Parasitic plants. Parasitic plants, presentation for a biology lesson on the topic Biology of plant parasites

Class: 6

Presentation for the lesson

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Tasks.

Educational.

Create conditions: to use the skills to apply acquired knowledge when answering specific questions.

Developmental. To promote the further development of students’ logical thinking - the formation of the ability to compare, generalize, and give scientific justification.

Educational. Continue: formation of a scientific worldview; fostering a positive attitude towards acquiring knowledge and self-confidence.

Equipment: computer, projector, presentation for the lesson.

During the classes

1. The lesson begins with a review of homework. (Slides No. 2-6)

What is the difference between cultivated and wild plants? Name possible habitats.

List the importance of cultivated and wild plants.

What are the benefits and harms of weeds?

2. New topic.

If you suddenly see some pale pink rags the length of a finger sticking out of the ground, know that you happened to meet Peter's cross. Although, of course, you will have to think about what it is, in any case. The plant is too unusual, you won’t immediately understand what it is. In the lower part, near the ground, the thick white stem is covered with large scales, and above it bears many pink flowers that press tightly against each other. Peter's cross is interesting because it never has green leaves. He simply doesn't need them. It attaches itself to the roots of some trees and shrubs and takes the necessary nutrients from there. This is how he lives. (Slide No. 12)

In another plant - broomrape, in the process of evolution, all organs of plants of this genus, except for the stem, flowers and fruits, underwent significant changes: the roots turned into short fleshy sucker fibers that stick to the roots of the host plant, the leaves lost chlorophyll and became small brownish, yellowish or purple scales with alternate location. The stem of broomrape is light brown, yellowish, fleshy, erect, with a club-shaped base equipped with suckers that penetrate into the root tissue of the host plant. (Slide No. 13)

2.2. Plants are predators.

A problem is presented to the students. Who are called predators in nature? Can there be predators among plants? How do plants benefit from eating animals? (Slides No. 16-17)

There is a group of plants in the magnificent kingdom of Flora, which at all times not only delighted naturalists and naturalists, but also served as an inexhaustible source of inspiration for the creators of chilling fables, in which human imagination more than made up for the lack of accurate knowledge and facts.

These plants belong to different families and live in a wide variety of climatic zones - from the Arctic tundra to the equatorial jungle. But they have one thing in common - they are all predators, whose main business in life is hunting. And even though the prey, by our standards, is small, and the hunting process itself is silent, in these dramatic battles between plant and animal, the great law of the eternal movement of nature is revealed to the attentive observer - the struggle for survival.

Sundews are one of the most common insectivorous plants. They grow all over the world and number about 100 species, most of which live in Australia and New Zealand. Their typical representative is the large-leaved sundew, which often grows in the swamps of the temperate zone of the Northern Hemisphere.

An inviting drop of “dew” turns out to be sticky mucus, which deprives the insect of the opportunity to escape. The sundew leaf is unusually sensitive - just the lightest touch is enough, and all its hairs begin to move, bending towards the center in an effort to “generously” cover the victim with an adhesive substance and move it to the very middle of the leaf - where the digestive villi are located. Gradually, the sundew leaf closes over the insect, turning into a kind of tiny stomach.

The digestion process usually takes several days. Sundew glands secrete a liquid containing organic acids (mainly benzoic and formic) and digestive enzymes such as pepsin, which break down insect proteins into simpler compounds that the plant can absorb. From insects caught by sundews, only chitinous covers, insoluble by enzymes, remain, which are soon washed off from the surface of the trapping leaf by rain or carried away by the wind. (Slides No. 18-19)

Very effective dexterous device Venus flytrap, inhabitant of North America. Although this plant is related to the sundew, it uses a completely different method of hunting. Its modified leaves are a miniature copy of a steel trap.

Dicotyledonous leaf blades have a kind of hinge in the middle that allows them to fold. Each half of the leaf is equipped with three sensitive hairs that respond to touch. The leaves of the Venus flytrap act with lightning speed - as soon as the insect barely touches the sensitive hairs, the halves of the leaf instantly slam shut, their jagged edges overlap each other and the victim finds itself in a reliable trap. It is not easy to open a slammed leaf of a plant - it is more likely to tear than give way. Unlike the sundew, the flycatcher is able to distinguish between living and inanimate objects - small specks caught in a trap do not attract the slightest attention. For the same reason, a small gap remains between the two halves of the slammed sheet - too small prey, which is not worth wasting time on, can escape the trap. But if the victim is sufficiently well-fed, then after catching it, the trap shrinks more and more, trying to crush the insect and press it against the digestive glands. (Slides No. 20-21)

They have acquired even more complex devices for catching insects. nepenthes, or pitcher plants. These are usually vines that live in swampy soils along the edges of evergreen tropical forests. Their climbing or creeping stems sometimes reach 20 meters in length. The curly leaves end in long tendrils, on which hang rather large jugs, mottled with reddish spots and emitting a strong odor. Attracted by the nectar and bright colors, the insects climb up the edge of this trap, which usually ends with them falling to the bottom of the jug, into the liquid containing digestive enzymes. For greater reliability, the jug is equipped with jagged edges hanging from the top. (Slides No. 22-26)

3. Consolidation. (Slide No. 27)

Questions for consolidation:

What plants are called predators? Give examples of such plants.

What benefits do carnivorous plants benefit from eating animals?

Slide 2

Direct influence of plants on each other

The influences can be direct when plants come into contact.

Slide 3

Lianas

They twine around trunks, hang from branches, spread from tree to tree, like snakes, crawl along the ground or lie on it in tangled balls - this is how the English traveler Alfred Wallace described vines in the tropics.

Slide 4

Slide 5

Evergreens, vines, shrubs with thick climbing stems