GenBio Exam PDF

UNIT 1: (A) pairs with Thymine (T), and Guanine (G) always pairs with COMPONENTS (GPT) Cytosine (C) DNA (Deoxyribonucleic Acid) 1. Nucleotides: The basic building blocks of DNA, each...

UNIT 1: (A) pairs with Thymine (T), and Guanine (G) always pairs with COMPONENTS (GPT) Cytosine (C) DNA (Deoxyribonucleic Acid) 1. Nucleotides: The basic building blocks of DNA, each consisting of three components: o Sugar: Deoxyribose o Phosphate Group: A phosphate group attached to the 5' carbon of the sugar o Nitrogenous Base: One of four types— adenine (A), thymine (T), cytosine (C), or guanine (G) 2. Double Helix Structure: DNA molecules are typically double-stranded, with two long chains of nucleotides running in opposite directions, coiled around each other to form a double helix. 3. Base Pairing: The two strands are held together by Basic functions of DNA hydrogen bonds between complementary bases: Information storage adenine pairs with thymine, and cytosine pairs with - DNA stores the genetic information that determines the guanine. characteristics and functions of an organism. RNA (Ribonucleic Acid) Transcription and translation 1. Nucleotides: The building blocks of RNA, similar to - DNA is transcribed into RNA and then translated into DNA but with some differences: proteins, which control cellular activities. o Sugar: Ribose (instead of deoxyribose) Replication o Phosphate Group: A phosphate group - DNA can make exact copies of itself, which is essential attached to the 5' carbon of the sugar for cell division and growth. o Nitrogenous Base: One of four types— Inheritance adenine (A), uracil (U) (replaces thymine in - DNA is inherited from generation to generation and is DNA), cytosine (C), or guanine (G) responsible for passing traits from parents to offspring. 2. Single-Stranded: RNA is usually single-stranded, although it can form secondary structures by folding RNA (Ribonucleic Acid) back on itself. Proteins 3. Base Pairing: In RNA, adenine pairs with uracil, and Amino acids are the building blocks for proteins. This means cytosine pairs with guanine. our DNA codes Proteins for different proteins that perform specific functions in our body. 1. Amino Acids: The building blocks of proteins, each consisting of: There are different codons for amino acids o Amino Group: -NH₂ o Carboxyl Group: -COOH Three “stop” codons mark the polypeptide as finished o Hydrogen Atom: -H One codon, AUG, is a “start” signal to kick off o Side Chain (R Group): Varies between translation (it also specifies the amino acid methionine) different amino acids and determines the properties of the amino acid 2. Peptide Bonds: Amino acids are linked together by STRUCTURE OF PROTEINS peptide bonds, forming polypeptide chains. Primary structure - describes the order of amino acids; linear 3. Levels of Structure: and unbranched o Primary Structure: The sequence of amino Secondary structure - formed from the primary structure; an acids in the polypeptide chain. amino group bonds with a carboxyl group from the same chain o Secondary Structure: Local folding into Tertiary structure - forms because of hydrogen bonding or ionic alpha-helices and beta-sheets stabilized by bonding between R groups of amino acids with sulfur hydrogen bonds. Quaternary structure - union of two or more tertiary structured o Tertiary Structure: The overall 3D shape of polypeptide which may be held together by interactions of the R a single polypeptide chain, determined by group, hydrogen bonding, and disulfide bonds. interactions among the side chains. o Quaternary Structure: The arrangement of multiple polypeptide chains (subunits) into a functional protein. COMPONENTS (quipper) Brief Review of DNA Structure Double Helix - A double helix is the shape of a DNA molecule. Imagine a twisted ladder that is essentially what a DNA molecule looks like Nucleotides - Nucleotides are the basic units of DNA, composed of a phosphate group (P), a sugar (deoxyribose), and a nitrogenous base (A, C, G, or T) that encodes genetic UNIT 1: (B:1-4) information. DNA REPLICATION (GPT) Base Pairing - The specific pairing of nucleotides in DNA, by 1. DNA Polymerase which are held together by hydrogen bonds. Adenine (A) always Function: DNA polymerase is the enzyme responsible for synthesizing new DNA strands. It adds nucleotides to the growing DNA chain in a sequence complementary to the - the initializer template strand. - helps polymerase on knowing where to start its work by Mechanism: making what we call a ‘Primer’ Template Strand: DNA polymerase reads the DNA Polymerase existing DNA strand (template strand) and adds - the builder enzyme complementary nucleotides to the new strand being - replicates DNA molecules to create a new strand of synthesized. DNA. Direction: It synthesizes DNA in the 5' to 3' direction. Ligase - the gluer Proofreading: DNA polymerase has proofreading - glues the DNA fragments together abilities to correct errors during DNA synthesis, Replication ensuring high fidelity in DNA replication. Process of DNA replication 2. Primase Initiation: Function: Primase synthesizes a short RNA primer that - The two DNA strands unwind and separate, breaking provides a starting point for DNA polymerase to begin DNA the hydrogen bonds between complementary bases synthesis. (A-T, C-G). Short RNA sequences called primers Mechanism: (attached to the single strands of DNA) provides a Primer Creation: Primase creates a short RNA starting point for DNA synthesis. primer (usually 10-15 nucleotides long) on the single- Elongation: stranded DNA template. This primer provides a free 3' - Free nucleotides pair with the exposed bases on each hydroxyl (OH) group to which DNA polymerase can strand, following the rules of complementarity. One add DNA nucleotides. strand, called the leading strand, is synthesized Temporary Nature: The RNA primer is eventually continuously in the 5' to 3' direction. The other strand, removed and replaced with DNA nucleotides. called the lagging strand, is synthesized 3. Helicase discontinuously in short fragments called Okazaki Function: Helicase unwinds and separates the double- fragments. The RNA primers are removed and stranded DNA to make the strands available for replication. replaced with DNA nucleotides. Mechanism: Termination: Unwinding: Helicase breaks the hydrogen bonds - The Okazaki fragments on the lagging strand are between the complementary base pairs of the DNA joined together by an enzyme called DNA ligase, strands, converting the double helix into two single forming a continuous DNA strand. DNA polymerase strands. checks for errors and corrects them to ensure Travel: It moves along the DNA, opening up the helix accuracy. in the direction of replication. UNIT 1: (C) 4. Topoisomerase DIFFERENCE BETWEEN EUKARYOTES AND Function: Topoisomerase alleviates the torsional strain and PROKARYOTES(GPT) supercoiling that occurs ahead of the replication fork as the Prokaryotes: Faster DNA replication due to a single, circular DNA is unwound. chromosome, fewer regulatory mechanisms, and fewer Mechanism: nucleotides to replicate. Replication speed is about 1,000 to Cutting and Rejoining: Topoisomerase makes 2,000 nucleotides per second. temporary cuts in the DNA strands to relieve the Eukaryotes: Slower DNA replication due to multiple, linear stress caused by unwinding and then reseals the cuts. chromosomes, complex chromatin structure, and extensive Types: regulatory mechanisms. Replication speed is about 50 to 100 o Topoisomerase I: Cuts one strand of the nucleotides per second. DNA. DIFFERENCE BETWEEN EUKARYOTES AND o Topoisomerase II (DNA gyrase in PROKARYOTES(QUIPPER) bacteria): Cuts both strands of the DNA to Occurs in the nucleus of the eukaryotic cells and the cytoplasm of relieve tension. prokaryotic cells Summary of the Replication Process: UNIT 1: (D) 1. Unwinding: Helicase unwinds the DNA double helix, TRANSCIPTION (GPT) and topoisomerase prevents supercoiling. Transcription is the process by which the genetic information in 2. Priming: Primase synthesizes an RNA primer on the DNA is copied into a complementary RNA sequence. Here’s a single-stranded DNA. simplified overview: 3. Polymerization: DNA polymerase adds new DNA 1. Initiation: nucleotides to the 3' end of the primer, extending the o Binding: RNA polymerase, the enzyme new DNA strand. responsible for transcription, binds to a 4. Replacement: The RNA primer is later removed and specific region of the DNA called the replaced with DNA by a different DNA polymerase. promoter, which signals the start of a gene. DNA REPLICATION (quipper) o Unwinding: The DNA double helix is Enzymes unwound and separated in the region of the The ability to speed up reactions, build up or break down items gene to be transcribed. that they act upon on. 2. Elongation: o RNA Synthesis: RNA polymerase moves Types of Enzymes along the DNA template strand, adding Helicase complementary RNA nucleotides to the - the unzipping enzyme growing RNA chain. The RNA strand is - since the DNA has two strands, it is tasked with synthesized in the 5' to 3' direction, separating the two. complementary to the DNA template strand. Primase 3. Termination:  o Stopping: Transcription continues until RNA - Once transcribed, they cause the transcript to be released from polymerase reaches a termination signal, a the RNA polymerase. specific sequence of DNA that signals the end of the gene. o Release: The RNA polymerase enzyme and the newly formed RNA transcript are released from the DNA. The DNA strands rejoin to form the double helix. 4. Processing (in eukaryotes): o Modification: The initial RNA transcript (pre- mRNA) undergoes modifications such as adding a 5' cap, a 3' poly-A tail, and splicing out introns (non-coding regions) to form the mature mRNA. TRANSCIPTION (quipper) STAGE I: INITIATION - RNA polymerase binds to a sequence of DNA called the promoter - Found near the beginning of gene - Each gene has its own promoter - Once bound, RNA polymerase separates the DNA strands, providing the single-stranded template needed for transcription. UNIT 1: (E) Translation/Protein synthesis (GPT) Translation, or protein synthesis, is the process through which the genetic code carried by mRNA is used to build a protein. Here’s a breakdown of the key components and the concept of hydrolysis in this context: i. mRNA (Messenger RNA) Function: mRNA serves as the template for protein synthesis. It carries the genetic information from the DNA (in the nucleus) to the ribosome (in the cytoplasm), where the protein will be STAGE II: ELONGATION assembled. - One strand of DNA - TEMPLATE STRAND- acts as a template for RNA polymerase Process: - Builds an RNA molecule out of complementary nucleotides, Codons: The mRNA sequence is read in sets of three making a chain that grows from 5’to 3’ nucleotides called codons. Each codon specifies a - RNA transcript carries the same information as the non-template particular amino acid to be added to the growing (coding) strand of DNA, but it contains the base uracil(U) of polypeptide chain. thymine (T) ii. tRNA (Transfer RNA) Function: tRNA molecules transport amino acids to the ribosome and match their anticodons with the codons on the mRNA. Process: Anticodons: Each tRNA has an anticodon that is complementary to a specific mRNA codon. This ensures that the correct amino acid is added to the growing polypeptide chain. Amino Acid Attachment: Each tRNA carries a specific amino acid to the ribosome, where it adds its amino acid to the chain according to the mRNA sequence. WHAT DO 5’AND 3’MEAN? iii. Amino Acid - Two ends of a strand of DNA or RNA strand are different from Function: Amino acids are the building blocks of proteins. each other They are linked together in a specific sequence dictated by the - DNA / RNA strand has directionality mRNA to form a polypeptide chain. At the 5’ end of the chain, the phosphate group of the first nucleotide in the Process: chain sticks out. The phosphate group is attached to the 5' carbon of the sugar Peptide Bond Formation: Amino acids are linked by ring, which is why this is called the 5' end. peptide bonds, forming a polypeptide chain that folds into a functional protein. At the 3’ end, the hydroxyl of the last nucleotide added to the chain is exposed. 1. Hydrolysis The hydroxyl group is attached to the 3' carbon of the sugar ring, which is why Concept: Hydrolysis is the chemical process by which peptide this is called the 3' end. bonds between amino acids in a protein are broken down, typically during protein degradation. STAGE III: TERMINATION Process: - Sequences called terminators signal that the RNA transcript is complete.  Water Molecules: Hydrolysis involves the addition of Mechanism: water molecules to break peptide bonds. Each peptide bond requires one water molecule to break. Dominant Allele: The allele that is expressed in the Example Calculation: To break a polypeptide chain phenotype. with n amino acids into individual amino acids, you Recessive Allele: The allele that is masked by the need n−1 water molecules. For instance, if a presence of a dominant allele and only expressed polypeptide chain consists of 6 amino acids, breaking when two recessive alleles are present. it into individual amino acids requires 5 water molecules. Summary Example: In pea plants, the allele for purple flowers (P) is 1. mRNA carries the genetic code from DNA to the dominant over the allele for white flowers (p). A plant with the ribosome. genotype Pp will have purple flowers because the dominant 2. tRNA brings the appropriate amino acids to the allele (P) masks the effect of the recessive allele (p). ribosome, matching their anticodons with the codons on the mRNA. Summary 3. Amino Acids are linked together to form proteins. 4. Hydrolysis breaks peptide bonds between amino 1. Law of Segregation: Each parent contributes one acids using water molecules. For a polypeptide chain allele for each gene to their offspring, and these with 6 amino acids, 5 water molecules are needed to alleles segregate during gamete formation. completely hydrolyze the peptide bonds. 2. Law of Independent Assortment: Genes for UNIT 1: (f) different traits are inherited independently of each LAWS OF INHERITANCE(GPT) other if they are located on different chromosomes. The Laws of Inheritance, formulated by Gregor Mendel in the 3. Law of Dominance: In a heterozygote, the dominant 19th century, describe how traits are passed from parents to allele masks the effect of the recessive allele, offspring. Mendel's work laid the foundation for classical determining the phenotype. genetics. Here’s an overview of these key principles: LAWS OF INHERITANCE(quipper) 1. Law of Segregation Genetics Definition: Each individual has two alleles for each gene, one Genetics is the study of heredity (the transmission of inherited from each parent. These alleles separate (segregate) transmission of traits from generation to generation). during the formation of gametes (sperm and egg cells), so Genetics began with the work of Gregor Mendel. each gamete carries only one allele for each gene. Mendel developed basic principles of heredity with NO knowledge of genes or chromosomes. Mechanism: Mendel worked with pea plants. Why peas? Pea plants: Gamete Formation: During meiosis, the alleles for a Are inexpensive given gene separate into different gametes. Reproduction is easy to control Fertilization: When gametes fuse during fertilization, Produce many offspring the resulting offspring have two alleles for each gene, Pea plants have contrasting characteristics. one from each parent. Contrasting characteristics include: Seeds – round or wrinkled Example: For a gene controlling flower color in pea plants Seed Color – yellow or green (e.g., purple or white), if a plant has one purple allele and one white allele (Pp), the gametes will receive either the P allele or Height – tall or short the p allele, but not both. Flowers – white or purple Pod color – yellow or green 2. Law of Independent Assortment Etc. Mendel Developed Principles of: Definition: Genes for different traits are passed independently 1. Dominance: one form of a hereditary trait that dominates or of one another from parents to offspring. This means the prevents the expression of the recessive trait. inheritance of one trait (e.g., flower color) does not influence 2. Segregation: Splitting of chromosomes during meiosis the inheritance of another trait (e.g., seed shape). 3. Recombination: Combining chromosomes from both the sperm and egg (fertilization) Example: In pea plants, if you track two traits, such as flower 4. Independent Assortment: Independent segregation of color and seed shape, the inheritance of flower color is genes during the formation of gametes. independent of seed shape. Pea Plant Characteristics 3. Law of Dominance - Mendel determined that since peas reproduce sexually, there must be two “characters” (called alleles) that influence each trait. (one from the egg and one from the sperm). Definition: In a heterozygous organism (with two different - Alleles are represented by letters. alleles for a gene), one allele may mask the expression of the other allele. The dominant allele is expressed in the phenotype, UNIT 1: (G) while the recessive allele is not. GENETICS(GPT). Punnett Squares Definition: Punnett squares are a tool used to predict the Trait Expression: The trait appears if at least one genotypic and phenotypic outcomes of a genetic cross between dominant allele is present. An individual with one two organisms. dominant allele will express the trait. How It Works: Pedigree Pattern: The trait tends to appear in every Setup: A Punnett square is a grid where the possible generation and is passed directly from affected parents gametes of one parent are listed along the top and the to their offspring. possible gametes of the other parent are listed along the side. v. Breeding, Crossbreeding, and Genetic Engineering Filling Out: The squares inside the grid are filled in by 1. Breeding combining the alleles from each parent to show the Definition: Breeding involves mating organisms to produce possible genotypes of the offspring. offspring with desired traits. Outcome: The completed Punnett square helps Advantages: determine the probability of different genotypes and Selective Traits: Allows for the enhancement of phenotypes among the offspring. desirable traits in plants and animals. Example: For a cross between two heterozygous pea plants Controlled Outcomes: Can lead to improvements in (Pp), a Punnett square would show the 3:1 phenotypic ratio of yield, disease resistance, and other beneficial traits. dominant to recessive traits in the offspring. Disadvantages: Genetic Diversity: Can reduce genetic diversity, ii. Non-Mendelian Patterns of Inheritance potentially leading to inbreeding and associated health 1. Incomplete Dominance problems. Definition: Incomplete dominance occurs when the phenotype Time: Traditional breeding can take many generations of a heterozygous individual is intermediate between the to achieve desired results. phenotypes of the two homozygous parents. 2. Crossbreeding Example: In snapdragons, if red-flowered (RR) and white- Definition: Crossbreeding involves mating individuals from flowered (WW) plants are crossed, the resulting offspring (RW) different breeds, varieties, or species to produce offspring with have pink flowers, showing an intermediate phenotype. traits from both parents. 2. Codominance Advantages: Definition: Codominance occurs when both alleles in a heterozygous individual are fully expressed, resulting in a Hybrid Vigor: Often results in hybrids with enhanced phenotype that shows both traits simultaneously. characteristics such as better growth rates or disease Example: In blood types, the A and B alleles are codominant. resistance. An individual with genotype AB has both A and B antigens on Diverse Traits: Combines traits from different genetic the surface of red blood cells. backgrounds. 3. Sex-Linked Inheritance Disadvantages: Definition: Sex-linked traits are associated with genes located Unpredictable Outcomes: Can produce unexpected on the sex chromosomes (X or Y). These traits often show or undesired traits. different patterns of inheritance in males and females. Compatibility Issues: Not all species or breeds are Example: Hemophilia is a sex-linked recessive disorder carried compatible for crossbreeding. on the X chromosome. Males with one X-linked hemophilia allele 3. Genetic Engineering will express the condition because they have only one X Definition: Genetic engineering involves directly manipulating chromosome, while females need two copies of the allele to an organism’s DNA using biotechnology to introduce, remove, express it. or alter genetic material. Advantages: iii. Epistasis Precision: Allows for precise modifications to specific Definition: Epistasis occurs when the expression of one gene genes, leading to targeted improvements. is affected by one or more other genes. It involves interactions Rapid Results: Can achieve desired traits more between different gene products. quickly than traditional breeding methods. Example: In Labrador retrievers, coat color is determined by two Disadvantages: genes: one for pigment color (B/b) and one for pigment deposition (E/e). The presence of the recessive ee genotype Ethical Concerns: Raises questions about the ethics masks the effect of the B/b genotype, resulting in a yellow coat of manipulating genetic material. regardless of the B/b genotype. Unintended Effects: Potential for unintended consequences or off-target effects. iv. Pedigree Analysis GENETICS(quipper) Definition: Pedigree analysis is a method used to trace the inheritance patterns of specific traits through generations in a i. Punnett Square – used to predict the outcome of family. genetics crosses 1. Autosomal Recessive Hybrid Cross - When two heterozygotes are crossed, there are Characteristics: 3 possible genotypes which occur in a 1:2:1 ratio. Trait Expression: The trait only appears if an 1 Homozygous Dominant 2 Heterozygous Dominant individual inherits two recessive alleles (one from each 1 Homozygous Recessive parent). Carriers of the trait have one recessive allele but do not express the trait. The phenotypic ratios are 3:1 or 3 Dominant : 1 Recessive It is not possible to tell the appearance if an individual Pedigree Pattern: The trait may skip generations and is showing a dominant trait that is pure (BB) or hybrid (Bb). can be carried by individuals who do not express it. Therefore, you must perform a test cross. 2. Autosomal Dominant Test Cross – To determine the genotype of an organism Characteristics: showing a dominant phenotype, cross the organism with a recessive individual. If any recessive offspring are produced the 2. Adaptation: Over time, advantageous traits become individual is heterozygous. more common in the population, leading to gradual ii. Codominance - some traits are controlled by 2 adaptation to the environment. different dominant alleles. Both alleles are dominant, 3. Descent with Modification: Over generations, and there are two dominant phenotypes. A populations evolve, and new species can arise as a heterozygote expresses both phenotypes at the same result of the gradual accumulation of adaptations. time. ii. Natural Selection Definition: Natural selection is the process through which Incomplete Dominance - (blending inheritance) sometimes an certain traits become more common in a population because allele is only partly dominant over another. they offer some advantage in survival and reproduction. In a heterozygote the dominant allele is only partially expressed Mechanisms: and the phenotype is between the two homozygous forms. 1. Fusion: o Definition: Fusion in evolutionary biology Gene Linkage – If the genes for two different traits are located generally refers to the merging of distinct on the same chromosome pair (homologous chromosomes), populations into a single, larger population. they are said to be linked, and are usually inherited together. o Impact: Fusion can reduce genetic Ex. The gene for eye and hair color are on the same divergence between populations and chromosome. Blond hair is often inherited with blue eyes. increase genetic diversity within the combined population. Crossing over – In the 1st meiotic division the chromatids of 2. Gene Flow: homologous chromosomes may exchange segments. This o Definition: Gene flow is the transfer of results in the rearrangement of linked genes and increases genetic material between separate variability of offspring. populations through interbreeding. o Impact: Gene flow can introduce new alleles Multiple Alleles - some traits are controlled by more than 2 into a population, increasing genetic variation different alleles types. and potentially helping populations adapt to Ex. Human blood types – The inheritance of blood types in changing environments. humans can be explained by a model in which there are 3 alleles 3. Genetic Drift: for blood type. o Definition: Genetic drift is the random fluctuation of allele frequencies in a Sex Determination - Scientists have discovered that population due to chance events. chromosomes in cells from males and females were identical o Impact: Genetic drift is more pronounced in except for one pair small populations and can lead to significant Humans have 23 pairs of chromosomes. changes in allele frequencies over time, 22 pairs of autosomes sometimes resulting in the loss of genetic Pair of sex chromosomes variation. 4. Mutation: The sex chromosomes are called X and Y o Definition: Mutation is the change in the DNA The XX condition produces females, and the XY condition sequence of an organism’s genome. produces males. o Impact: Mutations introduce new genetic variations into a population. While many Sex Linkage - Thomas Hunt Morgan’s work with Drosophila mutations are neutral or harmful, some can be (fruit Fly) demonstrated that some genes are located on the X beneficial and contribute to evolutionary chromosome and do not have a corresponding allele on the Y changes. chromosome. iii. Speciation Since many sex-linked genes are recessive, they are expressed Definition: Speciation is the process by which new species in males more than in females. arise from existing ones. It occurs when populations of a species UNIT 2: (A) become reproductively isolated and diverge to form new DARWINISM(GPT) species. Darwinism refers to Charles Darwin's theory of evolution Types of Speciation: through natural selection. Here’s a detailed explanation of 1. Allopatric Speciation: Darwinism, including observations and inferences, natural o Definition: Allopatric speciation occurs when selection mechanisms, and speciation types: a population is geographically separated into i. Inferences and Observations distinct groups that evolve independently. Observations: o Mechanism: Geographic barriers (such as 1. Variation: Individuals within a species show variation mountains, rivers, or distance) prevent gene in their traits. flow between populations, leading to 2. Inheritance: Some of these traits are heritable and divergent evolution. Over time, genetic passed on from parents to offspring. differences accumulate, and the isolated 3. Overproduction: Organisms tend to produce more populations may become distinct species. offspring than can survive to adulthood. o Example: The Darwin's finches on the 4. Struggle for Existence: There is competition for Galápagos Islands evolved into different limited resources among individuals within a species due to geographic isolation and population. different environmental pressures on each Inferences: island. 1. Differential Survival and Reproduction: Individuals 2. Sympatric Speciation: with traits better suited to their environment are more o Definition: Sympatric speciation occurs likely to survive and reproduce. This is often without geographic separation, within a summarized as "survival of the fittest." single, continuous population.  o Mechanism: This type of speciation can occur through mechanisms such as polyploidy (increased number of chromosomes), habitat differentiation, or sexual selection. Individuals within the Survival of the Fittest: Individuals with certain heritable population may evolve different adaptations adaptive characteristics survive and reproduce at a higher or preferences that lead to reproductive rate than other individuals. isolation. Natural selection increases the adaptation of organisms to o Example: In cichlid fish in African lakes, their environment over time. different species have evolved in the same Speciation: If an environment changes over time, natural lake by exploiting different ecological niches selection may result in adaptation to these new conditions or through mate preferences, leading to and may give rise to new species. reproductive isolation despite the absence of physical barriers. ii. Natural Selection Summary 1. Darwinism: - There is competition for survival o Observations: Variability, inheritance, - Individuals with best adaptations survive and reproduce overproduction, and competition. - Lead to the evolution of new species over time as o Inferences: Differential survival and populations diverge due to differential survival and reproduction lead to adaptation and descent reproduction. with modification. 2. Natural Selection: 4 TYPES OF NATURAL SELECTION o Fusion: Merging of populations. o Gene Flow: Transfer of genetic material STABILIZING SELECTION - Natural selection in which between populations. intermediate phenotypes survive or reproduce more o Genetic Drift: Random changes in allele successfully than do extreme phenotypes. frequencies. o Mutation: Introduction of new genetic DIRECTIONAL SELECTION - Natural selection in which variations. individuals at one end of the phenotypic range survive or 3. Speciation: reproduce more successfully than do other individuals o Allopatric: Speciation due to geographic isolation. DIVERSIFYING (DISRUPTIVE) SELECTION - Natural selection o Sympatric: Speciation occurring without in which individuals on both extremes of a phenotypic range geographic barriers, often through ecological survive or reproduce more successfully than do individuals with or reproductive mechanisms. intermediate phenotypes. DARWINISM(quipper) i. VARIATION SEXUAL SELECTION - Sexual selection occurs when certain Phenotypic variation in coat color within populations traits increase an individual's chances of mating and Genetic variation at the MclR (melanocortin-1 receptor) reproducing. These traits may not necessarily increase survival locus associated with coat color. fitness but can still evolve through mate choice. Variation in coat color could result from genetic differences, from environmental differences Genetic drift: This refers to the random fluctuations in allele frequencies that can occur in small populations. Genetic drift can FITNESS CONSEQUENCE be caused by different factors, such as: Fitness - differential effect of the trait on the expected reproductive success of an individual relative to other Founder effect: This occurs when a small group of individuals individuals in its population from a larger population colonize a new area, leading to a new population with reduced genetic diversity compared to the original population. Bottleneck effect: This occurs when a population undergoes a sudden reduction in size, leading to a decrease in genetic diversity. GENETIC FLOW Movement of alleles between populations due to migration or interbreeding. Gene flow can increase the genetic diversity of a population, as new alleles are introduced from other populations. Conversely, ADAPTATION gene flow can also reduce genetic diversity if a population loses Refers to an inherited trait that makes an organism more fit its unique alleles due to interbreeding with other populations. in its abiotic (nonliving) and biotic (living) environment, and that has arisen as a result of the direct action of natural Primordial Soup Theory selection for its primary function. -the theory states that if energy is added to the gases that made up Earth's early atmosphere, the building blocks of life would be created UNIT 2: (B) LAMARCKISM(GPT) Lamarckism is an early theory of evolution proposed by Jean- aspects of species formation and maintenance. Here’s an Baptiste Lamarck in the early 19th century. Although it has overview of the three main species concepts: largely been replaced by Darwinian evolution and modern i. Biological Species Concept genetics, it was influential in shaping early ideas about how Definition: The Biological Species Concept, proposed by Ernst organisms evolve. Here’s a detailed explanation Mayr, defines a species as a group of organisms that can of Lamarckism and its concept of Use and Disuse: interbreed and produce fertile offspring under natural conditions. Lamarckism Members of the same species share a common gene pool and Definition: Lamarckism, or Lamarckian evolution, is the idea are reproductively isolated from other such groups. that organisms evolve through the inheritance of acquired Key Points: characteristics. According to Lamarck, traits that an organism Reproductive Isolation: Species are maintained by acquires during its lifetime can be passed on to its offspring. barriers to reproduction that prevent gene flow between i. Use and Disuse different species. These barriers can be prezygotic Definition: The principle of Use and Disuse is a central (preventing mating or fertilization) or postzygotic component of Lamarck’s theory. It posits that traits become (preventing the development of viable or fertile more pronounced or diminished based on their use or disuse offspring). during an organism's lifetime. Gene Flow: Successful interbreeding and gene Mechanism: exchange within a species help maintain the genetic Use: Traits that are used or exercised become more cohesion of the species. developed and pronounced. For instance, if an Limitations: This concept is less applicable to asexual organism frequently uses a particular organ or body organisms (like bacteria) and organisms that do not part, that organ becomes stronger or more prominent. have well-documented breeding patterns. It also can Disuse: Traits that are not used or are used less be challenging to apply to extinct species or those with frequently become reduced or may eventually limited observation. disappear. Example: In nature, humans (Homo sapiens) and chimpanzees Examples: (Pan troglodytes) are considered separate species because 1. Giraffe's Neck: Lamarck famously used the example they cannot interbreed and produce fertile offspring. of giraffes to illustrate his theory. He suggested that ii. Ecological Species Concept ancestral giraffes had shorter necks, but they stretched Definition: The Ecological Species Concept defines a species their necks to reach higher branches. Over based on its ecological niche, or the unique role and position it generations, these longer necks would be inherited by occupies in its environment. A species is identified by its their offspring, leading to the long-necked giraffes we adaptation to a particular set of environmental conditions and its see today. interactions with other organisms. 2. Muscle Development: Another example is the idea Key Points: that if a person builds muscle through exercise, their Niche Differentiation: Species are considered distinct offspring would inherit those larger muscles. Lamarck if they occupy different ecological niches and have believed that physical changes due to exercise or different roles in the ecosystem. This concept disuse could be passed on to the next generation. emphasizes the ecological and environmental factors Key Points and Criticisms that contribute to species identity. Lamarck’s Influence: Lamarck's theory was among Adaptive Traits: Species are identified by the specific the first to propose a mechanism for evolutionary adaptations they possess that allow them to exploit change and contributed to the discussion on how their niche effectively. organisms adapt over time. Flexibility: This concept can be useful for identifying Criticisms: species in ecological contexts where reproductive o Lack of Evidence: Modern genetics and isolation is not apparent or relevant. evolutionary biology have shown that Example: The various species of Darwin's finches on the acquired characteristics are not typically Galápagos Islands are distinguished not only by their physical passed on to offspring. Changes that occur in traits but also by their specialized feeding behaviors and an organism’s lifetime generally do not affect ecological niches. the DNA in a way that can be inherited. iii. Morphological Species Concept o Genetic Inheritance: The discovery of DNA Definition: The Morphological Species Concept defines a and the principles of Mendelian genetics species based on its physical characteristics and morphology. It demonstrated that inherited traits are passed identifies species based on shared structural features and through genetic material rather than through overall appearance. changes acquired during an organism’s Key Points: lifetime. Physical Traits: Species are classified based on Summary observable physical traits and anatomical features, Lamarckism proposed that evolution occurs through the such as size, shape, and coloration. inheritance of traits acquired during an organism's life, with the principle of Use and Disuse suggesting that traits are Practical Use: This concept is often used for developed or diminished based on their use or non-use. While identifying fossil species and in cases where influential in the early study of evolution, Lamarckism has been reproductive behavior is not well understood. largely superseded by Darwinian natural selection and modern Limitations: Morphological variation can occur within genetic understanding, which provide a more accurate a species, and similar physical traits can evolve explanation of evolutionary processes. independently in different species (convergent UNIT 2: (C) evolution), which can lead to misidentification. SPECIES CONCEPT (GPT) Example: Different species of beetles might be distinguished Species concepts are frameworks used to define and identify from each other based on differences in body shape, color what constitutes a species. Each concept emphasizes different patterns, and size. Summary  1. Biological Species Concept: Defines species based Tiktaalik: A fossil that shows characteristics of both on reproductive isolation and the ability to produce fish and early tetrapods, bridging the gap between fertile offspring. aquatic and terrestrial life. 2. Ecological Species Concept: Defines species based iii. Biogeography on their ecological niche and adaptation to specific Definition: Biogeography is the study of the geographical environmental conditions. distribution of species and ecosystems across the planet. It 3. Morphological Species Concept: Defines species provides evidence of evolutionary processes based on the based on physical traits and morphological spatial distribution of organisms. characteristics. Key Points: SPECIES CONCEPT (quipper) Geographic Distribution: The distribution of species Importance concepts: can be explained by historical events such as Biological Species Concept continental drift, glaciation, and the movement of - species is a group of interbreeding natural population that is tectonic plates. reproductively isolated from other such groups. Endemism: Species that are found only in specific Evolutionary Species Concept regions (endemics) often have evolutionary - a single lineage of ancestor-descendant populations of relationships to other species in nearby areas, organisms which maintains its identity from other such lineages reflecting past geographical connections. [in space and time] and which has its own evolutionary Examples: tendencies and historical fate. UNIT 2: (D) Galápagos Islands: The unique species found on the EVOLUTIONARY EVIDENCES(GPT) Galápagos Islands, such as Darwin's finches, illustrate Evolutionary evidence provides insights into how species adaptive radiation and how isolated environments can have evolved over time and how they are related to one another. lead to speciation. Here’s an explanation of the key types of evidence supporting Marsupials: The distribution of marsupials in Australia the theory of evolution: and the Americas provides evidence of historical i. Homologous Structures biogeographical patterns and evolutionary divergence. Definition: Homologous structures are anatomical features in iv. Direct Observation different species that have a similar origin but may serve Definition: Direct observation involves witnessing evolutionary different functions. These structures arise from a common changes and adaptations in real-time, often through controlled evolutionary ancestor. experiments or long-term studies. Key Points: Key Points: Common Ancestry: Homologous structures indicate Microevolution: Observations of small-scale that species with these features share a common evolutionary changes within populations evolutionary origin. Despite differing in function, the (microevolution) show how species adapt to underlying anatomical structure is similar. environmental pressures over shorter timescales. Divergent Evolution: Homologous structures are Experimental Evidence: Laboratory and field often the result of divergent evolution, where an experiments can demonstrate evolutionary processes ancestral trait is modified over time as species adapt to and natural selection in action. different environments or ecological niches. Examples: Examples: Antibiotic Resistance: The evolution of antibiotic- Limbs of Vertebrates: The forelimbs of mammals resistant bacteria illustrates natural selection and (e.g., humans, whales, and bats) have different adaptation in response to drug pressures. functions (grasping, swimming, flying) but are built on Peppered Moth: The change in coloration of peppered a similar bone structure (humerus, radius, ulna). moths in response to industrial pollution is a well- Flower Structure: The flower structures in different documented example of natural selection. plant species may have evolved from a common Summary ancestor but adapted to different pollinators. 1. Homologous Structures: Anatomical features in ii. Fossil Records different species that indicate a common evolutionary Definition: Fossil records are the remains or impressions of origin and divergent evolution. ancient organisms preserved in sedimentary rock. They provide 2. Fossil Records: Evidence from fossils that provides a historical evidence of past life forms and their evolution over historical record of life forms and their evolutionary time. changes. Key Points: 3. Biogeography: The study of species distribution Chronological Evidence: Fossils show a across the globe, revealing patterns of evolutionary chronological sequence of evolutionary changes, history and adaptation. illustrating how species have changed over millions of 4. Direct Observation: Real-time observations of years. evolutionary processes, demonstrating how species adapt and evolve in response to environmental Transitional Forms: Fossils of transitional forms, or changes. "missing links," reveal intermediate stages between These lines of evidence collectively support the theory of different groups of organisms, supporting the concept evolution, illustrating the complex and dynamic processes that of gradual evolutionary change. drive the diversity of life on Earth. Extinction: Fossil records document extinct species EVOLUTIONARY EVIDENCES(quipper) and provide evidence of past biodiversity. 1. HOMOLOGICAL STRUCTURES Examples: Archaeopteryx: A transitional fossil between Homology - similarity of the structure, physiology, or dinosaurs and modern birds, showing features of both development of different species of organisms based upon their groups. descent from a common evolutionary ancestor 2. FOSSIL RECORDS 3. BIOGEOGRAPHY - the scientific study of the geographic distributions of species 4. DIRECT OBSERVATIONS MRSA -methicillin-resistant Staphylococcus aureus Methicillin works by deactivating an enzyme that bacteria use to synthesize their cell walls. S. aureus populations included individuals that were able to synthesize their cell walls using a different enzyme that was not affected by methicillin. UNIT 2: (E) EARTH’S HISTORY(GPT) i. Cambrian Period (541-485 million years ago) Cambrian Explosion: Rapid diversification of animal life, with most major phyla appearing. Development of Hard Parts: First appearance of shells and exoskeletons. Marine Dominance: Predominantly marine ecosystems with early reef-builders. ii. Devonian Period (419-359 million years ago) Age of Fishes: Extensive diversification of fish, including sharks and bony fish. First Land Plants: Emergence of vascular plants and early forests. First Amphibians: First vertebrates to transition from water to land. Extinctions: Multiple extinction events affecting marine life. iii. Permian Period (299-252 million years ago) Pangaea: Formation of the supercontinent Pangaea. Diverse Terrestrial Life: Rise of early reptiles and ancestors of mammals. Permian-Triassic Extinction: Largest mass extinction, with significant loss of marine and terrestrial species. iv. Triassic Period (252-201 million years ago) Recovery and Diversification: Recovery from the Permian extinction, rise of dinosaurs and early mammals. Breakup of Pangaea: Beginning of Pangaea’s breakup into Laurasia and Gondwana. First Dinosaurs: Appearance of early dinosaurs. First Mammals: Emergence of early mammal-like reptiles. Summary 1. Cambrian Period: Marked by the Cambrian Explosion, a rapid diversification of life forms, and the development of hard parts in organisms. 2. Devonian Period: Known as the "Age of Fishes," the rise of first land plants and forests, and the emergence of the first amphibians. 3. Permian Period: Characterized by the formation of the supercontinent Pangaea, diverse terrestrial life, and the Permian-Triassic extinction event. 4. Triassic Period: Featured the recovery from the Permian extinction, the breakup of Pangaea, and the emergence of the first dinosaurs and mammals. EARTH’S HISTORY(quipper) Precambrian Life ◦ What do scientists think was alive way back then?? ◦ Bacteria This era lasted for billions of years until more living organisms evolved