ferns (euphyllophytes)+ gymnosperms + lycophytes

week 3

what tissue do ferns+gymnosperms have that bryophtyes do not?

vascular tissue

what is vascular tissue?

consists of xylem and phloem, mean to transfer water, mineral, other nutrients throughout the plant

what are tracheophytes?

• Posses lignified cells for water conduction

• These are always tracheids

• Angiosperms have another water conducting cell type in addition to tracheids

what are tracheophytes?

what are lycophytes?

group of vascular plants

clubmosses

What pivotal steps in the early history of plant evolution contributed to the success of vascular plants in their occupation of the land?

• Ancient vascular plants gave rise to more specialized plants with more highly differentiated plant body → consist of roots (anchorage and absorption of water/minerals, acquisition of energy from sunlight)

• Gametophytic generation underwent progressive reduction in size and gradually became more protected and nutritionally dependent on sporophyte

• Seeds evolved, structures that a provide embryonic sporophyte with nutrients and help protect it from rigors of life on land

Explain the evolutionary origin of microphylls and megaphylls. Which groups of seedless vascular plants have microphylls? Which have megaphylls?

• Microphylls → usually relatively small leaves that contain only single strand of vascular tissue

  • Stems possessing protosteles and are characteristic of lycophyte

  • May have evolved as superficial lateral outgrowths of the stem or from sterilization of sporangia in lycophyte ancestors

  • Began as small scalelike or spinelike outgrowths, enations devoid of vascular tissue

• Megaphylls → larger than most microphylls (generally large leaf with several to many veins)

  • Evolved from entire branch systems by series of steps

  • Earliest plants had leafless, dichotomously branching axis

types of stele [vascular architecture]: protostele, siphonostele (leaf gap), siphonostele, eustele (no leaf gap)

type of stele in botany, form solid rod with phloem surrounding xylem, lacks central pith

has pith, multiple veins

characteristic of megaphyll

What is meant by homospory and heterospory? What are the contrasting features of the gametophytes produced by homosporous and heterosporous plants?

• Homosporous → vascular plant that produce only one kind of spore as a result of meiosis

  • Found in almost all ferns, horsetails, and some lycophytes

  • Potential to produce bisexual gametophytes (bear both sperm-producing antheridia and egg-producing archegonia)

  • sporangium borne by sporophyll

• Heterospory → production of two types of spores in two different kinds of sporangia

  • Found in some lycophytes, as well as few ferns and all seed plants

  • Microspores and megaspores → microspores give rise to male gametophytes and megaspores gives rise to female gametophytes

  • megsporangium

  • Produced in microsporangia and megasporangia

  • Heterosporous plants, gametophytes develop within spore wall 

Describe the characteristics of each of the following phyla of seedless vascular plants: Rhyniophyta, Zosterophyllophyta, Trimerophytophyta, Lycopodiophyta, and Monilophyta. Which of these are exclusively fossil phyla?

• Rhyniophyta: seedless plants, consist of simple dichotomously branching axes or stems, numerous lateral branches that arose from dichotomized axes

Describe the characteristics of each of the following phyla of seedless vascular plants: Rhyniophyta, Zosterophyllophyta, Trimerophytophyta, Lycopodiophyta, and Monilophyta. Which of these are exclusively fossil phyla?

• Zosterophyllophyta: leafless, dichotomously branched, aerial stems were covered with cuticle, lower branches frequently produced lateral branches, borne laterally on short stalks, homosporous

Describe the characteristics of each of the following phyla of seedless vascular plants: Rhyniophyta, Zosterophyllophyta, Trimerophytophyta, Lycopodiophyta, and Monilophyta. Which of these are exclusively fossil phyla?

• Trimerophytophyta: probably evolved directly from rhyniophytes, likely contains plants of diverse evolutionary relationships, generally larger and evolutionarily more specialized than rhyniophytes, trimerophytes

Describe the characteristics of each of the following phyla of seedless vascular plants: Rhyniophyta, Zosterophyllophyta, TrimIn eusporangia → parent cells or initials are located at surface of tissue from which sporangiumm is produced

• In many euphorangia, inner wall layers are stretched and compressed during course of development

• Much larger than laptosporangia, contain many more spores, characteristic of all vascular plants

• Leptosponrangia → aris from single superficial initial cellerophytophyta, Lycopodiophyta, and Monilophyta. Which of these are exclusively fossil phyla?

• Lycopodiophyta: all lycophytes are euaporangiate, most consist of branching rhizome

  • Club mosses

  • Selaginella

Describe the characteristics of each of the following phyla of seedless vascular plants: Rhyniophyta, Zosterophyllophyta, Trimerophytophyta, Lycopodiophyta, and Monilophyta. Which of these are exclusively fossil phyla?

• Moniophyta: comprise ferns [great majority] and horsetails, extensive fossil phyla

  • Ferns have two kinds of sporangia

    • Eusporangiate

    • leptosporangiate

In terms of their structure and method of development, how do eusporangia differ from leptosporangia?

• In eusporangia → arise from group of initial cells

  • parent cells or initials are located at surface of tissue from which sporangium is produced

    • In many euphorangia, inner wall layers are stretched and compressed during course of development

    • Much larger than laptosporangia, contain many more spores, characteristic of all vascular plants

    • Sporangium wall surrounds the spores

• Leptosporangia → arise from single superficial initial cell

  • smaller, simple structure

  • The annulus disperse the spores from within it

Which ferns are eusporangiate? Which are leptosporangiate?

• Eusporangiate: psilotopsida [ophioglossales and psilotales] and marattiopsida

• Leptosporangiate: most polypodiopsida

What is a seed, and why was the evolution of the seed such an important innovation for plants?

• Seed → matured ovule containing an embryo

• protected, nutrient supplied embryo

• limits reliance on water, resilient

• can be dispersed at long distances

• Production of seeds is extreme form of heterospory that is modified to form an ovule (structure that helps develop the seed)

According to the current hypothesis, from which group of plants did seed plants evolve? What is the evidence for this hypothesis?

seeds evolved from progymnosperms

evidence: structure called eustele that has vascular tissue in strands around a pith, bares strong similarity link to the now seed plants

How do the mechanisms by which sperm reach the eggs in gymnosperms and in seedless vascular plants differ?

for ferns and other seedless plants, water is NEEDED for sperm movement to reach egg

for gymnosperms, pollen grain is transferred through wind until hitting megagametophyte in ovule (pollination)

Give the distinguishing features of the four phyla of living gymnosperms.

coniferphyta: most numerous, needle like leaves

cycadophyta: large compound leaves (palm like), pollinate mainly by insects, roots form upwards, highly toxic compounds, unisex sporophytes

ginkgophyta: 1 extant species left, leaves shaped like thallus, unisex sporophytes

gnetophyta: most similar to angiosperms, unisexual sporophytes, shrubs and woody vines

In what ways do gnetophytes resemble angiosperms?

resemble angiosperms by having similar strobili (cone bearing structure), presence of vessels in xylem, lack archegonia in some genera

growth forms of early vascular plants

• Branching sporophytes (unlike sporophytes)

• Lack of leaves (but has vascular system)

• Include: rhyniophyte, zosterophyllophyte, and trimerophyte

• Ancestral or outgroup to: all tracheophytes, lycophytes, monilophytes, gymnosperms and angiosperms

• Asymmetric branching will be important for the evolution of leaves

what do lycophytes, ferns, and bryophytes have in common?

they all rely on water for fertilization (sperm needs to swim to get to female)

alternation of generations

spore based reproduction

fern anatomy

Pinnules, turn over and see the sori on the other side

fern cycle

Meiosis occurs → annulus releases the spores → germinates → begin to form gametophyte → mature gametophytes (archegonium clumped together and antheridium spread more of everywhere)

Egg fertilizes → zygote → young embryo → create embryo → full grown sporophyte (the dominate above ground plant seen)

gymnosperm examples

• Conifers

• Cycads

• Ginkgo

• Gnetophytes 

plant examples of homospory

bryophytes, most lycophytes, monilophytes —> develop bisexual gamete (produce both sperm and eggs)

produce spores of similar shape and size

plant examples of heterospory

seed plants (angiosperms and ggymnosperms), selaginella, certain ferns

how are gymnosperm megaspores and megagametophytes different from those of ferns?

gymnosperms: mega → ovules in female cones, one of four megaspores survives and develops into megagametophyte

^produce archegonia, containing egg cells

ferns: produce specialized structures, sporangia, found on underside of fronds

megaspores

spores that will develop into female gametophytes, producing egg cells

megagametophyte

female gametophytes that develop from megaspores

what type of plants have megaspores and megagametophytes?

heterosporous plants [meaning the spore production of two different sizes and sexes by sporophytes of land plants]

what gamete do heterospory plants produce?

produce separate male and female gametophytes (2 gametophytes while bisexual gametophytes are only one gametophyte but can produce both types of gametes)

what are archegonia and antheridia? what type of plants have archegonia and antheridia?

archegonia: female reproductive structures, typically flask-shaped and contain egg cell

antheridia: male reproductive structures, small spherical, release sperm when mature and swim to archegonia to fertilize egg

bryophytes, ferns, lycophytes

gymnosperms have archegonia (but not antheridia), bc male gametophyte is pollen, produces directly without forming antheridia