General Biology 2 Q3 Module 1-4 PDF

12 General Biology 2 Quarter 3: Module 1-4  DEVELOPMENT TEAM OF THE MODULE WRITERS: JULIE ANDREA P. AÑANO, Master Teacher I AYRA PATRICIA S. ALVERO, Teacher III AILINE C. AUSTRIA, Teacher I LOUISE A. FERRER, Ma...

12 General Biology 2 Quarter 3: Module 1-4  DEVELOPMENT TEAM OF THE MODULE WRITERS: JULIE ANDREA P. AÑANO, Master Teacher I AYRA PATRICIA S. ALVERO, Teacher III AILINE C. AUSTRIA, Teacher I LOUISE A. FERRER, Master Teacher I CHRISTIAN MARU G. GARCIA, Teacher III MARGIAN ERICA S. TAGUAS, Special Science Teacher I CONSOLIDATOR: AYRA PATRICIA S. ALVERO, Teacher III LANGUAGE EDITOR: IZAH RIZZA T. FRANCISCO, Teacher II CONTENT JOVILYN G. ENOLPE, Teacher I VALIDATORS: JOSELITO P. GRANDE JR., Teacher II EFREN M. LEYSAN JR., Teacher III COVER PAGE AIRA MARI CON M. AUSTERO ILLUSTRATOR: TEAM LEADER: DR. RAQUEL M. AUSTERO Education Program Supervisor  Module 1 Genetic Engineering Process Most Essential Learning Competencies Outline the processes involved in genetic engineering (STEM_BIO11/12-IIIa-b-6) Discuss the applications of recombinant DNA (STEM_BIO11/12-IIIa-b-7) What’s In Genetic engineering refers to the direct manipulation of DNA to alter an organism’s characteristics in a particular way. It is also referred to as genetic modification which involves the process of altering the DNA in an organism’s genome. Genetic engineering is the process of using recombinant DNA (rDNA) technology to alter the genetic makeup of an organism. GENETIC ENGINEERING PROCESS The genetic engineering process typically entails isolating DNA from one organism (an animal, plant, virus, or bacteria), inserting it into the DNA of another organism, and ensuring that the traits associated with the inserted genes are expressed in the modified organism. Genetic engineering provides a set of techniques to cut DNA either randomly or at a number of specific sites. Once isolated one can study the different segments of DNA, multiply them up and splice them or stick them next to any other DNA of another cell or organism. The process makes it possible to break through the species barrier and to shuffle information between completely unrelated species. There are different ways to get a gene from one species to another or to transform an organism with a new gene. A vector is used to carry the gene into the host, or rather into the nucleus of a host cell. Vectors are commonly bacterial plasmids or viruses. Another method is the shotgun technique also known as "bio-ballistics," which blindly shoots masses of tiny gold particles coated with the gene into a plate of a particular species cells, expecting to land a hit generally in the DNA of the cell. Yet there is a problem, a gene of a certain organism will not work in another organism unless there is a “promoter” with a "flag" that the receiving cells will recognize and give it a go signal to replicate. Such a control sequence should either be a sequence specific to the receiving organism or may be almost similar. Most genetic engineering of plants for example is done with viral promoters. Viruses integrate their genetic information into the DNA of a host cell (such as one of your own), multiply, infect the next cells and multiply. This is possible because viruses have evolved very powerful promoters which command the host cell to constantly read the viral genes and produce viral proteins. Simply by taking a control element (promoter) from a plant virus for instance and sticking it in front of the information block of another species gene, a fish gene for example, therefore you can get this combined virus-fish gene (known as a "construct') to work in a plant. Though often hailed as a precise method, the final stage of placing the new gene into a receiving higher organism is rather crude, lacking both precision and predictability. The "new" gene can end up anywhere, next to any gene or even within another gene, disturbing its function or regulation.  To help explain the process of genetic engineering let us take the example of insulin, a protein, that helps regulate the sugar levels in our blood. Normally, insulin is produced in the pancreas, but in people with type 1 diabetes has a problem with insulin production. Genetic engineering has been used to produce a type of insulin, very similar to our own, from yeast and bacteria. This genetically modified insulin, ‘Humulin’ was licensed for human use in 1982. An illustration showing how genetic modification is used to produce insulin in bacteria. Image credit: Genome Research Limitedhttps://www.yourgenome.org/sites/default/ files/illustrations/process/genetic_engineering_yourgenome.png 1. A small piece of circular DNA called a plasmid is extracted from the bacteria or yeast cell. 2. A small section is then cut out of the circular plasmid by restriction enzymes or referred to as molecular scissors. 3. The gene for human insulin is inserted into the gap in the plasmid. This plasmid is now genetically modified. 4. The genetically modified plasmid is introduced into a new bacteria or yeast cell. 5. This cell then divides rapidly and starts making insulin. 6. To create large amounts of the cells, the genetically modified bacteria or yeast are grown in large fermentation vessels that contain all the nutrients they need. The more the cells divide, the more insulin is produced. 7. When fermentation is complete, the mixture is filtered to release the insulin. 8. The insulin is then purified and packaged into bottles and insulin pens for distribution to patients with diabetes. 4  Genetic engineering in its modern transgenesis form has been around for only 25 years. From its beginnings in the 1970s it has been hotly debated. The table below includes most forms of artificial interference in the outcome of reproductive processes. In addition to these are many social consequences making the overall risk/benefit assessment highly complicated with so many perceived benefits and disadvantages. Summary of techniques affecting the outcome of breeding/reproductive processes Microorganisms Plants Animals Man Manipulation of Selection/gathering of species or varieties of wild Deliberate encouragement of bacterial conjugation, species dating back to the beginnings of farming some specific crosses, e.g. Alexander e.g. interruption by a 10,000 years ago the Great's eugenic intermarriage mechanical process. of Greeks and Persians. See also (Not regarded as genetic Plato's Republic, Book V modification in EU regulations) 459e et seq. Bacterial transduction, Traditional breeding: Traditional breeding: Selection of newborn through i.e. use of phages deliberate crossing of deliberate crossing of environmental challenges, e.g. (as (bacterial viruses) to varieties of species followed varieties of species legend has it) in ancient Sparta. carry bacterial or other by selection with or without followed by selection -- Selection by infanticide. genes or artificial DNA specific environmental i.e. prevention of sequences into challenges, e.g. cold, salty undesirable crosses. bacteria. (Not regarded as soils, diseases. genetic modification in EU regulations) Transformation, the Crosses which cross species Crosses which cross Genocide (e.g. Adolf Hitler's 'final natural tendency of barriers, often necessitating species barriers, e.g. solution') bacteria to take up 'embryo rescue' to construct a mules & hinnies. DNA in their viable plant (e.g. Triticale, a environment, can be wheat-rye hybrid). used to insert DNA Artificial control of pollination, Artificial insemination Artificial insemination, the woman functional as genes into pollen transfer, prevention of with careful selection sometimes selecting sperm stored the bacterial genome self-pollination, covering up of the donor animal. in a sperm bank from a donor with selected flowers to restrict known characteristics (e.g. high resulting in transgenic pollination. IQ). bacteria, e.g. bacteria transformed so as to Male sterilization by anther Sterilizations (e.g. Sterilizations. Compulsory make 'human' insulin removal or insertion of male castration) sterilization of selected individuals for treatment of sterile genes. is still sanctioned legally in some diabetes. (Bacterial countries. transformation is not regarded Polyploidy induction: i.e. Surrogate motherhood as genetic modification in the chromosome doubling, tripling EU regulations) etc with e.g. colchicine. Creation of specific hybrids Manipulation of animal Amniocentesis, chorionic villus to exploit the heterosis embryos in vitro to mix sampling or sampling fetal cells in effect, i.e. hybrid vigor.the cells and create umbilicus wall or maternal blood, F1 hybrids usually do not chimaeras, e.g. the followed by genetic or cytological breed true or are sterile.geep, a mixture of testing, followed by abortion of sheep and goat. undesirable embryos, fetuses. Chemical or radioactive mutagenesis , i.e. creation of mutations in the genes Contraception. Abortion after genetic artificially. testing (e.g. for Down syndrome, trisomy 21). Anther culture in vitro. Many Nuclear transfer Nuclear transfer 'cloning' (illegal in methods of plant reproduction 'cloning' (e.g. Dolly the many countries) for various involve a cloning or vegetative sheep and many other purposes (e.g. stem cell therapy). propagation step on cells or species). Cloning, i.e. induction of twinning the whole organism (e.g. etc by physical manipulation of growing potatoes). embryo prior to implantation. Somatic cell culture, protoplast (plant cell wall chemically removed) fusion. In-vitro fertilization and In vitro fertilization (IVF) In vitro fertilization (IVF, 'test tube' selection (not regarded as usually after induction of babies). genetic manipulation in EU super-ovulation in the regulations). animal. 5  Marker assisted selection, i.e. a genetic marker IVF followed by genetic testing of meaning a particular DNA sequence is used to select one cell of the developing embryo organisms for further breeding. It avoids having to wait followed by implantation in mother or for the organism to reach maturity to see expression of surrogate only if genetically desirable the characteristic linked to the marker. (Pre-implantation genetic diagnosis, e.g. Adam Nash who as an embryo was found to be free of the hereditary disorder Fanconi's anemia and whose umbilical cells were used after he was born to cure his sister Molly of the disease). Creation of transgenic Creation of transgenic Intracytoplasmic sperm or plants, e.g. by switching off animals (e.g. Herman spermatid (immature sperm cell) genes (Flavr Savr tomato); the bull, Tracy the injection (ICSI). insertion of genes from sheep for Gene therapy, i.e. insertion into unrelated species pharmaceutical embryo, child or adult of specific (e.g. Bacillus production, genes (DNA sequences) using a thuringiensis insect toxin xenotransplantation suitable vector (carrier). Potential gene) or even from animals; (transplantation of for so-called 'designer babies'. inclusion of control of animal tissues/organs This includes 'germ line' gene expression genes; insertion into humans) therapy where the descendants of of selectable marker genes or research into the patient would be affected. (e.g. genes for antibiotic diseases (e.g. mice resistance). with certain genes 'knocked out'). Reference: Heaf, David. 2000. A beginner's guide to genetic engineering. Retrieved from http://www.sciencegroup.org.uk/ What’s More Activity 1: Review about the insulin Read and analyze the given paragraph below about insulin. Answer the questions that follow on a separate sheet of paper. Insulin is a hormone produced by the pancreas, which reduces the concentration of glucose in the blood. People, who cannot produce insulin, or not enough of it, are called diabetics. Many diabetics need daily injections of insulin. For many years this insulin has been extracted from the pancreas of pigs, sheep and cattle. Human insulin can now be produced using a technique known as genetic engineering. 1) What is a hormone? 2) Where in the body is insulin produced? 3) What is its function? 6  4) Why are bacteria suitable for use for this purpose? 5) What biomolecules are used to extract a gene from a chromosome? 6) Explain why the same restriction enzyme must be used to extract the gene and open the loop of DNA in the bacterium. 7) What substances should be added to a bioreactor to enable bacteria to grow? 8) Give one advantage of using genetically engineered insulin compared with that extracted from pigs, sheep or cattle. WHAT’S MORE Activity 2: Clone It Refer to the given figure then answer the questions. 1) In the cloning shown in the figure, which sheep is the source of the nucleus in the fused cell? _______________________________________________ 2) Which sheep provided an egg cell? _________________________________ 7 3) Why was the nucleus removed from the egg cell? ______________________________________________________________ 4) Which animal is a clone? __________________________________________ 5) Which two animals are genetically identical? __________________________ What I Have Learned Activity 3: Review the “GE” terms Unscramble each of the clue words. Copy the letters in the numbered boxes drawn below and complete the phrase. 8 PHRASE: By using the 10 given words unscrambled above, define the unlocked phrase. ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ ____________________________________________________________________________ What I Can Do Genetic engineering faces several ethical issues. Explain a significant concern of performing genetic modifications among animals. _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ _____________________________________________________________________ 9  Module 2 Mechanism of Evolution Most Essential Learning Competencies Describe the general features of the history of life on Earth, including generally accepted dates and sequence of the geologic time scale and characteristics of major groups of organisms present during those periods (STEM_BIO11/12-IIIc-g- 8). Explain the mechanisms that produce change in populations from generation to generation (e.g., artificial selection, natural selection, genetic drift, mutation, recombination) (STEM_BIO11/12-IIIc-g-9). What’s In Evolution happens when a heritable trait of a species changes. We can observe this in all modern organisms which have descended from an ancient common ancestor. Evolution is the reason why organisms used to be similar then diversified after billions of years. To study evolution, we must first understand the history of earth and how these major events in history have affected living organisms. In this module, we will try to describe dates in history and living organisms present in each unit of time. We will also elaborate on the selective forces that act in order for evolution to happen and examine the mechanisms of evolution like natural selection, artificial selection, genetic drift and mutation. Geological Time Scale The earth is ~4.6 billion years old while the oldest form of life first existed ~3.5 billion years ago. Geologists and biologists use geologic time scales to describe and scale significant events that happened in the history of earth. This time scale measure time on a scale of four units: (1) epoch is the smallest unit of time which encompasses millions of years, it is grouped into larger units - (2) periods which are combined to make a subdivision called an (3) era which makes up the largest unit in the geological time scale - (4) eon. Take note that the division of units of time is based on occurrence of significant geological events like mass extinction, that is why these units of time vary in length and have no uniform length. The table below summarizes history of earth and life using the four units of time (eon, era, period and epoch): The first unicellular organism was found in fossilized stromatolites (a layered rock). Oxygen revolution refers to the significant increase of O2 in the atmosphere, it had an enormous impact on life, specifically the anaerobic organisms. Later, this led to emergence of aerobic eukaryotic cells. The first eukaryotes evolved from prokaryotic cells which engulfed mitochondria - this process is called endosymbiosis. The Cambrian explosion occurred 535-525 million years ago, this led to the existence of several groups of animals like sponges, cnidarians, and mollusks. 10  This has been a significant part of the history of earth because of the sudden appearance of several animals in a relatively short period of time. Aside from the milestones mentioned above and, on the table, many other significant events happened that affected life on earth like movement of plate tectonics, meteorites hitting earth and mass extinctions. Geologic Time Scale and some important events in the history of life from https://www.campbell.edu/ 11 Definition of Evolution Evolution is descent with modification or simply changes of traits in species over time. But what exactly is being modified or changed? In living organisms this change or modification refers to heritable traits of a species. Heritable traits are encoded by the gene which can be transferred to generations as alleles. Therefore, evolution describes the cumulative changes that happened in a population of one generation to another. We have to remember that evolution doesn’t happen in one generation, it involves changes in heritable characteristics between two or more generations of population. To be more concise, evolution is a change in the allele frequency of a population’s gene pool over successive generations. Let’s take these two scenarios for example, in the first scenario there has been a two-year drought which caused limited plants for beetles to consume. All the beetles in the population have the same chance of survival and reproduction but since there is a limited food supply, the beetles in the population became smaller in size compared to the previous generations. Second scenario is that 90% of the population of beetles possess genes for bright green color and 10% of them have genes for brown color. Since bright green beetles are easily predated because of their obvious color in the photoreception of their predators, after several generations, green beetles become 30% of the population and brown beetles make up the 70%. Now, if we are going to evaluate the two scenarios, the first one is definitely not an example of evolution. The limited food supply is the agent of change not the allele frequency. Smaller body size was not genetically determined, they can regrow to the average size when normal food supply returns. The second scenario is a good example of evolution because the frequency of genes changed due to environmental pressure, we can also consider this as an example of natural selection. In the next paragraph we will discuss mechanisms like natural selection, mutation, recombination, genetic drift and artificial selection lead to evolution. Image Source: https://evolutionbyfl.weebly.com/natural-selection-overproduction- genetic-variation-mutation-differential-survival.html 12 Mechanism of Evolution Fundamental to the process of genetic variation upon which selective forces can act in order for evolution to happen. The table below shows the different the different mechanisms of evolution. 13  What’s More Activity 1: True or False Directions: Identify if the statements are true or false. (10 points) 1. Population refers to the group of all individuals belonging to a species that live in a particular area and interbreed with one another to form offspring. 2. Selective breeding can lead to the domestication of animals. 3. A cow needs to be selectively bred before it produces milk. 4. Over the centuries, artificial selection has served as the primary principle behind selective breeding used to produce new varieties of plants and animals. 5. Genetic change happens due to a failed adaptation. 6. Artificial selection occurs without human intervention. 7. Only animals are selectively bred. 8. Natural selection leads to no noticeable change in the traits of populations. 9. Survival of the fittest accurately describes natural selection. On the down side, artificial selection may cause negative alteration in the population genetics of the species by allowing some traits to dominate in high frequency. What I Have Learned Activity 2: Deepening your Understanding Directions: Answer the questions below. (10 points) 1. What do you think is the importance of evolution in animals? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 2. How is adaptation different from evolution? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 14 3. Do you think natural selection will happen without the changes in the environment? Why? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 4. Do you think artificial selection is beneficial for domesticated animals? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 5. How do you think selective breeding can solve problems in food security? ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ WHAT’S MORE Activity 3: Mindmap Create your own mind map which summarizes and organizes your own understanding of evolution and its evidence/s. 15  What I Can Do Our understanding of evolution today is greatly influenced by Charles Darwin’s On the Origin of Species. Though Darwin’s groundbreaking understanding of evolution was sound and was able to elaborate on many accurate concepts, some mechanisms were still absent and unexplained. Device your own theory of evolution. ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ 16  Module 3 Speciation and Development of Evolutionary Thought Most Essential Learning Competencies Show patterns of descent with modification from common ancestors to produce the organismal diversity observed today (STEM_BIO11/12-IIIc-g-10) Trace the development of evolutionary thought (STEM_BIO11/12-IIIc-g-11) What’s In Species is defined as a population or group of populations whose members share a genetic heritage and have the potential to interbreed. They are genetically compatible, and thus are able produce viable, fertile offspring. When the environment forces members of a species to be reproductively isolated, they are prevented from interbreeding with one another. Through time, such isolation may lead to the formation of a new species. This process in which new and distinct species form in the course of evolution is called speciation. In this lesson, we will investigate the different modes of how speciation occurs, producing the biodiversity that we have today, as well as the ideas of different scientists serving as the foundation of evolutionary thought. Reproductive Isolation Reproductive isolation occurs due to barriers such as difference in habitat, behavior, mating period, etc. which prevent individuals from interbreeding. Through time, their genetic differences grow large enough that they are considered members of different species that cannot interbreed. Reproductive barriers can be classified as prezygotic or postzygotic. Pre zygotic barriers prevent fertilization from occurring. This happens when the species are isolated from each other through differences in habitat, breeding seasons, courtship behavior, morphological incompatibility of reproductive structures or incompatibility of gametes. 17  Pre-zygotic barriers Examples Both are found in the same Two species that occupy geographical area but the apple different habitats within the maggot fly Rhagoletis pomonella) Habitat same area may rarely feeds and mates on hawthorns and Isolation encounter or never come in apples while its relative, the contact blueberry maggot fly (R. mendax), feeds and mates only on blueberries Species with different Western spotted skunk (Spilogale breeding seasons. Their gracilis) mates in late summer while Temporal reproductive maturities do not the eastern spotted skunk Isolation match and breed either on (Spilogale putorius) mates in late different seasons or times. winter. Courtship rituals used to Male fireflies signal their mates by attract a potential mate are flashing light pulses in particular Behavioral unique among species. Only patterns. Only females of the same Isolation members of the same species species recognize the signal, which recognize and respond to prevents interbreeding between two such behaviors. closely related firefly species. The shells of two species of snails in Mating is attempted, however, the genus Bradybaena spiral in Mechanical differences in morphological opposite directions. This structural Isolation structure prevent it from difference prevents successful successfully happening. mating. Red and purple sea urchins have Sperm of one species is not different Gametic able to fertilize the eggs of proteins on the surfaces of the eggs Isolation another species due to and sperm, causing them to bind incompatibilities. poorly to each other, preventing fertilization. 18  If fertilization does occur and a zygote is formed, post zygotic barriers prevent further reproduction from occurring. It is possible that the offspring may not survive and reach reproductive maturity or may be sterile. Post zygotic barriers Examples Salamanders of the genus Ensatina Reduced Fertilization occurs but the occasionally hybridize but the hybrids Hybrid zygote fails to develop past either do not complete development Viability the early embryonic stages. or die. Fertilization occurs and the offspring is viable but is sterile. The chromosomes of Reduced A cross between a male donkey and a the two parent species differ Hybrid female horse is a mule which is able in number or structure, Fertility to survive but is sterile. hence, meiosis in the hybrids may fail to produce normal gametes. In the course of their separation from Offspring from the first- a common ancestor, cultivated rice generation are fertile and strains have accumulated different Hybrid viable, however, mating with mutant recessive alleles at two loci. Breakdown the same generation or with The succeeding generations are small a parent generation makes and sterile due to the many recessive the offspring sterile. alleles that they carry. 19 Modes of Speciation 1. Allopatric In allopatric speciation, the population is divided into geographically isolated subpopulations. Environmental conditions in the two areas may cause the populations to evolve into different species. 2. Sympatric In sympatric speciation occurs in populations that live in the same geographic area. Such events promote polyploidy in which an individual has more than one set of chromosomes. Sympatric speciation can occur when one individual develops an abnormal number of chromosomes, either extra chromosomes or fewer, such that viable interbreeding can no longer occur. Once a species develops an abnormal number of chromosomes, it can then only interbreed with members of the population that have the same abnormal number, Hence, they become reproductively isolated and can lead to the development of a new species. Source: https://image.slidesharecdn.com/22lecture presentation-160322122532/95/biology-in-focus-chapter-22-56- 638.jpg?cb=1458649554 20 Development of Evolutionary Thought 21  What’s More Activity 1: Types of reproductive barriers Directions: Differentiate pre zygotic and post zygotic barriers. Classify the reproductive isolation mechanisms below in the appropriate column. Pre zygotic barrier Post zygotic barrier Description Isolation mechanisms Activity 2: Modes of speciation Directions: Complete the venn diagram below that compares sympatric speciation with allopatric speciation. 22 Activity 3: That’s odd! Directions: Encircle the word that does not belong to the group and explain your reason why. Catastrophism 1. Gradualism Uniformitarianism Catastrophism 2. Evolution Natural selection Darwin 3. Lamarck Wallace What I Have Learned Directions: Explain the phrase, “survival of the fittest”, in relation to Darwin’s theory of evolution by natural selection. ______________________________________________________________________________ ______________________________________________________________________________ ______________________________________________________________________________ __________________________________________________________________ What I Can Do The Philippines is known to be a biodiversity hotspot. Sadly, climate change and anthropogenic activities led to some flora and fauna to be endangered. Fill out the table below with examples of these endangered species and what you can do to prevent it from worsening. Threat to the Endangered species/Reason Habitat/Location What I can do species for being endangered 23  Module 4 Evidences of Evolution Most Essential Learning Competencies Explain evidence of evolution (e.g. biogeography, fossil record, DNA/protein sequences, homology, and embryology) (STEM_BIO11/12-IIIc-g-12) Infer evolutionary relationships among organisms using the evidence of evolution (STEM_BIO11/12-IIIc-g-13) What’s In Biogeography Biogeography is the study of the geographic distribution of living things and the abiotic factors that affect their distribution. Abiotic factors, such as temperature and rainfall, vary based on latitude and elevation, primarily. The composition of plant and animal communities change in response to the changes in these abiotic factors. The geographic distributions of organisms are influenced by many factors, including continental drift theory, which describes the slow movement of Earth’s continents over time. About 250 million years ago, all of Earth’s landmasses is united as one large continent called Pangaea. Pangaea began to break apart and at around 20 million years ago, the continents we know today were within a few hundred kilometers of their present locations. Figure 4.1.Most of the mammal species in Australia are marsupials, while most mammal species elsewhere in the world are placental. Photo by Aushulz, CC BY-SA 3.0 Ecologists who study biogeography examine patterns of species distribution. No species exists everywhere; for example, broad groupings of organisms that had already evolved before the breakup of the supercontinent Pangaea tend to be distributed 24 worldwide. In contrast, broad groupings that evolved after the breakup tend to appear uniquely in smaller regions of Earth. Biologists estimate that Australia, for example, has between 600,000 and 700,000 species of plants and animals. Approximately 3/4 of living plant and mammal species are endemic species found solely in Australia. Fossils are the preserved remains or traces of animals, plants, and other organisms from the past. The age of fossils can range from 10,000 to 3.48 billion years old. The observation that certain fossils were related to a particular rock stratum led to the recognition of a geological timescale. Like existing organisms, fossils vary in size from microscopic, like single-celled bacteria, to gigantic, like dinosaurs and trees. Fossils help us identify when organisms lived, as well as provide evidence for the progression and evolution of life on earth over millions of years. Fossils provide solid evidence that organisms from the past are not the same as those found today; fossils show a progression of evolution. Comparing the anatomies of both modern and extinct species, paleontologists can infer the lineages of those species. This method is most successful for organisms that had hard body parts, such as shells, bones or teeth. The resulting fossil record tells the story of the past and shows the evolution of form over millions of years. One of the best-studied fossils are of the horse lineage. Scientists have been able to reconstruct the "family tree" for horses and their now-extinct relatives using fossils. Changes in the lineage leading to modern-day horses, such as the reduction of toed feet to hooves, may reflect adaptation to changes in environment. Homology We say evolution is a process of descent with modification; wherein some characteristics of an ancient organism are altered (by natural selection) in its descendants over time as they adapt to certain environmental conditions. As a result, related species can share similar characteristics but function differently. Similarity resulting from common ancestry is known as homology. A common example of homologous structures in evolutionary biology are the foreleg bone structure of mammals (Figure 4.2a). These structures do not have the same function but share similar structure based from the last common ancestor. Homologous traits of organisms are an outcome because of descent from a common ancestor. It’s important to note that referring to two structures as homologous depends on what ancestor is being described as the common ancestor. If we go all the way back to the beginning of life, all structures are homologous! The opposite of homologous structures are analogous structures, which are physically similar structures between two taxa that evolved separately (rather than being present in the last common ancestor). These structures evolved independently to serve the same function. Bat wings and bird wings evolved independently and are considered analogous structures (Figure 4.2b). Genetically, a bat wing and a bird wing have very little in common; the last common ancestor of bats and birds did not have wings like either 25  insect pterodactyl bird bat Figure 4.2. (a) Foreleg bone structure of mammals are homologous structures due to same structure shared from a common ancestor but do not necessarily have the same function while (b) wings of animals are analogous structures as they share a common function but do not have similar structure. bats or birds. Wings evolved independently in each lineage after diverging from ancestors with forelimbs that were not used as wings. Vestigial Structures Vestigial structures are referred to as “leftover” structures or remnants of features that served a function in the organism’s ancestors. An example of this are the skeletons of some snakes that retained the remnants of the pelvis and leg bones of their walking ancestors. Another example is the eye remnants buried under the scales of blind species of cave fishes. We would not expect to see these vestigial structures if snakes and blind cave fishes had origins separate from other vertebrate animals. DNA/Protein Sequences Like structural homologies, similarities between biological molecules can reflect shared evolutionary ancestry. At the most basic level, all living organisms share: The same genetic material (DNA) The same, or highly similar, genetic codes The same basic process of gene expression (transcription and translation) The same molecular building blocks, such as amino acids These shared features suggest that all living things are descended from a common ancestor, and that this ancestor had DNA as its genetic material, used the genetic code, and expressed its genes by transcription and translation. The basic idea behind this approach is that two species have the "same" gene because they inherited it from a common ancestor. For instance, humans, cows, chickens, and chimpanzees all have a gene that encodes the hormone insulin, because this gene was already present in their last common ancestor. In general, the greater the difference of DNA between two species, the more distantly the species are related. For instance, human and chimpanzee insulin proteins 26 are much more similar (about 98% identical) than human and chicken insulin proteins (about 64% identical), indicating that humans and chimpanzees are more closely related than humans and chickens. Although similarity in DNA/protein sequences are great for establishing the common origins of life, these features are not so useful for determining how related organisms are. Nucleotide sequences of genes is preferred if we want to determine which organisms in a group are most closely related based from their molecular structure. Embryology Embryology, the study of the development of the anatomy of an organism to its adult form, provides evidence for evolution as embryo formation in widely divergent groups of organisms tends to be conserved. Structures that are absent in the adults of some groups often appear in their embryonic forms, disappearing by the time the adult or juvenile form is reached. For example, all vertebrate embryos, including humans, exhibit gill slits and tails at some point in their early development. These disappear in the adults of terrestrial groups, but are maintained in adults of aquatic groups, such as fish and some amphibians. Great ape embryos, including humans, have a tail structure during their development that is lost by birth. Figure 4.3. Gill slits are a common feature in certain stages of the embryonical development of vertebrate animals. 27  What’s More Activity 1: Which Is Which? Directions: Shown below are images of the skeletal structure of the front limbs of 6 animals: human, crocodile, whale, cat, bird, and bat. Each animal has a similar set of bones. Color code each of the bones according to this key: humerus- blue carpal-green radius- yellow metacarpals-orange ulna- red phalanges- violet 28 Activity 2: All That Is Left Direction: Below are some vestigial structures found in humans. For each, hypothesize what its function may have been. Structure Possible Function Wisdom teeth Appendix Muscles for moving the ear Body hair Little toe Tailbone Activity 3: Match Me Up! Directions: Match the terms in Column A with the correct description in Column B. Write the letter of the answer on the space before each number Column A Column B _____1. Vestigial structure remains of dead organisms _____2. Homologous structures similarities and differences in _____3. DNA sequence amino acid sequences between _____4. Fossil record organisms _____5. Embryology related organisms have the same bone makeup in the early stages of development dogs, pigs, and humans resemble one another structures that have reduced in size because they no longer serve an important function 29  What I Have Learned Directions: Write a statement explaining how evidence of evolution can be used to establish evolutionary relationships in animals. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ What I Can Do In your own words differentiate homologous, analogous and vestigial structures. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ 29  30 Answer Key MODULE 1 MODULE 2 Activity 1 Activity 1 1. A hormone is a chemical substance 1. T secreted by the endocrine glands. 2. T Hormone acts like a messenger, 3. F 4. T which helps in controlling activities of 5. F the body. 6. F 2. Insulin is produced in the pancreas. 7. F 3. Insulin reduces the concentration of 8. F glucose in the blood. 9. F 4. Bacteria are suitable because it is 10. T able to reproduce insulin at a faster rate compared to other organisms. 1. They are all heritable traits that can be passed 5. The biomolecules used to extract a to the offspring. 2. It can be based on the physical traits of the pairs gene from a chromosome is called a since these are the heritable traits they can pass to restriction enzyme. their offspring. 6. 7 and 8. Answers may vary 3. Yes, this is due to the transfer of genetic materials from parents to offspring during reproduction. Activity 2 4. It can be related to the theories that Mendel formulated out of his experiments. 1. Sheep A is the source of the nucleus in the fused cell. 2. Sheep B provided the egg cell. 3. The nucleus is removed from the egg cell because there is already a nucleus taken from Sheep A. 4. The lamb is a clone. 5. The two animals that are identical are: Sheep A and the Lamb. What I Have Learned Answers may vary What I Can Do Answers may vary Answer Key  31 MODULE 3 MODULE 4 Activity 1 Activity 1: Which is Which? Activity 2 Follow color codes for the following bone structures: humerus- blue radius- yellow Activity 3 ulna- red carpal-green catastrophism; metacarpals-orange uniformitarianism incorporates the theory phalanges- violet of gradualism plus the idea that what happened in the past can be observed occurring today catastrophism; natural Activity 2: All That is Left selection is a mechanism by which evolution occurs Lamarck; Darwin and Wallace both explained that evolution Activity 3: Match Me Up! occurs by natural selection. E C B A D What I Can Do Answer may vary What I Learned Answer may vary