Methodical development of a lesson on ecology "laws and consequences of food relations". Lesson topic: Laws of competitive relations in nature

mutually beneficial
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Target: to study the laws and consequences of food relations.

Tasks: emphasize the universality, diversity and extraordinary role of food relations in nature. Show that it is food connections that unite all living organisms into a single system and are also one of the critical factors natural selection.

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Lesson topic: LAWS AND CONSEQUENCES OF FOOD RELATIONSHIPS

Target : to study the laws and consequences of food relations.

Tasks: emphasize the universality, diversity and extraordinary role of food relations in nature. Show that it is food ties that unite all living organisms in single system and are also one of the most important factors of natural selection.

Equipment: graphs showing fluctuations in numbers in the relationship "predator - prey"; herbarium samples of insectivorous plants; wet preparations (tapeworms, liver fluke, leeches); insect collections ( ladybug, ant, gadfly, horsefly); images of herbivorous rodents, mammals (eagle, tiger, cow, zebra, baleen whales).

I. Organizational moment.

P. Testing knowledge. Test control.

1. Light-loving herbs growing under spruce are typical
representatives of the following type of interactions:

a) neutralism;

b) amensalism;

c) commensalism;

d) protocooperation.

2. Type of relationship of the following representatives of the stomach
of the world can be classified as "freeloading":

a) hermit crab and sea anemone; b) a crocodile and an ox bird;

c) shark and sticky fish;

d) wolf and roe deer.

3. An animal that attacks another animal, but
eats only part of its substance, rarely causing death, relatively
goes to number:

a) predators

b) carnivores;

d) omnivores.

4. Coprophagia occurs:
a) in hares;

b) in hippos;

c) elephants;

d) tigers.
5. Allelopathy is an interaction with the help of biologically active substances, characteristic of the following organisms:

a) plants

b) bacteria;
c) mushrooms;
d) insects.

6. Do not enter into a symbiotic relationship:

a) trees and ants;

b) legumes and rhizobium bacteria;

c) trees and mycorrhizal fungi;

d) trees and butterflies.

a) phytophthora;

b) tobacco mosaic virus;

c) champignon, meadow mushroom;

d) dodder, broomrape.

a) eat only the outer integument of the victim;

b) occupy a similar eco-niche;

c) attack mainly weakened individuals;

d) have similar methods of hunting prey.

9. Wasps-riders are:

b) predators with features of decomposers;

a) fleas;

b) lice;

c) stem nematodes;

d) rust fungi.

a) mushrooms b) worms;

c) fish;

d) birds.

b) broomrape;

c) white mistletoe;

d) head.

a) amoeba - "opaline - frog;

b) frog -> opaline - amoeba;

c) mushrooms - * frog -> opaline;

d) frog - * amoeba - opaline.

III. Learning new material. 1. Teacher's story.

Life on Earth exists due to solar energy, which is transmitted through plants to all other organisms that create a food, or trophic, chain: from producers to consumers, and so 4-6 times from one trophic level to another.

The trophic level is the location of each link in the food chain. The first trophic level is producers, all the rest are consumers. The second level is herbivorous consumers; the third - carnivorous consumers feeding on herbivorous forms; the fourth - consumers consuming other carnivores, etc.

Consequently, it is possible to divide consumers by levels: consumers of the first, second, third, etc. orders.

Energy costs are associated primarily with the maintenance of metabolic processes, which are called respiration expenditure; a smaller part of the costs goes to growth, and the rest of the food is excreted in the form of excrement. Ultimately most of energy is converted into heat and dissipated in environment, and no more than 10% of the energy from the previous one is transferred to the next, higher trophic level.

However, such a strict picture of energy transition from level to level is not entirely realistic, since the trophic chains of ecosystems are intricately intertwined, forming trophic webs.

For example, sea otters eat sea ​​urchins that eat brown algae; the destruction of otters by hunters led to the destruction of algae due to an increase in the population of hedgehogs. When hunting for otters was banned, algae began to return to their habitats.

A significant part of heterotrophs are saprophages and sa-profits (fungi), which use the energy of detritus. Therefore, two types of trophic chains are distinguished: grazing chains, or pasture chains, which begin with the eating of photosynthetic organisms, and detrital decomposition chains, which begin with the decomposition of the remains of dead plants, corpses and animal excrement. So, the flow of radiant energy in an ecosystem is distributed over two types of food webs. The end result: the dissipation and loss of energy, which, in order for life to exist, must be renewed.

2. Work with the textbook in small groups.

Task 2. Specify the features of food relations of typical predators. Give examples.

Task 3. Specify the features of the food relations of animal-gatherers. Give examples.

Task 4. Indicate the features of food relations of grazing species. Give examples.

Note: the teacher should draw the attention of students to the fact that in foreign literature the term denoting relations of the type

In this regard, it must be borne in mind that the term "predator" is used in the literature on ecology in a narrow and broad sense.

Answer to task 1.

Answer to task 2.

Typical predators spend a lot of energy searching, tracking and capturing prey; kill the victim almost immediately after the attack. Animals have developed a special hunting behavior. Examples - representatives of the order of carnivores, mustelids, etc.

Answer to task 3.

Foraging animals spend energy only searching for and collecting small prey. Collectors include many granivorous rodents, chicken birds, carrion vultures, and ants. Peculiar collectors - filter feeders and ground-eaters of reservoirs and soils.

Answer to task 4.

Grazing species feed on abundant food that does not need to be searched for long and is easily available. Usually these are herbivorous organisms (aphids, ungulates), as well as some carnivores (ladybugs on aphid colonies).

3. D and s to s s and I.

Question. In what direction is the evolution of species in the case of

with typical predators? Sample answer.

The progressive evolution of both predators and their prey is aimed at improving the nervous system, including the sense organs, and the muscular system, since selection maintains in prey those properties that help them escape from predators, and in predators, those that help in getting food.

Question. In what direction does evolution go in the case of gathering?

Sample answer.

The evolution of species follows the path of specialization: selection in prey maintains traits that make them less conspicuous and less convenient to collect, namely, protective or warning coloration, imitative resemblance, mimicry.

In o p r o With. In what situations does a person act as a typical predator?

Sample answer.

• Using commercial species(fish, game, fur and hoofed animals);
• when destroying pests.

Note: the teacher should emphasize that in the ideal case, with the competent exploitation of commercial objects (fish in the sea, wild boars and elk in the forest, timber), it is important to be able to foresee the consequences of this activity in order to stay on the fine line between acceptable and excessive use. resource. The purpose of human activity is to preserve and increase the number of "victims" (resource). IV. Anchoring new material. Textbook, §9, questions 1-3. Answer to question 1.

Not always. The nesting area can accommodate only a certain number of birds. The sizes of individual plots determine how many nest boxes will be occupied. The breeding rate of the pest may be so high that the available number of birds will not be able to significantly reduce its numbers.

Answer to question 2.

Simplification of the model is as follows: they did not take into account that prey can run away and hide from predators, predators can feed on different prey; in reality, the fertility of predators depends not only on the food supply, etc., that is, relations in nature are much more complicated.

Answer to question 3.

For moose, the forage base has improved and the death from predators has decreased. Permission for moderate hunting is given if the high number of elk begins to adversely affect the restoration of forests.

Homework:§ 9, task 1; Additional Information.

Nutritional relationships not only provide the energy needs of organisms. They play another important role in nature - they keep kinds in communities, regulate their numbers and influence the course of evolution. Food connections are extremely diverse.

Rice. one. Cheetah chasing prey

Typical predators they spend a lot of effort to track down the prey, catch up with it and catch it (Fig. 1). They have developed a special hunting behavior. They need a lot of sacrifices during their lives. Usually they are strong and active animals.

Animal Gatherers spend energy searching for seeds or insects, i.e., small prey. Mastering the found food for them is not difficult. They have developed search activity, but no hunting behavior.

grazing species do not spend much energy searching for food, there is usually a lot of it around, and most of their time is spent on the absorption and digestion of food.

AT aquatic environment a widespread way of mastering food, such as filtration, and at the bottom - swallowing and passing through the intestines of the soil along with food particles.

Rice. 2. The predator-prey relationship (wolves and reindeer)

The consequences of food ties are most pronounced in relationships predator - prey(Fig. 2).

If a predator feeds on large, active prey that can run away, resist, hide, then those of them who do it better than others remain alive, i.e., have sharper eyes, sensitive ears, a developed nervous system, muscle strength. Thus, the predator selects for the improvement of prey, destroying the sick and the weak. In turn, among predators, too, there is a selection for strength, agility and endurance. The evolutionary consequence of these relationships is the progressive development of both interacting species: predator and prey.

G.F. Gause
(1910 – 1986)

Russian scientist, founder of experimental ecology

If predators feed on inactive or small species that are not able to resist them, this leads to a different evolutionary result. Those individuals that the predator manages to notice die. Victims that are less noticeable or somewhat inconvenient to capture win. This is how it works natural selection on the patronizing coloration, hard shells, protective spikes and needles and other tools of salvation from enemies. The evolution of species goes in the direction of specialization according to these traits.

The most significant result of trophic relationships is the containment of the growth in the number of species. The existence of food relations in nature is opposed to geometric progression breeding.

For each pair of predator and prey species, the result of their interaction depends primarily on their quantitative ratios. If predators catch and destroy their prey at about the same rate as these prey reproduce, then they can hold back growth in their numbers. It is these results of these relationships that are most often characteristic of sustainable natural communities. If the rate of reproduction of prey is higher than the rate of eating them by predators, outburst of numbers kind. Predators can no longer contain its numbers. This, too, occurs occasionally in nature. The opposite result - the complete destruction of the prey by a predator - is very rare in nature, but in experiments and under human-disturbed conditions it is more common. This is due to the fact that with a decrease in the number of any type of prey in nature, predators switch to another, more accessible prey. Hunting only for a rare species takes up too much energy and becomes unprofitable.

In the first third of our century, it was discovered that the predator-prey relationship could cause regular periodic fluctuations numbers each of the interacting species. This opinion was especially strengthened after the results of the research of the Russian scientist G.F. Gauze. In his experiments, G.F. Gause studied how the number of two types of ciliates in test tubes, connected by predator-prey relations, changes in test tubes (Fig. 3). The victim was one of the types of ciliates-shoes, feeding on bacteria, and the predator was a ciliate-didinium, eating shoes.

Rice. 3. The course of the number of ciliates-shoes
and predatory ciliates didinium

Initially, the number of the slipper grew faster than the number of the predator, which soon received a good food base and also began to multiply rapidly. When the rate of eating shoes caught up with the rate of their reproduction, the growth in the number of the species stopped. And since the didiniums continued to catch slippers and multiply, soon the eating of victims far exceeded their replenishment, the number of slippers in test tubes began to decline sharply. Some time later, having undermined their food base, they stopped dividing and didiniums began to die. With some modifications of experience, the cycle was repeated from the beginning. The unhindered reproduction of the surviving slippers again increased their abundance, and after them the curve of the number of didiniums went up. On the graph, the predator abundance curve follows the prey curve with a shift to the right, so that changes in their abundance turn out to be asynchronous.

Rice. four. Reducing the number of fish as a result of overfishing:
the red curve is the global cod fishery; blue curve - the same for capelin

Thus, it was proved that interactions between predator and prey can, under certain conditions, lead to regular cyclic fluctuations in the abundance of both species. The course of these cycles can be calculated and predicted, knowing some initial quantitative characteristics of the species. The quantitative laws of the interaction of species in their nutritional relationships are very important for practice. In fishing, harvesting of marine invertebrates, fur trade, sport hunting, collection of decorative and medicinal plants- wherever a person reduces the number of species he needs in nature, from an ecological point of view, he acts in relation to these species as a predator. Therefore, it is important be able to anticipate the consequences its activities and organize it in such a way as not to undermine natural resources.

In fisheries and fisheries, it is necessary that when the number of species decreases, the fishing rates also decrease, as happens in nature when predators switch to more easily accessible prey (Fig. 4). If, on the contrary, you strive with all your might to extract a declining species, it may not restore its numbers and cease to exist. Thus, as a result of overhunting through the fault of people, a number of species that were once very numerous have already disappeared from the face of the Earth: European tours, passenger pigeons and others.

When predators of a species are killed accidentally or deliberately, outbreaks of the number of its prey first occur. This also leads to ecological disaster either as a result of a species undermining its own food base, or - the spread infectious diseases, which are often much more destructive than the activities of predators. A phenomenon arises ecological boomerang, when the results are directly opposite to the initial direction of influence. Therefore, the competent use of natural environmental laws is the main way of human interaction with nature.

1) hare - clover;

2) woodpecker - bark beetles;

3) fox - hare;

4) a person is an ascaris;

5) bear - elk;

6) bear - bee larvae;

7) blue whale - plankton;

8) cow - timothy;

9) tinder fungus - birch;

10) carp - bloodworm;

11) dragonfly - fly;

12) toothless mollusk - protozoa;

13) aphid - sorrel;

14) caterpillar Siberian silkworm- fir;

15) grasshopper - bluegrass;

16) sponge - protozoa;

17) influenza virus - human;

18) koala - eucalyptus;

19) ladybug beetle - aphid.

138. Choose the correct answer. The result of food relations between populations of foxes and hares will be:

a) decrease in the number of both populations;

b) regulation of the number of both populations;

c) an increase in the number of both populations.

139. Explain the following facts: a) during the mass shooting of birds of prey (hawks, owls) that feed on partridges and black grouse, the number of the latter first increases and then decreases; b) with the extermination of wolves, the number of deer in the same territories also decreases over time.

140. Indicate which of the following groups organisms belong to.

List of organisms:

3) sundew;

4) ixodid tick;

6) bull tapeworm;

7) daphnia;

8) rabbit;

11) tinder fungus;

13) boletus;

14) Koch's wand;

16) female mosquito;

17) earthworm;

18) dung fly larvae;

19) Colorado potato beetle;

21) nodule bacteria;

22) scarab beetle.

141. Explain why in China, after the destruction of sparrows, the grain harvest dropped sharply.

142. Jays feed mainly on oak acorns in autumn. They bury many acorns in the ground as a reserve for the winter and early spring. Describe the mutual benefit of these types of relationships.

143. Specify type biotic relationship, which corresponds to a pair of interacting species in the forest (Fig.).

144. In the middle of summer, after a fire, a bark beetle breeding center arose in the burnt area: all living trees touched by the fire turned out to be damaged by pests. Explain why.

145. How can the phenomenon of predation and parasitism be used in agriculture? Give specific examples.

146. It is known that many insects feed on pines: sawflies, weevils, bark beetles, barbels, etc. Why do pests mainly live on diseased trees and bypass healthy, young pines?

147. One and the same organism can be either a predator or a prey in relation to individuals of different ages of another species. Give examples.

148. Critical importance have nutritional relationships between individuals within a species. Feeding on their own kind - cannibalism - is a fairly common occurrence in fish. Give examples.

149. By creating mathematical model changes in the number of predators and prey, A. Lotka and V. Voltaire assumed that the number of predators depends only on two reasons: the number of victims (the larger the food supply, the more intense reproduction) and the rate of natural decline of predators. At the same time, they understood that they greatly simplified the relationships that exist in nature. What is this simplification?

150. The relationship in the biocenosis, which consists in creating one type of habitat for another, is called:

a) trophic; b) topical; c) phoric; d) factory.

151. A pollinator and a pollinated plant are an example of a relationship:

a) trophic; b) topical; c) phoric; d) factory.

153. Competition for a food object is an example of the relationship: a) trophic; b) topical; c) phoric; d) factory.

154. Interspecific relationships in the biocenosis, based on the participation of one species in the distribution of another, are called: a) topical; b) phoric; c) factory; d) trophic.

155. Building nests by birds natural materials is an example of relationships: a) trophic; b) topical; c) phoric; d) factory.

156. Interspecific relationships in the biocenosis, based on nutritional relationships, are called: a) topical; b) phoric; c) factory; d) trophic.