Ecosystems Natural Selection Options for Navigation Table Ecosystems
Ecosystems Natural Selection
Options for Navigation Table Ecosystems: Natural Selection Pre-Test Introduction Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Glossary
Natural Selection Pre-Test Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Click a link below to take the pre-test for this unit! • Google assessment
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Introduction
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Introduction What Happened to the Dinosaurs? The dinosaurs are gone. They, along with many non-dinosaur species, disappeared from land, the seas, and the air about 65 million years ago. The only mammals present at that time, according to fossils that have been found, were small rodent-like creatures that lived in the shadows of the giant dinosaur beasts (but there were small dinosaur species too). Dinosaurs were at the top of the animal kingdom at that time. They dominated the habitats available to animals.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know Introduction What Happened to the Dinosaurs? Continued We are not sure what killed the dinosaurs in such massive numbers as to cause the extinction of so many species. It might have been a worldwide plague of infectious disease, which we can't prove because such a plague could occur without leaving a fossil record. One theory is that a giant meteor struck the earth in the southern Gulf of Mexico near the Yucatan Peninsula. Such a crash would have thrown up so much dust and debris into the earth's atmosphere that all light would have been blocked out, making the earth suddenly very cold, and plants could not grow. This idea is popular but not yet accepted by all scientists. Another theory is that large eruptions from the Deccan volcanoes in India released large amounts of mercury and carbon dioxide. The carbon dioxide made the oceans too acidic for some ocean organisms, and their decline impacted the entire food web. What We Know Story Time Activities Self-Study Game Post-Test An example of an aquatic food web
Introduction Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters What Happened to the Dinosaurs? Continued Whatever the cause for dinosaur extinction, we are confronted with the well-documented fact that many new species of mammals appeared soon after the extinction of the dinosaurs. Many of these primitive mammals also died out, but apparently some of their descendants still exist today. Can you name some of these species? How about: How We Know Monotremes (like platypus and echidnas) What We Know Marsupials (like opossums) Story Time Activities Self-Study Game Post-Test Moles Armadillos
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Introduction What is Natural Selection? Are there certain general forces of nature that can favor some species at the expense of others? How does nature influence which species survive and which become extinct? How do humans influence species survival? You might say that nature selects which species survive and which become extinct. And you can go further and suggest that natural selection is the process by which new species might emerge. To understand natural selection, you must first understand a little about the genetic material in living organisms. The genetic material for all organisms are contained in the genes, which are located within the chromosomes in the nucleus of the cell. Genes are made of DNA and are passed from one generation to the next. This passage of genes from parent to offspring is called heredity. These genes determine some of the characteristics of the offspring.
Introduction Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What is Natural Selection? Continued Charles Darwin suggested that natural selection is the process by which new species might emerge. Darwin did not invent evolution. He discovered that natural selection was the way evolution occurs. The idea is that each species has a range of genetic variability. Genetic mutations, or changes in the genes of an organism, can introduce even more variation. The environment favors certain traits in a species, and those individuals that have such traits are more likely to survive and have more offspring that will also have these traits. Eventually, given enough time (like millions of years), the genes controlling the advantageous traits may dominate the population, and a new species may emerge. Changes in environment may put existing species at risk because their traits are no longer suitable for the new environment. If the genes of the species no longer help the species survive, extinction of species may then occur. Source: The National Archives UK
Natural Selection Ecosyste ms: Natural Selection Objectives Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test • After completing this lesson, each student should be able to: ➢ Explain what we mean by "Natural Selection" ➢ Explain how natural selection is the mechanism for the scientific view of how new species arise ➢ Give examples of how human activity changes natural selection forces
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Why It Matters
Why It Matters Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Where Did Everyone Go? In the long history of Earth (about 4. 5 billion years) most species have become extinct. The fossil record (see How We Know) shows what many extinct animals and plants were like. These life forms have never come back. Why did they disappear? Are we next? Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Mammoth W, a female mammoth, lies in situ at Waco mammoth National Monument Image courtesy of City of Waco and Dava Butler
Why It Matters Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Where Did Everyone Go? Continued Extinction occurs when drastic changes occur in climate or living conditions. A given species may or may not be adapted for life under the changed conditions. About the same time that extinction occurs, new species may appear if they have traits that are useful in the new environment. New species typically have a genetic make-up that allows them to take advantage of the changed life conditions. New species appear because they happen to be adapted to the changed conditions. Nature is thus said to exert forces to drive some species into extinction and to select new species ("natural selection"). Some species are so well adapted to their environment that they survive in spite of massive environmental change. Sharks and turtles, for example, are still with us even though they also lived in the time of dinosaurs. Mammalian fossils began appearing around the time that dinosaurs were dying out. Even some primitive mammals are still around, such as armadillos. Apparently, their anatomy (body structure), physiology (body functions), and behavior are suited for today's environment just as they were millions of years ago. Sea turtle on way back to ocean after laying eggs on beach
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know Changes in the Universe Scientists also have evidence that the abiotic (non-living) universe has been changing for millions of years. Such living and non-living changes are called "evolution. " Many people (but only a few scientists) do not believe in evolution, arguing that the idea is "just a theory. " Scientific theories are not simple opinions. They are supported by observable evidence and data. Theories that stand the test of time should be shown much respect. Scientists use theories What We Know • Story Time • • Activities Self-Study Game Post-Test Why It Matters Astronomers using NASA's Hubble Space Telescope have assembled a comprehensive picture of the evolving universe – among the most colorful deep space images ever captured by the telescope. Remember, what we see today actually happened millions of years ago. Other pictures show that the universe is expanding at an accelerating rate. to describe and unify what is observable and measurable in a way that makes the most practical sense to organize thinking about many different observations to make predictions of theory that can be tested whenever possible Absolute proof for a theory is not necessary. A theory deserves support as long as it remains useful and cannot be disproved through experimental evidence. No theory in biology meets these requirements better than theory of evolution.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Why It Matters Changes in the Universe In "modern" times, ideas about evolution were first introduced around 1865 by Charles Darwin and Alfred Wallace. When they found out about each other's work, Darwin and Wallace decided to publish at the same time. But it was not evolution that they discovered. What they discovered was how evolution occurred. Talk about evolution has always created religious arguments. In the time of Darwin and Wallace, people who thought evolution made sense were subject to vicious ridicule and condemnation as evil people. To a lesser degree, the same views exist today.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Why It Matters What Was Important About Darwin's Discovery? Darwin provided overwhelming evidence for natural selection in his famous book, The Origin of Species. After many years of sailing around the world as a passenger on the ship, The Beagle, Darwin had collected numerous specimens of sea and island life and had made many observations of plants and animals in their natural environment. He documented the relationships between the environment and the structures and functions of plants and animals that gave them the ability to survive and thrive in such environments. The careful observations he made on plants and animals caused him to realize that each species had its own "niche" in the environment. "Niche" is a combination of the role, function, and place of an organism in the environment. Darwin's train of thought went like this: • • a species survives when enough of its members are adapted to the niche in which they live. members of a species are adapted because they have special anatomy and function that fits the niche specifies what it takes for an animal to survive in that particular niche. new species can emerge if genetic change occurs, as by mutation or gradual accumulation of the "right" genes that make the descendants fit for an available niche.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Why It Matters What Was Important About Darwin's Discovery? Continued Thus, the niche exerts a selection pressure. Only individuals that have genes that make them fit and adapted to the niche can survive. If only a few members of a species are adapted, the species may not survive. But, you may say, how can complex animals and plants appear from mere random chance events? Nothing as complicated as humans could arise by accident or chance. But the effect of natural selection is anything but random. If the selection forces of niches dictate what it takes to survive in the niche, that is hardly random. Not all possibilities are equally likely. The chance for any organism to fill a niche is not 50: 50.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Why It Matters What Was Important About Darwin's Discovery? Continued Even if genetic mutation is purely random (which is probably not the case), natural selection is not random. For some animals and plants, there is zero likelihood that they can survive in a particular niche. Cows can't live in the water. For other types of organisms that have the right combination of genes, the chances can be much higher, even a 100% chance of being adapted to that niche. For example, another mammal, manatees or “sea cows, ” can live in the water. Their anatomy, physiology, and behavior work in that environment. If several species can survive in the same niche, then competition among species becomes a factor. One or more species may be forced out of the niche by individuals who are more fit for that environment. None of this is random.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Why It Matters Why Scientists Think Natural Selection is So Important For scientists, natural selection is a unifying principle that is consistent with all biological knowledge. Natural selection is the only possible mechanism, based on observable evidence, that can explain how the environment can determine which species can survive and which cannot. Life is precious and fragile. Adapt or die. Anything that we humans do to the environment can change natural selection forces and thus create the risk of driving species into extinction. As we have seen with dinosaurs, changing the environment may open previously occupied niches that can be occupied by new species that have the genes that can make them fit for that environment.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know
How We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters Galapagos Islands – Nature’s Laboratory The Galapagos islands, a group of about 21 islands, are located about 900 km off the coast of Ecuador. Charles Darwin studied the plants and animals in these islands in 1835. What Darwin saw was a dazzling array of niches and hundreds of species that showed special adaptations for their niche. He studied his notes and drawings for some 25 years before finally publishing his classic book, The Origin of Species. How We Know What We Know Story Time Activities Self-Study Game Post-Test Satellite view of a volcano on one of the Galapagos Islands. Photo from NASA
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know Galapagos Islands – Nature’s Laboratory Darwin described many niches and their species. Among his most famous objects of study were "Darwin's finches. " These were 13 different species of finches - found on only one of the islands - that had very specialized beaks that corresponded to the requirements of the food they ate. For example, one species had a large parrot-like beak for cracking seeds. Another had a delicate beak used to grasp insects. Another had a plier-like beak used to hold twigs in order to probe trees for termites and other wood-boring insects. Clearly, a bird of a given species would have trouble getting enough food if it had the wrong kind of bill for the food it preferred to eat. Observations like this led Darwin to develop his theory of natural selection. What We Know Story Time Activities Self-Study Game Post-Test How We Know The sketches on the left are Darwin’s own. The pictures on the right show the finches’ beaks are adapted for their diet.
Natural Selection Ecosyste ms: Natural Selection How We Know Galapagos Islands – Nature’s Laboratory Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test You can learn about the different plants and animals on Galapagos today by clicking here. Research still goes on in these islands. For more information, click here. Darwin's ideas have gained strength over the subsequent decades of scientific research. Since then, all that we have learned about geology, genetics, and comparative anatomy and physiology in plants and animals has only served to add further weight to the logic of Darwin's insights.
How We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How Scientists Know the Earth is Billions of Years Old Scientists say "seeing is believing. " Most scientists believe that the earth is about 4 billion years old and that the universe is much older than that. Non-scientists say "believing is seeing. "
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know How Scientists Know the Earth is Billions of Years Old Clearly, it would take a VERY long time for natural selection forces to favor emergence of species that are fitted for the kind of environment they live in. The evidence for the age of the earth includes: • The theory of plate tectonics describes the large-scale motion of seven large plates and several smaller plates of the Earth’s lithosphere over time. This process began some 3. 5 billion years ago. Large supercontinents have assembled and broken apart over the history of Earth. Pangea is one supercontinent that began to break apart about 175 million years ago (notice for example how Africa seems to fit into South America). This theory is supported by matching radioactivity, magnetic fields, minerals, and rock formations in the pieces of continents. Given the rate at which the earth’s plates move today, all this would take millions of years to occur. Source: USGS
Natural Selection Ecosyste ms: Natural Selection How Scientists Know the Earth is Billions of Years Old Cont’d • Deposits of fossils from different life forms appear in geological sediments and earth layers that would take millions of years to form from erosion and deposits of dust. Fossils are formed from sediments in lakes and marshes. Successive layers containing different fossils accumulate over thousands of years. Later, erosion can scrape or carve canyons to reveal the layers. Remains of ancient human species are found deep in layers of Olduvai Gorge in Africa. Radioactive dating indicates that these layers are many millions of years old. • Radioactive dating (see page on Radioactive Dating) shows numerous extinct plants and animals that lived millions of years ago. Fossils of these life forms indicate that they became extinct at different times, separated by millions of years. • Numerous transitional forms of life have been found among fossils. Examples: lung-breathing fishes with primitive forelimbs, extinct whales with hind limbs, birdlike dinosaurs, and fossils of hominins with smaller brain capacity than today's humans. Click here for a timeline of human evolution. • Transitional forms are not an absolute requirement. Mutations in a few key genes can produce dramatic changes in life form in one generation. See our Story Time for the Populations unit. Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know An artist's depiction of the fossil fish that bridges the evolutionary gap between animals of land sea. Credit: Zina Deretsky, National Science Foundation
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know How Do We Know There is Natural Selection? One way that we find out about natural selection is to see how humans change animals by selectively breeding them to increase the numbers of individuals that have certain traits. For example, if a farmer keeps the calves from his cows that give the most milk, eventually his herd will have more high -producing cows in it. 1. Humans perform selective breeding practices for crops, farm animals, and pets. Sometimes this is called “artificial selection” because instead of natural selection occurring, humans are dictating which genes are passed from generation to generation. 2. Humans can also affect natural selection unintentionally when they alter the environment or introduce plants and animals into new niches. 3. We can see niches and can see that niches and their occupants change - even in our lifetime. Some examples of this are discussed more thoroughly in the Population Balance unit.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know How Do We Know There is Natural Selection? Continued Repeated use of antibiotics, for example, imposes a selection force. Those members of a species that just happen to have genes that impart resistance to an antibiotic have a selective advantage. When confronted with antibiotic the susceptible bacteria die, but a few will survive because they just happen to have genes that protect them. When the survivors reproduce, the genes that made them resistant proliferate in the population. Eventually, the antibiotic does not work anymore because all of the bacteria are resistant to it. A similar process has been observed to be occurring today with insecticides.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know Radioactive Dating Some chemical elements are radioactive. They decay at a constant rate, giving off energy (like beta particles or gamma rays) and turning into a "daughter" compound that is slightly different and does not decay. Such is the case with carbon. Some carbon atoms are radioactive and decay at a fixed rate to become stable nitrogen. Living things and materials made from living things, such as bowls and decorations carved from wood, contain atoms of carbon. If you measure how much of this radioactive carbon is decaying now, you can use the known rate of decay to calculate how much radioactive carbon was incorporated at the time the living thing died. Willard Libby had worked with the team making the nuclear bomb during World War II, so he was an expert in nuclear and atomic chemistry. After the war, he became very interested in peaceful applications of atomic science. He and two students were the first to measure the "half-life" of radiocarbon. The half-life is the time it takes for half the radiocarbon in a sample of bone or shell or any carbon sample to disappear. Libby calculated that it takes 5, 568 years for half the radiocarbon to decay. After twice that time (about 11, 000 years), another half of that remaining amount will have disappeared. After another 5, 568 years, again another half will have disappeared. You can work out that after about 50, 000 years, all the radiocarbon will have disappeared. Therefore, radiocarbon dating is not able to date anything older than about 50, 000 years.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know Radioactive Dating So how do you measure age, of a fossil, for example? Radioactive carbon decay gives off a "beta particle, " which can be detected and counted. Thus, you measure how many beta particles are being given off. Back-calculating using the known half-life rate of decay lets you determine the age of specimen being tested. A dead animal or plant cannot acquire new radioactive carbon. We know that the method works for relatively young objects because results agree with ages of things that have a historical record. Radiocarbon dating is reasonably accurate over a period of about 50, 000 years. For older materials, other radioactive methods have to be used. For more details on the method, click here. To illustrate why carbon dating is an important tool, let us consider what it tells us about human origins. Distinctly human skulls and bones have been found that have been dated at about 1 million years old, and human-like fossils and their tools have been dated at 2 million years old. One recent find of five skulls is dated at 7 million years. These were clearly human-like skulls (not ape), but they had small brain capacity (we know they were from adults because the skull bones were fused). Canyon-forming rivers have carved out the earth sediments and exposed primitive human skulls. The sediments have been dated with ages similar to those of the skulls. See sites on Africa's Olduvai Gorge.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n How We Know Fossils Ever been to the petrified forest in Arizona's national park? If you have, you would have seen whole forests that have become fossils. Some of these fossils are so well formed that you can determine the age of trees the same way we do on a tree that we cut down. The number of rings around the trunk tell us how old the tree is. Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Source: NPS
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test How We Know How are Fossils Formed? If trees or other plants or animals get buried under sediment before they decompose, ground water can dissolve silica in the soil above and carry it into the dead plant or animal. The silica will crystallize in the dead plant or animal and stay trapped there. Thus, the detailed structures are revealed and preserved. When rivers cut through the sediment and wash it away, fossils become uncovered and you can find them. So how do fossils relate to Natural Selection? If nothing alive today resembles a fossil we assume that the species is extinct. Fossils show us that many species (perhaps as many as 90% of all species) no longer live. Why did they become extinct? Something must have forced them out of existence. Forces of nature seem to be the obvious answer. These species might have • • Lost their niches Failed to survive when niches changed Lost out to competing or predator species Died from disease or some natural disaster
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know Niches Every species needs its own "niche. " This term is a combination of the role, function, and place of an organism in its environment. The extinction of dinosaurs about 65 million years ago opened many niches for new occupants that could become new species. When dinosaurs became extinct, the niches in which they lived became available for other species. Natural selection especially favored the existing small mammals because they were smarter than most other species and their warm-bloodedness allowed them to thrive in many climates. Jungles, like this one in Costa Rica, provide many niches for many plant and animal species. What We Know Story Time Activities Self-Study Game Post-Test What We Know What would happen to these niches if we chopped down the trees in the jungle? . . . Or if there was a drought that dried up the swamps and river?
Natural Selection Ecosyste ms: Natural Selection What We Know Do you think there would be as many niches in the desert? Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Niches come in surprising forms. Here, a crab lives inside a shell underwater.
What We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Life Develops Over Time Radioactive dating indicates that our earth formed about 4. 5 billion years ago. How long is 4. 5 billion years? One simple way to make the numbers easier to understand is to make 4 billion years equal to one year on our calendar. The table below* shows the approximate dates of the earliest known fossils of various kinds of plants and animals. *Data taken from The Extraordinary Story of Life on Earth, 1996. Prometheus Books. Date Event Jan. 1 (4 B Earth forms from asteroids, star debris. yrs) Jan. 5 Earth cools. Continuous rain. (3. 8 B) Feb. 14 Bacteria appear. (3. 5 B) May 16 Continents move. Huge varieties of bacteria. (2. 5 B) Aug 24 Photosynthetic bacteria make oxygen (1% of (1. 4 B) air). Ozone layer protects earth from UV. Sept. 10 Oceans form. (1. 2 B) Sept. 28 (1 B) Single cell animals appear in oceans. Oct. 16 Colonial animals appear (coral). (800 M) Oct. 27 Sponges appear. (700 M) Nov. 5 7% oxygen in air. Jellyfish. (600 M) Sexual reproduction. Origin of nervous systems. Nov. 8 Continents broke off, began drifting around the Date Event Nov. 27 (380 M) Insects appear. (370 M) Vertebrates and fish appear. Nov. 29 (355 M) Amphibians appear. Dec. 3 (310 M) Great forests, swamps. Birds appear. Dec. 5 (280 M) Reptiles appear. Dec. 9 (280 M) Dinosaurs appear. Dec. 23 (85 M) Flowers (sex in plants). Dec. 25 (65 M) Dinosaurs become extinct. Dec. 26 (63 M) Small mammals proliferate. Dec. 28 (35 M) Huge mammals appear. Dec. 31 7: 30 PM Primitive humans appear. (2 M) Dec. 31 11: 50 PM Modern humans appear.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know Life Develops Over Time Fossils have been found for a few small mammal species that lived at the same time as dinosaurs. Selection forces allowed certain animals to survive that had genes for new variations in anatomy, functions, and brain power. Some of these changes helped certain types of mammals to occupy special niches that they were accidentally adapted for. It was as if Nature were selecting certain species to survive. Just as dinosaurs were selected against by Nature when their niches went away, new unoccupied niches selected for new species that had the right characteristics to thrive in the niches. One apparently useful adaptation was brain power. Humans, having very complex brains, appeared last. Fossils of human skulls indicate that there were pre-human species over a million years ago that had skulls much more like our skulls than those of ancient or modern apes. Modern human skulls appear in the fossil record only in relatively recent times, and historical indications of abstract thinking (such as art, domestication of animals, and agriculture) apparently began about 10, 000 years ago.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know Simple Virtues Simple life forms are more likely to exist just because they are simple. Bacteria were the only life forms found in the oldest known fossils (3. 5 billion years ago). Bacterial fossils are hard to find because they are so small and do not have hard structures. But spores and blue-green algae are common fossils because they have a hard cell wall that is more easily preserved as fossils. Bacteria have always dominated life on earth and do so even today in the sense that they have more individuals and live in practically all environments, including hostile environments in frozen areas, in hot springs, and deep within the earth and deep in the ocean. Many thermophilic organisms live in the hot springs of Yellowstone National Park. Morning Glory Pool during winter NPS Photo
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know Complexity is Inevitable We expect life forms more complex than bacteria because life can only evolve in that direction - it can't get any simpler. The late professor Stephen Gould (see Story Time in Populations) believed that evolution is not driven toward progress nor toward the creation of higher forms such as humans. Maybe higher forms just happen because that is the only direction in which evolution can occur. But that is not true. Many parasites appear to have evolved from higher forms by having traits that enabled them to thrive as parasites. What Dr. Gould missed was that there is an advantage to having complex nervous systems, which has put humans at the top of the mammal group and insects at the top of the invertebrates. These advanced forms were not accidents. Rather, they are at least partly predictable because complex nervous systems provide great advantages to occupy multiple niches and to defend against predators.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know The Virtues of Sexual Reproduction Sexual reproduction increases the spread of gene mutations and gene variability. For higher animals and plants, sexual reproduction is essential for a species to "arrive" and to survive. An emerging species must populate its niche lest that niche get populated by some other species. We even define a species in terms of a group of like animals (or plants) that are sexually isolated. To scientists this means that members of one species cannot breed with members of another species and produce offspring that can reproduce with that same group.
What We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Darwin’s Theory In his famous book, Darwin stated that the idea of evolution was well understood by many others before his time. He reviewed the evidence that geologists and biologists had presented over many preceding decades. What was new was Darwin's explanation that natural selection caused evolution. The basic idea was that the niches provided by Nature preferentially selected those emerging life forms that had inheritable traits that made them adapted to live in those niches. Here, we show the value of camouflage, an adaptation that allows the octopus to hide safely among the coral. Self-Study Game Post-Test Source: NOAA
Natural Selection Ecosyste ms: Natural Selection Darwin’s Theory Continued The essence of Natural Selection can be summarized as follows: • Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know • • Heredity is the passage of genetic instructions from one generation to the next generation. Individuals in a population are genetically varied. Reproduction produces many more offspring than are needed for a species to survive. The genetic traits that are passed on to new generations are those that are best adapted to the available niches. As each generation reproduces, the incidence of the favorable traits gradually increases and comes to dominate the population. That population may become genetically isolated, thus forming a new species.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Major Changes in Selection Forces In the long history of Earth, major catastrophes have occurred: ● Introductio n ● Why It Matters ● How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know Volcanic eruptions so massive that the entire earth was swamped in carbon dioxide and turned into a world-wide greenhouse World-wide cooling that caused much of the earth to be covered in ice Earth-shattering collisions with asteroids (one of which probably wiped out the dinosaurs) Such catastrophes must have created drastic changes in selection forces. Most species became extinct, and those that survived found a world of new niches and opportunities. Mutations that at one time would hinder a species from surviving in a niche often found a welcoming environment. New species could appear so rapidly that they might not have left a fossil record of intermediate forms.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know Major Changes in Selection Forces Continued Climate has always been important. Dinosaurs needed a jungle-like environment. Dinosaur fossils have been found near the North Pole, suggesting that millions of years ago, the earth's axis tilted different to make the Pole warm, at least during part of the year. Few species thrive in very cold climates. The simplest successful organisms are millions of species of bacteria that occupy virtually all niches on earth, including such hostile environments as Antarctica and hot volcanic beds at the bottom of the ocean (click here or here for more information on organisms that live in extreme niches). Collection of ice samples in glaciers has revealed that certain bacteria are thriving in such a hostile environment.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Niches for Early Life Forms All scientific evidence supports the view that life began in the sea. When the seas receded and bare land appeared, a new range of niches became available for evolving plants and animals alike. The oldest land fossils are of plant species that are now extinct. The presence of plants created selection opportunities for land animals, which now had something to eat. And then animals that ate other animals appeared because they now had something to eat. But what about breathing air? Air provided a wonderful opportunity for species that could use the oxygen created by the plants. Fish were and are adapted to absorbing the 0. 5% of oxygen in water. But any animal that can breathe atmospheric oxygen has access to 20% oxygen. What We Know
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know Niches for Early Life Forms Continued Today, some living relics of the first land species of animals have been found. These are so-called "lung fish. " They are true fish, relying on gills and living in water. But if they become stranded when their ponds and creeks dry up, their little lungs can still keep them alive. Also, their pectoral fins are primitive limbs, and they can squirm their way back to water. Scientists think that relatives of these lung fishes gave rise to the first true amphibians, like frogs and salamanders, because the bone pattern in the limbs of fossils or early lungfish show a strong resemblance to the limbs of reptiles and mammals. Individuals that happened to have better limb bones and more efficient little lungs are thought to have accumulated in their populations because they had a selective advantage of being able to thrive on land. Amphibians were the first land animals, being able to thrive in both water and on land. Reptiles soon appeared because they could leave the sea entirely (although some reptile species were sufficiently adapted to life in the sea that they still exist today - like the turtle).
What We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Is Evolution Occurring Today? You bet. Modern genetics allows us to map changes in genes of many species and to document the degree of genetic similarity among species and which genes change over time. Genetic scientists crank out new species of fruit flies almost every day. Bacteria adapt to antibiotics and turn into species that are resistant. Humans have domesticated plants and animals in just the last six thousand years. There are examples of species being created in our time. Of course, these are examples of artificial selection, not natural selection. Either way, heritable traits of descendants are changed by the force of selection.
What We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Is Evolution Occurring Today? Continued We change and even destroy habitats. Can you think of examples? We move species into new habitats that they would not have access to without being moved by humans. Can you think of some examples? But these are signs of "micro -evolution, " not the macroevolution of whole new groups of plants and animals. Characteristic microevolution MACROevolution Scale Looks at small-scale changes at the gene level that contribute to evolution Studies large-scale changes that contribute to evolution Relationship to species at species level above species level Changes occur Within a species Between species Time period Several generations Much longer Causes Mutations, selection, gene flow 1, and genetic drift 2 Extended microevolution Data Based on molecular experiments Based on fossil data 1 transfer 2 change of genetic info from one population to another in allelic frequency by chance within a population
Natural Selection Ecosyste ms: Natural Selection What We Know Is Evolution Occurring Today? Continued Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Extinction is a natural phenomenon. It occurs naturally at a rate of about one to five species per year. It now appears that about 12 species are going extinct every day. Humans change the balance of selection forces in nature by forcing many species into extinction. Between 1600 and 1900, humans eliminated about 75 bird and mammal species. Another 92 bird and mammal species were eliminated between 1900 and modern times. Remember, that humans have affected evolution mostly in the last few thousand years. Macroevolution of new species involves the force of natural selection operating over vast stretches of time, such as millions of years.
What We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Selection Forces on Humans What is the selection force that gives humans such remarkable brains? Clearly, early humans had a major selective advantage if they could occupy many niches, compete with other species for food, and avoid becoming food for other species. Their complex brains made these things possible. Another somewhat frightening thing to consider is that humans have always killed each other, sometimes for food, but more often out of just plain meanness. No other species does that against its own kind on the scale that humans have. All this killing may have created selective forces for being smart because being smart gives advantages in war. But humans also are smart enough to cooperate and work together to help the species survive. Early huntergatherer cultures left plenty of evidence that they worked as teams to find food.
What We Know Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Selection Forces on Humans Continued We cannot be certain of the selective forces acting on humans today because we can't look back from a million or so years from now. But let us consider some possibilities: ∙ ∙ Worldwide famine could act as a selective force that favors the survivors whose bodies used food more efficiently or who were so aggressive that they took food resources from the less fortunate. Worldwide disease epidemics could favor people who were more resistant to disease. Worldwide pollution could favor people who resist the damaging effects of environmental hazards (But remember that cancer develops late in life, after successful reproduction has occurred). World war could favor people with traits that lead to success in war (such as intelligence or aggressiveness). Can you think of others?
Natural Selection Ecosyste ms: Natural Selection Creationism/Intelligent Design vs Evolution ● Pre-Test Introductio n ● Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test What We Know ● Evidence for natural selection seems compelling. Theory of Evolution arises from those facts and unifies our scientific understanding of life at all levels: molecular, cellular, organismal, and ecosystem. Theory of Evolution takes no position on God or spiritual beliefs. These are beyond the realm of science and not testable by the methods of science. "Creationism" or "Intelligent Design" are alternative ways to think about origin of species, but they are not scientific theories. Scientific theories are based on observable physical evidence. Theories lead to predictions that can be tested through research. A large list of links to Web sites dealing with various aspects of evolution can be found here. The official position of the National Science Teaching Association is found on their website.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime Thomas H. Huxley (1825 -1885) They called him “Darwin’s Rottweiler. ” After Darwin, an Englishman, announced his Theory of Evolution, the idea came under vigorous attack particularly in the press and by the Church of England. Darwin was a shy man, not prone to hostility and public debate. He and his theory needed a champion. Huxley became that champion. Darwin, along with Alfred Wallace, created the explanation for "evolution, " but it was Thomas Huxley who sold the idea to the world.
Storytime Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Life in the London Slums Thomas Huxley grew up at a time when England was in the worst depression of the century. Few people there had jobs. He lived in a squalid area of East London, characterized by fetid alleys, bars, and dance halls. Many people there were starving. Thomas was an apprentice to a druggist in that part of town. People there were constantly begging him for medicine and for help for their misery. Thomas was high strung and sensitive, and their misery left him scarred for life. He spent his nights in a tiny room by the shipping port. There he would escape the misery around him the only way he could -- by dreaming of better things. A slum today. Slums built along rivers that are constantly polluted by urban waste, agricultural runoff, and chemical effluents. In 19 th Century London, slums were run-down parts of the city. Slum in Ecuador. Source: HUD USER
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime A Strange Family Unlike Darwin, Thomas had no fortune to inherit and no family tradition to uphold. His father was considered intelligent, but he was poor. He was a math teacher in a minor public school in a country town west of London. Young Thomas was noted for having a quick temper and for being stubborn, like his father. His only obvious talent was drawing. Many years later this talent for drawing would serve him well, as he drew anatomical details of many new species of animals. Photography was not available in those years. Thomas’ mother was a lower-class "Cockney” and was 40 years old when she gave birth to Thomas, who was her sixth and last child. She is said to have "lightning intuition. " "Things flash across me, " she would say. Thomas had great affection for his mother but little for his father. Family life was strange. Thomas barely knew his siblings because they were all much older. He did not like his brothers; they were too much like him - intensely selfish. He was alone a lot. His temper added to the problem of making friends. Years later, someone described him as "one of the most secretive and thin-skinned mortals in the world. " Tom got most of his nurturing from his sister, Lizzie. She helped Tom acquire religious training and helped him learn some French and German. Tom developed an interest in the German philosopher, Goethe.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime A Strange Family Continued He first began attending the small school where his father taught when he was eight years old. He was there for two years, and that was all the formal education he ever had. He remembered nothing, except whipping the school bully. The school enrollment had fallen so much that his father had to quit because the family could not live on his income. The family moved to Coventry, where his grandfather ran an old country inn. This was an area of England where silk-weaving was the main business. Children at the age of six went to work weaving silk. The village was also populated by coal miners who generally lived in filth. The village was full of pregnant 16 -year old girls destined to a life of despair and drudgery. The people were clannish and did not accept outsiders like Thomas and his family. The family was still poor, and there was no money for Thomas’ education. Thomas escaped into a fantasy world: it was the only bearable place to be. He became cynical and sad about the real world. His father did have books, since, after all, he was a schoolteacher by trade. These books became Thomas’ outlet of escape.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime Child Labor The real-world still made its demands on Tom. All children in those days had to become apprentices. Weaving silk, working coal mines, or even working in the new steam factories in town were not for Tom. He was interested in philosophy. The closest thing he could find was medicine. So he became an apprentice to John Cooke, a "medical doctor" who was a boyfriend of Tom’s sister. Cooke overwhelmed Tom with the realities of human medicine. At the age of 13, Tom dissected naked human cadavers. It was emotionally shattering. He could not stand it. His family sent him to a friend’s farm that took him back to innocence and recovery. Religious controversy surrounded Coventry. Tom pondered the question of how God’s love could square with all the poverty and misery of so many around him. He also realized the corruption in the Anglican Church, which had become embroiled in the politics of ruling the government of the whole country. The small-mindedness of Coventry drove Tom to follow his two brothers-in-law to London at the age of 15. Brother-in-law Cooke apprenticed Tom to a low-life doctor named Thomas Chandler in the East End.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime Self-improvement, the Path to Power Medical education in those days was corrupt. Access to education and privilege were given on the basis of social status, not on talent. Many medical doctors were little more than what we would call "quacks. " But reform was brewing. Indeed, reform was brewing on all fronts in English society. People wanted benefits from the new industrial age, not misery. Social injustice had become so bad that it could no longer be ignored. Tom became inspired by such realization, and he dedicated himself to learning so that he too could participate in this renewal of England. Night after night, after all day of making medical rounds in the slums, Thomas would study books on his own. He read history, philosophy, Latin, Greek, chemistry, physiology, and physics. He pushed himself harder and harder. He regarded self-improvement as the path to power.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Medical School at Last When he thought he was prepared, he moved in with his sister Lizzie and family in a part of town with a medical college. He got loans from his medical-doctor brothers-in-law to enroll in an inexpensive medical school. Professors and students alike came from backgrounds not too different from that of Thomas. It was not Oxford or Cambridge. Here, rank meant little. Merit counted. But the graduates of Thomas’s medical school did not get the plum assignments of graduates from prestigious medical schools. Tom and his classmates were humble general practitioners who only got access to less desirable practices. Thomas distinguished himself academically in medical school, although physically he looked like a long-haired hippy. Politically, he was a radical. Despite his social background, he was admitted for clinical training to Charing Cross Hospital, which normally accepted mostly the sons of clergy and surgeons. It was a charity hospital, and Huxley was at last able to provide significant help to some of the downtrodden poor of London society. Storytime
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime Medical School at Last Continued Huxley got his first taste of real science from his Charing Cross chemistry professor, George Fownes, who had come from Germany with a fresh Ph. D, which was unheard of at the school. Fownes inspired an interest in experimentation in the laboratory. When not perusing his official formal education, Huxley could be found a mile away at the library of the prestigious Royal College of Surgeons. Here he read inspiring works from the leading German and French scientists of the time. Huxley finished medical school (taking first prize in anatomy and physiology exams) at the age of 20. He was too young to obtain a license to practice, yet he was deeply in debt for the loans that put him through college.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime A New Life at Sea A Navy friend suggested that Tom get a job at sea. He could be a ship doctor. Thomas cut through the red tape and sent a personal letter of application to the Surgeon General of the British Navy. His initiative and academic credentials impressed the General and the Navy top brass. They hired him and assigned him at first to a Navy hospital on land. Huxley had what he needed most: a job and 7 shillings a day to start chipping away at his debt. This was the Golden Age of British imperialism, and the Royal Navy was the "right arm of England. " England was opening new colonies and trade routes around the world. The Navy provided crucial security for England’s ships of commerce. The Navy recognized Thomas’ talent and kept him at work in their medical museum. However, this assignment would not advance a medical career in the Navy. Thomas needed to get ship duty. Then the break of his life came. Ship Captain Owen Stanley had contacted the Admiral to request assignment of a ship doctor with "a flair for science. " Guess who fit that bill? The ship’s mission was to explore New Guinea, a part of the world where animal and plant life had not been studied. Huxley was assigned as ship doctor with Stanley on The Rattlesnake. Huxley was promised full permission to collect specimens of New Guinea’s exotic animals.
Storytime Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test A New Life at Sea Continued Huxley found that life was hard on the long voyages in the small, cramped ship. The Rattlesnake was only 113 feet long, had a crew of 180, and was 44 years old at the time. At least Huxley had officer quarters on board and was free to collect specimens and pursue his scientific bent. However, he had to finance the resources he needed. The Navy provided no books. The ship’s mission was ambitious. It was to secure Northern Australia for British settlement and make the surrounding South Seas safe for British merchant ships. Port landings could be dangerous. They were sure to encounter savages, some cannibalistic. Doing science in such an environment was a challenge. Some of Huxley’s fellow officers shared his interest in science and encouraged him. Drawing of H. M. S. Rattlesnake, the ship where Huxley worked as a Navy doctor. Click here for more.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test The Path of Fame During the long voyages, Huxley dredged the seas to collect specimens. He dissected them and made drawings of their structure. He wrote manuscripts describing their anatomy and function, which he mailed back to England whenever they made port. Many of his papers described unknown species: mollusks, crustaceans, jellyfish, anemone, siphonophore, insects, spiders, and millipedes. He wrote long monographs that summarized large groups of species, such as the Mollusks and Coelenterates (jellyfish). He was at sea, often for months at a time, 12, 000 miles from home in England. It was not unusual for him to wait a year or more to find out if his manuscript had been accepted for publication by the journal to which he mailed it. He knew even less about the stir he was causing back home in England. He was becoming a scientific celebrity because of his rigorous scholarship, beautiful drawings, and the novelty of the new species he was describing. Storytime
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime The Path of Fame Continued Like most sailors, Huxley sometimes cruised the dance halls and crashed private parties looking for a social life. Rather than picking up a few shallow friends, Huxley fell hopelessly in love with an Australian girl, Henrietta. "Nettie, " as he called her, was poetic, artistic, well read, and religious. She likewise loved Thomas but seldom got to see him. He was at sea for as long as eight months at a time. Yet, she remained faithful for years before they finally had enough money to marry. Huxley pressed on, ambitiously pursuing his science. He realized that a Navy life was not for him and Nettie and that science was his way out. He wanted a professorship back home that would allow him and Nettie to make a home in England allow him to pursue "big league" science. He sent some of his papers to influential people such as Sir Burnett, who had initially given him the Navy job, and asked him to submit it to the prestigious Royal Society.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Fame Has Arrived in England Huxley’s ship was finally ordered home to England. Thomas left Nettie behind in Australia, for he had no funds for her transport or to make a home for her. By now, Huxley did have a reputation for excellence. He found some patrons who introduced him around the scientific elite in England. He got some modest funding. Then came funding from the government. Best of all, he was invited to give talks about his research at sea. Huxley discovered that he had a talent for speech-making. He not only started moving in elite scientific circles but he became a great popularizer of science. His talks about mollusks, jellyfish, and the like were enjoyed by non-scientists too. Huge crowds attended his public lectures. You might say that Huxley was like the Carl Sagan of his day. Storytime
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime Fame Has Arrived in England Continued Huxley got assigned to shore duty in England was told he should do his research. Huxley was invited to numerous parties and dinners because he was a science celebrity. Yet he could not find a job outside the Navy. Finally he got his foot in the door when the famous scientist, Edward Forbes, helped him gain paid admission to the Royal Society. He had infiltrated the old boy’s club at last and would soon turn its world upside down. Huxley formed strong friendships with two other great scientists of his day, Joseph Hooker and John Tyndall. Together, they would lead Britain into world prominence in science. They lobbied the politicians and government bureaucrats to create museums, educational institutions, and research universities. They demanded that positions and funding should become based on merit, not political or social standing.
Storytime Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Professor at Last Huxley's membership in the Royal Society was getting him noticed. He gave wonderful talks that amazed such luminaries in the Society as Michael Faraday, Charles Lyell, and Alfred Wallace. At 28 he was a rising star but still could not get a respectable job in science. Finally, at age 30, Huxley landed a lectureship in England. By 1855, Huxley was debt free and brought Nettie to England where they married and began their family. That family included a son, Leonard, who grew up to write many biographies, edit a major magazine, and to sire a famous grandson for Thomas, Aldous Huxley, who wrote the classic book, Brave New World. Leonard was also the father of another famous Huxley, Julian, like his grandfather, became a famous biologist and became active in the politics of science, serving as the first director of the United Nations’ UNESCO. For more information on Julian, click here. Yet another son of Leonard, Andrew Huxley, won the Nobel Prize in 1963 for his discoveries on the mechanism of the nerve impulse. To learn more about Andrew, click here. A proud grandfather holds his grandson, Julian Huxley
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Storytime Changing British Science His work over the next years brought Huxley many positions and much fame. He became rich through his multiple appointments and his numerous magazine articles and books. One book went through seven editions. His writings were profound and cleverly styled yet worded simply enough that even marginally literate people read and enjoyed them. Theory of Evolution that Wallace and Darwin independently proposed was seized upon by Huxley as the one unifying theory that could explain life in the natural world. Huxley not only endorsed theory--he became the primary advocate for it throughout the world. The scientific community was eventually persuaded. The Church of England was another matter, however. They held to what we would call today, "Creationism, " which is based on a literal word-for-word interpretation of the Bible. Huxley was not an atheist, for he knew there was no way to disprove the existence of God. He became an agnostic, a term that he invented. He positioned himself as the enemy of the Church, not so much on religious grounds but because of the divisiveness of all the sects in Britain and because of the privileges that the Anglican Church reserved unto itself. There was no separation of Church and state in the England of his day.
Storytime Natural Selection Ecosyste ms: Natural Selection Changing British Science Continued In the era just after our own Civil War, Huxley and his colleagues (notably, Darwin, Hooker, and Tyndall) reformed the institutions of British science. Huxley believed that science could modernize society and uplift the masses. He was a working-class hero (London cab drivers would refuse his fare). He was a star among the leaders of world science. He sold Darwin’s ideas on evolution to scientists and positioned theory so well that the Church had no choice but to reject it or accommodate to it. According to the New York Times, Huxley had made "ferocious assaults on the structures of Victorian society - religion, class, education -- as he molded Darwin’s scientific revolution into a social engine to overthrow the old order. " Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Huxley when he was President of the Royal Society He had come a long way from the fetid alleys, bars, and dance halls of the slums of London.
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test References 1. Desmond, Adrian. 1999. Huxley. From Devil’s Disciple to Evolution’s High Priest. Perseus Books, Penguin, London. 2. http: //aleph 0. clarku. edu/huxley/guide 1. html Storytime
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Activities
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Click to download an activity ● Student Activity Sheet #1 - Niches ● Student Activity Sheet #2 -Survival of the Fittest ● Student Activity Sheet #3 - Natural Selection and Selective Breeding Activities
Natural Selection Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Self-Study Game
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A-Di Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Glossary adaptation - the process that changes the anatomy, physiology, or behavior of a population that enables them to more effectively live in a given environment. Return to Why It Matters allele - one of two or more alternative forms of the same gene that are located in the same place on homologous chromosomes in the nucleus of the cell. Alleles are usually characterized as being dominant or recessive. allele frequency - the proportion of a gene in a population that is made up of a specific allele. carnivory - the type of predation in which an animal kills and eats another animal for food. Cockney - a person who is native to London, especially the East End of London. Return to Storytime diversity - the number of species in a given location.
Dr-Ex Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters Glossary dredge - to dig out the bottom of a body of water. Many times people dredge ponds to make them deeper or will dredge the ocean looking for new species. Return to Storytime ecosystem - A group of organisms that are interdependent and the environment they live in and depend on. For example, cows grazing on a pasture reflect an ecosystem. It would include the cows and everything that surrounds them, for example, the grass, water, and of course other animals, like the cow birds, army worms, fire ants, soil microbes, and other living things associated with the pasture. How We Know evaporate - to turn a substance from a liquid to a gas. What We Know evolution - a process by which a population of organisms changes over time. More specifically, evolution is a change in genetic frequency over time. Return to Introduction Story Time Activities Self-Study Game Post-Test extinction - when a species of animals dies off completely from the earth. Return to Introduction
Fe-Ge Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Glossary fetid - having a heavy or offensive odor. Return to Storytime food web- a food web represents feeding relationships within a community. It also show the transfer of food energy from its source in plants through herbivores to carnivores. Normally, food webs consist of a number of food chains meshed together. Each food chain is a descriptive diagram including a series of arrows, each pointing from one species to another, representing the flow of food energy from one feeding group of organisms to another. Return to Introduction fossil record - when an animal dies, its bone structure is often preserved when decaying debris or dirt packs on top of it for thousands to millions of years. This is how researchers know what many of the dinosaurs looked like, which led to discovery of how they lived and interacted with the ecosystem. Return to Introduction gene- a unit of heredity which is transferred from a parent to offspring and is held to determine some characteristic of the offspring. Genes are located within the chromosome in the nucleus of cells. Return to Introduction
He-Ra Ecosyste ms: Natural Selection Pre-Test Introductio n Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test Glossary heredity- is the passage of genetic instructions from one generation to the next generation. Return to Introduction | Return to What We Know legume- in simple terms, peas or beans. niche- the role of species based upon its function within a community. This includes the activities of the individuals and how they interact with each other and the habitat around them. Return to Why It Matters | Return to What We Know petrify- to convert organic material into stone through infiltration of water and mineral deposits. Return to How We Find Out radioactive dating - a type of absolute dating that allows scientists to determine the age of certain materials, such as carbon. Minerals decay over time, releasing radioactive rays. Scientists know how long it takes for any isotope to decay. Using this information, we can find how old an object is by determining how much radioactive material still exists in the object. Return to How We Find Out
Ra-Va Ecosyste ms: Natural Selection Pre-Test Introductio n Glossary sea anemone - polyps with brightly colored tentacles. Return to Storytime Source: NOAA Why It Matters How We Know What We Know Story Time Activities Self-Study Game Post-Test siphonophore - jellyfish that are usually delicate, transparent, and colored. Return to Storytime Source: NOAA
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