Ecology studies the interactions among organisms and their environment. It does not only make biological connections clearer, but also has great importance for many branches of production, e.g., for agriculture and forestry, as well as human medicine and veterinary medicine. The environment affects every living being. The environment is divided into environmental factors for better analysis of its effect. Light, temperature, water, gases of the air, wind and ground belong to the abiotic factors. All living beings belong to the biotic factors.

Every living being is adapted in certain measure to the environment. Some living beings survive big variations of the abiotic factors well and, therefore, are spread on the whole planet. Other living beings occur only in certain areas of the earth because they can live only under narrow conditions.

7.1 Environmental factors of a butterfly

Temperature as an environmental factor

All living beings need warmth for their metabolism. Every species has a specific temperature optimum. The living being is especially active at the optimum temperature; it reacts fast to excitations, moves, consumes a lot of food, grows and increases. Species adapts to this temperature best of all.

The activity of the ectothermic animals depends more on the environmental temperature, than that of the endothermic animals. The minimum temperature for most ectothermic animals is about 0 °C, the maximum is from 50 °C to 60 °C. At the extreme temperatures the living beings can just still live, but they do not reproduce any more. At less than 0 °C their cytoplasm is destroyed by ice formation; at more than 50 °C the structure of protein is disintegrated. The hypnospores of bacteria and protozoans can survive substantially higher and deeper temperatures in dry state.

The endothermic animals (birds and mammals) are substantially more independent of the environmental temperature. This is possible due to their construction and the ability to regulate their body temperature. Therefore, they can also inhabit cold seas and cold mountains.

Water as an environmental factor

Water is of vital importance for all organisms. They need it as a means of transportation and as a building material.

Water defines the original living space of all living beings. The vaporisation protection on the skin of some organisms was originated during the phyletic evolution. Insects have a chitin layer and reptiles a horny layer by which they can live on the dry land. The humid respiratory organs of the animals living on land lie inside of the body and are thereby protected against dehydration.

Relations between the organisms of the same kind

They are the relations between organisms of the same kind, for example:

• relations between both genders,
• relations between parents and descendants,
• relations inside a group of animals, e.g., the labour division of the bees,
• relations in animal groups for the mutual protection,  e.g. monkeys.

Relations between organisms of different kinds

The neutral behaviour

Many kinds of living being live on the same territory side by side without using each other or damaging. Some bacteria and protozoa are constantly occured in the bowel of vertebrates, which live there on food leftovers, but usually cause no illnesse cause.

Symbiosis

If two kinds of living being live together with mutual use, it is called symbiosis. Certain kinds of bacteria which can split cellulose live constantly in a part of the stomach or in the appendix of herbivores (e.g., cow, horse). They are nourished by the herbivores and increase the food amount for the herbivore, while they release the nutrients enclosed by the cell walls.

Parasitism

If a living being damages a living being of another kind, it is called parasite, and the injured living being is the host. Many kinds of protozoons (bacteria and protozoans), multicellular animals (first of all flat worms (Plathelminthes), threadworm (Nemathelminthes), insects) and the plants (e.g., mushrooms) live parasitic.

Many parasites live on definite hosts. While ectoparasites on the body surface cause host's damage, endoparasites live in his cells, tissues or organs. Some parasites cuase a host's change. The host in whom the parasite becomes ripe is called final host; the hosts who are damaged during the development of parasite are called transport hosts.

Parasites are adapted to the parasitic life-style. In comparison to free-living kinds, the parasites display anatomical changes:

• regression of the sense organs,
• regression of the intestine by endoparasites which take digested materials through the skin,
• formation of organs for fixation and holding on, e.g., suckers,
•  strongly developed gender organs and big progeny.

Parasites damage their hosts not only by rejection of vital nutrients, but first of all by the delivery of toxic materials (toxins).

The host reacts to the penetrated parasites, it forms antybodies against single-cell parasites which destroy the poisons and often parasites. However, antibodies of the host do not conmat multicellular parasites.

The human society fights parasites taking into consideration their way of living. Therefore, the measures of fight are different.

If a host is infected by a certain parasite, this must be fought by specific means, so that the host's organism is helped and the spreading of the parasites is decreased.

Example: Certain drugs help against tuberculosis bacteria, other against tapeworm.

The protective inoculations and remedial vaccinations are carried out as measures to the fight against microorganisms.

If parasites use transport hosts, the contact of humans or farm animals and transport hosts must be avoided.

Examples: in order to fight plasmodium, its transport hosts –anopheles, must be destroyed.

Cows serve as a transport host for cattle tapeworm. Larvae of this tapeworm living in beef are destroyed by long cooking of meat.

If the eggs of bowel-inhabiting parasites with the excrement reach outwardly, a new infection must be avoided by cleanness.

Example: If hands, fruit and vegetables are washed thoroughly and the sick people are isolated from the healthy, the possibility of the transference is decreased.

Infection by parasites is due partly to the low knowledge of many people. The knowledge of hygiene is an important indirect measure to the fight against parasites.

Structure and way of living of the cattle tapeworm

The cattle tapeworm belongs to the stem of the Plathelminthes. A mature worm in the bowel of a person or an animal is several metres long; it consists of an only 1 mm head and more than 1000 segments (proglottids). The head owns no senses, no mouth, but only four suckers with whose help it holds on in the inner wall of the bowel. The body surface is covered with cuticula which prevents that the tapeworm is digested by the enzymes of its host. Behind the head new proglottids are formed constantly. The tapeworm is hermaphrodite, in the front proglottis the male cells develop first. They then reach the back proglottids and fertilise the ova which are formed in the female organs. The proglottids full with fertilised eggs are pushed off at the body end.

7.2 Structure of the cattle tapeworm

a – head with suckers (S), b – young proglottid with male organs, c – older proglottid with female organ, GO = gender opening

The eggs get into the ground with the excrement which is used as a fertilizer. They are eaten by domestic animals with the feed. The eggs of the cattle tapeworm can develop only in cattle to larvae (measie) which live in the muscles of the cattle. If a person eats uncooked meal, measie containing in the meat of cattle, the measie develops in the bowel of the human further until the ripe tapeworm.

The meat of cattle and pigs is examined before it is sold. Therefore, it seldom occurs that a tapeworm develops in human.

Relations between many species in a habitat

There are relations not only between two species like parasitism and symbiosis, but in living spaces between lots of species which are dependent on each other. The green plants produce organic materials. The herbivores and carnivores among the animals use the organic materials. As saprophytes organic diminish again to inorganic materials, the autotrophen plants have food again and close the circulation of the carbon compounds.

A biocoenosis

A biocoenosis is understood as a symbiosis of many species living together in a habitat with certain environmental factors. Such a habitat is called biotope. Many species of autotrophen and heterotrophen living beings live in a biocoenosis. Besides neutral organisms living side by side, there are also parasites and symbionts. A biocoenosis is, e.g., the system of a certain wood, steppe, lake, sea.

7.3 Development of the cattle tapeworm

The organisms ineract with the abiotic factors ruling in the biotope and form with them a unity of higher degree, an ecosystem.

In an ecosystem the values of the environmental factors constantly fluctuate around certain averages. This process is called biological balance. An ecosystem is always regulated independently. Its structure is thereby preserved for a long time.

Changes of the ecosystems by the person

Energy and raw materials are taken from the ground, the air, the water, the kingdom of plants and animals as a basis of social production. Large parts of the ecosystems have been changed by the human activity and new ones have occurred (e.g., fields), these biotopes are not fuled by biological balance, they must be constantly influenced by human.

Poor knowledge or irresponsible work led to more or less strong negative influence on the nature. Ground, air and water are poisoned by industry in many places on the earth still today; deserts are partly the result of the human work.  

Parasites in agriculture

There are numerous living beings which damage our cultivated plants or domestic animals as parasites.

The level of these damages is different in the different countries depending on the methods of plant production or cattle breeding, and the climate. This level changes from year to year. The amount of losses caused by diseases, animal pests and weeds in the production of wheat is about 24% of the yield, with rice in India and Indonesia about 57% and with the cultivation of cotton from 30 to 40%.

Parasites which cause big damages in the agriculture are representatives of many systematic groups, first of all many bacteria and protozoans. Plathelminthes are, first of all, the liver flukes of the sheep and cow. Nemathelminthes can be parasites of our domestic animals and pests of different cultivated plants, they damage to roots of plants.

Insects play an especially big role as pests for plants, or as carriers of diseases.

Fungi are also to be found with the useful plants as parasites. Some fungi are on the surface of plants; they have special processes which penetrate into the epidermis cells of the host and take away from these the necessary nutrients. Mildew is a parasite with visible white mycelium on the leaves of the host plants. It can completely destroy the harvest.

Another fungus causes, for example, the disease of coffee plant. The plants wilt because the vessels are closed and thereby the water transportation is prevented.

To fight against different diseases caused by mushrooms is possible by the following measures:

- rise of the robustness by right soil tillage, fertilisation, irrigation or drainage, favourable plant supplies, suitable crop rotation;

- elinimation of infected plants or plant parts to prevent the spreading of the disease;

- cultivation of resistant kinds;

- chemical fight.

Not only parasites decrease harvest, but also weeds. A weed is a plant which can destroy the yield. The decrease in production by weeds happens from the following causes:

Weeds take away water and mineral substances from the ground, therefore the useful plants lack them. As a weed often grows quicker than the tilled plants, it deprives them of the necessary light.

The weeds are hosts and transport hosts for diseases caused by parasites.

The are different methods of fight against weed:

- careful seeds separation from  the weed seeds;

- destruction of weeds by manual labour or ground processing machines;

- chemical fight and destruction by synthetic hormones.

1. Answer the questions using the information from the text:

1. What tasks does ecology have?

2. What are biotic environmental factors?

3. Which living beings are spread on the whole earth?

4. How does a living being behave if the surrounding temperature has optimum values?

5. What is the temperature maximum of an organism caused by?

6. What does the symbiosis mean?

7. What advantages do herbivores get from bacteria living in their digestive canal?

8. What is the name of the symbiosis of many species in a biotope?

9. In which biotopes biological balance don’t rule?

2. Answer the questions about parasites with the help of the text:

1. What eating habits do many mushrooms have?

2. What is an entoparasite?

3. Which living beings are called transport hosts?

4. How can the host be damaged by the parasite?

5. How does the host react against penetrated single-cell parasites?

6. Why are the malaria mosquito fought?

7. What is the most important measure for the protection against the bowel-inhabiting parasites which have no transport host?

8. Which organs are infected by the cattle tapeworm?

9. Which function does the cuticula of the tapeworm have?

10. In what part of the tapeworm are the female gender organs developed?

11. Why is the meat examined before selling?

ECOSYSTEMS

1. Define the concepts biotope, biocoenosis, ecosystem.

2. Describe some of the abiotic environmental factors (temperature variations of the year and the day, average height of the temperature, height and distribution of the rain in the year etc.).

3. Describe biocoenosis.

4. Speak about the interaction between environmental factors.

5. Explain  biological balance using examples.

Example: Relations between green plants, animals, putrefaction bacteria

Example: Relations between the weather, the plant growth, plant-eating insects and insectivorous birds

Use conditional sentences:

• If the weather is optimum during the growth period of certain plants, so grow...

HUMAN CHANGE OF THE NATURE

1. Give an example of irresponsible work of the human and damages it causes.

2. Give an example of useful changing of the nature.

3. Explain the statement that the results of the ecological investigations matter in increasing measure of the human medicine and the veterinary medicine.

SINGLE-CELL PARASITES

1. Give the scientific of diseases, their causes and the systematic group which they belong.

• The cause of the tuberculosis, tuberculosis bacteria, belongs to the bacteria.

the cause of the bacillary dysentery, the amebic dysentery, the sleeping sickness, the malaria

2. What is protective inoculation and remedial vaccination?

3. Describe the cause and course of certain infectious diseases.

PARASITIC WORMS

1. Explain, why the cattle tapeworm is called endoparasite.

2. Describe the development and reproduction of the cattle tapeworm.

FIGHT AGAIST PARASITES

1. The measures of the fight agaist parasites depend on structure, development and way of living of the parasite and their hosts. Give examples. Describe preventive measures and treatment. Speak about:

• fight against the cattle tapeworm
• fight against the plasmodium

2. Answer the questions about parasites in the agriculture and weeds with the help of the text:

1. What does the level of the damage by parasites to useful plants and domestic animals depend on?

2. What host do Nemathelminthes live in?

3. Which groups of living being play an important role as parasites in plants?

4. In what manner do parasitic mushrooms live?

5. Why must weeds be destroyed?

6. What preventive measures are there to fight against weeds?

THE ROLE OF THE ENVIRONMENTAL FACTORS IN THE AGRICULTURE

1. Use the following words in the text:

abiotic, biotic, poison, climate, liver fluke, parasite, mushroom, weed

In order to cultivated plants grow well and develop, there should be some ... factors like light, pH-factor of soil, water count in soil and the air in certain amount in plants. Some factors like the average temperature and the amount of the rain, belong to the concept....

... occur also except animals and bacteria as parasites in plants. Some of them live as... on the leaves. The growth of the useful plants is restrained by... in the fields. Insects can be fought with the help of....

For our domestic animals... factors play an important role: The domestic animals need certain plants as food, but they can be also damaged by parasites, e.g., by Plathelminthes like ...