As you know, in 1675, i.e., more than three hundred years ago, A. Leeuwenhoek discovered "animalcules" (animals), which were later named ciliates. Since 1820, the name Protozoa has been established, which in Greek means “simple animals”. Zoologist K. Siebold considered them a special type of the animal kingdom and distinguished two classes: ciliates and rhizopods. He also determined that the simplicity of their organization corresponds to one cell. Since then, the unicellularity of the protozoa has become universally recognized, and the names "unicellular" and "protozoa" have become synonymous.

According to the level of organization, all living organisms are classified into two groups. The usual division into unicellular and multicellular organisms required clarification after the electron microscope was used to study the structure of organisms and new research methods appeared. Questions arose about the main differences that determine the levels of development, as well as about the plans of the building. Therefore, it is necessary to consider the organization of protozoa - a paraphyletic group that unites representatives of the organic world, previously attributed to plants, animals and fungi, but having their own specific features.

Spontaneous generation

The nature of protozoa has long been a subject of controversy. Some scientists considered them as living molecules, or simple complexes of such molecules that are capable of spontaneous generation, i.e., arise on their own. Few teachings adhered to these views, especially since the brilliant experiments of L. Spalanzani in the 18th century. L. Pasteur in the 19th century refuted the idea of ​​spontaneous generation.

Cellularization

Other scientists considered the protozoa to be very complexly organized creatures, which can be structurally compared with highly organized animals. They saw the reason for this in the fact that in the organism of multicellular organisms there are structures that do not have division into cells, for example, syncytia. Based on such views, the zoologist J. Hadji in the 50-60s of the XX century. even put forward the theory of the origin of multicellular animals by cellularization. Having discovered the similarity of ciliates with the most primitive ciliary worms, the so-called intestinalless, Hadji suggested that when the parts of the body of the ciliates containing organelles are separated and partitions are formed between them, a multicellular organism arises. Therefore, by its nature, ciliates are comparable to the whole organism of lower multicellular organisms. However, after electron microscopy studies, it was proved that the theory of cellularization relies only on external analogies and convergent similarities.

Cell theory T. Schwann

From the standpoint of the cell theory developed by M. Schleiden and T. Schwann, protozoa are single-celled organisms. According to modern scientists who adhere to these views, protozoa are cells that are functionally organisms. However, functions cannot exist separately from certain structures. Thus, the modern definition of protozoa as microscopic unicellular animals, which are physiologically independent organisms, does not correspond to the current level of knowledge. A satisfactory definition of protozoa can be given after answering the following questions: are protozoa only unicellular organisms? Are they always microscopically small? Are they exclusively animals? Are they organisms only in a physiological sense?

The subkingdom Unicellular (Protozoa) unites animals whose body consists of one cell. It performs the functions of an independent organism. The cell of the simplest consists of cytoplasm, organelles, one or more nuclei. In it there is an exchange of substances with the external environment, the processes of reproduction in development.

Many unicellular organisms have special organelles (movement, nutrition, excretion) that have arisen as a result of adaptation to the environment.

Cell- this is a self-reproducing formation, separated from its environment by a plasma membrane, which contributes to the regulation of the exchange between the internal and external environment.

The simplest animals are a thriving and diverse group (about 70,000 species) - inhabitants of water bodies and moist soil. Mostly they are part of the zooplankton - a collection of the smallest animals that live in marine and freshwater reservoirs. On land, they are also found in the aquatic environment - in soil drip water, as well as in the liquid medium inside multicellular animals and plants. Although soil protozoa can significantly affect the number of bacteria, their value is still incomparably less than that of protozoa in fresh and marine waters.

Many of the simplest animals are as small and simple as some of the cells of large animals. But they differ from them in that they are able to live independently. Unicellular animals are a well-coordinated organism that provides nutrition, respiration, excretion, reproduction, growth, development and metabolism. In his protoplasm there is, as it were, a division of labor: each of its separate, smaller formations performs its own specific task.

For example, the nucleus regulates the vital activity of the entire unicellular organism and reproduces itself, due to which new daughter organisms are formed; in the digestive vacuole, food is digested; the contractile vacuole removes excess water and substances harmful to the body dissolved in it.

Under adverse conditions, many protozoa stop eating, lose their organs of movement, become covered with a thick shell and form a cyst. With the onset of favorable conditions, unicellular ones take on their former appearance.

According to the name Protozoa, only animals should be included in this sub-kingdom. But the modern system of protozoa contains green flagellates (botanists consider them algae), myxomycetes and plasmodiophorids (according to mycologists, these are fungi), etc. In this regard, the ancient protozoa can most likely be considered as the initial group that gave rise to and fungi, and plants, and animals. Therefore, at present, it should be considered recognized to distinguish a special kingdom of protists and contrast it with the kingdoms of plants and animals. The allocation of the kingdom of protists belongs to the famous zoologist and evolutionist E. Haeckel (1866). Protozoa, on the other hand, can be distinguished as a subkingdom in the protist system.

Unicellular organisms have come a long way of evolution, during which their great diversity has arisen. Depending on the complexity of the structure and methods of movement, several types of protozoa are distinguished. material from the site

• Sarkozhgutikontsy (Sarcomastigophores).
  • Sarcode.

From the time of Linnaeus to the present day, protozoa have attracted the attention of scientists for various reasons. There was even a special science - protozoology.

Life on Earth appeared billions of years ago, and since then living organisms have become more complex and diverse. There is a lot of evidence that all life on our planet has a common origin. Although the mechanism of evolution is not yet fully understood by scientists, its very fact is beyond doubt. This post is about how life on Earth developed from the simplest forms to humans, as our distant ancestors were many millions of years ago. So, from whom did man come?

The Earth arose 4.6 billion years ago from a cloud of gas and dust that surrounded the Sun. In the initial period of the existence of our planet, the conditions on it were not very comfortable - many more debris flew in the surrounding outer space, which constantly bombarded the Earth. It is believed that 4.5 billion years ago, the Earth collided with another planet, resulting in the formation of the Moon. Initially, the Moon was very close to the Earth, but gradually moved away. Due to frequent collisions at this time, the Earth's surface was in a molten state, had a very dense atmosphere, and the surface temperature exceeded 200°C. After some time, the surface hardened, the earth's crust formed, the first continents and oceans appeared. The age of the most ancient explored rocks is 4 billion years.

1) The most ancient ancestor. Archaea.

Life on Earth appeared, according to modern concepts, 3.8-4.1 billion years ago (the earliest found traces of bacteria are 3.5 billion years old). How exactly life arose on Earth is still not reliably established. But probably already 3.5 billion years ago, there was a unicellular organism that had all the features inherent in all modern living organisms and was a common ancestor for all of them. From this organism, all its descendants inherited structural features (they all consist of cells surrounded by a membrane), a way to store the genetic code (in double-helixed DNA molecules), a way to store energy (in ATP molecules), etc. From this common ancestor There were three main groups of unicellular organisms that still exist today. First, bacteria and archaea split among themselves, and then eukaryotes evolved from archaea - organisms whose cells have a nucleus.

Archaea have hardly changed over billions of years of evolution, probably the most ancient human ancestors looked about the same

Although archaea gave rise to evolution, many of them have survived to this day almost unchanged. And this is not surprising - since ancient times, archaea have retained the ability to survive in the most extreme conditions - in the absence of oxygen and sunlight, in aggressive - acidic, salty and alkaline environments, at high (some species feel great even in boiling water) and low temperatures, at high pressures, they are also able to feed on a wide variety of organic and inorganic substances. Their distant highly organized descendants cannot boast of this at all.

2) Eukaryotes. Flagella.

For a long time, extreme conditions on the planet prevented the development of complex life forms, and bacteria and archaea reigned supreme on it. Approximately 3 billion years ago, cyanobacteria appeared on Earth. They begin to use the process of photosynthesis to absorb carbon from the atmosphere, releasing oxygen in the process. The released oxygen is first spent on the oxidation of rocks and iron in the ocean, and then begins to accumulate in the atmosphere. 2.4 billion years ago there was an "oxygen catastrophe" - a sharp increase in the oxygen content in the Earth's atmosphere. This leads to big changes. For many organisms, oxygen is harmful, and they die out, being replaced by those that, on the contrary, use oxygen for breathing. The composition of the atmosphere and the climate are changing, it is getting much colder due to a drop in greenhouse gases, but an ozone layer appears that protects the Earth from harmful ultraviolet radiation.

About 1.7 billion years ago, eukaryotes evolved from archaea - single-celled organisms whose cells had a more complex structure. Their cells, in particular, contained a nucleus. However, the resulting eukaryotes had more than one predecessor. For example, mitochondria, important building blocks of the cells of all complex living organisms, evolved from free-living bacteria taken over by ancient eukaryotes.

There are many varieties of unicellular eukaryotes. It is believed that all animals, and hence humans, descended from unicellular organisms that learned to move with the help of a flagellum located behind the cell. The flagella also help filter water in search of food.

Choanoflagellates under a microscope, according to scientists, it was from such creatures that all animals once originated

Some species of flagellates live by uniting in colonies; it is believed that the first multicellular animals once originated from such colonies of protozoa.

3) Development of multicellular. Bylateria.

Approximately 1.2 billion years ago, the first multicellular organisms appeared. But evolution is still slowly advancing, in addition to the development of life is hindered. So, 850 million years ago, global glaciation begins. The planet has been covered with ice and snow for more than 200 million years.

The exact details of the evolution of multicellular organisms are, unfortunately, unknown. But it is known that after some time the first multicellular animals were divided into groups. Sponges and lamellar sponges that have survived to this day without any special changes do not have separate organs and tissues and filter nutrients from the water. Coelenterates are slightly more complicated, having only one cavity and a primitive nervous system. All other more developed animals, from worms to mammals, belong to the group of bilateria, and their distinguishing feature is the bilateral symmetry of the body. When the first bilateria appeared is not known for certain, it probably happened shortly after the end of the global glaciation. The formation of bilateral symmetry and the appearance of the first groups of bilateral animals probably took place between 620 and 545 million years ago. Findings of fossil imprints of the first bilaterians date back to 558 million years ago.

Kimberella (imprint, appearance) - one of the first species of bilateria discovered

Shortly after their appearance, bilateria are divided into protostomes and deuterostomes. Almost all invertebrates—worms, molluscs, arthropods, etc.—are descended from protostomes. The evolution of deuterostomes leads to the appearance of echinoderms (such as sea urchins and stars), hemichordates, and chordates (which include humans).

Recently, the remains of creatures called Saccorhytus coronarius. They lived about 540 million years ago. By all indications, this small (only about 1 mm in size) creature was the ancestor of all deuterostomes, and therefore of man.

Saccorhytus coronarius

4) The appearance of chordates. First fish.

540 million years ago, the "Cambrian explosion" takes place - in a very short period of time, a huge number of various types of marine animals appear. The fauna of this period has been well studied thanks to the Burgess Shale in Canada, where the remains of a huge number of organisms from this period have been preserved.

Some of the Cambrian period animals found in the Burgess Shale

Many amazing animals were found in the slates, unfortunately long extinct. But one of the most interesting finds was the discovery of the remains of a small animal called pikaya. This animal is the earliest found representative of the chordate type.

Pikaya (remains, drawing)

Pikaya had gills, a simple intestine and circulatory system, and small tentacles near the mouth. This small animal, about 4 cm in size, resembles modern lancelets.

The appearance of the fish was not long in coming. The first animal found that can be attributed to fish is Haikouichthys. He was even smaller than the pikaya (only 2.5 cm), but he already had eyes and a brain.

This is what haikouichthys looked like

Pikaya and Haikouichthys appeared between 540 and 530 million years ago.

Following them, many larger fish soon appeared in the seas.

The first fossil fish

5) The evolution of fish. Armored and first bony fishes.

The evolution of fish went on for quite a long time, and at first they were not at all the dominant group of living creatures in the seas, as they are today. On the contrary, they had to escape from such large predators as scorpions. Fish appeared, in which the head and part of the body were protected by a shell (it is believed that the skull subsequently developed from such a shell).

The first fish were jawless, probably feeding on small organisms and organic debris by drawing in and filtering water. It was only about 430 million years ago that the first fish with jaws appeared - placoderms, or armored fish. Their head and part of their body were covered with a bone shell covered with leather.

ancient armored fish

Some of the armored fish became large and began to lead a predatory lifestyle, but a further step in evolution was made thanks to the appearance of bony fish. Presumably, the common ancestor of the cartilaginous and bony fishes that inhabit the modern seas descended from the armored fish, and the armored fish themselves, which appeared at about the same time as the acanthodes, as well as almost all jawless fish, subsequently died out.

Entelognathus primordialis - a likely intermediate form between armored and bony fish, lived 419 million years ago

Guiyu Oneiros, who lived 415 million years ago, is considered the very first of the discovered bony fish, and therefore the ancestor of all land vertebrates, including humans. Compared to predatory armored fish, reaching a length of 10 m, this fish was small - only 33 cm.

Guiyu Oneiros

6) The fish come to land.

While fish continued to evolve in the sea, plants and animals of other classes had already made their way to land (traces of the presence of lichens and arthropods on it were found as early as 480 million years ago). But in the end, fish also took up the development of land. Two classes originated from the first bony fishes - ray-finned and lobe-finned. Most modern fish are ray-finned, and they are perfectly adapted to life in the water. Lobe-finned, on the contrary, adapted to life in shallow water and in small fresh water, as a result of which their fins lengthened, and the swim bladder gradually turned into primitive lungs. As a result, these fish have learned to breathe air and crawl on land.

Eustenopteron ( ) is one of the fossil lobe-finned fish, which is considered the ancestor of land vertebrates. These fish lived 385 million years ago and reached a length of 1.8 m.

Eusthenopteron (reconstruction)

- another lobe-finned fish, which is considered a likely intermediate form of evolution of fish into amphibians. She could already breathe with her lungs and crawl out onto land.

Panderichthys (reconstruction)

Tiktaalik, the found remains of which date back to 375 million years ago, was even closer to amphibians. He had ribs and lungs, he could turn his head apart from his torso.

Tiktaalik (reconstruction)

One of the first animals, which are no longer classified as fish, but as amphibians, were ichthyostegs. They lived about 365 million years ago. These small animals, about a meter long, although they already had paws instead of fins, could still hardly move on land and led a semi-aquatic lifestyle.

Ichthyostega (reconstruction)

At the time of the emergence of vertebrates on land, another mass extinction occurred - the Devonian. It began about 374 million years ago, and led to the extinction of almost all jawless fish, armored fish, many corals and other groups of living organisms. Nevertheless, the first amphibians survived, although it took them more than one million years to more or less adapt to life on land.

7) The first reptiles. synapsids.

The Carboniferous period, which began about 360 million years ago and lasted 60 million years, was very favorable for amphibians. A significant part of the land was covered with swamps, the climate was warm and humid. Under such conditions, many amphibians continued to live in or near water. But about 340-330 million years ago, some of the amphibians decided to master drier places. They developed stronger limbs, more developed lungs appeared, the skin, on the contrary, became dry so as not to lose moisture. But in order to really live far from water for a long time, one more important change was needed, because amphibians, like fish, spawned, and their offspring had to develop in an aquatic environment. And about 330 million years ago, the first amniotes appeared, that is, animals capable of laying eggs. The shell of the first eggs was still soft, not hard, however, they could already be laid on land, which means that the offspring could already appear outside the reservoir, bypassing the tadpole stage.

Scientists are still confused about the classification of amphibians of the Carboniferous period, as well as whether to consider some fossil species already early reptiles, or still amphibians, having acquired only some features of reptiles. One way or another, these either the first reptiles, or reptilian amphibians looked something like this:

Vestlotiana is a small animal about 20 cm long, combining the features of reptiles and amphibians. Lived about 338 million years ago.

And then the early reptiles split off, giving rise to three large groups of animals. Paleontologists distinguish these groups according to the structure of the skull - according to the number of holes through which muscles can pass. Figure from top to bottom of the skull anapsis, synapsid and diapsida:

At the same time, anapsids and diapsids are often combined into a group sauropsids. It would seem that the difference is quite insignificant, however, the further evolution of these groups went in completely different ways.

More advanced reptiles evolved from sauropsids, including dinosaurs and then birds. Synapsids also gave rise to a branch of animal-like lizards, and then to mammals.

The Permian period began 300 million years ago. The climate became drier and colder, and early synapsids began to dominate on land - pelycosaurs. One of the pelycosaurs was Dimetrodon, which was up to 4 meters long. He had a large “sail” on his back, which helped to regulate body temperature: to quickly cool down when overheated or, conversely, to quickly warm up by exposing his back to the sun.

It is believed that the huge Dimetrodon is the ancestor of all mammals, and hence man.

8) Cynodonts. The first mammals

In the middle of the Permian period, therapsids descended from pelycosaurs, already more like animals than lizards. Therapsids looked like this:

Typical therapsid of the Permian period

During the Permian period, many species of therapsids, large and small, arose. But 250 million years ago there was a powerful cataclysm. Due to a sharp increase in volcanic activity, the temperature rises, the climate becomes very dry and hot, lava floods large areas of land, and harmful volcanic gases fill the atmosphere. The Great Permian Extinction occurs, the largest mass extinction of species in the history of the Earth, up to 95% of marine and about 70% of land species die out. Of all therapsids, only one group survives - cynodonts.

Cynodonts were mostly small animals, from a few centimeters to 1-2 meters. Among them were both predators and herbivores.

Cynognathus is a species of predatory cynodonts that lived about 240 million years ago. It was about 1.2 meters long, one of the possible ancestors of mammals.

However, after the climate improved, the cynodonts were not destined to capture the planet. Diapsids seized the initiative - dinosaurs evolved from small reptiles, which soon occupied most of the ecological niches. Cynodonts could not compete with them, they were crushed, they had to hide in holes and wait. Revenge was not taken soon.

However, cynodonts survived as best they could and continued to evolve, becoming more and more like mammals:

Evolution of cynodonts

Finally, the first mammals evolved from cynodonts. They were small and were presumably nocturnal. Dangerous existence among a large number of predators contributed to the strong development of all the senses.

Megazostrodon is considered one of the first true mammals.

Megazostrodon lived about 200 million years ago. Its length was only about 10 cm. Megazostrodon fed on insects, worms and other small animals. Probably, he or another similar animal was the ancestor of all modern mammals.

Further evolution - from the first mammals to humans - we will consider in.

Food chains and trophic levels

Consider the biotic structure of an ecosystem. Within the ecosystem, energy-containing organic substances are created by autotrophic organisms and serve as food (a source of matter and energy) for heterotrophs.

Feeding on each other, living organisms carry out the transfer of energy and matter and form food chains. Nutritional relationships are also called trophic (from the Greek trophy - life)

Trophic (food) chain – this is a chain of successive transfer of matter and energy equivalent to it from one organism to another, and each of its links is trophic level(Greek trophos - food). The first trophic level is occupied by autotrophs, or the so-called primary producers. Organisms of the second trophic level are called primary consumers, the third - secondary consumers, etc. There are usually four or five trophic levels and rarely more than six.

The last trophic level - decomposers - they carry out mineralization, and they can decompose all trophic levels, starting from 2.

There are 2 types of food chains:

Grazing chains (pasture) - begin with living phototrophs. for example

Grass → mouse → owl → hawk

Chains of decomposition (detrital) - begin with detritus. For example,

Dead animal → fly larvae → common frog → already.

The arrow shows the transfer of energy.

Eating chains predominate in aquatic ecosystems, while decay chains predominate in land ecosystems.

In reality, food chains are much more complex, because an animal can feed on organisms of different types. Some animals eat other animals and plants, omnivores (man, bear). Chains intertwine in a complex way and form food webs. for example

Food chains can be thought of as ecological pyramids, with rectangles representing the level's ecological efficiency stacked one above the other. The height of the blocks is the same, and the length of each is proportional to the productivity of each level (number, mass, amount of energy). The height of the pyramid corresponds to the length of the food chain.

The ecological pyramid is a trophic chain. The longer the chain, the less important in terms of biomass, number or energy are the frugivores at the top of the pyramid. Only about 0.1% of the energy received from the Sun is bound in the process of photosynthesis. Due to this energy, several thousand grams of dry organic matter per 1 m3 per year are synthesized. More than half of the energy associated with photosynthesis is immediately consumed in the process of respiration of the plants themselves. Another part of it is carried by a number of organisms along food chains. When animals eat plants, most of the energy contained in food is spent on various life processes, turning into heat and dissipating. Only 5-20% of food energy passes into the newly built substance of the animal's body. Let us illustrate: with the pyramids of numbers, biomasses and energies, a very simple human food chain.

Pyramid of numbers (Elton's pyramid):

Tasks and exercises for the school course of general ecology 1

Continuation. See No. 15/2002

(Printed with abbreviations)

Ways of impact of organisms on the environment

1. It's been raining. A bright hot sun came out from behind the clouds. In which territory will the soil moisture content be higher after five hours (soil type is the same): a) in a freshly plowed field; b) in a ripe wheat field; c) in an ungrazed meadow; d) in a grazing meadow? Explain why.
(Answer: in. The thicker the vegetation cover, the less the soil heats up and therefore the less water will evaporate.)

2. Explain why ravines are more often formed in non-forest natural zones: steppes, semi-deserts, deserts. What human activity leads to the formation of ravines?
(Answer: the root systems of trees and shrubs, to a greater extent than grassy vegetation, retain the soil when it is washed away by water flows, therefore, in places where forest and shrub vegetation grows, ravines form less often than in fields, steppes and deserts. In the complete absence of vegetation (including grassy), any flow of water will cause soil erosion. When vegetation is destroyed by man (plowing, grazing, construction, etc.), increased soil erosion will always be observed.)

3.* It has been established that in the summer after the heat, more precipitation falls over the forest than over the nearby vast field. Why? Explain the role of the nature of vegetation in shaping the level of aridity of certain areas.
(Answer: over open spaces, the air heats up faster and stronger than over a forest. Rising up, hot air turns raindrops into steam. As a result, when it rains, less water flows over a vast field than over a forest.
Areas with sparse vegetation or those without it at all are heated up by the sun's rays, which causes increased evaporation of moisture, and as a result, depletion of groundwater reserves, soil salinization. Hot air rises. If the desert area is large enough, then this can significantly change the direction of air currents. As a result, less precipitation falls on bare areas, which leads to even more desertification of the territory.)

4.* In some countries and islands, the importation of live goats is prohibited by law. The authorities motivate this by the fact that goats can harm the nature of the country and change the climate. Explain how it can be.
(Answer: goats eat not only grass, but also leaves, as well as tree bark. Goats can reproduce quickly. Having reached a high number, they mercilessly destroy trees and shrubs. In countries with insufficient rainfall, this causes further desiccation of the climate. As a result, nature is impoverished, which negatively affects the country's economy.)

Adaptive forms of organisms

1.* Why do wingless forms predominate among insects on small oceanic islands, while winged ones prevail on the nearby mainland or large islands?
(Answer: small oceanic islands are blown by strong winds. As a result, all flying small animals, unable to withstand strong winds, are blown into the ocean and die. In the course of evolution, insects living on small islands have lost the ability to fly.)

Adaptive rhythms of life

1. List the abiotic environmental factors known to you, the values ​​of which periodically and regularly change over time.
(Answer: illumination during the day, illumination during the year, temperature during the day, temperature during the year, humidity during the year, and others.)

2. Select from the list those habitats in which animals do not have diurnal rhythms (provided that they live only within one specific environment): lake, river, cave waters, soil surface, ocean floor at a depth of 6000 m, mountains, human intestines , forest, air, soil at a depth of 1.5 m, river bottom at a depth of 10 m, bark of a living tree, soil at a depth of 10 cm.
(Answer: cave waters, ocean floor, soil at a depth of 1.5 m.)

3. In what month do chinstrap Adélie penguins usually breed in European zoos - May, June, October or February? Explain the answer.
(Answer: October is the time of spring in the Southern Hemisphere.)

4. Why did the experiment with the acclimatization of the South American llama in the Tien Shan mountains (where the climate is similar to the habitual conditions of the animal's native places) end in failure?
(Answer: mismatch of annual cycles - cubs of animals were born in a new habitat in the fall (in the homeland of animals at this time it is spring) and died in the cold winter from starvation.)

CHAPTER 2. COMMUNITIES AND POPULATIONS

Types of organism interactions

2. From the proposed list, make up pairs of organisms that in nature can be in mutualistic (mutually beneficial) relationships with each other (the names of organisms can be used only once): bee, boletus mushroom, sea anemone, oak, birch, hermit crab, aspen, jay, clover , boletus mushroom, linden, nodule nitrogen-fixing bacteria.
(Answer: bee - linden; boletus mushroom - birch; actinia - hermit crab; oak - jay; boletus mushroom - aspen; clover - nodule nitrogen-fixing bacteria.)

3. From the proposed list, make pairs of organisms between which trophic (food) connections can form in nature (the names of organisms can be used only once): heron, willow, aphid, amoeba, hare, ant, aquatic bacteria, wild boar, frog, currant , sundew, ant lion, mosquito, tiger.
(Answer: heron - frog; hare-hare - willow; aphid - currant; amoeba - water bacteria; ant lion - ant; tiger - boar; sundew - mosquito.)

4. Lichens are an example of a biotic relationship:

(Answer: a.)

5. Pairs of organisms cannot serve as an example of a predator-prey relationship (choose the correct answer):

a) pike and crucian carp;
b) lion and zebra;
c) freshwater amoeba and bacteria;
d) ant lion and ant;
e) jackal and vulture.

(Answer: e.)

6.

A. The interaction of two or more individuals, the consequences of which are negative for some, and indifferent for others.
B. The interaction of two or more individuals, in which one uses the remains of the food of others without harming them.
B. Mutually beneficial interaction of two or more individuals.
D. The interaction of two or more individuals, in which one provides shelter to the other, and this does not bring harm or benefit to the owner.
D. Cohabitation of two individuals that do not directly interact with each other.
E. The interaction of two or more individuals with similar needs for the same limited resources, which leads to a decrease in the vital indicators of the interacting individuals.
G. The interaction of two or more organisms, in which some feed on living tissues or cells of others and receive from them a place of permanent or temporary residence.
H. The interaction of two or more individuals, in which one eats the other.

(Answer: 1 - B; 2 - D; 3 - E; 4 - A; 5 - G; 6 - B; 7 - F; 8 - Z.)

7. Why do you think progressive technologies for planting trees in poor soil involve contamination of the soil with certain types of fungi?
(Answer: a symbiotic relationship is formed between these mushrooms and the tree. Mushrooms quickly form a very branched mycelium and braid the roots of trees with their hyphae. Thanks to this, the plant receives water and mineral salts from a huge area of ​​​​the soil surface. To achieve such an effect without mycelium, the tree would have to spend a lot of time, matter and energy on the formation of such an extensive root system. When planting in a new place, symbiosis with a fungus significantly increases the chances of a tree to take root safely.)

8.* Name the organisms that are human symbionts. What role do they play?
(Answer: representatives of bacteria and protozoa that live in the human intestine. In 1 g of the contents of the large intestine, there are 250 billion microorganisms. Many substances that enter the human body with food are digested with their active participation. Without intestinal symbionts, normal development is impossible. A disease in which the number of symbiotic organisms of the intestine decreases is called dysbacteriosis. Microorganisms also live in tissues, cavities and on the surface of human skin.)

9.* The relationship of an adult spruce and a neighboring oak seedling is an example:

(Answer: a.)

Laws and consequences of food relations

1. Match the proposed concepts and definitions:

A. An organism that actively seeks out and kills relatively large prey that can flee, hide, or resist.
B. An organism (usually small in size) that uses the living tissues or cells of another organism as a source of food and habitat.
B. An organism that consumes numerous food objects, usually of plant origin, for which it does not spend much energy searching.
D. An aquatic animal that filters water through itself with numerous small organisms that serve as food for it.
C. An organism that seeks out and eats relatively small, incapable of escaping and resisting food objects.

(Answer: 1 - B; 2 - G; 3 - A; 4 - D; 5 - V.)

2. Explain why in China in the middle of the twentieth century. following the destruction of sparrows, the grain harvest dropped sharply. After all, sparrows are grain-eating birds.
(Answer: adult sparrows feed mainly on seeds, but chicks need protein food for their development. Feeding offspring, sparrows collect a huge number of insects, including pests of crops. The destruction of sparrows caused pest outbreaks, which led to a reduction in crops.)

Laws of competitive relations in nature

1. For each proposed pair of organisms, select a resource (from the following) for which they can compete: lily of the valley - pine, field mouse - common vole, wolf - fox, perch - pike, buzzard - tawny owl, badger - fox, rye - blue cornflower, saxaul - camel thorn, bumblebee - bee.
Resources: burrow, nectar, wheat seeds, water, hares, light, small roach, potassium ions, small rodents.
(Answer: lily of the valley and pine - potassium ions; field mouse and common vole - wheat seeds; the wolf and the fox are hares; perch and pike - small roach; buzzard and tawny owl are small rodents; badger and fox - hole; rye and cornflower - light; saxaul and camel thorn - water; bumblebee and bee - nectar.)

2.* Closely related species often live together, although it is generally accepted that there is the most intense competition between them. Why, in these cases, is there no displacement by one species of another?
(Answer: 1 – very often closely related species living together occupy different ecological niches (they differ in the composition of their preferred food, in the way they obtain food, use different microhabitats, and are active at different times of the day); 2 - competition may be absent if the resource for which the species compete is in excess; 3 - displacement does not occur if the number of a competitively stronger species is constantly limited by a predator or a third competitor; 4 - in an unstable environment in which conditions are constantly changing, they can alternately become favorable for one or another species.)

3.* In nature, Scotch pine forms forests on relatively poor soils in swampy or, conversely, dry places. Planted by human hands, it grows well on rich soils with medium moisture, but only if a person takes care of the plantings. Explain why this happens.
(Answer: usually under these conditions, other types of trees win in competition (depending on the conditions, these can be aspen, linden, maple, elm, oak, spruce, etc.). When caring for plantings, a person weakens the competitive power of these species by weeding, cutting down, etc.)

Populations

1. Select a value that estimates the population density index of a population:

a) 20 individuals;
b) 20 individuals per hectare;
c) 20 individuals per 100 breeding females;
d) 20%;
e) 20 individuals per 100 traps;
e) 20 individuals per year.

(Answer: b.)

2. Choose a value that estimates the birth rate (or death rate) of the population of the population:

a) 100 individuals;
b) 100 individuals per year;
c) 100 individuals per hectare;
d) 100.

(Answer: b.)

3. White hares and brown hares living in the same territory are:

a) one population of one species;
b) two populations of two species;
c) two populations of the same species;
d) one population of different species.

(Answer: b.)

4. On an area of ​​100 km2, forest felling was carried out annually. At the time of the organization of the reserve, 50 moose were noted in this territory. After 5 years, the number of moose increased to 650 heads. After another 10 years, the number of moose decreased to 90 and stabilized in subsequent years at the level of 80–110 heads.
Determine the density of the moose population: a) at the time of the creation of the reserve; b) 5 years after the creation of the reserve; c) 15 years after the creation of the reserve. Explain why the number of moose first increased sharply, and then fell and stabilized later.
(Answer: a – 0.5 individuals/km2; b – 6.5 individuals/km2; c – 0.9 individuals/km2. The number of moose has increased due to protection in the reserve. Later, the number decreased, since logging is prohibited in the reserves. This led to the fact that after 15 years, small trees growing on old clearings grew, and the food supply of elk decreased.)

5. The hunters found that in the spring, 8 sables lived on an area of ​​20 km2 of the taiga forest, of which 4 were females (adult sables do not form permanent pairs). Every year, one female brings an average of three cubs. The average mortality of sables (adults and calves) at the end of the year is 10%. Determine the number of sables at the end of the year; density in spring and at the end of the year; mortality rate per year; birth rate per year.
(Answer: the number of sables at the end of the year is 18 individuals; spring density - 0.4 individuals / km2; density at the end of the year 0.9 individuals/km2; mortality rate per year - 2 individuals (according to calculations - 1.8, but the real value, of course, will always be expressed as a whole number); birth rate per year - 12 individuals.)

6.* Is the population: a) a group of cheetahs in the Moscow Zoo; b) a family of wolves; c) perches in the lake; d) wheat in the field; e) snails of the same species in one mountain gorge; e) bird market; g) brown bears on Sakhalin Island; h) a herd (family) of deer; i) red deer in the Crimea; j) a colony of rooks; k) all spruce plants? Justify the answer.
(Answer: yes - c, e, f, i. A population is a group of individuals of the same species, interconnected, living in the same territory for a long time (several generations). A population is a natural grouping that has a specific sex, age, and spatial structure.)

7.* How can one explain the fact that if in a fight between two (non-fighting) dogs one turns its unprotected neck, the other does not grab it, while in a fight between a lynx and a dog such behavior will be fatal for the dog that turned its neck?
(Answer: aggression between individuals of the same species, as a rule, is aimed at maintaining the hierarchical and spatial structure of the population, and not at the destruction of fellow tribesmen. A population, like a species, is a single whole, and the well-being of one individual largely determines the well-being of the population, species. The lynx will simply eat the dog.)

8.* In the forest, scientists evenly placed traps for white hares. A total of 50 animals were caught. They were marked and released. A week later, the capture was repeated. We caught 70 hares, of which 20 were already tagged. Determine the number of hares in the study area, assuming that the animals marked for the first time were evenly distributed throughout the forest.
(Answer: 50 marked individuals were to be distributed among the total number of hares (X) living in the study area. Their share in the resampling should also reflect their share in the total population, i.e. 50 is to X like 20 is to 70.
Let's solve the proportion:
50: X = 20: 70; X \u003d 70x 50: 20 \u003d 175.
Thus, the estimated number of hares in the study area is 175 individuals.
This method (Lincoln index, or Petersen index) is used to determine the number of secretive animals that cannot be directly counted. The result of the calculations may have a fractional value, but it must be remembered that the real number of animals is always expressed as an integer value. In addition, this method has its own errors, which must also be taken into account. It is more logical to talk, for example, about the number of 170-180 individuals.)

Demographic structure of the population

1. Explain why up to 30% of individuals can be removed from the wild boar population without the risk of destroying it, while the permissible shooting of elk should not exceed 15% of the population?
(Answer: the female wild boar on average brings from 4 to 8 (sometimes up to 15) piglets, and the female elk - 1-2. Therefore, the recovery of the wild boar population is proceeding at a faster pace.)

2. Which organisms have a simple and which have a complex age structure of populations?
(Answer: a simple age structure of populations is distinguished by organisms whose life cycle does not exceed one year, and reproduction occurs once in a lifetime and is timed to seasonal changes in the environment. These are, for example, annual plants, a number of insect species, etc. Otherwise, the age structure of populations can be complex.)

3. Explain why a significant spring death of adult shrews will lead to a sharp and prolonged decline in the population, while the complete destruction of all adult May beetles that emerged in the spring will not lead to a similar result.
(Answer: the population of shrews in spring is represented exclusively by adult animals of the last year of birth. May beetles, whose larvae develop in the soil for 3–4 years, have a complex age structure of the population. When adults die one spring the next year, they will be replaced by beetles that have developed from another generation of larvae.)

4. Build age pyramids for Russia (140 million) and Indonesia (190 million) using the data provided.

To be continued

1 The signs "*" and "**" mark tasks of increased complexity, having a cognitive and problematic nature.

In any trophic chain, not all food is used for the growth of an individual, i.e. for the accumulation of its biomass. Part of it is spent to meet the energy costs of the body (breathing, movement, reproduction, maintaining body temperature).

At the same time, the biomass of one link cannot be completely processed by the next, and in each subsequent link of the trophic chain, a decrease in biomass occurs.

On average, it is believed that only about 10% of the biomass and the energy associated with it passes from each trophic level to the next, i.e. the production of organisms of each subsequent trophic level is always less on average 10 times the production of the previous level.

So, for example, on average, 100 kg of biomass of herbivorous animals (consumers of the first order) is formed from 1000 kg of plants. Carnivores (second-order consumers) that eat herbivores can synthesize 10 kg of their biomass from this amount, while predators (third-order consumers) that feed on carnivores synthesize only 1 kg of their biomass.

Thus , the total biomass, the energy contained in it, as well as the number of individuals progressively decrease as one ascends the trophic levels.

This pattern has been named ecological pyramid rules.

This phenomenon was first studied by C. Elton (1927) and named by him pyramid of numbers or Elton's pyramid.

ecological pyramid - this is a graphic representation of the relationship between producers and consumers of different orders, expressed in units of biomass (pyramid of biomass), number of individuals (population pyramid) or the energy contained in the mass of living matter (pyramid of energy) ( Fig.6).

Fig.6. Diagram of the ecological pyramid.

The ecological pyramid expresses the trophic structure of ecosystems in geometric form.

There are three main types of ecological pyramids: the pyramid of numbers (numbers), the pyramid of biomass and the pyramid of energy.

1) pyramids of numbers, based on the count of organisms of each trophic level; 2) biomass pyramids, which use the total mass (usually dry) of organisms at each trophic level; 3) energy pyramids, taking into account the energy intensity of organisms of each trophic level.

energy pyramids are considered the most important, since they directly refer to the basis of nutritional relationships - the flow of energy necessary for the life of any organisms.

Pyramid of numbers (numbers)

The pyramid of numbers (numbers) or Elton's pyramid reflects the number of individual organisms at each trophic level.

The population pyramid is the simplest approximation to the study of the trophic structure of an ecosystem.

At the same time, the number of organisms in a given area is first calculated, grouping them by trophic levels and presenting them as a rectangle, the length (or area) of which is proportional to the number of organisms living in a given area (or in a given volume, if it is an aquatic ecosystem).

The population pyramid can have a regular shape, i.e. taper upwards (correct or straight), and may be an inverted top down (inverted or reversed) Fig.7.

right (straight) inverted (inverted)

(pond, lake, meadow, steppe, pasture, etc.) (temperate forest in summer, etc.)

Fig.7. Pyramid of numbers (1 - correct; 2 - inverted)

The population pyramid has a regular shape, i.e. narrows when moving from the level of producers to higher trophic levels, for aquatic ecosystems (pond, lake, etc.) and terrestrial ecosystems (meadow, steppe, pasture, etc.).

For example:

1,000 phytoplankton in a small pond can feed 100 small crustaceans - first-order consumers, which in turn will feed 10 fish - second-order consumers, which will be enough to feed 1 perch - third-order consumers.

The abundance pyramid for some ecosystems, such as temperate forests, is inverted.

For example:

in the forest of the temperate zone in summer, a small number of large trees - producers supply food to a huge number of small-sized phytophagous insects and birds - consumers of the first order.

However, in ecology, the population pyramid is rarely used, since due to the large number of individuals at each trophic level, it is very difficult to display the structure of the biocenosis on the same scale.

biomass pyramid

The biomass pyramid reflects more fully the nutritional relationships in the ecosystem, since it takes into account the total mass of organisms (biomass) of each trophic level.

Rectangles in biomass pyramids display the mass of organisms of each trophic level, per unit area or volume.

Pyramids of biomass, as well as pyramids of abundance, can be not only regular in shape, but also inverted (reversed) Fig.8.

Consumers of the 3rd order

Consumers of the 2nd order

Consumers of the 1st order

Producers

right (straight) inverted (inverted)

(terrestrial ecosystems: (aquatic ecosystems: lake,

meadow, field, etc.) pond and especially marine

ecosystems)

Fig.7. Pyramid of biomass (1 - correct; 2 - inverted)

For most terrestrial ecosystems (meadow, field, etc.), the total biomass of each subsequent trophic level of the food chain decreases.

This creates a pyramid of biomasses, where producers significantly predominate, and gradually decreasing trophic levels of consumers are located above them, i.e. the biomass pyramid has a regular shape.

For example:

on average, out of 1000 kg of plants, 100 kg of the body of herbivorous animals are formed - consumers of the first order (phytophages). Carnivorous animals - consumers of the second order, eating herbivores, can synthesize 10 kg of their biomass from this amount. And predators - consumers of the third order, feeding on carnivores, synthesize only 1 kg of their biomass.

In aquatic ecosystems (lake, pond, etc.), the biomass pyramid can be inverted, where the biomass of consumers prevails over the biomass of producers.

This is explained by the fact that in aquatic ecosystems, the producer is microscopic phytoplankton, which rapidly grows and reproduces), which continuously supplies live food in sufficient quantities to consumers that grow and reproduce much more slowly. Zooplankton (or other animals that feed on phytoplankton) accumulate biomass over years and decades, while phytoplankton have an extremely short life span (several days or hours).