1

Wildflower population: Genetic drift1

Figure 1: Field of tulips (Image: Sakurai Midori, Source:

http://upload.wikimedia.org/wikipedia/commons/thumb/a/a2/Lily_flowered_tulip.jpg/800px-Lily_flowered_tulip.jpg)

There are 40 plants of one species on a meadow. They differ only in the colour of their flower (which

is inherited): there are 10 red flowers, 10 white flowers, 10 green flowers and 10 blue ones. A blind

snail that also lives on the meadow eats one plant a day, not preferring plants with a specific

coloured flower. Every time a plant has been eaten, another one is able to reproduce itself (by

producing a stolon, for example) and occupies the free space.

Tasks:

1a) Tick your hypothesis for the development of the population:

o There will be a major change in the composition of the population.

o The proportions of the flower colors will always range around 25%.

1 Game based on: Scheersoi, A. & Kullmann,H. 2007. さGWﾐSヴｷaデ ┌ﾐS “WﾉWﾆデｷﾗﾐ ゲヮｷWﾉWヴｷゲIｴ ┗WヴﾏｷデデWﾉﾐくさ Praxis der

Naturwissenschaften-Biologie in der Schule 7: 45-47.

Material: wooden beads, bag, petri dishes

2

1b) Simulate the development of the population by following the game instructions. After each

turn, write down the composition of the population in Table 1.

1c) Tick how the wildflower population has evolved.

o There has been a major change in the composition of the wildflower population on account

of the snail.

o The proportions of the flower colors have always ranged around 25%.

1d) Note the assumptions of the model about the influence of evolutionary factors on the

wildflower population.

Game Instructions:

Put 10 beads of each colour (10 red ones, 10 white

ones, 10 green ones and 10 blue ones) in the bag.

They represent the different coloured flowers. Draw

one bead from the bag and put it in the petri dish. A

plant of this colour is eaten by the blind snail. Draw

a second bead, representing the flower which can

reproduce itself. Therefore you have to add a

second bead of this colour and put both of them

back in the bag. The number of beads in the bag

should be 40 after each move. Write the amount of

W;Iｴ Iﾗﾉﾗ┌ヴ Sﾗ┘ﾐく Nﾗ┘ ｷデ ｷゲ デｴW ﾐW┝デ ヮﾉ;┞Wヴげゲ デ┌ヴﾐく When you have finished, you should analyse how

the population has developed.

3

1e) Optional task: Explain how you would change the game if the beads did not represent

different flower colours but different alleles.

Vocabulary list

English German

allele Allel

bead Perle

composition Zusammensetzung

evolve (from sth.) sich (aus etwas) entwickeln

flower Blüte

Genetic Drift Gendrift

meadow Wiese

petri dish Petrischale

proportion Anteil

range schwanken

reproduce sich fortpflanzen

stolon Ausläufer

4

Table 1: Development of the wildflower population

number of

turns/days

number of flowers

red white blue green

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

number of

turns/days

number of flowers

red white blue green

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

1

Cabbage: Artificial Selection

Several vegetables have been produced from the wild cabbage as a result of artificial selection

(domestication) that has begun about 2000 years ago. Today, kale, Brussels sprouts, broccoli,

kohlrabi, head of cabbage and cauliflower, amongst others, belong to its most popular cultivated

forms.

German English

Wildkohl wild cabbage

Grünkohl kale

Kopfkohl head of cabbage

Rosenkohl Brussels sprouts

Kohlrabi kohlrabi

Blumenkohl cauliflower

Brokkoli broccoli

German English

Endknospe terminal bud

Blütenstand peduncle

Blatt leaf

Hauptachse main axis

Seitenknospe lateral bud

Material: wild cabbage, kale, head of cabbage, Brussels sprouts, kohlrabi, cauliflower, broccoli, scissors

Figure 1: Vegetables derived from the wild cabbage (Saedler,

HWｷﾐ┣く ヲヰヱヲく さ“WﾉWﾆデｷﾗﾐくざWiS Begierig 4: 14.)

Figure 2: Plant organs in 1st

and 2nd

year (Saedler, Heinz.

ヲヰヱヲく さ“WﾉWﾆデｷﾗﾐくざWiS Begierig 4: 11)

2

Tasks:

1) Compare the different vegetables (Fig. 1) to the wild cabbage. Find out for each vegetable which

organ (Fig. 2) differs most from the wild cabbage and how. You may use scissors to cut parts of the

plants off to examine them. Write down your results by putting the terms below to the right place

in Table 1.

enlarged (x2)

thickened

transformed (x2)

crimped

Table 1: Which selection has led to which vegetable?

vegetable\ organ

1st

year 2nd

year

terminal bud main axis leaf peduncle lateral bud

kale

head of cabbage

kohlrabi

Brussels sprouts

cauliflower

broccoli

3

Vocabulary list

English German

artificial selection künstliche Selektion

broccoli Brokkoli

Brussels sprouts Rosenkohl

cauliflower Blumenkohl

crimped gekräuselt

cultivated bebaut, kultiviert

domestication Domestikation

enlarged vergrößert

head of cabbage Kopfkohl

kale Grünkohl

kohlrabi Kohlrabi

lateral bud Seitenknospe

leaf Blatt

main axis Hauptachse

peduncle Blütenstand

scissors Schere

terminal bud Endknospe

thickened verdickt

transformed umgewandelt

wild cabbage Wildkohl

1

Cacti: Natural Selection

Most cacti live on the American continent, in extremely dry environments like deserts. Since water is

scarce there, their habitat poses a challenge to them. They show several adaptednesses to drought.

Tasks:

1) How might the visible traits of cacti contribute to efficient water use? Examine the cacti

and assign the functions below to the adaptednesses listed in Table 1.

reduction of transpiration rate (x2)

protection from herbivores

provide shade (x2)

store water

photosynthesis

Table 1: Adaptednesses of cacti and their functions

adaptedness

functions of the structure

thick stems with cylindrical or spherical

shape (low surface area-to-volume ratio)

thick waxy coverings (cuticles)

ribs

green stems

modified leaves: spines

Material: cacti

2

2) Put the statements below (a-e) in the right order to describe how the adaptation of the stem

shapes of cacti has occurred over a long period of time.

a. Plants with a rather spherical shape were more likely to survive and reproduce themselves

because they lost less water through transpiration. They had a greater relative fitness.

b. Originally, the individuals of the plant population had a non-spherical shape.

c. The frequencies of alleles for a spherical shape increased in the gene pool of the next

generations.

d. On account of further mutations and/or recombination, individuals with an even more

spherical shape appeared which lost even less water.

e. Plants with a rather spherical shape resulted from mutations.

3) Discuss in your group the different meanings of the terms adaptation and adaptedness in

the sentences a. and b. below. Try to come up with a short definition for both terms.

a. The adaptation of the stem shapes of cacti to the drought occurred over many generations.

b. The spherical shape of cacti stems is an adaptedness to drought.

Adaptation is

Adaptedness is

Figure 1: Barrel cactus (Source: http://www.garden-

services.com/gallery/cacti/images/cactusbarrel.jpg)

3

Vocabulary list

English German

adaptation Anpassung

adaptedness Angepasstheit

cactus, pl.:cacti/cactuses Kaktus, pl.: Kakteen

cuticle Cutikula

cylindrical zylindrisch

drought Trockenheit

gene pool Genpool

herbivore Pflanzenfresser

surface area-to-volume ratio Oberfläche-zu-Volumen-Verhältnis

natural selection natürliche Selektion

photosynthesis Photosynthese

relative fitness Darwin-Fitness, evolutionäre Fitness

rib Rippe

scarce knapp

shade Schatten

spherical kugelförmig

spine Dorn

transpiration rate Transpirationsrate

waxy wachsartig

1

Maize: Recombination

Chance events like mutation and sexual recombination are sources of genetic variation in the gene

pool of a population. They are also responsible for the great diversity of maize. Every grain of a maize

ear is produced from an individual fertilization. Thus, hundreds of offspring can be analysed on a

single ear. The phenotypes that will be studied in the following activity on interchromosomal

recombination (i.e. the assortment of chromosomes of the parents to the gametes) are the grain

colour and grain texture.

Tasks:

1a) The maize ears at hand are the F2 generation which results from the cross between a plant

homozygous for purple (R/R) and smooth (Su/Su) grains and a plant homozygous for yellow

(r/r) and wrinkled (su/su) grains. Assign the phenotypes to the genotypes in Table 1 by using

crayons: Indicate wrinkled grains by stripes and smooth grains by colouring the whole field

using a yellow (for yellow grains) or purple (for purple grains) crayon. Remember: Capital

letters indicate dominant alleles.

P: R/R Su/Su x r/r su/su

F1: R/r Su/su

F1 Cross: R/r Su/su x R/r Su/su

Table 1: Gametes of the F1 generation and genotypes of the F2 generation

F2:

gametes

R Su R su r Su r su

R Su

R/R Su/Su R/R Su/su R/r Su/Su R/r Su/su

R su

R/R Su/su R/R su/su R/r Su/su R/r su/su

r Su

R/r Su/Su R/r Su/su r/r Su/Su r/r Su/su

r su

R/r Su/su R/r su/su r/r Su/su r/r su/su

Material: maize ears of F2 generation from the heredity below, yellow

and purple crayons

2

1b) State in which proportion you expect the phenotypes of the maize ear at hand.

1c) Count the grains of each phenotype. Calculate the total number of grains and the total of

each phenotype and record them in Table 1. Check if the numbers for each phenotype

correspond to the numbers you would have expected according to 1b).

Table 2: Numbers for each phenotype of grains

phenotype class purple,

smooth

purple,

wrinkled

yellow,

smooth

yellow,

wrinkled

total number

of grains

ear 1

ear 2

ear 3

total number for each phenotype

expected number for each phenotype

2) Optional task: How many possible combinations of interchromosomal recombination, i.e.

how many different gametes are there for maize with n= 10 chromosomes? Enter the outcome:

3

Vocabulary list

English German

allele Allel

assortment Mischung

crayon Buntstift

diversity Vielfalt

fertilization Befruchtung

gamete Gamet/Keimzelle

gene pool Genpool

genetic variation genetische Variation

grain of maize Maiskorn

interchromosomal

recombination

interchromosomale

Rekombination

maize Mais

maize ear Maiskolben

offspring Nachkommenschaft

phenotype Phänotyp

population Population

proportion Anteil

recombination Rekombination

smooth glatt

wrinkled runzelig

purple violett

1

Maize-Darts: Mutation

Chance events like mutation and sexual recombination are sources of genetic

variation in the gene pool of a population. They are also responsible for the

great diversity of maize. The indigenous peoples of the Americas domesticated

the wild crop relative Teosinte (Fig. 1) to maize. Although these two plants look

very different from each other, some of the major changes are due to only one

mutated gene each. As the natives had opened up of the new food source

maize, they could spend more time for cultural activities: civilizations of the

Americas known for their cultural achievements like the Maya came into being.

Tasks:

1a) The picture on the dartboard (Fig. 2) shows the maize

genome with its 10 chromosomes in a gamete. It is retraced

from the photo of an electron microscope. Step behind the

line on the floor, put the blindfold on so that you cannot

see anything and throw the darts at the dartboard (at

least 15 times). Write down in Table 1 how often you

threw the darts and how often you hit a chromosome.

Figure 1: Wild crop relative Teosinte ( Saedler,

Heinz. 2011 く さM;ｷゲ-DﾗﾏWゲデｷﾆ;デｷﾗﾐくざ WiS

Begierig: 7)

Material: dartboard with picture of maize genome, darts

More on the diversity of Maize: transposable elements

The great diversity of Maize results from the fact that its genome contains 85%

transposable elements which are responsible for 80% of spontaneous

mutations. Transposable elements are genes or parts of genes which can change

their position within the genome of a cell. They can either be copied

(retrotransposons) or cut out (DNA transposons) and pasted to a different

position. Their activity may lead to new sequences. Transposable elements are

pervasive in multi-cellular organisms.

Figure 2: Genome in a gamete of maize (modified

after Saedler, Heinz. 2012. WiS Begierig 4: 15)

2

1b) Rates of spontaneous mutations in organisms range from 10-6 to 10-5 per gene and

generation. That means that only one cell of 1.000.000 to one of 100.000 cells have a mutation in

the considered gene. Most mutations can be repaired by mechanisms of the cell. If every throw

targeted another gamete of one generation, what would be the rate of spontaneous mutations

in Maize? Add the throws and hits of your group and gross up to 100.000 throws in Table 1.

Table 1: Darts results

1c) Name the characteristics of mutations which are represented by the dartboard model.

1d) Which characteristic of the genome is not considered in the dartboard model?

1e) Why is it important for evolution that the mutation occurs in the gamete?

Give reasons.

pupil 1 pupil 2 pupil 3 total

hits

throws

total hits per throws

hits per 100.000 throws

3

Vocabulary list

English German

blindfold Augenbinde

crop Anbaupflanzen,pl.

dartboard Dartscheibe

dart Dartpfeil

diversity Vielfalt

DNA transposon DNA-Transposon

electron microscope Elektronenmikroskop

gamete Gamet, Keimzelle

genetic variation genetische Variabilität

gross up hochrechnen

hit Treffer

indigenous einheimisch

maize Mais

multi-cellular vielzellig

mutation Mutation

pervasive überall vorhanden

retrotransposon Retrotransposon

throw Wurf

transposable element Transposon

1

Neolithic Revolution

About 12.000 years ago, people began to

cultivate plants in the region of the Fertile

Crescent (in parts of what today is Lebanon,

Syria, Turkey, Iraq, Iran, Jordan and Israel)

(Fig. 1). Thereby they laid the foundation

for the Neolithic Revolution.

Task:

1. Use the internet to find out about the Neolithic Revolution. Describe shortly what

the Neolithic Revolution was and how it affected human societies. You may use

ﾗﾐW ﾗa デｴW ﾉｷﾐﾆゲ HWﾉﾗ┘ ﾗヴ ┌ゲW ﾆW┞┘ﾗヴSゲ ﾉｷﾆW さNWﾗﾉｷデｴｷI RW┗ﾗﾉ┌デｷﾗﾐざが さNWﾗﾉｷデｴｷI Eヴ;ざが さNWﾗﾉｷデｴｷI AｪWざ aﾗヴ ┞ﾗ┌ヴ ケ┌Wゲデく

http://www.h2g2.com/approved_entry/A2054675

http://www.smm.org/catal/mysteries/what_were_they_eating/hunting_and_gathering/

http://history-world.org/agriculture.htm

Neolithic Revolution:

Vocabulary list

English German

fertile crescent Fruchtbarer Halbmond

Neolithic Age/Era Neolithikum

Neolithic Revolution Neolithische Revolution

Figure 1: Region of the Fertile Crescent (Saedler, Heinz. ヲヰヱヱく さA┌a SWﾏ WWｪ ┣┌ヴ HW┝;ヮﾉﾗｷSｷWぎ EﾏﾏWヴ ┌ﾐS DｷﾐﾆWﾉくざ Wｷ“ BWｪｷWヴｷｪ ヱ: 9.)

Material: computer with access to the internet

1

Wheat: Artificial Selection

At the beginning of the Neolithic Era about 12.000 years ago, harvesting the wheat ancestor Wild

Einkorn was cumbersome as the ripe spikes were very brittle and shattered easily (shattering spikes)

into the single spikelets which contained only one grain each. These grains then had to be collected.

Afterwards, the protective tough glumes which enclosed the grains (hulledness) had to be removed.

These features enabled the spikelets and the grains to disperse. Many years of domestication passed

by until modern day wheat forms like soft and durum wheat have evolved. Their spikes do not

shatter easily (non-shattering spikes) and have light glumes (free-threshing).

Tasks:

1) Time travel: Think back to the time of the Neolithic Era was when agriculture expanded. Your

family is starving and tired from hunting and gathering. One day you meet a traveller from far away.

He sells wheat spikes to you which are different from the ones you know in some respects. He

promises that these spikes would mean an end to your food shortage. However, unfortunately you

have mixed them up with the spikes you already had. Now you have to decide about which grains to

sow and it is up to you to assure the survival ﾗa ┞ﾗ┌ヴ a;ﾏｷﾉ┞ぐ

Take the spikes labelled 1 and 2 in your hands and compare them regarding the features in table 1.

Then assign the numbers of the spikes to right blank in the wheat pedigree (Figure 2).

Table 1: features of spikes 1 & 2

Figure 1: Wheat spike (D) and spikelet (E) with lemma (d), outer glume (h) and palea (v) (modified after Strasburger, E. et al.

2008. Lehrbuch der Botanik. Heidelberg: Spektrum Akademischer Verlag: 867)

English German

palea Vorspelze

lemma Deckspelze

outer glume Hüllspelze

spike Ähre

spikelet Ährchen

spikes grains

shattering non-shattering hulled free-threshing

1

2

Material: spikes labelled 1 and 2

2

2) Optional task: Would the modern wheat forms also survive in nature without human

intervention? Give reasons.

Vocabulary list

English German

agriculture Landwirtschaft

allopolyploidy Allopolyploidie

ancestor Vorfahre

artificial selection Künstliche Selektion

brittle brüchig

cumbersome mühsam

(to) cultivate anbauen

(to) disperse sich verteilen, ausbreiten

durum wheat Hartweizen

Emmer Emmer

food-shortage Nahrungsmittelknappheit

free-threshing freidreschend

Goatgrass Gänsefußgras

glume Spelze

grain Getreidekorn

(to) harvest ernten

hulled bespelzt

hybridization Kreuzung

lemma Deckspelze

Neolithic Era Neolithikum

outer glume Hüllspelze

palea Vorspelze

pedigree Stammbaum

polyploidy Polyploidie

ripe reif

shatter zerbrechen

soft wheat Weichweizen

sow aussäen

Spelt Dinkel

spike Ähre

spikelet Ährchen

Wild Einkorn Wildes Einkorn

Wild Emmer Wilder Emmer

Wild Spelt Wilder Spelzweizen

3

Figure 1: Wheat pedigree (modified after Saedler, Heinz. ヲヰヱヱく さけFヴWｷSヴWゲIｴWﾐSげ ｷﾐ SｷW Z┌ﾆ┌ﾐaデぎ H;ヴデ- ┌ﾐS WWｷIｴﾐ┘Wｷ┣Wﾐくざ WiS Begierig 1: 11)

Durum wheat

Wild

Einkorn

Wild

Spelt

Wild

Emmer Goatgrass

Spelt

Soft Wheat

shattering spikes

non-shattering spikes

hulledness

free-threshing

years BC

Neolithic Era

Extension: Polyploidy

Abnormal cell division during meiosis may lead to organisms containing more than two sets

of chromosomes. Hybridization may result in polyploids with chromosomes from different

species (alloploidy). Polyploidy is common in plants. Hexaploid soft wheat results from

hybridization of a tetraploid wheat form and a diploid wild grass.