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What sets humans apart from other organisms? Our brain! Humans have the largest brains of all vertebrates relative to our body size. Our cerebrum has 86 billion neurons (nerve cells) connected by trillions of synapses. The human brain has the capacity to store 1.25 x 1012 bytes.1 Has modern human’s 200,000 years of development and the human brain’s impressive capacity guarded the human brain from disorder? Clearly, this is not true since diseases of the brain exist. But why do they exist? Why have we not been able to prevent disorders from disrupting our complex and powerful brain?
Currently, millions of dollars are being invested by countries like the US to learn more about the brain, yet we still do not completely understand many of the cognitive and functional mechanisms of our brain that make us so uniquely human. President Barack Obama's BRAIN Initiative is currently investing $100 million into brain research and technology. Through funding to the National Institutes of Health and other government agencies, universities and research foundations have access to $240 million allotted for neuroscience research projects.2 With the combined efforts of these groups are we on the verge of new discoveries regarding the human brain?
With a rising population of baby boomers who have retired or will soon do so, concern about diseases that develop at an older age is on the rise. According to a Scripps article on illnesses such as cancer, diabetes, and heart disease, Alzheimer’s disease is a major health concern of individuals who are retired or soon entering retirement.3 My students will become adults in the next few years and many will enter the work force. Their voting decisions and efforts in the field of health and science could directly impact our senior citizens and the healthcare available to them. Thus, this unit designed for students studying Anatomy and Physiology will provide students with a background on the brain and how evolution has shaped the human brain over time. Despite attempts to curve the path of evolution, humans will continue to be subjected to the devices of natural selection hindering our attempt to be in control of our own fate. To aid my students’ understanding of natural selection’s imperfections, the study of the brain will include a focus on the evolution of disease focusing on two very different yet similar neurodegenerative diseases: Alzheimer’s and prion diseases.
School Background and Rationale
Mt. Pleasant High School, located on the east foothills of San Jose, California is one out of 11 comprehensive high schools in East Side High Union School District. Our school currently enrolls approximately 1350 students with an ethnic breakdown of 71% Hispanic/Latino, 19% Asian, and 8% all other ethnicities. 60% of the students receive free and reduced lunch and the school also receives Title 1 funding.4 Because of the social and cultural dynamics of my students’ families, often my students live with an elderly parent or grandparent. Each year that I have introduced the central nervous system as a topic in Anatomy and Physiology, many students have expressed interest in learning about Alzheimer’s disease (AD) and dementia. Sadly, I have several students who realize they are living with grandparents with signs of dementia but are undiagnosed. Their personal stories and experiences are the reasons for this unit. With the writing of the unit, I hope to gain an improved ability to explain the evolution and development of the human brain, disease evolution, and how AD and prions affect the central nervous system.
Raising the topic of evolution and disease evolution will pique student’s interest but it will also cause them to question many of their theological and cultural beliefs. To preface this discussion, students will be asked to keep an open mind in order to foster a classroom environment in which students can voice their confusion, their conflicting viewpoints, and their disbelief. Students will be held to the expectation that they must be able to decipher fact versus opinion and thereupon are given the choice to accept what science has to offer or continue to hold on to their own beliefs.
The topics of natural selection, adaptation, and inheritance will not be completely new to my 11th and 12th grade students, since, as 9th graders, students studied these themes in their Biology classes. Despite this expectation many students will only remember the phrase “survival of the fittest” but will not recall how to explain adaptation, inherited traits, and common ancestry. This unit will thus serve to remind students of the key points of Darwin’s work on evolution by natural selection, yet extend their understanding of natural selection by focusing on the human brain.
Anatomy and Physiology at Mt. Pleasant High School is designed for students in their junior or senior years of high school. Students taking this course usually have some interest in majoring in nursing, physical therapy, or the medical field. Because of the changes in science standards, teachers in our district are revamping their curriculum to include the Next Generation Science Standards (NGSS). NGSS requires students to discuss the evolutionary relationships among organisms and be able to describe examples of genetic variations in a population that will lead to increased ability to survive and reproduce in a specific environment (Appendix: Implementing District Standards). Since this unit will be taught as an extension of the central nervous system curriculum that I already teach, students will study the major structures of the central nervous system, the mechanism of neuron signal transmission, and the functional regions of the brain.
The Modern Brain
The central nervous system which includes the brain and the spinal cord controls all of the nervous system. It is the center for all neural signals and integrates and coordinates all activities of the nervous system. The nervous tissues that comprise the brain can be described as grey matter and white matter. Grey matter contains mostly the cell bodies of neurons (the cells of the nervous system) and white matter which contains the myelinated axons of neurons. In the brain tissue, white matter can be found in the inner portions of the brain and grey matter on the outside. Neuron clusters amplify the signals found on individual neurons. Collectively neurons coordinate all functions of the brain and require massive amounts of energy to run.
The 3 major regions of the brain are the forebrain, the hindbrain, and the midbrain. The soft tissue of the brain is protected by multiple layers of tough tissue beginning with the bony skull, and the meninges. The meninges encloses the brain and spinal cord in 3 membranes - the dura mater, the arachnoid mater, and the pia mater. The forebrain contains 3 major regions: the cerebrum, the thalamus, and the hypothalamus; each of the three regions have specific functions.5 The cerebrum, which is the major part of the brain, comprises two regions: left and right cerebral hemispheres. The two hemispheres of the cerebrum each control the opposite side of the body. The left hemisphere controls the movements of the right side and the right hemisphere controls the left. The major functions of the cerebrum include higher intellectual skills, memory, consciousness, movement, and language acquisition.6 The thalamus, located at the base of the forebrain serves as a connection point between the cerebellum (the small part of the brain behind the cerebrum responsible for coordination and balance) and sensory areas of the brain. Finally, the hypothalamus, located just beneath the thalamus, maintains blood pressure, temperature, and emotions.7 The hindbrain is comprised of the cerebellum, the medulla oblongata, pons, and midbrain. Individually they function to coordinate and relay information related to reflexes, and house control centers for heart rate, breathing, swallowing, and coughing. Finally, the midbrain, housed above the pons on the brainstem controls visual and auditory information.8
The wrinkles of the cerebrum are known as the cortex. There are different regions to the cortex, depending on its function. Some areas are for interpretation of sound, sight, and smell. Other cortex regions form memories and store them. Alzheimer’s disease ravages these areas and later damages the surrounding regions.
Evolution of an Intelligent Brain
Though with little technology or evidence to support his statement, Charles Darwin in The Descent of Man correctly asserted the interrelatedness of our species to great apes such as gorillas and chimpanzees. Darwin further stated that modern humans were directly descended from an ancient version of humanlike primates that migrated out of Central Africa some 60,000 years ago.9 Darwin’s own Victorian society and even members of today’s society struggle with the fact that humans and apes share a common ancestry; over time as a result of multiple pressures that selected for human-specific traits, we successfully reproduced in large numbers and proliferated by spreading around the Earth. We simply cannot ignore this fact unless through sheer will to disavow the fossil record and clear genetic evidence. Evolution of humans did occur and natural selection was the major mechanism by which it happened.
Most of the students in my classes can accept Darwin’s descent with modification, but struggle with the question, “What makes us unique?” Many would answer this by saying that it is our intelligence. However, understanding intelligence is difficult for teenagers to grasp since they often simply want to know how to become more intelligent. Unfortunately, instead of giving them a deeper understanding of how intelligence develops, adults brush off their question with the answer, “Read more.” Though reading more would improve intelligence, perhaps students would be better served if they were given a more complete and broader answer. We have only limited understanding of human intelligence and why the human species has evolved to be a decision-maker that dictates the fate of so many other species. Evidence for what sets “us” apart from “them” is varied and some lines of evidence can be subjective. Through this unit, I hope to aide my students to decide for themselves what distinguishes modern humans from our most recent ancestors and current great ape relatives, through the study of brain size, gyrification, and genetics.
Brain size and gyrification
In his book Why Evolution is True, evolutionary biologist Jerry Coyne asserts that abundant evidence supports the views of Darwin and more recent scientists, on how humans evolved from non-human ancestors. This evolution starts from Pan with its small brain, large teeth, and capability of bipedalism to Homo with its large brain, small teeth and exclusive bipedalism.10 In the past 7 million years the human brain has tripled in size. The evidence for this statement comes from the measurement of the insides of skulls giving anthropologists the volume of the brains that occupied the skulls. Because we do not have brain samples from our ancestors, we rely on observations from the endo-cranial volumes of fossil skulls that we have discovered. Australopithecus afarensis, or the famous ‘Lucy’ fossil, had an internal skull volume of 400-550 ml; Homo erectus had a skull volume of 600 ml; whereas modern chimpanzees have skull volumes of 400 ml, and gorillas have volumes of 500-700 ml. Today, modern human brains range in volume between 1200 and 1500 ml, clearly indicating that brain size in human-like primates has increased over time, and that our brain size is much larger than our close relatives.11
Along with brain size, another area of brain evolution research that supports the argument of humans’ superior intelligence and advanced evolution is the complexity of folds of the cerebral cortex. With increasing mass, our brain was selected to reorganize and to develop brain regions that would allow efficient problem solving and decisions over newly encountered challenges. Examples might be migration out of Africa, adapting to new local environments, searching for new sources of food, greater reliance on walking upright, and the creation and utilization of simple and complex tools.
Since neural connectivity in a species predicts the brain’s coherence and predictive power, the cerebral cortex was selected for greater growth. Studies regarding the growth of the cerebral cortex are leading researchers to conclude that increased folding of the cerebral cortex correlates with intelligence. Michel Hofman in Frontiers in Neuroanatomy reviews the organization of the human brain, specifically describing the organization of the cerebral cortex. Hofman states that the complex folding of the cortex region allows for more folding that benefits faster brain processes.12 This is an interesting point with regards to evolution since many species who have smaller, smoother brains do not have the intellectual capacity of humans. Organisms like lizards and mice have very smooth brains. In contrast, organisms like elephants and dolphins that are known for their intelligence, have an increased amount of gyrification, which is the process by which the brain undergoes folding in order to achieve greater amounts of sulci and gyri – the folds of the brain.
In essence because of the increased folding, there is more surface area to the modern human brain creating opportunities for neurons to increase their interactions. Furthermore, scientists have tracked higher order species as having more brain mass. Studies show that over time both grey matter and white matter regions have increased. In fact, modern humans have double the amount of white matter than grey matter. They have more brain cells (neurons) than other animals contributing to the hills and valleys of our brain known as gyri and sulci. Because humans have more brain mass, the cerebral cortex is pressured to fold into itself in order to balance the increase in size within the confines of the skull. When comparing humans to our close animal relatives such as primates, human brains simply have more gyri and sulci that help explain our greater intelligence.13
An interesting question by Hofman in the article “Evolution of the human brain: when bigger is better” is whether the human brain is reaching its processing capacity. Because the brain cannot infinitely grow in size and the cerebral cortex cannot fold infinitely, Hofman argues that, at some point, the brain will reach a limit for cognitive abilities. Though the modern human brain has grown in size and gyrification has increased its complexity, neurons are limited by their own structure and signal transmission time. Hofman poses, “Could this be an indicator that the human brain has reached its apex of biological intelligence?”14
President Obama’s BRAIN (Brain Research through Advancing Innovative Neurotechnologies) Initiative is driving brain research to new levels of understanding. According to Kavli Institute for Neuroscience at Yale, one of many research groups in the BRAIN Initiative, evolutionary genomics will help scientists find answers to the mechanisms of brain evolution.15 Brain evolution is not easy to study, however. Most studies have focused on comparative anatomy, whereas the current work of James Sikela, Daniel Geschwind, and James Noonan strives to understand the uniqueness of our modern brain using genetic tools. The genetic tools currently available to scientists allow them to compare the genomic data of other primate species to our own. Instead of looking at specific genes and trying to decipher whether a set is particularly significant to human brain evolution, the team is able to investigate the genome as a whole.
One aspect of their work uses filters on a genome to find regulatory sequences. Regulatory sequences are nucleic acids that do not code for DNA but are important for the monitoring of gene expression. Sikela and colleagues monitor the up-regulation or down-regulation of certain genes, essentially searching for when certain genes are expressed. Unlike genes that affect brain development, regulatory sequences can be modified and therefore show more variation. This allows scientists to discover and study genetic sequences that have been conserved in the genome of different species. If these sequences appear, then it was probably important to the species being studied and therefore conserved by evolution. These same genomic filters are being used to find other regulatory sequences that might be influencing brain size and complexity.16
Sikela and his colleagues are also focused on genes that are highly duplicated. James Noonan, looked at the genomes of Neanderthal and Denisovan humans and found that there were only 84 different protein-coding sites in the entire genome, indicating the close similarity of Neanderthal and Denisovan genomes. When studying a specific coding region, their work showed Neanderthal brains had more copies of the coding region compared to modern humans. Sikela believes this may be attributed to the fact that Neanderthals had a larger brain mass than modern humans. In addition, Sikela et al. learned that there are only 134 genes that are elevated in humans compared to chimps, gorillas, and monkeys. Looking specifically at one gene, DUF1220, their team found the gene repeatedly in different genomes. In fact, there were as many as 270 more DUF1220 gene copies in humans than in other organisms! This difference indicates that the presence of these genes may be evidence of human brain evolution, because we share the same genes with other animals, yet have so many more copies. Unfortunately, elevated copies of these same genes seem to make humans more susceptible to brain diseases such as schizophrenia, autism, microcephaly, and macrocephaly.17
Evolution of Disease and Evolutionary Medicine
Students in Physiology become hyper focused when diseases and disorders are mentioned in class. It seems an inherent or intrinsic motivation to pay attention when they are introduced to a new disease. But, teenagers have a difficult time relating to disease brought on by advanced age since they perceive themselves to be impervious to disease. To engage my students, I often include topics that include health and disease topics across different ages in order to entice them to pay attention to others rather than just themselves. By gaining awareness of the evolution of disease, I hope my students will be able to recognize the need to consider medicine more holistically, in light of other scientific disciplines.
The study of evolutionary medicine permits scientists to consider the importance of evolutionary biology to better understand public health issues and matters of health and disease. By definition, disease is simply a disorder of structure or function in an organism. Evolutionary medicine views disease in several ways. One view of disease is that it is a mismatch between an organism’s genetic origins and evolution in an ancient environment, which can be at odds with living in a current environment. Essentially, from an evolutionary standpoint a person may develop a disease because they are unable to function properly under their current “temporal” or “structural” constraints.18 In other words, a person may develop a disease because they are no longer able to fit their current environment. Gluckman et al. state “selection does not act to promote either health or longevity but rather operates to sustain and maximize fitness.”19
With diseases like AD, prion diseases, kuru, and Creutzfeldt-Jakob disease, has the acceleration of human brain evolution made us more susceptible to protein folding diseases? Recall that natural selection does not cause disease but influences our susceptibility to disease in particular environments. Chris Dobson questions the benefits of a quickly evolving brain with the following observation. The seemingly fast rise and decline of diseases like kuru and bovine spongioform encephalopathy is due to human interaction with our environment and the other species within in it. Human actions are, in effect, accelerating the natural progression of evolution to our own detriment.20 With our astonishing brain power are we then overtly influencing our own evolution? Dobson cautions our need to advance so quickly stating, “Evolution acts slowly, and we are an impatient species.”21
Misfolded protein diseases
In a 2002 article in the journal Nature, Chris Dobson describes the impact of diseases caused by the misfolding of proteins. “Getting Out of Shape” highlights the commonalities among AD, transmissible human amyloid diseases like kuru, and transmissible spongiform encephalopathy. All three are problems with proteins, specifically misfolded proteins.
Proteins are typically soluble in normal form, but when proteins change conformation and create aggregates, they become difficult for the body to remove. Interestingly, all proteins have the ability to change, but which proteins are more likely to change is highly variable. Though humans have 20 amino acids to run all the complex mechanisms in the human body, and we produce about 50,000 different proteins, the combinations of those 20 amino acids become thousands of different polypeptides all interacting in a specific manner; this estimate adds to the complexity and awe of the evolved human body.
When these proteins change in their folding conformation from the globular state to sheets, they create problems for humans. Evolutionary processes have selected amino acids that form monomeric structures to persist, because they form the backbone for many different types of polypeptides. Unfortunately, when the structure changes slightly a protein can become vulnerable to re-conformations or new-folding that may generate amyloid fibrils, which can cause amyloidosis: disease caused by the accumulation of amyloid fibrils.22 Dobson notes that one reason why amyloidosis is often found in older people is because controls that prevent proteins from misfolding degrade with age. Though many proteins last only a short time, weeks as opposed to years, some proteins can span a person’s life time, like those in the eyes. Perhaps the reason for the answer to why certain proteins misfold with advanced age is that evolutionary pressures have allowed our genes to encode for these proteins to favor the young, or remain protective only through the reproductive years.
Every 67 seconds someone in America develops Alzheimer’s disease (AD).23 Every single person is vulnerable because every human has a brain. Unfortunately today, 110 years since Dr. Alois Alzheimer’s discovery, we still do not have a cure for AD despite progress in understanding how the disease develops. Alzheimer’s disease is the most common form of dementia, memory loss, and problems with behavior and thinking. Though many patients develop AD after the age of 65 years old, 5% develop younger onset AD. AD is a progressive disease in which symptoms worsen over time. AD can last between 4 years to 20 years.24 According to Bufill et al., AD prevalence doubles every 5 years. Most cases of AD are caused by multiple factors: advanced age, history of cranial trauma, exposure to certain toxins, and carriage of a specific allele called apolipoprotein epsilon 4 (Apo ε4). The work of Bufill et al. attempts to explain the cause of AD using an evolutionary approach. The team believes the brain’s genetic changes have made it more susceptible to factors that cause disease.25
The hallmark of AD is the development of plaques that stifle brain cell ability to perform tasks. AD’s appearance in the brain can involve either plaques or tangled protein forms; however, both of these damage or kill nerve cells. Plaques in the form of protein fragments called beta amyloid appear on the outside of neurons. Tangles made of tau proteins appear inside neurons.26
Though AD is the most well-known neurodegenerative disease, there are others that affect humans in a similar fashion known as prion-related diseases. Many Americans, like myself, were introduced to prions when the cattle industry in the United Kingdom was ravaged by mad cow disease. Between the years of 1986-2001, 180,000 cattle were affected and terminated.27 Though the disease is specific for bovines (called bovine spongiform encephalopathy), humans that ate tainted beef came down with a form of Creutzfeldt-Jakob Disease called variant CJD, raising public concerns about the consumption of meat contaminated with prions.
Prions themselves are naturally occurring and are simply amino-acid chains. However, despite its lack of genetic-based inheritance using DNA or RNA, prions show typical hallmarks of Darwinian evolution including variation, natural selection, and adaptation. Though prions are not living organisms, they are interesting to study because prions show evolution by natural selection over time. Thus, intriguingly natural selection is occurring in a system that is non-living. Prions present an aberrant form of evolution, where natural selection occurs but nucleic acid based inheritance does not exist.
Prion diseases are transmissible spongiform encephalopathies (TSEs). TSEs have the ability to increase neuron loss and cause the characteristic spongiform on the brain tissue. Prions are infectious particles that act like bacteria and viruses, because they can spread from one organism to another. Humans can acquire prion particles through blood transfusions, injections of human hormone, surgery with contaminated instruments, and even more commonly oral uptake through eating tainted meat. Unlike viruses, prions lack information storage components like RNA or DNA, but they “act” like viruses in that they can make copies of themselves and transmit biological information across generations. Like all proteins, prion proteins are made of subunits of amino acids, with sticky ends prepared to attach to the next subunit. In its elongation process, subunits are added to the end of the growing protein, laying down new subunits like bricks. Unlike healthy proteins, prions have amyloids which effectively stop neurons from communicating with one another.
Prion disease is due to the buildup of abnormally folded prion proteins, also known as rogue proteins. In its progression, the rogue proteins recruit other proteins, and create more abnormally folded proteins. The resulting accumulation of these rogue proteins interfere with the brain’s ability to communicate via its neurons. The disease has a very long incubation period, up to 30 years! This means a person may not develop any symptoms of spongiform encephalopathy until many years after consuming tainted meat. Prion diseases can be categorized into sporadic, inherited, and acquired prion diseases.
There are several different kinds of human prion diseases including Creutzfeld-Jakob Disease (CJD), variant Creutzfeldt-Jakob Disease (vCJD), fatal familial insomnia, Gerstmann-Straussler-Scheinker syndrome, and kuru. Animal prion diseases include bovine spongiform encephalopathy (BSE), chronic wasting disease (CWD), and scrapie. The earliest known evidence for prion disease comes from scrapie in sheep in goats in the 1730s. Later, AD was discovered in 1906, followed by CJD in 1920.
Classroom Activities & Strategies
Our school and district is moving towards incorporating NGSS (Next Generation Science Standards) and working to move the cognitive load from teachers to students. One aspect of this work includes improving students’ depth of knowledge (DOK).28 Teachers are reorganizing and creating lessons to answer the challenge of NGSS and Common Core. One aspect of NGSS dictates that students are better able to model different scientific phenomena. Thus, I hope to create an activity in which students not only model the change of human brain structure when affected by prions but also have them model beta-amyloid plaques and their destruction of neuronal transmission. Combined with flipped classroom activities and readings, students will participate in four main activities: anonymous surveys, modeling of brain evolution and disease, letters to loved ones with Alzheimer’s, and presentations related to neurodegenerative diseases. Because our district is continuing its focus on literacy in the content area, this unit will include multiple primary resource readings and videos to support their essays and presentations.
Along with improving content rigor by Webb ‘s DOK levels, our district motto of 5C’s aligns very closely with a July 2016 National Public Radio (NPR) story that described strategies and activities that would help children become smarter. NPR cited that children should be engaged in activities that include the 6 C’s: Collaboration, Creativity, Critical Thinking, Communication, Content, and Confidence.29 These 6 C’s are very closely aligned to our district’s goals of 5 C’s which include: Collaboration, Creativity, Critical Thinking, Communication, and Civic Engagement. The story emphasizes that classroom and home activities should incorporate these C’s in order to foster intelligence and emotional development.
In our district, students have access to Chromebook laptops. Students and teachers are encouraged to utilize technology to enhance and extend their lessons. In this first activity students will use web based surveying in order to participate in an early discussion of evolution. Since my students come from a variety of cultural and religious backgrounds, using an anonymous survey to gauge the pulse in the room regarding evolution allows all students to participate without fear of judgment or being wrong. This activity will also allow me to assess their prior knowledge regarding Darwinian evolution. Questions that can be included in the survey include: 1. On a scale of 1-5 how much do you agree or disagree with the following statement- I believe in the theory of evolution. 2. On a scale of 1-5 how much do you agree or disagree with the following statement- I believe in that our human ancestors included Neanderthals and Australopithecus africanis. 3. On a scale of 1-5 how much do you agree or disagree with the following statement- I believe in that our human ancestors included Neanderthals. 4. On a scale of 1-5 how much do you agree or disagree with the following statement- Only organisms that are the strongest, fittest, fastest are able to reproduce. I expect that the activity will lead to a rich discussion among all my students which will open up an opportunity to change their misconceptions during lectures and class readings.
After a series of lectures and internet research reading activities students will be asked to show their creativity and understanding of the human brain evolution through the creation of models. This will be a continuation of a previous project in which they have created adult size skeletons from scratch. Because our school utilizes RAFT (Resource Area for Teachers) teachers are able to purchase recycled goods from local companies for their classroom.30 My intention is to have my students use random recycled materials, including balloons, Styrofoam, scraps of cloth, and plastics for students to envision and construct the structure of the modern human brain. This activity will require students to be creative and collaborative. They will need to justify the use of the recycled material, giving reasons for its relation to the functional areas of the brain. In this way students are integrating engineering practices within their learning process. After the completion of this first model, students will be asked to include a second model that shows the difference between our ancient ancestors and how a diseased modern brain would appear. Since this activity requires quite a bit of planning and time, students will be encouraged to work in collaborative groups.
Each year, when I have introduced students to Alzheimer’s disease, I have shown them different videos of people’s testimonies as they progress with Alzheimer’s. To express their understanding of the disease’s impact on the brain and even more so, on the victims of the disease, students will be asked to write a letter to themselves describing what it means to live with Alzheimer’s. My hope is that students will not only learn to empathize with those suffering with the disease, but also practice expressing their emotional communication skills through their personal letter.
As a conclusion to this unit, students will be asked to display the results of the above mentioned activities. Students will share their work to other peers and adults at our school during a Health Forum event. This event will showcase their understanding of brain evolution and brain diseases while fulfilling our district’s 5Cs.
Appendix: Implementing District Standards
Students studying this unit will be able to complete the following NGSS standards:31
Disciplinary Core Idea: Environmental factors affect expression of traits, and affect the probability of occurrences of traits in a population. Variation and distribution of traits observed depends on both genetic and environmental factors.
Students in Anatomy and Physiology will be able to follow variation in the development of the human brain. These variations will allow students to trace the traits that lead back to our last common ancestor. Though a study of genetics and heredity will not be covered within the scope of the unit, a review of genetic inheritance, genetic recombination, and the ability for mistakes in gene replication (mutation) to diversify the gene pool is necessary to understand how the human brain has evolved.
Evaluate the evidence supporting claims that changes in environmental conditions may result in: (1) increases in the number of individuals of some species, (2) the emergence of new species over time, and (3) the extinction of other species.
LS4.C: Adaptation: Changes in the physical environment, whether naturally occurring or human induced, have thus contributed to the expansion of some species, the emergence of new distinct species as populations diverge under different conditions, and the decline–and sometimes the extinction–of some species. Species become extinct because they can no longer survive and reproduce in their altered environment. If members cannot adjust to change that is too fast or drastic, the opportunity for the species’ evolution is lost.
Students studying this unit will show how the evolution of the brain including growth of the cortex, increased gyrification of the neocortex, and increased neural connectivity has contributed to the success of humans as a species. Furthermore, students will be able to communicate that the success of the species is also connected to our ability to adapt to new environments.
- Hofman, “Evolution of the human brain: when bigger is better”
- Gregoire, “5 Amazing Advances in Brain Research” Accessed July 18, 2016
- www.scripps.org, “Top ten health concerns of baby boomers”, Accessed August, 2016
- data.cde.gov, SARC report 2014-2015
- McGraw Hill, Hole’s Anatomy, 387
- National Geographic Genographic Project, Accessed July 19, 2016
- Coyne, What About Us, 197
- Sikela, Noonan, and Geschwind, “Evolution: What’s Uniquely Human About the Human Brain? (accessed April McGraw Hill, Hole’s Anatomy, 38730, 2016), 6
- Hofman, “Evolution of the human brain: when bigger is better.”
- www. Livescience.com/29365-human-brain.html, accessed July 15, 2016
- Sikela, Noonan, and Geschwind, “Evolution: What’s Uniquely Human About the Human Brain? accessed April 30, 2016), 4
- Ibid, 6
- Ibid, 2
- Gluckman, Hanson, Beedle, 235
- Ibid, 9
- Dobson, “Getting Out of Shape"
- Alz.org, (accessed June 22, 2016)
- Bulfill, Blesa, Agusti
- Alz.org, (accessed June 22, 2016)
- Gluckman, Hanson, Beedle, 7
- Norman Webb’s depth of knowledge, Accessed August 3, 2016
- Kamenetz, Anya, “How to Raise Brilliant Children According to Science,” Accessed August 4, 2016
- RAFT, Resource Area for Teachers
- NGSS Framework for high school science
Arnold. National Center for Biotechnology Information. Accessed June 26, 2016. http://www.ncbi.nlm.nih.gov/pubmed/22137143.
"Brain Disease 'resistance Gene' Evolves in Papua New Guinea Community; Could Offer Insights into CJD." ScienceDaily. November 21, 2009. Accessed July 11, 2016. https://www.sciencedaily.com/releases/2009/11/091120091959.htm.
Browning. "Darwinian Evolution of Prions in Cell Culture Jiali Li, Et ..." Accessed June 26, 2016. http://ag.arizona.edu/mycoherb/arnoldlab/teaching/2011 stuff/PrionsEvolve.pdf.
Bulfill, Enric, Rafael Blesa, and Jordi Agusti. "Alzheimer's Disease: An Evolutionary Approach." Journal of Anthropological Sciences 91, no. 2013, 135-57. Accessed July 12, 2016.
Journal article discusses the association of Alzheimer's disease and evolution. Article
poses questions that allow for further discussion.
Centers for Disease Control and Prevention. 2015. Accessed June 26, 2016. http://www.cdc.gov/prions/index.html.
Collinge, J. "Prion Strain Mutation and Selection." Science 328, no. 5982 (2010): 1111-112. doi:10.1126/science.1190815.
Coyne, Jerry A. Why Evolution Is True.
This book provides a complete and easy to understand evidence for evolution while
discounting intelligent design. This is a good resource for understanding everything from
adaptation, speciation, sexual selection, and other lines of evidence for evolution.
Darwin, Charles. The Origin of Species ... and the Descent of Man .. New York: Modern Library, 1859.
"Darwinian Medicine." Accessed July 11, 2016.
Overview of Darwinian Medicine including background on natural selection, adaptation, and proximate explanation related to disease development.
Dobson, Christopher M. "Protein-misfolding Diseases: Getting out of Shape." Nature 418, no. 6899 (2002): 729-30. Accessed July 11, 2016. doi:10.1038/418729a.
"Evolution: What's Uniquely Human About the Human Brain?" The Kavli Foundation. Accessed June 26, 2016. http://www.kavlifoundation.org/science-spotlights/evolution-what’s-uniquely-human-about-human-brain.
"Evolutionary Descent of Prion Genes from the ZIP Family of Metal Ion Transporters." PLOS ONE:. Accessed June 26, 2016. http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0007208.
Gluckman, Peter D., Felicia M. Low, Tatjana Buklijas, Mark A. Hanson, and Alan S. Beedle. "How Evolutionary Principles Improve the Understanding of Human Health and Disease." Evolutionary Applications 4, no. 2 (2011): 249-63. Accessed July 11, 2016. doi:10.1111/j.1752-4571.2010.00164.x.
Gregoire, Carolyn. "5 Amazing Advances In Brain Research In 2014." The Huffington Post. Accessed July 18, 2016. http://www.huffingtonpost.com/2014/12/31/brain-research-2014_n_6334088.html.
This article shares 5 major advancements in brain research and shares current research
related to the BRAIN Intiiative.
"Help End Alzheimer's." Alzheimer's Association. Accessed June 19, 2016. http://www.alz.org/.
Hofman, Michel A. "Evolution of the Human Brain: When Bigger Is Better." Front. Neuroanat. Frontiers in Neuroanatomy 8 (2014). Accessed July 15, 2016. doi:10.3389/fnana.2014.00015.
Article discusses the evidence behind the evolution of the human brain including a
discussion whether the human brain is at the point in which it is reaching its capacity.
"How To Raise Brilliant Children, According To Science." NPR. Accessed August 06, 2016. http://www.npr.org/sections/ed/2016/07/05/481582529/how-to-raise-brilliant-children-according-to-science?utm_campaign=storyshare.
"Molecular Evolution of Prions." Molecular Evolution of Prions. Accessed June 26, 2016. http://www.mad-cow.org/~tom/prion_evol.html.
“National Center for Biotechnology Information. Accessed June 26, 2016. http://www.ncbi.nlm.nih.gov/pubmed/24401672
"NGSS Search the Standards." Next Generation Science Standards. Accessed July 17, 2016. http://www.nextgenscience.org/search-standards?keys=.
"Prion Biology and Diseases (Cold Spring Harbor Monographs Series) / Edition 2." Barnes & Noble. Accessed June 26, 2016. http://www.barnesandnoble.com/w/prion-biology-and-diseases-stanley-b-prusiner/1101420688.
"Prions and Prion Disease." Prion Clinic. Accessed June 26, 2016. http://www.prion.ucl.ac.uk/clinic-services/information/prion-disease/.
"Prions Point to a New Style of Evolution." New Scientist. Accessed June 26, 2016. https://www.newscientist.com/article/mg21328524-800-prions-point-to-a-new-style-of-evolution/.
ScienceDaily. Accessed June 26, 2016. https://www.sciencedaily.com/releases/2009/09/090928131210.htm.
"Scripps Health - Top 10 Health Concerns of Baby Boomers." Scripps Health. 2015. Accessed August 03, 2016. https://www.scripps.org/news_items/5475-top-10-health-concerns-of-baby-boomers.
Use for a survey on health concerns among aging Americans.
Sherwood, Chet C., Francys Subiaul, and Tadeusz W. Zawidzki. "A Natural History of the Human Mind: Tracing Evolutionary Changes in Brain and Cognition." J Anatomy Journal of Anatomy 212, no. 4 (2008): 426-54. Accessed July 12, 2016. doi:10.1111/j.1469-7580.2008.00868.x.
Shier, David, Jackie Butler, and Ricki Lewis. Hole's Essentials of Human Anatomy and Physiology. Boston: McGraw-Hill, 2006. Accessed July 06, 2016.
Anatomy and Physiology textbook used for high school science courses. This book provides background information needed for the teaching of the central nervous system.
"The Bright Side of Prions | The Scientist Magazine®." Accessed June 26, 2016. http://www.the-scientist.com/?articles.view/articleNo/38721/title/The-Bright-Side-of-Prions/.
"The Human Journey: Migration Routes." Genographic Project. Accessed July 19, 2016. https://genographic.nationalgeographic.com/human-journey/.
"Using Webb's Depth of Knowledge to Increase Rigor." Edutopia. 2014. Accessed August 03, 2016. http://www.edutopia.org/blog/webbs-depth-knowledge-increase-rigor-gerald-aungst.
Edutopia article describing DOK levels and its use in the classroom.
Yankner, Bruce A., Tao Lu, and Patrick Loerch. "The Aging Brain." Annu. Rev. Pathol. Mech. Dis. Annual Review of Pathology: Mechanisms of Disease 3, no. 1 (2008): 41-66. Accessed July 11, 2016. doi:10.1146/annurev.pathmechdis.2.010506.092044.
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