lab 7: non-vascular plants & seedless vascular plants

Question 1

phylogenies

Answer 1

-green algae are important photosynthetic organisms in freshwater habitats, while land plants are the key photosynthesizers in terrestrial environments
-the transition from aquatic to terrestrial life occurred when land plants evolved from green algae, their closest living relatives 500 mya

Question 2

what do we need plants for?

Answer 2

-ecosystem services, food supply, fuel, fibers, building materials, medicines, limit erosion by wind & water, hold water in soil, moderate local climate, produce oxygen at least 28%, build soil, dominant primary producers in terrestrial ecosystems & provide the base of the food chain

Question 3

what are morphological differences in land plants?

Answer 3

based on morphology, the major phyla of plants are grouped into 3 categories: non-vascular plants (bryophytes), seedless vascular plants & seed plants

Question 4

reproduction in dry conditions

Answer 4

-gametangia: reproductive organs
-retained embryos, pollen, seeds, & flowers enable them to reproduce efficiently even in dry environments
-the innovations instrumental for efficient plant reproduction in dry environments:
-spores: that resist drying out bc they have a protective coat around them, strong, can survive so much
-gametes: female & male gametes that are produced in a gametangia

Question 5

producing gametes in protected structures

Answer 5

-plants can be dioecious meaning that they have separate female & male plants
-monoecious can have male & female part of the same plant
-gametangia: reproductive structure find antheridia (male) &/or archegonium (female)
-zygote will divide & mature in the archegonium to produce sporophyte
-sporophyte will remain attached to the gametangia

Question 6

alternation of generations

Answer 6

-they have the multicellular haploid phase (gametophyte) & a multicellular diploid phase (sporophyte)
-they are connected by gametes (egg/sperm) & spores

Question 7

different trends in the 2 groups

Answer 7

-in non-vascular plants (bryophytes) have the sporophyte (2n) is smaller & short lived & is largely dependent on the dominant gametophyte (n) for nutrition
-in seedless plants (ferns) the dominant sporophyte (2n) is much larger & long lived than the gametophyte (n)
-backwards

Question 8

non-vascular plants (bryophytes)

Answer 8

-important: lack vascular tissue (xylem & phloem)
-liverworts, mosses & hornworts
-gametophyte phase is dominant phase
-earliest branching group among land plants (most ancient living group of plants)
-grow low to the ground (no water-conducting cells)
-have rootlike structures (rhizoids) helps to anchor the plant to the soil & absorb nutrients
-find them in moist habitats (have to be low to the ground bc they lack these tissues)
-can be small; we use them for many things like (whisky or packaging)

Question 9

bryophyte life cycle: sexual reproduction

Answer 9

-alternation of generations
-thallus= plant body
-antheridia= male sex organs that produce swimming sperm
-archegonia= female sex organs the produce eggs
-they need water for fertilization (sperm swim to egg)
-fertilization produces zygote
-zygote will divide & mature in the archegonium to produce sporophyte (has spores in it)
-sporophyte will remain attached to the reproductive structure (gametophyte)
-mature sporophyte will produce haploid spores via meiosis (each can develop into a gametophyte)

Question 10

non-vascular plants: phylum hepaticophyta (liverworts)

Answer 10

-earliest land plants
-will find all these on the floor
-sexual reproduction: archegonia & antheridia
-some asexual reproduction: gemmae (splash) cups: call it fragmentation: pieces of gemmae break off & spread by raindrops
-liverworts will have these elaters which will help disperse spores by twisting (depends on conditions of the environment)
-in humid conditions; elaters coil
-when dry, elaters expand & spores are released

Question 11

non-vascular plants: phylum bryophyta (mosses)

Answer 11

-can use them for packaging, able to dry out then rehydrate later
-asexual reproduction: fragmentation
-most are dioecious (separate male & female plants)
-sexual reproduction doesn’t occur often via self-fertilization bc the sexes are separate
-large deposits of sphagnum moss / peat, can add to soil, used as fuel, flavoring food or drink like whisky

Question 12

moss sporophyte

Answer 12

-capsules located atop stalks called setae
-sporophyte is attached to rhizoid or a foot to attach to the soil
-capsules are covered by calyptra (open up & fall off when the capsule matures)
-then the haploid spores will get released
-haploid sperm released from antheridia -> sperm swim to archegonia -> down necks to fertilize -> diploid zygote -> matures to diploid sporophyte -> sporophyte grow in archegonium -> differentiates into a slender seta w swollen cap on end -> capsule is covered by calyptra -> sporophyte grown on gametophyte & produce spores (meiosis) -> buds produce leafy gametophytes

Question 13

non-vascular plants: phylum anthocerophyta (hornworts)

Answer 13

-smallest group: 100 species
-look like horns & grow up in the air
-gametophyte will grow flat
-archegonia are embedded in the thallus (not discrete organs)

Question 14

seedless vascular plants

Answer 14

-have well-developed vascular tissue (xylem & phloem) but do not make seeds, which consist of an embryo & a store of nutritive tissue, surrounded by a tough protective layer
-they have specialized group of cells are used to transfer water & nutrients up from the roots to the shoot to the leaves
-create spores
-grow away from the ground
-non-flowering
-depend on water for reproduction
-sporophyte is the dominant phase but gametophyte is nutritionally independent
-have sporophylls: spore leaf-like structures, spore-forming leaves (can be megaphylls: many veins or microphylls: one vein)

Question 15

seedless vascular plants: phylum pteridophyta (ferns)

Answer 15

-about 12,000 species
-find a lot in the tropics
-can be very small (few centimeters to 20 meters)
-most species reproduce sexually
-underneath the fern, they have groups of sporangia (we call it sori) find spores
-the sporangia is protected by indusium
-only seedless vascular plant to have these big leaves (fronds), which give them a large surface area for photosynthesis
-fiddlehead breaks through fronds & unrolls to display the frond/leaf
-these terrestrial ferns are homosporous (will produce 1 kind of spore that will develop into a gametophyte that produces both antheridia & archegonia)
-have the underground stems called rhizomes

Question 16

life cycle of seedless vascular plants

Answer 16

-dominant sporophyte (2n) is much larger & longer lived than gametophyte (n)
-fern spores germinate -> protonema -> divides to form prothallium (gametophyte) -> rhizoids, male & female reproductive structures occur on prothallium underside
-as zygote grow to embryo it remains attached to the prothallus (embryonic plant depend on it for water & nutrients)
-rarely self fertilize bc antheridia & archegonia mature at different types (avoid inbreeding & self-fertilization)

Question 17

seedless vascular plants: pteridophyta (whisk ferns)

Answer 17

-no fossil record; find them only in the tropics
-theres 2 living (extant) groups: psilotum (widely distributed) & tmesipeteris (south pacific)
-they are morphologically very simple, don’t have the leaves & roots
-species gain a lot of nutrition from fungi that grow in association with their rhizomes (extensive underground stems)

Question 18

seedless vascular plants: pterophyta (horsetails)

Answer 18

-prominent in fossil record (some were giant)
-15 species
-have a brushy appearance (“scouring rush” colonially)
-only the stem is photosynthetic
-leaves are very tiny & they are nonphotosynthetic microphylls
-asexual reproduction occurs via fragmentation / extension of the rhizome)

Question 19

seedless vascular plants: lycophyta (club mosses)

Answer 19

-very old (300-400 mya)
-considered evergreen (don’t loose their leaves during the winter)
-live in a disiguious forest
-drop their leaves that conserves their energy
-most ancient plants lineage with roots (belowground stems)
-make up coal deposits
-have rhizomes (underground horizontal stems) where asexual reproduction occurs
-sporangia cluster in the strobili at tips of branches
-have unusual leaves (microphylls or lycophyll: leaf with 1 vein)
-believed to have common ancestry with cone-bearing plants (pine trees)