Biology lesson in 5th grade
Slide 1 Topic: “Single-celled algae”
Subject results:
– form the ability to distinguish algae from other studied ones plants(according to the table);
To develop the ability to determine the habitat;
– form the ability to explain the structural features and vital functions of algae;
– form ability to understand the meaning of biological terms:thallus, algae .
Meta-subject and personal results:
Cognitive UUD
1. Develop the ability to analyze, compare, classify and generalize facts and phenomena, identify the causes and consequences of simple phenomena.
2. Develop the ability to build logical reasoning, including establishing cause-and-effect relationships.
Communicative UUD
Form the ability to independently organize educational interaction when working in a group (pair).
Regulatory UUD
Form the ability to independently discover and formulate a learning problem, determine the purpose of learning activities (formulation of a lesson question).
Form the ability to work according to a plan, check your actions with the goal and, if necessary, correct mistakes independently.
Form the ability to improve independently developed assessment criteria in dialogue with the teacher.
Equipment: tables, text and pictures of the textbook, flashcards, microscope, microscopic specimens of the green alga Spirogyra. technological lesson map, textbook “V.V. Pasechnik "Biology. Bacteria, fungi, plants M.: ed. Bustard, gray "Vertical" Federal State Educational Standard 2014. - 141 p. ". table.
Lesson terms and concepts: chlamydomonas, spirogyra, thallus plants,
Type: A lesson in “discovering” new knowledge;
Target: organizing student activities to study the structural features of unicellular algae, their adaptability to the environment and their role in nature and human life.
Tasks:
Introduce students to algae as representatives of ancient plants;
Build knowledge about their habitat;
Reveal the structural features of the body;
Show the structure of unicellular algae using the example of Chlamydomonas;
Introduce the diversity of unicellular and multicellular algae;
Show the importance of algae in nature and human life;
Continue to develop the ability to use a microscope;
Continue developing the ability to work with a textbook;
Lesson plan:
1. Organizational moment
2. Explanation of new material. Laboratory work.
3. Consolidation
4. Homework
Equipment: flashcards, microscope, microslides of green algae spirogyra.
During the classes:
1. Organizational moment (5 min).
Updating the problem:
Teacher's opening speech: Good afternoon everyone! Hello! GUYS, look out the window and smile at the world around us, look at each other, smile and wish yourself health and turn and smile at our guests.
Now what's your mood? We begin to work with this mood. We have very serious work ahead of us, and I wish everyone success so that by the end of the lesson no one’s mood will deteriorate. Successful work happens only to attentive people.
Slide 2 Sergey: I have an aquarium like this at home and my fish in the aquarium ate all the algae - both Vallisneria and pondweed.
Slide 3 Slide Biologist: You're wrong, Vallisneria and pondweed are flowering plants. But not everything that grows in water is algae.
1. How do Sergei’s views differ from mine? ( You are talking about plants, and Sergei is talking about algae)
And I asked this question not by chance, because the topic of our lesson will really be related to algae. Try to guess what we will be talking about in class, and if it is a biology lesson.( About the structure, adaptability of Chlamadomonas to its habitat, etc.)
Do you have any other ideas about the topic of the lesson?
Slide 4 . TO By the way, - Look at the presented slides,
What is the name of algae? ( green algae chlamydomonas, spirogyra)
How many cells does Chlamydomonas have? (one )
Do all algae consist of one cell like Chlamydomonas? (No )
How are the algae presented on the slides different?
So, what two groups of “Algae” can be identified based on this slide?
Seaweed Slide 5
Unicellular Multicellular
(Chlamydomonas) (Spirogyra)
(Among algae there are unicellular and multicellular forms.) Therefore, today we will discuss only single-celled algae in class. Let's open our notebooks and write down the topic of the lesson. What will it be called?
Slide 6(Single-celled algae)
Guys, today we are working in groups. (1,2,3,4,5 groups)
Now confer in pairs (groups) and propose a plan for studying the topic. It can be in the form of questions, phrases, sentences, not too cumbersome.
Whose group is ready, give a sign.
1. Definition of algae.
2. Algae habitat
3. The structure of algae.
4. Method of feeding algae.
5. The importance of algae in nature and human life
Slide 7 Plan
We came up with a 5-point plan.
You have proven that you are attentive, so remember that the plan is the result that you should get by the end of the lesson, that is, you need to learn to reveal each point of the plan you propose.
Thank you for your ideas and suggestions, and I have a whole basket of ideas for you. Take out the note with the idea and read it out loud. If the idea is accepted, we leave it in the basket, and at the end of the lesson we will discuss whether this idea was implemented.
Today we are learning to highlight the most important information
Today we are learning to write smart cheat sheets
Today we are learning to express our thoughts beautifully.
Today we are learning to catch the teacher's hints
Today we learn to listen to each other
Today we learn to prove convincingly.
Well, now that the topic, plan and objectives of the lesson have been determined, we work according to the plan.
Define the term algae.
(Give examples) Why is this difficult to do?
Slide 8. P I offer help: Select the necessary words from the list and create a definition. (We work in groups)
Living, unicellular, organisms, or, in aquatic environments, multicellular
(Single-celled or multicellular organisms living in an aquatic environment)Slide 9 The word “algae” literally means only that these are plants that live in water, but not all plants in water bodies can be scientifically called algae, such plants as reeds, reeds, cattails, water lilies, egg capsules, small green plates of duckweed and etc., are seed (or flowering) plants.
What kingdoms of living nature do you know? Slide10
What kingdom can algae belong to? (To the plant kingdom)
So we have to prove that algae belong to the plant kingdom?
Consider the habitat
Where can unicellular algae live?
Slide 11. Almost all algae live in water. A few are on stones, wood, sand, bark. Algae inhabit seas, rivers and lakes only at those depths where sunlight penetrates.
Let's write in notebooks: Habitat: in water, in damp places, on rocks and wood.
What's the next item on the plan?
3.Building.
Let's remember what main organelles a plant cell consists of? Let's turn to the poster. (shell, cytoplasm, nucleus, chloroplasts)
Slide 12. A Can you find them in Chlamydomonas? What other organelles are there? Take my hint. Who can help us with this? Well, of course the textbook. Let's turn to the textbook for help, open page 94, first paragraph. (Read)
Who can tell us? So what other organelles does Chlamydomonas have?
Slide13 Chlamydomonas (from Greek “the simplest organism covered with a membrane”). Chlamydomonas has an oval shape and two flagella, thanks to which it moves in water. The outside is covered with a transparent shell, under which there are cytoplasm, a nucleus, a cup-shaped chloroplast and a red “eye”, with the help of which Chlamydomonas distinguishes the light it needs for photosynthesis. The “eye” perceives light - and Chlamydomonas moves towards the illuminated place. It has pulsating vacuoles that remove excess water from the cell.
Slide14 Performing laboratory work:
Laboratory work “My biological research. Studying
structure of algae":
Procedure for performing laboratory work:
1. Consider the appearance of the algae.
2. Draw and label the names of its organ bodies: (nucleus, cell wall, cytoplasm, vacuoles, chromatophore).
Let's consolidate the learned material. I call it an organoid. If this organoid is found both in the plant and in algae, you squat with your arms extended forward; if the organoid is found only in algae, you put your hands on your belt and tilt your torso to the left and right.
Slide 15. physical education minute.
Shell, red sensory eye, nucleus, two flagella, cytoplasm, pulsating vacuoles, chloroplast. Enough. Sit down
We continue to work.
4.Food.
Why is Chlamydomonas green? What does this mean.( there is a chromatophore. chloroplasts) What does this word mean (carrying light). What is contained in the chromatophore ( chlorophyll - a substance that captures light rays)
What role do you think chlorophyll plays in the nutrition of Chlamydomonas? In a word, how are nutrients formed in Chlamydomonas?
Algae consume dissolved minerals, water, carbon dioxide, oxygen and light energy. However, in the dark, many algae begin to feed on ready-made organic substances dissolved in water.
Slide16 Autotrophic - the creation of organic nutrients through the process of photosynthesis.
Heterotrophic – absorption of ready-made nutrient solutions.
You already understand on what basis algae are divided into 2 groups depending on the method of nutrition.
Try to make a diagram in your notebook (according to the way you eat)
Slide17
Now can we say which kingdom algae belong to? Let's compare them to plants. What do plants and algae have in common? Can we call plants autotrophs?
What organs do plants have? What about algae?
Slide The body of multicellular algae does not have true roots, stems and leaves and is called a thallus.
Slide18 Algae - thallus plants"
Since we found out that there are 4 Kingdoms in nature: ( plants, fungi, bacteria, animals), then algae belong to which kingdom? (plants). In turn, plants are divided into 2 subgroups: lower, higher.
Let's make a small cheat sheet in a notebook in the form of a diagram:
Slide 19
Do you think algae affects the environment? We can name the positive and negative effects of algae on the environment. Popov Vova prepared a message about the role of algae in nature and human life.
The lesson is coming to an end. Today we worked with a large amount of material. Let's try to summarize - what of what you studied remained reliably and for a long time in your memory (suitcase), what material requires further comprehension (meat grinder), and what flew by (Fan)
Let's check your knowledge in your suitcases.
I suggest you run this test:
The organelle that reacts to light in Chlamydomonas is: a) chromatophore, b) flagellum, c) ocellus, d) nucleus.
Photosynthesis in algae occurs in a) the chromatophore, b) the light-sensitive eye, c) the leaf.
Algae absorb water and minerals: a) rhizoids, b) leaves, c) roots, d) the whole body.
Algae feed: a) creating organic substances from inorganic ones, b) consuming ready-made organic substances, c) creating inorganic substances from organic ones.
Check the correct answers on the screen), rate:
0 errors - 5, 1 error - 4, 2 errors - 3, 3 errors - 2.
1.-c, 2-a, 3-d, 4-c, 5-a.
Homework:
for those who received a “3” paragraph, answer questions about it;
for those who received "4" paragraph without questions;
For those who received a “5”, come up with a riddle.
Now let's get back to the basket of ideas, -
Which of them were you able to implement in the lesson?
Which ones will we leave for the next lesson? It was difficult? Interesting? Mood?
Which of the acquired knowledge and skills will be useful to you in life today?
Thank you all for your work, lesson is over, goodbye.
Homework: text on p. 94-96.
Algae are inhabitants of water. They live both in fresh water reservoirs and in salt waters of seas and oceans. There are also those that live outside of water, for example, on the bark of trees. Algae are very diverse. Let's start getting acquainted with them with unicellular green algae.
For example, in the summer you had to see the green surface of a pond, or the quiet emerald
backwater of the river. Such bright green water is said to “bloom.” Try scooping up the “blooming” water with your palm. It turns out that it is transparent. Many single-celled green algae floating in the water give it an emerald hue. During the “blooming” of small puddles or ponds, the most common unicellular algae found in the water chlamydomonas. Translated from Greek, the word “chlamydomonas” means “the simplest organism covered with clothing” - a membrane. Chlamydomonas is a single-celled green algae. It is clearly visible only under a microscope. Chlamydomonas moves in water using two flagella located at the anterior, narrower end of the cell. Like all other living organisms, Chlamydomonas breathes oxygen dissolved in water.
On the outside, Chlamydomonas is covered with a transparent membrane, under which there is cytoplasm with a nucleus. There is also a small red “eye” - a red light-sensitive body, a large vacuole filled with cell sap, and two small pulsating vacuoles. Chlorophyll and other coloring substances in Chlamydomonas are found in chromatophore(translated from Greek as “carrying color”). It is green because it contains chlorophyll, which is why the entire cell appears green.
Through the shell, Chlamydomonas absorbs minerals and carbon dioxide from water. In the light in the chromatophore, during the process of photosynthesis, sugar is formed (starch from it) and oxygen is released. But Chlamydomonas can absorb ready-made organic substances dissolved in water from the environment. Therefore, Chlamydomonas, together with other unicellular green algae, is used in wastewater treatment plants. Here the water is purified from harmful impurities.
In summer, under favorable conditions, Chlamydomonas reproduces by division. Before dividing, it stops moving and loses its flagella. 2-4, and sometimes 8 cells are released from the mother cell. These cells in turn divide. This is the asexual method of reproduction of Chlamydomonas.
When unfavorable conditions for life occur (cold temperatures, drying out of the reservoir), gametes (sex cells) appear inside Chlamydomonas. The gametes enter the water and unite in pairs. In this case, a zygote is formed, which is covered with a thick shell and overwinters. As a result of division, four cells are formed - young Chlamydomonas. This is a sexual method of reproduction.
Chlorella- also a unicellular green algae, widely distributed in fresh water bodies and soils. Its cells are small, spherical, clearly visible only with a microscope. The outside of the chlorella cell is covered with a membrane, under which there is cytoplasm with a nucleus, and in the cytoplasm there is a green chromatophore.
Chlorella multiplies very quickly and actively absorbs organic substances from the environment. Therefore, it is used in biological wastewater treatment. On spaceships and submarines, chlorella helps maintain normal air composition. Due to the ability of chlorella to create large amounts of organic matter, it is used for feed.
Algae are inhabitants of water. They live both in fresh water bodies and in salt waters of seas and oceans. Algae are very diverse. Let's start getting acquainted with them with unicellular green algae.
We live in the age of space exploration. The time will soon come when Soviet cosmonauts will rush to distant planets. Space paths are long. Future cosmonauts will have to spend months and years in ships rushing across the expanses of the universe. A person consumes up to 700 liters of oxygen per day and exhales a lot of carbon dioxide. How to be? Scientific research has shown that green algae can provide oxygen to astronauts. In the light, when organic nutrients are formed, they absorb carbon dioxide and release oxygen, continuously replenishing its reserves in the air.
The most useful plant for space travel is likely to be a tiny single-celled algae called chlorella. Why is chlorella more interesting than other green plants for space researchers? Because this algae is capable of multiplying quickly. It contains a large amount of proteins equivalent to the protein of powdered cow's milk.
Chlorella- a single-celled green algae, widely distributed in fresh water bodies, seas and soils. (Its cells are small, spherical, clearly visible only with a microscope. On the outside, the chlorella cell is covered with a membrane. Under the membrane there are cytoplasm and nucleus. Inside the cytoplasm there is a green chromatophore, in which organic substances are formed in the light. Chlorella absorbs carbon dioxide, water and mineral salts the entire surface of the body through the shell.
During the process of photosynthesis, that is, the creation of organic substances in the light, chlorella releases an amount of oxygen that significantly exceeds its mass. At the same time, chlorella absorbs much more solar energy than flowering plants.
Chlorella's ability to produce large amounts of organic matter and release a lot of oxygen allows scientists to suggest that chlorella can be used in spaceship greenhouses as a source of oxygen and food for astronauts. Scientists' research has not yet been completed, but preliminary tests have shown that algae can accompany astronauts on flight to provide them with oxygen and, possibly, nutrition.
Chlorella is just one type of single-celled algae.
You've probably seen the green surface of a pond or the quiet emerald backwater of a river in the summer. Such bright green water is said to “bloom.” Try scooping up the “blooming” water with your palm. It turns out that it is transparent. This multitude of small green balls and plates floating in the water gives it an emerald hue. The smallest green balls and plates are single-celled green algae that live in water. During the “blooming” of small puddles or ponds, a single-celled algae is most often found chlamydomonas. Let's take a look at this little plant.
The algae got its somewhat strange name from the words: chlamys - clothes of the ancient Greeks and monad - the simplest organism. Literally translated, “Chlamydomonas” means: the simplest organism covered with “clothing” - a shell. Chlamydomonas is a unicellular round green algae. It is clearly visible only under a microscope. Chlamydomonas moves quickly in water with the help of two flagella located at the anterior, narrower end of the cell.
Rice. 153. Appearance and reproduction of algae:
1 - chlorella; 2
- chlamydomonas.
On top, Chlamydomonas is covered with a transparent membrane, under which the cytoplasm and nucleus are located. There is also a small red “eye” - a red body, a large vacuole filled with cell sap, and two small pulsating vacuoles. Chlorophyll and other coloring substances in Chlamydomonas are located in the chloroplast - the chromatophore.
Chlamydomonas has a cup-shaped chromatophore. It is colored green by chlorophyll, which is why the entire cell appears green. Translated into Russian, the word “chromatophore” means “color carrier.”
Single-celled Chlamydomonas feeds, like green flowering plants. Chlamydomonas absorbs solutions of mineral salts and carbon dioxide with its entire surface. In the light, an organic substance - starch - is formed in the chromatophore during photosynthesis and oxygen is released. But Chlamydomonas can also absorb ready-made organic substances from the environment.
Like all other living organisms, Chlamydomonas breathes oxygen dissolved in water.
In summer, Chlamydomonas reproduces by simple division. Before dividing, it stops moving and loses flagella, then its nucleus and cytoplasm are divided in half. The new cells in turn divide in half. This is how four, and sometimes eight, mobile small cells appear under the mother’s shell. They are called zoospores.
Zoospores become covered with their membranes and form flagella. Soon they swim out of the ruptured maternal shell into the water, begin to live independently and turn into adult Chlamydomonas.
The reproduction of algae by the formation of zoospores is called asexual reproduction.
When unfavorable conditions occur, the reproduction of Chlamydomonas becomes more difficult. First, Chlamydomonas divides into a large number of small motile cells with flagella. Then small mobile cells of different individuals of Chlamydomonas are connected in pairs. In this case, the cytoplasm and nucleus of one cell merge with the cytoplasm and nucleus of another cell. So from two cells one new one is formed, which is covered with a thick, dense membrane. In this form the body overwinters. In the spring, several young chlamydomonas are formed from a cell with a thick shell. They leave the shell of the mother cell, grow and soon become adults.
Algae are characterized by a wide variety of structures
nia. They are unicellular, colonial and multicellular.
In the conditions of Belarus, such autotrophic and autoheterotrophic unicellular algae as chlorella, green euglena, etc. are widespread.
Chlorella is often found in fresh water bodies, on damp soil, and tree bark. Chlorella is a spherical, single-celled organism. Its cell is covered with a dense, smooth membrane. The cytoplasm contains the nucleus, cup-shaped chloroplast and other organelles.
Chlorella reproduces asexually, producing many spores. The spores, while still inside the mother cell, are covered with their own membrane and then come out. The spore subsequently grows into an adult.
Green Euglena lives in small fresh bodies of water with stagnant water - puddles, lakes, swamps, and also on moist soil. In the summer, you can watch how the water in a small pond or puddle turns green - “blooms”. The reason for this “blooming” may be the massive development of euglena. Under a microscope, in a drop of water taken from such a reservoir, you can examine its structure.
Structure of green euglena: 1 - peephole; 2 - chloroplast; 3 - core; 4 - reserve nutrients; 5 - contractile vacuole; 6 - flagellum.
The body of green euglena, about 0.05 mm long, has an elongated, streamlined shape, well adapted to movement in water. The outer layer of cytoplasm in euglena is compacted and called the pellicle, which gives the cell its shape. There is a depression at the front end of the euglena's body. It is the exit channel of the contractile vacuole, and from the opening of the recess it emerges flagellum- organelle of movement. Constantly rotating its flagellum, the euglena seems to be screwed into the water and, due to this, swims forward. The cytoplasm of euglena contains a nucleus, a bright red light-sensitive eye and about 20 chloroplasts containing chlorophyll.
Nutrition. A special feature of euglena is the ability to change the nature of nutrition and metabolism depending on environmental conditions. In the light, it is characterized by an autotrophic type of nutrition. Euglenas are always found in the illuminated part of the reservoir, where conditions are more favorable for photosynthesis. Euglena helps to find illuminated places photosensitive eye, located at the anterior end of the body.
If euglena is placed in the dark for a long time, it loses chlorophyll and becomes colorless. In the absence of chlorophyll, photosynthesis stops, and euglena begins to assimilate ready-made organic substances, i.e. transitions from autotrophic to heterotrophic (saprotrophic) mode of nutrition. That is why in waters enriched with organic substances, euglena develops in mass quantities.
Heterotrophic nutrition in euglena is carried out by absorbing organic substances over the entire surface of the body.
Often, developing in polluted water bodies where there is a large amount of dissolved organic matter, euglena combines both types of nutrition - both autotrophic and heterotrophic. Euglena's ability to change its feeding pattern provides the ability to survive in various living conditions. Thus, Euglena green is an autoheterotrophic protist.
Distinctive feature autoheterotrophic protists is their ability to feed in two ways: in the light - like plants, and in the dark - like animals. This means that in the light they carry out the process of photosynthesis and create organic substances. When there is insufficient light for photosynthesis and when there is an abundance of organic substances in the water, they assimilate ready-made organic substances that are formed in the reservoir during the breakdown of dead parts of living organisms.
Breathing and elimination in green euglena the same happens as in other freshwater protists.
The contractile vacuole, in which excess water with dissolved metabolic products accumulates, releases its contents when contracted. This process occurs rhythmically every 20-30 s.
Reproduction. Asexual reproduction of euglena begins with the division of the nucleus, chloroplasts, light-sensitive eye and the formation of a second flagellum. Then, at the anterior end of the cell, a separation gap appears between the flagella, which gradually increases. At the end of longitudinal division, the daughter cells, connected to each other by their posterior ends, diverge. Under favorable conditions, the process of cell division continues for 2-4 hours.
Sexual reproduction in Euglena has not been scientifically established.
Euglena, like amoeba, tolerates unfavorable environmental conditions in the state of cysts.
Chlamydomonas often found in bodies of water polluted with organic matter that are similar to euglena. Last year you became acquainted with its structure, nutrition, and reproduction. To this should be added one more very important feature of Chlamydomonas. It turns out that, along with the autotrophic method of nutrition, it is able to absorb organic substances dissolved in water through the shell and thus participate in the purification of polluted water.
Chlamydomonas reproduces asexually and sexually. In favorable conditions chlamydomonas multiplies in an asexual way. In this case, Chlamydomonas loses its flagella and stops moving. Its nucleus divides twice: four daughter nuclei are formed. The protoplast is then divided into four parts. Thus, four and sometimes eight zoospores are formed inside the mother cell. Each of them is covered with a shell, and two flagella are formed at the anterior end. The shell of the mother cell ruptures, and the zoospores develop into daughter chlamydomonas, which begin to exist independently. They grow quickly and are capable of a new division within a day.
In adverse conditions(for example, when a reservoir dries out), Chlamydomonas occurs sexual reproduction. In this case, its contents are divided into 6, 32, 64 small movable
sex cells - gametes. They swim into the water and merge with the gametes of another individual. This is how fertilization occurs, as a result of which one cell is formed - a zygote. It has no flagella, is covered with a thick shell and is resistant to adverse conditions. When favorable conditions occur, several chlamydomonas develop from the zygote.
Diatoms. Diatoms are found in seas and fresh waters of all climatic zones. Under a microscope you can see that the shape of these single-celled organisms can be very diverse. What all diatoms have in common is the presence of a durable silica shell. This shell consists of two halves, which fit one to the other, like a box with a lid. The yellow-brown color of diatoms is given by pigments that mask chlorophyll. Diatoms reproduce sexually and asexually through cell division. As a result of an increase in the volume of cytoplasm, the halves of the shell diverge, and the nucleus and cytoplasm divide. Each daughter cell re-forms the missing half of the shell.
In fresh waters, diatoms are mainly found at the bottom of bodies of water. Marine diatoms live suspended in water. A drop of fat contained in an algae cell allows it to easily maintain this state. Diatoms provide an important food supply for shallow-dwelling animals such as shellfish. One square centimeter of tidal land often contains over a million diatoms that form a brown coating. Shellfish “graze” on diatoms, and other animals, such as herring gulls and eiders, feed on them.
Diatoms are at the very beginning of the food chain: diatoms → shellfish → birds.
Almost non-degradable shells dia-
Diatoms of marine and fresh water bodies: 1 - tabellaria; 2- pinnularia; 3 - tabellaria; 4 - rhizo-salting; 5 - fragilaria; 6 - stephanodiscus; 7 - navicula; 8 - asterionella; 9 - cyclotella.
tom algae formed thick layers of sedimentary rock over geological epochs diatomite Today these deposits are being mined. Due to the fine structure and hardness of the shells, diatomite is used as a grinding and polishing material, as well as for making filters. In pharmacies, silica is offered as a skin, hair and nail care product. The structure of diatom shells is so fine and regular that they can be used to test the quality of microscopes.
Colonial algae. Volvox. In small freshwater bodies of water (ponds, lakes) there are floating green balls with a diameter of 1-2 mm. This is a Volvox. When examined under a microscope, it can be seen that it is formed by many individual cells located along the periphery of the ball in one layer. Their number ranges from 500 to 60,000.
Volvox colony with daughter colonies inside the mother colony.
Cells are individual organisms united in a colony. Volvox cells are similar to Chlamydomonas. They have two flagella. The coordinated work of the flagella ensures the rotational (top-shaped) movement of the colony (hence the name of this organism: “volvox” means “top”).
The bulk of the colony consists of a semi-liquid gelatinous substance, which was formed as a result of mucilage of the cell walls. The outer layer of the gelatinous substance is denser, which gives the entire colony a certain shape.
In a Volvox colony, individuals are not completely isolated from one another. They are fused by their side walls and connected to each other by thin cytoplasmic bridges.
Volvox is characterized by differentiation, or specialization, of cells in the colony. Some of them are vegetative, incapable of reproduction, others are cells of asexual and sexual reproduction. In a Volvox colony, there are few reproduction cells - from 4 to 10. In the summer, these cells divide repeatedly and form several new daughter colonies inside the mother colony. When the size of the daughter colonies increases so much that they cannot fit inside the mother colony, the latter ruptures and dies, and the daughter colonies go outside.
During sexual reproduction, gametes develop in specialized cells of the colony, the fusion of which results in the formation of a zygote. After a period of rest, a new colony develops from the zygote after a series of successive divisions.
The presence of organisms such as Volvox with specialized cells that perform different functions suggests that the development of multicellular organisms from unicellular organisms could proceed through colonial forms.
Algae include unicellular, colonial and multicellular organisms capable of photosynthesis. The ability to photosynthesis is ensured by the presence of chloroplasts in their cells. Algae come in different shapes and sizes. They live primarily in water and inhabit those water depths where light penetrates. Euglena green and Chlamydomonas are typical representatives of autoheterotrophic protists (algae).
Multicellular algae are widespread in freshwater and marine reservoirs. The body of multicellular algae is called thallus. From The distinctive feature of the thallus is the similarity of cells and the absence of tissues and organs. All cells of the thallus are structured almost identically, and all parts of the body perform the same functions. In the body of an algae, substances move from cell to cell, and this happens very slowly.
The cells of the thallus can divide in one direction, forming filaments, or in two directions, forming plates. Among algae there are species not only of microscopically small sizes, but also those that reach a length of over 100 m (for example, the brown alga Macrocystis pyriformis reaches a length of 160 m).
Algae play an important role in nature, participating in the formation of organic matter and oxygen.
Multicellular algae are filamentous, lamellar, and bushy. They usually lead an attached lifestyle.
Ulotrix. This algae lives mainly in fresh water, less often in sea water. It attaches to underwater objects, forming bright green bushes up to 10 cm high.
Ulotrix filaments consist of a single row of cylindrical cells with thick cellulose membranes. Ulotrix is characterized by chloroplasts in the form of a plate forming an open belt.
Asexual reproduction is carried out by breaking the filament into short sections, each of which develops into a new filament, or by 4-flagellate zoospores. They leave the mother cell, lose their flagella, attach sideways to the substrate and grow into a new filament. During sexual reproduction
Ulotrix: 1 - appearance; 2 - fragment of a thread with zoospores and gametes; 3 - zoospore; 4, 5 - gametes and their copulation.
The gametes fuse to form a zygote. The zygote first floats, then settles to the bottom, loses its flagella, develops a dense shell and a mucous stalk, with which it attaches to the substrate. After a period of rest, the nucleus divides and the zygote germinates as zoospores.
Change of generations in algae. In some algae species, both gametes and spores can develop in the cells of one individual. At high temperatures, for example, algae produce spores, and at low temperatures, gametes.
In other algae, individuals of one species can be of two varieties. Some of them produce spores. They are called sporophytes, and they have a double set of chromosomes in the cells of their body. Others produce gametes. They are called gametophytes and have a single set of chromosomes in their cells.
The gametophyte may be similar in appearance to the sporophyte, or may differ in shape and size. In Ulotrix, the filamentous multicellular gametophyte (the generation that forms gametes) is replaced by a unicellular sporophyte - the generation that is the result of the sexual process and forms spores.
In kelp, on the contrary, the gametophyte is microscopic, and the sporophyte is a ribbon up to 15 m long.
Spirogyra. Spirogyra is often found in stagnant and slow-flowing reservoirs. It is a thin thread consisting of cylindrical, mononuclear cells arranged in one row with a clearly visible cell membrane. The outside of the threads is covered with a thick layer of mucus, so it feels muddy and slimy to the touch. Together with other filamentous green algae, spirogyra forms large masses of bright green mud.
A characteristic feature of spirogyra is that the chloroplast has the appearance of a spirally twisted ribbon located in the cytoplasm along the cell wall. Most of each cell is occupied by a vacuole containing cell sap. In the center of the cell there is a nucleus enclosed in a cytoplasmic
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Reproduction of ulotrix and alternation of generations: a - daughter (new) algae; b - algae that form gametes (gametophytes): 1 - zoospore germination; 2 - gametes; 3 - gamete fusion; 4 - zygote (sporophyte); 5 - germination of the zygote with four-flagellate zoospores.
Chinese pouch connected by cords to the wall cytoplasm.
Asexual reproduction in Spirogyra is carried out by breaking the thread into separate short sections. Reproduction
Spirogyra: A - part of the thread; b - sexual process (conjugation): 1 - chloroplast; 2 - core; 3 - zygote.
there are no disputes. Spirogyra is also characterized by sexual reproduction.
During sexual reproduction, two filaments are usually located side by side. In their cells, protrusions of walls appear that grow towards each other. At the point of their contact, the walls dissolve, and a through channel is formed between the cells of the two threads. Through this channel, the contents of the cell of one thread move into the cell of the other thread and merge with its contents. As a result, a zygote is formed. This type of sexual process is called conjugation. The resulting zygotes with a thick shell germinate after a period of dormancy. This is preceded by double division of the nucleus: out of the four resulting nuclei, three die, 
Seaweed: 1 - ulva; 2 - fucus.
and one remains the nucleus of a single seedling, which emerges at the site of rupture of the zygote shell and develops into an adult algae.
Ulva. Ulva is known as “sea salad”, as the population of many coastal countries eats it. In the shallow waters of the Black and Sea of Japan, ulva is one of the most abundant algae. It is easily recognized by its wide two-layer lamellar thallus of bright green color.
The thallus of the ulva consists of almost the same type of cells. Only at the base are they larger and equipped with shoots, with the help of which the plants are attached to the substrate. Ulva reproduces asexually (by four-flagellate zoospores) and sexually. It does not have specialized reproductive organs; zoospores and gametes are formed in ordinary cells.
Kelp. The seas are inhabited by algae that have a yellow-brown thallus color. These are the so-called brown algae. The color of their thallus is due to the high content of special pigments in the cells. The body of brown algae has the form of threads or plates. A typical representative of this group of algae is kelp, which is known as sea kale. It has a lamellar thallus up to 10 - 15 m long. Laminaria is attached to the substrate by outgrowths of the thallus - rhizoids. Reproduces by zoospores and sexually.
Laminaria is used as food and feeds livestock as a food additive containing many chemical elements and large amounts of iodine. Laminaria is also used to obtain iodine and carbohydrates used in the food, medical and microbiological industries.
In shallow waters, dense thickets form fucus. Its thallus is more dissected than that of kelp. In the upper part of the thallus there are special air bubbles, due to which the body of the fucus is held in an upright position.
Adaptations of algae to living conditions. For organisms living in oceans, seas, rivers and other bodies of water, water is their habitat. Conditions of this environment
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Seaweed: 1 - kelp; 2 - allaria; 3 - undaria; 4 - phyllophora; 5 - gelidium; 6 - ahnfeltsion.
noticeably different from terrestrial conditions. Reservoirs are characterized by a gradual weakening of illumination as they dive deeper, fluctuations in temperature and salinity, and low oxygen content in water - 30-35 times less than in air. In addition, water movement poses a great danger to seaweed, especially in the coastal (tidal) zone. Here algae are exposed to such powerful factors as surf and wave impacts, ebb and flow, etc.
The survival of algae in such harsh conditions of the aquatic environment is possible due to a number of structural features.
1. With a lack of moisture, the cell membranes become significantly thicker and become saturated with inorganic and organic substances, which protect the body from drying out during low tide.
2. The seaweed thallus is firmly attached to the ground, so in the event of surf and
When hit by waves, they are relatively rarely lifted off the ground.
3. Deep-sea algae contain larger chloroplasts with a high content of chlorophyll and other photosynthetic pigments.
4. Some algae have special bubbles filled with air. They, like floats, hold the thallus near the surface of the water, where it is possible to capture the maximum amount of light for photosynthesis.
5. The release of spores and gametes in seaweed coincides with the tide. The development of the zygote occurs immediately after fertilization, which prevents it from being carried away into the ocean.
The meaning of algae. The widespread distribution of algae determines their great importance in the biosphere and human economic activity. Thanks to their ability to photosynthesize, they create a huge amount of organic substances in water bodies that are used by aquatic animals. In other words, algae are feeders for aquatic animals.
Algae are a source of oxygen. By absorbing carbon dioxide from the water, algae saturate it with oxygen, necessary for all living organisms.
Many algae (Euglena, Chlamydomonas, etc.) are active cleaners of polluted water bodies, including economic and domestic wastewater from city sewers.
In the geological past of the Earth, algae played an important role in the formation of rocks and chalk, limestone, reefs, special varieties of coal, and were the ancestors of plants that colonized the land.
Algae are extremely widely used in various sectors of human economic activity, including the food, pharmaceutical and perfume industries. They are cultivated in large quantities in open-air installations to obtain proteins and vitamins.
Of great importance in nature and human economic activity is chlorella. Rapid reproduction and high intensity of photosynthesis (about 3-5 times higher than in terrestrial plants) lead to the fact that the mass of chlorella increases more than 10 times per day. At the same time, proteins (up to 50% of the dry mass of the cell), sugars, fats, vitamins, etc. accumulate in the cells.
The ability of chlorella to intensively absorb carbon dioxide and release oxygen during photosynthesis makes it possible to use it to restore air in confined spaces of spaceships and submarines.
Algae serve as raw materials for the production of valuable organic substances: alcohols, varnish, organic acids, iodine. Special substances are also obtained from algae, on the basis of which glue is made, which has an adhesive strength 14 times greater than that of starch. These substances are used in the textile and paper industries to add thickness and gloss to paper.
obtained from red algae agar-agar. It is used as a solid medium on which fungi and bacteria are grown with the addition of certain nutrients. Agar-agar is used in large quantities in the food industry in the production of marmalade, marshmallows, ice cream and other products.
Humans use algae for food. Thus, on the Hawaiian Islands, out of 115 types of algae available there, the local population eats about 60. The most famous as a therapeutic and preventive remedy is “seaweed” (some types of brown algae, kelp and red porphyry). It is used against gastrointestinal disorders, thyroid disease, rickets and other diseases. In agriculture, algae are used as organic fertilizers for some plants and as a feed additive in the diets of domestic animals.
Multicellular algae are widespread in freshwater and marine reservoirs. The body of multicellular algae is called a thallus. A distinctive feature of the thallus is the similarity of cell structure and the absence of tissues and organs. All cells of the thallus are structured almost identically, and all parts of the body perform the same functions. Algae have a number of characteristic features for living in water. Algae play an important role in the biosphere and human economic activity.
Algae are found ubiquitously in all habitable habitats. In freshwater bodies of water, algae most often have microscopic sizes, but in the seas there are algae that reach tens of meters in length.
Algae live in reservoirs of any type, but some have adapted to life on land (in the soil and on its surface, on stones and rocks, tree trunks, etc.). Some of them move freely (actively or passively) in the water column, while others lead an attached lifestyle.
Algae are a taxonomically diverse group of organisms that arose and evolved independently of each other. Algae are photosynthetic, oxygen-producing organisms that live primarily in water. The body of algae is represented by a thallus, or thallus, and is not divided into multicellular vegetative organs. Algae are characterized by single-celled reproductive organs (sporation and sexual reproduction). Currently, this group unites approximately 35^40 thousand species.
Based on their body structure, algae are divided into unicellular, colonial and multicellular. The cells of many algae are similar in structure to plant ones, that is, they have a cell wall, a vacuole with cell sap and chloroplasts, which in algae are called chromatophores. Chromatophores contain pigment systems, which include chlorophylls and carotenoids. Combinations of these pigments determine the color of algal thalli. Some algae have lost the ability to photosynthesize and completely switched to a heterotrophic type of nutrition.
Reproduction in algae can occur in three ways: vegetative (cell division in half, fragments of colonies and filaments, specialized structures), asexual (motile zoospores and immobile aplanospores) and sexually with the participation of gametes. The sexual process in algae is of three types: isogamy, in which the fusion of motile gametes of the same size and shape occurs; heterogamy, in which motile gametes that have the same shape but differ in size merge; oogamy, when a stationary large female gamete (egg) fuses with a small, motile sperm. A separate type of sexual process is conjugation. During conjugation, the protoplasts of two haploid vegetative cells merge and a diploid zygote is formed.
The structure and activity of unicellular algae
can be considered using the example of Chlamydomonas and Chlorella.
Chlamydomonas is a green algae that lives in puddles and other shallow bodies of water. The cell shape of this algae resembles a drop. The outside of the Chlamydomonas cell is covered with a cell wall consisting of pectin. The algae moves in water using two identical flagella located at the front end of the cell. Most of the cell is occupied by a cup-shaped chromatophore. Closer to the front end there is a red eye that perceives light. In the chromatophore, the process of photosynthesis occurs and a reserve polysaccharide, starch, is deposited. The cytoplasm of the cell contains a nucleus and two contractile vacuoles. Chlamydomonas does not have a vacuole with cell sap. Reproduction in Chlamydomonas is asexual and sexual. Asexual reproduction is carried out using zoospores, which are formed inside the mother cell. Most often, 2-4-8 biflagellate zoospores are formed, each of which, after entering the water, grows to the size of an adult individual. During sexual reproduction, biflagellate gametes are formed under the membrane of the mother cell, which fuse in pairs and form a zygote. The zygote becomes covered with a thick shell and overwinters. In the spring, the nucleus in it divides meiotically, and as a result, four young haploid chlamydomonas are formed. Thus, most of the life cycle of Chlamydomonas occurs in the haploid stage; only the zygote is diploid.
The single-celled green alga Chlorella is found in fresh and salt water bodies, as well as in the soil and on its surface. Its cell is spherical in shape and covered with a dense cellulose membrane. The cytoplasm contains a nucleus and a large cup-shaped chromatophore.
Chlorella reproduces only asexually using round, immobile aplanospores. Chlorella is a convenient object for scientific research; with its help, many processes occurring in photosynthetic cells are actively studied. It was used on spaceships for air regeneration and disposal of organic residues in closed life support systems.
Representatives of filamentous algae are Ulotrix and Spirogyra.
The filamentous green algae Ulotrix lives mainly in fresh water bodies and forms a green coating on underwater objects. The ulothrix filament is attached to the substrate using one colorless basal cell (rhizoid). Ulotrix threads do not branch and consist of short identical cells. In the cytoplasm of the cell there is a nucleus and a chromatophore in the form of an open ring. Most of the cell is occupied by a vacuole with cell sap. Ulotrix reproduces vegetatively, asexually and sexually. Four-flagellate zoospores form inside ulothrix cells, enter the water, swim, then attach to underwater objects and begin to divide, forming new filaments. As a result of the first division, two cells of different quality are formed: one colorless (rhizoid), the other green. When the latter divides, the thread of the algae's body grows. During sexual reproduction, biflagellate gametes are formed in cells. The sexual process is isogamous. Having left the mother cell, the gametes fuse in water, forming a four-flagellate zygote, which, after swimming for a certain time, becomes covered with a shell. After a period of rest in the zygote, as a result of meiotic division, 4 haploid zoospores are formed, which, after entering the water, germinate into new filaments. Thus, ulothrix spends most of its life cycle in a haploid state; only its zygote is diploid.
Another widespread green filamentous algae, spirogyra, forms accumulations of green mud in fresh water bodies. Its threads do not branch and consist of large cylindrical cells covered with a cellulose membrane and mucus. In the center of the cell there is a large vacuole with cell sap, in which the nucleus is suspended on cytoplasmic threads. The chromatophore is spirally twisted. One cell can have several chromatophores. Spirogyra reproduces vegetatively (when the filaments break) and sexually.
The sexual process in Spirogyra proceeds according to the type of conjugation. In this case, the contents of the vegetative cells of two adjacent filaments merge. The resulting diploid zygote is coated with membranes and becomes a hibernating stage. In the spring, the nucleus undergoes meiotic division, three haploid nuclei die off, and only one new haploid spirogyra filament grows.
Algae that live in the seas can be unicellular, colonial and multicellular. The largest thalli are brown, red and green algae. Brown algae are multicellular organisms with a yellow-brown color, which is due to the presence of a large number of yellow and brown pigments. Brown algae form the densest thickets to a depth of 15 m, although they can go to a depth of 40-100 m. In the northern and temperate latitudes, one of the most common brown algae grows - kelp, or seaweed, the thallus of which can reach a length of 20 m. Its thallus contains a lot of the amino acid methionine, iodine, carbohydrates, minerals and vitamins, the content of which can exceed many vegetables and forage grasses. In the life cycle of kelp there is an alternation of asexual and sexual generations. This algae is cultivated in the northern seas of Russia and the countries of Southeast Asia.
Red algae, or scarlet algae, mainly live in the seas. They are called so because of the color of the thallus, which varies depending on the ratio of pigments from dark crimson, pink to bluish-green or yellow. The presence of red pigment allows red algae to live at great depths (up to 200 m). These are the deepest sea algae. Their multicellular thalli look like beautiful, complexly dissected plates, sometimes bushes resembling corals, but some representatives can consist of a single cell or form colonies. In addition to cellulose, the cell wall of red algae contains agar. Many scarlet mushrooms are edible.
The importance of algae in nature and agriculture is diverse. Algae are capable of synthesizing organic substances from inorganic ones through the process of photosynthesis. In aquatic ecosystems, they most often play the role of producers, that is, they perform the same function as green plants on land. This is the initial link in the food chain.
During photosynthesis they release large amounts of oxygen. Oxygen dissolves in water and is used for respiration by other organisms.
Algae thickets serve as a habitat, shelter and breeding place for many animals, that is, algae form a variety of aquatic biotopes.
When favorable external conditions occur, some algae are capable of multiplying en masse and causing water blooms. Green bloom of water in ditches, puddles and pits is most often caused by the proliferation of euglena algae. Red tides, a sea bloom caused by a number of microscopic single-celled algae (hence the name Red Sea), cause great damage to fisheries. The algae that cause red tides release substances that are toxic to animals and humans.
Soil algae participate in the formation of the soil structure, partially ensure its fertility, saturate the soil with oxygen, and take part in the formation of a number of rocks and sedimentary rocks.
Algae are widely consumed as food (species of the genus porphyry, kelp). A number of species are successfully cultivated.
Red algae is used to produce agar. It has gelling properties and is used to make jelly, marshmallows, souffles, a number of sweets and other products, and in microbiology to prepare media on which microorganisms are grown.
Brown algae is the only source of alginates - alginic acid compounds that are used in the food industry.
A number of algae (kelp, fucus, ascophyllum) are used to feed livestock and produce fertilizers.
Algae are used in medicine to treat a number of diseases. In recent years, preparations from algae have been used to remove radionuclides.
Some algae are used as indicator organisms to determine the degree of pollution of water bodies. They are also used for wastewater treatment.
Many algae serve as good model objects for scientific research.
Choose one correct answer.
1. Algae does not have
2) leaves
4) no stem, no leaves, no roots
2. Chromatophore is
1) algae cell membrane
2) algae chloroplast
3) algae reproductive organ
4) leaf blade of brown algae
3. Algae multiply
1) vegetatively
2) zoospores
3) sexually
4) all of the above methods
4. Sexual reproduction was not found in
1) Spirogyra 3) Chlamydomonas
2) chlorella 4) kelp
5. When Chlamydomonas reproduces asexually, it forms
1) one zoospore
2) six zoospores
3) eight zoospores
4) an indefinite large number of zoospores
6. Chlamydomonas reproduces sexually
1) in unfavorable conditions
2) in favorable conditions
3) constantly, regardless of external conditions
4) only in laboratory conditions
7. The sexual process is called conjugation
1) Chlamydomonas 3) Chlorella
2) kelp 4) spirogyra
8. Multicellular algae is
1) Chlamydomonas 3) Spirogyra
2) chlorella 4) pinnularia
9. A single-celled algae is
1) kelp 3) chlamydomonas
2) fucus 4) spirogyra
10. Does not apply to filamentous algae
1) ulotrix 3) cladophora
2) kelp 4) spirogyra
11. Chlorophyll in spirogyra cells is located in
1) numerous plastids
2) spherical chromatophore
3) ribbon chromatophore
4) cytoplasm in dissolved form
12. A chromatophore in the form of an open ring has
1) Chlamydomonas 3) Chlorella
2) spirogyra 4) ulotrix
13. Algae rhizoids serve for
1) breathing
2) vegetative propagation
3) attachment to the substrate
4) photosynthesis
14. The department of brown algae includes
1) chlamydomonas
2) kelp
3) chlorella
4) spirogyra
15. According to the type of nutrition, algae, as a rule, belong to
16. Filamentous algae include
| 1) desmococcus | 4) spirogyra |
| 2) chlamydomonas | 5) ulotrix |
| 3) chlorella | 6) cladophora |
| 17. Multicellular green algae is | |
| 1) chlamydomonas | 4) spirogyra |
| 2) chlorella | 5) cladophora |
| 3) ulotriX | 6) kelp |
| 18. Algae cells may contain the following pigments | |
| 1) hemoglobin | 4) carotene |
| 2) hemocyanin | 5) myoglobin |
| 3) chlorophyll | 6) bilirubin |
| 19. Parts of the thallus can be divided | |
| 1) chlamydomonas | 4) spirogyra |
| 2) chlorella | 5) ulotrix |
| 3) pinnularia | 6) cladophora |
| 20. Chlorophyll contains | |
| 1) kelp | 4) chlorella |
| 2) fucus | 5) ahnfeltsion |
| 3) ulotrix | 6) spirogyra |
| 21. Match the name of the algae and the type | |
| which it belongs to. | |
| Name of algae | Type of algae |
| 1) desmococcus | A) red algae |
| 2) cladophora | B) green algae |
| 3) kelp | B) brown algae |
| 4) fucus | |
| 5) Cystoseira | |
| 6) porphyry | |