EVOLUTION Methods Used in Determining the Age of Fossils Experts make use of several methods to determine the age of fossils. These methods are the following: 1. Relative Dating - This method is used to determine the age of rocks by comparing them with the rocks present in the other layer. The younger sedimentary rock layer is assumed to be found on top and the older rock is found at the bottom layer. 2. Radiometric Dating - This type of dating is used to determine the age of rocks using the decay of radioactive isotopes present among the rocks such as Carbon-14. All organisms have decaying Carbon-14 in them. Plants and animals that are still alive constantly replace the supply of carbon in their body while the amount of carbon14 in their body stays the same. When an organism dies, carbon-14 will start to decay. 3. Carbon Dating- It is used to tell the age of organic materials. Art collectors use carbon dating to determine if a piece of artwork is genuine or not Geologic Time Scale Out of the examinations of layers of rocks and dating of fossils, scientists were able to develop the Geologic Time Scale. This scale shows the major events in the Earth’s history. It also shows the appearance of various kinds of organisms in a particular period of time on Earth. Era, the largest division of the Geologic Time Scale, has the following parts: Precambrian, Paleozoic, Mesozoic, and Cenozoic. Each era is further divided into periods. The Precambrian is a term used to describe the interval of geologic time that extends from the formation of the Earth, around 4.6 billion years ago, to the beginning of the Phanerozoic eon, approximately 541 million years ago. It is the longest span of Earth's history and is divided into three eons: the Hadean, Archean, and Proterozoic. During the Precambrian, the Earth underwent significant changes, including the formation of the first continents, the evolution of the atmosphere and oceans, and the emergence of life. The earliest life forms were unicellular organisms such as bacteria and algae, which appeared around 3.5 billion years ago. The Hadean eon represents the earliest stage of Earth's history, from its formation around 4.6 billion years ago to about 4 billion years ago. During this time, the planet was subject to intense bombardment by asteroids and comets, which caused widespread volcanic activity and the formation of the first oceans and atmosphere. The Hadean eon is named after Hades, the Greek god of the underworld, due to the extreme conditions that prevailed on Earth at that time. The Archean eon followed the Hadean and lasted from about 4 billion years ago to 2.5 billion years ago. It is characterized by the emergence of life on Earth, the formation of the first continents, and the stabilization of the atmosphere and oceans. During the Archean, the first microbial life forms evolved, and the earliest evidence of photosynthesis and oxygen production by cyanobacteria appeared. The Proterozoic eon followed the Archean and lasted from about 2.5 billion years ago to the beginning of the Phanerozoic eon, around 541 million years ago. It is marked by the emergence of eukaryotic cells, the diversification of life forms, and the formation of the supercontinent Rodinia. During the Proterozoic, Earth's climate alternated between ice ages and warmer periods, and the first multicellular organisms appeared. The oldest fossils discovered to date are from approximately 3.5 billion years ago, Precambrian Era. These fossils are microbial mats found in Western Australia and were described in a study published in 2018. The fossils consist of structures that resemble modern microbial communities, suggesting that life on Earth was present and diverse as early as 3.5 billion years ago. However, it is possible that even older fossils exist but has not yet been discovered. AGE OF DINOSAURS The Phanerozoic eon is the current eon of Earth's history, and it began approximately 541 million years ago with the Cambrian explosion, a period of rapid diversification and evolution of complex life forms. The Phanerozoic eon is characterized by the presence of abundant fossil records, and it is divided into three major eras: the Paleozoic, Mesozoic, and Cenozoic. The Paleozoic era lasted from about 541 to 252 million years ago and saw the evolution of many new types of animals, including fish, amphibians, reptiles, and the first insects. During the Paleozoic, the supercontinent Pangaea formed and then began to break apart, leading to the emergence of separate continents. The Mesozoic era lasted from about 252 to 66 million years ago and is often called the "Age of Dinosaurs." Dinosaurs were the dominant land animals during this era, and many other new types of plants and animals evolved. The Mesozoic also saw the rise of mammals, birds, and flowering plants. The Cenozoic era began about 66 million years ago and continues to the present day. It is characterized by the diversification and dominance of mammals, the emergence of humans, and significant climate change. During the Cenozoic, the continents continued to move and separate, leading to the formation of modernday continents and oceans. The Phanerozoic eon is a critical period in the Earth's history, as it saw the evolution and diversification of complex life forms, the formation and separation of continents, and significant geological and climate changes. It provides a wealth of information for scientists to study the evolution and history of our planet. Hint of Evolution from Comparative Another hint of evolutionary concept is from comparative anatomy. Comparative anatomy is the study of the similarities and differences present in the anatomy of various species. It is an important tool that helps to determine the evolutionary relationships between organisms and whether or not they share common ancestors. Meanwhile, anatomical similarities between organisms support the idea that these organisms evolved from a common ancestor. When referring to anatomical structures, they can either be homologous or analogous. 1. Homologous structures - These refer to structures from different species which have similar internal framework, position, and embryonic development. Homologous structures may have the same origin or ancestors but different functions. This type of evolution is called divergent evolution. Divergent evolution is the splitting of an ancestral population into two or more subpopulations that are geographically isolated from one another. The following is an example of a homologous structure: The forelimbs belonging to a dog, man, cat, bat, bird, lizard, and whale are structurally the same, but are functionally different. 2. Analogous structures – The structures of unrelated species may evolve for them to look somewhat the same because the structure has adapted to similar functions. In another words, analogous structures have similar functions but different in origin. In convergent evolution, analogous structures of unrelated organisms from different ancestors developed a similar function. This is one example: The wings of birds, bats, and insects exhibit the same functions. Evidence from Embryonic Development Embryology is the study of the anatomy development of an organism to its adult form. It provides evidence for evolution as embryo formation in widely-divergent group of organisms tends to be well conserved. That is to say, structures that are absent among adults of some groups often appear during their embryonic forms. An embryo is an early stage of development among organisms Due to these manifestations, embryonic development is considered to be very useful when studying the relationship of organisms. Studies have also shown that closely-related species can exhibit similar embryonic development but their adult structures can become quite different later on. Amino Acid Sequence Another evidence for evolution is provided by the biochemical analysis and amino acids sequence of an organism’s DNA. For example, it is clear that the evolution of the new functions of proteins commonly occurs after gene duplications. These types of duplication allow the free modification of one copy by mutation, selection, or drift (changes in a population’s gene pool resulting from chance), while the second copy continues to produce a functional protein. This means that the greater the similarity present in the amino acid sequence, the closer the relationship is among the organisms. Also, organisms with similar structures and biochemical compositions could have probably descended from a common ancestor. To increase your understanding on amino acid sequences and their determining factor to the relationship of organisms, perform the activity in the next section. Theories of evolution attempt to explain how and why evolution occurs. Here are some of the most well-known theories of evolution: 1. Theory of Evolution by Natural Selection: This theory, proposed by Charles Darwin in the 19th century, states that the process of natural selection determines which traits become more or less common in a population over time. Individuals with traits that help them survive and reproduce are more likely to pass on those traits to their offspring, while individuals with less advantageous traits are less likely to do so. 2. Lamarck's Theory of Evolution: This theory, proposed by Jean-Baptiste Lamarck in the 18th century, posited that traits acquired during an organism's lifetime can be passed down to its offspring. Inheritance of acquired traits (Theory of Acquired Characteristics): Lamarck proposed that an organism can pass on traits acquired during its lifetime to its offspring. For example, if a giraffe stretches its neck to reach leaves on a high tree, its neck would become longer, and this acquired trait would be passed on to its offspring. However, this theory has been disproven by modern genetics, which has shown that acquired traits cannot be passed down to offspring through genes. Use and disuse (Theory of Use and Disuse): Lamarck suggested that the use or disuse of a particular body part can influence its development over time. For example, if a bird stops using its wings for flight and instead relies on its legs to move around, its wings would gradually shrink and eventually disappear over time. This theory has also been discredited, as it has been shown that changes in body structures are driven by genetic mutations rather than use or disuse. Progression towards complexity (Theory of Need): Lamarck proposed that all living things have a natural tendency to become more complex and sophisticated over time. He believed that simple organisms gradually evolved into more complex ones through a process of increasing perfection. However, this theory has been challenged by the discovery of many simple organisms that have remained relatively unchanged for millions of years, as well as by the understanding that evolution is driven by natural selection rather than a pre- determined complexity. goal of increasing 3. Modern Synthesis: This theory, also known as the Neo-Darwinian Synthesis, combines Darwin's theory of natural selection with the understanding of genetics that emerged in the 20th century. It posits that genetic mutations are the ultimate source of variation in populations and that natural selection acts on this variation to produce evolutionary change. 4. Neutral Theory of Molecular Evolution: This theory, proposed by Motoo Kimura in the 1960s, suggests that much of the genetic variation within and between species is the result of neutral mutations that do not have an effect on an organism's survival or reproduction. This theory has been supported by molecular studies of DNA and protein sequences. 5. Punctuated Equilibrium: This theory, proposed by Stephen Jay Gould and Niles Eldredge in the 1970s, suggests that evolution occurs in relatively rapid bursts, followed by long periods of stasis. This theory challenges the idea of gradual, continuous evolution and posits that major evolutionary changes happen relatively quickly, in response to major environmental shifts. Charles Darwin JeanBaptiste Lamarck BIODIVERSITY Biodiversity is the variety of life on earth and the essential interdependence of all living things. Short for biological diversity, includes all organisms, species, and populations; the genetic variation among these; and all their complex assemblages of communities and ecosystems. It also refers to the interrelatedness of genes, species, and ecosystems and their interactions with the environment. Levels of Biodiversity 1. Genetic Diversity - different genes & combinations of genes within populations. Genetic diversity is all the different genes contained in all individual plants, animals, fungi, and microorganisms. It occurs within a species as well as between species. 2. Species Diversity- organisms that have the potential to interbreed in nature and produce viable, fertile offspring. A number of different species represented in a given community. Population are a group of individuals of the same species that live in the same area and interbreed, producing fertile offspring. Species diversity is all the differences within and between populations of species, as well as between different species 3.Ecosystem Diversity-variation in the ecosystems found in a region. Ecosystem diversity is all the different habitats, biological communities, and ecological processes, as well as variation within individual ecosystems. Humans depend on biodiversity in countless ways, yet species are being rapidly lost due to human activities. The ecosystem services approach to conservation tries to establish the value that society derives from the natural world such that the true cost of proposed development actions becomes apparent to decision makers. Species are an integral component of ecosystems, and the value they provide in terms of services should be a standard part of ecosystem assessments. Adaptation refers to the ability of an organism to survive and reproduce in an environment. This may involve changes in behavior or physical structure to survive. For example, if we take a street dog (that lives in a tropic place) in Alaska (cold country), it will grow thicker fur to survive cold temperature. Likewise, when a dog in a cold country brought to the tropics, it will shed its fur to adapt to the warm climate. Variation increases the chance of survival. Organisms with the most desirable traits would likely survive environmental changes and gradually become better suited to survive in a given environment; this is called adaptation. The differences among individuals in a population that improve the species' fitness. These adaptations can be physical, chemical, or behavioral. Camouflage and mimicry are two forms of physical adaptation. - Camouflage: Structural adaptation that enables an individual to blend with its surroundings, and that allows an individual to avoid detection by predators. Occurs when an individual “blend” into the environment in the eyes of a potential predator. - Mimicry: A phenomenon in which an individual gains some sort of survival advantage by looking like an individual of another (often more harmful) species. Is present when one species has evolved to look like another species in a way that will provide some advantage. The best-known examples of mimicry are those in which a species mimics another that is toxic or harmful to a potential predator. Camouflage and mimicry are both adaptations because they increase the likelihood of an individual evading predation long enough to reproduce.