hemmungspendel experiment

Versuch 

Ein Hemmungspendel ist ein mathematisches Pendel mit einem Anschlag, der die Fadenlänge auf einer Schwingungsseite verkürzt.

Beschreibung

VARIANTE A: Stativstange 1: Ausgangspunkt der Schwingung. Hier wird der Pendelkörper losgelassen. Stativstange 2: Hemmt die Bewegung des Pendels. Hier knickt der Faden ab. Stativstange 3: Liegt auf gleicher Höhe wie Stativstange 1. Der Pendelkörper schlägt trotz Hemmung dagegen. Ein kurzes Video (AVI-Datei) dieser Variante mit akustischem Anschlag ist im Ordner Dateien zu finden. Durch Reibung wird immer etwas Energie in Wärme umgewandelt. Damit der Anschlag an Stativstange 3 hörbar ist, muss diese etwas niedriger als Stativstange 1 angebracht werden. Daraus folgt, dass die Kugel in umgekehrter Richtung nicht an Stativstange 1 anschlagen kann, wenn sie bei Stativstange 3 losgelassen wird. VARIANTE B: Bei dieser Variante fehlen die Stativstangen 1 und 3. Dies hat den Vorteil, dass die Kugel zuerst ohne die Hemmung durch Stativstange 2 schwingen kann. Dann wird die Hemmung eingebracht und eine Zeitlupenaufnahme von mehreren Schwingungen gemacht (siehe Video).

• Modellversuche
• Versuche mit dem van de Graaff-Generator
• Villard-Greinacher-Schaltung
• Wechselstromwiderstand an RLC
• Magnetron-Versuche (12 cm Wellenlänge)
• Übersicht / Sitemap
• Drehbewegung und Kreisel
• Elastische Kräfte
• Potenzielle und kinetische Energie
• Stoßgesetze
• Geradlinige Bewegung, Kraft, Masse, Beschleunigung
• Kräfte im rotierenden System
• Messen und Messfehler
• Schwerpunkt und Gleichgewicht
• Täuschungen
• Mechanik der Flüssigkeiten
• Schwingungen und Wellen
• Thermodynamik
• Elektrizität und Magnetismus
• Elektromagnetismus, Schwingungen und Wellen
• Atom und Kernphysik
• Mechanik der festen Körper

• Übersicht / Sitemap |
• Mechanik der festen Körper |
• Mechanik der Flüssigkeiten |
• Schwingungen und Wellen |
• Thermodynamik |
• Elektrizität und Magnetismus |
• Elektromagnetismus, Schwingungen und Wellen |

Artikelaktionen

Start Footer

Benutzerspezifische werkzeuge.

Diese Webseite verwendet Cookies

Wir verwenden Cookies, um unsere Website optimal für Sie zu gestalten. Mit dem Bestätigen des Buttons "Akzeptieren" stimmen Sie der Verwendung von Cookies zu. Durch Anklicken der untenstehenden Checkboxen können Sie auswählen, welche Cookie-Kategorien Sie zulassen möchten. Durch Klicken auf die Schaltfläche "Mehr anzeigen" erhalten Sie eine Beschreibung jeder Kategorie. Weitere Informationen finden Sie in unserer Datenschutzerklärung .

Cookie-Details

Notwendige Cookies helfen, eine Website nutzbar zu machen, indem sie grundlegende Funktionen wie die Seitennavigation und den Zugang zu sicheren Bereichen der Website ermöglichen. Ohne diese Cookies kann die Website nicht ordnungsgemäß funktionieren.

• go to navigation go to navigation
• go to main content go to main content
• go to footer go to footer

Zeichenabstand:

Schriftgröße:

Word spacing:

• Französisch

Universität allgemein

• Zukunftsperspektiven der Universität Freiburg
• Veranstaltungen Universität allgemein
• University College Freiburg (UCF)
• Alumni Freiburg
• Lehrer*innenbildung
• Informationen zur Universität

Informationen zum Studium

• ERASMUS in Freiburg
• Student Speak
• Teacher Speak
• Welcome Day for international students
• ACT - Africa Centre for Transregional Research
• Bernstein Center Freiburg
• Biochemie und Molekularbiologie
• Spemann Graduiertenschule für Biologie (SGBM)
• Zentrum für biologische Signalstudien (bioss)

Centre for Security and Society

• European Lectures on Security and Society
• Die Samstags-Uni (2012)
• Sonstige Projekte
• Digitales Lehren und Lernen
• FMF - Freiburger Materialforschungszentrum
• Heideggers „Schwarze Hefte“ – Ideologieanfälligkeit der Intellektuellen
• Evolution - Karrieren eines wissenschaftlichen Paradigmas
• „Katastrophen“: 2. Interdisziplinäres FRIAS-Symposion
• Gastvorträge im FRIAS
• Lunch Lectures
• Freiburger Horizonte
• Hermann Staudinger Lectures
• Geowissenschaften

Geschichte, Gesellschaft, Politik

• Gender Studies
• Gesellschaft
• Osteuropakanal
• Ringvorlesung - Geschichte, Gesellschaft, Politik
• Islamwissenschaft
• Politikwissenschaft
• Geschichte der Astronomie
• Ostmitteleuropa zwischen den Weltkriegen, 1918-1939
• Die Donaumonarchie Österreich-Ungarn
• Das Zeitalter der Entdeckungen
• Reformation und Gegenreformation in Ostmitteleuropa
• Polen im 20. Jahrhundert
• Das Osmanische Reich und Europa
• Osteuropa im Mittelalter
• Der Erste Weltkrieg in Osteuropa
• Mittelalter- und Renaissanceforschung
• Hochschuldidaktik
• Innovationscampus Nachhaltigkeit (ICN)
• Mathematische Grundlagen
• Didaktisches Seminar im WS 2008/09 und im SoSe 2009
• Gauß-Vorlesung der DMV
• Palliative Care
• Prostatakrebs
• Medizinische Reha
• Diabetes Typ 2
• Chronisch-entzündliche Darmerkrankungen
• Brustkrebs bei Frauen
• Chronischer Schmerz
• Der Weg in die Reha
• Medienkulturwissenschaft
• Der Musikwissenschaftliche Podcast
• Historische Musikaufnahmen
• Konzerte und Musikproduktionen der Universität

Philosophie, Sprache, Literatur

• Frei sein, frei handeln - Freiheit zwischen theoretischer und praktischer Philosophie
• Theorien der Wahrheit, WS 2008/09
• Beweistheorien, SoSe 2009
• Was ist Philosophie? SoSe 2010
• Kontroversen in der Philosophie, WS 2010/11
• Logik und Metaphysik, SoSe 2011
• Voraussetzung und Vorurteil, WS 2011/12
• Paradigmenwechsel in der Philosophie? SoSe 2012
• Antike und mittelalterliche Philosophie. WS 12/13
• Nietzsche als Philosoph der Moderne
• Heidegger in der Moderne
• Heideggers „Schwarze Hefte“ im Kontext
• Bernhard Waldenfels-Archiv
• Was ist Zeit? Transdisziplinäre Annäherungen
• Husserl-Arbeitstage 2009
• Colloquium Phaenomenologicum
• Frankreich-Zentrum
• Universitätsbibliothek
• Vorlesungen
• Experimente
• Psychologie
• Freiburger Vorträge
• Völkerrecht und Rechtsvergleichung
• Reden und Vorträge - Recht

Religion und Theologie

• Rede des Monats - Religion und Theologie
• Der Diskurs der Theologie - Von Gott reden in Kultur und Geschichte
• Dies Academicus
• Freiburger Religionsgespräche
• School of Education FACE

Studium generale

• Samstags-Uni: Demokratie – Grundlagen und Herausforderungen
• Zwei Leitfiguren der Moderne - Immanuel Kant (*1724) und Franz Kafka (†1924)
• Einzelveranstaltungen
• Vortragsreihen
• Samstags-Uni: In vino veritas? Wein – Kultur – Wissen
• Samstags-Uni – Der Klimawandel
• Blicke auf Europa
• Bildung – heute
• Die digitale Revolution
• 70 Jahre Grundgesetz: Von der Verfassung unseres Gemeinwesens
• Der Dreißigjährige Krieg: Interdisziplinäre Perspektiven
• 500 Jahre Reformation: Luther und die Folgen (2017/18)
• Einführung in den Islam (2017)
• Nationalsozialismus in Freiburg (2016/17)
• Erinnerungsorte des Mittelalters am Oberrhein (2016)
• Der Isenheimer Altar – Werk und Wirkung (2015/16)
• Zwischenkriegszeit: Vom Kaiserreich zur Weimarer Republik (2015)
• Der Erste Weltkrieg im Spiegel der Künste (2014/15)
• Freiburg 2025: In welcher Stadt wollen wir leben? (2014)
• Das Freiburger Münster (2013/14)
• Neue Wege in der Medizin (2013)
• Religion – Wozu? Religion und Religionen in moderner Gesellschaft (2012/13)
• Freiheit und Sicherheit in der offenen Gesellschaft (2012)
• Alt und Jung (2011/12)
• Im "Internationalen Jahr der Wälder" 2011 zum Thema "Wald"
• Mythos in Antike und Gegenwart (2010/11)
• Samstags-Uni: „Resilienz“: Widerstandskräfte in Krisenzeiten
• Recht und sozio-ökonomische Wirlichkeit (2009)
• Zum Verhältnis von Kunst und Wirklichkeit (2008)
• Zur Geschichte der Freiburger Universität (2007)
• 175 Jahre Deutschlandlied
• Bioethik und die Dynamik der Natur
• Ethik in der Medizin
• Der Erste Weltkrieg am Oberrhein
• Freiburger Sommervorträge
• Freiburger Wintervorträge
• Grenzen der Ökonomisierung?
• Herausforderung „Corona“: Perspektiven der Wissenschaft
• Heinrich Böll 100
• Mittelalterbilder in der Moderne
• Navigare necesse est. Reiseliteratur von der Antike bis zur Gegenwart
• Neurowissenschaftliche Forschung – Wo stehen wir?
• Perspektiven der Hermeneutik
• Nietzsches Literaturen
• Welt-Sichten: Verständigungen über Kultur
• Neues aus der Kultur – und ihren Wissenschaften
• Einzelvorträge Studium generale
• Das Sinfonieorchester in der zeitgenössischen MusikKultur-Gesellschaft-SWR Sinfonieorchester
• Lange Nacht der Universität

Technik und Technologien

• Technologien und Prozesse (Zengerle, Wintersemester 2008)
• Mikrofluidik I - Effekte und Phänomene (Zengerle, Wintersemester 2008)
• Mikrofluidik II - Platforms (Zengerle, Wintersemester 2008)
• Informationen zum Studium an der TF
• BrainLinks-BrainTools
• Methodenmodul
• Vertiefungsmodul
• Praktikumsmodul
• Managementmodul
• Communication Systems II (Schneider, Wintersemester 2008)
• Communication Systems (Schneider, Sommersemester 2008)
• Informatik II (Ottmann, Sommersemester 2008)

Umwelt und Natürliche Ressourcen

• Cost of Food

Wirtschaft und Management

• Informationsaustausch Art. 27 DBA Deutschland-Schweiz und Steuerhinterziehungsbekämpfungsgesetz
• Gründen mit Geist - Vom Campus ins eigene Unternehmen
• Startinsland
• Ringvorlesung "Entrepreneurship – Wege in die berufliche Selbstständigkeit"
• Einführungs-VA
• Eigenangebote
• Zertifikate

A 41.3 Hemmungspendel-Energieerhaltung

0 favorites

Starten bei:

Laden Sie den QR-Code dieses Videos hier herunter oder öffnen Sie ihn in einem neuen Tab.

Eingebettet auf leerer Seite

Geben Sie nachfolgend die E-Mail-Adresse des Empfängers und einen Text zur Empfehlung ein.

• hochgeladen

Ein Pendel wird zum Schwingen gebracht. Die Pendelkugel erreicht stets das Niveau der Ausgangslage, wie auch die Schattenprojektion gegen die Tafel zeigt. Der Schwung des Pendels kann mit einer Querstrebe behindert werden, die Energie bleibt dennoch erhalten.

Weitere Informationen auf: https://www.experimente.physik.uni-freiburg.de

Arbeit, Energie und Leistung

Hemmungspendel.

Schwierigkeitsgrad: mittelschwere Aufgabe

Flexon spielt mit einem Pendel. Er lenkt es aus und stellt fest, dass es nach einer bestimmten Zeit fast wieder die Ausgangslage erreicht hat. Nun hält er - wie in der Animation in Abb. 1 gezeigt - einen Metallstift senkrecht zur Schwingungsebene an den Faden.

Kannst du in diesem Fall vorhersagen, wie hoch der Pendelkörper steigen wird? Begründe deine Antwort!

Hinweis: Man bezeichnet die Anordnung, bei der die reguläre Schwingung des Pendels durch ein Hindernis gestört wird als Hemmungspendel oder auch GALILEI-Pendel.

• Aufgabe drucken
• Lösung drucken
• Aufgabe + Lösung drucken

Ja, man kann vorhersagen, wie hoch das Pendel ausschlagen wird, da das Hindernis in der Schwingung keine Energie umwandelt (sondern lediglich die Pendellänge und damit auch die Schwingungsdauer verändert). Entsprechend der Energieerhaltung muss das Pendel natürlich auch auf der gehemmten Seite genau so hoch ausschlagen wie es auf der ungehemmten Seite ausschlägt. Das Pendel erreicht also auf beiden Seiten die gleiche Höhe.

Dies gilt zumindest dann, wenn der Stab, der die Schwingung hemmt, oberhalb des höchsten Punktes des Pendelkörpers in die Schwingung gehalten wird.

Grundwissen zu dieser Aufgabe

Vorherige aufgabe, nächste aufgabe, aus unseren projekten:.

Das Portal für den Chemieunterricht

Das Portal für den Wirtschaftsunterricht

Ideen für den MINT-Unterricht

Schülerstipendium für Jugendliche

Search form

• Experiments
• Anthropology
• Self-Esteem
• Social Anxiety

• Kids' Science Projects >

Pendulum Experiment

The Pendulum Experiment is an experiment about gravity. Pendulums (or pendula if we are being exact!) are a fascinating scientific phenomenon.

This article is a part of the guide:

• Kids' Science Projects
• Paper Towel
• Salt Water Egg
• Fruit Battery

Browse Full Outline

• 1 Kids' Science Projects
• 2 How to Conduct Science Experiments
• 3.1 Mold Bread
• 3.2 Popcorn
• 3.3 Salt Water Egg
• 3.4 Corrosiveness of Soda
• 3.5 Egg in a Bottle
• 3.6 Fruit Battery
• 4.1 Pendulum
• 4.2 Paper Towel
• 4.3 Paper Airplane
• 4.4 Charge a Light Bulb
• 4.5 Lifting Ice Cube
• 4.6 Magic Egg
• 4.7 Magic Jumping Coin
• 4.8 Invisible Ink
• 4.9 Making-a-Rainbow
• 4.10 Oil Spill
• 4.11 Balloon Rocket Car
• 4.12 Build an Electromagnet
• 4.13 Create a Heat Detector
• 4.14 Creating a Volcano
• 4.15 Home-Made Glue
• 4.16 Home-Made Stethoscope
• 4.17 Magic Balloon
• 4.18 Make a Matchbox Guitar
• 4.19 Make Your Own Slime
• 5.1 Heron’s Aeolipile
• 5.2 Make an Archimedes Screw
• 5.3 Build an Astrolabe
• 5.4 Archimedes Displacement
• 5.5 Make Heron’s Fountain
• 5.6 Create a Sundial

For many years they have been used for keeping time. If you pull back a pendulum and then let it go, the time it takes to swing over and then return back to its starting position is one period.

They follow some simple mathematical rules and we are going to find out how they work.

We are going to do a series of three experiments to see what effect changing things has on a pendulum.

Please note that this experiment is probably easier with more than one person.

Facts About Pendulums

Pendulums have been around for thousands of years. The ancient Chinese used the pendulum principle to try and help predict earthquakes.

Galileo Galilei was the first European to really study pendulums and he discovered that their regularity could be used for keeping time, leading to the first clocks

In 1656, the Dutch inventor and mathematician, Huygens, was the first man to successfully build an accurate clock.

What You Will Need for the Pendulum Experiment

A long piece of string, at least 1 meter long.

One piece of metal wire to bend into a hook.

Some nuts from a toolbox - they must all be the same weight and must fit onto the hook.

A large piece of paper to put behind the pendulum or a wall that nobody minds you drawing on.

A stopwatch.

Initial Setting Up the Pendulum Experiment

To do this experiment requires a little building work but nothing too complicated.

The pencil should be firmly taped to the top of the tabled, leaving about 4cm hanging over the edge.

Next make a loop in your string to fit on the end of the pencil but do not make it too tight fitting.

At the other end of your string tie your hook and slide one of the nuts onto the hook.

Put your piece of card flat behind the pendulum and you are ready to go.

Before performing the pendulum experiment , make sure that everything swings freely without sticking.

Experiment One - Changing the Weight

In this experiment we are going to find out what effect changing the mass on the end of the string makes

Take your string back about 40 - 50 cm. You must make a mark on the wall or your piece of paper to make sure that you let it go from the same place every time.

As you let it go, start the stop-watch, and count the number of oscillations in one minute

Repeat the experiment 5 times and calculate an average

Put another weight on the hook

Release the weight from exactly the same place. Calculate the period as before.

Repeat 5 times and average the results

Try the same procedure with after adding another weight

You may be surprised by your results!

Experiment Two - Changing the Angle

Go back to just one weight on the string

You have the results from the first mark in your last experiment so you can use these results again.

Now, take the string back only about 20cm and make a mark as before

Let go and count the number of periods for one minute

Repeat 5 times and then work out an average

Try exactly the same thing but now let go from 10cm.

What difference does the angle of swing make?

Experiment Three - Changing the Length of the String

You already have your results from the first experiment and can use these again.

Take the string of the pendulum and cut off about 20cm. If you are really organized, you can use another length of string from the same roll to make a shorter one.

Take back to the same angle and let it fly.

Take another 20cm off the string, replace and try again.

What effect does changing the length of the string have on a pendulum?

As you can see from your results, changing a few things on a pendulum can have some unexpected effects.

There are still more questions about pendulums. What makes them slow down and stop? How does a pendulum in a grandfather clock keep swinging for a long time?

Maybe your next experiment could answer some of these questions.

• Psychology 101
• Flags and Countries
• Capitals and Countries

Martyn Shuttleworth (Feb 25, 2008). Pendulum Experiment. Retrieved Sep 05, 2024 from Explorable.com: https://explorable.com/pendulum-experiment

You Are Allowed To Copy The Text

The text in this article is licensed under the Creative Commons-License Attribution 4.0 International (CC BY 4.0) .

This means you're free to copy, share and adapt any parts (or all) of the text in the article, as long as you give appropriate credit and provide a link/reference to this page.

That is it. You don't need our permission to copy the article; just include a link/reference back to this page. You can use it freely (with some kind of link), and we're also okay with people reprinting in publications like books, blogs, newsletters, course-material, papers, wikipedia and presentations (with clear attribution).

Want to stay up to date? Follow us!

Get all these articles in 1 guide.

Want the full version to study at home, take to school or just scribble on?

Whether you are an academic novice, or you simply want to brush up your skills, this book will take your academic writing skills to the next level.

Download electronic versions: - Epub for mobiles and tablets - For Kindle here - PDF version here

Save this course for later

Don't have time for it all now? No problem, save it as a course and come back to it later.

Footer bottom

• Privacy Policy

• Subscribe to our RSS Feed
• Like us on Facebook
• Follow us on Twitter

8.1 Mendel’s Experiments

Learning objectives.

• Explain the scientific reasons for the success of Mendel’s experimental work
• Describe the expected outcomes of monohybrid crosses involving dominant and recessive alleles

Johann Gregor Mendel (1822–1884) ( Figure 8.2 ) was a lifelong learner, teacher, scientist, and man of faith. As a young adult, he joined the Augustinian Abbey of St. Thomas in Brno in what is now the Czech Republic. Supported by the monastery, he taught physics, botany, and natural science courses at the secondary and university levels. In 1856, he began a decade-long research pursuit involving inheritance patterns in honeybees and plants, ultimately settling on pea plants as his primary model system (a system with convenient characteristics that is used to study a specific biological phenomenon to gain understanding to be applied to other systems). In 1865, Mendel presented the results of his experiments with nearly 30,000 pea plants to the local natural history society. He demonstrated that traits are transmitted faithfully from parents to offspring in specific patterns. In 1866, he published his work, Experiments in Plant Hybridization, 1 in the proceedings of the Natural History Society of Brünn. As stated earlier, in genetics, "parent" is often used to describe the individual organism(s) that contribute genetic material to an offspring, usually in the form of gamete cells.

Mendel’s work went virtually unnoticed by the scientific community, which incorrectly believed that the process of inheritance involved a blending of parental traits that produced an intermediate physical appearance in offspring. This hypothetical process appeared to be correct because of what we know now as continuous variation. Continuous variation is the range of small differences we see among individuals in a characteristic like human height. It does appear that offspring are a “blend” of their parents’ traits when we look at characteristics that exhibit continuous variation. Mendel worked instead with traits that show discontinuous variation . Discontinuous variation is the variation seen among individuals when each individual shows one of two—or a very few—easily distinguishable traits, such as violet or white flowers. Mendel’s choice of these kinds of traits allowed him to see experimentally that the traits were not blended in the offspring as would have been expected at the time, but that they were inherited as distinct traits. In 1868, Mendel became abbot of the monastery and exchanged his scientific pursuits for his pastoral duties. He was not recognized for his extraordinary scientific contributions during his lifetime; in fact, it was not until 1900 that his work was rediscovered, reproduced, and revitalized by scientists on the brink of discovering the chromosomal basis of heredity.

Mendel’s Crosses

Mendel’s seminal work was accomplished using the garden pea, Pisum sativum , to study inheritance. This species naturally self-fertilizes, meaning that pollen encounters ova within the same flower. Because every pea plant has both male reproductive organs and female reproductive organs, each plant produces both types of gametes required for reproduction—both pollen and ova. In plants, just as in animals, reproductive organs are classified by the size of the gametes produced. The organs producing the smaller pollen are called male reproductive organs, while the organs producing the larger ova are called female reproductive organs.

In garden peas, the flower petals remain sealed tightly until pollination is completed to prevent the pollination of other plants. The result is highly inbred, or “true-breeding,” pea plants. These are plants that always produce offspring that look like the parent. By experimenting with true-breeding pea plants, Mendel avoided the appearance of unexpected traits in offspring that might occur if the plants were not true-breeding. The garden pea also grows to maturity within one season, meaning that several generations could be evaluated over a relatively short time. Finally, large quantities of garden peas could be cultivated simultaneously, allowing Mendel to conclude that his results did not come about simply by chance.

Mendel performed hybridizations , which involve mating two true-breeding individuals that have different traits. In the pea, which is naturally self-pollinating, this is done by manually transferring pollen from the anther of a mature pea plant of one variety to the stigma of a separate mature pea plant of the second variety.

Plants used in first-generation crosses were called P, or parental generation, plants ( Figure 8.3 ). Mendel collected the seeds produced by the P plants that resulted from each cross and grew them the following season. These offspring were called the F 1 , or the first filial (filial = daughter or son), generation. Once Mendel examined the characteristics in the F 1 generation of plants, he allowed them to self-fertilize naturally. He then collected and grew the seeds from the F 1 plants to produce the F 2 , or second filial, generation. Mendel’s experiments extended beyond the F 2 generation to the F 3 generation, F 4 generation, and so on, but it was the ratio of characteristics in the P, F 1 , and F 2 generations that were the most intriguing and became the basis of Mendel’s postulates.

Garden Pea Characteristics Revealed the Basics of Heredity

In his 1865 publication, Mendel reported the results of his crosses involving seven different characteristics, each with two contrasting traits. A trait is defined as a variation in the physical appearance of a heritable characteristic. The characteristics included plant height, seed texture, seed color, flower color, pea-pod size, pea-pod color, and flower position. For the characteristic of flower color, for example, the two contrasting traits were white versus violet. To fully examine each characteristic, Mendel generated large numbers of F 1 and F 2 plants and reported results from thousands of F 2 plants.

What results did Mendel find in his crosses for flower color? First, Mendel confirmed that he was using plants that bred true for white or violet flower color. Irrespective of the number of generations that Mendel examined, all self-crossed offspring of parents with white flowers had white flowers, and all self-crossed offspring of parents with violet flowers had violet flowers. In addition, Mendel confirmed that, other than flower color, the pea plants were physically identical. This was an important check to make sure that the two varieties of pea plants only differed with respect to one trait, flower color.

Once these validations were complete, Mendel applied the pollen from a plant with violet flowers to the stigma of a plant with white flowers. After gathering and sowing the seeds that resulted from this cross, Mendel found that 100 percent of the F 1 hybrid generation had violet flowers. Conventional wisdom at that time would have predicted the hybrid flowers to be pale violet or for hybrid plants to have equal numbers of white and violet flowers. In other words, the contrasting parental traits were expected to blend in the offspring. Instead, Mendel’s results demonstrated that the white flower trait had completely disappeared in the F 1 generation.

Importantly, Mendel did not stop his experimentation there. He allowed the F 1 plants to self-fertilize and found that 705 plants in the F 2 generation had violet flowers and 224 had white flowers. This was a ratio of 3.15 violet flowers to one white flower, or approximately 3:1. Mendel performed an additional experiment to ascertain differences in inheritance of traits carried in the pollen versus the ovum. When Mendel transferred pollen from a plant with violet flowers to fertilize the ova of a plant with white flowers and vice versa, he obtained approximately the same ratio irrespective of which gamete contributed which trait. This is called a reciprocal cross —a paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross. For the other six characteristics that Mendel examined, the F 1 and F 2 generations behaved in the same way that they behaved for flower color. One of the two traits would disappear completely from the F 1 generation, only to reappear in the F 2 generation at a ratio of roughly 3:1 ( Figure 8.4 ).

Upon compiling his results for many thousands of plants, Mendel concluded that the characteristics could be divided into expressed and latent traits. He called these dominant and recessive traits, respectively. Dominant traits are those that are inherited unchanged in a hybridization. Recessive traits become latent, or disappear in the offspring of a hybridization. The recessive trait does, however, reappear in the progeny of the hybrid offspring. An example of a dominant trait is the violet-colored flower trait. For this same characteristic (flower color), white-colored flowers are a recessive trait. The fact that the recessive trait reappeared in the F 2 generation meant that the traits remained separate (and were not blended) in the plants of the F 1 generation. Mendel proposed that this was because the plants possessed two copies of the trait for the flower-color characteristic, and that each parent transmitted one of their two copies to their offspring, where they came together. Moreover, the physical observation of a dominant trait could mean that the genetic composition of the organism included two dominant versions of the characteristic, or that it included one dominant and one recessive version. Conversely, the observation of a recessive trait meant that the organism lacked any dominant versions of this characteristic.

• 1 Johann Gregor Mendel, “Versuche über Pflanzenhybriden.” Verhandlungen des naturforschenden Vereines in Brünn , Bd. IV für das Jahr, 1865 Abhandlungen (1866):3–47. [for English translation, see http://www.mendelweb.org/Mendel.plain.html]

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Access for free at https://openstax.org/books/concepts-biology/pages/1-introduction

• Authors: Samantha Fowler, Rebecca Roush, James Wise
• Publisher/website: OpenStax
• Book title: Concepts of Biology
• Publication date: Apr 25, 2013
• Location: Houston, Texas
• Book URL: https://openstax.org/books/concepts-biology/pages/1-introduction
• Section URL: https://openstax.org/books/concepts-biology/pages/8-1-mendels-experiments

© Jul 10, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.

You are using an outdated browser. Please upgrade your browser to improve your experience and security.

Enhanced Page Navigation

• Hans Spemann - Nobel Lecture: The Organizer-Effect in Embryonic Development

Hans Spemann

Nobel lecture.

Nobel Lecture, December 12, 1935

The Organizer-Effect in Embryonic Development

The experiments which finally led to the discovery of the phenomena which are now designated as “organizer-effect” were prompted by a question which actually goes back to the beginnings of developmental mechanics, indeed to the beginnings of the history of evolution in general. How does that harmonious interlocking of separate processes come about which makes up the complete process of development? Do they go on side by side independently of each other (by “self-differentiation”, Roux), but from the very beginning so in equilibrium that they form the highly complicated end product of the complete organism, or is their influence on each other one of mutual stimulation, advancement or limitation?

These questions, various answers to which constitute the theories of preformation or epigenesis, were lifted out of the realm of speculation up into that of an exact science when first Wilhelm Roux and then Hans Driesch used experimental methods in their research into development. The first experiments consisted in separating the individual parts of the embryo from each other and culturing them in isolation. This would show what each part was capable of by itself, while at the same time showing how far the developmental processes depending on them were dependent on or independent of each other.

In this way Roux was able after taking a frog’s egg, pricking and destroying one of its two blastomeres, to obtain half an embryo from the other. Driesch, on the other hand, took a sea-urchin’s egg, separated one segmental cell from the other and obtained a smaller but complete embryo. Further experiments showed that the differing results depended not on the material but on the method. The completely isolated segmental cell which has been reduced by half can grow into a whole in the case not only of the sea-urchin’s egg, but also of amphibian’s egg. This growth is inhibited if the dead cell is left attached; when this happens, the cell grows in accordance with its original determination, forming, first at least, half an embryo.

Even in those early days of research into developmental mechanics a second method of enquiry into this same question was discovered – that of “embryonic transplantation”. Gustav Born observed that portions of young larval amphibians united if their freshly cut edges happened to come into contact with each other. He followed up this phenomenon and found that the individual portions were capable of self-differentiation to an astonishing degree.

It was from these premises that I began my experiments. They were all carried out on young amphibian embryos, mostly those of the common striped newt ( Triton taeniatus ). To make these experiments intelligible to the non-specialist it will be necessary in the first place to describe the main features in the normal development of these eggs.

Development begins immediately after fertilization, with a fairly protracted period of cell division which is called segmentation on account of the furrowing which appears on the surface. By the formation of an inner cavity or blastocoele, the blastocyst or blastula comes into being. Its lower, vegetative half (the thick floor of the blastocyst) consists of large cells rich in yolk, while the upper, animal half (the thin roof) is made up of numerous small cells poorer in yolk. Between the two is the marginal zone – a ring of medium-sized cells.

Next begins a very complicated and in many ways puzzling process: the so-called gastrulation. The end result of it is that all the material of the marginal zone and of the vegetative half of the blastula becomes invaginated and is thus covered over by animal material. Then along the line of invagination, i.e. the primitive orifice or blastopore, runs the outer layer of cells or ectoderm into the two invaginated layers, the mesoderm (originating from the marginal zone), and entoderm (corresponding to the vegetative half of the blastula, rich in yolk).

With this the primordia of the most important organs, the skin and central nervous system, vertebral column and musculature, gut and body cavity have in the main achieved their final dispositions. Their visible differentiation occupies the next phase of development.

The primordium of the central nervous system originates in the ectoderm of the dorsal surface, starting from the blastopore and coming forward as a thickened plate shaped like a shield with its anterior half broader than its posterior. This is the neural plate, and its lateral margins rise up as the neural folds. The neural folds are brought closer to each other and fused together so that the neural plate becomes a tube – the neural tube. This becomes separated from the epidermis and sinks below the surface. Its front end, which is thicker and originated in the broader anterior part of the neural plate will become brain; its thinner posterior part will become spinal cord. The neural plate lies over mesoderm. When the plate forms the neural tube, separates off and sinks below the surface, the mesoderm divides into five longitudinal strips lying side by side. The median strip is destined to be the axial skeleton or notochord. To the right and left of it is a row of mesodermal blocks or somites. These in turn are flanked on either side by the lateral plates from which arises the primordium of the coelum.

Finally, the entoderm first forms a broad open gutter, which is shaped like a trough. Its margins then bend inward towards the middle, and, along the mid-line – that is, just beneath the notochord – it completes the intestinal tube.

All these processes which, given a favourable temperature, go forward surprisingly quickly depend essentially not on the production of new material from the embryo substance but on the rearrangement of what is already there. It is therefore possible, and W. Vogt did this to perfection by means of staining, to show in the blastula or early gastrula, as it were, a topography of the rudiments of the presumptive organs.

In the face of this sort of topographical map we are again confronted with the question whether there is a real diversity in these parts which corresponds to the pattern of the presumptive rudiments in the early gastrula; whether they are more or less predestined, i.e. “determined”, for their subsequent fate or whether they are still indifferent and do not have their ultimate determination impressed on them until later.

The first answer to this question was given by experiments in isolation. Thus, if the bisection is not made as early as between the two cells after the first segmentation but later, even at the blastula stage, or at that of the very young gastrula, you can still get twins. So up to this stage the cell material must still be to a large degree indifferent and capable of being used for various purposes in constructing the body. This becomes especially clear when the bisection is made in such a way that it separates the ventral half of the embryo from the dorsal half. Even then the latter half can develop into a miniature embryo of normal proportions. Here the new allocation of the material becomes perfectly clear. According to the evidence of our topographical map, the dorsal half contains almost all the material for the neural plate, i.e. much too much for a half-sized embryo; on the other hand, it lacks all of the presumptive epidermis. This latter must therefore be made good by material from the former.

Now if presumptive neural plate and presumptive epidermis are interchangeable, they must therefore also be interchangeable without prejudicing further normal development. Embryonic transplantation at this early stage must therefore produce different consequences than it would if performed in the later stages in which Gustav Born experimented.

It was on these thoughts and on the development of a way to facilitate the manipulation of these uncommonly fragile young embryos and operation upon them that the success of the new experiments rested.

The first experiment consisted in exchanging a portion of presumptive epidermis and neural plate between two embryos of the same age, each being at the beginning of gastrulation. The grafts took so smoothly and development proceeded so normally that their margins left no trace except that the grafted tissue itself was distinguishable for a while by means of its natural pigmentation, or by artificial vital staining. From this it was obvious hat, as we had expected, the portions were interchansable – that is to say, presumptive epidermis could become neural plate and presumptive neural plate could become epidermis.

From this we can infer not only the very indifferent nature of the cells at this early stage of development; the result allows the much more important conclusion that the transplanted portion must in its new environment be subjected to some kind of influence which determines its subsequent development.

It is here that the analytical superiority of this experiment is shown over the previous ones, whereby use was made of the regulation power of the embryo. For it was now possible to examine all the parts of the embryo separately for their active and reactive induction capacity, and also to vary the age and species of the implant with great latitude.

At the same time this opens important fresh possibilities: first of all in the matter of procedures. The interchangeability may be undertaken not only between embryos of the same species but also between those of different species, e.g. between embryos of Triton taeniatus which have a fair amount of pigmentation and those of Triton cristatus which have little or none. This allows us to distinguish the implant more or less clearly for a very long time even in sections and often to define its limits in terms of its cells. Let me describe a case of this kind in more detail.

A portion of presumptive neural plate was removed from an embryo Triton taeniatus at the beginning of gastrulation and exchanged with a portion of presumptive epidermis from a Triton cristatus embryo of the same age. The embryo in which the host was taeniatus later showed anteriorly and to the left in the neutral plate a smoothly grafted oblong area of white cristatus tissue which developed further into parts of the brain and eye. The other embryo with cristatus as the host showed on the right-hand side in the epidermis of the gill area a long streak of dark taeniatus tissue which developed further as epidermis and formed the covering of the outer gills. Since the portions have been exchanged, and since one portion is now settled where the other came from, we can see at once from sections that brain substance has come from presumptive epidermis, and epidermis has come from presumptive brain substance.

Because the implant in this “heteroplastic” transplantation remains distinguishable for a fairly long time it is possible to test the interchangeability of those parts of the embryo which develop inwards during gastrulation. We can, for example, establish whether the exchange is feasible not only as between one and the same layer of cells but also as between two different layers.

By and large this is in fact the case. So O. Mangold was able to show that mesodermal organs such as notochord, somites and pronephric ducts could arise from presumptive ectoderm by suitable transplantation at the beginning of gastrulation.

Now, when random samples were taken from the whole surface of the gastrula and transplanted in this way in an indifferent place it became apparent that a limited area, namely the region of the upper and lateral blastopore lip did not conform. A portion of this kind, transplanted in an indifferent place in another embryo of the same age did not develop according to its new environment but rather persisted in the course previously entered upon and constrained its environment to follow it. It invaginates altogether as if it were still in its old place, builds up part of the axial organs and completes itself out of the mesodermal environment. Above all, it induces in the overlying ectoderm a neural plate which closes to a tube, in favourable cases bulges out into optical vesicles and adds lenses and auditory vesicles.

First carried out at my instigation by Hilde Mangold, this experiment shows, therefore, that there is an area in the embryo whose parts, when transplanted into an indifferent part of another embryo, there organize the primordia for a secondary embryo. These parts were therefore given the name of “organizers” and the region of the embryos in which they are gathered together at the beginning of gastrulation was called the “centre of organization”. H. Bautzmann has defined the limits of this area by systematic probing outwards and has found that it coincides more or less with the area of the presumptive notochord-mesoderm which invaginates later.

From these two facts – the development of an indifferent piece in conformity with its location and the inductive effect of an organizer – several series of experiments proceeded, connected with obvious questions. We will just touch on a few of them.

Since at first the organizer becomes invaginated, that is, completes the gastrulation it has begun, so that material in the neighbourhood can be included in the process, one might suppose that it is this process itself which causes further determination of the parts it has affected. But this is, to say the least, extremely unlikely, because the induction of neural plate takes place even though it has not itself been invaginated. This can be proved by a method which is highly significant for the whole progress of research. That is to say, those parts of the embryo which are being examined for their inductive capacity can be made to bypass the activte invagination and can be made effective by inserting them in the blastocoele through a small slit in the roof of the blastula or young gastrula which quickly heals over. The gastrulation does not suffer any essential disturbance from this and while it goes on, the blastocoele disappears and the piece we are examining comes to lie directly under the ectoderm and there shows what it is capable of. Thus a portion of the upper marginal zone of the blastula or early gastrula, or else a piece of the roof of the archenteron of the mature gastrula was planted in the blastocoele of a young gastrula and so brought beneath the ectoderm from the beginning; it was demonstrated that these portions were able to induce neural plate.

Now, these methods made it also possible to examine for their inductive capacity pieces which could not be embodied in the host embryo by any other means, either because they differed too much in age and origin or else because they were no longer living, or even not of living origin. We will have a look at these experiments next.

It had already been demonstrated in my early experiments that host and donor did not need to be exactly the same age in order to be able to work together. It was O. Mangold in particular who followed up this question and made the important discovery that the inductive reaction capacity is strictly limited in time while the inductive action capacity remains for a long time, far beyond the stage necessary for normal development.

This is true not only, as H. Bautzmann showed, for the notochord which normally induces in the earlier stages, but strangely enough also for a portion of embryo in which there would otherwise be no question if this kind of induction, viz. the neural plate. Both O. Mangold and I found simultaneously but independently, and starting from different lines of enquiry, that it can induce after transplantation. To this, O. Mangold added the important statement that the inductive capacity of this tissue persists into late stages, until there is a functioning brain in the hatched out larva.

Associated with this is the question whether and how far the inductive influence is specific in nature. Also, and this is connected with the other question, what role the action and reaction system plays in bringing about the highly complicated product of development. I had already expressed the opinion earlier that the inductive stimulus does not prescribe the specific character but releases that already inherent in the reaction system. The inductive potential already adduced of parts which have far exceeded the stage of observed normal effectiveness also points in the same direction. Still more is this true of the more recent experiments by Holtfreter which prove the extensive diffusion of factors which are able to induce a neural plate in the ectoderm of the young gastrula. So pretty well the whole animal kingdom from tapeworms to human beings was examined by the implantation method and shown to be capable of induction.

However, this does not only make obvious the largely unspecific character of the inducting agent; it also seems probable that it is chemical in nature. It was always thought to be so from the beginning. To make quite sure, experiments had to be made in which the inductor had been destroyed in various ways – by desiccation, freezing, or boiling. We got no clearly positive result from these first experiments; not until later similar ones by Holtfreter. It became apparent that this kind of treatment did not destroy the capacity of the inductors and, further, quite paradoxically, that this can in fact call forth such capacity in non-inductors.

The first experiment with a chemically treated inductor was carried out by Else Wehmeier and proved that an inductor immersed in 96% alcohol for 3f minutes did not lose its capacity.

After this, the chemical analysis was tackled in various quarters: in Germany by F. G. Fischer and E. Wehmeier, later with H. Lehmann, L. Jühling, and K. Hultzsch; in England by J. Needham, D. M. Needham, and C. H. Waddington. From the large number of separate results which still seem to be coming in I should like to draw attention to one only which is of the utmost importance in this connection. Chemically simple substances as, for example, synthetic oleic acid can nevertheless induce a complicated and in a certain sense complete structure such as a neural plate which will close over into a neural tube. Again, that would therefore indicate, as do some of the results from abnormal inductors, that most of the complication is based in the structure of the reaction system, and that the inductor has only a triggering and in some circumstances directing effect. Whether and, if so, how far and in what way such “unorganized inductors” (for it would be a contradiction in terms to speak here of “organizers”) determine the direction is at the moment one of the most interesting but also most difficult questions.

But this broaches a new complex of questions which goes right back to the first induction experiments. It had already turned out in Hilde Mangold’s experiments that the induced embryonic primordia were in the main arranged in the same direction as the primary ones and on a level with them. This seemed to emerge either from a general structural plan of the embryo or else from an influence of the primary embryonic primordia.

To investigate the former phenomenon, the similarity of direction of the constituents of the two embryos, two different experiments were set up. Upper blastopore lip still engaged in invagination was implanted in a different orientation in relation to the host embryo – crosswise and opposite to the orientation of the later primary primordia. With crosswise implantation it was shown that the invaginating cells of the graft were carried along by the gastrulating movements of the host and that thus the substratum was laid down along the long axis of the embryo. With opposite implantation the cells of the graft migrating against the stream get jammed but are not deflected. A controlling structure of the embryo, therefore, only works in so far as it determines the direction of the gastrulation movements both of the host embryo and the graft. It becomes even more obvious when a piece of the roof of the archenteron is planted in the blastocoele. The graft does not lie fixed in the cell formation of the host embryo so it can rather keep its original position and the induced secondary embryo primordia can be either crosswise or entirely opposite to those of the primary.

Of even greater interest, perhaps, is the result of the experiments which were to explain how the secondary primordia of the embryo were on the same level. For example, it can be seen that the auditory vesicles of both lie in nearly the same cross section of the embryo. In order to find out the cause of this regional determination or at least to establish its position the implantation was varied in two ways. To understand this we must remember one simple fact about development. In the course of gastrulation the invaginating material is rolled inwards around the upper lip of the blastopore. Thus, the material first invaginated lies farthest towards the front underneath the subsequent brain, while material invaginating later underlies the future spinal cord. Now it could be that the substratum of the head also determines the brain character of the anterior end of the neural plate (“head-organizer”) and the substratum of the trunk area determines the character of the spinal cord (“trunk-organizer”). In order to test this, a portion of upper blastopore lip at the beginning of gastrulation (head-organizer) and one from an advanced and mature gastrula (trunk-organizer) were transplanted in the same place in an early gastrula, i.e. at the site where the lower blastopore lip would later develop; this was done also at different sites – in the head and trunk areas. It was shown that in fact something like a head- and trunk-organizer does exist, since the former is able to induce a brain also in the trunk region. It was shown moreover that the level in the embryo at which the induction takes place co-determines its nature, since at the head level even a trunk-organizer can induce a brain.

We have already indicated above that this last could have two different reasons. It could be that the disposition for building the head surrounds the whole embryo at head level in a broad circular band. But it could equally well be that a regional differentiating influence is exerted by the primary embryo primordia which co-determines the shape of the secondary embryo. In the region of the primary brain, respectively its primordia, there would be a “brain area” in which neural substance which had been stimulated by induction would develop into brain.

On the basis of definite facts established by experiment, Holtfreter has decided against the first and in favour of the second possibility. Moreover he has in addition discovered some more extremely interesting examples of these “embryonic areas”. As we have seen, inducing tissues retain their induction capacity for a long time, and far beyond the stage of development required in the normal course. That being so, in a normal-embryo neural substance would have to be induced afresh in the epidermis which lies over the neural tube or the somites, unless that tissue had already exceeded its ephemeral period of reaction capacity. We could therefore infer, what Holtfreter discovered in a different enquiry, that a young portion still capable of reaction would in fact behave differently in this site. And it really is true that in particles of ectoderm from early gastrula implanted superficially at different levels in older gastrula a great variety of inherent potencies is activated. It depends on the region, so that in an anterior area, brain with optic and aural vesicles is induced, while further back, notochord and pronephric ducts are induced, and further back still, little tails. That shows that even the older embryo is still riddled with “embryonic areas” which do not normally come to light but can be detected at any time by indicators rich in potencies.

These inductions between parts of different ages do not complete the embryo by replacing what has been taken away; they are not “complementary” (O. Mangold) as in the case of a graft of the same age from an exactly similar site. Rather do the induced parts develop according to site only in a general sense, through “autonomic” induction; they are produced in excess and have a certain independence (O. Mangold).

A still further series of questions and experiments arose out of the first induction experiments and we will just touch on these in conclusion. As said earlier the induction effect is also possible with heteroplastic transplantation, i.e. between embryos of different species. For example; presumptive brain of a Triton taeniatus embryo can be made into epidermis in the gill area of a Triton cristatus . But the outer gills covered by it will have taeniatus properties; that is to say, they will be similar not to those of the species which has caused their development (instead of that of brain) but will resemble that of the species from which the implant originates. Potencies are not transferred to the “gill area” of the host; it is merely that those potencies relevant to its location are awakened. And in heteroplastic transplantation these diverge somewhat from those of the host. If an exchange between samples of different genus or even between systematic groups remote from each other (xeno-plastic) were possible and followed by induction effects, very valuable conclusions could be expected.

In this respect there is another question that must be dealt with which cropped up during those first experiments: whether in fact the induced organ is laid down part for part or as a whole. From the example of the outer gills we were not able to answer the question, but we could do so from two other organs – the lens and the balancers.

In the Triton, as with most amphibia, the lens of the eye arises as a sequel to the optic cup and its size depends strictly on it. Thus, if the optic cup diminishes in size so does the lens. So it follows that the smaller eye of the Triton taeniatus has a smaller lens than the larger eye of Triton cristatus at the same stage of development. E. Rotmann now interchanged presumptive lens epidermis with presumptive ventral epidermis in each of the two species at the beginning of gastrulation. The lenses which are formed at a certainmoment thereafter follow the size and degree of development of the donor. This can be seen very clearly in the constricted lens primordia with early fibre development; but even quite early stages show lens growth in the epidermis which in one case is too large for the optic cup and in the other case too small. The lens potencies therefore react in the field that activates them not only qualitatively but also quantitatively in accordance with the heredity of the species to which they belong. The lens potencies are not stimulated by the optic cup to the extent within which, with its drawn-in retina layer, it comes into contact with the epidermis. Rather is the lens more or less put in hand as a whole with the epidermis.

The balancers behave in the same way in a further completely analogous experiment of Rotmann’s. In its structure and in its angle to the head it is similar to the species from which the transplanted ectoderm is derived and not to the other from which the induction has proceeded.

Added to this problem of uniformity according to species there is another in those cases of xenoplastic transplantation in which organs of different morphological significance are situated in the same region. This is so, for instance, when the ectoderm of the presumptive mouth region is exchanged between the embryos of Urodela and Anura. In the newt larva, lateral to the head and beneath the eyes are two balancers, while the tadpole has beneath the mouth near the ventral mid-line two lower suction cups. Moreover, the newt has real teeth in its mouth which both in origin and structure are comparable to our own teeth. The tadpole’s mouth, on the other hand, is furnished with horny jaws and little horny processes. These are quite different in origin and structure from real teeth and indeed have nothing to do with them morphologically. It has been an old dream of mine to substitute for the presumptive mouth region of a newt the foreign ectoderm which comes from a frog early in gastrulation, since I wanted to find out what kind of “armoury” the mouth would form then. This experiment has now been successfully carried out several times since then, and also the other way round. It was first performed at my instigation and in my Institute by O. Schottt, later by Holtfreter, O. Mangold, and E. Rotmann with results we expected but hardly dared hope for. In the mouth region of a Triton larva there arose from transplanted Anura ectoderm of the early gastrula, suction cups and horny jaws; in a tadpole, balancers arose from Urodela ectoderm. When the foreign implant was so narrow that it left the place of origin of the characteristic organs wholly or partly free, these could then themselves develop alongside.

After these results we can say with all certainty of the inducing stimulus that as regards what arises, it must be of a very special nature; but as to how it arises, it must be of a very general character. We have, however, no idea at all how the “mouth area” releases potencies of the “mouth structures”, even when they are of an entirely different species.

Nobel Prizes and laureates

Nobel prizes 2023.

Explore prizes and laureates