29 Plant Diversity: How Plants Colonised Land Flashcards
What organism have cell walls made of cellulose?
Green algae, dinoflagellates, brown algae and plants
Do algae have cell walls made of cellulose?
Yep
In what organisms are chloroplasts with chlorophyll a and b seems?
Green algae, euglenids, plants and a few dinoflagellates
What did land plants evolve from?
Charophyte algae.
What suggests that land plants evolved form charophyte algae?
They share 4 basic characteristics: rings of cellulose-synthesising proteins, peroxisome enzymes, similarly structured flagellated sperm and the formation of a phragmoplast.
How are charophyte algae similar to land plants in terms of rings of cellulose-synthesising proteins?
The cells of both land plants and charophytes have distinctive circular rings of proteins in the plasma membrane. These protein rings synthesize the cellulose microfibrils of the cell wall.
Noncharophyte algae have linear sets of proteins that synthesize cellulose.
How are charophyte algae similar to land plants in terms of peroxisome enzymes?
The peroxisomes of both land plants and charophytes contain enzymes that help minimize the loss of organic products resulting from photorespiration.
How are charophyte algae similar to land plants in terms of the formation of a phragmoplast?
In land plants and certain charophytes, a group of microtubules called the phragmoplast forms between the daughter nuclei of a dividing cell.
A cell plate then develops in the middle of the phragmoplast, across the midline of the dividing cell. The cell plate, in turn, gives rise to a new cross wall that separates the daughter cells.
What is a phragmoplast?
A group of microtubules that forms between the daughter nuclei of a dividing cell in plants and charophyte algae.
A cell plate develops in the middle of the phragmoplast and eventually becomes a cell wall.
How are the zygotes of charophytes protected form desiccation?
They are surrounded by a layer of a durable polymer called sporopollenin that prevents the exposed zygotes from drying out.
What is sporopllenin?
A durable polymer that surrounds the zygotes of charophytes to prevent them from desiccation.
What are the main challenges of life on earth?
- Need more structural support - note how jellyfish flops when out of water
- Desiccation
- Distribution of gametes.
What are land plants most closely related to?
Charophytes
What does ’viridiplantae’ refer to?
A proposed kingdom that would include chlorophytes, charophytes and embryophytes (land plants) but not red algae
What does ’streptophylta’ refer to?
A proposed kingdom that would include charophytes and embryophytes (land plants) but not red algae or chlorophytes
What are land plants also known as?
Embryophytes
What are embryophytes?
Land plants
What are the derived characteristics of land plants?
Alternation of generations & Multicellular, dependant embryos,
Walled spores produced by Sporangia
Multicellular gametangia
Apical meristems
Do algae have apical meristems?
No, this is a derived trait of land plants
In what organisms does alternation of generations occur?
In some algae but not charophytes (analogy)
Obviously in land plants etc.
What is the basic idea of alternation of generations in plants?
The multicellular haploid gametophyte produce haploid gametes (eggs and sperm) by MITOSIS that fuse during fertilisation, forming diploid zygotes.
To zygote undergoes mitosis to multicellular diploid sporophyte. Meiosis in a mature sporophyte produces haploid spores, eproductive cells that can develop into a new haploid organism without fusing with another cell.
Mitotic division of the spore cell produces a new multicellular gametophyte, and the cycle repeats
How do plant embryos differ from algae?
Multicellular plant embryos develop from zygotes that are retained within the tissues of the female parent (a gametophyte).
The parental tissues provide the developing embryo with nutrients, such as sugars and amino acids.
How does the plant embryo receive nutrients from the parent?
It has specialised ‘placental transfer cells’ to transfer sugars etc.
What are placental transfer cells?
Specialised cells found in the plant embryo to help it acquire nutrients from the parent
Why are plants called embryophytes?
They have multicellular embryos that are dependant on the parent.
What is unique about land plant spores?
They are walled and produced by sporangia
Where are land plant spores produced?
In multicellular organs called sporangia
What do sporangia produce?
Land plant spores
How are land plant spores produced?
Within a sporangium, diploid cells called sporocytes (‘spore mother cells’), undergo meiosis and generate the haploid spores.
The outer tissues of the sporangium protect the developing spores until they are released
What structure within the sporangia forms the spores?
Sporocytes
What are sporocytes also know as?
‘Spore mother cells’
What are spore mother cells?
Sporocytes
Where are gametes produced in land plants?
Gametangia
What are gametangia?
The multicellular organs in land plants that form gametes
What are the types of gametangia?
Archegonia and antheridia
What is archegonia?
The type of gametangia that produces female gametes (eggs)
What is antheridia?
The type of gametangia that produces male gametes (sperm)
What is the form of gametangia that produces male gametes?
Antheridia produces sperm
What is the form of gametangia that produces female gametes?
Archegonia produces eggs
What is a key adaptation of land plants to prevent desiccation?
A waxy cuticle
What were the roots of early land plants like?
Short and not well developed
How did early land plants survive with primitive roots?
They formed symbiotic relationships with mycorrhizae
What are ’secondary compounds’?
Products that are produced by plants from secondary metabolic pathways. These include alkaloids, terpenes, tannins and flavonoids which serve many purposes such as discouraging herbivores.
Note that secondary metabolic pathways are side branches of the primary metabolic pathways that produce lipids, carbohydrates and amino acids etc.
What are the products of ancillary metabolic pathways in plants called?
‘Secondary compounds’
note that ancillary metabolic pathways is not a technical term
What are ’secondary metabolic pathways’?
Those that branch off from the primary metabolic pathways such as those that produce carbohydrates and amino acids.
What are ‘primary metabolic pathways’?
The basic ones that are fundamentally important for plant life. They include the synthesis of lipids, amino acids and carbohydrates.
Why are secondary compounds important to the plant?
Various alkaloids, terpenes, and tannins have a bitter taste, strong odor, or toxic effect that helps defend a plant against herbivores and parasites.
Flavonoids absorb harmful UV radiation, and some related compounds deter attack by pathogens.
What is is the most basal group of land plants?
Bryophytes
What are bryophytes?
Non-vascular plants
What are nonvascular plants called?
Bryophytes
What groups of organisms does bryophyte include?
Moss, liverworts and hornworts
What is a ‘grade’?
A group of biological organisms that share a key trait
What is a group of biological organisms that share a key trait called?
A ‘grade’
What are vascular plants divided into?
‘Seedless vascular plants’ and ‘seed plants’
What groups of plants are seedless vascular plants?
Lycophytes and Pterophytes
What group are lycophytes in?
Seedless vascular plants.
What organisms are lycophytes?
Club mosses, spike mosses and quilworts (not normal mosses)
What group are club mosses in?
Lycophytes and thus seedless vascular plants (not bryophytes)
What group are spike mosses in?
Lycophytes and thus seedless vascular plants (not bryophytes)
What groups of organisms are pterophytes?
Ferns, horsetails and whisk ferns
What groups of organisms are ferns?
Pterophytes and thus seedless vascular plants.
What groups of organism are seed plants?
Gymnosperms and angiosperms
What type of organism are gymnosperms?
Seed plants
What is the fundamental trait of gymnosperms?
They do not have enclosed chambers in which seeds mature
What is the fundamental difference between angiosperms and gymnosperms?
Angiosperms have enclosed chambers in which seeds mature, gymnosperms do not.
What are the steps in the reproductive lifecycle of a moss?
Spores develop into small threadlike haploid ‘protonemata’
The protonemata produce ”buds” that divide by mitosis and grow into gametophores.
The gametaphores of males produce sperm that travel in a film of moisture to reach the female egg, which remains in the archegonia of the female gametophore.
Fertilisation takes place in the archegonium of the female to produce a diploid zygote.
The zygote develops into the sporophyte embryo.
The sporophyte grows a long stalk (seta) that emerges from the archegonium.
Attached by its foot, the sporophyte remains nutritionally dependant on the gametophyte.
Meiosis occurs and haploid spores develop in the capsule. When the capsule is mature, its lid pops off, and the spores are released.
What is the capsule?
The organ at the end of the seta which consists of sporangium that produces spores.
What is the structure of a moss?
It has a root called a rhizoid, a “stalk” called the ’seta’ which terminates in the capsule
What is the seta of a moss?
Its “stalk”
What is at the end of a moss’s seta?
Its capsule
What is the “stalk” of a moss called?
Its seta
What are the “roots” of mosses called?
Rhizoids
How do mosses gain the water needed for life processes?
Not through their rhizoids
What is the role of rhizoids?
Anchoring
They lack specialised water conducting cells and thus do no play a primary role in water and mineral absorption
Why are rhizoids not heavily involved in mineral and water absorption?
They lack specialised water conducting cells
What is the structure of rhizoids?
Long, tubular single cells (in liverworts and hornworts) or filaments of cells (in mosses).
Unlike roots, which are found in vascular plant sporophytes, rhizoids are not composed of tissues.
What are the groups of bryophytes (common names)?
Liverworts, hornworts and mosses
Technical name:
What are the groups of bryophytes (scientific names)?
Hepatophyta, anthocerophyta and bryophyta
What are liverworts technically called?
Hepatophyta
What are hornworts technically called?
Anthocerophyta
What are mosses technically called?
Bryophyta
What does ’hepatophyta’ refer to?
The bryophyte phylum that consists of liverworts.
What does ’anthocerophyta’ refer to?
The bryophyte phylum that consists of hornworts.
What does ’bryophyta’ refer to?
The bryophyte phylum that consists of mosses.
What does ’thalloid’ refer to?
When describing plants it means that they do not have a distinct stem and leaves.
What is the structure of liverworts?
Many have liver shaped leaves (technically thalluses) that are the gametophytes.
In some the gametophore emerges and branches out like a little plan tree. Sporophytes dangle form this structure.
What is the structure of hornworts?
They are basically just tall tubes.
This sporophyte can grow up to 5 cm tall and consists entirely are sporangium, with no seta produced.
What structures make up the sporophyte of a moss?
The capsule and seta.
What does ’brood bodies’ refer to?
Some mosses reproduce asexually by forming brood bodies, small plantlets that detach from the parent plant and grow into new, genetically identical copies of their parent.
How are spores released from the capsule?
In most mosses, the seta becomes elongates to elevate the capsule. Typically, the upper part of the capsule features a ring of interlocking, tooth-like structures known as the peristome.
These “teeth” open under dry conditions and close again when it is moist. This allows spores to be discharged gradually, via periodic gusts of wind that can carry them long distances.
What are ‘peristomes’?
Teeth-like structures around the capsule that can be opened and closed to allow the controlled release of spores
What structure in the capsule allows spore release to be regulates?
The ‘periostomes’
Why are peristomes important?
They allow the spores to be slowly released.
They also allow the plant to control when they are released such. For example it is advantageous to release them during dry days with high winds.
In what organisms are stomata found?
Plants but also mosses and hornworts
Do mosses have stomata?
Yes
Do liverworts have stomata?
No
Do hornworts have stomata?
Yes
Why are stomata important for mosses and hornworts?
They support photosynthesis by allowing the exchange of CO2 and O2 between the outside air and the sporophyte interior
They also provide evaporative cooling
What is peat?
A large deposit of partially decayed organic material such as dead moss
What were the first tall plants?
Ferns and other seedless vascular plants.
What are the stages in the reproductive cycle of ferns?
Sporangia release spores. Most fern species produce a single type of spore that develops into a bisexual photosynthetic gametophyte.
Each gametophyte develops spermproducing organs called antheridia and egg-producing organs called archegonia.
Sperm use flagella to swim to eggs in the archegonia of a different gametophyte. An attractant secreted by archegonia helps direct the sperm.
Fertilisation occurs to produce a zygote that develops into a new sporophyte. The young plant grows out from an archegonium of its parent, the gametophyte.
On the underside of the sporophyte‘s reproductive leaves are spots called sori. Each sorus is a cluster of sporangia that produces spores through meiosis
What is the sporangium of ferns found?
In dots on the underside of the leaves called ’sori’ (singular: sorus)
What does ’sorus’ refer to?
The dots on the underside of a fern leaf that contain the sporangium (plural: sori)
What does ’sori’ refer to?
The dots on the underside of a fern leaf that contain the sporangium (singular: sorus)
What are the structures that produce spores in ferns called?
Sori (sing.: sorus)
What are the dots on the underside of ferns?
Sori (produce spores)
In ferns is the sporophyte or gametophyte dominant
Sporophyte
Are the large fern leaves sporophytes or gametophytes?
Sporophytes
What are the leaves of lycophytes called?
Microphylls
What are microphylls?
The small, usually spine-shaped leaves supported by a single strand of vascular tissue that are found only in lycophytes
What are most plant leaves?
Megaphylls (not microphyls)
What plants have megaphylls?
All plants except bryophytes
What are megaphylls?
Leaves with highly branched vascular systems.
What are leaves with highly branched vascular systems called?
Megaphylls
What are sporophylls?
Modified leaves that have sporangia
What are modified leaves with sporangia called?
Sporophylls
What are cones technically called?
Strobili
What are strobili?
Groups of sporophylls (leaves with sporangia) formed into cone-like structures.
What are sporophylls arranged into cone-like structures called?
Stroboli
How can seedless vascular plants be divided into based on the spores they produce?
Heterosporous or homosporuos.
What are homosporus plants?
Those that have one type of sporangium that produces one type of spore, which typically develops into a bisexual gametophyte,
What are heterosporous plants?
Those that have two types of sporangia and produces two kinds of spores.
Megasporangia on megasporophylls produce megaspores, which develop into female gametophytes
Microsporangia on microsporophylls produce the smaller microspores, which develop into male gametophytes.
What are the basic stages of homosporous spore production?
Sporangium on the sporophyll produces a single type of spore.
This spore develops into a bisexual gametophyte that produces eggs and sperm
What are the basic stages of heterosporous spore production?
Megasporangium on the megasporophyll produces megaspores that develop into female gametophytes that produce eggs.
Microsporangium on the microsporophyll produces microspores that develop into male gametophytes that produce sperm
What is megasporangium?
The tissue in heterosporous plants which produces megaspores
What is microsporangium
The tissue in heterosporous plants which produces microspores
What are microspores?
The spores produced by the microsporangium that develop into sperm-producing male gametophytes
What are sporophyls?
Leaves which contain spore-producing sporangium
What is a megasporophyll?
A leaf that contains megasporangium which produces megaspores
What is a microsporophyll?
A leaf that contains microsporangium which produces microspores
What are megaspores?
The spores produced by the megasporangium that develop into egg-producing female gametophytes.
What nutritional role do many lycophytes play?
Many are epiphytes
What do the lycophytes include?
Club mosses, spike mosses and quilworts
In what phylum are ferns?
Pterophyta
In what phylum are horsetails?
Pterophyta
In what phylum are whisk ferns?
Pterophyta
In what phylum are club mosses?
Lycophyta
In what phylum are spike mosses?
Lycophyta
In what phylum are quillworts?
Lycophyta
What is a protonema?
The thin filaments formed as mosses first emerge from spores.
What is the foot of a moss?
The part that connects it to the gametophyte (not to be confused with the rhizoid roots)
What is the part that joins the moss gametophyte and sporophyte?
The foot
What is the gametophyte form of a moss?
The tall green bits at the bottom
What is the sporophyte form of a moss?
The brown bits at the top that terminate in the capsule
Is the green bit of a moss the gametophyte or sporophyte?
Gametophyte
What is the ploidy of moss gametophytes?
Haploid
Are the brown bits at the top of the mosses gametophytes or sporophytes?
Sporophytes
What is the gametophyte form of a fern?
The small little disks that have rhizoids
Are the small disks the gametophyte or sporophyte form of ferns?
Gametophyte
What is the sporophyte form of ferns?
The large green leaves we are familiar with
Are the large green leaves of a fern the gametophyte or the sporophyte?
Sporophyte
