BIO 111 Exam 3 Review: Phylogeny, Prokaryotes, Eukaryotes, Plants, and Fungi

Phylogeny and Systematics

Understanding Phylogeny

Phylogeny is the evolutionary history and relationship among species or groups of organisms. Systematics uses phylogenetic trees to depict these relationships.

• Phylogenetic Tree: A diagram showing evolutionary relationships. Key features include:

  • Branch Points (Nodes): Represent common ancestors where lineages diverge.

  • Sister Taxa: Groups that share an immediate common ancestor.

  • Outgroup: A lineage that diverged before the group of interest, used for comparison.

• Homology vs. Analogy:

  • Homology: Similarity due to shared ancestry (e.g., vertebrate forelimbs).

  • Analogy: Similarity due to convergent evolution, not common ancestry (e.g., wings of birds and insects).

• Convergent Evolution: Independent evolution of similar features in different lineages.

Example: The wings of bats and birds are analogous structures, while the forelimbs of whales and humans are homologous.

Traditional Linnaean Classification

• Hierarchy: Kingdom, Phylum, Class, Order, Family, Genus, Species.

• This system groups organisms based on shared characteristics.

Prokaryotes vs. Eukaryotes

Major Differences

• Prokaryotes: Lack a nucleus and membrane-bound organelles; include Bacteria and Archaea.

• Eukaryotes: Have a nucleus and membrane-bound organelles; include Protists, Plants, Fungi, and Animals.

Structures Specific to Bacteria

• Cell Wall: Contains peptidoglycan (unique to bacteria).

• Flagella: Used for movement; structurally different from eukaryotic flagella.

Gram-Positive vs. Gram-Negative Bacteria

Feature	Gram-Positive	Gram-Negative
Cell Wall	Thick peptidoglycan layer	Thin peptidoglycan layer, outer membrane present
Staining	Retains crystal violet (purple)	Does not retain crystal violet (pink/red)
Antibiotic Sensitivity	Generally more sensitive	Often more resistant due to outer membrane

Antibiotics

• Target bacterial structures (e.g., cell wall synthesis, protein synthesis).

• Gram-negative bacteria are often more resistant due to their outer membrane.

Modes of Nutrition

Prokaryotes

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

• Chemolithoautotrophs: Use inorganic chemicals for energy and CO2 as a carbon source.

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

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

Eukaryotes

• Photoautotrophs: Plants and algae (photosynthesis).

• Chemoheterotrophs: Animals, fungi, and many protists (consume organic material).

Major Eukaryotic Groups

• Protists: Mostly unicellular, diverse modes of nutrition and reproduction.

• Plants: Multicellular, primarily photoautotrophic.

• Fungi: Multicellular (except yeasts), absorb nutrients from environment.

• Animals: Multicellular, ingest food.

Secondary Endosymbiosis

Secondary endosymbiosis occurs when a eukaryotic cell engulfs another eukaryotic cell that has already undergone primary endosymbiosis, leading to complex plastids in some protists.

Plant Diversity and Life Cycles

Four Major Categories of Plants

• Bryophytes: Nonvascular plants (mosses, liverworts, hornworts).

• Seedless Vascular Plants: Ferns and relatives.

• Gymnosperms: Seed plants without flowers (conifers, cycads).

• Angiosperms: Flowering plants.

Plant Life Cycle (Alternation of Generations)

• Plants alternate between a multicellular haploid gametophyte and a multicellular diploid sporophyte.

• The relative dominance of each stage varies among plant groups.

Example: In bryophytes, the gametophyte is dominant; in vascular plants, the sporophyte is dominant.

Major Reproductive Structures

• Sporangia: Produce spores.

• Gametangia: Produce gametes (archegonia for eggs, antheridia for sperm).

• Seeds: Protective structures containing plant embryos (in gymnosperms and angiosperms).

• Flowers: Reproductive organs of angiosperms.

Seed Plant Structures

• Ovule: Structure that develops into a seed after fertilization.

• Pollen: Male gametophyte that delivers sperm to ovule.

• Seed: Contains embryo, food supply, and protective coat.

Homosporous vs. Heterosporous Plants

Type	Spore Production	Examples
Homosporous	One type of spore	Most ferns, bryophytes
Heterosporous	Two types: megaspores (female), microspores (male)	Seed plants

• Mega- refers to female structures (e.g., megaspore, megagametophyte).

• Micro- refers to male structures (e.g., microspore, microgametophyte).

Structure and Function of Flowers

• Sepals: Protect the flower bud.

• Petals: Attract pollinators.

• Stamens: Male reproductive organs (anther and filament).

• Carpels (Pistil): Female reproductive organs (stigma, style, ovary).

The flower life cycle involves pollination, fertilization, seed development, and fruit formation.

Fungi

Major Fungal Structures

• Hyphae: Thread-like filaments forming the body of the fungus.

• Mycelium: Network of hyphae.

• Fruiting Body: Reproductive structure (e.g., mushroom).

Fungal Contributions to Ecosystems

• Decomposers: Break down organic matter, recycling nutrients.

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

• Pathogens: Cause diseases in plants and animals.

Basic Fungal Reproductive Cycle

• Fungi reproduce via spores, both sexually and asexually.

• Sexual reproduction involves plasmogamy (fusion of cytoplasm), karyogamy (fusion of nuclei), and meiosis.

• Asexual reproduction typically involves mitosis to produce spores.

Additional info: Species-specific details are not required; focus on general processes.