Study Guide: Characteristics of Eukaryotes and Fungi

Unifying Characteristics of Eukaryotes

Geological Record

• Eukaryotes emerged approximately 2.1 billion years ago (BYA).

• Prokaryotes date back to about 3.8 BYA (e.g., Stromatolites).

Monophyletic Group

• Eukaryotes form a single clade from a common ancestor, characterized by:

  • Cells with nuclei.

  • Nuclear envelopes with nuclear pores.

  • Presence of mitochondria.

  • Cytoskeleton with microtubules and microfilaments.

  • Ability for motility (flagella or cilia in some lineages).

  • Organized chromosomes by histones.

  • Capability for mitosis and sexual reproduction.

  • Some lineages retain cell walls; many do not.

Prokaryote Metabolism & Endosymbiosis

Aerobic Respiration

• Utilizes mitochondria, present in all eukaryotic lineages and is efficient for ATP production.

Endosymbiosis Theory

• Eukaryotic cells originated from one cell engulfing another, with co-evolution.

• Mitochondria derived from bacteria; nuclear genes from archaea.

Mitochondria

• Unique to eukaryotic cells, with a range from 1 to over 1,000 per cell.

• Resemble proteobacteria, contain circular chromosomes similar to prokaryotes.

• Divide independently via binary fission.

Plastids

• Include chloroplasts; originated from cyanobacteria.

• Genome: Circular chromosome similar to mitochondria.

Protist Characteristics

• Paraphyletic group, diverse in structure and function, with over 100,000 species.

• Eukaryotic, but not classified as animals, plants, or fungi.

• Complex cellular structures with potential for animal-like or plant-like traits.

Protist Metabolism

• Diverse metabolic processes: aerobic, anaerobic, photoautotrophs, heterotrophs, and mixotrophs.

Protist Motility and Lifecycles

• Utilize flagella, cilia, and pseudopodia for movement.

• Asexual (binary fission) and sexual reproduction strategies, including complex life cycles.

Eukaryotic Supergroups

Six Recognized Supergroups:

1. Archaeplastida: Includes red and green algae, plants; shows alternation of generations.

2. Amoebozoa: Includes slime molds; unique for their feeding networks.

3. Opisthokonta: Includes closest relatives to animals (choanoflagellates).

4. Rhizaria: Important in the carbon cycle, includes foraminiferans and radiolarians.

5. Chromalveolata: Characterized by organisms engulfing red algae.

6. Excavata: Diverse group often linked to diseases.

Role of Protists in Ecosystem

• Major producers and contributors to global photosynthesis.

• Symbiotic relationships, especially between dinoflagellates and corals.

Pathogenic Protists

Affecting Humans and Animals

• Plasmodium: Causes malaria.

• Trypanosoma: Causes sleeping sickness.

• Giardia spp.: Causes gastrointestinal issues.

• Trichomonas: A sexually transmitted infection.

Fungal Cells

Overview

• Eukaryotic organisms; cell walls made of chitin.

• Types of growth: unicellular (yeasts) and multicellular (molds).

Fungal Nutrition

• Heterotrophs, including saprobes, parasites, and predatory fungi.

• External digestion by secreting enzymes.

Fungal Reproduction

• Reproduces both sexually and asexually; includes a variety of methods.

Major Phyla of Fungi

1. Chytridiomycota: Most primitive with flagella.

2. Zygomycota: Saprobes; e.g., black bread mold.

3. Ascomycota: Sac fungi; economic importance in food and medicine.

4. Basidiomycota: Club fungi; includes many edible mushrooms.

5. Glomeromycota: Associative mycorrhizae with plant roots.

Ecological Roles of Fungi

• Universal decomposers, essential for nutrient cycling.

• Form mutualistic relationships (e.g., mycorrhizae).

• Fungi in lichens provide stability and nutrients.

Fungal Parasites and Pathogens

Impact on Plants and Humans

• Fungal pathogens can rot crops and cause crop losses.

• Mycosis and mycotoxicosis affect animal populations and food safety.

Beneficial Use of Fungi

• Food applications (mushrooms, cheese).

• Medical applications (antibiotics like penicillin).