Presentation of gymnosperms. Department of gymnosperms. I. Testing knowledge on the topics covered
- The purpose of the lesson: create conditions for understanding and comprehending new educational information, for applying knowledge and skills in new learning situations and check the level of assimilation of educational material different ways learning.
- Lesson objectives:
- Educational: organize the activities of students to study information about the diversity of gymnosperms; to promote the assimilation of knowledge about the features of the external structure and the significance of gymnosperms, their role in nature; to promote awareness of the value of the subject being studied.
- Educational: to develop active cognitive activity through work with a textbook and showing presentations; teach to recognize gymnosperms; to form intellectual abilities (the ability to analyze, generalize, compare, classify, draw conclusions, proof).
- Educational: to form the experience of equal cooperation between the teacher and students in the learning process; stimulate development cognitive interest; to instill communication skills in students, the ability to conduct assessment and self-assessment; continue to cultivate respect for green plants.
- Most evergreen, needle-shaped or scaly leaves. Microspores give rise to a male gametophyte, consisting of several cells, which, when transformed, produce pollen. Pollen is carried by the wind and fertilization does not depend on water, falling on the cover of the ovule. Life forms in the form of trees and shrubs.
- The Gymnosperms division includes six classes, two of which are completely extinct. Evergreen tree-like, evergreen leafless shrubs, deciduous and coniferous trees are possible. Gymnosperms can be dioecious and monoecious.
- Subclass Conifers forms forests in North America and Northern Eurasia. The largest number of species of pine, spruce, fir, larch are concentrated around Pacific Ocean especially in China. Represented mainly by trees, wood consists of tracheids, contains resin passages. The leaves of most conifers are hard, needle-like (needles) and do not fall off in an unfavorable season.
- The needles are covered with a thick layer of cuticle, the stomata are immersed in the leaf tissue. In conifers, the main tissue is completely absent or there is very little of it. In the leaves of coniferous trees, phytoncides are produced that have bactericidal properties.
- Coniferous stems have cones - female and male; consist of axes with attached scales. On seed scales under two ovules, a gametophyte with one egg is formed from each. Most pine pollen grains have two light air sacs.
- Wood is used as fuel; building material; in car building; shipbuilding; in aviation; for the manufacture of musical instruments, furniture. In medicine, pine buds, juniper cone-berries are used; fir oil, needles; as well as resins, essential oils. The seeds are used in human nutrition.
- Habitat in the tropics and subtropics. *Buildings Evergreen tree-like, rarely stunted plants, similar to palm trees: a tap root is developed. *Development Dioecious plants, sporophylls collected in unisexual strobili.
- The habitat is represented by a single family, a species of ginkgo biloba. *Build: Tall deciduous tree. The leaves have a fan-shaped lobed plate, sitting on a thin petiole. Ginko is bred as an ornamental tree. *Features of development: Dioecious plants. Fertilization is carried out by motile spermatozoa.
- Habitat in arid and desert areas. * Structural features: Branched evergreen leafless shrubs or shrubs with opposite leaves. * Features of development: After fertilization, a seed appears, surrounded by a fleshy pericarp.
- They are oxygen providers organic matter; purify the air; serve as a habitat for valuable species of animals and birds; give food to animals. They perform an important water protection function. In biogeocenoses, they perform the function of producers.
Which are characterized by the presence of ovules with the subsequent development of the seed, but do not form flowers and fruits. These are the main signs of gymnosperms. The most ancient and primitive representatives of this division appeared in the late Devonian period from one of the fern species. At the end of the Paleozoic period, gymnosperms reached their peak, while in the process of evolution they displaced spore plants. To this day, only a few representatives of this group have survived in nature, since the gymnosperms are the ancestors of the currently most common flowering (angiosperms) plants that are more adapted to life on Earth. The difference between angiosperms and gymnosperms is that in angiosperms the seeds are located in the ovary, while in gymnosperms the ovules, which later transform into seeds, do not have an isolated container, but are covered with thin scales and attached to the stem.
The department of gymnosperms includes 4 classes: coniferous, ginkgo, gneto, cycad. Gymnosperms include about 800 modern species. The overwhelming majority of the species of this department (more than 500) make up the class of conifers that appeared on our planet at the end of the Carboniferous period. They grow on all continents. Nearly 95% of the world's forests consist of only coniferous trees or are mixed.
Most gymnosperms are evergreens, rare species are deciduous trees or shrubs, some are lianas. Plants of this department have leaves of various shapes: from scaly, needle-like to branched, bilobed, pinnate. The structure of seeds of gymnosperms is similar. In these plants, the ovules (ovules), consisting of a megasporangium and a protective shell, are located openly on the inside of the scaly leaves. In conifers, such leaves with adjacent ovules are like a spiral and form a cone. Thus, the seeds of plants of the group described above seem to be naked, there is no ovary, hence the name comes from the gymnosperms. Conifers have male and female cones, for example, in monoecious pine they are located on the same plant. Fertilization of the female gametophyte by the male and the initial stages of sporophyte development are carried out inside the ovule. The zygote develops into a seed embryo. A mature seed is surrounded by a protective shell and contains an embryo consisting of a root, a bud and embryonic leaves (cotyledons), as well as a supply of nutrients that are necessary for germination. All gymnosperms reproduce by seeds.
The value of gymnosperms in nature is very great. These plants form huge areas of coniferous and mixed forests, enriching the air with oxygen. Forests regulate the rate of snowmelt, the water level in rivers, reduce the noise and strength of winds, and fix sandy soils. The forest is a habitat for many animals, some feed on shoots, seeds and cones of coniferous trees. For humans, gymnosperms of coniferous plants are of invaluable practical importance. The wood of plants of the above-described group of "soft" types is used as a raw material for the manufacture of paper and as timber from which furniture, sleepers, poles, bridges, etc. are made. Until now, coniferous wood is often used as fuel. Coniferous trees release into the air a large number of phytoncides - volatile substances that inhibit the development of pathogens. Therefore, sanatoriums and hospitals are located in coniferous forests to treat people suffering from respiratory diseases. Medicinal preparations are obtained from parts of coniferous trees - activated carbon, camphor, as well as essential oils for use in perfumery, the confectionery industry, and medicine. And the seeds of the Siberian pine are called "pine nuts" and eat them.
The diversity of gymnosperms is considered using a multimedia presentation. The slide show depicting gymnosperms is commented on with a short message. I consider it necessary to introduce students to gymnosperms growing not only in Russia, but also on the territory of other states.
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Features of the organization Seeds appear in gymnosperms. These are more perfect than spores, units of reproduction and settlement, since they have an embryo and reserve nutrients necessary at the first stages of its development. Dense shells protect the seed from adverse factors, many of which are detrimental to spores. Seed plants have acquired advantages in the struggle for existence, which determined their flourishing in the drying up of the climate.
Ancestors of gymnosperms: the oldest representatives of the ferns. It is among them that there are heterosporous tree-like forms with secondary wood, which could give rise to gymnosperms. Gymnosperms did not originate from true (typical) ferns, but from one of the lateral branches of the most ancient fern-like plants.
Gymnosperms have a stem, root and leaves. They form seeds by which they reproduce and spread. Gymnosperms are wind-pollinated plants, their reproduction does not depend on water. Due to this, seed plants are currently the conquerors of land. Gymnosperms in the bark and wood have resin canals filled with resin and essential oils. The needle-like or scaly leaves are covered with a tough cuticle. The stomata are embedded in the tissue, which reduces the evaporation of water.
The most common in Russia Spruce Pine
Juniper
Siberian and Dahurian larch
Fir and Siberian pine
Ephedra - undersized shrub
Cypress - the tree of the Mediterranean
Thuja grows there
Cryptomeria is loved by the Chinese and Japanese
Conifers of the southern hemisphere. Araucaria
Welwitschia from the Namib Desert
Liana gnetum
cycad
Ginkgo biloba
Consider pine and fir cones. Why are these plants called gymnosperms?
Male cones Female cones
The use of conifers Furniture, paper are made from coniferous wood; it is used in the construction of buildings, the manufacture of musical instruments, pencils. Coniferous resin is used to obtain rosin, turpentine. Coniferous fragrances are used in the manufacture of creams, shampoos, and soaps. Larch gives a person wood that does not rot in water and is not inferior in strength to metal.
These plants form vast forests (taiga), and also decorate streets and city parks. Less resistant to air pollution.
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