Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Unilineal evolution wikipedia , lookup
Population genetics wikipedia , lookup
Creation and evolution in public education wikipedia , lookup
Acceptance of evolution by religious groups wikipedia , lookup
Sympatric speciation wikipedia , lookup
Catholic Church and evolution wikipedia , lookup
Evidence of common descent wikipedia , lookup
The eclipse of Darwinism wikipedia , lookup
Hologenome theory of evolution wikipedia , lookup
Science 10th grade LEARNING UNIT How are the components of the world related? LEARNING OBJECT Do species evolve rhythmically or gradually? S/K Skill 1. Define the concept of “phyletic gradualism” Skill 2. Explain the basis of the process of speciatio. Skill 3. Analyze the theoretical foundations of mosaic (or modular) evolution. Skill 4. Clarify that evolution is a process occurring in the geological time scale (millions of years) Skill 5. Research into the theory of the common ancestor. Skill 6. Look into the contributions of Gould and Eldredge to the development of the theory of punctuated equilibrium. Skill 7. Compare the bases of gradualism and punctuationism. Skill 8. Use connectors to express consequence, cause-effect and comparison-contrast, as a tool to review studied topics. Language English Socio cultural context of the LO Curricular axis Colombia Standard competencies Explain biologic diversity as a consequence of environmental, genetic and dynamic-relationship changes inside an ecosystem. Background Knowledge DNA synthesis, Mendel´s laws, modern genetics, human ecology, hereditary laws. English Review topic Connectors for consequence, cause-effect and compare-contrast Vocabulary box Chromatids: One or two identical chromosomal strands into which a chromosome splits longitudinally preparatory to cell division. Living Surroundings Idle: Not working or active; unemployed; doing nothing. Lineage: The line of descendants of a particular ancestor; family. Polyploid: Having a chromosome number that is more than double the basic or haploid number. Vestige: A mark, trace, or visible evidence of something that is no longer present or in existence. Wisdom Teeth: The third molar on each side of the upper and lower jaw: the last teeth to erupt. NAME: ______________________________________________________________ GRADE: _____________________________________________________________ Objectives • To analyze the theory of punctuated equilibrium in the context of evolution of biologic species. • To explain how evolution occurs based on different theories and its implications for speciation, taking into account the theory of a common ancestor and the contributions done by Gould and Eldredge regarding gradualism and punctuationism. • To reflect on the effects of different evolutionary theories in the conception of the human being. • To give advice in a classroom conversation about studied topics. Introduction The human body has evolved for millions of years and during this period it has developed abilities that allow it to adapt to the environment. Some parts of the human being have deteriorated or degenerated until losing the original purpose they had, therefore, these organs or structures are not vital any longer, becoming useless, and are at risk of disappearing. Charles Darwin called these processes “vestiges” because they are evidence of evolution. A clear example of this are wisdom teeth, crucial for chewing branches or bones millions of years ago, but, nowadays, they are unnecessary due to changes in nutrition of humankind. The same situation occurs with the appendix, an idle organ used to digest cellulose when the dietary base of humans relied on plenty vegetable proteins. Similarly, the pinky finger in the feet gets smaller on every generation and there will come the time, in millions of years, when it will disappear completely. The only certain thing is that the only truly essential toe is the thumb because it helps to maintain the balance of the entire body. Additionally, hair was useful for humans to isolate cold, but it began regressing progressively to guarantee better temperature regulation. However, hair continued to grow on different parts of the body, such as eyebrows, to avoid sweat drip into the eyes and to express emotions, and in the beard as a factor in sexual selection. However, most of the hair that covers the human body does not have a specific function. Then, why do we change? How do we evolve? Why do some individuals do not present these characteristics, such as wisdom teeth? Where do you think these micro-changes will lead us? ACTIVITY 1 - SKILL 1: Define the concept of “phyletic gradualism” - SKILL 2: Explain the basis of the process of speciation. - SKILL 3: Analyze the theoretical foundations of mosaic (or modular) evolution. - SKILL 4: Clarify that evolution is a process occurring in the geological time scale (millions of years) INTRODUCTION According to Ayllón (2011): The evolutionary theory developed by Charles Darwin suggests that living creatures change with time, and different degrees of relationships appear between species; reason why Darwin proposes natural selection as the motor of evolutionary change, but only the fittest individuals are capable of producing offspring. Evolution is evidenced by fossil register and genetic kinship. Campo, (2013), states that: Living creatures came to be 4000 million years ago, as bacteria that multiplied and diversified into billions of species, which resulted in the generation of species with progressive complexity in the course of time. Thus, evolution is a fact that can be proven with evidentiary support, but the exact mechanism how it happens is not fully understood, because it is unclear if the formation of new species happens slowly and gradually or in sharp leaps. What is known, however, is that evolution is a continuous process of adaptation to the environment. For example, mankind has evolved as shown in the following timeline, which shows the physiological changes that helped them adapt to the environment. 4 million First Hominids. The oldest fossils found – belonging to the Australopithec us- are four million years old. They are not complete skeletons but isolated remains. 3,6 million New fossils have been found at Sterkfontein caves, in the outskirts of Johannesburg. The oldest skeleton. The remnants found in South Africa belong to the “Australopithec us Africanus” species. Around 1,20m in height and a brain slightly bigger than a chimpanzee’s. AUSTRALOPIT HECUS AUSTRALOPITH ECUS 2,5 million 1 million 150000 The first humans. The oldest vestiges of the Homo genre, characterized by a brain bigger than the Australopithe cus; they appeared around the same time than the first stone tools. Humankind expands. Although some scientists state that “Homo Erectus” appeared in Africa 1.8 million years ago, there are no concluding proofs beyond one million years ago. “Homo Sapiens”. According to most experts, the current species appears in Africa only 150000 years ago and then travels around the Earth. HOMO HABILUS HOMO ERECTUS HOMO SAPIENS ANAMENSIS AFRICANUS Retrieved from: Soy así por la ciencia, no por la moda: http://www.taringa.net/posts/cienciaeducacion/17186065/Soy-asi-por-la-ciencia-no-por-la-moda.html Different ways of evolution enable the appearance of new species, known as the “Compound of populations whose individuals are potentially capable of reproducing among them naturally and are isolated, reproductively, from other groups” being their offspring fertile. (Israel, 2013). However, starting from existing species, new lineages can appear, producing new species in a process called speciation. This process is defined as the cause that allows a determined species to generate a different population, reproductively isolated from the previous one, which gradually develops genetic differences, showing diversity. According to Abarca (2011), there are different speciation processes that can be classified as: - Geographic or allopatric speciation: This process occurs when a population with similar genetic characteristics founds itself isolated by a geographic accident, such as rivers, mountains or deserts, which leads to the formation of geographic races which in turn produce new species who do not exchange genes, evolving separately. . For example, species of rabbits were separated and isolated reproductively by the presence of a river. Modified from: Neodarwinismo, o la relación entre evolución y genética: http://b-logia20.blogspot.com.co/2015/02/neodarwinismo-o-la-relacion-entre.html - Sympatric speciation: This type of speciation refers to genetic changes in populations that inhabit one geographic region, but segregate into different species due to the appearance of diverse mechanisms of reproductive isolation. . For example, genetic changes in populations can isolate them in reproductive terms. - Parapatric or polyploid speciation: This type of speciation refers to an increase in the number of chromosomes in an organism of the population. This individual does not reproduce with other members of the group, but only with others that share its polyploidy, which is the heritable condition of possessing more than two complete sets of chromosomes. This phenomenon occurs most commonly in less evolved animals and vegetables. Modified from: Especiación en plantas: http://www.genomasur.com/a_evo/evo_43_p.htm Increase in the number of chromatids in the Anemone flower, separating the species reproductively. There are different theories regarding evolution. Some of them are: 1). Phyletic evolution, anagenesis or phyletic gradualism: According to Guammen (1996), “Refers to changes in species through soft and continuous processes in time. As a consequence, species do not exist as well defined units, but as groups in constant modification, presenting infinity of intermediate stages for each species, called links” As such, progressive evolution of species implies a change in the genetic frequency of the entire population and by processes of mutation, allows significant differentiation from a previous generation, creating a new species and rendering the former generation extinct. For this reason, Ermini (2011) states that “a species changes gradually with time, until becoming a species that looks and acts differently” Consequently, characteristics of phyletic gradualism can be summarized as: 1) New species are originated by the transformation of an entire previous population. 2) This transformation is slow and consistent. 3) The transformation affects a high percentage of the population, generally the entire group. 4) Finally, the transformation covers a vast part of the geographic distribution of the previous generation. Did you know? Evolution of fingers and teeth of horses fits inside the evolutionary theory of phyletic gradualism and can be followed through its ancestor Hyracotherium (also called Eohippus). A small mammal ranging in size between 20cn and 40cm tall, herbivore that lived during the Eocene, 55 million years ago, in North America, with four fingers in the forelimbs and three in the hind limbs, each one ending in a nail. Its changes were evidenced in the increase of its height up to 115cm and loss of fingers until becoming monodactyl, meaning with only one finger. Little by little, its only finger hardened until developing hooves to be able to run away from predators. Regarding its teeth, Merychippus developed dentures with high crowns, which enabled it, as opposed to Hyracotherium, to scavenge leafs and stumps in trees and shrubs. That is how Hyracotherium became extinct and genetic transformation opened the path for Equus, known as the current horse, as illustrated in the figure. [CITATION Bul11 \l 9226]. For example, evolution of fingers and teeth of horses, as shown in the following image: Retived from https://upload.wikimedia.org/wikipedia/commons/d/dd/Horseevolution.png 2). Punctuated equilibrium or punctuationism: Cachón & Barahona (2013), conceive speciation “as a quick transformation of peripheral populations, presenting long periods of stability, that appear punctuated, or interrupted, by brief moments of quick evolution, producing visible transformations and new species based on existing ones. This explains why the absence of intermediate steps in the fossil registry does not mean it is incomplete, but sometimes evolution advances quickly” This concept was suggested by Eldredge and Gould, two paleontologists of the United States of America, based on observations of fossils with few or null changes in each species found. Available fossil tests propose that several lineages seem to follow the same evolutionary pattern, called saltationism, which is a sudden change of a big magnitude, produced between one generation and the next, turning saltation as a mechanism of speciation. The extraordinary diversity of life is explained by the fact that species change and are divided by leaps, and not gradually. Retrieved from: Las bases genéticas de la evolución: http://cienciasteorias.blogspot.com.co/2011/07/evolucion-las-bases-geneticas-de-la.html In the previous image, the organisms that represent this model are cichlid African fish from Lake Victoria. This lake, which is less than 1 million years old, has around two hundred species of cichlid fish, of different sizes and shapes, adapted to the diverse habitats and nourishment types available in the lake. According to existent data, this compound of species evolved from one unique ancestor that existed only 200000 years ago. 3). Mosaic (or modular) evolution: Tarancón (2013) suggests that “certain structures possess a rate of evolution or modification greater than the rest of structures of the same individual. This is why these individuals may preserve structures from their ancestors but at the same time incorporate new ones. Thus, evolutionary changes do not necessarily affect the entire organism at once, but may vary the anatomy of some of its parts.” The occurrence of these types of changes is random, without defined direction or purpose, but always controlled by natural selection. Because there are different ways for an anatomic change to occur, more than one can appear simultaneously, adding the effects towards the final morphologic change. This results in an evolutionary pattern where all the characteristics of an organism evolve at the same rate. The pioneer of this theory is Gavin de Beer. [CITATION Riv07 \l 9226]. For example, the social, cultural, learning, physiological and neurological aspects were not linked when language started, but intellectual development and the ability to connect them in a unique system progressed, resulting in a more useful and effective communication mechanism without modifying the volume of the brain. Learning Activity: - SKILL 1: Define the concept of “phyletic gradualism” - SKILL 2: Explain the basis of the process of speciation. - SKILL 3: Analyze the theoretical foundations of mosaic (or modular) evolution. - SKILL 4: Clarify that evolution is a process occurring in the geological time scale (millions of years) SKILL 7: Compare the bases of gradualism and punctuationism. - SKILL 8: Use connectors to express consequence, cause-effect and comparisoncontrast, as a tool to review studied topics. The following exercises expect to establish relations between the concepts covered in the unit and mental construction developed by the students to explain, understand and interpret the process of evolution. 1. Look carefully for the following words in the Word Search. Once you finish, complete the paragraph explaining the process of evolution according to the period of time. Millions Long Environment Allopatric Soft Need Short Speciation Independent Continuous Adaptation Origin Geographic Evolution Population Change individuals Barriers Species Phyletic Time Vegetation Transformations Phyletic Gradualism Fill in the gaps: Life began 4.50 _______________ of years ago, and has since transformed and evolved in the course of ______________, thanks to a _____________ of ________________ to ____________ in the ____________ or the _______________. These changes are expressed in a ____________ or ___________ period of time, resulting in the ___________ of new __________________ which generate new ____________, that in turn, because of ____________ ________________ and genetic ______________ are separated, generating __________________. 2. Watch carefully the next video, and then define speciation and the basis of the process of speciation in one paragraph. Video: Especiación: https://www.youtube.com/watch?v=1hHlvvcAkzE ___________________________________________________________________________________ ___________________________________________________________________________________ ___________________________________________________________________________________ 3. According to the information developed so far in the unit, and considering the context of the following paragraph, explain the meaning of the underlined phrases. "Natural selection can happen only through preservation and accumulation of infinitely small modifications, each of them destined to preservation of life, the process of modification and production of a number of related forms must be slow and gradual, -a species originates at first two or three varieties, these begin to transform into species slowly, which, in turn, produce other species in equally slow steps”. “It is a very important consideration, because the periods during which these species have suffered modifications are extremely long to be measured in years, but are relatively short in comparison to periods in which species have remained without suffering any change at all” Retrieved from: García and others (2002). 3.1. “the process of modification and production of a number of related forms must be slow and gradual” 3.2. “species have suffered modifications” 4. Watch carefully the following video. Based on the information shown, organize the following sentences inside the table, so that similarities and differences between the concepts of gradualism and punctuationism are expressed. Video: Gradualism vs. Puntuacted Equilibrium: https://www.youtube.com/watch? v=qWUqQyVa5ts - Changes occur in long periods and are punctuated in time. - Changes occur in short periods and in leaps in time. - Produces small changes - Produces big changes. - Slow evolution - Quick evolution - There is evolution through time - Changes appear because of pressure in the environment - All organisms descend from a common ancestor . Gradualism Punctuationism Differences Similarities 5. Mosaic (or modular) evolution states that there are certain structures with a higher rate of evolution or modification than the rest of the structures of the same organism. Research at least three examples of any type of living organism on Earth, where mosaic evolution can be evidenced. Once you have identified the examples, choose the most relevant of the three and build a 3D model, as well as an oral presentation that must not exceed 5 minutes, in which you must analyze the theoretical bases of this type of evolution. Language practice In pairs, fill in the gaps using the appropriate connector from the box. Remember you can give advice to your classmate during the exercise using the expression “If I were you”, for example: Student A: I think the best answer for number 1 is… Student B: If I were you, I’d choose… Furthermore Consequently On the Contrary Consequently But 1. Charles Darwin suggests in the development of the theory of evolution that all organisms change in time ________maintain degrees of relationship among them. 2. There are different theories about the mechanism species use to evolve, __________ they all share the idea that all of them originated from already existing species 3. There are different types of speciation, such as geographic speciation, which occurs when a population of the same species is separated from another one by a geographic accident. They must evolve independently, and ___________ reproduce in isolation. 4. Among evolutionary theories, we can find phyletic evolution, presenting soft and continuous variations in populations through time._____________, species do not exist as well-defined units, ________ as groups in continuous modification.___________, the theory of punctuated equilibrium suggests that speciation occurs as quick transformations in peripheral populations. ____________, between one speciation event and the next we can find long periods of balance that appear punctuated (or interrupted) by brief periods of quick evolution. Did you know? Our ancestors had bigger jaws than current humans, which helped them to maintain a diet based on hard and raw roots, nuts and leaves. That is how wisdom teeth appeared, a third group of teeth which are believed to be an evolutionary answer to the nourishment habits of earlier humans. However, with time, maxillaries have progressively decreased but maintaining the same number of teeth, and that has become a problem, because the evolution of bones has not been simultaneous with the evolution of teeth (mosaic evolution), and since wisdom teeth are the last ones to appear, they do not have a proper place to do so, thus generating dental issues. It has been determined that only 10% of the current population does not possess wisdom teeth, creating a change in their physiology. Probably, after some time, no human being will have wisdom teeth, due to dietary changes. Therefore, are we still evolving? Abstract Charles Darwin suggests in the development of the theory of evolution that all organisms change in time but maintain degrees of relationship among them. According to this theory, only the fittest organisms can reproduce so that some adaptations to the environment are inherited to their descendants. This process is lengthy through time and happens in changing environments, resulting in diversification of species. There are different theories about the mechanism species use to evolve, but they all share the idea that all of them originated from already existing species. Understanding the concept of species as organisms capable of reproduction, who are reproductively isolated from others, and their offspring is fertile, is the basis to define speciation as the process when a population of a determined species makes room for a new one, reproductively isolated from the previous one, gathering genetic differences throughout time. There are different types of speciation, such as geographic speciation, which occurs when a population of the same species is separated from another one by a geographic accident. They must evolve independently, and consequently reproduce in isolation. Similarly, we can find sympatric speciation, which happens in species that diverge by means of reproductive isolation; and parapatric speciation, which increases polyploidy between individuals, isolating them reproductively and genetically. Among evolutionary theories, we can find phyletic evolution, presenting soft and continuous variations in populations through time. As a consequence, species do not exist as well-defined units, but as groups in continuous modification. Contrary to this idea, the theory of punctuated equilibrium suggests that speciation occurs as quick transformations in peripheral populations. Furthermore, between one speciation event and the next we can find long periods of balance that appear punctuated (or interrupted) by brief periods of quick evolution. A different line of thought is mosaic (or modular) evolution, which states that certain structures or modules that make part of living creatures possess a higher rate of evolution or modification than the rest of the structures of the same organism. These organisms may preserve the same structures as their ancestors but can also incorporate new ones. However, evolutionary changes do not necessarily affect the entirety of the organism at once; they can vary the anatomy of only specific parts of the living creature. Homework 1. Starting from a single predecessor organism, life diversified in the multiple forms that inhabit present day Earth; this is known as the common ancestor. Based on the previous statement, in groups of 4 students, investigate how, when, where and what represents the common ancestor of all living creatures, as well as how this organism evolved until now. Once you have the results of your research, create a timeline showing your results and share them in a presentation no longer than 10 minutes. 2. In pairs, investigate how the contributions of Gould and Eldredge helped the development of punctuated equilibrium theory, and present at least two examples. Once you are finished with your inquiry design a story to evidence these events and share it with the rest of your classmates. Evaluation Based on the topics covered in the unit, the evaluation will assess the understanding of the materials developed so far. 1. Who proposed the theory of evolution of species? a) Charles Darwin b) Niles Eldredge c) S. J. Gould d) Alfred Russel Wallace. 2. Which theory suggests that organisms change slowly and gradually? a) Gradualism b) Punctuated Equilibrium c) Neutralism d) Synthetic Theory 3. Which theory suggests that the origin of new species (speciation) can occur in short or immediate geological periods, through mechanisms like polyploidy in plants? a) Gradualist Theory b) Punctuated Equilibrium c) Neutralism d) Gradualism 4. Which theory suggests that “most species can stay millions of years with morphology relatively similar and only experiment slight fluctuations with no apparent direction or purpose? a) Natural Selection b) Punctuated Equilibrium c) Neutralism d) Gradualism e) Synthetic Theory 5. Which are the vestigial organs in human beings? a). Incisor teeth and molars b). Third molars and liver c). Liver and appendix d). Wisdom teeth and appendix 6. Watch closely the following figure and complete the sentence: A common ancestor is __________________________________. The one who originated dogs and cats was ___________________, through a type of evolution called ____________________, these species diversified the most in the _________________ era. Bibliography Abarca, B. (2011). Biología 26. Retrieved on March 28th, 2016, from http://biologia26.blogspot.com.co/2011/12/especiacion.html Ayllón, J. (2011l). La evolución del evolucionismo. Revista cultural y de cuestiones actuales de la Universidad de Navarra (p. 667). Bulfon, G. (2011). Taringa.net. Retrieved on March 28th, 2016, from http://www.taringa.net/posts/info/7218006/Evolucion-Del-Caballo-Equus-feruscaballus.html Cachón, V., & Barahona, A. (2013). Facultad de Ciencias UNAM. Retrieved on Match 28th, 2016, from 142-140-1-PB%20(3).pdf Campo, D. (2013). D Ciencia. Retrieved Marzo 28, 2016, from http://dciencia.es/que-es-la-evolucion-conceptos/ Ermini, J. (2011). Taringa.net. Retrieved on March 28th, 2016, from http://www.taringa.net/post/ciencia-educacion/9205456/Tipos-de-evolucion-casosy-medidas-de-evolucion.html Evolución y Biología Evolutiva. (2011). Retrieved on March 28th, 2016, from https://otrabiologia.files.wordpress.com/2011/06/evolucion.pdf García, P., Montellano, M., Quiroz, S., Sour, F., Ceballos, S., & Chávez, L. (2002). Paleobiología. México: Facultad de Ciencias, UNAM. Retrieved from http://www.libros.unam.mx/digital/V5/36.pdf#page=241 Guammen, D. (1996). Todo Sobre la Evolución. Retrieved on March 28th, 2016, from http://todosobrelaevolucion.org.mx/capsula.php?id=50 Israel. (2013). La Evolución sencilla. Retrieved on March 28th, 2016, from https://laevolucionsencilla.wordpress.com/2013/02/23/capitulo-1-bisprofundizamos-en-la-evolucion-especiacion-como-resultado-de-la-evolucion/ Malena. (2009). El teoguillo.com. Retrieved on March 28th, 2016, from http://elteologillo.com/2016/02/25/la-teoria-de-los-equilibrios-puntuados/ Martínez, C. (2003). El Clarín. Retrieved on March 28th, 2016, from http://edant.clarin.com/diario/2003/08/21/s-03901.htm (n.d.). Retrieved on March 29th, 2016, from http://portalacademico.cch.unam.mx/alumno/biologia2/neutralismoyequilibrio/equ ilibriopuntuado Rivera, Á. (2007). Evolución y conducta. ARQUEOWEB: Revista sobre arqueología en internet, 1(9). Rothhammer, F. (1984). Evolución gradual o revolución genética. Revista chilena de Historia Natural, 57: 5-7. Tarancón, J. (2013). Geología. Retrieved on March 29th, 2016, from http://gealogia.blogspot.com.co/2013/04/la-evolucion-en-mosaico.html Glossary • Adaptation: Physiological process or morphological or behavioral trait of an organism that has evolved during a period by means of natural selection, in order to increase expectancy in the long term to reproduce successfully. • Common ancestor: Living creature or species from which two or more individuals of a species descends. • Chromosomes: Organelle in the form of filament found in the interior of a nucleus of a eukaryote cell, containing genetic material. • Offspring: Offspring, or progeny, is the result of reproduction, which means, the individual or individuals produced during the intervention of one or more parents. • Genetic Divergence: The result of adaptations and mutations that act on populations. • Diversity: Refers to the ample variety of living creatures on Earth and the natural patterns forming it, resulting in billions of years of evolution. • Speciation: The process in which a population of a determined species makes room for another population, reproductively isolated from the previous population, and gathering genetic differences throughout time. • Species: The compound of natural organisms or populations capable of mating and producing fertile offspring, but not capable to do so (or at least not commonly) with members of populations from another species. • Evolution: The change in phenotypic genetic heredity of biological populations through generations that has originated diversity of living creatures existing on Earth, from a common ancestor. • Gene: Particle with genetic material that, along with others, is found on a fixed order on a chromosome, and determines the appearance of hereditary characters in living creatures. • Gradualism: The evolution process that occurs through soft and continuous changes of the populations in time. • Mutation: A change in the genetic information (genotype) of a living creature, producing a variation in the characteristics of the organism and is not necessarily transmitted to the offspring. It occurs spontaneously and suddenly, or by the action of mutagens. This change will be present in a small proportion of the population (variant) or in the organism (mutation) • Kinship: The link that joins species that have a common ancestor. • Population: The compound of organisms or individuals of the same species that co-exist in the same space and time. • Punctuationism: A theory that determines that during most of the existence of a species, it will remain stable or presenting minor changes (stasis periods), gathering evolutionary changes during the process of speciation (formation of new species), that will result in a species of brief genetic revolution in geological terms. • Natural Selection: A phenomenon in evolution defined as the differential reproduction of genotypes in a biological population. The classic formulation of natural selection establishes that the conditions of an environment can be beneficial or harmful; meaning that reproduction of living organisms is selected according to their singularities.