Chapter 32: Evolution and Diversity of Modern Gymnosperms and Angiosperms (Part 1, Week 6) Flashcards
What are particularily important in our everyday lives because they are the sources of many products, including wood, paper, beverages, food, cosmetics, and medicine?
The seed plants–Gymnosperms and Angiosperms
What are some examples of seed plants helping in medicine?
All of these are secondary metabolites which are distinct from the products of primary metabolism (carbs, lipids, proteins, and nucleic acids).
Madagascar periwinkles provide extracts for leukemia and lymphatic cancers.
Taxol, found in the bark of Pacific yew tress, is used to treat breast and ovarian cancers.
T/F Secondary metabolites are particularily diverse in gymnosperms and angiosperms.
True. Their roles help in protecting plants from disease-causing organisms and plant-eating animals, and also aid plant growth and reproduction.
[Start 32.1 Overview of Seed Plant Diversity]
What did gymnosperms originate from?
Now extinct seedless plants known as progymnosperms.
These were woody, representing the first trees.
Few gymnosperm, especially conifers, exist today.
T/F Angiosperms arose from an unknown gymnosperm lineage, thereby inheriting the capacity to produce wood and other seed plant features.
True
[Start 32.2 The Evolution and Diversity of Modern Gymnosperms]
What is a plant that produces seeds that are exposed rather than seeds enclosed in fruits?
Gymnosperms Greek gymnos, meaning naked (referring to the unclothed state of ancient athletes), and sperma, meaning seed.
What do most modern gymnosperms occur as?
Woody plants such as shrubs or trees.
What modern gymnosperms include that are native to the Sierra Nevada mountains of the western U.S. and are among Earth’s largest organisms weighing as much as 6,000 tons and reaching an amazing 100 m in height?
Famous giant sequoias (Sequoiadendron giganteum)
What is a secondary plant tissue composed of numerous pipelike arrays of empty, water-conducting cells whose walls are strengthened by an exceptionally tough polymer known as lignin?
The large size of the sequoias and other trees is based on the prescence of this!
Wood
These properties enable woody tissues to transport water upward for great distances and also to provide the structural support needed for trees to grow tall and produce many branches and leaves.
In modern seed plants, what is a special tissue that produces both thick layers of wood and thinner layers of inner bark?
Vascular cambium
A secondary meristematic tissue of seed plants.
What is a thin layer of secondary phloem that transports watery solutions of organic compounds in a woody stem?
Inner bark
What helps gymnosperms and woody angiosperms to compete effectively for light and other resources needed for photosynthesis? (3)
Vascular cambium, wood, and inner bark.
How did the vascular tissue of progymnosperms (first trees with leafy tiwgs; from Greek meaning before gymnosperms) differ from earlier vascular plants?
The vascular tissue of progymnosperms differed from that of earlier vascular plants in being arranged in a ring around a central pith of nonvascular tissue.
This is called an eustele.
What are regarded as the earliest diverging modern gymnosperm phylum, originating more than 300 mya?
Cycads (cycad comes from a Greek word meaning palm)
Nearly 300 cycad species occur today, primarily in tropical and subtropical regions.
Many cycads are listed as endangered, and commercial trade in cycads is regulated by CITES (Convention on International Trade in Endangered Species of WildFauna and Flora), a voluntary international agreement between governments to protect such species.
Bonus Question! Are palm trees and cycads the same thing?
No, because cycads (which are gymnosperms) do not produce flowers while palm trees do.
What do cycads produce that are extended above ground and have branching shapes resembling corals?
What do they harbor within themselves?
Coralloid roots
Coralloid roots harbor light-dependent, photosynthetic cyanobacteria within their tissues. The cyanobacteria, which form a bright blue-green ring beneath the root surfaces, convert atmospheric nitrogen (N2) into ammmonia (NH3), providing their plant hosts with the nitrogen that is crucial to growth.
How is cycad reproduction unique?
They produce conspicuous conelike structures that bear either ovules and seeds or pollen.
When matured, they emit odors to attract beetles that carry pollen to the ovules where the pollen produces tubes that deliver sperm to eggs.
What is the single remaining species of a phylum that was much more diverse during the Age of Dinosaurs?
Its species name from the two-lobedshape of its leaves, which have unusual forked veins
Ginkgo bilboa trees
What is an interesting fact about G. bilboa trees and how they came to be widely cultivated today?
They descended from seeds produced by a tree found in a remote Japanese temple garden and brought to Europe by 17th-century explorers.
Why are Gingko seeds often mistaken as fruits?
Because of their colorful appearance. They have fleshy, foul-smelling seed coats.
What are G. biloba trees widely planted along city streets? (2)
- Because they areornamental and also tolerate cold, heat, and pollution better than manyother trees.
- In addition, these trees are long-lived—individuals can live for more than a thousand years and grow to 30 m in height.
T/F G. biloba trees can have a specific sex.
True.
Individual trees produce either ovules and seeds or pollen, based on a sex chromosome system much like that of humans.
Ovule-producing trees have two X chromosomes; pollen-producing trees have one X and one Y chromosome.
How does a G. biloba tree reproduce?
- Wind disperse pollen to ovules which then germinate and grow through ovule tissues for several months.
- The tubes burst, delivering flagellate sperm to egg cells.
- After fertilization, zygotes develop into embryos, and the ovule integument develops into a fleshy, foul-smelling outer seed coat and a hard inner seed coat.
What is the lineage of trees named for their seed cones, of which pinecones are familiar examples?
Conifers! More than 50 genera.
T/F All conifers are deciduous.
False. Some are and some are not. Deciduous means that they drop all of their leaves in the fall.
Since confiers develop simple pollen cones and more complex ovule-bearing cones, how do you distinguish between the two?
- For simple pollen cones, have many leaflike structures, each bearing a microsporangium in which meiosis occurs and pollen grains develop.
- For the more complex ovule-bearing cones, also called seed cones, are composed of many short branch systems that bear ovules. These ovules contain female gametophytes, within which eggs develop.
Information to better understand conifer reproduction terms!
- Mature sporophyte produces 2 types of cones: Ovule cones (2n) and Pollen cones (2n).
2a. For ovule cones, megaspores (n) are produced by meiosis within megasporangia.
- Within the scales of the cone, the megasporangium is the structure of the plant body that contains the female reproductive organ, which is the megaspore itself!
- This whole structure to include the scale can be called the ovule.
2b. For pollen cones, microspores (n) are produced by meiosis within microsporangia.
- Within the scales of the cone, like you might think, the microsporangia is the structure of the plant body that contains the male reproductive organ, which is the micropores themselves!
3a. The megaspores then undergo mitosis and produce female gametophytes that containing eggs within archegonia.
- Again, this whole structure is considered as the ovule.
- To image this, think of the russian nesting doll. The integument (which comes from the scale) covers the entire ovule except for the small opening for fertilization. Just inside the integument, lies the megasporangium (2n). Then the female gametophyte (n) and the two archegoniums (n) containing 1 egg (n) a piece.
3b. The microspores undergo mitosis as well, and develop into pollen grains, which are are young male gametophytes (not yet mature!)
- The microsporangium is lost, and the pollen grains are dispersed into the wind and encounter ovules. - The pollen grain’s male gametophyte (with its antheridium which is the equivalent to the female archegonium that houses the egg cells) matures, producing sperm cells in a pollen tube.
- The pollen tube delivers sperm to eggs, where fertilization occurs. Only 1 egg per ovule is fertilized and develops!
- After fertilization, the zygote (diploid cell resulting from the fusion of two haploid gametes (sperm and egg)), produces an embryo within a seed. Mature seeds are then dispersed.
- Seeds germinate, and embryo sporophytes grow into seedlings!
THIS process takes 2 years! From gamete development to seed development!
N/A
What are the specialized vascular cells within the wood of conifers that are efficient water and mineral conduction even in dry conditions?
Tracheids
Like the tracheids of other vascular plants, those of conifers are devoid of cytoplasm and occur in long columns that function like plumbing pipelines
What do tracheids possess in their side and end walls that are circular which allow water to move both vertically and laterally from one tracheid to another?
Pits
Definition - A thin-walled circular area in a plant cell wall where secondary wall materials such as lignin are absent and through which water moves.
What is the nonporous, flexible central region of a conifer pit that functions like a valve?
The torus (plural, tori)
Why does the presence of tori within the tracheids of conifers help explain why they have been successful for hundereds of millions of years?
When tracheids are dry in arid or cold habitats, they fill with air and cannot conduct water. For this, the torus presses against the pit opening, sealing it.
This conifer adaptation localizes air bubbles, preventing them from stopping water conduction in other tracheids.
What do the conspicuous resin ducts that be display on conifer woods and leaves accomplish?
Flow of syrup-like resin that helps prevent attack by pathogens and herbivores.
Resin that exudes from tree surfaces may trap insects and other organisms, then harden in the air and fossilize, preserving the inclusions in amber.
