Unit 3: Plants

Question 1

THREE MAJOR DOMAINS OF LIFE

Answer 1

EUKARYA, ARCHAEA, BACTERIA

Eukaryotes: 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

Prokaryotes: 2 of 3 major clades (“domains”) of life → archaea and bacteria; former more closely related to eukaryotes than latter

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)

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)

Question 2

FUNGI + CHARACTERISTICS (6)

Answer 2

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)

1. fruiting bodies (multicellular) or “yeast” forms (unicellular)
2. non-motile bodies
3. 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)
4. Considered eukaryotes (bc have nuclei and mitochondria) but do not have chloroplasts → cell walls are present but contain CHITIN, not cellulose
5. Life cycle includes spores
6. Store carbon as glycogen (not starch) → absorptive mode of nutrition, also heterotrophic

Question 3

ALGAE + CHARACTERISTICS + TYPES

Answer 3

aka former plastids; photosynthetic organisms occur in 4 of 5 supergroups (aka the major groups of eukaryotes) as well as in cyanobacteria due to endosymbiosis; economic as food, medicine, and industrial; both a/sexual reproduction where alternations of generations occur in the sexual cycle

General Characteristics: cellulose cell wall, photosynthesis, possess alternation of generations

Unicellular: blue green bacteria, dinoflagellates, euglenoids, diatoms, golden algae, phytoplankton
Multicellular: brown, green, red algae, incl. Seaweeds

Question 4

FUNGAL LIFE CYCLE *photo

Answer 4

1. Meiosis (division of cells into four haploids)
2. Plasmogamy (cytoplasm of two parent cells fuses together without the fusion of nuclei, effectively bringing two haploid nuclei close together in the same cell)
3. 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

Question 5

BRYOPHYTE LIFE CYCLE *photo

Answer 5

small, alternation of generations, dominance of gametophyte, development of archegonium and antheridium

1. 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)

Question 6

FERN LIFE CYCLE *photo

Answer 6

1. Meiosis (release of spores; sperm use flagella to swim from the antheridia to eggs in the archegonia)
2. Fertilization (zygote develops into new sporophyte w reproductive leaves w spots called sori w clusters of sporangia)

Question 7

GYMNOSPERM LIFE CYCLE *photo

Answer 7

1. Meiosis (female gametophyte w sperm nucleus)

2. Fertilization (ovulate cone and pollen cone as parents to create megaspore; pollen is microsporangia)

Question 8

ANGIOSPERM LIFE CYCLE *photo

Answer 8

1. Meiosis (ovary into megasporangium; microsporocytes into microspore w male gametophyte)
2. 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)

Question 9

LIFE CYCLE EXTRAS (5)

Answer 9

Trends: gametophyte to sporophyte dominance; gametophyte size reduction; sporophyte size enlargement; minimal to extensive seed protection

Heterospory: takes gametophyte reduction to a new level → two different types of spores produces (aka two diff sporangia, micro / mega) that are morphologically different + protected to an exaggerated extent than ever before; precondition that allowed for the evolution of pollen / seeds

Animals: only haploid in gametes; fertilization occurs just after meiosis without mitosis in between

Fungi: only diploid in zygote; meiosis occurs after fertilization is complete with no mitosis in between

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

Question 10

FIVE MAJOR CLADES OF FUNGI

Answer 10

Chytridiomycota: microscopic; difficult to find and isolate; not easily distinguishable; diverged early in history of fungi with motile spores and gametes; important decompositional role; can be multi or unicellular filamentous, therefore have a lot of forms; also includes disease causing organisms

Zygomycota: really good at dispersing spores and very distinctive; considered a mold on ecological level (not taxonomic) because has growth where mycelium is on outside of substrate as opposed to inside; has zygosporangium, which is a structure formed after reproduction that holds cryptic sexual bodies; also has gametangia, which are specialized hyphae that are attracted to each other via pheromones (sexual attractive compounds) that fuse together (if different mating types); zygosporangium (aka production of sexual spores) formed from fusion of gametangia of sexual hyphae

Glomeromycota: once thought to be zygomycetes BUT separate recently resolved MAJOR CLADE; may have been the key to success for land plants (referring to ability for plants to colonize land before roots); no sex known

Ascomycota: aka sac fungi; highly diverse with distinctive sacs (known as asci) in which sexual spore are formed; asci often home in fruiting bodies (known as ascocarps, or reproductive organs)

Basidiomycota: aka club fungi; lots of edible taxa incl. mushrooms, puffballs, brackets are among different fruiting bodies → fruiting bodies used as their reproductive organs, often produced at the leading edge of radiating mycelium, where resources are richest thus creating “fairy rings”

Question 11

FUNGI EXTRAS (2) + CHARACTERISTICS (8)

Answer 11

BONUS: Deuteromycota (fungi imperfecti) and Oomycota (slime mold)

1. cell walls of chitin
2. absorbant nutrition system
3. fruiting bodies (multicellular) or “yeast” forms (unicellular)
4. non-motile bodies
5. 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)
6. considered eukaryotes (bc have nuclei and mitochondria) but do not have chloroplasts
7. store carbon as glycogen (not starch)
8. heterotrophic

Question 12

FUNGI AS MUTUALISTIC

Answer 12

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 → eg. cocoa tree, where study found that trees without endophytes were more susceptible to pathogens + grasses, where fungal endophytes 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)

Question 13

RETURN TO ENDOSYMBIOSIS

Answer 13

Theory of 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: Size / structure, replication, ribosomes, antibiotics, genomes

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

Question 14

3 MAJOR LINEAGES OF BRYOPHYTES + CHARACTERISTICS (5) + ECOLOGICAL IMPORTANCE

Answer 14

3 Major Lineages of Bryophytes: Hornworts currently leading in which group is most closely linked to land plants

1. MOSS: lots of cryptic species
2. LIVERWORTS: ~9k species; name refers to shape of thing; unobvious sporophytes that don’t have stomata; earliest delineation from land plants
3. HORNWORTS: gametophyte has association with cyanobacteria that allow for Nitrogen fixation and primary succession; horn shaped structures are sporophytes grown from archegonium

CHARACTERISTICS:

1. primarily dominant (most present / complex in life cycle) haploid but also has fleeting, diploid generation
2. free-living
3. lack rigidity because does not have conducting tissue, unlike vascular plants
4. sporophytes are typically visible to the naked eye
5. desiccation tolerance therefore great at hydrating and taking up resources quickly (trait not seen in vascular plants, especially seed)

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 (Eg. “bog people” of Ancient N. Europe)
• Prevent microbial activity → used in WWII as sterile bandaging of wounds in highly dirty trenches, which saved a lot of lives

Question 15

EARLY PLANT ADAPTATIONS TO LAND (7)

Answer 15

1. Desiccation resistant spores and multicellular sporangia: sterile jacket cells to protect developing spores
2. Cuticle: waxy outer covering that helps reduce water loss
3. Stomata: found on sporophytes; pores allow gas exchange (CO2) in presence of cuticle
4. Gametangia: haploid on gametophytes has sterile jacket; extends to protect embryo
5. Embryo: sheltered and nourished inside the female gametangia
6. Fungal Association: glomeromycetes x land plants; allowed them to colonize land
7. Production of rich secondary chemistry: refers to chemicals not involved in energy production; used to be considered waste but actually helps protect plants from UV light and then (later) herbivores

Question 16

INNOVATIONS OF VASCULAR PLANTS (5)

Answer 16

1. Dominant sporophyte generation: diploid constitution allows for more complexity and protection from deleterious genes
2. Well developed cuticle: has lignin
3. Vascular tissue: allows for rigidity; made of xylem (water and inorganic nutrients) or phloem (sugar and other organic compounds) to conduct material throughout the plant body
4. Branched sporophyte
5. Roots

Question 17

GYMNOSPERMS (4+1)

Answer 17

Defined as the of two major lineages of seed plants (the other is angiosperm); woody plants with seeds usually in cones and not enclosed in ovary (“naked seeds”), therefore exposed to environment → cycadophyta, ginkgophyta, gnetophyta, coniferophyta

CYCAD: the almost-palm (flower, coveted, rare, almost extinct); unbranched stem clothed by persistent leaf vase; huge cones; tough leaves; found in tropics via insect dispersion

GINGKO: possibly related to cycads (?); highly branched woody stems with fan shaped, deciduous leaves; wind dispersed; seeds borne on stalks with no cone (fleshy, gross smelling); medicinal species; only one species left as a result of natural extinction

SHARED CHARACTERISTICS WITH CYCAD: largest sperm in the world (flagellated); produce either pollen or seed but not both on the same tree (gendered trees) BUT cycad can change their sex within their lifetime

GNETO: about 80 species; grow in different environments, don’t look alike BUT unified through fine scaled features; can be a shrub or platypus
Eg. Mormon tea ephedra: shrub example; can be made into various stimulants (ephedrine, meth)
Eg. Welwitschia: 2 foliage leaves that split indefinitely; non-elongated woody stems; grown in cultivation

CONIFERO: oldest, biggest, tallest, most diverse surviving lineage (>600 species); decay and insect resistant bark and wood contributes to longevity / size, resulting in some of the oldest / largest well known non-clonal organisms; dominant in harsh environments worldwide (eg. higher latitudes / altitudes) BUT not well represented in lowland tropics

Question 18

ANGIOSPERMS: important changes (3+1) + anatomy (5)

Answer 18

Important Changes to Life Cycle: Increase in size of sporophyte and reduction of size of gametophyte; seed coat (originates from integument); female gametophyte is the main content of pine seed, where the embryo embedded inside the gametophyte is the next sporophyte generation → three generations of tissue protecting each other

Anatomy:
Cone: made up of sterile / fertile appendages (= modified leaves, usually 3+ at a node) separated by very short stem segments (=internodes, usually so short as to be invisible)
Sepals: protective, help to reduce grazing
Petals: visually attractive to pollinators → understanding floral advertisement by petals requires considering the visual spectrum of the dominant pollinators (eg. bees see in lower wavelengths than we do)
Stamen: aka sporophyll; have stalk with anther (enlarged tip) filled with sporangia; outer layer of pollen are v decay resistant; allow for study of history → modified leaf that bears microsporangia (typically differentiated into a filament and anther
Carpal: MOST DISTINCTIVE FEATURE OF FLOWERING PLANTS; can be multiple or free / fused; individual units called pistil, made of stigma (at tip), style (tube), and ovary (bulbous bottom) → enrolled leaf with fused margins containing ovules

Question 19

BIOTIC TYPES OF POLLINATION

Answer 19

BIOTIC Types of Pollination: ancestral in flowering plants; requires an attractant or advertisement, such as showy parts or an odor → reward for pollinators often present (expensive to produce); often sticky, oily, clumped, sculptured; eg. nectar produced by nectaries; located variously in a flower with the floral timing synched with pollinator activity
eg. Helianthus with bright yellow petals to attract pollinators

Bee: deceitful pollination; flower appear / smell like female bees

Moth: whitish floral coloration; present (often sweet) floral scent

Butterfly: colorful floral coloration; no floral scent

Bird: colorful (often reddish) floral coloration; no floral scent

Bat: white / pale floral coloration; fruity / musky floral scent

Fly: reddish / light spotted (often fleshy textured) floral coloration; rotten floral scent

Question 20

MECHANISMS AGAINST SELFING (5)

Answer 20

selfing, aka, inbreeding can have deleterious consequences genetically via reduction in the variability of offspring (needed for their successors to survive)

1. Genetic incompatibility: aka “SI”; genetically based system that allows plants to recognize pollen that shares one or both alleles of the “S” gene and to prevent those male gametophytes from reaching the ovules&raquo_space;> Many flowering plants have lost SI, therefore allowing selfing where outcrossing does not occur BUT have other mechanisms to promote outcrossing
2. Unisexual (imperfect) flowers: possessing either only functional stamen (male) or carpals (female) → promotes outcrossing and reduces inbreeding
   - MONOecious: both sexes on one individual
   - DIoecious: one sex on one individual; sex separation
3. Spatial separation of anthers and stigmas in the same flower: differ in relative height placement → eg. anthers of one mating type at the same height as stigmas in a compatible mating type
4. Temporal separation of pollen release and stigma receptivity in the same flower
5. Co-evolution of pollinator x plant relationships: one of the most effective / efficient relationships
   Inflorescence: architecture of floral presentation varies across different angiosperm taxa

Question 21

FRUIT

Answer 21

Fruit Development and Precursory Structures: ovary at maturity becomes all or part of the fruit → 3 types of fruit: simple, aggregate, multiple
Simple: typically fleshy; derive from one ovary; dispersed with the seed → eg. cherries
Aggregate: derived from >1 separate carpels of 1 flower → eg. raspberries
Multiple: derived from multiple flowers, aka compact inflorescence → eg. pineapples

BONUS: accessory fruit: fruit with fleshy parts derived largely from tissues other than the
ovary; includes all three types of fruit → apple (s), strawberry (a), dig (m)

Fruit and Seed Dispersal:
diverse; often cover entire fruit of plant (can be just seed though)
fruit seeds evolved in response to a/biotic agent
Eg. wind and winged seeds
Water dispersal interesting because involves buoyancy, necessity of long distance travel, water resistance, etc.
Animal dispersal:
Accidental as not intentional vs Active as using for a purpose
External as clinging to fur or Internal as ingestion

Question 22

PLANT ANATOMY

Answer 22

DERMAL: outer protective covering of plant body; primary growth called epidermis; has cuticle to prevent dehydration and stomatal (pores); can also have hairy protrusions

GROUND: incl. Cells that are specialized for photosynthesis, storage, and support (that is, the most metabolically active); lies between dermal and vascular tissues in stems / roots called cortex or (if internal to ring of vascular) in EUDICOTS then called pith

1. PARENCHYMA: LIVING CELL; most metabolically active; undergo photosynthesis; different from embryonic cell types with thin primary walls that are flexible / can divide, therefore very responsive to damage; also contains chloroplasts that can be used in storage
2. COLLENCHYMA: LIVING CELL; just below the epidermis; unevenly thick walls that serve as structural support for parts of the plant that are still lengthening, therefore still a little flexible → eg. celery strands
3. SCLERENCHYMA: DEAD CELL at functional maturity; one of the most rigid, therefore provides the greatest structural strength; have both primary and secondary walls (second impregnated with lignin, a polymer that makes wood hard); not capable of expansion → eg. can be boxy (sclereids) or elongated (fiber)

VASCULAR: aka conducting; xylem and phloem are discrete but adjacent components of vascular tissue (exact arrangement differs between different types of organs)

1. XYLEM: conduction of water and inorganic nutrients from the soil&raquo_space; Tracheids: diagnostic feature of all plants; elongated with tapered ends; heavily lignified and hollow; essentially tubes for water to flow through; move from tracheid to tracheid via pits (naked primary walls that are permeable to water)&raquo_space; ++Vessel elements: usually present in tracheids / fibers; not a lot of structural strength; have perforation plates at the ends with large openings; better at conducting
2. PHLOEM: conduction of organic nutrients made by the plant (eg. sugar)&raquo_space; Sieve cells: connected to form sieve tubes (living!) that has a 1:1 peripheral of cytoplasm around the inner perimeter of the cell but not fully endowed with nucleus / ribosome therefore hollow for nutrient transport; sieve plate rapidly responds to damage via kalos that closes the wound to prevent sugar bleeding&raquo_space; ++ Companion cells: sister to sieve; helps regulate functioning of sieve tubes since the latter doesn’t have a nucleus or anything

Question 23

SHOOTS VS ROOTS SYSTEM + SHOOT ANATOMY + BUD TYPES

Answer 23

Shoot is considered to be the leaves and stem (above ground components); root is considered to be the roots (below ground components).
Shoot is developmentally / morphologically / anatomically different from the root system.
Shoot captures CO2 and light, performs photosynthesis to create sugar
Root anchors plant, transports water and inorganic nutrients of soil

Shoot Anatomy:

1. Node: point where the leaf connects to the stem → internode: between consecutive leaves
2. Leaves: made of blade and petiole (connection between stem and blade); blade as a platform for photosynthesis

Buds: opportunity for elongated growth

• Auxiliary: located in upper angle between petiole and stem
• Apical: aka terminal; located at the top of stem

Question 24

TYPES OF PLANT GROWTH

Answer 24

Plants are modular (open development), meaning that multiple units can regenerate.

Determinate Growth: growth up to a certain point than stopping → eg. human height

Indeterminate Growth: potential for elongating growth all their life → eg. plants (but plant leaves can individually have determinate growth)

Meristems: apical; sites of active cell division which can continue indefinitely in plants; indeterminate; located at shoot / root tips

Shoot Apical Meristem (SAM): produces new leaves at periphery and undergoes cell division mostly parallel to surface of SAM that add length to shoot with cellular enlargement and different into different cell / tissue types below SAM → responsible for growth in length of stem (can also have root apical meristem)

Question 25

EUDICOT VS MONOCOT *photo

Answer 25

Germination: early establishment of the sporophyte → the weakest link because of high mortality rates at this stage; occurs only in optimal conditions that trigger different cues (long vs short term cues)

First to emerge is the embryonic root → most advantageous as can obtain water

Gravitropism: in relation to the pull of gravity → (+) if downward, (-) if upward

EUDICOT: hypocotyl has (-) gravitropism, therefore pulls cotyledons above the ground (hook) and straightens once exposed to sunlight to promote growth of the shoot tip and foliage leaves

MONOCOT: coleoptile (protective sheath) emerges first with (-) gravitropism, acting as a tunnel that the shoot tip can grow through (therefore having to damage from the soil); cotyledon remains underground to supply nutrients