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