

• Archaea: Prokaryotic cells lacking peptidoglycan, often found in extreme environments, unique membrane lipids.

• Eukarya: Eukaryotic cells with membrane-bound organelles, includes plants, animals, fungi, and protists.

• Evolutionary Relationships: Archaea are more closely related to Eukarya than to Bacteria.

Ecological Roles of Prokaryotes

Prokaryotes play essential roles in ecosystems as decomposers, producers, nitrogen fixers, and pathogens.

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

• Producers: Cyanobacteria perform photosynthesis, producing oxygen and organic compounds.

• Nitrogen Fixers: Convert atmospheric nitrogen into forms usable by plants.

• Pathogens: Cause diseases in plants, animals, and humans.

• Cyanobacteria: Only prokaryotes to evolve oxygenic photosynthesis, crucial for Earth's oxygen atmosphere.

Prokaryotic Gene Transfer

Horizontal gene transfer is the movement of genetic material between organisms, not by descent.

• Mechanisms: Transformation, transduction, and conjugation.

• Importance: Increases genetic diversity and adaptation in prokaryotes.

Prokaryotic Nutrition

Prokaryotes exhibit diverse nutritional modes, classified by energy and carbon sources.

• Photoautotrophs: Use light energy and CO2 as carbon source.

• Chemoautotrophs: Use inorganic chemicals for energy and CO2 for carbon.

• Photoheterotrophs: Use light for energy, organic compounds for carbon.

• Chemoheterotrophs: Use organic compounds for both energy and carbon.

Key Terms in Prokaryote Biology

Understanding terminology is essential for studying prokaryotes.

• Halophile: Organism that thrives in high-salt environments.

• Extremophile: Organism adapted to extreme conditions (temperature, pH, salinity).

• Methanogen: Archaea that produce methane as a metabolic byproduct.

• Decomposer: Organism that breaks down dead material.

• Nitrogen Fixation: Conversion of atmospheric nitrogen to ammonia.

• Conjugation: Direct transfer of DNA between bacteria.

• Mutualism: Symbiotic relationship where both organisms benefit.

• Commensalism: One organism benefits, the other is unaffected.

• Parasitism: One organism benefits at the expense of another.

Chapter 28: Protists

Characteristics of Protists

Protists are a diverse group of mostly unicellular eukaryotes, exhibiting varied forms and functions.

• Unicellular or multicellular (e.g., algae).

• Habitat: Aquatic or moist environments.

• Nutrition: Photoautotrophic, heterotrophic, or mixotrophic.

Protist Evolution and Relationships

Protists show evolutionary relationships with plants, animals, and fungi, and are classified as a paraphyletic group.

• Paraphyletic Group: Includes some but not all descendants of a common ancestor.

• Comparison: Protists differ from plants (lack true roots, stems, leaves), animals (lack tissues), and fungi (lack chitin cell walls).

Endosymbiosis and Organelle Evolution

The endosymbiotic theory explains the origin of mitochondria and chloroplasts in eukaryotes.

• Primary Endosymbiosis: Eukaryote engulfs a prokaryote (e.g., mitochondria from alpha-proteobacteria).

• Secondary Endosymbiosis: Eukaryote engulfs another eukaryote (e.g., chloroplasts in some algae).

• Life Cycles: Protists exhibit diverse life cycles, including asexual and sexual reproduction.

Classification of Protists

Protists are classified by ecological roles, habitat, and motility.

• Major Groups: Excavata, Stramenopiles, Alveolata, Rhizaria, Archaeplastida, Amoebozoa, Opisthokonta.

• Motility: Flagella, cilia, pseudopodia.

Protist Traits and Terminology

Protists display a wide range of traits and reproductive strategies.

• Brown Algae, Diatoms, Dinoflagellates: Examples of photosynthetic protists.

• Key Terms: Primary endosymbiosis, secondary endosymbiosis, mitochondria, plastid, mitosis, meiosis, haploid, diploid, gametophyte, sporophyte, spore, flagella, cilia.

Chapter 29: Plant Diversity I – How Plants Colonized Land

Derived Characteristics of Land Plants

Land plants evolved unique features to survive on land, distinguishing them from their algal relatives.

• Multicellular dependent embryo (embryophytes).

• Walled spores produced in sporangia.

• Multicellular gametangia (structures for gamete production).

• Apical meristems: Regions of cell division at tips of roots and shoots.

Adaptations to Terrestrial Life

Plants developed adaptations for terrestrial environments, such as cuticles and vascular tissues.

• Cuticle: Waxy layer preventing water loss.

• Stomata: Pores for gas exchange.

• Vascular tissue: Xylem and phloem for transport.

• Support structures: Lignin for rigidity.

Alternation of Generations

Land plants exhibit alternation of generations, a life cycle with multicellular haploid and diploid stages.

• Sporophyte: Diploid, produces spores by meiosis.

• Gametophyte: Haploid, produces gametes by mitosis.

Formula:

• $2n \xrightarrow{meiosis} n \xrightarrow{fertilization} 2n$

Bryophytes and Seedless Vascular Plants

Bryophytes (mosses, liverworts, hornworts) and seedless vascular plants (ferns, lycophytes) represent early land plant lineages.

• Bryophytes: Nonvascular, dominant gametophyte generation.

• Seedless Vascular Plants: Vascular tissue, dominant sporophyte generation.

Key Terms in Plant Diversity

• Microphyll, megaphyll: Types of leaves.

• Sporophyte, gametophyte, spore, gamete, sporangia, gametangia, xylem, phloem, lignin, roots, rhizoids, vascular tissue, cuticle, stomata, bryophyte, lycophyte, monilophyte, archegonia, antheridia.

Chapter 30: Plant Diversity II – The Evolution of Seed Plants

Sporophyte vs. Gametophyte Generation

Seed plants show a dominant sporophyte generation, with reduced gametophytes protected within tissues.

• Nonvascular plants: Dominant gametophyte.

• Seed plants: Dominant sporophyte, gametophyte reduced and dependent.

Seed Plant Adaptations

Seeds and pollen allow plants to reproduce without water and colonize dry environments.

• Seed: Embryo, food supply, and protective coat.

• Pollen: Delivers sperm to egg without water.

Angiosperms and Gymnosperms

Seed plants are divided into gymnosperms (naked seeds) and angiosperms (flowering plants with enclosed seeds).

• Gymnosperms: Conifers, cycads, ginkgo.

• Angiosperms: Flowering plants, fruits, double fertilization.

Plant Life Cycles and Reproduction

Seed plants have complex life cycles involving pollination, fertilization, and seed development.

• Pollination: Transfer of pollen to ovule.

• Double fertilization: Unique to angiosperms; one sperm fertilizes egg, another forms endosperm.

Key Terms in Seed Plant Evolution

• Ovule, pollen, fruit, endosperm, double fertilization, secondary metabolite, conifer, heterospory, homospory.

Table: Comparison of Plant Groups

Group	Vascular Tissue	Dominant Generation	Seeds	Flowers
Bryophytes	No	Gametophyte	No	No
Seedless Vascular Plants	Yes	Sporophyte	No	No
Gymnosperms	Yes	Sporophyte	Yes	No
Angiosperms	Yes	Sporophyte	Yes	Yes