Adaptations to Life on Land, the Evolution of Land, Non-Vascular, and Vascular Plants, and Classifying Vascular Plants

What are the two specific kinds of mosses?

sphagnum (peat mosses) and dung mosses

What keeps the land plant's spores from drying out?

-spores have thick spore walls containing sporopollenin, a polymer that resists decay and keeps spores from drying out -spores swimming in aquatic environments do not have thick sporopollenin walls

How have vascular plants completely transformed the world (2)?

-they have structure, so they can grow tall: some of the early vascular plants were huge, treelike structures that grew to be enormous, their vascular tissue (lignin-rich tracheids) allowed for vertical growth -they could live in drier habitats: true organs, especially roots, allowed plants to disperse to areas that weren't wet, which allowed animals to move onto land because plants provided a food source for them

Why was further diversification of bryophytes needed for land plants?

bryophytes were the first plants to transition to life on land, have signaling proteins and genetic information that helped them avoid desiccation on land, but have drawbacks that prevented them from thriving on land

What are hydroids?

cells in moss that die and leave channels through which water can move

What are the 11 major groups of land plants?

liverworts, mosses, hornworts, lycophytes, horsetails, leptosporangiate ferns, cycads, gingko, gnetophytes, conifers, and flowering plants -most ancient are non-vascular

What are the synapomorphies associated with lycophytes?

microphylls, independent sporophyte, strobili

What are elaters?

grow alongside the spores in the sporophyte, assist in dispersal of spores and are very sensitive to changes in humidity -in liverworts

What are the 3 groups of euphyllophytes?

monilophytes (horsetails and ferns), gymnosperms, and angiosperms -ferns, horsetails, and lycophytes were dominant during the Carboniferoud period about 300-350 MYA, now angiosperms dominate plant world

What are different species of ferns that do not look like ferns (3)?

-Marsilea ferns look like 4-leaf clovers -Salvinia is an invasive aquatic species known to clog waterways in Florida and other places, do not look like ferns but DNA testing reveals they are -tree ferns of the genus Libotium are large and look like trees, but lack wood and can only grow higher, in Gainesville and Miami

What is the liverwort cryptothallus?

-a thalloid liverwort that is not photosynthetic and has a white appearance, primarily grows under soil and extends long seta in a spaghetti like appearance above the soil -is a parasite: steals nutrients from mushroom-producing (basidiomycete) fungus that forms a mycorrhizal relationship with birch and pine trees in Europe (also steals the nutrients from the tree) -has the genes it needs to make chlorophyll, but does not

What is the perianth?

-all leafy and some thalloid liverworts have a specialized structure called the perianth in which archegonia are produced -some thalloid have specialized structures that look like palm trees or umbrellas, where archegonia and antheridia are produced

What are gemmae?

-asexual structures, tiny pieces of liverwort -gemmae are in thalloid and leafy liverworts, exist in gemma cups for thalloid and found alongside the margins of the gametophyte in leafy

What are the embryos of land plants and how are they protected/nourished?

-embryos are tiny diploid plants initially surrounded and nourished by cells of the gametophyte (why land plants are called embryophytes) -a diploid zygote forms when sperm make their way down the archegonium by swimming or being splashed there -the gametes fuse together and form a zygote that will divide and become the embryo, which will initially be housed and nourished in the gametangium of the gametophye, but will eventually grow into a multicellular sporophyte -this initial protection and nourishment of the embryo makes it more likely that the young plant will develop fully and survive

What are the monilophytes?

-ferns and horsetails, which share a similar life cycle and have a larger, more complex, and longer-lived sporophyte than non-vascular plants -refer to leptosporangiate ferns (form a clade)

What is the role of the annulus and lip cells in ferns?

-ferns forcibly eject, or fling, the spores out of the sporangia, which is facilitated by a layer of asymmetrically thickened cells called the annulus, which exists opposite to another group of thin-walled cells called lip cells -as spores develop, the sporangium swells and when enough moisture is in the air, the lip cells burst open, the top of the sporangium flings back and the annulus allows the sporangium to open while anchoring the bottom portion in place, the spores are then forcefully ejected

What are the multicellular gametangia of land plants?

-gametangia are multicellular organs in which gametes are produced and are advantageous because they protect the egg and sperm from drying out (versus chloroplasts, that rely on the cellulose wall to avoid desiccation) -archegonia are female gametangia which produce eggs via mitosis and serve as fertilization site -antheridia are male gametangia which produce sperm with 2 subtropical whiplash flagella via mitosis (the sperm must swim to archegonium to engage in fertilization)

Why do vascular plants have life cycles dominated by the diploid sporophyte, unlike non-vascular plants?

-genetic advantages of diploidy: diploid individuals can hide recessive deleterious gene (because they have 2 versions of each gene), whereas haploid can't (only 1 version) -genetic variation: diploid sporophyte can produce sporangia that can produce millions of genetically unique spores via meiosis with different combinations of genes, can be advantageous in changing environment -these adaptations help scientists define and classify the monophyletic group of land plants and can further divide the group into 11 major groups

What are dung mosses?

-grow on dung and decaying animal flesh, grow mostly in polar climates -often come into contact with flies, they make sticky spores that attach to little landing pads for flies -when a fly lands on one of the pads, the spores attach to it and the fly takes the spores with it when it visits a new pile of dung or new carcass -demonstrates that plants often rely on other organisms to ensure their survival and dispersal

What are the components of the lycophyte's sporophyte?

-has roots, leaves, and sporangia that produces spores via meiosis -sporangia are sometimes nestled in the base of microphyll, other times, they are produced on specialized areas of the stem without microphylls -when sporangia exist outside of microphylls, they form cup-like structures called strobili on stems and branches, this formation is why lycophytes are called club mosses (not true mosses, which are non-vascular)

How is the sporophyte different in vascular plants than in bryophytes?

-in bryophytes, the sporophyte is unbranched and nutritionally dependent on the gametophyte -tracheophytes have branched sporophytes independent of the gametophyte at maturity and branch dichotomously -they also have apical meristems at the end of each branch and the xylem in the lignified stalk provides the internal support necessary to hold the branches up, which allows more surface area for spore production

What is overtopping growth?

-in euphyllophytes, one branch differentiates from others and grows on top of them -allowed them to better compete for light and grow taller

What are multiflagellate sperm?

-in euphyllophytes, sperm have multiple flagella, providing an evolutionary advantage because it allows them to more easily fertilize eggs -multi means they have more than 2 flagella, unlike plants that are diflagellate that have only 2

What are mosses?

-next land plants/bryophytes to emerge after liverworts, consist of small plants with erect, leafy gametophytes, do have stomata (unlike liverworts) -most transport water externally by capillary action (must live in moist habitats) -have around 15,000 extant species -like in liverworts, the sporophytes are attached to gametophytes and are dependent on the gametophyte for protection and nutrition and sporophyte contains a capsule connected to the gametophyte via a seta

___________ is a process that creates clones (exact copies) of parent cell, while ____________ is a process that creates daughter cells with half of the DNA content of the parent cell. A ___________ cell has only 1 copy of each chromosome, and a __________ cell has 2 copies.

Mitosis, meiosis, haploid, diploid

What is the function of the stem in tracheophytes?

support the plant, elevating leaves and spreading them out to promote maximum surface area for light capture and rates of photosynthesis

Why did land plants have to adapt to the land environment (8)?

the sun has harmful UV rays and extremely dry conditions -adaptations included the cuticle, stomata, multicellular gametangia, protected and nourished embryos, UV-absorptive pigments, thick spore walls, mutualistic associations with fungi, and alternation of generations

What allows bryophytes to live on dead trees, bare rocks, and buildings?

their mutualistic associations with fungi, which date back to at least 460 MYA (suggesting fungi played a crucial role in transition to land)

Why are bryophytes different than many other land plant groups?

they have unbranched sporophytes with a single sporangia

What does bryophyte reproduction require?

-a lot of water, which is a disadvantage compared to angiosperms, that can spread further with their use of pollen and seeds, not spores -angiosperms are more successful than nonvascular plants, which are hard to find in nature

What is a trend in the evolution of land plants involving their life cycle?

-a movement from life cycle dominated by haploid form to one dominated by diploid form -non-vascular plants' life cycles are dominated by haploid gametophyte, while vascular plants have life cycles dominated by diploid sporophyte

What is the role of the xylem in vascular plants? the phloem?

-xylem: brings water and nutrients from roots to top of plants -phloem: takes sugars from photosynthetic parts of plant (sources) to parts of the plant that need them (sinks)

What are sphagnum (peat mosses)?

-ancient moss lineage with unique appearance -has branches that grow in whorls that look like pom-poms -grow in swamp-like conditions and acidify water in bogs where they are found, which helps slow down the rate of decay of dead life forms that fall into the bog -also play a role in carbon storage: because it grows in layers and does not decay, all of the carbon that has been incorporated into the plant body remains trapped in deposits of peat moss, which keeps CO2 from being released back into the atmosphere -a lot of potential energy is stored in peat bogs and sphagnum is sometimes burned as fuel -also is very absorbent and used for gardening

What is the structure of the sporophyte of liverworts?

-attached to and physiologically dependent on gametophyte -has a stalk (or seta) and capsule, where haploid spores are produced in sporangium via meiosis -cell elongations throughout the length of the stalk cause the stalk to grow, extending the sporangia in the air

What is the typical fern life cycle?

-begins with a mature sporophyte with sori (clusters of sporangia) on the underside of its leaves -the sporangia releases spores, which germinate and grow to become a mature gametophyte -the antheridium produces sperm and the archegonium produces eggs -fertilization of the egg by the sperm leads to a zygote, which divides to become a developing embryo that grows into a sporophyte, which matures and is independent of the gametophyte and the life cycle is complete

What is the life cycle of the bryophytes?

-begins with the release of a spore from the sporangium, the sporangium forms a capsule that eventually desiccates and explosively splits, throwing spores as far as 2 feet away from the plant -this allows the gamete to occupy a territorial niche with no competitors -once the spore comes in contact with water, it germinates, forms a bud, and turns into either a multicellular haploid male or female gametophyte, which is anchored in placed by rhizoids (specialized root-like tissue) -when the gametophyte receives the appropriate signal, it forms the gametes needed for reproduction via mitosis, males form flagellated sperm in their antheridia, females form eggs in archegonia -the motile sperm splashes or swims in water until it reaches the archegonium, where fertilization takes place, the fertilized egg is a diploid zygote, which divides to form an embryo -the embryo grows up, forming a young sporophyte that continues to grow and eventually produce spores of its own -in its earliest stages, the sporophyte exists as a threadlike chain of cells called the protonema

What are lycophytes?

-club mosses, sister group to remaining vascular plants (the euphyllophytes), about 1200 species, small plants -have an extensive fossil record, showing they were much more prevalent before versus today -ones that exist today are much smaller than those that existed millions of years ago, which is common in evolution where larger forms of a group of organisms are often not the ones that end up surviving -the spores of lycophytes are used commercially: photography, movie explosions, lycopodium powder to coat latex gloves

What are ferns?

-contain sporangia on both their leaves and modified leaves, have leptosporangia (sporangia arisen from a single epidermal cell) -are stalked and have a thin wall, their outer rims have a single row of specialized cells called the annulus, which assists in spore dispersal -more than 15,000 species of ferns with a variety of shapes, sizes, and living environments -like lycophytes, have independent sporophyte and gametophyte generations (and the sporophyte generation is dominant and can live for hundreds of years)

Are ferns and horsetails heterosporous or homosporous?

-early vascular plants, like horsetails and ferns, had 1 kind of sporangium that produced 1 type of spore, which developed into a gametophyte that produced both male and female reproductive organs -they are homosporous because they produce 1 spore type

What pigments did land plants evolve to protect against the sun's radiation?

-evolved UV-absorptive pigments that protect against ultraviolet radiation, one of the most significant challenges to living on land -they absorb certain wavelengths of light and dissipate excess radiation, collectively called accessory pigments

What is our source of coal on the Earth today?

-huge, treelike structures that dominated during the Devonian and Carboniferous periods were not true trees because they lacked wood, when these organisms died, their biomass was eventually converted to coal -these organisms are very dominant, we get so much of our energy from remains of ancient trees that have been extinct for millions of years

What are megaphylls?

-in euphyllophytes, overtopping growth allowed for the evolution of new, more complex leaves with many veins called a megaphyll, which evolved from a flattened portion of a branching stem system with overtopping growth -are modified branches with terminal sporangia on the leaf surface, so ovules in many euphyllophytes are born on their leaves -provide plants with evolutionary advantage because they spread out the photosynthetic surface (increasing surface area increases the rates of photosynthesis)

What are gemma cups?

-in liverworts, structures where gemmae are made -when a raindrop splashes in the cup, the gemmae splash out, land around the plant, and grow into a genetically identical individual to the gametophyte, a method of asexual reproduction and dispersion -the ability to reproduce asexually was an important feature in the colonization of land

What are microphylls?

-in lycophytes, small, flat leaves with a single midvein and are photosynthetic -natural selection may have favored their development because they are positioned horizontally, allowing more surface area for collection of sunlight and they also have thin cells, which allows sunlight to penetrate into photosynthetic cells below the surface -many have evolved from lateral sporangia (spore-bearing structures located along the stem of the plant) -a particular genus of lycophytes (Selaginella) have sporangia that lie along the stem and are often used as house plants and are at garden stores

What is the function of sieve cells and phloem found in vascular plants?

-internal conduction of sucrose, in the phloem -phloem is the living tissue that distributes sugars, amino acids, and other important organic products throughout the plant and is thought to have developed later than the xylem over evolutionary time -xylem and phloem flow occur in opposite directions (xylem is from root upward and phloem is from leaves downward, but can go in other directions)

What is the function of tracheids in vascular plants?

-internal conduction of water, in the xylem -are elongated, ornamented, thick-walled cells in xylem tissues that conduct water, not alive at maturity -these vessels have tough, thick walls strengthened by lignin (complex polymer) to support plants as they grow vertically -their elongated structure allows them to conduct water efficiently: water flows from cell, passing through small pits in cell walls of tracheids

What are the roots in vascular plants?

-involved in absorption of water and minerals -xylem begins at the roots and takes water upward through the plant to the leaves and stems -most water absorption occurs via root hairs, tiny extensions that increase the surface area for absorption -the root grows downward into the ground via the root tip, the primary area of growth

What occurs in the alternation of generations of land plants?

-is a synapomorphy of all land plants, in which there are 2 different forms, a multicellular diploid (2n) form (the sporophyte) and a multicellular haploid (n) form (the gametophyte) -to reproduce, the sporophyte produces haploid spores through meiosis in a specialized structure called the sporangium, those spores germinate and divide mitotically, forming the haploid gametophyte -through mitosis, the male gametophyte produces the sperm and female gametophyte produces the egg (gametes are produced in protective structures called gametangia: antheridium and archegonium) -when the gametes fuse in fertilization, a diploid zygote is formed, the zygote divides via mitosis, forming an embryo, which remains in the tissue of the female gametophyte -placental transfer cells mediate the transfer of nutrients from parent to embryo and the sporophyte develops, process continues -in humans, gametes are created via meiosis, in plants, they are created via mitosis, genetic recombination occurs during crossing over in meiosis I

What are the groups of euphyllophytes and what are their characteristics?

-is a true leaf plant (has megaphylls), includes all vascular plants except lycophytes: horsetails, ferns, gymnosperms, and angiosperms -the monilophytes (horsetails and ferns) are a sister lineage to the seed plants (gymnosperms and angiosperms) -the seed plants are the most recent group of euphyllophytes to emerge -has multiflagellate sperm, endogenous branching, overtopping growth, and megaphylls

What do bryophytes, non-vascular plants, lack and what does this cause?

-lack true organs (roots, stems, and leaves) and vascular tissue (xylem and phloem) -they have to rely on osmosis and diffusion to get water and other nutrients to their cells -also have swimming sperm with 2 flagella and require water for fertilization (most bryophytes live in moist environments)

What is the function of the land plant's cuticle?

-land plants protected themselves from water loss by developing a coating of waxy lipids (cuticle) made out of cutin and other waxy polymers -the coating traps water and protects it against evaporation, typically on both top and bottom of plant's leaves

What are the structures of a fern?

-leaf of a fern is a frond, attached to the ground via leaf stalk called stipe -stem and roots are underground and their leaves can have many different shapes, ferns have young, coiled leaves called fiddleheads and large megaphyll leaves where sporangia are born -the underside have small clusters of bumps called sori (sorus), which are thought to have evolved through the webbing or sporangia and are often covered by an indusium, a flap of green tissue that protect the sori

What is the life cycle of green algae (coleochaete and chara)?

-life cycle dominated by haploid phase and the vegetative bodies are haploid -produce gametes through mitosis, when gametes fuse in fertilization, they produce a diploid zygote that immediately undergoes meiosis, producing 4 haploid spores (land plants evolved to have multicellular haploid forms- gametophyte and multicellular diploid forms- sporophyte)

What are epiphytic bryophytes?

-live on other plants -ex. tree covered with bryophytes in temperate rainforest biome: bryophytes can't grow to be tall because they lack vascular tissue -living on top of other plants is one way for them to gain access to sunlight and protection from things on the ground -not parasites (do not derive nutrition at expense of host)

What are the 2 categories of vascular plants?

-lycophytes (club mosses) with microphylls -euphyllophytes (everything else) with megaphylls

What are vascular plants?

-monophyletic group of plants that forms the largest and most important clade of land plants, have vascular tissue (xylem and phloem) -AKA tracheophytes (these and the bryophytes make up all the land plants) -include lycophytes, horsetails, leptosporangiate ferns, cycads, gingko, gnetophytes, conifers, and flowering plants

Are seed plants homosporous or heterosporous?

-more complex plants (seed plants) developed heterospory: a reproductive strategy in which 1 type of spore (microspore) develops into the male microgametophyte and another type of spore (megaspore) develops into the female megagametophyte -involves the production of 2 kinds of sporangia (megasporangia, which give rise to megaspores, and microsporangia, which give rise to microspores), the microspore is much smaller than the megaspore -the megagametophyte produces archegonia (contains the egg) and the microgametophyte produces antheridia (contains sperm), so heterosporous plants have unisexual gametophytes

What helps the earliest plants acquire the water and minerals needed to survive on land?

-mycorrhizae: mutualistic associations between fungi and underground plant structures (usually roots) -the filamentous fungi gather minerals and water from soil and bring it back to the plant in exchange for products of photosynthesis (glucose) -the fungi expand the surface area of the roots, making them more efficient at acquiring water and minerals -fungi can either form a sheath outside root's surface or extend into roots themselves -the earliest evidence of this dates back to time when plants were making transition to land

What is the function of the stomata?

-openings through which plants can exchange gases (O2 and CO2) with the outside environment -can open and close based on plant's needs and environmental conditions, primarily located on underside of leaf, majority of land plants have stomata, some don't -the first land plants probably did not have stomata, but they emerged fairly early on in evolution of land plants

How did the reproductive mechanisms of land plants evolve to help them adapt and thrive in their environment?

-reproductive mechanisms that do not depend as heavily on water for fertilization -pollen are small male gametophytes that are compact enough that they can travel through air, are transferred to female reproductive structures through air or by animals

What are horsetails?

-sister plants to ferns and evolved before them, not many still in existence, sometimes called by their genus name, Equisetum, look like tails of horses, in wet habitats -their non-photosynthetic, reduced leaves form distinct circles around the stem and have irregular branching roots, also have hollow stems with continuous ridges where silica (tough, hard substance) is embedded (may be an adaptation to prevent against herbivory) -their sporangia are produced in large strobili at the top of the plant -sometimes called "scouring rushes" because their strobili-containing strands can be used like a scrub brush to scour a pan

Are the species of mosses and liverworts monoecious or dioecious?

-some are monoecious (male and female organs on same individual) -some are dioecious (male and female organs on different individuals)

What are liverworts that are exceptions regarding living in moist habitats?

-some desert-dwelling conserve water by shutting down their metabolism during dry times and only reproducing when it becomes moist -some more advanced have flat photosynthetic lobes resembling leaves

What are structures relating to moss sporophytes?

-some have a cap-like structure on the distal end called the operculum -the unbranched sporophyte produces a single capsule lined with peristome teeth (like elaters in liverworts) that increase efficiency of spore dispersal -peristome teeth are hygroscopic, meaning they change shape as humidity changes and have a specialized structure that allows spores to be discharged gradually, rather than releasing all spores at once

How did partnerships with land animals promote the growth and reproduction of land plants?

-some plants developed flowers and fruits, which attracted animals -the development of flowers and fruits is associated with the huge diversification of animal life -flowers have pleasant fragrances or bright colors to attract animals -fruits have sweet taste, when an animal eats a fruit, it takes the seed with it and eventually releases them in its excrement, which helps plant species spread to new habitats

What is the dominant stage in bryophytes?

-spend most of their time in haploid gametophyte stage, their dominant stage -their gametophytes are typically larger and live longer than sporophytes, but do not have any strong supportive tissue -the sporophytes are typically dependent on the gametophyte for nutrition in some developmental stages

What are hornworts?

-the 3rd and last bryophyte, only 100 living species, their green sporophytes look like small horns -have the largest and most independent sporophyte of the bryophytes -their cells only contain 1 chloroplast -sporophyte is capable of indefinite cell division (can grow indefinitely) -have symbiotic relationships with nitrogen-fixing cyanobacteria that live in their internal cavities

What are liverworts?

-the most ancient bryophyte, their sporophyte is dependent on the larger gametophyte, which remains attached to and grows directly on the gametophyte -is a diverse group with more than 9,000 species, easy to miss, gametophyte body is either flattened (thalloid) or leafy -do not have true leaves (lack true organs) or true roots, but have rhizoids, extensions of the plant body that anchor wherever it grows -can't conduct water and have no vascular tissue, so they get water from soil and air and typically live in moist habitats -do not have stomata and use air pores to exchange gases with the enivornment

Are the sporophytes of lycophytes independent or dependent on the gametophyte?

-they have an independent sporophyte, which is the dominant structure in early tracheophytes (unlike bryophytes) -with the introduction of a branched sporophyte came the dominance of the sporophyte generation In tracheophytes -the gametophyte is extremely reduced, but still has the antheridia and archegonia, and can live independently of the sporophyte

What is the structure of roots in euphyllophytes?

-they have roots with endogenous branching, complex branching patterns -unlike lycophytes with dichotomously branched roots

What are drawbacks of bryophytes that prevented them from thriving on land?

-they relied on osmosis to get water to their tissues -they have swimming sperm, so they required water for fertilization -their gametophytes lacked strong supportive tissues -this all limited the range of earliest land plants and they could not grow tall because they had no supportive tissue or ways to get nutrients to tip of plant and could only live in moist environments

What are the major synapomorphies of tracheophytes that distinguish them from bryophytes?

-tracheids in xylem, sieve cells in phloem -branched, independent sporophyte -true organs (roots, leaves, stems)

What is the function of the leaves in tracheophytes?

-use photosynthesis to produce sugars, phloem begins here and takes sugars down to stem and roots (roots are underground, sunlight does not penetrate the ground, so the roots are dependent on other portions of the plant for sugars) -inside of the leave consists of many cells loosely packed together to allow chlorophyll-containing cells to access CO2 they need to perform photosynthesis -also have veins (bundles of xylem and phloem, or vascular tissue) that extend from the leaf to the rest of the plant -leaves are covered with a waxy cuticle that prevents them from water loss (thinner in bryophytes) and have stomata, small openings in the leaf where gases are exchanged

What adaptations did the earliest land plants develop to thrive?

-vascular tissue -new reproductive mechanisms -partnerships with land animals

How did vascular tissue help land plants adapt to their environment better?

-vascular tissue assists in the movement of water and sugars -includes the xylem and phloem, the pipes through which water and sugars flow throughout plant

What does the xylem have in flowering plants, besides tracheids?

-vessel elements that stack end to end to form xylem vessels even more efficient than tracheids at transporting water -are an evolutionary innovation of flowering plants, not present in other vascular plants

What were the first land plants to evolve?

bryophytes, a paraphyletic group of land plants consisting of non-vascular, herbaceous plants (liverworts, mosses, and hornworts) -not a clade because does not include all descendants of common ancestor

What is the seta in a bryophyte?

the capsule formed from the sporangium is connected to the gametophyte via a stalky part of sporophyte called the seta

What are the moss reproductive structures?

the perigonium (groups of antheridia) and the perichaetium (groups of archegonia), no special structures

What are the true plant organs in tracheophytes?

while bryophytes have to live very near to the ground, vascular plants have true plant organs (roots, leaves, stems)