Lesson objectives: to form students’ understanding of the main directions of evolution, to show the relationship between the paths of evolution; introduce the types of evolutionary changes, the concepts of biological progress and biological regression.
Equipment: tables, diagrams illustrating convergence, aromorphosis, physiological and behavioral adaptations of organisms, disk “Virtual School of Cyril and Methodius. General biology. Grade 11, lesson No. 19. Biological progress and biological regression.”
During the classes
1. Test of knowledge.
Frontal conversation on the following issues:
- Who laid the foundations of scientific systematics? (Carl Linnaeus.)
- List the main systematic groups used in classifying plants? (Species, genus, family, order, division, kingdom.)
- List the main systematic groups used in the classification of animals? (Species, genus, family, order, class, type, kingdom.)
- What is binary nomenclature? (Double species name.)
- On what basis do we classify organisms as the same species? (Organisms must be similar in external and internal characteristics, live in the same territory, and freely interbreed with each other to form fertile offspring.)
- Why is Carl Linnaeus' system called artificial? (Because he did not take into account related relationships between organisms.)
- Why is modern classification called natural? (The modern classification system takes into account the relationship of species to both living and extinct species.)
2. Studying new material.
Natural selection determines the path of evolution. How did the formation of modern systematic groups proceed? Why did the organization of living beings become more complicated in some cases, while in others, on the contrary, became simpler? You can find out the answers to these questions by becoming familiar with the main types of evolutionary changes and the main directions of evolution.
2.1. Types of evolutionary changes.
Parallelism is the process of evolutionary development in a similar direction of two or more initially divergent species. For example, among mammals, cetaceans and pinnipeds, independently of each other, switched to living in the aquatic environment and acquired the corresponding adaptations - flippers.
Convergence is a type of evolutionary change as a result of which unrelated organisms acquire similar characteristics. A classic example of convergent development is the emergence of similar body shapes in sharks, ichthyosaurs, and dolphins. The similarity between unrelated organisms is only external. Birds and butterflies have wings, but the origin of these organs is different. In the first case, these are altered limbs, in the second, folds of skin.
Divergence is the most general type of evolutionary process, the basis for the formation of new systematic groups. Divergence is divergent evolution. The process of divergence is usually represented in the form of an evolutionary tree with diverging branches. A common ancestor gave rise to two or more forms, which in turn became the ancestors of many species and genera. An example of the divergence of forms is the emergence of finches with different morphophysiological characteristics from one or a few ancestral forms on the Galapagos Islands. The divergence of intraspecific forms and species in different habitats is determined by competition in the struggle for the same conditions, the way out of which is dispersal into different ecological niches.
2.3. Main directions of evolution.
The development of living nature went from simple to complex and was progressive. Along with this, species adapted to specific living conditions and specialized. Biological progress is achieved in various ways. A.N. Severtsov called them the main directions of evolutionary progress: aromorphosis, idioadaptation and degeneration.
Aromorphosis is such large, large-scale, evolutionary changes that lead to a general rise in the organization, increase the intensity of life, but are not narrow adaptations to sharply limited conditions of existence. Aromorphoses provide significant advantages in the struggle for existence and make it possible to transition to a new habitat. Aromorphoses in animals include the appearance of viviparity, the ability to maintain a constant body temperature, the emergence of a closed circulatory system, and in plants - the appearance of a flower, a vascular system, and the ability to maintain and regulate gas exchange in the leaves. (Lesson “Biological progress and regression.” Slide 3)
Through aromorphosis, large systematic groups of a rank higher than the family arise in the process of evolution.
Aromorphoses help increase survival and reduce mortality in populations. The number of organisms increases, their range expands, new populations form, and the formation of new species accelerates. All this constitutes the essence of biological progress. Typical aromorphoses in invertebrates are: sexual differentiation, the appearance of a bilateral organization, the emergence of a tracheal respiratory system, the concentration of the central nervous system, the transition to pulmonary respiration; in mammals - the division of the heart into the right and left halves with differentiation of the two circulation circles, an increase in the working capacity of the lungs. The consequence of these aromorphoses is better oxidation of the blood and an abundant supply of oxygen to the organs, and therefore an intensification of the functions of the organs. Differentiation and specialization of the digestive organs leads to a more complete use of nutrients, which enhances metabolic processes, increases overall activity, the emergence of warm-bloodedness, increases the activity of motor organs and improves their design. All these and other aromorphoses are interconnected, and arogenic characteristics turn out to be useful in a wide variety of living conditions. For example, the possession of movable limbs by animals opens up the possibility of their diverse use in the desert, forest, valley, mountains, in water, for digging soil, etc. Or such aromorphoses as the formation of striated muscles, the development of walking limbs and wings in insects. These aromorphoses opened up the possibility for insects to conquer land and partly the air. Major aromorphoses in the development of plants were: the emergence of the epidermis, stomata, conductive and mechanical systems, the natural change of generations in the plant cycle, the formation of flowers, fruits, etc.
Idiomatic adaptation – represents small evolutionary changes that increase the adaptability of organisms to certain environmental conditions. In contrast to aromorphosis, idioadaptation is not accompanied by a change in the basic features of the organization, a general rise in its level and an increase in the intensity of the body’s vital activity. Usually small systematic groups - species, genera, families - arise in the process of evolution through idioadaptation.
Idioadaptation, like aromorphosis, leads to an increase in the number of species, expansion of the range, acceleration of speciation, that is, to biological progress.
Typical idioadaptations in animals are structural features of the limbs (for example, in moles, ungulates, pinnipeds), beak features (in birds of prey, waders, parrots), adaptations of bottom fish (in stingrays, flounders), protective coloring in insects. Examples of idioadaptations in plants include various adaptations to pollination, distribution of fruits and seeds. (Lesson “Biological progress and regression.” Slide 4)
Biological regression is also observed in nature. It is characterized by features that are opposite to biological progress: a decrease in numbers, a narrowing of the range, a decrease in the number of species and populations. As a result, regression often leads to the extinction of the species.
Of the numerous branches of the most ancient amphibians, only those remained that led to the formation of modern classes of amphibians and reptiles. The ancient ferns and many other groups of plants and animals disappeared. (Slide 8)
With the development of human civilization, the causes of biological progress and biological regression are increasingly associated with the changes that humans make to the landscapes of the Earth, disrupting the connections of living beings with the environment that have developed during the process of evolution.
Human activity is a powerful factor in the progress of some species, which are often harmful to him, and the biological regression of others, which are necessary and useful to him. For example, the appearance of insects resistant to pesticides, pathogenic microbes resistant to drugs, the rapid development of blue-green algae in wastewater. When sowing, people invade wildlife, destroying many wild populations over large areas, replacing them with artificial ones. Intensified extermination by humans of many species leads to their biological regression, which threatens them with extinction. (Slide 9.)
2.4. Correlation of evolutionary paths.
Of all the considered ways to achieve biological progress, aromorphoses are the rarest. Aromorphoses can be considered as turning points in the development of life. For groups that have undergone appropriate morphophysiological transformations, new opportunities open up in mastering the external environment.
Each aromorphosis is followed by many idioadaptations, which ensure a more complete use of all available resources and the development of new habitats.
3. Consolidation of the studied material.
3.1. Conversation on issues.
- Do idioadaptations lead to morphological progress? (No. Idiomatic adaptations do not increase the level of organization.)
- Do idioadaptations lead to biological progress? (Various idioadaptations lead to the colonization of different habitats and to enhanced speciation, increase adaptability to specific conditions and abundance, contribute to a wider distribution of a given group and, therefore, lead to biological progress.)
- Give examples of degenerations in the liver fluke and the bovine tapeworm. (The nervous system and sensory organs are simplified; the bovine tapeworm completely lacks a digestive system.)
- Give examples of degenerations in dodder. (Lack of leaves, roots and chlorophyll.)
- Do degenerations lead to biological progress? (Morphophysiological regression can lead to an increase in numbers, increased adaptability to special conditions and a wider distribution of organisms, the emergence of new species and, consequently, to biological progress.)
- What evolutionary paths lead to biological progress? (Aromorphoses lead to an increase in the level of organization and the settlement of new habitats. Then a period of idioadaptations begins, and a large number of new species are formed, well adapted to different specific living conditions. After simplification, a period of idioadaptations also begins. Thus, all three paths lead to biological progress .)
- What evolutionary paths lead to morphophysiological progress? (Only aromorphoses lead to morphophysiological progress.)
3.2. Final testing (based on questions for the lesson “Biological progress and regression. Slide 13).
Biological progress has been studied and is being studied by scientists - biologists.
Scientists are unanimous in the opinion that successful results in the struggle for existence are the progression of organisms.
Development has three directions. In addition, it is believed that this is the only evolutionary path for the emergence of man.
Biological progress is
The fact that the birth rate in a population is higher than the mortality rate, and the number of organisms increases with settlement in new places, indicates the ecological prosperity of the species. A. Severtsov created and characterized the theory of biological progress:
- Organisms adapt to environmental factors.
- The number of representatives of the species is increasing.
- Child groups appear.
- The habitat area is expanding.
- Having gone through a brutal struggle for existence, one systematic unit wins.
Today insects, birds, mammals, and nematodes are progressing.
Paths of biological progress
Organisms progress along three paths or directions, acquiring the necessary adaptations.Arogenesis- acquisition of major morphophysiological changes - aromorphoses, which increase vitality.
At allogenesis organisms do not move to a new level, but adapt to live in special conditions. New species, genera, and families appear.
Catagenesis called the general degradation of individuals, a simplification that helps to survive and reproduce.
Biological progress and regression
When regression occurs, the opposite happens: the number of individuals decreases, the boundaries of the habitat decrease in the same way as the number of population groups. Regression threatens the extinction of a species that does not have the ability to compete and is destroyed through the process of natural selection. Another reason is direct destruction by humans. The remaining rare representatives of wildlife are protected and listed in the Red Book.
Achieving biological progress
Biological progress - types
Adaptations of species help not only to survive. When settling in new habitats, organisms are forced to switch to other food. At the same time, competition with relatives is sharply weakened. Representatives quickly reproduce and disperse, giving rise to the formation of new species. The resulting groups are distinguished by unequal selection effects and different living conditions.
Signs of biological progress
Biological progress is determined by three criteria:
- Increase in the number of organisms of a species.
- Resettlement to new places, expanding the boundaries of the range.
- Formation of new populations, subspecies, species.
The signs form a single connection with each other.
Examples of biological progress
Animal Kingdom:
- acquired bilateral symmetry;
- reproductive system of two types;
- movable limbs;
- the appearance of tracheal breathing in invertebrate animals and alveolar breathing in vertebrate animals;
- Central nervous system and developed parts of the brain;
- 4-chambered heart, systemic and pulmonary circulation, warm-blooded animals.
Transformations in plants:
- chlorophyll use of solar energy;
- integumentary, mechanical and conductive tissues;
- roots, stems, and leaves were identified, allowing the plants to reach land;
- fertilization does not depend on water;
- the seed is protected by the fruit.
Biological progress is characterized
The main evolutionary direction associated with biological progress improves the external and internal structure of organisms. In another case, it changes secondary organs without complicating the structure. Thus, individuals adapt to changed conditions. In the third characteristic, individuals progress, acquiring a more complex organization of life.
Biological progress: aromorphosis
Aromorphosis refers to morphophysiological progress that increases the standard of living:
Biological progress: idioadaptation
During telogenesis, genera, species, orders, and families appear. Adaptations are highly specialized for specific conditions without changing the level of the organization. For example, chameleon, sloth, turtle are additional devices. Mammals have a similar internal structure. Angiosperms are represented by thousands of species and forms. Thanks to aromorphosis, birds acquired a beak, but the size and shape depend on the diet.
Biological progress of animals
With the domestication of animals, people chose productive pets, created acceptable living conditions, and took care of health. Having become domesticated animals, their productivity has increased and they bring healthy offspring, increasing their numbers. There is biological progress.
What is the way to achieve biological progress?
The problem of biological progress
The topic of progress in the organic world remains difficult to understand and often causes discussions among biologists. Considered the key to solving the problem. Scientists Lamarck, Darwin, Haskley put forward scientific hypotheses about the presence of biological progress in nature. And also Rensch, Severtsov, Simpson, Schmalhausen and others. Some evidence is erroneous. The models of Severtsov and Haskley, which are the center of scientific discussions among biologists, are considered models.
Evidence of biological progress
The main directions of development of living nature are biological progress and biological regression. As a result, large systematic units are formed, and the process lasts thousands of years. Evidence of biological progress includes:
- Comparative anatomy: similar structure of vertebrates, homologous organs, atavisms and rudiments.
- The similarity of embryos, proven by Karl Baer.
- Findings of paleontologists.
- The ant has the largest brain in relation to its body.
- The human brain performs 100 thousand chemical reactions.
- The tallest grass, 30 m, is bamboo.
- The human body is marked by 90 rudiments.
- Today there are 10 thousand poisonous plants on the planet.
- Rats go without water longer than camels.
- Snakes have two reproductive organs and sleep for 3 years without food.
- Marine sunfish are capable of laying 5 million eggs at once.
conclusions
Biological progress and regression are the main methods and directions of evolution in which specific orders and genera survive, develop and improve, or disappear.
The idea of the directed nature of evolution following the path of progress, i.e. along the path of improving organisms from simple to complex, from lower forms of life to higher ones, is generally accepted. However, one should not think that progress is the only way of evolutionary changes; in fact, this is only one of the possible directions of evolution.
Modern ideas about the directions of evolution are based on the works of domestic biologists A.N. Severtsov and I.I. Schmalhausen and American paleontologist J.G. Simpson. A.N. Severtsov identified the concepts of biological progress and regression.
Biological progress means the victory of a species or other systematic group in the struggle for existence. Signs of biological progress are an increase in the number of individuals of a given systematic group, expansion of its range and disintegration into subordinate systematic groups. All three signs of biological progress are related to each other. An increase in the number of individuals forces a species (or any other systematic group) to expand the boundaries of its range, to populate new habitats, which leads to the formation of new populations, subspecies, and species.
Biological progress is opposed by biological regression. It is characterized by the opposite signs: a decrease in the number of individuals, a narrowing of the range, a gradual or rapid decrease in the population and species diversity of the group. Biological regression can lead a species to extinction. The general reason for biological regression is a lag in the rate of evolution of a group from the rate of changes in the external environment. Rapid environmental change caused by human activity leads to an increase in the number of species entering a state of biological regression and doomed to extinction (if an environment acceptable to them is not preserved).
The driving forces of evolution operate continuously, resulting in improved adaptations. However, under the influence of human economic activity, the habitat of living beings changes much faster than adaptations are formed. This leads to a reduction in numbers, narrowing of ranges and the threat of extinction of a number of species. The unprecedented speed of human attack on nature leads to such rapid changes in the environment that species that were in a state of biological progress just a few decades ago, unable to keep up with the changes, are undergoing biological regression. Thus, plowing of the steppes leads to a sharp decrease in the number of virgin species: ground squirrels, marmots, steppe pikas, cranes, steppe eagles. Large mammals (especially predators), represented by a small number of individuals that live in a small area, reproduce slowly and do not tolerate human proximity, have minimal chances of survival. These are, for example, the tiger, cheetah, leopard, leopard, polar bear. On the contrary, biological progress is achieved by small fertile animals that are widespread and easily get along with humans. Among mammals, these primarily include a typical urban animal - the pasyuk rat, among birds - the crow, and among insects - the red cockroach.
Biological regression- this is an evolutionary movement in which a reduction in habitat occurs; reduction in the number of individuals due to inability to adapt to the environment; a decrease in the number of species in groups due to pressure from other species, the extinction of a species. The science of paleontology has proven that many species in the past completely disappeared. If, with biological progress, some species develop and spread widely throughout the globe, then with biological regression, species disappear, unable to adapt to environmental conditions.
Causes of biological regression: the disappearance of the ability of organisms to adapt to changes in environmental conditions.
The following are subject to biological regression:
2. Animals leading a sedentary lifestyle.
3. Animals living underground or in caves.
2. Examples of degeneration in organisms leading a sedentary lifestyle.
In animals leading a sedentary lifestyle, the organ of movement functions only during the larval stage; the notochord is reduced. For example, the only representative of a separate type of brachiata - pogonophora - lives on the bottom of the sea and leads a sedentary lifestyle. In 1949, zoologist A.V. Ivanov first found it in the Sea of Okhotsk at a depth of 4 km; it was caught in a net along with fish. The elongated worm-like body of the animal is covered with a cylindrical tube. In the front of the body there are tentacles that periodically extend from the tube to the outside for breathing. The body consists of three sections, in the anterior section there are tentacles (in some species there are up to 200-250), a brain, a heart, and excretory organs. The second section is larger, the third is very long. In the inner part of the sections there are respiratory organs, in the outer part there are outgrowths attached to the tube (Fig. 34).
Rice. 34. Pogonophora: 1 tentacles; 2- head; 3-first section of the body; 4-second body section; 5-third body section; 6-sensitive hairs; 7-back of the body
Pogonophora has a brain and heart, but the mouth and stomach are reduced, and the respiratory organs are the tentacles. Due to their sedentary lifestyle, they do not look like animals. In the inner part of the tentacles there are long thin hairs that are equipped with blood vessels. In the water, the hairs come out of the tube and microorganisms attach to them. When there are a lot of them, the pogonophores pull the hairs inside. Under the influence of enzymes, small organisms are digested and absorbed by internal outgrowths.
The rudimentary intestine in the Pogonophora embryo proves the presence of digestive organs in the ancestors. Due to the digestion process outside the body, the digestive organs of pogonophora were reduced.
The structure of the ascidian is also simplified in the process of evolution due to its sedentary lifestyle. Ascidia belongs to one of the branches of the chordate type - tunicates that live in the sea (Fig. 35).
Rice. 35. Ascidians
The sac-like body of the ascidian is covered with a shell, its sole is attached to the bottom of the sea and leads a motionless lifestyle. There are two holes in the upper part of the body, through the first hole water passes into the stomach, and from the second it comes out. Respiratory organs - gill slits. Reproduces by laying eggs. From the egg, mobile tadpole-like larvae with notochord characteristics develop. As an adult, the ascidian attaches to the bottom of the sea, and the body becomes simpler. It is believed that the ascidian is a highly degraded chordate animal.
3. Examples of degeneration of animals living underground or in caves.
Proteus from the class lives in caves in the former Yugoslavia and southern Austria
amphibians, similar to newt (Fig. 36).
Rice. 36. Proteus
In addition to lungs, it has external gills on both sides of its head. In water, proteas breathe with gills, and on land with lungs. Inhabitants of waters and deep caves, they are serpentine-shaped, transparent, colorless, without pigments. In adults, the eyes are covered by skin, while the larvae have rudimentary eyes. Thus, the ancestors of ascidians had eyes and led a terrestrial lifestyle. In cave organisms, organs of vision and pigments disappeared, and activity decreased.
In flowering plants that transferred to an aquatic environment, the leaf blades became narrow, thread-like, and the conducting tissues stopped developing. The stomata have disappeared, only the flowers have not changed (water buttercup, duckweed, hornwort).
The genetic basis of evolutionary changes leading to simplification of the level of organization is mutation. For example, if the remaining underdeveloped organs - rudiments, albinism (lack of pigments) and other mutations - do not disappear during the process of evolution, then they are found in all members of a given population.
Thus, there are three directions in the evolution of the organic world. Aromorphosis- increasing the level of organization of living organisms; idioadaptation- adaptation of living organisms to environmental conditions without a fundamental restructuring of their biological organization; degeneration- simplification of the level of organization of living organisms, leading to biological regression.
The relationship between the directions of biological evolution. The connection between aromorphosis, idioadaptation and degeneration in the evolution of the organic world is not the same. Aromorphosis occurs less frequently than idioadaptation, but it marks a new stage in the development of the organic world. Aromorphosis leads to the emergence of new highly organized systematic groups that occupy a different habitat and adapt to living conditions. Even evolution follows the path of idioadaptation, sometimes degeneration, which provides organisms with a new habitat for them.
Biological regression
Biological regression- decrease in the number of species, narrowing of the range, decrease in the level of adaptability to environmental conditions.
1.What is the difference between biological regression and biological progress?
2. How many pathways does degeneration have?
3. Give examples of degeneration in animals.
4. What are examples of degeneration in plants?
How do you explain the reasons for the disappearance of the roots and leaves of the dodder?
What and how does dodder eat? Does it form organic matter?
1. Explain the reasons for the transformation of broomrape leaves into scales.
2. Analyze examples of degeneration of pogonophorans leading a sedentary lifestyle.
3. How do pogonophorans digest food if they do not have a digestive organ?
4. What organisms do you know that lead a sedentary lifestyle? Describe them.
Where does Proteus live? Explain with examples of degeneration. Give examples of degeneration in plants living in an aquatic environment. Write a short essay about aromorphosis, idioadaptation, degeneration.
What are biological progress and regression? What are their main features? To find answers to these questions, let's analyze these biological terms in more detail.
Features of development in biology
A. N. Severtsov argued that it is possible to achieve transformations and the emergence of new devices in a variety of ways. He characterized biological progress and regression and gave definitions to these terms.
Characteristics of biological progress
It assumes the victory of another taxonomic group or a certain species in a fierce struggle for existence. Biological progress has certain signs:
- increase in the number of individuals;
- range expansion;
- increase in the number of daughter taxonomic forms.
The listed signs are interconnected. With an increase in the number of individuals, the boundaries of the range of a given species expand, new territories are populated by its representatives, as a result of which new species, subspecies, and populations are formed. Nowadays, birds, many mammals, and insects are in a state of biological progress.
The concept of regress
The main characteristic of biological regression is that this process is the opposite of progress. It also has certain distinctive characteristics that should be mentioned separately:
- a decrease in the number of individuals as a result of the mortality rate exceeding the birth rate;
- decrease in diversity within a species;
- a decrease in the boundaries and integrity of the area, it disintegrates into several separate spots;
- Due to their small numbers, individuals are subject to catastrophic elimination, which can provoke the destruction of the entire group.
Paths of biological progress
Characteristics of biological progress and regression will be incomplete without indicating possible paths of evolutionary changes. A. N. Severtsov noted that there are several options for changing the state of a species or genus. If, in his opinion, biological regression has only one option of existence, then progress is represented in various ways: degeneration, idioadaptation, aromorphosis.
Biological evolution
For a long time, I. I. Shmalgauzen studied the problem of evolutionary processes in biology. It was he who identified the main options for biological progress:
- hypermorphosis;
- allomorphosis;
- aromorphosis;
- hypomorphosis;
- catamorphosis;
- telomorphosis.
Biological regression has no such directions. Aromorphosis is a path of evolution that is accompanied by an increase in the level of vital activity and involves an expansion of the habitat of the genus. Arogenesis is characterized by:
- strengthening activities;
- increased differentiation;
- integration of the body;
- manifestation of active variants of the struggle for existence;
- improvement of the senses and nervous system.
As a result of aromorphosis, changes occur that contribute to the rise of the organization, that is, not biological regression is observed, but development (progress). The species has a chance to transition to new conditions of existence. Examples of arogenesis include a four-chambered heart, the appearance of viviparity, constant body temperature, two circles of blood circulation, and breastfeeding of newborn babies with milk. Biological regression does not have such capabilities. It was through aromorphoses that classes and types appeared and large taxa developed. A. N. Severtsov said that it is aromorphosis that presupposes the complication of the species, its possibility of subsequent self-improvement. What does biological regression lead to? Examples in history indicate that its result is the complete extinction of a species or genus.
Allogenesis involves the formation of specific adaptations during changes in living conditions. In this case, the progression of the organism does not imply a complication of the entire species, and a general increase in energy is not required. Allogenesis leads to species diversity and a significant increase in numbers. For example, mammals have managed to master various living conditions; they can be found in arctic deserts and in the tropics. In addition, their representatives mastered different environments (soil, water, land), which led to a decrease in competition between representatives of different species for habitats and food. But no biological regression occurred. The examples given above, on the contrary, indicate a stable level of organization of living organisms. Thanks to idioadaptation, new genera, species, orders, families appear, and low-ranking taxa arise.
Telogenesis is recognized as a narrow specialization, an adaptation to specific conditions of existence, which does not imply a serious change in the level of organization. For example, chameleons, turtles, and sloths are endowed with additional adaptations to their living conditions.
Conclusion
According to the theory proposed by A. N. Severtsov, the main factor for increasing the organization of living organisms is private adaptations, which can be accompanied by simplification, that is, degeneration. Thanks to the same arogenesis, various “superstructures” may appear, which give the species the opportunity to survive and develop in private conditions. Biological regression and progress are the main methods of biological development that allow a particular order or genus to survive, develop, improve, or lead to its complete death and extinction.