Lab Final

Question 1

What is the dominant phase of the fern life cycle?

Answer 1

Sporophyte.

Question 2

What is the defining external morphology of ferns?

Answer 2

Ferns have fronds that are often large to capture as much light as possible in the understory. Fronds are arranged spirally on the underground stem or rhizome.

Question 3

What are sori?

Answer 3

Clusters of sporangia found on the underside of fronds.

Question 4

What are the three types of fern stem morphology?

Answer 4

1. Creeping (large distance between fronds which are arranged spirally on subterranean rhizomes or aboveground stems).
2. Compact (stems located almost entirely below ground, with fronds arranged in very tight spirals).
3. Erect (found in tree ferns, most of the stem is aboveground, often very tall, leaves arranged in tight spiral but are only present at the top of the plant and shed lower leaves).

Question 5

What are the stelar morphologies found in ferns?

Answer 5

Siphonosteles or dictyosteles.

Question 6

What are the three major parts of fern fronds?

Answer 6

1. Petiole or stipe (stem to leave transition).
2. Rachis (backbone of leaf and main vascular strand).
3. Blade.

Question 7

What are immature fern fronds called?

Answer 7

Fiddleheads or croziers.

Question 8

Are ferns monomorphic or dimorphic?

Answer 8

Most ferns are monomorphic (containing sporophylls), but some are dimorphic (separate fertile and vegetative leaves). Some are dimorphic within a single frond (fertile and vegetative regions).

Question 9

What are the three main venation patterns seen in fern fronds?

Answer 9

1. Open-dichotomous (ancestral condition, veins don’t rejoin at the ends).
2. Reticulate (characteristic of most ferns and dicots, abundant branching and joining of vascular tissue).
3. Striate/parallel (found mainly in monocots, very long veins connected at regular intervals in a ladder-like arrangement).

Question 10

How do ferns reproduce?

Answer 10

Fern sporophytes produce spores in sporangia that are either arranged in spikes or clustered together in sori. Most ferns are homosporous, other than water ferns.

Question 11

What are the two types of ferns?

Answer 11

1. Eusporangiate (ancestral condition).
2. Leptosporangiate (more recently evolved, presence of sori).

Question 12

What does it mean if a fern is eusporangiate?

Answer 12

Eusporangia are produced from many cell divisions, are much larger than leptosporangia, and produce more spores. These ferns don’t form sori and instead have eusporangia on fertile fronds that release spores through slits at the end of the eusporangium.

Question 13

What does it mean if a fern is leptosporangiate?

Answer 13

Leptosporangia are produced from single cells and have a thin layer of tapetal cells. Spores are released through a specialized ejection mechanism (whip). These ferns form sori.

Question 14

What do the terms marginal, veinal, and inter-veinal mean regarding sori?

Answer 14

Where on the leaf they occur.

Question 15

What is an indusium?

Answer 15

Piece of specialized tissue that covers sori for protection while the sporangia are maturing.

Question 16

What are the types of indusium?

Answer 16

1. False indusium (leaf margin folds over the sori, typically marginal/linear sori, ancestral condition).
2. True indusium (most prevalent, separate umbrella or cup shaped outgrowth from the leaf surface).
3. Ex-indusium (most evolutionarily advanced, circular sori, no indusium).

Question 17

How can you distinguish between indusiate and ex-indusiate ferns?

Answer 17

Since the indusium is shed at sporangial maturity, if there is no indusium and the spores have still not been released, the fern is ex-indusiate. If there is no indusium and the spores have been released, it is hard to know.

Question 18

What are the main features of Osmunda ferns?

Answer 18

Intermediate between eusporangiate and leptosporangiate. Hemidimorphic.

Question 19

What is the purpose of the annulus structure in leptosporangiates?

Answer 19

Cells of the annulus contract as the sporangium dries out, eventually ripping apart the sporangium wall and ejecting the spores (similar to chuck it whip motion).

Question 20

What is different about heterosporous ferns?

Answer 20

Produce their sporangia in sporocarps, which open upon hydration and extend a sorophore branch with indusiate sori attached (containing both micro and megaspores).

Question 21

What type of fern is Marsilea?

Answer 21

Heterosporous leptosporangiate.

Question 22

What is the fern gametophyte called?

Answer 22

Prothallus.

Question 23

What is the difference between homothallic and heterothallic prothalluses?

Answer 23

Homothallic means male and female organs are located on the same gametophyte (ie. monoecious). Heterothallic means male and female organs grow on separate gametophytes (ie. dioecious).

Question 24

What type of prothallus is most common?

Answer 24

Most fern gametophytes are homothallic, but have evolved to be protogynous (archegonia mature before antheridia) to prevent self-fertilization.

Question 25

What is the characteristic shape of most prothalluses and where are archegonia and antheridia located?

Answer 25

Heart-shaped, with archegonia in the notch region and antheridia underneath the pointed ends.

Question 26

What occurs following fertilization of fern eggs?

Answer 26

The new sporophyte begins to grow and is retained on the gametophyte until several leaves and roots have grown. The zygote undergoes many divisions within the archegonia to produce the first tissues. The development of the foot is essential (acts like umbilical cord to gametophyte).

Question 27

What groups are included in gymnosperms?

Answer 27

Cycadophyta, Ginkgophyta, Coniferophyta, and Gnetophyta.

Question 28

How are gymnosperm seeds different from angiosperm seeds?

Answer 28

Gymnosperms have "naked seeds" that have no protective structure/fruit and receive pollen directly on the unfertilized ovule. Angiosperm seeds are protected and have the pollen first deposited on the stigma of the flower.

Question 29

What is the external morphology of cycads?

Answer 29

Vegetative sporophyte is very similar to ferns, with spiral leaves at the top that are replaced every year. The trunk grows in size every year in most species. Stem is typically erect and non-branching. Small amount of secondary growth of vascular tissue in many species.

Question 30

What type of stele(s) are found in Cycas?

Answer 30

Siphonostele in stem. Eustele or atactostele in petiole.

Question 31

Are cycads monoecious or dioecious?

Answer 31

Strictly dioecious. Pollen produced by microsporangiate male strobili. Seeds produced by megasporangiate female strobili.

Question 32

What are the features of cycad pollen?

Answer 32

Large amounts of pollen spores are found in microsporangia on the lower surface of microsporophylls. Multicellular (3-6 cells). At least one prothallial cell. Tube cell produces the pollen tube for delivering to the archegonial chamber. Generative cell divides to form stalk cell (vegetative tissue) and body cell (flagellated sperm).

Question 33

What is the morphology of cycad megasporangia?

Answer 33

Most cycads have tightly packed cones. Developing ovules on megasporophylls with peltate shape. Some species have dissected megasporophylls (much more open).

Question 34

What external features differentiate microsporangiate and megasporangiate cycad cones?

Answer 34

Microsporangiate cones are small and narrow, more numerous on microsporophylls, and lighter in colour due to the presence of pollen. Megasporangiate cones are big and broad, peltate and darker in appearance.

Question 35

What were the requirements for seed evolution?

Answer 35

1. Evolution of heterospory. 2. Reduction in size of gametophyte phases. 3. Reduction in megaspore mother cells to one. 4. Survival of only one megaspore. 5. Evolution of endospory and retention of megaspore on the sporophyte. 6. Formation of protective integuments surrounding the developing megasporangium. 7. Embryo retention.

Question 36

How is the seed an extreme example of heterospory?

Answer 36

Seed plants produce only one functional megaspore contained within the ovule surrounded by an integument layer for protection and micropyle opening.

Question 37

How are gymnosperms similar to seedless vascular plants?

Answer 37

Female gametophyte still produces archegonia within the ovule.

Question 38

How does fertilization occur in gymnosperms?

Answer 38

Wind or animals transfer pollen from microsporangiate cones to the micropylar end of megasporangiate cones, then the tube cell grows through the nucellus towards the archegonia, and the body cell undergoes a division to produce two sperm that are released into the archegonial chamber, then they swim towards archegonia.

Question 39

What is the free nuclear stage of seed development?

Answer 39

Zygote divides rapidly following fertilization without the formation of cell walls, so the zygote is coenocytic for a while before pushing into the megagametophyte tissue.

Question 40

What is the nucellus?

Answer 40

Nutritive tissue in gymnosperm seeds.

Question 41

What is the external morphology of ginkgo trees?

Answer 41

Can grow very tall, have two types of shoots (long and stubby), primitive venation pattern, dioecious, seed develppment similar to cycads.

Question 42

What genera are included in Gnetophyta?

Answer 42

Gnetum, Ephedra, and Welwitschia.

Question 43

What are the important features of Gnetophyte cones?

Answer 43

Female cones look a lot like flowers, develop colour/bigger/look like berries. Ovules are considered intermediate between gymnosperms and angiosperms because they have 2 integuments instead of 3 (consistent with flowering plants). Very few ovules grow to maturity.

Question 44

How does the vascular system of Gnetophytes differ from other gymnosperms?

Answer 44

Have tracheids and vessels, which shows they are intermediate species between gymnosperms and flowering plants.

Question 45

What type of leaves are needles?

Answer 45

Megaphylls.

Question 46

How do needles withstand periods of drought and cold?

Answer 46

Thick waxy cuticle. Sunken stomata to prevent evaporative water loss. Hypodermis provides additional support and protection. Resin ducts protect from herbivores. One or two vascular bundles running through them.

Question 47

How many needles are found in different conifers?

Answer 47

Pines 2-3. Spruce single. Larch tons. Hemlock single.