Biology 1424 Lecture Exam 4 Notes

**Refer to the lecture slides, text and lab activities for pictures and illustration as well as more detailed information. The notes are a good review, but are not designed to substitute for the text and lecture.  When used in combination with the text and lecture they should be very useful.

CHAPTER 20: BRYOPHYTES NOTES

1.   The term bryophyte does not represent a taxon, but is a general term, which applies to all non-vascular land plants.

2.   Non vascular plants do not have xylem or phloem tissue.  Non vascular land plants such as mosses and liverworts have transport tissues, but they are not as advanced in their structure and are not as efficient as true xylem and phloem tissue.  These tissues are hydroids for the transport of water and leptoids for the transport of foods.  The lack of true  vascular tissue places limits on the size and distribution of bryophytes.  Bryophytes are usually limited to moist often shaded habitats.  They are not able to fully exploit the terrestrial environment as do vascular plants.

3.   The gametophyte is the dominant generation in the bryophyte lifecycle while the sporophyte is less dominant and is dependent upon the gametophyte for its survival. Haploid spores are the first cells of the gametophyte generation.  All cells of the gametophyte generation are haploid. Spores germinate producing a filamentous growth, the protonema, which produces buds that develop into gametophyte plants. Mature female gametophytes produce a single haploid egg in the archegonium while male gametophytes produce numerous sperm in the antheridium.  Sperm are released into water on the surface of the plant and swim to the archegonium where the egg is fertilized.  The fertilized egg (zygote) is the first cell of the sporophyte generation.  All cells of the sporophyte generation are diploid. The fertilized egg (sporophyte) receives all its nourishment from the gametophyte plant as it develops and matures. As the zygote grows and matures it develops a spore producing structure the sporangium.  At maturity meiosis occurs among the diploid spore mother cells producing haploid spores.

4.   The purpose of the cuticle is to prevent the evaporation of water from the internal tissues of the plant. The thin cuticle of bryophytes allows water to easily evaporate from many bryophytes, thus most bryophytes are limited to moist shaded areas.

5.   Hydroids are for the transport of water and leptoids for the transport of foods. These tissues are not as advanced in structure and are not as efficient in the transport of water and food as or xylem and phloem tissues.

6.   Bryophytes have a flagellated sperm, thus they are dependent upon water on the surface of the plant to swim from the antheridium to the archegonium for fertilization.  This limits most bryophytes to moist areas where water is common on the surface of the plant.

7    Even though some bryophytes appear to have roots, leaves and stems they do not since by definition true roots, leaves and stems contain xylem and phloem tissues.

8.   The Division Musci contains the mosses. Mosses differ in structure and appearance from liverworts and hornworts in that mosses usually grow upright and have leaf-like structures spirally arranged around the upright stalk. Liverworts and hornworts grow prostrate on the substrate and often form a flat leaf-like thallus. Leafy liverworts grow prostrate to the substrate and produce their leaf-like structures in a two dimensional arrangement rather than three dimensionally as in moss.

9.   Refer to number 3 for the generalized life cycle of the moss.  The moss sporophyte grows as an upright stalk from the archegonium of the female gametophyte.  As it matures it produces a capsule at its apex where spores are produced.

10. Mosses grow mostly in moist habitats. They are important in providing habitat in the areas they grow.  They help to stabilize the soil, retain moisture and some act as pioneer plants in biological succession in some locations. Mosses such as Sphagnum create the conditions required for acid bog communities in many locations in the world.

11. Sphagnum moss produce peat bogs in many areas of the world.  Sphagnum forms peat which has been used for centuries for fuel and building material. Today peat used as fuel electric power plants in some areas of the world. Peat is also harvested and used as a soil conditioner.

12. The division Hepatophyta contains the liverworts. Liverworts grow prostrate on the substrate and often form a flat leaf-like thallus. Leafy liverworts grow prostrate to the substrate and produce their leaf-like structures in a two dimensional arrangement rather than three dimensionally as in moss.

13. The archegonia of the liverwort are located on the underside of lobes of the upright archegoniophore.  The antheridia are sac-like structures located in the upper surface of the cap located at the apex of the antheridiophore. Refer to your text and lab materials for photos or drawings.

14. The liverwort sporophyte is a sac-like structure that develops from the fertilized egg within the archegonium. The sporophyte develops on the underside of the archegoniophore and receives all its nourishment from the gametophyte.

15. Gemmae cups are asexual reproductive structures located on the upper surface of the liverwort thallus. They contain groups of cells that can splash out with raindrops.  These groups of cells can develop into mature gametophytes.

16. The Division Anthocerophyta contains the hornworts.

17. Describe the appearance of hornworts.Hornworts grow prostrate on the substrate and often form a flat leaf-like thallus similar to liverworts. The sporophyte grows upward from the gametophyte as a horn-like structure. Unlike other bryophytes the hornwort sporophyte is green and photosynthetic, has stoma on its surface and is rather long lived.

18. Hornworts contain nitrogen fixing Nostoc within cavities in the thallus.

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CHAPTER 21: INTRODUCTION TO VASCULAR PLANTS: FERNS AND THEIR RELATIVES NOTES

1.   Non-seed producing vascular plants are the ferns and fern allies. The sporophyte is the dominant generation in the lifecycle and the gametophyte is reduced to a small heart shaped structure. Sporophyte and gametophyte plants are separate bodies. Ferns and fern allies are vascular plants meaning that they have xylem and phloem tissue. Even though ferns produce swimming sperm ferns and fern allies are more diverse and successful that the bryophytes.  Ferns are more resistant to desiccation than bryophytes.

2.   Sporophytes produce spores in sporangia located in either cone-like strobili or on the surface of  vegetative leaves in clusters called sori. Gametophytes are free living and may be photosynthetic as in ferns or form symbiotic relations with soil fungi as in most other fern allies. Antheridia and archegonia are produced on the gametophyte.

3.   Microphylls are often small leaves with only one vascular bundle entering the blade from the stem while megaphylls are often larger and have multiple vascular bundles entering the blade from the stem.

4.   DIVISION PSILOPHYTA - WISK FERNS

• Two Genera And 10 Species.
• Most Primitive Vascular Plants
• Generally Consist Of A Forked Stem Up To 30 Cm
• Show Dichotomous Branching.
• Branches And Rhizoids Develop From An Underground Rhizome.
• No Leaves Or Roots, Have Rhizoids And Scales
• Non Photosynthetic Underground Gametophyte
• Over 400 Million Years

5.   DIVISION LYCOPHYTA - GROUND PINES, CLUB MOSSES, SPIKE MOSSES

• Lycopodium - 200 Species
• Selaginella - 700 Species
• Produce Spores in Terminal Cone-Like Strobili.  A Strobilus Is Composed of Clusters of Modified Leaves that Function as Sporangia.
• Small Leaf-Like Structures Microphylls
• Selaginella Is Heterosporous - Produce Both Microspores And Megaspores. This Is An Important Step Toward The Production Of Seed.
• Lycopodium Is Homosporous.
• Common Over Much Of The World
• Refer to the lecture slides for more information.

6.   DIVISION SPHENOPHYTA - HORSETAILS

7.   DIVISION PTEROPHYTA - FERNS

• 9,700 Species
• Most Are Terrestrial But Some Have Evolved An Aquatic Floating Life Style.
• Azolla, A Floating Fern Houses Nitrogen Fixing Bluegreen Algae. In Asia It Is Grown In Rice Fields To Fertilize The Fields.
• Some Tree Ferns Grow As High As 30 Meters.
• Gametophyte - Heart Shaped Prothallus, Antheridia And Archegonia Are Produced On The Lower Surface.
• Sporophyte - Dominate Green Plant
• Spores Produced On The Surface Of Specialized Leaves (Fronds) Called Sporophylls
• Vegetative Leaves Are Called Fronds.
• Spores Produced In Sporangia
• Sporangia Or Clustered Into Groups Forming Sori
• Non Seed Producing
• Review The Life Cycle Of The Fern In Your Text.

8.   The prothallus is the gametophyte and grows as a prostrate heart shaped thallus.  It produces antheridia and archegonia for sexual reproduction. The sorus is made of a cluster of sporangia located on the lower surface of the frond. The fern frond extends as it grows and elongates from its coiled tip.  The coiled tip is the fiddlehead.

9.  Ferns and fern allies are most common in the moist tropics.  Ferns are by far the most common and successful in today's world. Ferns range in size from a few millimeters to tree ferns that grow 50 to 70 feet in height.

CHAPTER 22: INTRODUCTION TO SEED PLANTS: GYMNOSPERMS NOTES

1.  General characteristics for the gymnosperms.

• Gymnosperms produce naked seed often on the surface of woody scales
• Spore producing structures are strobili, cones, and are composed of modified leaves.
• Tracheids are the most conducting elements in the xylem
• Many are drought tolerant
• Many form vast forest, especially in the northern hemisphere.
• Refer to the lecture slides for more information.

2.   DIVISION CYCADOPHYTA - CYCADS

• Flourished In The Jurassic, Now 10 Genera And 160 Species
• All Tropical Or Subtropical.
• Most Are Tree Like And Palm Like In Appearance.
• Produce Very Large Male And Female Cones On Separate Plants, Dioecious.
• May Live Over A Thousand Years.
• Produce Flagellated Sperm
• Refer to the lecture slides for more information.

3.   DIVISION GINKGOPHYTA - GINKGO TREES

• Only One Living Species, Ginkgo biloba.
• Common During The Jurassic.
• Commonly Planted In Cities Because Of Resistance To Atmospheric Pollution.
• Dioecious
• Refer to the lecture slides and text for more information.

4.  DIVISION GNETOPHYTA - GENTUM, EPHEDRA, WELWITCHIA

5.   Division Coniferophyta

6.   Refer to the lecture slides and text for a review of the lifecycle of the pine.

7.   Gymnosperms form vast forest in much of   the world, particularly in the northern hemisphere.  As such they provide considerable natural habitat.  Economically they are the most important lumber and paper pulp plants in the northern hemisphere.

CHAPTER 23: FLOWERING PLANTS NOTES

1.   The Division Anthophyta

• 250,000 Species
• By far the most diverse and successful plants on earth today.
• Most Possess Xylem Vessels
• The Flower if the Sexual Reproductive Organ of the Plant.
• Dominant Sporophyte With A Much Reduced Gametophyte.
• The Gametophyte Is Much Reduced, The Male Gametophyte Is The Pollen Grain. It Develops Within The Anther And Is Released Upon Maturity. The Female Gametophyte Is The Ovule Sac. It Develops Within The Ovary And Remains There Upon Maturity.

2. Initially the anther is the microsporangia and is the site of Microspores production; later the microspores mature into pollen grains within the anther.  Pollen grains are the male gametophytes. Diploid microspore mother cells undergo meiosis to produce haploid microspores.  In many flowering plants the microspore undergoes one mitotic division producing a two nucleated pollen grain.   One nucleus the tube nucleus will control the growth of the pollen tube as it germinates prior to fertilization.  The other nucleus, the generative nucleus, divides again by mitosis producing two sperm nuclei.  One sperm nucleus will fertilize the zygote to produce the embryo and the other will fuse with the polar nuclei of the female gametophyte to produce a food storage tissue, the endosperm.

3.   Megaspores are produced in the ovary.   each ovary contains one or more ovules.  Each ovule contains a diploid megaspore mother cell which will undergo meiosis to produce a single functional haploid megaspore.  In many flowering plants the megaspore then undergoes a series of three mitotic divisions producing a seven celled, eight nucleated female gametophyte, the ovule sac.  The egg nucleus is fertilized by one sperm producing the embryo and the two polar nuclei fuse with the second sperm nucleus from the pollen tube to produce the endosperm.  The other nuclei usually degenerate as the ovule develops into the seed. Refer to your lecture slides for the location and identity of the nuclei of the ovule sac.

4.   Pollination is the transfer of pollen from the anther to the stigma of the same flower or to another flower.  After pollination the pollen grain germinates producing the pollen tube that grows through the carpel to the ovule where the sperm are released for fertilization which is the fusion of the sperm and egg nucleus.  In flowering plants this is called double fertilization because the second sperm then fuses with the polar nuclei to form the endosperm. Pollination can be facilitated by the wind or by animal pollinators such as insects, birds and bats. Through coevolution many pollinators have evolved interdependencies in which both the plant and pollinator become dependent upon each other for survival.

5.   Apomixis is reproduction with out meiosis or the fusion of gametes in otherwise normal sexual structures. Parthenocarpy is the development of a fruit from an unfertilized ovary, thus normally no seed are produced.

6.   Flower structure:

• Flowers Evolved From Shoot Systems, Stems And Leaves. A Flower Is A Much Shortened Stem Tip With Highly Modified Whorls Of Leaves That Function As Floral Parts.
• Flower Structure And Function.
• Sepals - First Whorl Of Floral Parts, Leaf Like, Cover The Bud Prior To Opening.
• Calyx - All Sepals Collectively.
• Petals - Second Whorl Of Floral Parts Usually Colorful, Common On Flowers Pollinated By Animals, Attract Pollinators.
• Corolla - All Petals Collectively.
• Stamens - Male Reproductive Portion Of The Flower. Composed Of A Supporting Filament And A Pollen Producing Capsule The Anther At The Apex.
• Pistil Or Carpel - Female Portion Of The Flower. Composed Of The Stigma, Style And Ovary.Stigma - Apical Portion, Produces A Sweet Sticky Fluid For Germination Of The Pollen Grain.
• Style - Stalk Connecting The Stigma To The Ovary.
• Ovary - The Expanded Base Of The Flower That Produces The Ovules, The Female Gametophytes. Upon Fertilization The Ovule Becomes The Seed And The Ovary The Fruit.
• Perianth - A Collective Term For The Calyx And The Corolla.
• Inferior Ovary - Floral Parts Are Fused To The Outer Ovary Wall And Emerge As Free Appendages Above The Ovary. Same As An Epigynous Ovary
• Superior Ovary - Floral Parts Are Free From The Ovary And Are Attached At Its Base. Same As A Hypogynous Ovary
• Complete Flower - A Flower With All Four Whorls Of Floral Parts.
• Incomplete Flower - A Flower That Is Lacking One Or More Of The Floral Parts
• Perfect Flower - A Flower With Both Stamens And Pistil.
• Imperfect Flower - A Flower That Is Lacking Either The Pistil Or The Stamens.
• Inflorescence - The Assemblage Of Flowers At An Apex Or The Flower Cluster.
• Zygomorphic Flower - A Flower That Is Bilaterally Symmetrical.
• Actinomorphic Flower - A Regular Flower, A Flower That Has Radial Symmetry.