Unit 2: Biodiversity – Bacteria, Archaea, Protists, Fungi, and Plants

Chapter 27: Bacteria and Archaea

Gram-Positive vs. Gram-Negative Bacteria

Gram staining differentiates bacteria based on cell wall structure, which affects their physiology and response to antibiotics.

• Gram-Positive: Thick peptidoglycan layer, no outer membrane, stains purple, commonly forms endospores.

• Gram-Negative: Thin peptidoglycan layer, has outer membrane, stains pink/red, rarely forms endospores.

Bacteria vs. Archaea: Prokaryotic Cell Differences

Bacteria and Archaea are both prokaryotes but differ in cell structure and evolutionary lineage.

• Bacteria: Cell wall contains peptidoglycan, ester-linked membrane lipids, unique rRNA, found in diverse environments.

• Archaea: No peptidoglycan, ether-linked membrane lipids, rRNA similar to eukaryotes, often extremophiles.

Bacterial Diversity: Size, Reproduction, and Generation Time

Bacteria's rapid reproduction and large populations drive genetic diversity and adaptability.

• Short generation times and fast reproduction increase mutation rates and genetic variation.

• Natural selection acts quickly, favoring traits for survival in extreme environments.

• Bacteria can form specialized groups adapted to harsh conditions.

Bacterial DNA Exchange: Transformation and Transduction

Bacteria can acquire new genetic material through horizontal gene transfer.

• Transformation: Uptake of naked DNA from the environment.

• Transduction: DNA transfer via bacteriophages (viruses that infect bacteria).

• These processes enable rapid adaptation, such as antibiotic resistance.

Types of Bacteria: Morphological Classification

Bacteria are classified by shape, which influences their ecological roles.

• Cocci: Round, can form chains, clusters, or pairs.

• Bacilli: Rod-shaped, can form chains, clusters, or pairs.

• Spirilla: Rigid spiral, single cells.

• Spirochetes: Flexible spiral, single cells.

• Vibrios: Comma-shaped, single cells.

Ecological Interactions of Prokaryotes

Prokaryotes engage in diverse ecological relationships.

• Symbiosis: Close, long-term interaction between two species.

• Mutualism: Both benefit (e.g., Rhizobium in legumes).

• Commensalism: One benefits, other unaffected (e.g., skin bacteria).

• Parasitism: One benefits, host harmed (e.g., Mycobacterium tuberculosis).

• Pathogens: Disease-causing organisms (e.g., Streptococcus pyogenes).

Impacts of Bacteria on Humans

Bacteria have both beneficial and harmful effects on human health and society.

• Positive: Essential for health (gut flora), industry (fermentation), and environment (decomposition).

• Negative: Some cause diseases and spoilage.

Chapter 28: Protists

Diversity of Protists and Eukaryotes

Most eukaryotes are single-celled protists, which are diverse and abundant across all eukaryotic supergroups.

• Protists are found in nearly every environment, often unseen due to their microscopic size.

Evolutionary Differences Among Protist Supergroups

Protists are classified into four major supergroups based on evolutionary traits.

• Excavata: Feeding groove, modified or absent mitochondria (e.g., Euglena, Giardia).

• SAR: Genetic similarities, includes Stramenopiles, Alveolates, Rhizarians.

• Archaeplastida: Red and green algae, land plants, photosynthetic.

• Unikonta: Amoebozoans and Opisthokonts, single flagellum, includes animals and fungi.

SAR Subclades: Stramenopiles, Alveolates, Rhizarians

The SAR supergroup is divided into three subclades with distinct features.

• Stramenopiles: Hairy flagella, includes algae and molds.

• Alveolates: Membrane-bound alveoli, includes ciliates, dinoflagellates, parasites.

• Rhizarians: Threadlike pseudopodia, often with mineral skeletons.

Unikonta Subclades: Amoebozoans and Opisthokonts

Unikonta includes both single-celled and multicellular organisms.

• Amoebozoans: Move with lobe-shaped pseudopodia, includes amoebas and slime molds.

• Opisthokonts: Posterior flagellum, includes animals, fungi, and related protists.

Protists: Kingdom Status and Origins of Plants, Fungi, Animals

Protists are no longer considered a single kingdom because they are not a natural evolutionary group.

• Plants, fungi, and animals each originate from different protist ancestors within eukaryotic supergroups.

Chapter 31: Fungi

Structure and Function of Fungal Bodies

Fungi have unique structures adapted for nutrient absorption and reproduction.

• Hyphae: Thread-like filaments, main structural unit, high surface area for absorption.

• Mycelium: Mass of hyphae, main feeding structure.

• Cell Walls: Made of chitin, provides strength and protection.

• Septae: Cross-walls dividing hyphae, allow movement of cytoplasm and organelles.

• Fruiting Bodies: Produce and release spores for reproduction.

• Spore-Producing Structures: Specialized cells/structures for spore production and dispersal.

Fungal Evolution and Closest Relatives

Fungi evolved from unicellular, flagellated ancestors within the opisthokont lineage.

• Closest relatives: animals and choanoflagellates.

Phyla of Fungi: Major Differences

Fungi are classified into several phyla based on reproductive and structural traits.

Phylum	Key Features	Examples
Chytrids	Flagellated spores, aquatic	Batrachochytrium
Zygomycetes	Resistant zygosporangia, coenocytic hyphae	Bread molds
Glomeromycetes	Arbuscular mycorrhizae with plants	Plant symbionts
Ascomycetes	Spore in asci, includes yeasts and morels	Saccharomyces, morels
Basidiomycetes	Spore on basidia, includes mushrooms	Mushrooms

Fungal Nutrition: Saprophytic, Parasitic, Mutualistic

Fungi obtain nutrients through different ecological strategies.

• Saprophytic: Decompose dead material.

• Parasitic: Harm living hosts to obtain nutrients.

• Mutualistic: Both partners benefit (e.g., mycorrhizae).

Fungi in Nutrient Cycling, Ecology, and Human Welfare

Fungi play essential roles in ecosystems and human society.

• Recycle nutrients, support plant growth, maintain ecosystem balance.

• Positive impacts: food, medicine, biotechnology.

• Negative impacts: disease, toxins.

Lichens: Symbiotic Associations

Lichens are symbiotic associations between fungi and photosynthetic partners (algae or cyanobacteria).

• Cannot be classified as a single organism; partners from different kingdoms.

Chapter 29: Plant Diversity I – How Plants Colonized Land

Major Developments in Plant Evolution

Plants evolved adaptations for terrestrial life.

• Waxy cuticle and stomata for water retention and gas exchange.

• Vascular tissue for transport and support.

• Lignin for structural strength.

• Seeds and pollen for reproduction without water.

• Flowers and fruits for efficient pollination and seed dispersal.

Origin of Plants: Evidence and Evolutionary Relationships

Plants evolved from green algae, specifically charophytes.

• Evidence: molecular data, cell structure, reproductive similarities, fossils.

Adaptations for Life on Land

Key adaptations enabled plants to colonize terrestrial environments.

• Roots for anchoring and absorbing water/nutrients.

• Lignin in cell walls for strength and support.

• Pollen and seeds for reproduction without water.

• Waxy cuticle covering leaves and stems.

Key Traits Present in Nearly All Plants

Four key traits distinguish land plants from their algal ancestors.

• Alternation of generations.

• Multicellular, dependent embryos.

• Walled spores in sporangia.

• Multicellular gametangia.

Vascular vs. Non-Vascular Plants

Plants are classified based on the presence of vascular tissue.

Type	Key Features	Examples
Vascular	Grow tall, sporophyte dominant, true roots/stems/leaves	Ferns, conifers, flowering plants
Non-Vascular	Low-growing, gametophyte dominant, no true roots/stems/leaves	Mosses, liverworts, hornworts

Bryophytes: Key Features

Bryophytes are extant non-vascular plants with simple structures.

• Non-vascular, small, simple structure.

• Dominant gametophyte generation.

• No true roots, stems, or leaves.

• Depend on water for reproduction.

• Reproduce via spores.

Extant Vascular Plants: Key Features

Vascular plants have adaptations for terrestrial life.

• Vascular tissue (xylem and phloem).

• True roots, stems, and leaves.

• Dominant sporophyte generation.

• Reproduce via spores or seeds.

Chapter 30: Evolution of Seed Plants

Seed Adaptations and Plant Diversification

Seeds enabled plants to diversify and colonize varied environments.

• Protect and nourish embryos.

• Enable wide dispersal.

• Allow dormancy and survival in harsh climates.

• Reduce dependence on water for reproduction.

Gymnosperms vs. Angiosperms

Seed plants are divided into gymnosperms and angiosperms based on reproductive structures.

Type	Key Features	Examples
Gymnosperms	Naked seeds, cones, wind pollination, needle/scale leaves	Pine, spruce, fir
Angiosperms	Seeds in fruit, flowers, diverse pollination, broad leaves	Roses, grasses, oaks

Angiosperm Life Cycle: Major Events

The angiosperm life cycle involves several key stages.

• Flower formation: Sporophyte produces reproductive organs.

• Meiosis: Production of haploid spores/gametophytes.

• Pollination and fertilization: Fusion of gametes.

• Seed and fruit development: Protection and dispersal.

• Germination and growth: New sporophyte generation.

Angiosperm Flower: Parts and Functions

Flowers are specialized structures for reproduction.

• Sepals: Protect the bud.

• Petals: Attract pollinators.

• Stamens: Produce pollen (male).

• Carpels/Pistil: Produce ovules, receive pollen (female).

• Ovule: Develops into seed after fertilization.

Monocots vs. Eudicots: Characteristics and Examples

Angiosperms are classified as monocots or eudicots based on seed leaves and other traits.

Type	Key Features	Examples
Monocot	One seed leaf, parallel veins, flower parts in multiples of 3, scattered vascular bundles, fibrous roots	Grasses, lilies, orchids, palms, onions, bananas
Eudicot	Two seed leaves, net-like veins, flower parts in multiples of 4 or 5, ring-arranged vascular bundles, taproot	Roses, sunflowers, beans, oaks, maples, tomatoes, apples

Importance of Seed Plants for Human Welfare

Seed plants are vital for food, medicine, materials, and ecosystem health.

• Support human welfare in nearly every aspect of life.