DIGESTION IN FLAT WORMS

Protozoa – the causative agents of human diseases

Among the simplest organisms, many are dangerous to humans. Dysentery amoeba cause intestinal disorders, trypanosomes cause sleeping sickness, malarial plasmodium cause malaria.

Epidemics of some of these diseases bring a lot of trouble to mankind. In past centuries, and even today in a number of countries, the problem of combating these serious diseases has arisen. The fact is that these diseases can be transmitted both from person to person, and from animal carrier to person.

Diseases that are transmitted to humans by animals are called natural focal. They have existed and have always existed in nature. Infectious diseases transmitted from person to person are called anthroponoses (anthropo – man). Examples of such diseases are smallpox, AIDS, influenza.

A natural focal disease is a complex system consisting of a pathogen, a host, and a vector. These diseases include malaria, plague, tick-borne encephalitis.

Anthroponoses can be defeated. It is enough to cure everyone who is sick or to vaccinate people against a specific disease. This is how smallpox and poliomyelitis were defeated. But the amoebiasis caused by amoebic dysentery has not yet been defeated. Although it would seem that it is quite simple. If you do not drink water from stagnant, untested reservoirs, wash fruits and vegetables well, as well as hands before eating, then the risk of getting sick with amoebic dysentery is minimized. At the same time, you need to know that amoebic dysentery is transmitted only from person to person through direct contact.

How to prevent infectious natural focal diseases? It is not possible to eradicate all tsetse flies that carry sleeping sickness pathogens or all malarial mosquitoes. There is no vaccination against malaria yet. However, there are ways to deal with them. To date, the most effective method of combating malaria and fever vectors, which affect up to 50 million people annually in tropical countries, is DDT, an insecticide synthesized back in the 19th century and actively used to control insects in the 20th century. But DDT decomposes very slowly and accumulates in plants, animals and humans, as well as in the environment. Today, the use of DDT is virtually banned worldwide, but for African countries such as Tanzania, the use of DDT is permitted because this insecticide is the only effective method for controlling malarial mosquitoes.

2. Using the text “Development of the tapeworm” and your own knowledge, describe the possible path of the parasite from a sick animal, through a trade network, to a place in the human body where an adult worm can live up to 15 years.

DEVELOPMENT OF THE BULL CHAIN

The bovine tapeworm often parasitizes in the human intestine. It consists of a head, a short neck and a long ribbon-like body. On the head are four round muscular suckers, with the help of which the parasite is attached to the walls of the intestine. The body of the worm can reach 4-10 m, consists of numerous segments. The growth of the worm and the increase in the number of segments continues throughout life. New segments are formed in the neck area. At first they are very small, but increase towards the posterior end of the body. The worm absorbs food with the entire surface of the body, it has no digestive organs.

Reproduction of bovine tapeworm occurs in the body of the main host – humans. Like most other flatworms, the tapeworm is a hermaphrodite. In each of its segments, except for the youngest ones, there is one ovary and many testes. These segments come off and come out with feces. During the day, the worm produces about 175,000 eggs. Cattle can swallow tapeworm eggs along with grass. In the stomach of the intermediate host, the eggs hatch into microscopic larvae with six hooks.

With their help, the larvae penetrate into the wall of the stomach, enter the bloodstream, spread throughout the body of the animal and penetrate the muscles. Here, the six-hooked larvae grow and turn into a Finn. A finna is a pea-sized vesicle with a tapeworm head and neck inside.

3. Using the content of the text “Parasitic Worms”, answer the following questions.

1) What class of animals does the liver fluke belong to?

2) Who is the final owner of the bull tapeworm?

3) What other, besides those indicated in the text, do flatworms have structural features associated with a parasitic way of life?

parasitic worms

Flatworms are an ancient group of animals. They include both free-living and parasitic forms. Planarians are free-living, while flukes and tapeworms are parasitic. Free-living worms have sensory organs – light-sensitive eyes, organs of balance and touch. Parasitics have no specialized sense organs. However, they have characteristic adaptations for their way of life – hooks, suckers, development with a change of owners.

The most common parasitic worms are the liver fluke and tapeworm. The liver fluke belongs to the class Flukes. It goes through several stages in its development. From an egg that has fallen into the water, a larva with cilia develops. It enters the body of a snail – a small pond snail, which is the intermediate host of the worm. There it transforms into a tailed larva. Tailed larvae attach themselves to plants and turn into cysts. Sheep, goats, and cows swallow fluke cysts and become the final hosts of the parasite, in whose bodies adult worms develop and multiply.

Bull tapeworm belongs to the class Tapeworms. It parasitizes tapeworm in the human intestine, which is its definitive host. The worm consists of many segments filled with eggs, with developing embryos. The eggs enter the external environment, and from there into the organisms of cows grazing in the meadows. The cow is the intermediate host of the bovine tapeworm. In her body, six-hooked larvae develop from eggs, which penetrate the muscles with blood flow, where they turn into Finns. Eating poorly fried meat, a person becomes infected with a bovine tapeworm. In his intestines, a worm develops from a Finn, after a while it grows up to several meters in length and is capable of reproduction.

4. Insert in the text “Reproduction of freshwater hydra” the missing terms from the proposed list, using digital symbols for this. Write down the numbers of the selected answers in the text, and then enter the resulting sequence of numbers (in the text) into the table below.

FRESHWATER HYDRA

The freshwater hydra reproduces sexually and ___________ (A). In the warm season, ___________ (B) is formed on the body of hydras. These outgrowths increase, tentacles and a mouth are formed at the free end of their body, then the sole. In autumn, when unfavorable conditions occur, tubercles appear on the body of the hydra, in which ___________ (B) is formed. On the body of the hydra, both eggs and spermatozoa are formed, therefore the hydra is referred to ___________ (D).

LIST OF TERMS:

1) hermaphrodite 2) dioecious organism 3) kidney 4) zygote
5) asexual 6) dispute 7) stinging cage 8) sex cell

Write down the numbers in response, arranging them in the order corresponding to the letters:

Insert in the text “Digestion in flatworms” the missing terms from the proposed list, using digital symbols for this. Write down the numbers of the selected answers in the text, and then enter the resulting sequence of numbers (in the text) into the table below.

DIGESTION IN FLAT WORMS

Free-living flatworms by way of life, as a rule, ___________ (A). The food that enters their body is digested in the cells of the intestinal wall and in ___________ (B). Undigested food remains are removed through ___________ (B). Some parasitic worms do not have intestines; their food intake occurs through ___________ (D).

LIST OF TERMS:

1) intestinal cavity 2) mouth opening 3) anus 4) stomach
5) body surface 6) throat 7) symbiont 8) predator

Write down the numbers in response, arranging them in the order corresponding to the letters:

6. Insert in the text “Earthworm” the missing terms from the proposed list, using the days of this digital designation. Write down the numbers of the selected answers in the text, and then enter the resulting sequence of numbers (in the text) into the table below.

Earthworm

Earthworms are a suborder of low-bristle worms from the type ________ (A) worms. The number of segments is variable: from 80 to 300. The circulatory system in worms _____________ (B), is quite well developed, the blood is red. Breathing is carried out through the skin rich in sensitive cells, which is covered with protective mucus. The nervous system of earthworms consists of a ventral chain of nerve _________ (B). Earthworms are ___________ (G), each sexually mature individual has a female and male reproductive system. Reproduction occurs through ________________ (D), inside which the eggs are fertilized and develop.

LIST OF TERMS:

1) round

2) ringed

3) node

4) jumper

5) belt

6) open

7) closed

8) hermaphrodite

9) dioecious

Write down the numbers in response, arranging them in the order corresponding to the letters:

7. Insert into the text “Ascaris” the missing terms from the proposed list, using numerical designations for this. Write down the numbers of the selected answers in the text, and then enter the resulting sequence of numbers (in the text) into the table below.

Ascaris

Roundworms are large __________(A) worms, their length can reach 40 centimeters. Most often affect the organs of the gastrointestinal tract, cause ___________ (B). The favorite habitat of adults is the small intestine. Roundworms are bisexual. Roundworms move freely along the ________ (C) tract, therefore they can crawl into the organs of the __________ (D) system, thereby causing suffocation. You can become infected by eating unwashed vegetables or fruits. The constant presence of parasites in the intestine leads to ___________(D) of the intestinal wall.

LIST OF TERMS:

1) ascariasis

2) dysbacteriosis

3) gastrointestinal

4) respiratory

5) inflammation

6) bisexual

7) hermaphrodite

8) round

9) ringed

Write down the numbers in response, arranging them in the order corresponding to the letters:

8. Insert the missing terms from the proposed list into the text “Annelled worms”, using digital designations for this. Write down the numbers of the selected answers in the text, and then enter the resulting sequence of numbers (in the text) into the table below.

RINGED WORMS

Annelids are animals that have a long __________ (A) body. They are like flatworms and roundworms – __________(B) animals with __________(C) body symmetry. Annelids have __________ (D) and more complex nervous system and sensory organs than other worms. Annelids live in the seas, fresh waters, soil.

LIST OF TERMS:

1) two-layer

2) jointed

3) circulatory system

4) double sided

5) non-segmented

6) three-layer

7) radial

8) respiratory system

Write down the numbers in response, arranging them in the order corresponding to the letters:

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