volatility of the winged achene. Determine which tier these plants belong to. Indicate what environmental conditions are necessary for the reproduction and spread of this plant. Draw a conclusion about the adaptability of spruce (pine) to the conditions of existence in the forest biogeocenosis. Help me please.
What determines the specificity of the activity of biological catalysts - enzymes? what is the mechanism of action of cell receptorssurface?
How do monosaccharides combine to form polymers?
what monosaccharides are included in di- and polysaccharides?
What is the biological significance of lipoids?
8. What level of organization of living nature represents the totality of all ecosystems of the globe in their interconnection9. Which of the listed organs are homologous
10. The appearance of what sign in a person is classified as atavism
11. Which pair of aquatic vertebrates confirms the possibility of evolution based on convergent similarity?
12. The similarity between the functions of chloroplasts and mitochondria lies in what happens in them
13. Name the form of natural selection due to which the number of eyes and the number of fingers on the limbs of vertebrates remains constant for a long time
14. The creative nature of natural selection in evolution is manifested in
15. Name the form of natural selection that results in the loss of wings in some birds and insects
16. Which molecules contain phosphorus, which is necessary for all living organisms?
17 Paleontological evidence of evolution includes
18. The highest concentration of living matter is observed
19. What structures are missing in the skin cells of onion scales
20. Founder of scientific taxonomy (classification)
21. In a DNA molecule, the number of nucleotides with thymine is ...% of the total number. What is the percentage of nucleotides with cytosine in this molecule
22. During the process of photosynthesis, plants
23. The remainder of the third eyelid in the corner of a person’s eye - an example
24. Which cell organelles contain a wide variety of enzymes involved in the breakdown of biopolymers into monomers?
25. The distribution area of reindeer in the tundra zone is a criterion
26. The small pond snail is an intermediate host
27. The highest concentration of toxic substances in an environmentally polluted ground-air environment can be found in
28. Which organelle ensures the transport of substances in the cell?
29. Non-cellular life forms include
30. The intermediate nature of inheritance of a trait manifests itself when
31 The greenhouse effect on Earth is a consequence of increased concentrations in the atmosphere
32. The most acute form of struggle for existence
33. Genetic heterogeneity of individuals in a population increases
34. The development of multicellular organisms from a zygote serves as evidence
35. Human atavisms include the appearance
36. Identify organisms that enter into competitive relationships
37.What happens during photosynthesis
38. The similarity of the structure and activity of cells of organisms of different kingdoms of living nature is one of the provisions
39. The structure and functions of the plasma membrane are determined by the molecules that make up it
40. Establish a correspondence between the form of natural selection and its features
Gymnosperms (Gymnospermae) are the most ancient and still thriving group of seed plants, occupying an intermediate position between ferns and flowering plants. Previously, researchers classified all seed plants that do not form flowers into a separate division or even into a class of the division of seed plants (Spermatophyta). Currently, many scientists are inclined to divide the group of gymnosperms into several independent divisions.
All gymnosperms are trees or shrubs, often reaching enormous sizes. Some gymnosperms are highly branched and bear many small (often scale-like) leaves. Others are weakly branched and have large feathery leaves. Most gymnosperms lack vessels in the xylem and companion cells in the phloem. On the other hand, the tissues of gymnosperms are more complex than those of pteridophytes.
All gymnosperms are heterosporous plants; microsporophylls and macrosporophylls differ greatly in shape, size and structure. In the most primitive seed ferns they grew freely on ordinary shoots; in all other gymnosperms they are located on shortened shoots - strobili, usually dioecious. Microspores in seed plants develop in the pollen sac and are called pollen grains or dust particles. They are transferred to the female gametophyte, usually with the help of the wind, germinating inside after hitting the megasporangium. Inside the megasporangium, called the ovule, a megaspore develops; After fertilization by a male gamete, the ovule turns into a seed. The female gametophyte, of course, depends to a very large extent on the parent plant, but is resistant to dehydration to a much greater extent than the fern gametophyte. The nutrient reserve surrounding the seed is used by the zygote during germination; the seeds may remain dormant until favorable conditions occur. Fruits are not formed, but the seed can develop various adaptations that facilitate their distribution.
Gymnosperms are known from the Upper Devonian. Representatives of most orders are found in the Carboniferous and Permian, and their heyday occurs in the Mesozoic.
The oldest of the seed plants are progymnospermophyta. They combined an evolutionarily advanced stem structure with primitive lateral shoots, not much different from the shoots of psilophytes. Instead of true leaves, they developed forked, leafless branches. The progymnosperms apparently still reproduced by spores, but were already on their way to forming seeds.
Significantly more complex in structure were seed ferns(Pteridospermophyta or Lyginodendrophyta), now classified as an independent department. These were tree-like plants, the appearance and structure of the leaves resembled real ferns, but reproduced with the help of seeds. The development of the embryo most likely occurred after the seed fell to the ground. The large stems of seed ferns contained secondary xylem; pinnate leaves differed from true ferns only in the structure of the epidermis, stomata and petioles. Sometimes seed ferns are classified as cycads.
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 characteristics of gymnosperms. The most ancient and primitive representatives of this department appeared in the late Devonian period from one of the species of ferns. At the end of the Paleozoic period, gymnosperms reached their peak, and in the process of evolution, displacing spore plants. Only a few representatives of this group have survived to this day in nature, since gymnosperms are the ancestors of the currently most common flowering (angiosperm) plants, more adapted to life on Earth. The difference between angiosperms and gymnosperms is that in angiosperms the seeds are located in the ovary, and 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 rod.
The department of gymnosperms includes 4 classes: conifers, ginkgo, opium, cycads. Gymnosperms include about 800 modern species. The overwhelming majority of species in this department (more than 500) constitute the class of coniferous plants that appeared on our planet at the end of the Carboniferous period. They grow on all continents. Almost 95% of the Earth's forests consist only of 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 scale-like, needle-shaped to branched, bilobed, pinnate. The structure of gymnosperm seeds is similar. In these plants, the ovules (ovules), consisting of a megasporangium and a protective shell, are located openly on the inside of the scale-like leaves. In conifers, such leaves with adjacent ovules are like a spiral and form a cone. Thus, the seeds of the plants described above seem to be naked, there is no ovary, hence the name - the gymnosperm division. Conifers have male and female cones, for example, in the monoecious pine they are located on the same plant. Fertilization of the female gametophyte by the male and the initial stages of sporophyte development take place inside the ovule. A seed embryo is formed from the zygote. 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 importance of gymnosperms in nature is very great. These plants form vast areas of coniferous and mixed forests, enriching the air with oxygen. Forests regulate the speed of snow melting, the water level in rivers, weaken the noise and strength of winds, and stabilize sandy soils. The forest is the habitat of many animals, some of which feed on shoots, seeds and cones of coniferous trees. For humans, gymnosperms coniferous plants are of invaluable practical importance. The wood of plants of the above-described group, such as “soft” species, is used as raw material for making 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 large amounts of phytoncides into the air - volatile substances that suppress the development of pathogens. Therefore, sanatoriums and hospitals are located in coniferous forests to treat people suffering from respiratory diseases. Medicines 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 Siberian pine are called “pine nuts” and are eaten.
Among the highest representatives of the plant kingdom is the department of Gymnosperms. In this article you will learn what the structural features of gymnosperms are, get acquainted with their characteristics, and find interesting facts about them.
general characteristics
A structural feature of this plant division is the presence of ovules, which are subsequently transformed into a seed, but the flower and fruit are absent.
Gymnosperms are among the oldest on the planet. They originated from ferns and the first representatives of this department date back to the late Devonian period. They reached their greatest peak of development at the end of the Paleozoic period.
The life forms of this department are mainly trees and shrubs. Their distinctive characteristic is that they are all evergreens. Although there are species of deciduous trees and vines.
An organ such as a leaf in these plants has various forms:
- scaly;
- needle-shaped;
- feathery;
- bilobed;
- branched.
The ovules are located freely inside the scale-like leaves. In the Conifer family, they form a spiral-shaped cone in which dicotyledonous seeds ripen.
TOP 4 articleswho are reading along with this
The cones of coniferous plants are male and female. Pollen grains form in the male cone, which are transferred by wind to the female cone.
Classification
- conifers (55 genera, 560 species);
- oppressive (3 genera, 70 species);
- cycads (20 species);
- ginkgo (1 type).
The most common class is Conifers. They grow on all continents of the planet. Such trees and shrubs have scaly or needle-like leaves. There are no vessels in wood, but there are tracheids (elongated wood cells). All representatives of the Coniferous class secrete resin, which helps heal wood damage.
The Conifer class has seven families, the most common of which is the Pine family. Examples of gymnosperms in this family are pine, spruce, fir, and larch. The cypress family (cypress, juniper, thuja) is no less famous.
Family Pine
Two species of this family are widely known: Scots pine and Norway spruce. Below we offer you a description of the most famous pine trees.
Pine - light-loving plant. Its crown is located mainly at the very top of the tree. The height reaches 50 meters. The leaves are needle-shaped, located on short shoots. The lifespan of needles is 2-3 years, after which they fall off, being replaced by new needles. Pines are unpretentious to the soil and can grow in any conditions, adapting to them. Thus, on sandy soils, the roots of a tree go deep, while in swampy areas they are located on the surface.
Norway spruce grows in the European part of Russia. The crown is characterized by a cone-shaped shape. This is a shade-tolerant tree that lives on clay soils. The needles are short, located on elongated shoots. The lifespan of needles is 7-9 years, after which exchange occurs.
Larch - a coniferous tree with falling needles. It is flat, soft enough, so it falls off in the winter.
Fir very similar to spruce, but the needles are longer and not so prickly. The cones grow vertically, like candles.
Sequoia is the tallest conifer native to North America. Its height can reach 112 meters.
Rice. 3. Representatives of the conifer family.
The meaning of gymnosperms
To understand in detail the meaning of these plants, we offer the following table:
|
Name |
Meaning in nature |
Meaning for humans |
|
– absorb carbon dioxide, releasing oxygen; – perform a climate-forming function; – protect soils from erosion; - a source of food and habitat for many animals. |
Manufacturing of furniture, used in pharmacology, arrangement of recreational areas. |
|
|
Construction material, landscape design. |
||
|
They make paper, a source of vitamin C, a medicinal plant, and use it in landscape design. |
||
|
Larch |
Violin making, building material, landscape design. |
What have we learned?
Gymnosperms are the most ancient plants on the planet. They are distinguished from the angiosperm division by the absence of a flower and a protective covering around the seed. Life forms are represented by tree crops and shrubs. The most numerous class is Conifers. Their leaves are modified into needles, which are evergreen. Representatives of the Pine family are widely used as building materials and in pharmacology. They perfectly purify the air, enriching it with oxygen. Using this material, you can recall the topics studied in biology for the 6th grade and prepare for the test.
Test on the topic
Evaluation of the report
Average rating: 3.9. Total ratings received: 773.
The first seed plants were the now extinct seed ferns, which gave rise to gymnosperms. Gymnosperms are ancient seed plants on the path of biological progress. They appeared on Earth over 350 million years ago, long before the emergence of angiosperms. Scientists believe that gymnosperms descended from ancient heterosporous seed ferns that did not survive to this day. Imprints of seed ferns are found in deep layers of the earth's crust.
Structure of a pine branch
Pine branch
The structure of a female pine cone
In spring, small reddish cones can be seen on the tops of young shoots. These are female bumps. The female cone consists of an axis, or rod, on which the scales are located. On the scales of female cones, unprotected, as if naked (hence the name - gymnosperms), ovules lie, in each of them an egg is formed.
The structure of a female pine cone
The structure of a male pine cone
On the same branches on which the female ones are located, there are also male cones. They are located not at the top of the young shoot, but at their base. Male cones are small, oval, yellow and collected in close groups.
The structure of a male pine cone
Each male cone consists of an axis on which scales are also located. On the underside of each scale there are two pollen sacs in which pollen matures - a collection of dust particles in which male reproductive cells - sperm - are later formed.
The structure of a mature pine cone
Fertilization in pine trees occurs a year after pollen hits the female cones. And the seeds fall out after another six months, at the end of winter. By this time, the mature female cone becomes brown in color and reaches 4-6 cm.
The structure of a mature pine cone
When the scales of a mature female cone are pulled apart, it becomes clear that the seeds lie in pairs on the upper side of the scales, at their base. The seeds lie open, bare. Each pine seed is equipped with a transparent filmy wing, which ensures its transfer by the wind.
The process of pollination and fertilization in pine. (Development cycle)
Reproduction: sexual - by seeds.
Reproduction occurs in two stages: the process of pollination and the process of fertilization.
Pollination process
- Pollen settles on the ovules of the female cone.
- Pollen penetrates into the ovule through the pollen duct.
- The scales close and are glued together with resin.
- Preparation for fertilization.
- When pollen germinates, it forms sperm and a pollen tube.
Fertilization process
Fertilization occurs in the ovule 12 months after pollination.
- The sperm fuses with the egg, resulting in the formation zygote.
- Develops from a zygote embryo.
- From the entire ovule - seed.
The cone grows and gradually becomes lignified, its color becomes brown. Next winter, the cones open and the seeds spill out. They can remain dormant for a long time and germinate only in favorable conditions.
Pine seedlings look very peculiar when they have just emerged from the seed. These are small plants whose stem is shorter than a matchstick and no thicker than an ordinary sewing needle. At the top of the stem there is a bunch of very thin cotyledon needles radiating in all directions. Pine has not one or two of them, like flowering plants, but much more - from 4 to 7.
Pine seed sprout
Thus, plants belonging to the division Gymnosperms differ from all other plants in that they produce seeds. Internal fertilization, the development of the embryo inside the ovule and the appearance of the seed are the main biological advantages of seed plants, which gave them the opportunity to adapt to terrestrial conditions and achieve higher development than seedless higher plants.