Biology Unit 5 Study Guide PDF

Biology Unit 5 Topics Artificial selection Artificial selection is a process by which humans selectively breed plants or animals with desirable traits, resulting in populations that differ significantly from their wild counterparts. Artificial selection is also known as selective breeding. A...

Biology Unit 5 Topics Artificial selection Artificial selection is a process by which humans selectively breed plants or animals with desirable traits, resulting in populations that differ significantly from their wild counterparts. Artificial selection is also known as selective breeding. Artificial selection can be used to enhance specific traits such as size, color, and productivity. Artificial selection has been practiced for centuries, leading to domestication of animals and cultivation of crops. Artificial selection has played a significant role in the development of modern agricultural practices. Cladistics Cladistics is a method in taxonomy that classifies organisms based on shared derived characteristics, emphasizing evolutionary relationships. Cladograms show relationships through branching points. Clades are groups of organisms that share a common ancestor. Derived traits are features that evolved in the lineage. Outgroup comparison helps identify ancestral traits. Descent with modification 'Descent with modification' refers to the idea that species evolve over time, as new traits are inherited from their ancestors. The concept was proposed by Charles Darwin in his theory of evolution. It explains how diversity arises in the natural world. Evolution occurs through the accumulation of small genetic changes over generations. Species that share a common ancestor have similar traits due to descent with modification. Hardy-Weinberg equilibrium Hardy-Weinberg equilibrium posits that in a large, non-evolving population, the frequencies of alleles and genotypes remain constant over generations unless affected by specific forces. Hardy-Weinberg equilibrium is applicable only with five conditions: large population size,  absence of mutations, no immigration/emigration, random mating, and no natural selection. If these conditions are violated, it may lead to evolution. There are two equations associated with Hardy-Weinberg equilibrium: p2+2pq+q2=1, (p+q)^2=1. p represents the frequency of the dominant allele and q represents the frequency of the recessive allele in the population. Microevolution Microevolution refers to small-scale genetic changes within a population over a relatively short period of time. Microevolution is driven by processes such as mutation, natural selection, genetic drift, and gene flow. It leads to changes in the allele frequencies within a population. Microevolution can result in the development of new traits or the loss of existing traits. It is the basis for the concept of adaptation and the diversity of life forms on Earth. Natural selection Natural selection refers to the process by which certain species survive and reproduce more successfully due to advantageous traits. It's often described as 'survival of the fittest'. Based on the theories of Charles Darwin. Genetic mutations play a critical role. Environmental factors heavily influence natural selection. Natural selection and speciation Natural selection is the process by which advantageous traits in a population are passed on, leading to the evolution of new species over time. Variations in species arise due to genetic mutations, environmental factors, and reproductive isolation. Speciation occurs when a group of individuals from a population become reproductively isolated and evolve into a new species. Adaptations are traits that increase an organism's chances of survival and reproduction in a specific environment. Natural selection can lead to the emergence of diverse species with unique traits suited to their respective environments. Phylogenetics Phylogenetics is the study of evolutionary relationships between organisms, including the detection and classification of genetic and morphological similarities and differences. Phylogenetics is important for understanding the evolutionary history and common ancestry among species. It can be used to reconstruct the evolutionary tree of life, showing the relationships between different branches and groups of organisms. Phylogenetic analysis relies on genetic data, such as DNA sequences, and also considers morphological traits and fossil records. The use of computational algorithms and statistical methods is crucial in phylogenetics to analyze and interpret the data. Population Genetics 'Population Genetics' is the study of genetic variations and changes within populations of organisms. Population genetics helps us understand how genetic traits are passed on from one generation to the next. By studying population genetics, scientists can track the distribution of genetic variations and how they change over time. It helps determine the factors that influence genetic diversity within a population. Population genetics is also used to analyze and predict the spread of genetic diseases within populations. Reproductive isolation Reproductive isolation refers to a set of mechanisms that prevent species from interbreeding, ensuring the maintenance of distinct species. Prezygotic and postzygotic barriers contribute to reproductive isolation. It can occur in allopatric, sympatric, parapatric, and peripatric speciation. Mechanisms may include temporal, behavioral, or mechanical isolation. It plays a fundamental role in evolution, contributing to biodiversity. Speciation Speciation refers to the evolutionary process where populations evolve to become distinct species due to genetic, environmental, and behavioral factors. It typically occurs when populations are geographically isolated. Allopatric and sympatric are the two main types of speciation. Allopatric speciation occurs when a physical barrier separates populations. Sympatric speciation occurs without geographical isolation, often through polyploidy or habitat differentiation. Systematics Systematics is the study of evolutionary relationships among organisms, aiming to classify and organize life forms based on shared characteristics and evolutionary history. Taxonomy is a key component of systematics, involving the identification and classification of organisms based on similarities and differences. Phylogenetics uses genetic and molecular data to reconstruct evolutionary relationships and create phylogenetic trees representing the history of life. Cladistics is a method within systematics that analyzes shared derived characteristics to establish evolutionary relationships among groups of organisms. Systematists use both morphological and molecular data to determine the evolutionary history and relatedness of different species. Taxonomy Taxonomy is the science of classifying and naming organisms based on shared characteristics, leading to hierarchical categorization for systematic organization. Taxonomy categorizes organisms into hierarchical groups such as domain, kingdom, phylum, class, order, family, genus, and species. Carl Linnaeus, a Swedish botanist, is known as the 'father of taxonomy' for establishing the modern system of classification. The two main tasks of taxonomy are classification, which groups organisms based on similarities, and nomenclature, which assigns names to these groups. Taxonomy helps in revealing evolutionary relationships among organisms and aids in the identification and description of new species. Key Terms Adaptations "Adaptations" denotes the evolutionary process whereby an organism becomes better suited to its habitat through alterations in physical form, behavior, or physiology. "Adaptations" can broadly be categorized into structural, behavioral, and physiological variants. "Adaptations" help organisms survive and reproduce successfully in their environment. Species that fail to "adapt" adequately can become extinct. "Adaptations" can take many generations to emerge through the process of natural selection. Adaptive radiation Adaptive radiation refers to the evolutionary process where a single ancestral species diversifies into a multitude of species, each suited for different ecological niches. Adaptive radiation occurs when a species colonizes new habitats with different resources and environments. It leads to the emergence of distinct species, each specialized for a specific niche. Adaptive radiation is driven by natural selection and can occur over a short period of time. It is a key mechanism for the rapid expansion of biodiversity on Earth. Allele An allele is one of the alternative forms of a gene that can occupy a specific location on a chromosome. Alleles determine the variations that exist for a particular trait in a population. Each individual inherits two alleles for each gene, one from each parent. An allele can be dominant or recessive, determining its level of expression. Genetic mutations can lead to the creation of new alleles, increasing genetic diversity. Allele frequency Allele frequency refers to the proportion of a specific allele in a population's gene pool. It is calculated by dividing the number of occurrences of a specific allele by the total number of alleles in the population. Allele frequency can change over time due to natural selection, genetic drift, migration, or mutation. High allele frequencies are indicative of a common allele in the population, while low frequencies indicate a rare allele. Changes in allele frequency can lead to evolutionary changes in populations over generations. Allopatric speciation Allopatric speciation occurs when a population is geographically isolated, leading to the formation of new species over time. Geographic isolation prevents gene flow between populations. The isolated populations undergo genetic variations and adapt to their specific environments. Over time, the genetic differences accumulate, causing reproductive isolation and the formation of new species. Allopatric speciation is commonly observed in island populations or due to geographical barriers like mountains or rivers. Anagenesis Anagenesis is a process in which a single species evolves and undergoes changes over time, leading to the formation of a new species. Anagenesis is a form of speciation that occurs without the splitting of a lineage into two distinct species. It involves gradual changes in the genetic makeup of a population over generations. Anagenesis can result from natural selection, genetic drift, or other evolutionary mechanisms. Unlike in cladogenesis, there is no branching or diversification into multiple lineages in anagenesis. Analogous structures Analogous structures refer to organisms having similar structures that serve the same function, but have different evolutionary origins. They are often seen in organisms that live in similar environments and face similar selective pressures. Analogous structures are a result of convergent evolution, where unrelated species independently evolve similar adaptations. These structures provide evidence of adaptation to common environmental conditions rather than common ancestry. Example: The wings of birds and butterflies are analogous structures, as they serve the same purpose of flying but have different origins. Balancing selection Balancing selection refers to a evolutionary process that maintains genetic variation within a population by favoring multiple alleles instead of a single, dominant allele. Balancing selection can include mechanisms such as heterozygote advantage and frequency- dependent selection. Examples of balancing selection include sickle cell anemia and the MHC complex in vertebrates. This type of selection helps to maintain genetic diversity and adaptability within populations. Balancing selection can occur in both stable and changing environments. Biological species concept The Biological species concept defines a species as a group of organisms capable of interbreeding among each other, but not with individuals from other groups. Reproductive isolation is key for defining species. Emphasizes gene flow within a population. May not apply to asexually reproducing organisms.  Challenges arise with hybridization between closely related species. Bottleneck effect The bottleneck effect is a reduction in genetic variation caused by a drastic decrease in population size due to a random event. The bottleneck effect increases the chances of harmful genetic mutations becoming more prevalent in a population. The reduced genetic variation resulting from the bottleneck effect can decrease a population's ability to adapt to changing environmental conditions. The bottleneck effect can lead to an increased risk of inbreeding and genetic disorders in the population. Populations that have experienced the bottleneck effect are more susceptible to disease outbreaks and other catastrophic events. Clade A clade is a group of organisms that includes an ancestor and all of its descendants. A clade is also known as a monophyletic group or a natural group. In a cladogram, a clade is represented by a branch with all the organisms it includes. Clades are used to study evolutionary relationships among organisms. Identifying shared characteristics and analyzing DNA sequences help determine clades. Cladogenesis Cladogenesis is a process in which a species splits into two or more distinct lineages over time. Cladogenesis can occur through various mechanisms such as geographic isolation or genetic divergence. It is an important factor in the creation of new species and contributes to biodiversity. Cladogenesis results in the branching of the evolutionary tree and can lead to the formation of new traits and adaptations. The process of cladogenesis is often studied using phylogenetic trees and molecular data to track evolutionary relationships. Conjugation Conjugation is a genetic process in which two organisms exchange genetic material through direct contact. Conjugation is common among bacteria, allowing for the transfer of beneficial traits. The transfer of genetic material can occur through a specialized structure called a sex pilus.  Conjugation is a form of horizontal gene transfer, increasing genetic diversity within a population. Antibiotic resistance genes can be transferred through conjugation, leading to the spread of drug resistance. Convergent evolution Convergent evolution refers to the process where different species develop similar traits or characteristics despite not being closely related. Convergent evolution is driven by similar environmental pressures and leads to analogous structures. Examples of convergent evolution include the wings of bats and birds, which evolved independently for flight. Convergent evolution can result in the convergence of morphological, physiological, and behavioral traits. Convergent evolution is often seen in unrelated species living in similar habitats. Darwin Darwin is a renowned scientist known for his theory of evolution, which revolutionized our understanding of how species change over time. Darwin's theory of natural selection suggests that certain traits are advantageous for survival and reproduced more successfully. He proposed that all species share a common ancestry and are constantly evolving through small inherited variations. The Galapagos Islands played a significant role in shaping Darwin's ideas, as he observed unique species and variations among the finches on different islands. Darwin's theory had a profound impact on fields beyond biology, including anthropology, psychology, and philosophy. Directional selection Directional selection is a type of natural selection in which individuals with one extreme phenotype are favored, leading to a shift in the population towards that phenotype. Directional selection occurs when the environment changes and selects for a specific trait. This type of selection can lead to the evolution of new species over time. Directional selection can result in the loss of genetic diversity within a population. Examples of directional selection include the evolution of longer necks in giraffes and darker coloration in peppered moths. Disruptive selection Disruptive selection is a process in which extreme phenotypes have a higher fitness than the average phenotype, leading to the population splitting into two distinct groups. Disruptive selection can lead to the formation of new species. It can occur when there are multiple environmental factors favoring different phenotypes. Disruptive selection can increase genetic variation within a population. This type of selection often occurs in heterogeneous environments where different adaptations are advantageous. Divergent evolution Divergent evolution refers to the process where organisms that share a common ancestor evolve into different species due to different environmental pressures. Organisms develop distinct traits and adapt to different habitats. Divergent evolution results in speciation, forming new species. This type of evolution can occur over long periods of time. Divergent evolution can be seen in species with similar anatomical structures but different functions. Evolution Evolution, in essence, refers to the process where organisms develop and diversify from primitive and ancestral forms through successive generations. It's driven by mechanisms such as mutation, non-random mating, gene flow, genetic drift, and natural selection. Charles Darwin is renowned for establishing the theory through natural selection. Evolution explains the origin of species and their ancestral lineage. Genetic evolution and punctuated equilibrium are key concepts within the realm. Fitness Fitness pertains to an organism's ability to survive and reproduce in its environment, signaling its contribution to the gene pool. Fitness can be measured by an individual's genetic contribution to the next generation compared to others. Different species have different traits which increase their fitness. Factors such as competition, variation, and environment affect fitness. Natural selection favors organisms with higher fitness levels, leading to evolution. Founder effect The 'Founder effect' refers to a reduction in genetic variation due to a small number of individuals establishing a new population. Founder effect can cause high frequency of certain inherited diseases in isolated populations. It's a special case of genetic drift originating from a small population size. This effect plays a significant role in the genetic differences seen in different human populations. It can produce random changes in populations' allele frequencies affecting genetic diversity. Gene flow Gene flow is a fundamental concept in evolutionary genetics referring to the transfer of genetic variation from one population to another. It can occur through various mechanisms, including migration or dispersal. Gene flow helps maintain genetic diversity within a species. It can counteract the effects of natural selection and genetic drift. Barriers to gene flow can lead to speciation, creating new species. Gene pool A 'gene pool' refers to the total variety of genetic information within an interbreeding population, species or a group of species. Variety in gene pools promote genetic diversity which is vital for adaptation and evolution. Changes in a gene pool could result from gene flow, mutation, genetic drift, or natural selection. Dwindling gene pool could result in inbreeding, causing potential loss of genetic diversity. Through the Hardy-Weinberg equilibrium, one can estimate frequencies of specific alleles in a gene pool. Genetic drift Genetic drift refers to the change in the frequency of an existing gene variant in a population due to random sampling of organisms. Genetic drift often occurs in small populations. Genetic drift can lead to genetic variation reduction. Genetic drift can cause gene variants to disappear completely. It's one of the basic mechanisms of evolution, alongside mutation, migration, and natural selection. Genetic variation Genetic variation refers to the diversity in gene frequencies, and impacts an individual's phenotype and ability to adapt to its environment. It arises through mechanisms like mutation, gene flow, and sexual reproduction. Genetic variation is essential for natural selection. A population with little variation may be at risk during environmental changes. Genetic variation can be studied through genome sequencing. Genotype A Genotype refers to the genetic makeup of an organism, detailing the specific set of genes it carries. It ultimately determines the potential traits the organism can express. Genotypes are inherited from both parents and unique for each individual. It is represented by letters - capital for dominant traits and small for recessive. Genotypes combined with environmental factors determine the organism’s phenotype, or observable traits. Gregor Mendel’s work on pea plants is fundamental in understanding genotypic variations. Genotype frequency Genotype frequency refers to the proportion of individuals in a population that have a particular combination of alleles. Genotype frequency can be calculated by dividing the number of individuals with a specific genotype by the total number of individuals in the population. Genotype frequency is influenced by factors such as mutation, migration, natural selection, and genetic drift. Genotype frequency provides important information about the genetic diversity and structure of a population. Changes in genotype frequency over time can indicate evolutionary processes occurring within a population. Hardy-Weinberg equation The Hardy-Weinberg equation is a mathematical formula used to predict genotype frequencies in a population that is not evolving. Ensures that allele frequencies remain constant over generations in the absence of evolutionary forces. Requires specific conditions like a large population size, random mating, no mutation, migration, or natural selection. In practice, deviations from Hardy-Weinberg equilibrium indicate that evolutionary factors are currently influencing the population.  Useful for studying genetic drift, gene flow, and natural selection within a population. Heterozygote In genetics, a heterozygote refers to an organism that has two different alleles for a particular gene. Heterozygotes have one dominant allele and one recessive allele. They can express the dominant trait and pass on either the dominant or recessive allele to their offspring. Heterozygotes are carriers of recessive genetic disorders. Heterozygosity increases genetic diversity in a population. Homologous structures Homologous structures refer to parts of different species with similar anatomy due to a common ancestry, despite possible different functions today. They suggest evolutionary relationships between species. They may have different functions due to adaptive radiation. For instance, human hands and bat wings are homologous structures. These structures are a key component of Darwin's Theory of Evolution. Homozygote A homozygote refers to an individual organism that has two identical alleles for a particular gene. Homozygotes can either be homozygous dominant (two dominant alleles) or homozygous recessive (two recessive alleles). Homozygotes are genetically pure and will always produce offspring with the same trait as themselves. In a Punnett square, homozygotes are represented by a single letter (e.g., AA or aa). Homozygosity increases the likelihood of expressing inherited disorders if the allele is a disease-causing mutation. Horizontal gene transfer Horizontal gene transfer refers to the transfer of genetic material between different species or organisms that are not parent and offspring. It allows for the direct transfer of beneficial traits, such as antibiotic resistance, between bacteria. Horizontal gene transfer can occur through three main mechanisms: transformation,  transduction, and conjugation. This process plays a significant role in the evolution of prokaryotes, allowing for rapid adaptation to new environments. Horizontal gene transfer can lead to the spread of virulence genes, contributing to the emergence of new infectious diseases. HOX genes HOX genes are a group of genes that play a crucial role in determining the body plan of an organism during early development. Hox genes are found in many animals, including humans, and are highly conserved throughout evolution. Mutations in HOX genes can lead to developmental abnormalities or disruptions in an organism's body plan. HOX genes are responsible for the spatial organization of body structures along the head-to- tail axis. They are often arranged in clusters along the chromosome, with their order of expression corresponding to their physical location. Hutton Hutton was a scientist and geologist who proposed the concept of deep time, the idea that the Earth is very old and has undergone gradual changes over time. Hutton's work laid the foundation for the theory of uniformitarianism, which suggests that geological processes occurring today also occurred in the past. He argued against the idea of cataclysmic events shaping the Earth's surface, instead emphasizing slow and gradual processes over long periods of time. Hutton's ideas challenged the prevailing belief in a young Earth and were influential in the development of modern geology. His book 'Theory of the Earth' presented evidence for the idea that Earth's history could be explained through natural processes. Hybrid zones Hybrid zones are geographical areas where two different species come into contact and interbreed, producing hybrid offspring with a mix of traits from both species. Hybrid zones can form when barriers to reproduction weaken, allowing gene flow between species. They provide opportunities to study evolutionary processes and the dynamics of genetic mixing between different populations. In hybrid zones, species may exhibit varying levels of reproductive isolation, impacting the gene flow between them. Understanding hybrid zones can shed light on the mechanisms of speciation and genetic  diversity in natural populations. Intersexual selection Intersexual selection refers to the process by which one sex chooses a mate based on specific traits or behaviors, often leading to the evolution of exaggerated features. Female choice plays a significant role in intersexual selection by selecting males with desirable traits. Sexual dimorphism can arise as a result of intersexual selection, leading to physical differences between males and females. Displaying certain behaviors or producing elaborate courtship rituals can enhance an individual's success in intersexual selection. In some species, bright colors or complex vocalizations are examples of traits that may be favored through intersexual selection. Intrasexual selection Intrasexual selection refers to competition among individuals of the same sex for mating opportunities with the opposite sex. This type of selection often involves direct conflicts or displays of strength and aggression. It can lead to the development of exaggerated traits or behaviors to outcompete rivals. Male-male combat is a common example of intrasexual selection in the animal kingdom. Intrasexual selection plays a significant role in shaping reproductive strategies and evolution. Lamarck Lamarck was a French naturalist who proposed the theory of inheritance of acquired characteristics. Lamarck's theory suggested that traits acquired during an organism's lifetime could be inherited by future generations. He believed that species could change and evolve over time through the use or disuse of certain features. Unlike Darwin's theory of natural selection, Lamarck's theory did not involve competition and survival of the fittest. Lamarck's ideas were largely discredited in the scientific community, but his work paved the way for further understanding of evolution. Lyell Lyell was a geologist known for his theory of uniformitarianism, which proposed that geological processes we see today also shaped the Earth's past.  Lyell's work influenced Charles Darwin, who incorporated his ideas into the theory of evolution. Uniformitarianism challenged the prevailing belief in catastrophism, which proposed that major geological events were caused by sudden and catastrophic events. Lyell's book 'Principles of Geology' had a significant impact on the field and is still widely studied today. Lyell's theory of uniformitarianism laid the foundation for modern geological science. Malthus Malthus' theory states that population growth is limited by resources, leading to competition and struggle for survival. Malthus' theory is also known as the principle of population. He believed that population increases geometrically (exponentially) while resources grow arithmetically (linearly). Malthus' theory influenced Charles Darwin's theory of natural selection. His ideas are still significant in the study of human population dynamics. Monophyletic Monophyletic refers to a group of organisms that consists of a common ancestor and all of its descendants. Monophyletic groups are depicted on a phylogenetic tree by branching from a single point. Species within a monophyletic group share a more recent common ancestor than with species outside the group. A monophyletic group is considered a natural, coherent evolutionary unit. Cladistics is a method used to identify monophyletic groups based on shared derived characteristics. Non-random mating Non-random mating refers to the phenomenon in which individuals in a population selectively choose their mates based on certain traits or characteristics. Examples of non-random mating include assortative mating, inbreeding, and sexual selection. Non-random mating can lead to an increase in homozygosity in a population. This process can lead to the maintenance of specific traits within a population. Non-random mating can contribute to speciation by promoting reproductive isolation between populations. Paraphyletic Paraphyletic refers to a group that includes a common ancestor and some, but not all, of its descendants, leading to an incomplete evolutionary lineage. Traits of a paraphyletic group are not sufficient to define a monophyletic group. Paraphyletic groups can be problematic in classification and understanding evolutionary relationships. Examples of paraphyletic groups include reptiles, which exclude birds, and fish, which exclude tetrapods. Paraphyletic groups can potentially be redefined as monophyletic groups through further research and understanding. Phenotype A Phenotype is the observable characteristics or traits of an organism, resulting from the interaction of its genetic makeup and environmental influences. Phenotype encompasses an organism's appearance, physiological & biochemical properties. It is subject to change over an organism's lifespan due to environmental force. Observable traits can be simple (e.g., color) or complex (e.g., behavior). The term 'phenotype' contrasts with 'genotype', which is an organism's genetic constitution. Phenotypic variation Phenotypic variation refers to the range of observable traits in a population resulting from genetic and environmental factors. It is influenced by both genetic inheritance and environmental factors. Phenotypic variation is essential for evolution and adaptation. It allows individuals within a population to have different traits, such as height or eye color. Studying phenotypic variation can help researchers understand the role of genetics in disease susceptibility. Phylogenetic tree A phylogenetic tree is a diagram utilized by scientists to represent the evolutionary relationships among various species based on their genetic similarities and differences. Each branch in the tree signifies a distinct species or group of species. The root of the tree signifies the most recent common ancestor of the species in the tree. Branch lengths may reflect time or genetic change. The tree may be rooted or unrooted, impacting interpretation. Polyphyletic Polyphyletic refers to a group that does not share a common evolutionary ancestor, making it an unnatural grouping based on convergent characteristics. Polyphyletic groups are considered invalid in evolutionary classifications. Members of a polyphyletic group do not have a common ancestor. It is important to properly distinguish between polyphyletic and monophyletic groups in phylogenetic analyses. Polyphyletic classifications can lead to inaccuracies in understanding evolutionary relationships. Population A population refers to a group of individuals all belonging to one species that live in a defined geographic area. Populations exhibit various characteristics like growth rate, density and dispersion. A population's size is dynamic, changing due to birth, death, migration. Population genetics studies genetic variations within populations. Populations resilience plays critical part in ecosystem sustainability. Post-zygotic barriers Post-zygotic barriers are mechanisms that prevent hybrid zygotes from developing into viable, fertile offspring after fertilization. Common post-zygotic barriers include reduced hybrid viability and reduced hybrid fertility. Intrinsic post-zygotic barriers are caused by genetic incompatibilities within the hybrid offspring. Extrinsic post-zygotic barriers result from environmental factors limiting the survival or reproductive success of hybrid offspring. Post-zygotic barriers contribute to the reproductive isolation between different species. Pre-zygotic barriers Pre-zygotic barriers prevent fertilization between different species by acting before the formation of a zygote. Examples include differences in mating rituals, temporal isolation, and habitat isolation. These barriers help maintain species integrity and prevent hybridization. Pre-zygotic barriers can result from physical incompatibility or behavioral differences. They are important mechanisms in evolution and speciation processes. Selective pressure Selective pressure refers to any phenomena which alter the behaviour and fitness of living organisms within a given environment. It is a main driving force behind evolution and natural selection. Can be caused by factors like competition for resources, predation, or environmental changes. Organisms that adapt to selective pressures increase their chance of survival and reproduction. It influences the allele frequencies within a population, contributing to genetic diversity. Sexual selection Sexual selection is an evolutionary process, where certain traits increase an individual's likelihood of attracting mates and reproducing. It's a subset of natural selection. It can result in sexual dimorphism. Intersexual selection and intrasexual selection are its two main types. Darwin coined the term to explain attributes not beneficial for survival. Shared Derived Character A Shared Derived Character is a trait that is shared by a group of organisms and their common ancestor, distinguishing them from other related groups. Used in cladistics to construct phylogenetic trees based on shared evolutionary traits. Also known as synapomorphy, it helps determine evolutionary relationships between different species. Can be morphological, molecular, or behavioral characteristics that have evolved in a particular lineage. Presence of shared derived characters indicates a closer evolutionary relationship among the organisms. Shared primitive character Shared primitive character refers to a trait that is found in multiple related species and was present in their common ancestor. These characters help scientists understand evolutionary relationships. They are not unique to a particular group of species. Shared primitive characters are contrasted with derived characters that evolve later in a species' lineage. Identifying shared primitive characters aids in constructing phylogenetic trees. Stabilizing selection Stabilizing selection is an evolutionary process favoring intermediate phenotypes over extremes, maintaining genetic diversity. Results in reduced genetic variation. Common in stable, unchanging environments. Can lead to inclinations towards average characteristics. A factor in maintaining balanced polymorphism. Sympatric speciation Sympatric speciation refers to the process where new species evolve from a single ancestral species while inhabiting the same geographic region. It contrasts with allopatric speciation, involving physical separation. This can occur if genetic mutations create differences within a population. Common in plants due to polyploidy. Reproductive isolation is critical to prevent interbreeding. Temporal Isolation Temporal isolation refers to a reproductive barrier that prevents species from mating due to differences in the timing of their reproductive activities. Temporal isolation can occur when species have different mating seasons or times of day for mating. Temporal isolation is a mechanism of speciation, as it can lead to the formation of new species. Temporal isolation can be influenced by environmental factors such as changes in climate or availability of resources. Temporal isolation can also be influenced by behavioral factors, such as unique mating rituals or courtship behaviors. Transduction Transduction refers to the process where bacterial DNA is transferred from one bacterium to another through a virus or bacteriophage. Often occurs in bacteria and archaea which aids in horizontal gene transfer. Transduction requires contact between bacteria and the virus. There are two types: Generalized and Specialized transduction. The process can lead to bacterial resistance, as it can transfer resistance genes. Transformation Transformation refers to the process in which a cell takes up foreign DNA and incorporates it into its own genome. Transformation is a natural process that bacteria use to exchange genetic information. This process is commonly used in genetic engineering to introduce new genes into organisms. Transformation can be achieved by using electrical currents, heat shock, or chemicals to increase cell permeability. Once inside the cell, the foreign DNA can be integrated into the host genome through recombination. Vertical gene transfer Vertical gene transfer refers to the transmission of genetic material from parent to offspring through reproduction, resulting in genetic continuity. It is the primary mechanism for passing genes from one generation to the next. Occurs in sexually reproducing organisms and asexually reproducing organisms. Helps maintain the genetic stability of a species. Allows for the accumulation of genetic variations over many generations. Vestigial structures Vestigial structures refer to anatomical features that no longer serve a purpose in a particular species, but were useful in ancestors. An example is human's appendix, once used for digesting plant material. They represent evidence of evolution, demonstrating ancestral functions. Despite losing original function, some adapt new uses over time. They're observed throughout the animal kingdom, including whales' hip bones and snakes' tiny leg bones.