Excerpt from On the Origin of Species (6th Edition) by Charles Darwin, Chapter 4 Summary on Natural Selection
The affinities of all beings of the same class have sometimes been represented
by a great tree. I believe this simile largely speaks the truth. The green and budding
twigs may represent existing species; and those produced during each former year
may represent the long succession of extinct species. At each period of growth all the
growing twigs have tried to branch out on all sides, and to overtop and kill the
surrounding twigs and branches, in the same manner as species and groups of species
have tried to overmaster other species in the great battle for life. The limbs divided
into great branches, and these into lesser and lesser branches, were themselves once,
when the tree was small, budding twigs; and this connexion of the former and
present buds by ramifying branches may well represent the classification of all extinct
and living species in groups subordinate to groups. Of the many twigs which
flourished when the tree was a mere bush, only two or three, now grown into great
branches, yet survive and bear all the other branches; so with the species which lived
during long-past geological periods, very few now have living and modified
descendants. From the first growth of the tree, many a limb and branch has decayed
and dropped off; and these lost branches of various sizes may represent those whole
orders, families, and genera which have now no living representatives, and which are
known to us only from having been found in a fossil state. As we here and there see a
thin straggling branch springing from a fork low down in a tree, and which by some
chance has been favoured and is still alive on its summit, so we occasionally see an
animal like the Ornithorhynchus or Lepidosiren, which in some small degree connects
by its affinities two large branches of life, and which has apparently been saved from
fatal competition by having inhabited a protected station. As buds give rise by growth
to fresh buds, and these, if vigorous, branch out and overtop on all sides many a
feebler branch, so by generation I believe it has been with the great Tree of Life,
which fills with its dead and broken branches the crust of the earth, and covers the
surface with its ever branching and beautiful ramifications.
Questions
1. As we read the passage together,
visualize Darwin’s explanation and
sketch your interpretation.
2. Why does Darwin use language such
as “I believe this simile largely speaks
the truth.”?
3. Which one of Darwin’s main ideas of
evolution relates to the phrase “great
battle for life”?
4. What organisms could be applied to
Darwin’s quote, “From the first growth
of the tree, many a limb and branch
has decayed and dropped off… which
are known to us only from having
been found in a fossil state.”?
5. What scientific term relates to
Darwin’s phrase, “saved from fatal
competition by having inhabited a
protected station.”?
6. Research: Darwin published the Origin
of Species in 1859. What discoveries
later supported Darwin’s theory?
Vocabulary
Ornithorhynchus- common name is the duck-billed platypus, semi-aquatic egg-laying mammal endemic to eastern Australia
Lepidosiren- common name is the South American lungfish
Origin of Species Instructors’ Guide
We will use this excerpt from the Origin of Species to introduce the teachers to the process of close
reading. The close reading process is used for complex texts. It requires additional time and therefore,
should NOT be used with every text, only complex text. The excerpt from the Chapter 4 Summary has a
text complexity appropriate for a student in college. (Lexile score- 1530). The process of close reading
involves reading the text multiple times, annotating, highlighting content and academic vocabulary, and
answering text dependent questions.
Procedure:
1. Cold Read- Instruct the participants to read the text on their own.
2. Read the passage together and highlight content and academic vocabulary such as:
a. Affinityi.
Common definition- A natural attraction, liking, or feeling of kinship.
ii.
Biology definition- A relationship or resemblance in structure between species that
suggests a common origin.
b. Simile- A figure of speech involving the comparison of one thing with another thing of a
different kind
c. Ornithorhynchus- common name is the duck-billed platypus, semi-aquatic egg-laying
mammal endemic to eastern Australia.
d. Lepidosiren- common name is the South American lungfish
3. After reading the passage aloud, instruct the participants to sketch their visualization of
Darwin’s ideas. Sketch can be done on the back of the excerpt page.
Note: When the participants finish, show them the sketches from Darwin’s Notebook B, diagram
from Origin, and the Tree of Life Web Project. See Appendix A. Also in PowerPoint.
4. Why does Darwin use language such as “I believe this simile largely speaks the truth.”
Note- Darwin lived during a time when the Old Earth and geological evolution was gaining
acceptance, but biological evolution was not. People still interpreted the Bible literally and
believed that biodiversity was due to a creator designing each organism individually. Tree
metaphor written by Darwin resembles the use of metaphors used by nineteenth-century
poets novelists including Dickens and Conrad.
Origin of Species Instructors’ Guide
5. Which one of Darwin’s main ideas of evolution relates to the phrase “great battle for life”?
Note- Darwin is referring to competition/struggle for existence
6. What organisms could be applied to Darwin’s quote, “From the first growth of the tree,
many a limb and branch has decayed and dropped off; and these lost branches of various
sizes may represent those whole orders, families, and genera which have now no living
representatives, and which are known to us only from having been found in a fossil state.”
Note- Answers will vary.
7. What scientific term relates to Darwin’s phrase, “saved from fatal competition by having
inhabited a protected station.”
Note: Darwin is referring to the specific niche that the platypus and lungfish occupy.
8. Darwin published The Origin of Species in 1859. What discoveries supported Darwin’s
theory?
Note: Darwin did not know about the laws of genetics, DNA, or mutations. This will most
likely require an extension activity that incorporates CCR.W.7, CCR.W.8, and CCR.W.9
Origin of Species Instructors’ Guide
Short and Sustained Research Projects:
Possible extension: Depending upon your time period, how did the work of other scientists
influence the development of Darwin’s theory? Or, how did Darwin’s theory influence the work
of other scientists?
Use the History of Evolutionary Thought section of the Understanding Evolution Web Site as a
resource. http://evolution.berkeley.edu/evolibrary/article/0_0_0/history_01. If you use another
Web site in addition to this page, be sure to cite your reference.
Standards Covered:
RST.11-12.7 Conduct short as well as sustained research projects to answer a question (including a selfgenerated question) or solve a problem; narrow or broaden the inquiry when appropriate; synthesize
multiple sources on the subject, demonstrating understanding of the subject under investigation.
RST.11-12.8 Gather relevant information from multiple authoritative print and digital sources, using
advanced searches effectively; assess the strengths and limitations of each source in terms of the
specific task, purpose, and audience; integrate information into the text selectively to maintain the flow
of ideas, avoiding plagiarism and overreliance on any one source and following a standard format for
citation.
RST.11-12.9 Draw evidence from informational texts to support analysis, reflection, and research.
Students or pairs of students will be assigned to research the contributions of the following
scientists.
Time Period: Pre-1800:
1.
2.
3.
4.
5.
6.
Comparative Anatomy: Andreas Vesalius
Observation and Natural Theology: William Harvey & William Paley
Fossils and the Birth of Paleontology: Nicholas Steno
Nested Hierarchies, the Order of Nature: Carolus Linnaeus
Old Earth, Ancient Life: Georges-Louis Leclerc, Comte de Buffon
The Ecology of Human Populations: Thomas Malthus
Time Period: 1800s
1.
2.
3.
4.
5.
6.
7.
8.
Extinctions: Georges Cuvier
Early Concepts of Evolution: Jean Baptiste Lamarck
Developmental Similarities: Karl von Baer
Biostratigraphy: William Smith
Uniformitarianism: Charles Lyell
Discrete Genes Are Inherited: Gregor Mendel
Natural Selection: Charles Darwin & Alfred Russel Wallace
Early Evolution and Development: Ernst Haeckel
Origin of Species Instructors’ Guide
9. Biogeography: Wallace and Wegener
10. Fossil Hominids, Human Evolution: Thomas Huxley & Eugene Dubois
11. Chromosomes, Mutation, and the Birth of Modern Genetics: Thomas Hunt Morgan
Time Period: 1900-Present
1.
2.
3.
4.
5.
6.
Random Mutations and Evolutionary Change: Ronald Fisher, JBS Haldane, & Sewall Wright
Starting "The Modern Synthesis": Theodosius Dobzhansky
Speciation: Ernst Mayr
DNA, the Language of Evolution: Francis Crick & James Watson
Radiometric Dating: Clair Patterson
Endosymbiosis: Lynn Margulis
7. Evolution and Development for the 21st Century: Stephen Jay Gould
8. Genetic Similarities: Wilson, Sarich, Sibley, & Ahlquist
Origin of Species Instructors’ Guide
Appendix A:
Once Darwin started thinking seriously about evolution,
he grasped its essentials with astonishing speed. Only a
month or so elapsed between the time he opened the
first full transmutation notebook, in about July 1837,
and the time he drew a crude—but unmistakable—
evolutionary tree. This drawing, with the most ancient
forms at the bottom and their descendants branching
off irregularly along the trunk, reveals that Darwin
understood all plants and animals are related. Above
his tree Darwin wrote firmly, "I think.
http://www.mnh.si.edu/exhibits/darwin/treeoflife.html
Darwin sketched a tree of life to
illustrate his idea of descent with
modification. It is the only illustration
in On the Origin of Species.
http://rutgervos.blogspot.com/2007/10/introduction.html
Origin of Species Instructors’ Guide
Modern interpretation of Tree of Life Web Projecthttp://tolweb.org/tree/home.pages/aboutoverview.html