Abitur NRW Biologie 2021 · GK · Haupttermin · bilingual Englisch

Material A: The Grape as a Habitat

The ripe fruits of the common grape vine ( Vitis vinifera) are a source of nutrition as well as a habitat for many organisms. Yeasts, to which the so-called “baker’s yeast” ( Saccharomyces cerevisiae) belongs, are single-celled fungi. In nature, baker’s yeast occurs primarily on fruits. In autumn, they spread rapidly on ripe, sugary grapes. They ferment the sugar to gain energy, creating alcohol and various volatile 1 substances in the process. Other fungi, such as the grey mould ( Botrytis cinereum) or Penicillium species, also use the grapes as a nutrient source.

The fruit fly ( Drosophila melanogaster) is found all around the world and lives on various fruits and other organic material. Adult fruit flies use overripe and fermenting grapes as a source of nutrition and as a substrate for egg deposition. The flies and their larvae consume not only the grapes, but also the baker’s yeast growing on them. The yeast contains essential amino acids, lipids and vitamins.

Ichneumon wasps 2 of the genus Leptopilina are able to lay an egg inside of a fruit fly larva. After hatching, the ichneumon larva eats the fruit fly from the inside out. It emerges from the remains of the fruit fly larva when it has reached maturity. The zebra spider ( Salticus scenicus) hunts insects which live on the ripe, fermenting grapes. They jump on their prey from a distance of several centimetres and kill them with their venomous bite.

1 flüchtig

2 Schlupfwespe

Material B: Dispersion of Baker’s Yeast on Grapes

An experiment was conducted using adult fruit flies. The flies were bred in a laboratory and had had no contact with baker’s yeast before the experiment. At the start of the experiment, these fruit flies were fed for one day either with food including living baker’s yeast or with yeast-free food. A single fruit fly from each food group was then placed on a sterilised, yeast-free grape. Grapes without fruit flies were used as controls (Table 1).

Table 1 Growth of baker’s yeast on grapes. Each experiment was repeated 10 times. Experiment · Grapes with baker’s yeast growth

Fruit flies fed with yeast-free food · 0

Fruit flies fed with food containing yeast · 10

Control without fruit fly · 0

Material C: Reproduction of the Fruit Fly

The effect of the fruits and of the baker’s yeast on the reproduction of fruit flies was studied in further experiments. Four different tests were conducted, each using a different food source: grapes, grapes fermented by baker’s yeast, a grape-free nutrient medium for fruit flies, and a nutrient medium fermented by baker’s yeast. The odoriferous substances 3 released by these test foods were collected. Each was placed individually in a wind tunnel containing 20 fruit flies. After 15 minutes, the number of fruit flies which had flown into the wind and had landed on the source of the smell was noted (Figure 1A).

In another experiment, a substrate for egg deposition was created out of each of the four food sources. To each of the four egg deposition substrates, 20 fertilised fruit fly females were given, and the number of eggs laid was noted after 24 hours (Figure 1B).

In a third experiment, two-day-old, yeast-free fruit fly larvae were placed together with either a piece of grape (with or without baker’s yeast) or with a nutrient medium (with or without baker’s yeast). The percentage of larvae which developed into adult fruit flies was then noted (Figure 1C).

3 Duftstoffe

Material D: Odoriferous Substances in Yeasts

There are 83 genera of yeasts containing approximately 600 species. Many of these fungi produce odoriferous substances. Seven different yeast species which are not phylogenetically closely related were used in an experiment. Each of these species can be clearly differentiated from the others by its life requirements: some live on fruits, others on insects, in milk or as pathogens of humans. In a wind tunnel experiment similar to that described in Material C, it was analysed how many adult fruit flies landed on each odoriferous substance collected from these different yeast species (Figure 2).

Topic: Fruit as a Habitat

1.

Using Material A, sketch a food web and name its trophic levels, justifying your answer (Material A). [11 Punkte]

2.

Sum up the results presented in Table 1 and, building on them, explain how important the fruit fly is for the baker’s yeast (Materials A and B). Describe the results shown in Figure 1, then analyse and evaluate them regarding the role of the odoriferous substances in the fruit fly’s reproduction (Materials A and C). Check whether a symbiotic relationship between the baker’s yeast and the fruit fly is possible (Materials A to C). [27 Punkte]

Material A: The Grape as a Habitat

The ripe fruits of the common grape vine ( Vitis vinifera) are a source of nutrition as well as a habitat for many organisms. Yeasts, to which the so-called “baker’s yeast” ( Saccharomyces cerevisiae) belongs, are single-celled fungi. In nature, baker’s yeast occurs primarily on fruits. In autumn, they spread rapidly on ripe, sugary grapes. They ferment the sugar to gain energy, creating alcohol and various volatile 1 substances in the process. Other fungi, such as the grey mould ( Botrytis cinereum) or Penicillium species, also use the grapes as a nutrient source.

The fruit fly ( Drosophila melanogaster) is found all around the world and lives on various fruits and other organic material. Adult fruit flies use overripe and fermenting grapes as a source of nutrition and as a substrate for egg deposition. The flies and their larvae consume not only the grapes, but also the baker’s yeast growing on them. The yeast contains essential amino acids, lipids and vitamins.

Ichneumon wasps 2 of the genus Leptopilina are able to lay an egg inside of a fruit fly larva. After hatching, the ichneumon larva eats the fruit fly from the inside out. It emerges from the remains of the fruit fly larva when it has reached maturity. The zebra spider ( Salticus scenicus) hunts insects which live on the ripe, fermenting grapes. They jump on their prey from a distance of several centimetres and kill them with their venomous bite.

1 flüchtig

2 Schlupfwespe

Material B: Dispersion of Baker’s Yeast on Grapes

An experiment was conducted using adult fruit flies. The flies were bred in a laboratory and had had no contact with baker’s yeast before the experiment. At the start of the experiment, these fruit flies were fed for one day either with food including living baker’s yeast or with yeast-free food. A single fruit fly from each food group was then placed on a sterilised, yeast-free grape. Grapes without fruit flies were used as controls (Table 1).

Table 1 Growth of baker’s yeast on grapes. Each experiment was repeated 10 times. Experiment · Grapes with baker’s yeast growth

Fruit flies fed with yeast-free food · 0

Fruit flies fed with food containing yeast · 10

Control without fruit fly · 0

Material C: Reproduction of the Fruit Fly

The effect of the fruits and of the baker’s yeast on the reproduction of fruit flies was studied in further experiments. Four different tests were conducted, each using a different food source: grapes, grapes fermented by baker’s yeast, a grape-free nutrient medium for fruit flies, and a nutrient medium fermented by baker’s yeast. The odoriferous substances 3 released by these test foods were collected. Each was placed individually in a wind tunnel containing 20 fruit flies. After 15 minutes, the number of fruit flies which had flown into the wind and had landed on the source of the smell was noted (Figure 1A).

In another experiment, a substrate for egg deposition was created out of each of the four food sources. To each of the four egg deposition substrates, 20 fertilised fruit fly females were given, and the number of eggs laid was noted after 24 hours (Figure 1B).

In a third experiment, two-day-old, yeast-free fruit fly larvae were placed together with either a piece of grape (with or without baker’s yeast) or with a nutrient medium (with or without baker’s yeast). The percentage of larvae which developed into adult fruit flies was then noted (Figure 1C).

3 Duftstoffe

Material D: Odoriferous Substances in Yeasts

There are 83 genera of yeasts containing approximately 600 species. Many of these fungi produce odoriferous substances. Seven different yeast species which are not phylogenetically closely related were used in an experiment. Each of these species can be clearly differentiated from the others by its life requirements: some live on fruits, others on insects, in milk or as pathogens of humans. In a wind tunnel experiment similar to that described in Material C, it was analysed how many adult fruit flies landed on each odoriferous substance collected from these different yeast species (Figure 2).

3. Define the term coevolution. Sum up the findings presented in Figure 2 (Material D) and, drawing on all of the materials, discuss to what extent the relationship between the fruit fly and the baker's yeast can be regarded as an example of coevolution (Materials A to D). (16 Punkte)

a)

b)

c)

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

Topic: Pheromone Usage to Control Lobesia botrana in Wine Growing

1.

Name the tasks of dendrites and axons, and use Figure 1 to present the signal transduction in the olfactory sensory neurons of insects as a flow chart (Material A). Explain, at the neurophysiological level, how the receptor potential shown in Figure 1C develops over time (Material A). [16 Punkte]

2.

Sum up the data presented in Table 1 and Figure 2 (Material B), then analyse and evaluate them with regard to neurobiological aspects (Materials A and B). Drawing on neurobiological aspects, develop a well-reasoned hypothesis explaining why the action potential frequencies differ between OSN I and OSN A (Material B). Illustrate the selective advantages that a specialised sense of smell offers male and female L. botrana (Material B). [24 Punkte]

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)

Material A: Warmblood Fragile Foal Syndrome in Horse Breeding

Warmblood fragile foal syndrome (WFFS) is a hereditary disease in horses which leads to an incurable connective tissue disorder. Foals affected by WFFS show symptoms immediately after birth. Already in the first hours of life, they contract injuries in the ligaments, tendons and bones, which hardly heal and are eventually fatal. WFFS is inherited in an autosomal recessive pattern.

Although WFFS has been in existence for an estimated 170 years, an increase in cases has been documented since 2011. Between six and eleven percent of all horses are carriers of this gene defect. Horses which have been bred for equestrian sports 1 are especially affected. In breeding, one breeding stallion 2 is mated with several female horses. Scientists suspect a connection between the mutation underlying WFFS and the traits desired in the breeding of sports horses, such as a high level of agility.

1 Pferdesport

2 Zuchthengst

Material B: Molecular genetic causes of WFFS

Connective tissue consists mostly of collagen. Collagen is a fibrous protein which is involved in the production of connective tissues – such as in the skin, blood vessels, tendons and cartilage – as well as in the production of bones and teeth. Up to 25 % of the protein in a human or animal body consists of collagen. The gene PLOD1 codes for the enzyme lysyl-hydroxylase 1 (LH1), which is involved in an intermediate step in the synthesis of stable collagen fibres. In order to gain insights into the molecular genetic causes of WFFS, the PLOD1 gene was sequenced (Table 1).

Table 1 Section of the non-template strand of the PLOD1 gene of a healthy foal and a foal affected by WFFS. · Number of triplet

691 · 692 · 693 · 694 · 695 · 696 · 697

Normal allele · TAC · GAG · GGC · GGG · GGC · TGT · CGG · 5' → 3'

Mutated allele · TAC · GAG · GGC · AGG · GGC · TGT · CGG · 5' → 3'

Material C: Detecting WFFS

When breeding horses, it is recommended to test the horses. For this purpose, DNA is isolated from the blood or other tissues of the animals to be tested. Then, the procedure shown in Figure 1 is used to detect the mutation with the help of a specialised PCR. In this type of PCR, two additional probes are used which do not serve as primers. Each nucleotide of the probes is complementary to the nucleotides of the DNA sequence investigated, either with or without the mutation. Both probes are attached to different fluorescent dyes at their 5' ends, whereas quenchers 3 are attached at their 3' ends. If both the dye and the quencher of the probe are bound, the quencher inhibits the fluorescence of the dye.

3 hier: Entleuchter

During PCR, the fluorescence of the PCR sample is measured. Figure 2 gives exemplary values of the fluorescence which would be expected over the course of such a PCR for horses with different PLOD1 genotypes.

Material D: Diagram and Codon Table of the Genetic Code

1. Name how the evolutionary factors mutation and selection are defined. Using these definitions, illustrate why WFFS occurs more frequently in horses used in sports (Material A).

[10 Punkte]

a)

b)

c)

Material A: Warmblood Fragile Foal Syndrome in Horse Breeding

Warmblood fragile foal syndrome (WFFS) is a hereditary disease in horses which leads to an incurable connective tissue disorder. Foals affected by WFFS show symptoms immediately after birth. Already in the first hours of life, they contract injuries in the ligaments, tendons and bones, which hardly heal and are eventually fatal. WFFS is inherited in an autosomal recessive pattern.

Although WFFS has been in existence for an estimated 170 years, an increase in cases has been documented since 2011. Between six and eleven percent of all horses are carriers of this gene defect. Horses which have been bred for equestrian sports 1 are especially affected. In breeding, one breeding stallion 2 is mated with several female horses. Scientists suspect a connection between the mutation underlying WFFS and the traits desired in the breeding of sports horses, such as a high level of agility.

1 Pferdesport

2 Zuchthengst

Material B: Molecular genetic causes of WFFS

Connective tissue consists mostly of collagen. Collagen is a fibrous protein which is involved in the production of connective tissues – such as in the skin, blood vessels, tendons and cartilage – as well as in the production of bones and teeth. Up to 25 % of the protein in a human or animal body consists of collagen. The gene PLOD1 codes for the enzyme lysyl-hydroxylase 1 (LH1), which is involved in an intermediate step in the synthesis of stable collagen fibres. In order to gain insights into the molecular genetic causes of WFFS, the PLOD1 gene was sequenced (Table 1).

Table 1 Section of the non-template strand of the PLOD1 gene of a healthy foal and a foal affected by WFFS. · Number of triplet

691 · 692 · 693 · 694 · 695 · 696 · 697

Normal allele · TAC · GAG · GGC · GGG · GGC · TGT · CGG · 5' → 3'

Mutated allele · TAC · GAG · GGC · AGG · GGC · TGT · CGG · 5' → 3'

Material C: Detecting WFFS

When breeding horses, it is recommended to test the horses. For this purpose, DNA is isolated from the blood or other tissues of the animals to be tested. Then, the procedure shown in Figure 1 is used to detect the mutation with the help of a specialised PCR. In this type of PCR, two additional probes are used which do not serve as primers. Each nucleotide of the probes is complementary to the nucleotides of the DNA sequence investigated, either with or without the mutation. Both probes are attached to different fluorescent dyes at their 5' ends, whereas quenchers 3 are attached at their 3' ends. If both the dye and the quencher of the probe are bound, the quencher inhibits the fluorescence of the dye.

3 hier: Entleuchter

During PCR, the fluorescence of the PCR sample is measured. Figure 2 gives exemplary values of the fluorescence which would be expected over the course of such a PCR for horses with different PLOD1 genotypes.

Material D: Diagram and Codon Table of the Genetic Code

2. Name four properties of the genetic code and use Table 1 to determine the amino acid sequence and the type of mutation (Materials B and D). Explain what the mutation could mean for collagen synthesis and give reasons for the symptoms of WFFS (Materials A and B).

[18 Punkte]

a)

b)

c)

d)

Material A: Warmblood Fragile Foal Syndrome in Horse Breeding

Warmblood fragile foal syndrome (WFFS) is a hereditary disease in horses which leads to an incurable connective tissue disorder. Foals affected by WFFS show symptoms immediately after birth. Already in the first hours of life, they contract injuries in the ligaments, tendons and bones, which hardly heal and are eventually fatal. WFFS is inherited in an autosomal recessive pattern.

Although WFFS has been in existence for an estimated 170 years, an increase in cases has been documented since 2011. Between six and eleven percent of all horses are carriers of this gene defect. Horses which have been bred for equestrian sports 1 are especially affected. In breeding, one breeding stallion 2 is mated with several female horses. Scientists suspect a connection between the mutation underlying WFFS and the traits desired in the breeding of sports horses, such as a high level of agility.

1 Pferdesport

2 Zuchthengst

Material B: Molecular genetic causes of WFFS

Connective tissue consists mostly of collagen. Collagen is a fibrous protein which is involved in the production of connective tissues – such as in the skin, blood vessels, tendons and cartilage – as well as in the production of bones and teeth. Up to 25 % of the protein in a human or animal body consists of collagen. The gene PLOD1 codes for the enzyme lysyl-hydroxylase 1 (LH1), which is involved in an intermediate step in the synthesis of stable collagen fibres. In order to gain insights into the molecular genetic causes of WFFS, the PLOD1 gene was sequenced (Table 1).

Table 1 Section of the non-template strand of the PLOD1 gene of a healthy foal and a foal affected by WFFS. · Number of triplet

691 · 692 · 693 · 694 · 695 · 696 · 697

Normal allele · TAC · GAG · GGC · GGG · GGC · TGT · CGG · 5' → 3'

Mutated allele · TAC · GAG · GGC · AGG · GGC · TGT · CGG · 5' → 3'

Material C: Detecting WFFS

When breeding horses, it is recommended to test the horses. For this purpose, DNA is isolated from the blood or other tissues of the animals to be tested. Then, the procedure shown in Figure 1 is used to detect the mutation with the help of a specialised PCR. In this type of PCR, two additional probes are used which do not serve as primers. Each nucleotide of the probes is complementary to the nucleotides of the DNA sequence investigated, either with or without the mutation. Both probes are attached to different fluorescent dyes at their 5' ends, whereas quenchers 3 are attached at their 3' ends. If both the dye and the quencher of the probe are bound, the quencher inhibits the fluorescence of the dye.

3 hier: Entleuchter

During PCR, the fluorescence of the PCR sample is measured. Figure 2 gives exemplary values of the fluorescence which would be expected over the course of such a PCR for horses with different PLOD1 genotypes.

Material D: Diagram and Codon Table of the Genetic Code

Teilaufgabe 3

Describe the main stages of the PCR method and illustrate what role the fluorescent probes play in detecting the WFFS alleles shown in Figure 1 (Material C). Building on this, analyse and evaluate the findings of the study in Figure 2 (Material C). Providing reasons, derive measures that could help to lower the number of WFFS cases among sports horses (Materials A to C). [26 Punkte]

a)

b)

c)

d)