Aufgabe 2 - Stoffkreisläufe und Einfluss des Mens… · Abitur NRW Biologie GK · Haupttermin · bilingual Englisch 2021

Material A: Sense of Smell in Lobesia botrana

Like other insects, the European grapevine moth ( Lobesia botrana) detects odour molecules 1 (i.e. odoriferous substances) using sensory hairs called sensilla 2 (Figure 1A). These sensilla are present in e.g. the antennae. Every sensillum contains several different olfactory sensory neurons (OSN). Every OSN has only one dendrite, which extends into the sensillum. The axon leads directly to the olfactory centre in the insect’s brain. Odour molecules enter the sensillum through pores in the cuticle (the exoskeleton of insects). The odour molecules dissolve in the liquid contained in the sensillum and can thus reach the dendrite membrane of the OSN. Operating on the lock-and-key principle, they bind briefly at specific olfactory receptor proteins, thus producing a receptor potential (Figure 1B and 1C). Every OSN possesses only one type of receptor protein. Together with co-receptor proteins, the receptor proteins form a channel for cations in the dendrite membrane.

1 Duftstoff

2 Sensille; im Englischen Singular sensillum

Material B: Electrophysiological Investigations

For sexually mature European grapevine moths ( Lobesia botrana), olfaction is essential for locating partners and suitable host plants on which to lay eggs. Females emit species-specific odour molecules from particular glands. These sex pheromones serve to lure males for mating.

Electrophysiological studies were carried out on sensilla from male and female European grapevine moths. The sensilla, containing various OSNs, were exposed to the sex pheromone of female L. botrana and to several plant odours. The experiments used isolated antennae. Once a plant odour had been applied, the frequency of action potentials at the axon of an OSN was recorded. Table 1 and Figure 2 present the results.

Material C: Pheromone Usage in Greenhouses

European grapevine moths and other insects deposit their eggs on grape vines 3. After the larvae hatch in spring, they first feed on the flowers and later on the grapes, thus diminishing the crop yield of grapes. Between spring and autumn up to three generations of L. botrana can develop successively.

In a greenhouse built for viticulture, L. botrana had caused severe feeding damage. Therefore, the following approach was tried in the next growing season: Pheromone traps that selectively attracted male moths were set up all year round in a control unit and in a test unit of the greenhouse. From mid-May onward, the test unit additionally received pheromone dispensers meant to prevent feeding damage to the vines. These dispensers released female sex pheromones of L. botrana into the air, distributing them evenly throughout the test unit. Table 2 shows the results of the experiment.

Insecticides can be used as an alternative to pheromone dispensers in order to control pest insects such as L. botrana. Insecticides are often unspecific toxins which affect several different insect species. When used over a longer period of time there is a danger that pests develop resistances.

3 Weinrebe

4 Traubenbündel

3. Explain the data presented in Table 2 with regard to the effect of pheromone dispensers (Materials A to C). Discuss the use of pheromone dispensers for pest control as an alternative to insecticides (Materials A to C).

(14 Punkte)

a)

b)