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§ 5. Variety of plants

Plants differ from each other in color and shape of stems, leaves, flowers and fruit, life expectancy and other features.

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Fruit formation. The fruits serve to protect the seeds and to spread them. They are formed only in angiosperms, which is where the name of these plants comes from.

The fruit consists of one or more seeds (sometimes a significant number). The seed is surrounded by a pericarp, which consists of three layers - outer, middle and inner. It is formed either by the walls of the ovary (cherry, plum, etc.), or other parts of the flower also take part in its formation: the receptacle, the base of the stamens, sepals, petals (for example, apple fruits).

Variety of fruits. Fruits are very diverse in shape, size, color, number of seeds. Depending on the water content in the pericarp, they are divided into dry and juicy. In dry fruits, the pericarp is dry, leathery or lignified, with an insignificant water content, while in juicy fruits it is fleshy and juicy. A single-pistil flower produces one simple fruit (e.g. wheat, cherry). If there are several pistils in a flower, a corresponding number of small fruitlets are formed. Together they form a composite or complex fruit (for example, in raspberries, blackberries). Sometimes, with the close arrangement of flowers in the inflorescence, individual fruits grow together to form a seed (mulberry, pineapple).

Juicy fruits include berry-like fruits, drupes and some others. There are different types of berry fruits such as berry, apple.

The berry is a multi-seeded fruit with a juicy middle and inner layers of the pericarp, and its outer layer forms a protective skin (in currants, grapes, gooseberries).

Apple is a juicy multi-seeded fruit, the pulp of which is formed by an overgrown receptacle (in an apple, pear, quince, mountain ash); pumpkin is a fruit in which the middle and inner layers are juicy, and the outer one is colored, hard (for pumpkin, cucumber, melon).

The drupe consists of a hard woody bone (inner layer of the pericarp), a middle layer that can be juicy (in plums, cherries, hawthorns), more or less dry (in almonds) or fibrous (in coconut trees), and thin skin (outer layers) ...

In raspberries and blackberries, a composite multi-seeded fruit is a complex drupe formed from individual fruitlets. During ripening, these small fruits can separate from each other. In wild strawberries, numerous small dry fruits are interspersed into the surface of an overgrown fleshy receptacle, and in rose hips, they are located inside it. Thus, it is also a prefabricated fruit.

Dry fruits are subdivided into expanding, mainly polyspermous (for example, bean, pod, pod, capsule), and non-expanding, containing mainly one seed (for example, walnut, achene, caryopsis).

The pod opens along the top and bottom seams from the top to the base, and the seeds are attached to both halves of the pericarp (in peas, beans, soybeans).

The pod also opens at both seams, but from the base to the top. The seeds are located on a membranous septum inside the fruit (in cabbage, mustard, radish). The pod is similar in structure to a pod, but shorter and wider (in a shepherd's purse, saffron milk cap).

The box can be opened in different ways: in henbane - with a lid; in poppies - with denticles at the top; in dope - numerous longitudinal slits.

A nut is a fruit with a hard lignified pericarp, inside which a seed lies freely (for example, in a hazelnut).

In the caryopsis, the leathery pericarp grows tightly with the seed (for example, in rye, wheat).

Achene is a fruit in which the lignified pericarp only adheres to the seed, but does not grow together with it (for example, in a sunflower, calendula, string).

Very often, the fruits and seeds of many plants have various outgrowths: thorns, bristles, needles (horse chestnut, dope, string). In many plant species, these outgrowths play not only a protective role, but also serve to spread fruits and seeds.

Fish, crayfish, whales, jellyfish live on the ground and in the air, animals and, and in the soil - earthworms, moles and bears. The habitat for some animals is other living organisms and plants.

photo: Bill Gracey

The fauna of our planet is represented by unique organisms: from single-celled crumbs, which can only be viewed with a microscope, to giant whales, whose mass reaches 150 tons. Due to constant evolution, animal organisms are endowed with unique properties: they move, feed, defend themselves from enemies, reproduce and raise offspring in various conditions.

Animal classification

The following taxa are distinguished in the animal kingdom:

Family;

Species are combined into a genus, families into a row, classes into a type. In addition to these taxa, intermediate concepts are used: subtypes, subclasses, and others. All living organisms are divided into:

The simplest;

Insects;

Amphibians;

Reptiles;

Mammals.

photo: David Shannon

The meaning of animals

Representatives of the animal world are of great importance for the entire planet: they participate in the cycle of substances in nature, pollinate plants, are distributors of fruits and seeds. act as natural orderlies, in addition, they regulate the number of herbivorous organisms. : animals are bred and hunted by the commercial method for obtaining meat, skins, fur, milk and eggs, animals are used for research, medical and scientific purposes. In laboratory mice, hamsters, rats and guinea pigs, the effect of certain drugs is studied, monkeys are attracted in experiments with table cells. Bee and snake venom are used for medicinal purposes.

photo: Rob Escott

Features of the settlement of animals

Various factors affect the density of settlement of representatives of the animal world. These include climate, terrain, human activities and relationships between different species. Adaptation to environmental conditions is expressed in the characteristics of living organisms. So, in order to find favorable conditions for living, feeding and reproducing, many organisms travel great distances. These movements are called migrations. As an example, we can give the following example: fish of the order of salmon grow up in the sea, and breed in the upper reaches of rivers. The fry hatched from the eggs of these fish are carried back to the sea by the river current, where their further growth takes place.

photo: Jiya Aggarwal

If you move from the poles to the equator, it becomes noticeable that the number of species of living organisms increases. The biggest is. For example, there are more than 40 species of parrots alone, and thousands of butterflies.

Evolution of biodiversity

In the history of the animal world, there have always been periods of decline and increase in biodiversity. They are characterized by the emergence of new species that have appeared to replace others. Scientists learn about these stages from archaeological excavations: fossils and prints. So, in the Precambrian, 670 million years BC, soft-bodied invertebrates, annelids and coelenterates dominated. For the Cambrian and Silurian, 590-438 million years BC, marine invertebrates with shells are characteristic, insects reigned in the Late Carboniferous and Cenozoic, amphibians prevailed in the Carboniferous and Triassic, reptiles were most numerous in the Permian and Cretaceous, and mammals flourished in the Cenozoic.

The flowering and extinction of species is a natural process that occurs under the influence of climate change in certain regions and throughout the planet as a whole. Scientists assume that most species of living organisms will die out sooner or later. Some are transformed into evolutionarily more perfect species, but others will not be able to adapt to new environmental conditions. The latter are threatened with extinction.

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The living nature around us in all its diversity is the result of a long historical development of the organic world on Earth, which began almost 3.5 billion years ago.

The biological diversity of living organisms on our planet is great.

Each species is unique and unrepeatable.

For example, there are more than 1.5 million species of animals. However, according to some scientists, only in the class of insects there are at least 2 million species, the vast majority of which are concentrated in the tropical zone. The number of animals of this class is also great - it is expressed in numbers with 12 zeros. And different unicellular planktonic organisms only in 1 m 3 of water can be up to 77 million individuals.

Rainforests are characterized by a particularly high biological diversity. The development of human civilization is accompanied by an increase in anthropogenic pressure on the natural communities of organisms, in particular, the destruction of the greatest tracts of forests in the Amazon, which leads to the extinction of a number of species of animals and plants, to a decrease in biodiversity.

Amazonia

A special science - systematics - helps to understand all the diversity of the organic world. Like a good collector, according to a certain system, classifies the objects he collects, a taxonomist classifies living organisms on the basis of signs. Every year scientists discover, describe and classify all new types of plants, animals, bacteria, etc. Therefore, taxonomy as a science is constantly evolving. So, in 1914 a representative of an then unknown invertebrate animal was described for the first time, and only in 1955 the Russian zoologist AV Ivanov (1906-1993) substantiated and proved his belonging to a completely new type of invertebrates - pogonophores.

A. V. Ivanov

Pogonophores

Development of taxonomy (creation of artificial classification systems).

Attempts to classify organisms were undertaken by scientists in ancient times. The outstanding ancient Greek scientist Aristotle described over 500 species of animals and created the first classification of animals, dividing all animals known then into the following groups:

I.Animals without blood: soft-bodied (corresponds to cephalopods); soft shell (crustaceans); insects; cranial (shell molluscs and echinoderms).

II. Animals with blood: viviparous tetrapods (corresponds to mammals); birds; oviparous tetrapods and legless (amphibians and reptiles); viviparous legless with pulmonary respiration (cetaceans); scaled legless, gill-breathing (fish).

By the end of the 17th century. a huge amount of material was accumulated about the diversity of forms of animals and plants, which required the introduction of the concept of the species; for the first time this was done in the works of the English scientist John Ray (1627-1705). He defined a species as a group of morphologically similar individuals and tried to classify plants based on the structure of vegetative organs. However, the famous Swedish scientist Karl Linnaeus (1707-1778), who in 1735 published his famous work "The System of Nature", is rightfully considered the founder of modern taxonomy. Linney took the structure of the flower as the basis for the classification of plants. He combined closely related species into genera, similar genera into detachments, detachments into classes. Thus, he developed and proposed a hierarchy of systematic categories. In total, scientists have identified 24 classes of plants. To designate the species, K. Linney introduced a double, or binary, Latin nomenclature. The first word means the name of the genus, the second - the species, for example Sturnus vulgaris.

Carl Linnaeus

In different languages, the name of this species is spelled differently: in Russian - common starling, in English - common starling, in German - Gemeiner Star, in French - etourneau sansonnet, etc. Common Latin names of species make it possible to understand who is in question, facilitate communication between scientists from different countries. In the animal system, K. Linney identified 6 classes: Mammalia (Mammals). He placed man and apes in one detachment of Primates; Aves (Birds); Amphibia (Reptiles, or Amphibians and Reptiles); Pisces (Pisces); Insecta (Insects); Vermes (Worms).

The emergence of a natural classification system.

The system of K. Linnaeus, despite all its indisputable advantages, was inherently artificial. It was built on the basis of external similarities between different types of plants and animals, and not on the basis of their true relationship. As a result, completely unrelated species fell into the same systematic groups, but close ones were separated from each other. For example, Linnaeus considered the number of stamens in plant flowers as an important systematic trait. As a result of this approach, artificial groups of plants were created. So, viburnum and carrots, bells and currants fell into one group only because the flowers of these plants have 5 stamens each. Linnaeus placed plants of various types of pollination in one class of monoecious: spruce, birch, duckweed, nettle, etc. However, despite the shortcomings and errors in the classification system, the works of K. Linney played a huge role in the development of science, allowing scientists to navigate in the variety of living organisms.

While classifying organisms according to their external, often the most conspicuous characteristics, K. Linney did not reveal the reasons for this similarity. This was done by the great English naturalist Charles Darwin. In his work "The Origin of Species ..." (1859), he first showed that the similarity between organisms can be the result of a common origin, ie. relationship of species.

Since that time, the taxonomy began to bear an evolutionary burden, and the classification systems built on this basis are natural. This is the unconditional scientific merit of Charles Darwin. Modern taxonomy is based on the commonality of essential morphological, ecological, behavioral, embryonic, genetic, biochemical, physiological and other characteristics of classified organisms. Using these features, as well as paleontological information, the taxonomist establishes and proves the common origin (evolutionary relationship) of the species under consideration, or establishes that the classified species are significantly different and distant from each other.

Systematic groups and classification of organisms.

The modern classification system can be represented in the form of the following scheme: empire, super-kingdom, kingdom, sub-kingdom, type (department - for plants), subtype, class, detachment (order - for plants), family, genus, species. For extensive systematic groups, additional intermediate systematic categories have also been introduced, such as superclass, subclass, superorder, suborder, superfamily, subfamily. For example, the classes of cartilaginous and bony fish are combined into a superclass of fish. In the class of bony fish, subclasses of ray-finned and lobe-finned fish are distinguished, etc. Previously, all living organisms were divided into two kingdoms - Animals and Plants. Over time, organisms were discovered that could not be attributed to any of them. Currently, all organisms known to science are divided into two empires: Precellular (viruses and phages) and Cellular (all other organisms).

Precellular life forms.

There is only one kingdom in the precellular empire - viruses. They are non-cellular life forms that can penetrate and multiply in living cells. For the first time, science learned about viruses in 1892, when the Russian microbiologist DI Ivanovsky (1864–1920) discovered and described the tobacco mosaic virus, the causative agent of tobacco mosaic disease. Since that time, a special branch of microbiology has emerged - virology. Distinguish between DNA-containing and RNA-containing viruses.

Cellular life forms.

The Empire of Cellulars is divided into two super kingdoms (Prenuclear, or Prokaryotes, and Nuclear, or Eukaryotes). Prokaryotes are organisms whose cells do not have a formed (membrane-limited) nucleus. The kingdom of the Drobyanki belongs to prokaryotes, which includes half the kingdom of Bacteria and Blue-green (Cyanobacteria). Eukaryotes are organisms whose cells have a formed nucleus. These include the kingdoms of Animals, Mushrooms and Plants (Fig. 4.1). In general, the empire of the Cellular consists of four kingdoms: Drobyanka, Mushrooms, Plants and Animals. As an example, consider the systematic position of a well-known bird species - the common starling:

Systematic category type Category name

Empire Cellular

Super Kingdom Nuclear

Kingdom of Animals

Under the kingdom of the Multicellular

Type Chordates

Subtype Vertebrates

Superclass Terrestrial vertebrates

Bird class

Subclass Fan-tailed, or real birds

Superorder Typical Birds

Squad Passeriformes

Starling family

Genus True Starling

Common starling species

Thus, as a result of long-term research, a natural system of all living organisms was created.

Nematodes (lat. Nematoda, Nematodes) or roundworms are the second largest group of multicellular animals on Earth (after arthropods), distinguished by their appearance and structure. Formally, they refer to primary cavity worms, but this is an outdated classification.

Morphology

Nematodes are structurally simple organisms. Adult nematodes are composed of approximately 1000 somatic cells, as well as hundreds of cells associated with the reproductive system. These roundworms have been characterized as a "tube within a tube" based on the gastrointestinal tract that runs from the mouth at the front end to the anus located near the tail. Nematodes have digestive, nervous, excretory and reproductive systems, but do not have a secreted circulatory or respiratory system. They range in size from 0.3 mm to over 8 meters.

Reproduction

Most of the nematode species are dioecious with distinct males and females. Although some, such as Caenorhabditis elegans, have androdies, they are represented by hermaphrodites and males. Both sexes have one or two tubular gonads (ovaries and testes, depending on the sex).

Reproduction of nematodes is usually based on mating, although hermaphrodites are capable of self-fertilization. Males are usually smaller than females or hermaphrodites and often have a characteristic curved or fan-shaped tail to support the opposite sex. During mating, one or more chitinous spicules emerge from the cloaca and are inserted into the female's genital opening. This is how the seminal fluid is transferred, which during the process passes along the length of the entire male.

Due to the lack of knowledge about many nematodes, their taxonomy is controversial and has changed several times. In different sources, you can find very different classifications. In most of them, according to outdated information, nematodes are distinguished as a class, although they are already classified as a separate type, which includes several classes. But there is still controversy about this.

Previously, it was a suborder, but now it is allocated as a separate detachment.

All these suborders include several families, which, in turn, are subdivided into genera, and those into species.

Habitat

Roundworms can adapt to any ecosystem, so they can be found in fresh and salt water, soil, in the polar regions and in the tropics. Nematodes are ubiquitous. Scientists have found worms in every part of the earth's lithosphere.

Human infection

Live roundworm in human intestines during colonoscopy

Roundworms enter the body:

When nematodes infect a person, they develop the following symptoms:

1. Stool problems.
2. Vomiting and nausea.
3. Appetite disappears.
4. Dark circles under the eyes.
5. Itching in the anal area.

In the future, nematodes begin to penetrate into many human organs and actively reproduce. As a result, a person begins to feel severe weakness, an allergic reaction may develop, in rare cases, mental abnormalities, and so on. Human nematodes greatly reduce immunity.

Infection of animals

A person can become infected with nematodes from cats, dogs and other animals, if basic hygiene rules are not followed.

Nematode diseases in plants

Brown streaks on the potato stem caused by the nematode Trichodoride.

The most famous types are distinguished:

Particular attention is paid to a highly specialized type of worms - the golden potato nematode (Globodera rostochiensis). Almost everyone who has grown plants of the Solanaceae family at home or in the country is familiar with it. They prefer to settle on the roots of potatoes and tomatoes. The individual develops in the rhizome. Cysts are spread by soil, wind, water and infected tubers. Therefore, when a potato nematode is detected, the infection zone is quarantined.

You should know that the golden potato nematode, like other similar plant pests, is absolutely safe for humans.

Free-living nematodes

In free-living species, development usually consists of four cuticle molts during growth. Different types of these nematodes feed on a very diverse diet - algae, fungi, small animals, feces, dead organisms and living tissues. Free-living marine nematodes are important and abundant members of the meiobenthos (meiofauna, i.e. bottom-dwelling organisms). They play an important role in the decomposition process, aid in the breakdown of nutrients in the marine environment and are sensitive to changes resulting from pollution. It should be noted that the roundworm Caenorhabditis elegans, which lives in the soil, has become a model organism for scientists, i.e. used in various experiments. This is due to the fact that its genome (a set of genes) has long been fully studied, and this makes it possible to observe changes in the organism when manipulating genes.