Homework SoursePlant Diversity II Seed Plants 1 Explain how the rise in pr
Plant Diversity II – Seed Plants
1. Explain how the rise in prominence of one major group (angiosperms, for example) does not necessarily result in the total replacement of a previously dominant group (gymnosperms, for example)?
2. How have gymnosperm ovules evolved to withstand desiccation and herbivorous animals?
3. Your neighbor’s vegetable garden is being attacked by Japanese beetles, so she dusts her garden with an insecticide. Now, to her dismay, she realizes that the beans and squash are no longer producing. Explain to your neighbor the relationship among flowers, fruits (vegetables, in the gardening language), and insects
4. Seed plants provide food, medicines, fibers, beverages, building materials, dyes, and psychoactive drugs. Using web resources, your textbook, and library references, describe examples of human uses of plants in Table 16.7. Indicate whether your example is a gymnosperm or angiosperm. Based on your research, what is the relative economic importance of gymnosperms and angiosperms.
| Plant Diversity II – Seed Plants |
Solution
Ans 1: Two selective pressures have been proposed.
Gymnosperm leaves take a few years to be replaced and decay very slowly once shed so do not build soil fertility. Angiosperm adapted not just to shed leaves annually but also for leaves to decay rapidly building soil organics and fertility.
Angiosperm adapted for greater rate of photosynthesis suitable to support episodic dormancy and compete canopy replacement. One key difference is that temperate deciduous trees dominate in warmer regions with less cloud cover. This provides the plants with a higher photosynthetic rate for the growing season when they must store up the food created from photosynthesis as quickly and as excessively as possible while they do have leaves. This is in order to create sufficient food reserve to survive the winter with a dormant metabolism then regrow the entire canopy. The trees have broad, thin leaves they can angle for maximal solar exposure.
Gymnosperm remain evergreen in the cooler circumpolar boreal forests. Summer days are long but lack intense sunlight due to frequent cloud cover and high latitudes where the moist temperate coniferous forests & the boreal forests of the Northwest are dominant. The photosynthetic season is short and not very productive so evergreens were selected to keep their needle-like, cold tolerant leaves in order to be photosynthetic whenever temperatures allow. They have a slower photosynthetic rate. However these trees do not need to store food in order to replace their canopy annually so the slow, steady photosynthetic activity is sufficient.
Broad leaved deciduous trees need a combination of summer warmth with sufficient sunlight intensity and duration to store enough food to both survive the winter dormancy and regrow an entire leaf canopy. Further dropping leaves is a way to shed waste materials the tree has accumulated and to shed insect eggs laid on the leaves.
Evergreens simply have been selected for traits to survive in locations that cannot support most deciduous trees. They have a distinct conical shape, with layers of branches, to allow the low angled sunlight to penetrate farther in towards the trunk than the lollipop shape of a broadleaf trees allows. This branch layering also helps snow to slip free. The needle shaped leaf with very thick waxy cuticle permits photosynthesis during warm weather while protecting against severe desiccation during the cold winter storms when water is frozen. The leaf remains photosynthetic for 3 -5 years as it builds up an ever thicker cuticle. Once the cuticle is too thick for photosynthetic efficiency the leaf is replaced to only slowly release its nutrients.
Angiosperms due to their higher growth rates profit more rapidly from increased nutrient supply of their rapid leaf decay and regular litter production than gymnosperms. They created better soil they could take advantage of to out compete the slower growth of gymnosperms.
Ans 2: Hard, waxy and chemically resistant seed coats.
Ans 3: In particular, flower shares nectar with bee, bee carries pollen from one flower to another flower and fertilizes. Both benefit from the relationship. The flower doesn\'t need the nectar, the only reason its there is to feed the bee (or other insect, sometimes a bird) so that it will come and fertilize. Even the color of the flower (in fact the flower itself) is only there to attract the insect.
Ans 4: Economic importance of angiosperms:
The flowering plants cover their seeds by including them in a true fruit. They bear the reproductive organs in a structure called a flower; the ovule is enclosed within a carpel (female reproductive organ of a flower), which will lead to a fruit. In gymnosperms, the ovule is not enclosed at pollination and the seeds are not in a true fruit, although occasionally fleshy structures may cover the seed.
The dominant vegetation on the surface of the earth, with representation in aquatic environments as well, angiosperms provide great benefit to humans. On the one hand, such plants as the grasses (rice, corn, wheat,oats, sugar cane, etc.), the rose family (apples, pears, cherries, etc.), potatoes, tomatoes, peppers, coconuts, and olives are a central component of human nutrition and the human economy. Angiosperms also are a source of wood for shelter, paper for writing, fiber for clothes, and a variety of medicines. On the other hand, angiosperms also provide internal benefit to people, such as the joy they provide through the tastes and textures of fruits and the sights and smells of flowers. They are used for landscaping and for decorating homes, as the subject matter of works of art.
Angiosperms are integral to the environment and biogeochemical cycles of the planet, provide food and a living place for countless species, and help to convert radiant energy to a form that other organisms can use.
The angiosperms dominate the Earth’s surface and vegetation in more environments, particularly terrestrial habitats, than any other group of plants. As a result, angiosperms are the most important ultimate source of food for birds and mammals, including humans. In addition, the flowering plants are the most economically important group of green plants, serving as a source of pharmaceuticals, fibre products, timber, ornamentals, and other commercial products.
The basic angiosperm form is woody or herbaceous. Woody forms (generally trees and shrubs) are rich in secondary tissues, while herbaceous forms (herbs) rarely have any.Annuals are herbs that complete their growing cycle (growth, flowering, and death) within the same season. Examples of annuals can be found among cultivated garden plants, such as beans (Phaseolus; Fabaceae), corn (maize; Zea mays; Poaceae), and squashes (Cucurbita; Cucurbitaceae), as well as among the wildflowers, such as some buttercups (Ranunculus) and larkspurs (Delphinium). Biennials are also herbs, but, unlike annuals, their growing cycle spans two years: the vegetative (nonreproductive) plant growth takes place from seed during the first year, and flowers and fruit develop during the second. The beet (Beta vulgaris; Amaranthaceae) and wild carrot (Daucus carota; Apiaceae) are well-known biennials.
A perennial grows for many years and often flowers annually. In temperate areas the aerial parts of a perennialdie back to the ground at the end of each growing seasonand new shoots are produced the following season from such subterranean parts as bulbs, rhizomes, corms, tubers, and stolons.
Economic importance of gymnosperms: Gymnosperms are widely used in construction, furniture-building, paper-making and urban planning, as well as providing important solvents for industrial and home use, cleaning agents, and food. Gymnosperms are plants that do not flower and instead produce bare seeds or cones, as with the familiar pine tree.
Pine trees, of course, are of enormous economic importance. They grow quickly, and their wood is used to manufacture cheap construction materials such as particle board and plywood. Whole pines were the traditional material for ship masts, and their soft unprocessed wood continues to be used in woodworking. It is also a common firewood due to the low cost. Pulped pines produce the majority of paper manufactured.
Crude pine resin is commercially important. Rosin and oil of turpentine derived from the crude resin are used for applications ranging from oiling violin strings to making glue and soap on an industrial scale. Turpentine also has medical applications as an antispasmodic, a diuretic, a stimulant and an antibacterial.
Finally, pine nuts are used as food, the most famous recipe including them being pesto sauce.
Aside from pines, a gymnosperm called ginkgo is planted throughout major American cities as a street tree because it is resistant to pollution. Products made from ginkgo seeds are promoted by beverage manufacturers for their supposed neurological properties, said to promote alertness and memory.
Firs are used for their strong and attractive wood, which is relatively cheap due to the trees\' rapid growth.
Spruce is important to the music industry as spruce wood is used to make high-quality soundboards for violins and guitars.
