{"id":37,"date":"2017-09-01T17:44:56","date_gmt":"2017-09-01T17:44:56","guid":{"rendered":"http:\/\/americanboard.org\/Subjects\/general-science\/?page_id=37"},"modified":"2017-09-18T15:33:42","modified_gmt":"2017-09-18T15:33:42","slug":"life-in-review","status":"publish","type":"page","link":"https:\/\/americanboard.org\/Subjects\/general-science\/life-in-review\/","title":{"rendered":"Life in Review"},"content":{"rendered":"
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\u2b05 Previous Lesson<\/a>\u00a0Workshop Index<\/a>\u00a0Next Lesson \u27a1<\/a><\/div>\n

<\/p>\n

Life in Review<\/h1>\n

Objective<\/h4>\n

Next, we will go over the basics of the biological sciences and get ready for more in-depth reviews into all of the major disciplines of science. Our first topics will deal with how scientists organize the diversity of living organisms and how everything in biology can be best conceptualized in the context of evolution.<\/p>\n

Previously Covered<\/h4>\n

In the last lesson, we reviewed some of the major topics of physics, including the four of its fundamental fields: mechanics, energy, waves, and the electromagnetic spectrum.<\/p>\n

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Classification of Life<\/h3>\n

When we observe the natural world, one of our innate abilities is to classify things and organize them into groups. It is how our brains work as hunters and gatherers. In order to survive as long as we have, natural selection has shaped our abilities and behaviors. One of our most remarkable abilities is to classify things into meaningful categories. This is one of the few things that humans can do better, more effectively and more efficiently, than computers.<\/p>\n

Biologists use a classification system to organize all living things into groups based on the organisms\u2019 evolutionary relationships. This also makes them easier to study and understand. Biologists use a hierarchical system of roughly eight groups to classify organisms.<\/p>\n\n\n\n\n\n\n\n\n\n\n\n\n
Group<\/th>\nEffective size<\/th>\nExample<\/th>\n<\/tr>\n<\/thead>\n
Domain<\/td>\nLargest \u2013 there are only three known Domains of life<\/td>\nEukarya<\/td>\n<\/tr>\n
Kingdom<\/td>\nUsed to be the largest with at least seven categories<\/td>\nAnimalia<\/td>\n<\/tr>\n
Phylum<\/td>\nExtremely broad<\/td>\nChordata<\/td>\n<\/tr>\n
Class<\/td>\nRecognizably related<\/td>\nMammalia<\/td>\n<\/tr>\n
Order<\/td>\nSmall and familiar<\/td>\nPrimates<\/td>\n<\/tr>\n
Family<\/td>\nMost understood<\/td>\nHominidae<\/td>\n<\/tr>\n
Genus<\/td>\nTightly related<\/td>\nHomo<\/td>\n<\/tr>\n
Species<\/td>\nSmallest groups of a single kind<\/td>\nsapiens<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

A three-domain system of classification is the most commonly used system in modern biology and is based on nucleotide sequencing in RNA molecules that may have the most information about how life evolved on Earth. The three domains are bacteria<\/abbr>, archaea<\/abbr>, and eukarya<\/abbr>. All known organisms fall into one of these categories.<\/p>\n

\"Phylogenetic<\/center>Bacteria are all around us all the time. Members of the domain bacteria are prokaryotes, whose cells lack a nucleus (a dense area that contains nucleic acids \u2013 chemical instructions for the cell\u2019s activities). Archaea are tiny organisms that thrive in some of the most extreme habitats found on Earth, from geothermal vents, where hot gases and liquids spew from ocean floors through volcanic fissures to colder, acidic, or highly alkaline waters. Biologists believe that these harsh conditions are similar to those of ancient Earth and give more evidence that these organisms may have been some of the first life on our planet. Eukaryotes are organisms that contain cell nuclei and are classified further into protists, fungi, plants, and animals. Protists are any eukaryotic organism that cannot be classified as an animal, plant, or fungus and are a mixture of different, potentially unrelated, organisms. Fungi have cellular walls, use spores to reproduce, and feed by absorbing food. Mushrooms, mold, and mildew are all fungi. Plants are multi-cellular, autotrophic eukaryotes that live on land and in both fresh and salt water. In addition, plants are autotrophs; that is they can manufacture sugars from sunlight and water. They provide the original food for all the heterotrophs on the planet. The plant phylum includes a great variety of organisms. Some plants produce flowers while others do not. Some plants, such as trees, can grow very tall while others, like mosses, never grow more than a few millimeters in height. All animals are multi-cellular eukaryotes and are heterotrophs. Animals have different adaptations that allow them to locate food, capture, eat, and digest it. Animals live in extremely diverse environments and can have complex behavioral adaptations that we find fascinating because humans are also animals.<\/p>\n
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Question<\/h4>\n

What is the proper order of the classifications of life beginning with domain?<\/p>\n

    \n
  1. Domain, class, order, phylum, kingdom, family, genus, and species.<\/li>\n
  2. Domain, kingdom, phylum, class, order, family, genus, and species.<\/li>\n
  3. Domain, kingdom, order, class, family, phylum, genus, and species.<\/li>\n
  4. Domain, order, family, kingdom, phylum, class, genus, and species.<\/li>\n<\/ol>\n

    Reveal Answer <\/a><\/p>\n

    The correct answer is B.<\/p>\n<\/section>\n

    \n

    Question<\/h4>\n

    What are the three domains in which all organisms are classified?<\/p>\n

      \n
    1. Bacteria, archaea, and species.<\/li>\n
    2. Bacteria, phylum, and eukarya.<\/li>\n
    3. Fungi, archaea, and eukarya.<\/li>\n
    4. Bacteria, archaea, and eukarya.<\/li>\n<\/ol>\n

      Reveal Answer <\/a><\/p>\n

      The correct answer is D. Bacteria, archaea, and eukarya are the three domains that encompass all know life.<\/p>\n<\/section>\n

      Darwin and Wallace<\/h3>\n

      In all of human history, one of the most important and powerful scientific theories is that of evolution. Evolution is the process by which organisms acquire and pass on traits that were not present previously. This change-through-time is generated by inherent variation and mediated by natural selection. When Charles Darwin and Alfred Russel Wallace co-founded the theory of evolution through natural selection, they were well aware of the controversy. But the evidence was overwhelming, even back in 1858. Both men had spent large amounts of time exploring the tropical rainforests and islands of the world. Darwin mostly explored South America and the Galapagos Islands from aboard the Beagle, while Wallace actually lived and worked for extensive time periods across South America and the Indo-Malaysian archipelago. Between the amazing field observations and data collected by these two outstanding natural historians, there was ample evidence to form the ideas that have led to our current understanding of evolution.<\/p>\n

      \"Alfred<\/center>Wallace and Darwin first published a joint work in 1858 that laid out the scientific establishment of the theory, while the more famous and popularized version came out in a large tome by Darwin the next year. Although it was not immediately embraced by the scientific community, the theory of evolution has become one of the most powerful paradigms in all human endeavors. Later, during the 1930s, a group of scientists furthered the idea of evolution by combining it with Gregor Mendel\u2019s work on heredity to create the modern synthesis. In this new and improved version of evolution, the idea that genes are the fundamental unit of inheritance added a crucial bit of information about how evolution really worked \u2014 at the molecular level. With this mechanism, evolution came to mean the change in allele frequency in a population over time and could be explained through four main processes: migration, mutation, natural selection, and genetic drift.<\/p>\n

      \"Charles<\/center><\/p>\n

      Outstanding in their field<\/h3>\n

      In the mid 1800\u2019s, Charles Darwin and Alfred Russel Wallace were exploring some of the most diverse ecosystems on the planet. Both scientists had uncanny abilities to categorize and theorize about the origin and maintenance of the tremendous diversity they were witnessing. Both men came up with ideas about natural selection, speciation, and the fundamentals of evolution. Observations included the sheer diversity of living things, the remains of ancient organisms, and the characteristics of organisms on islands versus their mainland counterparts (the Galapagos Islands for Darwin and the Indo-Malaysian islands for Wallace). These observations led them both to separately, and then together; develop one of the most important scientific theories of all time \u2014 the theory of evolution.<\/p>\n

      After returning to England, Darwin compared Galapagos organisms to organisms that lived elsewhere, and found many similarities and differences. He found that plants and animals were almost identical in the Galapagos as they were in South America. However, as he studied his observations more closely, he found important differences, too. He theorized that some of the organisms in the islands must have come from the mainland, perhaps blown out to sea during a storm or set adrift on a fallen log. Once they reached the islands, they reproduced for many years and the offspring, while very similar, developed differences from their mainland relatives.<\/p>\n

      The most obvious differences Darwin noticed were the sizes and shapes of bird\u2019s beaks on the various islands of the Galapagos. An examination of birds from different islands and the South American mainland revealed that the birds had slightly different beak sizes and shapes. The differences in the beaks of birds in different locations seemed to show interesting patterns: there were classes of beak size and shape that each island seemed to share. Moreover, each island seemed to not only have similar bird beak adaptations in different species, but each island\u2019s species were slightly different from every other island\u2019s and the mainland\u2019s species. Darwin hypothesized that these differences in beak shape and size were adapted to best obtain food that was available in various environments and that the differences were variations on a theme, all coming from a common ancestor.<\/p>\n

      \"Bird<\/center><\/p>\n

      Figure 1. Darwin made observations of different bird beaks like these, each adapted to food availability for the different species.<\/p>\n

      Evolution<\/h3>\n

      Darwin reasoned that plants and animals that arrived on the Galapagos Islands encountered conditions that were different from those they experienced on the mainland, and must have evolved over many generations to become better adapted to their new surroundings. While Darwin was realizing the implications of these findings, another naturalist, Alfred Russel Wallace, was in the midst of one of the most important field expeditions of all time. Unlike Darwin, whose careful and meticulous fieldwork was synergized by months of contemplative research and theorizing back home in England, Wallace was more cavalier with his thinking while in the field. For many years after his trip around the world, Darwin continued to think about what he observed and was shocked to learn that Wallace had come to the very same conclusions, while in the Indo-Malay archipelago. While Darwin refined his theory based on countless observations made 15 years earlier, Wallace was publishing the first papers on the idea of natural selection. Finally, after many letters back and forth, the pair decided to jointly publish a paper that demonstrated how evolution, whose primary mechanism was natural selection, was a gradual change in a species over long periods of time. Although Darwin gets most credit for the theory of evolution through natural selection, both he and Wallace came to the same conclusions based on tropical fieldwork.<\/p>\n

      \n

      Question<\/h4>\n

      What is the building block of change that helps a species survive and reproduce in its environment?<\/p>\n

        \n
      1. Evolution<\/li>\n
      2. Adaptation<\/li>\n
      3. Variation<\/li>\n
      4. Selection<\/li>\n<\/ol>\n

        Reveal Answer <\/a><\/p>\n

        The correct answer is C. While the other choices are viable parts of the evolutionary process, variation is the primary building block that allows natural selection and adaptation to affect change over time. If there were no variation in the first place, natural selection would have nothing to work with – and evolution wouldn’t occur.<\/p>\n<\/section>\n

        Natural Selection<\/h3>\n

        Darwin and Wallace proposed an explanation of how evolution occurs in nature. In 1858, they proposed that evolution occurs by a process of natural selection. Natural selection limits unsuitable variations that can be passed on to the next and future generations. Organisms that have successful variations are more able to pass on their genetic material (for whatever reason) and become \u201cselected\u201d naturally.<\/p>\n

        Wallace and Darwin identified many factors that can affect natural selection. They knew that most organisms produced many more offspring than could survive on the available resources. Among these numerous offspring will be variation \u2014 they are not only different from each other, but also different from their parents. Any variation that can enable certain organisms to out-breed others will be advantageous in passing on those traits. For example, if an organism is able find food faster in their environment, that may enable an organism to be more able to mate successfully, so that trait (ability to find food faster) will be passed on. Another example: one organism might have a color that protects it from predators better than the coloration of another organism. Competition is common among members of the same species when food and other resources are limited. The important factors that must accompany a biological system in order for natural selection to act, are inherent variation, some sort of competition, and differential mating success based on whatever factors are acted upon by natural selection.<\/p>\n<\/section>\n

        <\/p>\n

        \u2b05 Previous Lesson<\/a>\u00a0Workshop Index<\/a>\u00a0Next Lesson \u27a1<\/a><\/div>\n

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        \u2b05 Previous Lesson\u00a0Workshop Index\u00a0Next Lesson \u27a1 Life in Review Objective Next, we will go over the basics of the biological sciences and get ready for more in-depth reviews into all of the major disciplines of science. Our first topics will deal with how scientists organize the diversity of living organisms and how everything in biology […]<\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-37","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages\/37","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/comments?post=37"}],"version-history":[{"count":8,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages\/37\/revisions"}],"predecessor-version":[{"id":532,"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/pages\/37\/revisions\/532"}],"wp:attachment":[{"href":"https:\/\/americanboard.org\/Subjects\/general-science\/wp-json\/wp\/v2\/media?parent=37"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}