General Biology Reviewer - S.Y. 2024-2025 PDF

GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer L0 HISTORY OF THE EARTH 0.1 ORIGIN Gaseous Mass Hypothesis of Kant Nebular Theory of Laplace Planetesimal Hypothesis of Chamberlain and Moulton Tidal Collision Hypothesis of Jeans and Jeffreys Electromagnetic Theory of Dr. Hannes Alfvén Inter-stellar Dust Hypothesis of Otto Schmidt 0.3 FACTS The Earth is 4.54 billion years old 0.2 THEORIES Life on Earth emerged around 3.5 billion years ago Modern humans first appeared 100-150 thousand BIG BANG THEORY years ago. According to this theory, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and L1 EARTH GEOLOGIC TIME SCALE in all directions. 1.0 FOSSILS Fossil records in rock strata offer insights into Earth's evolutionary history. This history includes macroevolution, which covers major life changes, speciation, and evidence from geologic time scales. Geologic time scales are based on fossil sequences in sedimentary rock layers. 1.1 OVERVIEW: GEOLOGIC TIME SCALE Eon – the largest division of the geologic time scale; spans hundreds to thousands of millions of STEADY STATE THEORY years ago (mya) Era - division in an Era that spans time periods of tens to hundreds of millions of years Period - division of geologic history that spans no more than one hundred million years Epoch - the smallest division of the geologic time scale characterized by distinct organisms 1.2 THE PRECAMBRIAN SUPER EON PRECAMBRIAN SUPER EON 4.5 billion years About 88% of the Earth’s history Hadean Eon Earliest era, marked by Earth's (4.6 – 3.8 formation. billion years Earth coalesced from a cloud of dust ago) into a planet No life known. GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 1 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer High temperature Ordovician Oceans dominated by invertebrates. Period Plants dominated the land, while Archean Eon Earth was extremely hot; extensive (500–450 animals remained mostly aquatic. (3.8 – 2.5 volcanic activity and protocontinents million years Straight-shelled cephalopods, billion years existed. ago) trilobites, snails, brachiopods, and ago) Cooling led to condensation of water corals in a shallow inland sea. vapor and formation of rain. First fish evolved Atmosphere contained methane, carbon dioxide, sulfur dioxide, but no Silurian This was the “Golden Age” of free oxygen. Period cephalopods and brachiopods (a Stromatolites and bacterial cells were (450–400 clam-like shellfish). present. million years Corals appeared in the ocean. ago) The first land plants developed, and Proterozoic Cyanobacteria existed (w/o oxygen) the first arthropods (scorpion-like Eon and oxygenated the Earth invertebrates) ventured onto land. (2.5 billion – Ediacara fauna: oldest fossils of larger, 542 million multicellular, soft-bodied marine Devonian The “Golden Age” of fishes (Fish with years ago) animals. Period lobed fins) Divided into three eras: (400–350 First seed plants evolved with Paleoproterozoic, Mesoproterozoic, million years protective seed coats and stored food and Neoproterozoic. ago) in cotyledons. Key events: Fish with lobe fins evolved, able to - Rapid continental accretion. breathe air outside water. - Increase in atmospheric oxygen levels. Carboniferous Large plant forests left carbon - Presence of herbivorous Period deposits, forming coal and crude oil. eukaryotes (algae). (350–300 AGE OF AMPHIBIANS: First - First glaciation occurred. million years amphibians evolved, living in water ago) and on land. Latter Part of the Precambrian: Ichthyostegahad features like a tail - Development of single-celled and simple that it inherited from fish; and legs that multicellular organisms. allowed it to move around on land. - Many fossils are preserved due to sea-dwelling First reptiles evolved, capable of creatures trapped in sediments. reproducing on dry land. 1.3 THE PHANEROZOIC EON Subperiod: Pennsylanian and Divided into three eras: Paleozoic, Mesozoic, and Mississippian Cenozoic. PENNSYLVANIAN - peat swamps common, with scale trees, seed ferns, scouring rushes, PHANEROZOIC EON and large dragonflies MISSISSIPPIAN - Amphibious tetrapods PALEOZOIC ERA multiply wildly; many grow enormous in the high humidity and oxygen Giant insects and - Longest and most diverse of the Phanerozoic eon, myriapods flourish in the high humidity and lasting nearly 300 million years. oxygen - Divided into Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian periods. Permian Amphibians decline; reptiles and - An era began with the Cambrian Explosion a relatively Period insects increase; first mammal-like rapid period of speciation kicked off a long period of life (300–250 reptiles appear. flourishing on Earth. million years Non-seed plants decline. ago) Formation of Pangea (supercontinent). Cambrian Following a mass extinction, there was Extreme temperatures, dry climate. Period a surge of new organisms. Plants and animals evolved waxy (550–500 Sponges evolved. leaves and leathery skins to prevent million years Abundance of small invertebrates like water loss. ago) trilobites. Ended with a mass extinction. CAMBRIAN EXPLOSION: burst of diversity of Hard external skeletons protected trilobites, clams, snails, and sea urchins from predators. GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 2 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer PHANEROZOIC EON Eocene Epoch (55–35 million years ago) MESOZOIC ERA - Global temperatures increased by 5–8 °C. - Known as the Age of Dinosaurs. - “Middle Life” Oligocene Epoch (35–25 million years ago) - “Age of Reptiles” - horses, antelopes, cats, oreodonts - Humid and tropical, herbivores thrive and small mammals came into existence Neogene Miocene (25–5 million years ago) - Contains the Triassic, Jurassic, and Cretaceous Period - horses, rhinoceri, and elephants. periods. Pliocene (5–2 million years ago) Triassic First dinosaurs evolved and colonized - a time of global cooling after the Period land, water, and air. warmer Miocene time. (250–200 Forests dominated by seed ferns and million conifers. years ago) Modern corals, fish, and insects evolved. Pangea began splitting into Laurasia and Gondwanaland. Quaternary Climate cooled, leading to ice ages. Jurassic Known as the Golden Age of Dinosaurs, Period (2 Sea levels dropped, creating land Period with flourishing species. million bridges for animal migration. (200–150 Earliest birds evolved from reptilian years Mammals like woolly mammoths million ancestors. ago–prese adapted with large size and thick fur. years ago) Intense volcanic activity nt) Last ice age ended ~12,000 years ago, Major groups of mammals evolved, coinciding with the evolution of Homo remaining small in size. sapiens. Appearance of flowering plants, with new Epochs of the Quaternary Period: insects evolving to pollinate them. Pleistocene Epoch (2–0.01 million years ago) Cretaceous Flowering plants appeared for the first - mammals successfully colonized all Period time. environments (150–65 Dinosaurs reached their peak. - Hominids diverged from an early million Continents began resembling their current ape-like family. years ago) positions. Warm climate, no ice caps at the poles. Ardipithecus ramidus - 4.4 (bipedal, erect forest dweller) Ardipithecus anamensis - 4.2-3.9 (bipedal, apelike skull) Period ended with the extinction of Australopithecus afarensis (“Lucy”) - 3.9-2.8 (bipedal, apelike dinosaurs. face with sloping forehead, human-like bodies. Lived together in family groups.) and other species of Australopithecus - 3.0-1.1 Homo habilis - 2.2-1.6 m.y.a. (used stone tools, somay be PHANEROZOIC EON related to Homo sapiens, but skull is like australopithecines Homo erectus - 1.8-0.4 m.y. (Peking man, Java man: developed CENOZOIC ERA large brains, tools, weapons, fire, and learned to cook food.) Homo sapiens archaic - 500-200 t.y.a. (Skulls intermediate between Homo erectus and Homo sapiens sapiens) Homo sapiens neandertalensis-200-30 t.y.a (teeth and brain similar to ours, but DNA different, burial sites suggest they practiced some form of religion.) Age of Mammals Holocene (0.01 million years ago–present) - Homo sapiens sapiens- 12,000-present L2 THE EARLY EARTH AND THE EMERGENCE OF LIFE Paleogene Paleocene Epoch (65–55 million years ago) Period - Beginning of modern life forms 2.0 FORMATION OF EARTH AND EARLY (65–2.6 following the K-T Boundary extinctions. ATMOSPHERE million - Age of mammals began, and years ago) grasslands spread GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 3 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer Earth formed 4.6 billion years ago (BYA) through the condensation of dust and rocks surrounding the 2.1 MILLER-UREY EXPERIMENT (1953) young sun. In 1953, Stanley Miller and Harold Urey tested the During its first few hundred million years, the planet Oparin-Haldane hypothesis by recreating early Earth experienced intense bombardment by chunks of conditions in a lab. rock and ice. They demonstrated that organic molecules This bombardment generated massive amounts of essential for life could form from inorganic heat and vaporized any existing water, preventing components. the formation of seas or lakes. Gases exposed to The bombardment ceased about 4 BYA, marking electrical sparks the end of conditions hostile to life. (mimicking lightning) formed organic molecules, EARLIEST EVIDENCE OF LIFE including amino acids, Earliest fossils of prokaryotic cells date back 3.5 after a week. BYA. Experiments Prokaryotes were Earth’s first organisms and under neutral atmospheric dominated for 1.5 billion years until eukaryotes conditions also produced appeared 1.8 BYA. organic molecules. Miller’s volcanic eruption simulation yielded 2.1 HYPOTHESIZED STAGES OF LIFE even more amino acids. Meteorites like FORMATION the 4.5-billion-year-old Scientists propose life began via a four-step Murchison meteorite process involving: contained over 80 amino acids, simple sugars, and 1. The abiotic (nonliving) synthesis of small nitrogenous bases, many not of terrestrial origin. organic molecules, such as amino acids and nitrogenous bases 2. The joining of these small molecules into 2.3 ABIOTIC SYNTHESIS OF macromolecules, such as proteins and MACROMOLECULES nucleic acids 3. The packaging of these molecules into 2009 protocells, droplets with membranes that - The abiotic synthesis of the smaller cytosine (C) maintained an internal chemistry different and uracil (U) bases was accomplished. from that of their surroundings 2016 4. The origin of self-replicating molecules - the abiotic synthesis of RNA’s two purine bases, that eventually made inheritance possible adenine (A) and guanine (G) was demonstrated. 2.2 SYNTHESIS OF ORGANIC COMPOUND ON RNA monomers formed spontaneously from simple precursor molecules. EARLY EARTH Experiments showed that organic polymers (e.g., polypeptides, RNA) could form by dripping solutions of monomers onto hot sand, clay, or rock. Early atmosphere likely lacked oxygen and was rich These reactions occurred without enzymes or in water vapor, nitrogen, carbon dioxide, methane, cellular machinery. ammonia, and hydrogen. As Earth cooled, water vapor condensed into oceans, forming the environment for chemical 2.4 WHAT ARE PROTOCELLS? reactions. Oparin-Haldane Hypothesis (1920s): the Russian chemist Alexander I. Oparin and British scientist ★ refers to a compartment where replication of the J.B.S. Haldane primitive genetic material took place and where - proposed that the Earth's early primitive catalysts gave rise to products that atmosphere, low in oxygen, likely enabled accumulated locally for the benefit of the replicating organic compounds to form from cellular entity. inorganic molecules, fueled by lightning and UV radiation. Haldane proposed that For life to continue, organisms must be able to reproduce life began in the oceans, which he called a (make more of themselves) and carry out metabolism "primordial soup." (process energy to live and grow). GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 4 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer Early life forms, called protocells, might have information and replicate, especially within vesicles. These contained self-replicating molecules (like RNA) and vesicles could pass on their RNA to daughter vesicles, metabolism-like processes. These molecules would making them unique from other molecules. allow them to reproduce and obtain energy, both essential functions for life. Over time, protocells (early cell-like structures) that could replicate and pass on genetic information How did these self-replicating molecules and metabolic would have been more successful and increased in processes come together in early life forms? number. RNA could have acted as a template for DNA Vesicles are fluid-filled compartments enclosed by formation, as DNA is more chemically stable and a membrane-like structure, possibly creating the replicates more accurately. This transition to DNA right environment for life-like processes like was crucial as genomes became larger and more replication and metabolism. complex. - Vesicles form spontaneously when lipids and organic molecules mix with water, 2.6 FOSSIL EVIDENCE AND EARLY LIFE arranging into a bilayer similar to cell membranes. Hydrophobic molecules face Fossils have helped geologists establish a geologic inward, forming a barrier. record of Earth’s history. - Vesicles can reproduce by splitting and The fossil record of life is divided into Archaean, grow without losing contents. Some Proterozoic, and Phanerozoic eons. absorb montmorillonite and organic The first two eons lasted approximately 4 billion molecules, aiding in metabolism. years, while the third spans the last half billion years. - Some vesicles have a selectively permeable bilayer, controlling what enters and exits, which is crucial for metabolic STROMATOLITES Layered rocks formed by reactions and energy processing. prokaryotes, with ancestors dating back to 3.5 BYA. Fossils remained similar for ROLE OF MONTMORILLONITE CLAY hundreds of millions of years, mostly from shallow marine Montmorillonite clay helps organic molecules stick bays, and stromatolites still together, increasing the chance of vesicle formation exist today. and providing a surface for RNA molecules, promoting By 2.8 BYA, they appeared in chemical reactions. both marine and salty lake environments. This suggests single-celled organisms emerged around 3.9 BYA. 2.5 SELF-REPLICATING RNA RNA was likely the first genetic material due to its CYANOBACTERIA: Cyanobacteria, or blue-green algae, were versatility major photosynthetic organisms for a billion years. These - RNA molecules can function as catalysts bacteria are still crucial today. (ribozymes) and store genetic information. - Some ribozymes can replicate short RNA sequences if supplied with building blocks, 2.7 WAYS OF FOSSILIZATION functioning similarly to enzymes. 1. UNALTERED PRESERVATION - Small organism or part trapped in amber, hardened plant sap How RNA Replication occurs 2. PERMINERALIZATION/PETRIFICATION - The 1. Unlike double-stranded DNA, single-stranded RNA organic contents of bone and wood are replaced can adopt various 3D shapes, which are determined with silica, calcite, or pyrite, forming a rock like by its nucleotide sequence. Certain RNA sequences fossil replicate faster and with fewer errors. 3. REPLACEMENT - hard parts are dissolved and 2. RNA molecules best suited for their environment replaced by other minerals like calcite, silica, pyrite, and replication process will produce the most or iron copies. Occasionally, copying errors will create RNA 4. CARBONIZATION/COALIFICATION - the other shapes better suited for replication, driving natural elements are removed and only the carbon selection. remained 5. RECRYSTALLIZATION - hard parts are converted to The RNA World Hypothesis: Early life may have started in an more stable minerals or small crystals turn into “RNA world”, where RNA molecules could store genetic larger crystals GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 5 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer 6. AUTHIGENIC PRESERVATION - Mold and casts are lowermost formed after most of the organism have been deposition are the destroyed or dissolved oldest RELATIVE DATING This means that the fossil is compared to something for which an age is already known. Fossils that are identified to be found only within a very specific age span. Examining the layers of rock or strata can be also be useful RULES OF RELATIVE DATING 1. LAW OF SUPERPOSITION - When sedimentary rock layers are deposited, younger layers are on top of older deposits 2.8 TYPES OF FOSSILS 2. LAW OF ORIGINAL HORIZONTALITY - Sedimentary ★ MOLDS: Impression made in a substrate = negative rock layers are deposited horizontally. If they are image of an organism (e.g shells) tilted, folded, or broken, it happens later. ★ CASTS: When a mold is filled in (e.g bones and 3. LAW OF CROSS-CUTTING RELATIONSHIPS - if an teeth) igneous intrusion or a fault cuts through existing ★ PETRIFIED: Organic material is converted into stone rocks, the intrusion is YOUNGER than the rock it (e.g pertified trees, coal balls) cuts through. ★ ORIGINAL REMAINS: Preserved wholly (e.g frozen in ice, trapped in tar pits, desiccated insided caves Absolute Dating in arid regions) It is determined by the actual age of the fossil and ★ CARBON FILM: Carbon impression in sedimentary through radiometric dating using radioactive rocks (e.g leaf impression on the rock) isotopes ★ TRACE/ICHNOFOSSILS: Record the movements 2.10 PROKARYOTES and behaviors of the organism (e.g Trackways, tooth marks, gizzard rocks) Fossils of prokaryotic cells, dated 3.4 BYA, were found in: - Australian rocks (discovered in 2011). 2.9 HOW DO WE MEASURE THE AGE OF - South African rocks, resembling FOSSILS? cyanobacteria (photosynthetic bacteria). Prokaryotes were Earth’s sole inhabitants from 3.5 BYA to ~2.1 BYA. DATING THE FOSSILS - Can help a scientist establish its They transformed Earth by producing atmospheric position in the geologic time scale and find its relationship oxygen through photosynthesis. with the other fossils. 2.11 HOW OXYGEN WAS PRODUCED BACK RELATIVE DATING ABSOLUTE DATING THEN Based upon the Determines the Photosynthetic prokaryotes released free oxygen study of layers of actual age of the (O₂) into the water. rocks fossil Through photosynthesis, they produced oxygen, Does not tell the Uses radioactive which dissolved in water. As oxygen levels exact age: only isotopes like increased, it reacted with dissolved iron, forming compare fossils carbon-14 and banded iron formations (source of iron ore today). as older or potassium-40 Once all dissolved iron precipitated, oxygen began younger, Considers the to accumulate in the atmosphere, marking a depending on half-life significant shift in Earth's composition. This change their position in is evident from the rusting of iron-rich rocks around the rock layer. O 2.7 BYA. Cyanobacteria, the first oxygen-producing Fossils in the organisms, were key contributors to this uppermost rock transformation. layer/ strata are Oxygen levels gradually increased, with a rapid rise younger while from 1% to 10% of today's levels. Scientists suggest those in the GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 6 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer that this acceleration was linked to the emergence of eukaryotic cells containing chloroplasts. L3 MECHANISMS OF EVOLUTION IMPACT OF OXYGEN ON LIFE 1. Caused the extinction of many prokaryotic groups. 3.0 THEORY OF EVOLUTION 2. Some anaerobic species survived and have descendants today. All living organisms on Earth are related to one 3. Led to adaptations like cellular respiration another. The theory of evolution states that all living (harvesting energy using O₂).. organisms have a common ancestor, but because of millions of years of evolution, each of the organisms became what they are today. 2.12 EMERGENCE OF EUKARYOTIC CELLS AND MISCONCEPTION: A common misconception is ENDOSYMBIOTIC THEORY that evolution acts on individual organisms, but it actually acts on traits that affect the survivability and reproduction of organisms, with observable Endosymbiotic Theory: Eukaryotic cells likely effects over time in populations. evolved from prokaryotic cells through a process where certain prokaryotes began living within larger In 1977, a drought in host cells. the Galapagos Islands The theory suggests that mitochondria and reduced the medium chloroplasts were once free-living prokaryotes that ground finch became endosymbionts (cells living within another population. With fewer cell). soft seeds, finches with larger beaks PROCESS OF ENDOSYMBIOSIS survived better by eating hard seeds. 1. The host cell, a heterotroph, sustains itself This trait was through phagocytosis (engulfing other cells). inherited, increasing the average beak size 2. Mitochondria formed when bacteria capable of in the next generation. Natural selection favored larger aerobic respiration were ingested. beaks, changing the population over time. 3. Chloroplasts formed when photosynthetic some mechanisms: bacteria were engulfed. 1. Natural Selection: Acts to encourage traits and behaviors that increase an organism's chance for Over time, this relationship became mutually beneficial, survival and reproduction, while eradicating traits resulting in inseparable parts within the host cell. and behaviors that are disadvantageous. It can only select traits that are favorable, not create new ones. 2. Mutation: The force responsible for novel traits and Evidence Supporting the Theory behaviors. Mutation and other sources of variation, along with evolutionary forces, modify populations Both mitochondria and chloroplasts have an inner and species. membrane with enzymes and transport systems similar to prokaryotic plasma membranes. These organelles replicate through a process MACROEVOLUTION MICROEVOLUTION similar to certain prokaryotes. Mitochondria and chloroplasts contain a single, Processes that give rise to new Small-scale evolution, circular DNA molecule, similar to bacterial species and higher taxonomic changes in populations chromosomes. groups with widely divergent over time These organelles have the necessary machinery characteristics. (including ribosomes) to transcribe and translate their DNA into proteins, similar to their free-living ancestors. The ribosomes in mitochondria and chloroplasts are more like prokaryotic ribosomes than eukaryotic cytoplasmic ribosomes, based on size, RNA sequences, and antibiotic sensitivity. GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 7 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer 3.1 POPULATION GENETICS Founder Effect: When a small group leaves to form a new Branch of biology that studies genetic variation population, the genetic structure within populations and how this variation changes of the new population reflects that over time and geographical space. It provides of the original founders. insights into microevolutionary processes such as mutation, selection, gene flow, and genetic drift. GENE FLOW The movement of alleles in and out of a population due to migration of individuals or IMPORTANT TERMINOLOGIES gametes. Example: Plants use wind or Gene: A segment of DNA that Gene Pool: The total collection pollinators to spread pollen, contains the instructions for of genes and alleles present in introducing new genetic variation building a specific protein or the population of a species. It to different populations. RNA molecule, determining a includes all the genetic particular characteristic or variations found in the MUTATION Changes in an organism’s DNA function in an organism. breeding members of the that drive diversity and evolution. population. Mutations can be beneficial, Allele: A variant form of a harmful, or neutral. Beneficial gene. Each gene can have Allele Frequency: The mutations spread through the multiple alleles that can proportion or rate at which a population, while harmful ones are result in different traits or specific allele appears in a eliminated by natural selection. phenotypes, like the different population's gene pool. It is Some mutations have little to no blood types (A, B, O) in the expressed as a percentage or effect on an organism, while ABO system. a decimal, representing the others cause significant changes relative frequency of an allele to the phenotype. within the population. NONRANDOM Individuals may prefer to mate MATING with those of similar or different genotypes. Example: Female peahens prefer males with bigger, brighter tails, 3.2 MECHANISMS OF EVOLUTION leading to natural selection (factors affecting allele frequencies) favoring these traits. Assortative Mating: A preference MECHANISMS OF EVOLUTION for mating with individuals who are phenotypically similar. GENETIC DRIFT Occurs due to chance, where Disassortative Mating: Preference some individuals in a population for different are more likely to survive and genotypes/phentoyypes reproduce, passing on more genes. ARTIFICIAL Human intervention in selecting Example: A bigger, stronger male SELECTION which phenotypes will be gorilla becomes the alpha, mates beneficial. more, and passes on traits for size Humans have used artificial and strength, making future selection to produce crops and generations more powerful. animals with desirable traits, such Small populations are more as larger fruits or more milk affected by genetic drift, while production. large populations have a buffer against its effects. RECOMBINATION Genetic diversity can arise from recombination of DNA from two TWO CIRCUMSTANCES THAT CAN LEAD different cells. TO GENETIC DRIFT Example: In prokaryotes, recombination can spread Bottleneck Effect: A natural advantageous alleles, like disaster can randomly kill off a antibiotic resistance, promoting large portion of a population, adaptive evolution. dramatically changing its genetic structure. NATURAL The most famous and widely GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 8 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer SELECTION accepted mechanism of evolution. q² = frequency of homozygous recessive (yy) Occurs when individuals with favorable traits are more likely to The sum of these genotype frequencies is p² + 2pq + q² = 1. survive and reproduce, passing on those traits. Traits that improve survival and reproduction are selected, while harmful traits are eliminated over time. 3.3 HARDY-WEINBERG PRINCIPLE OF EQUILIBRIUM Describe populations that are not evolving According to Hardy-Weinberg, if a population is in equilibrium, its This principle states that allele and genotype genetic structure will not change over time. frequencies in a population will remain constant TERMS! from generation to generation in the absence of Polymorphism: The presence of two or more distinct phenotypes (or disturbing factors. allele variations) in a population. A population with polymorphism These disturbing factors include mutation, has different variations of a particular trait. migration, emigration, natural selection, and a finite Phenotypic Variation: The distribution of different phenotypes population size. (observable traits) among individuals in a population, influenced by both genetic structure and environmental factors. CONDITIONS FOR HARDY WEINBERG EQUILIBRIUM 1. No mutations - gene pool is modified if mutations 3.4 GENETIC VARIANCE occur 2. Random Mating - if individuals mate within a subset This refers to the diversity of alleles in a of population such as close relatives (inbreeding) population. It represents the differences in genetic random mixing of gametes does not occur and makeup that contribute to the variation in traits genotype frequency changes. among individuals within a population. 3. No neutral selection - Allele frequencies change A higher level of genetic diversity in a population when individuals with different genotypes show allows for more potential for adaptation to consistent differences (survival/reproductive environmental changes. success) If a population has low genetic variance, harmful 4. Extremely large population size - In small mutations can spread more easily, and beneficial populations, allele frequencies fluctuate by chance traits may be lost. Conversely, greater genetic (genetic drift) diversity provides a better buffer against 5. No gene flow - By moving alleles into or out of environmental changes and diseases. populations, gene flow can alter allele frequencies INBREEDING? Inbreeding is the mating of closely related individuals. It can lead to undesirable consequences, such as EQUATION FOR ALLELE FREQUENCIES bringing together harmful recessive alleles that might cause If there are two alleles for a gene (e.g., Y for yellow, y for green), genetic disorders or increase susceptibility to diseases. the frequency of the two alleles is represented by p and q, where: p = frequency of allele Y L4 PATTERNS OF DESCENT WITH q = frequency of allele y p + q = 1 (since there are only two alleles for this gene) MODIFICATION GENOTYPE FREQUENCIES 4.0 WHAT ARE SPECIES? The frequency of different genotypes in the population can be Mayr defined species as "groups of interbreeding predicted: natural populations that are reproductively isolated from other such groups." p² = frequency of homozygous dominant (YY) 2pq = frequency of heterozygous (Yy) GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 9 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer Species is a group of populations whose members have the potential to interbreed in nature and e.g, male fireflies produce species-specific flashing produce viable, fertile offspring but do not produce patterns to attract females. Females only respond to their viable, fertile offspring with members of other such own species' patterns, preventing mating with other groups. species. Mechanical Isolation 4.1 BIOLOGICAL SPECIES CONCEPT (BSC) Structural differences in reproductive organs prevent defines species based on the ability of individuals successful mating. to exchange genes and reproduce. 1. The BSC is based on genetic features, like the In flowering plants, the shape of the flower is adapted to ability to exchange genes. specific pollinators. Plants with incompatible flower 2. It's a reproductive community, a gene pool, and a shapes and pollinator types fail to transfer pollen. genetic system. Gametic Isolation 3. Reproductive isolation can occur in several ways, including when: Incompatibilities between egg and sperm prevent - Individuals can't mate. fertilization. Sperm and egg cells of different species - Their offspring aren't viable. have specific proteins that allow them to recognize each - Their offspring aren't fertile. other. If the species are different, sperm may not 4. The BSC is useful for defining plant and animal recognize or interact properly with the egg. Additionally, species. It doesn't apply to all organisms, such as sperm may not survive or be mobile enough to reach the egg in another species. asexual and parthenogenetic organisms. Post-zygotic isolation mechanisms: Allow fertilization but 4.2 REPRODUCTIVE ISOLATION MECHANISMS result in nonviable, weak, or sterile hybrids. Pre-zygotic isolation mechanisms prevent fertilization and POST-ZYGOTIC ISOLATION zygote formation. PRE-ZYGOTIC ISOLATION Hybrid Inviability Geographic, Ecological, or Habitat Isolation The fertilized egg fails to develop properly, and the embryo dies early in its development. This can occur This occurs when populations are physically separated by when genetic incompatibility prevents normal growth. geographical barriers (mountains, rivers) or occupy different habitats within the same area (such as different Hybrid Sterility altitudes or ecosystems). Hybrids may survive and develop, but they are sterile and e.g two populations of flies may live in the same cannot reproduce. geographical area, but one group lives in soil while the other lives on water’s surface, preventing them from This typically occurs due to issues during meiosis, where meeting and reproducing. abnormal chromosome segregation results in the inability to produce viable gametes. Temporal/Seasonal Isolation A common example is the mule, a hybrid between a horse different species or populations reproduce at different and a donkey, which is sterile. times of the year, season, or day, preventing interbreeding. Hybrid Breakdown e.g fruit fly species like Drosophila persimilis (active in the Hybrids from the first generation (F1) may appear normal, morning) and Drosophila pseudoobscura (active in the vigorous, and viable, but when these hybrids reproduce, afternoon). their offspring (F2 generation) are weak, sterile, or both. Behavioral Isolation This breakdown in fitness occurs over generations and is often due to genetic incompatibilities that manifest in Differences in mating behaviors prevent species from later generations. mating. GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 10 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer 4.3 MODES OF SPECIATION L5 DEVELOPMENT OF EVOLUTIONARY 1. Allopatric Speciation (Geographic Speciation): THOUGHT - Members of a population become geographically isolated, preventing gene flow. ARISTOTLE viewed species as fixed - Over time, the isolated populations diverge (unchanging). due to natural selection, mutation, and Concluded that life-forms could be arranged on a ladder, or scale, genetic drift. of increasing complexity, later called the Scala Naturae (“scale of 2. Peripatric Speciation: nature”) - Occurs when small groups of individuals break off from the larger group and form a CAROLUS developed the two-part, or new species LINNAEUS binomial, format for naming - Unique characteristics in the smaller group species (binomial classification) published a pamphlet Systema become prominent over generations, Naturae (Systems of Nature) leading to speciation. Grouping similar species into increasingly inclusive categories. 3. Parapatric Speciation: - Occurs when the groups that evolved to be THOMAS Published “Essay on the Principle separate species are geographic ROBERT of Population” (1798), “An Inquiry MALTHUS Into the Nature & Progress of Rent neighbors. (1815). And “Principles of Political - Gene flow occurs but with great distances Economy (1820). is reduced. There is also abrupt change in "Population must always be kept the environment over a geographic border down to the level of the means of and strong disruptive selection must also subsistence.” happen. GEORGES Founded vertebrate paleontology CUVIER proposed the Theory of 4. Sympatric Speciation: Catastrophism based on - Happens within the same geographic paleontological evidence in the location, where populations share the Paris Basin. same habitat. He noticed several gaps where all - Abrupt genetic changes (e.g., polyploidy) evidence of life would disappear lead to reproductive isolation. and then abruptly reappear again - Example: Polyploidization in plants, where after a notable amount of time. chromosome number changes rapidly, JAMES Founder of Modern Geology creating new species. HUTTON “Theory of Gradualism” profound changes to the Earth, such as the Grand Canyon, are due to slow continuous processes and not part of catastrophes CHARLES Author of “Principles of Geology” LYELL Proposed the “Theory of Uniformitarianism” Geological changes that occurred in the past were still occurring and that the same rules were in effect JEAN Principle of use and disuse BAPTISTE Inheritance of Acquired LAMARCK Characteristics Physiological needs drive Lamarckian evolution No extinction of species. GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 11 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer species. This helped him hypothesize that the Galapagos Species disappeared because they just evolved into different was colonized by species. species from mainland South America and then diversified His claim was later on disproved giving rise to different species (on different islands). LAMARCKISM 5.1 MORE ABOUT CHARLES DARWIN Proposed that species can change over time that new species come from pre-existing species, and that all species share a common ancestor. Published On the Origin of Species by Means of Natural Selection (commonly referred to as The Origin of Species) IDEAS FROM THE ORIGIN OF SPECIES Descent with Modification - Explains three broad observations about nature— a. the unity of life, 5.0 CHARLES DARWIN b. the diversity of life, and Darwin embarked from England on the Beagle in c. the adaption/striking ways in which December 1831. organisms are suited for life in their Used the theories and principles proposed by environments. James Hutton, George Cuvier, and Charles Lyell by providing evidence suggesting Earth was far older Natural selection is the mechanism behind “descent with than a couple of thousand years ago. modification” He viewed the history of life as a tree, with multiple THE VOYAGE OF THE BEAGLE branching from a common trunk out to the tips of - The primary mission of the 5 year voyage of the the youngest twigs beagle was to chart poorly known stretches of the South American coastline 1. Primary mission of the voyage is to chart poorly known stretches of the South American coastline 2. Darwin observed and collected thousands of plants and animals 3. Noted organisms’ special features that enabled them to survive diverse environments 4. Associated species of plants and animals in South America’s temperate and tropical regions as more closely related species than species of the temperate regions of Europe TO SUMMARIZE: 5. Fossils found in South America resemble living - Natural selection is a process in which individuals species in that same region that have certain heritable characteristics survive 6. Read Lyell’s Principle of Geology and reproduce at a higher rate than other 7. Saw fossils of aquatic organisms in the Andes individuals. (mountain region), and accounted for many - Over time, natural selection can increase the match earthquakes that may have happened. These between organisms and their environment. observations affirmed his learning from Lyell. - If an environment changes, or if individuals move to 8. The voyage reached Galapagos where he observed a new environment, natural selection may result in finches. There were finches unique to the island adaptation to these new conditions, sometimes while there were others that resembled the giving rise to new species in the process. mainland GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 12 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer DARWIN’S 5 POINTS OF NATURAL SELECTION 1. Population has variations 2. Some variations are favorable 3. More offspring are produced than survive 4. Those that survive have favorable traits 5. A population will change over time. - Individuals in a population have traits that vary - Many of these traits are heritable (passed from parents to offspring) - More offspring are produced than survive - Competition is inevitable - Species generally suit their environment Darwin inferred that: - Individuals that are best suited to their environment are more likely to survive and reproduce - Over time, more individuals in a population will have the advantageous traits In other words, the natural environment “selects” for beneficial traits L6 PHYLOGENY 5.2 LAMARCK VS DARWIN 6.0 PHYLOGENETIC A branching diagram that represents the evolutionary history of a group of organisms. ROOTED UNROOTED There is a single ancestral Unrooted trees do not lineage to which all show a common ancestor organisms represented in but do show relationships the diagram relate among species. GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 13 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer 6.1 PARTS OF A PHYLOGENETIC TREE THE PHYLOGENETIC TREES It represents a hypothesis about evolutionary relationships. Phylogenetic trees do show patterns of descent. Phylogenetic trees do not indicate when species evolved or how much genetic change occurred in a lineage. It shouldn’t be assumed that a taxon evolved from the taxon next to it. 6.3 INFERRING PHYLOGENY Organisms with similar morphologies or DNA sequences are likely to be more closely related than Terminal taxa are connected by branches. The organisms with different structures or sequences. ▪ branches are the line segments that make up the When constructing a phylogeny, systematists need tree. Branches come together at branching points to distinguish whether a similarity is the result of called nodes. Each nodes/branch represents a homology or analogy. common ancestor shared by two or more terminal - Homology is similarity due to shared taxa. ancestry. - Analogy is similarity due to convergent ROTATING AROUND BRANCH POINTS evolution. - Rotating the branches of a tree around a branch point does not change what they convey about Convergent evolution occurs when similar environmental evolutionary relation- ships. pressures and natural selection produce similar /analogous - As a result, the order in which taxa appear at the adaptations in organisms from different evolutionary branch tips is not significant. What matters is the lineages. branching pattern, which signifies the order in which the lineages have diverged from common ANALOGOUS HOMOLOGOUS ancestors. - Note: The order of the taxa does NOT represent a Characters that have Characters having similar sequence of evolution "leading to" the last taxon separate evolutionary OUS structures because shown (in this tree, humans). origins, but are superficially these were derived from a similar because they common ancestor perform the same function. 6.4 WHAT IS CLADISTICS Studies relationships between taxa using shared derived characters CLADE: Includes an ancestral species and all of its descendants. Can be nested in larger clades, but not all groupings of organisms qualify as clades. ★ MONOPHYLETIC: Group I, consisting of three 6.2 WHAT WE CAN AND CANNOT LEARN FROM species (A, B, C) and their common ancestor 1, is a GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 14 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer monophyletic roup (clade), meaning that it consists of an incestral species and all of its descendants. ★ PARAPHYLETIC: Group II is paraphyletic, meaning that it consists of an ancestral species 2 and some of its descendants (species D, E, F) but not all of them (does not include species G). ★ POLYPHYLETIC: Group III, consisting of four species (A, B, C, D), is polyphyletic, meaning that the most recent common ancestor of its members is not part of the group. CLADISTICS SYMPLESIOMORPHY SYNAPOMORPHY is a character that an evolutionary originated in an novelty unique to ancestor of the a particular clade. taxon Trait or character homologies that that are shared are common to all from a recent KEY POINTS members of a common ancestor group and indicate a shared The lengths of the tree’s branches do not indicate the ancestry degree of evolutionary change in each lineage. The chronology represented by the branching pattern of the tree is relative (earlier versus later) rather than 6.5 CONSTRUCTING A CLADOGRAM absolute (how many millions of years ago). But in some tree diagrams, branch lengths are proportional to the amount of evolutionary change or to the times at which particular events occurred. Each branch length of the phylogenetic tree reflects the number of changes that have taken place in a particular DNA sequence in that lineage. Branch lengths can indicate time. L7 THREE DOMAINS OF LIFE 7.0 CAROLUS LINNAEUS Swedish botanist classified everything on Earth into three kingdoms: animal, vegetable (plants), and mineral (nonliving) popularized the taxonomic hierarchy Father of Modern Taxonomy Developed the BINOMIAL NOMENCLATURE LINNAEUS’ 7 LEVELS OF CLASSIFICATION KINGDOM The biggest group of organisms PHYLUM A group of related classes (e.g chordata w/backbone) GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 15 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer - Ernst Haeckel: German zoologist who proposed a CLASS A group of related orders (e.g Mammalia - mammals, Reptilia - third kingdom “Protista” reptiles) - Herbert F. Copeland: American botanist who proposed a separate kingdom for the bacteria, ORDER A group of related families (primates, Kingdom Monera (1930) carnivora) - Roger Yate Stanier & Cornelius B. Van Niel: Classified all living things as prokaryotes and FAMILY A group of related genus (Hominidae - eukaryotes. humans, apes) GENUS A group of related species (Homo, 7.1 ROBERT WHITTAKER canis, felis) American Ecologist SPECIES A group of related organisms (sapiens, Proposed the five-kingdom system domestica, mindorensis) 7.2 THE 5 KINGDOM SYSTEM MODERN SYSTEM OF CLASSIFICATION DOMAIN Highest level constitutes three KINGDOM prokaryotes domains of life (Archaea, bacteria, MONERA nicellular organisms eukarya) has cell wall made up of peptidoglycan Then, KINGDOM, PHYLUM, CLASS, ORDER, FAMILY, show different modes of GENUS, SPECIES nutrition KINGDOM eukaryotes PROTISTA Incredibly diverse Majority are unicellular Varied modes of nutrition Can be animal-like or plant-like protists. KINGDOM eukaryotes FUNGI can be heterotrophic , saprophytic or parasitic have cell walls made up of chitin immobile KINGDOM Eukaryotes PLANTAE Autotrophs immobile multicellular have cell walls made up of cellulose KINGDOM eukaryotes ANIMALIA heterotrophs mobile multicellular HOWEVER! - John Hogg: British Naturalist who proposed the fourth kingdom “Protoctista” (1860) GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 16 GENERAL BIOLOGY REVIEWER S.Y. ‘24 - ‘25 | 2ND SEM Q3 by: ry lorraine – cramer 7.3 THREE DOMAINS OF LIFE 7.4 BINOMIAL NOMENCLATURE Bi = two Nomial = portion NOMENCLATURE means naming system HOW TO WRITE THE SCIENTIFIC NAME? - Genus and species - Latin or Greek - Italicized in print - Underlined when handwritten - Capital Genus but NOT species HUMAN: Homo sapiens GOOD LUCK! GBIO SEM2 Q3 REVIEWER PAGE 17

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