Bio Exam 3, Objectives

Prokaryote Features

- small

- no nucleus

- DNA in nucleoid

- cell wall

- no organelles

- cell membrane

- ribosomes

- bacteria and archaea (unicellular)

Eukaryote Features

- big

- nucleus

- DNA in nucleus

- no animal cell wall

- cell membrane

- organelles

- ribosomes

Cell-Surface Structures

- Cell walls (they're cellulose/chitin in eukaryotes) (chitin in fungi)

- Bacterial cell wall = peptidoglycan

- archaea cell wall = polysaccharides and proteins, but NO peptidoglycan

- inactive endospores

- fimbriae = allow sticking to others

- pili = allow DNA exchange

Gram-positive

- simple walls

- high levels of peptidoglycan

Gram-negative

- less peptidoglycan

- toxic outer membranes

Motility

- heterogeneous environments cause bacteria to exhibit taxis

- chemotaxis = movement to/away a chemical stimulus

- flagella = movement

Cell Internal Organization/DNA

- Prokaryotic genomes have less DNA than eukaryotic genomes (because of their circular chromosome, lack of membrane, and nucleoid)

- Plasmids: Smaller DNA rings found in some bacteria

Genetic Transformation: Transformation

- Uptake of exogenous DNA from the environment

- Transform using DNA from outside

Genetic Transformation: Transduction

- Virus-mediated transfer of DNA between bacteria

- Transfer DNA from bacteria to viruses

Genetic Transformation: Conjugation

- Transfer DNA from one bacterium to another via cell-to-cell contact

- Conjoined cells transfer DNA directly

Autotroph

- Produce own food

- Can use CO2 to make organic carbon

Heterotroph

- Cannot make own food

- Need direct organic carbon sources, cannot make on their own

Photoautotroph

- Use light as energy and use CO2, HCO2 as their carbon source

- Photosynthetic prokaryotes (cyanobacteria, algae)

Chemoautotroph

- Use inorganic chemicals as energy and CO2, HCO as their carbon source

- Unique to some prokaryotes (sulfolobus)

Photoheterotroph

- Use light as energy and organic compounds as their carbon source

- Unique to aquatic and salt-loving prokaryotes (Rhodobacter, chloroflexus)

Chemoheterotroph

- Use organic compounds as energy and carbon sources

- Many prokaryotes (clostridium), protists, fungi, animals, and some plants

Beneficial Bacterial Impacts on Eukaryotes

- Aid digestion, produce nutrients, support systems, protection

Harmful Bacterial Impacts on Eukaryotes

- Infection, disease, tissue damage, and death

Viral Genomes

- Can be RNA viruses or DNA viruses

- Genomes are either a strand or a circle of DNA/RNA

- Between 3 and 2000 genes in virus genomes

Capsid

- Protein shell enclosing the viral genome

- Built from capsomeres

Envelopes

- Surround the capsids

Phages

- Infect bacteria (bacteriophages)

Replicative Cycles: Lytic Cycle

- Virus puts genome inside the host and replicates by hijacking it's cells to make copies

- Attachment -> DNA released into host -> viral genome/protein synthesis -> self-assembly -> release

Replicative Cycles: Lysogenic Cycle

- Viral genome is in the host and it uses the host to replicate it by passing onto the daughter cells

- Attachment -> DNA integrates into chromosome -> DNA copied -> daughter cells have the prophage

Retrovirus

- Use reverse transcriptase to copy it's RNA into the host's DNA

- HIV

Protists

- Eukaryotes

- Mostly unicellular, some multicellular

- Asexual or sexual

- Nutritionally diverse (some photoautotrophs, heterotrophs, mixotrophs)

- Largest unicellular = valonia ventricosa/sailor's eye

Endosymbiosis

- One species lives inside the cells of another (the host)

Mitochondria

- Descend from bacterium that was engulfed by a cell from an archaeal lineage

Plastid Lineage

- Came later than mitochondrial

- From photosynthetic bacterium that was engulfed by a heterotrophic eukaryote

Ecological Communities: Protists

- Some are beneficial (wood-digesting enzymes in termites aka trichonympha)

- Some are parasitic (Plasmodium, causes malaria)

- Produce A LOT of oxygen and are important to the food chain

Nutrition and Ecology: Fungi

- Heterotrophs strictly (unlike protists) (chemoheterotrophs)

- Use enzymes to breakdown their food and continue to be successful

- Can be decomposers, parasites, or mutualists

Body Structure: Fungi

- Multicellular filaments and single cells (yeasts/fungi) (either or both)

- Mycelia: Branched hyphae (filaments) adapted for absorption in ALL fungi (nutrient absorption)

- Fungal cell walls contain chitin****

Septate and Coenocytic Hyphae

- Most hyphae (filaments) are 2 cells divided by septa, and pores allow cell-to-cell movement

- Coenocytic Fungi: no septa, have continuous cytoplasmic mass with 100s to 1000s of nuclei

Mycorrhizal Fungi: Ectomycorrhizal Fungi

- Sheaths of hyphae over a root that grow into the root cortex

Mycorrhizal Fungi: Arbuscular Mycorrhizal Fungi

- Hyphae go to the cell walls of root cells and into the tubes from invagination of the root cell membrane

Fungi Mutualism Between Plants and Animals

- mycorrhizae enhancing plant nutrient uptake, lichens (fungi-algae, important in soil formation) thriving in harsh environments, leaf-cutting ants farming fungi for food, and gut fungi assisting ruminant digestion

Examples of Fungi as Pathogens

- Candida (yeast infections, C. auris), Aspergillus (respiratory infections), Cryptococcus, and dimorphic fungi like Histoplasma.

Practical Uses of Fungi

- food production (bread, cheese, beer), medicine (antibiotics like penicillin), and creating sustainable materials like mycelium packaging, leather alternatives, and insulation

Protist Type Examples

- Trypanosoma, Amoeba, Paramecium = animal-like

- Euglena, diatoms, dinoflagellates = plant-like

- Slime molds = fungus-like

Plant Adaptations for Land Move

- Challenges: water availability, no structural support, radiation

- Adaptations/Advantages: Sporopollenin (zygotes/spores), sunlight, more CO2 than H2O, nutrient-rich soil

Plant Derived Traits: Generation Alternation

- Plants alternate between 2 stages of reproduction

- Haploids (gametophyte) produced from mitosis

- Diploids (sporophytes) produced from meiosis

- Both multicellular (produces spores/SPORophyte)

Plant Derived Traits: Multicellular Dependent Embryos

- Embryo (2n) retained within tissues of the female gametophyte

- Nutrients are transferred from the parent to the embryo through placental transfer cells

Plant Derived Traits: Walled Spores

- They produce walled spores in the sporangia

Plant Derived Traits: Apical Meristems

- Undifferentiated cells that constantly grow at the root tips

Bryophytes/Nonvascular Plants

- Nonvascular

- Liverworts, mosses, and hornworts

- All their gametophytes are larger and live longer than sporophytes (gametophyte dominant)*****

- Represent the earliest lineages to diverge from a common ancestor of land plants

Bryophyte Ecological/Economic Importance

- Mosses: Inhabit diverse/extreme environments (dominant gametophyte)

- May help nitrogen in soil

- Sphagnum: form extensive deposits of decayed organic material (peat = fuel source), and are a global reservoir of organic carbon

Tall and Vascular Plants

- Ferns and seedless were the first to grow tall

- Vascular tissues allows tall growth

- Seedless vasculars will have flagellated sperm and are restricted to moist environments

- Sporophyte dominant (mosses and ferns)

Vascular Plant Origins and Traits

- Independent, branching sporophytes

- Life cycles with dominant sporophytes (unlike nonvascular plants/bryophytes)

- Have xylem, phloem, roots, and leaves

Xylem and Phloem: Transport

- Vascular tissues

- Water-conducting cells strengthened by lignin (carry water = xylem, and carries food = phloem)

- Provide structural support

- Allow for more height, which is an evolutionary advantage

Root Evolution

- Roots function to anchor plants, store photosynthesis products, and absorb water/nutrients

- They may have evolved from subterranean stems

Rhizoids

- Hair-like filaments in non-vascular plants

Rhizomes

- Underground plant stems for storage and vegetative reproduction

Leaf Evolution

- Primary photosynthesis organs

- Increase surface area

- Microphylls: Small leaf, single vein

- Megaphylls: Big leaf, highly branched, vascular, increase surface area for photosynthesis

Seed Plants

- Less gametophytes

- Heterospory

- Ovules (develop into seeds)

- Pollen

- Evolved to protect embryo with a tough coat and provide them nutrients so they remain dormant until good conditions

Seed Plant: Ovule and Egg Production

- Ovule: Megasporangium, megaspore, and integuments

- Microspores develop to pollen grains (haploid and male gametophytes)****

- Pollination: Pollen transfer allowing fertilization (pollen grains transferred from anther to stigma)

- If pollen germinates, pollen tube forms and discharges sperm into the female gametophyte in ovule

Gymnosperm

- Naked seed

- Vascular

- Non-flowering plants (seed plants)

- Exposed on sporophylls forming cones (seeds on cones)

- Most are conifers, no flowers/fruits

1. Cycadophyta (cycads)

2. Gingkophyta (1 living: ginkgo biloba)

3. Gnetophyta (3 genera: gnetum, ephedra, welwitschia)

4. Coniferophyta (conifers, pine, fir, redwood)

Angiosperm

- Found in fruit (mature ovaries)

- Vascular

- Flowering plants

- Greater than 250,000 species

1. Monocots = 1 cotyledon

2. Dicots = 2 cotyledon

- Basal Angiosperm: include flowering plants

- Magnolids: share some traits with basal but evolved later

Root Types

- Taproot: first to emerge, tall plants and those with high shoot masses, develop from the primary root and prevent toppling

- Primary Root: branches to form lateral roots for more anchorage and water absorption

- Fibrous Root System: small plants, their lateral roots come from adventitious roots

- Adventitious Roots: arise from stem or leaves

- Root Hairs: Absorb water and minerals from the soil, tubular extensions of epidermal cells

Stems

- Organ with nodes and internodes

- Nodes: attachment points from branches or leaves

- Internodes: Stem segments between nodes, give height, structure, and support

- Apical bud: growing from the shoot tips to cause elongation (made of apical meristem - primary growth)

- Axillary Bud: Structure with potential to form lateral branches, thorns, or flowers (ex. if you were to pinch off the apical bud, then a plant would stop elongating and become "bushier")

Leaves

- Function to increase surface area for photosynthesis, prevent moisture loss, and limit competition

- Flattened lamina/petiole (stalk) join the leaf to the stem

- Monocots: parallel vein arrangement, scattered vascular bundles

- Dicots: Reticulate vein arrangement (netlike), bundles in a ring