Final Exam: Plants Flashcards
THREE MAJOR DOMAINS OF LIFE
- prokaryotes
- plastids
EUKARYA, ARCHAEA, BACTERIA
Prokaryotes: 2 of 3 major clades (“domains”) of life → archaea and bacteria; former more closely related to eukaryotes than latter
Plastids: general term that incl chloroplasts + basic organelles → not all eukaryotes contain plastids; the appearance of them in eukaryotes is a result of bacteria undergoing endosymbiosis
Eukaryotes Characteristics (6)
- non-motile filamentous (not-moving, thin, long)
- absorb nutrients
- cell walls composed of chitin
- a/sexual reproduction
- heterotrophic decomposers
- possess membrane-bound nucleus and organelles
including protists, animals, plants, and fungi
Archaea
aka extremophiles, or lovers of extreme conditions; many taxa cannot survive outside of these extremes; highly valuable for molecular biology, including the resolution of the tree of life
eg. halophiles (highly saline; inland seas, lakes); thermophiles (incredibly hot; volcanic vents); methanogens (aka “true” extremophiles bc live in anaerobic gut and produce methane as waste)
Bacteria
v diverse, represented in every major mode of nutrition and metabolism; can be the source of very bad diseases (eg. cholera) BUT some are capable of photosynthesis
(eg. cyanobacteria) unlike all known archaea → cyanobacteria contributed to creation of Oxygen rich atmosphere 1.8 billion years ago + was critical to nitrogen fixation (along w other bacteria)
MODES OF LIVING:
Autotrophs: make their own food from inorganic compounds; capture carbon from atmosphere as CO2
- Photo-troph: capture light energy and carbon
- Chemo-troph: capture energy from oxidizing inorganic substances
Heterotrophs: feed on organic substances (other organisms or their products)
Fungi
distantly related to land plants due to their interdependently evolved multicellularity BUT more closely related to animals than to any photosynthetic clade (1 billion years ago)
Algae + Economic Importance
aka former plastids; economic as food, medicine, and industrial; both a/sexual reproduction where alternations of generations occur in the sexual cycle; interdependently developed multicellularity
Economic Importance: excellent thickeners / emulsifiers for food, medical, or industrial purposes → eg. agar, agarose
Algae – General Characteristics
cellulose cell wall, photosynthesis, possess alternation of generations
Algae – Unicellular vs Multicellular
Unicellular: blue green bacteria, dinoflagellates, euglenoids, diatoms, golden algae, phytoplankton
Multicellular: brown, green, red algae, incl. Seaweeds
Algae – UNICELLULAR IN DEPTH
- Blue green: cyanobacteria are unicellular but commonly occur as filaments; contain heterocysts (location of N fixation)
- Euglenoids: heterotrophic via phagocytosis (swallowing); photosynthetic via secondary endosymbiosis of photosynthetic cells; have flagella and storage polysaccharides
- Dinoflagellates: external armor of cellulose plates and 2 flagella; can cause algal blooms and paralyze prey
- Diatoms: most diverse / ecologically important; mostly unicellular;cell walls made of hydrated silica; account for ~25% of Earth’s primary productivity; sink when dead which helps to remove carbon from environment, creating diatomaceous Earth → animal-like life cycle; asexually reproduce by reducing in size until a threshold is reached, then they reproduce sexually to create a full size diatom
- Golden algae: unicellular or colonial; carotenoid pigmentation
Algae – MULTICELLULAR IN DEPTH
- Brown: keystone taxa; gel-like polysaccharides help resist ocean buffeting / desiccation; similar structure to plants but not related (ie. anchor, blades, stipes)
- Red: pigmentation mask green color of chlorophyll; colored as such in order to take in light at deeper depths (red as the only color not reflected in wavelength)
- Green: unicellular to multicellular; close relatives of land plants
Alternation of Generations
- gametophyte
- sporophyte
Seen in all land plants but not in all algae
multicellular organism in the haploid phase of the life cycle + multicellular in the diploid phase = mitosis in both places
Gametophyte = gamete-producing plant; haploid, produce gametes by mitosis; fuse to form a diploid zygote which develops into a new sporophyte
Sporophyte = spore-producing plant; diploid, produce spores by meiosis → spores germinate to become gametophytes
Sexual Life Cycles in General – Animals, Fungi, Plants
Differ in relative timing of meiosis and fertilization + limitation of meiosis
Animals: only haploid is gametes; F after Me, no mitosis in btwn
Fungi: only diploid is zygotes; Me after F, no mitosis in btwn
Plant: Mi after Me after F; haploid / diploid alternation within the lifespan of the same species
Spores / Gametes: both haploid; unicellular reproductive cells BUT a spore germinates directly to form a new haploid organisms (involving mitosis) whereas a gamete fuses with another to form a zygote
LIFE CYCLES : Fungi
- Meiosis (division of cells into four haploids);
- Plasmogamy (cytoplasm of two parent cells fuses together without the fusion of nuclei, effectively bringing two haploid nuclei close together in the same cell)
- Karyogamy (final step in the process of fusing together two haploid eukaryotic cells to create a diploid) → free-living, photosynthetic, need water for fertilization
Sexual: mycelium > plasmogamy > dikaryotic stage > meiosis (produce spores) > germination → zygote as only true diploid stage
Asexual: mycelium > spore producing structures > germination
LIFE CYCLES : Bryophytes
- Meiosis (produces haploids with sexual being antheridia; asexual being archegonia), 2. Fertilization (aka syngamy; fusion of haploids to create diploids), 3. Mitosis (produces gametes in gametangia and sporophyte in sporangia)
LIFE CYCLES : Ferns
- Meiosis (germination; release of spores; sperm use flagella to swim from the antheridia to eggs in the archegonia)
- Fertilization (zygote develops into new sporophyte w reproductive leaves w spots called sori w clusters of sporangia)
LIFE CYCLE : Gymnosperms
- Meiosis (female gametophyte w sperm nucleus)
2. Fertilization (ovulate cone and pollen cone as parents to create megaspore; pollen is microsporangia)
LIFE CYCLE : Angiosperms
- Meiosis (ovary into megasporangium; microsporocytes into microspore w male gametophyte)
- Double fertilization (two sperm in pollen tube, one fuses with egg to form the zygote (2n) while the other fuses with two polar nuclei to form endosperm (3n), aka the nutritive tissue for the embryo)
LIFE CYCLE EXTRAS
- trends
- heterospory
Trends: gametophyte to sporophyte dominance; gametophyte size reduction; sporophyte size enlargement; minimal to extensive seed protection
Heterospory: Production of two diff types of spores, which become unisexual gametophytes; promote outcrossing and protection of vulnerable generation; precondition that allowed for the evolution of pollen / seed
Seed Plants
no need for standing water for fertilization
Seeds as a unit of dispersal may offer benefits for life on dry land, with potential for extensive dormancy and with a major food source contained inside to allow for initial establishment of root and shoot systems during germination
FIVE MAJOR CLADES OF FUNGI
C > Z > G > A > B
- coenocytic
bonus: D > O
- Chytridiomycota: microscopic; diverged early; only one with motile spores and gametes; important decompositional role; can be unicellular or filamentous; also includes disease causing organisms
- Zygomycota: really good at dispersing spores and very distinctive; most prolific spore production comes from asexual → diff gametangia types fuse together to form zygosporangium; haploid nuclei of G undergo fusion w/in Z to form many diploid zygotes, which undergo meiosis to make haploid spores that are then released»_space; Coenocytic: open cytoplasm inside hyphae, except for reproductive bodies (G, Z, and asexual spores)
- Glomeromycota: may have been the key to success for land plants (referring to ability for plants to colonize land before roots); incl arbuscular mycorrhizal fungi; no sex known
- Ascomycota: aka sac fungi; highly diverse with distinctive sacs (known as asci) in which sexual spore are formed, found often home in fruiting bodies (known as ascocarps)
- Basidiomycota: aka club fungi; lots of edible taxa; produce basidia in basidiocarps, which are often produced at the leading edge of radiating mycelium, where resources are richest thus creating “fairy rings”
BONUS:
- Deuteromycota (fungi imperfecti): asexual
- Oomycota (slime mold): has protoplasmic streaming for rapid movement of oxygen and nutrient within plasmodium; engulfs food until depleted, upon which will harden to create sporangia
Ascomycota and Basidiomycota…
also incl yeasts, which can reproduce by asexul budding → unicellular fungi and v diverse
Only true diploid stage is zygote; after plasmogamy, fungi with septate hyphae produce dikaryotic hyphae of two nuclei that fuse only in the fruiting bodies; M after K to produce haploid sexual spores → dikaryotic stage as after P but before K (long lived in basidio, making up bulk of mycelium)
Fungal Characteristics (6)
- fruiting bodies (multicellular) or “yeast” forms (unicellular)
- non-motile bodies
- multicellular organisms are filamentous (made of mycelium made of hyphae, which are tubular filaments of high surface area to volume ratio therefore greatly enhancing absorption → leads to high possibility of drying out, therefore thrives in moist environments)
- Considered eukaryotes (bc have nuclei and mitochondria) but do not have chloroplasts → cell walls are present but contain CHITIN, not cellulose
- Life cycle includes spores
- Store carbon as glycogen (not starch) → absorptive mode of nutrition, also heterotrophic
Fungal importance to humans
Food: cheese, yeast, alcohol → some taxa look edible but are actually poisonous (amanita) or hallucinogenic (cause ergotism / temporary insanity; may have had a role in salem witch trials)
Disease causing / preventing (eg. penicillin)
Fungi as Mutualistic
- micorrhizal (2)
- endophytes
- lichen (3)
Mycorrhizal Association: mutualism between fungi and plants → 450 million years ago, fungi invaded land, and nowadays the fungi incorporate themselves into plant roots for a MUTUALISTIC relationship (eg. fungi gather phosphorus for plants)
- Ectomycorrhizal: found at temperate or boreal latitudes: fungal hyphae do not permeate cell walls, just spaces between cells (and outside of root)
- Arbuscular: makes up 80 to 90% of all plant relationships with fungi; penetrate cell wall (but not membrane) and have extensive contact with the cell membrane
Endophytes: aka microfungi inside plants that enter via plant pores that allow gas exchange; help repel herbivores by being unpalatable and therefore help improve plant tolerance in environmental conditions
Lichen: association between a fungus (usually an ascomycete) and a unicellular photosynthetic green alga or cyanobacterium; play an important role in primary succession with the ability to colonize and breakdown barren surfaces and some nitrogen fixation (allow for better plant growth) → lichen reproduce asexually and disperse as a unit called soredia
- Foliose: “leafy”
- Fruticose: “shrubby”
- Crustose: “crusting
Endosymbiosis
process of incorporation of one organisms within the “cell” of another → multi-step process: early eukaryote (with cytoskeleton) engulfed by a prokaryote that become mitochondria
Evidence for Endosymbiosis (5)
S > Re > Ri > A > G
- Size and structure of mitochondria / plastids similar to bacteria
- Replication: reproduce by binary fission
- Ribosomes: complexes of RNA and protein involved in genetic translation and protein synthesis
- Antibiotics: target protein synthesis in bacteria
- Genomes: mitochondria / plastids have genomes (usually circular, genetically similar to bacteria) separate from nuclear genome
Secondary Endosymbiosis
some photosynthetic eukaryotes among “algae” have plastids surrounded by 3-4 membranes (more than expected for primary endosymbiosis) → additional membranes created from the engulfing of photosynthetic single-celled eukaryotes that have already acquired a plastid from an earlier engulfment) → explains the appearance of plastids in all eukaryotes
No eukaryote evolved photosynthesis independently of cyanobacteria, which became incorporated into eukaryotic cells either primarily or secondarily to result in photosynthetic organisms in a wide diversity of clades.
Red + 3 or more major secondary endosymbiosis = presence of chloroplasts
Bryophyte Characteristics (9)
- primarily dominant haploid but also has fleeting, diploid generation
- free-living
- lack rigidity because does not have conducting tissue (lacking lignin), unlike vascular plants
- sporophytes are typically visible to the naked eye
- desiccation tolerance therefore great at hydrating and taking up resources quickly (trait not seen in vascular plants, especially seed)
- No roots → possess unicellular or filamentous rhizoids as anchor
- alternation of generations
- dominance of gametophyte
- development of archegonium and antheridium
3 Major Lineages of Bryophytes
MOSS: dominant “leafy” gametophyte generation; requires standing water for fertilization; peristome regulates spore dispersal; can reproduce aseuxually
LIVERWORTS: name refers to shape of thing; unobvious sporophytes that don’t have stomata; earliest delineation from land plants; flattened, prostate gametophyte
HORNWORTS: flattened, prostate gametophyte has association with cyanobacteria that allow for Nitrogen fixation and primary succession; horn shaped structures are sporophytes grown from archegonium; indefinite growth
Ecological Importance of Bryophytes
PEAT MOSS EXAMPLE
Acidity and chemistry (aka phenolics) of bogs are dominated by peat mosses, which inhibit decay via anaerobic, high altitude, and saturated soils → lack of decay leads to carbon build up, which are then harvested for fuel
Good at preserving fossils via low pH, cool temperatures, and anaerobic conditions → allowing for reconstruction of past lifestyles
Prevent microbial activity → used in WWII as sterile bandaging of wounds in highly dirty trenches, which saved a lot of lives
Eg. “bog people” of Ancient N. Europe
