Biology 1101 Weeks 7, 8, 9 Bundle
Biology 1101 Weeks 7, 8, 9 Bundle BIOLOGY 1101 - 0100
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BIOLOGY 1101 - 0100
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This 29 page Bundle was uploaded by Alexa Notetaker on Monday March 21, 2016. The Bundle belongs to BIOLOGY 1101 - 0100 at Ohio State University taught by Dr. Kristin Smock in Spring 2016. Since its upload, it has received 113 views. For similar materials see Biology in Biology at Ohio State University.
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Date Created: 03/21/16
Biology 1101 Week 7 Notes Exceptions to Mendel’s Laws: § There are some situations in which phenotypic ratios do not conform to Mendel’s predictions Incomplete Dominance: § Red and white flowers return in th2generation § The single copy of the red allele (R) in the heterozygote codes for less pigment production than 2 copies of red (R) do § Incomplete dominance occurs when a heterzygote has an intermediate phenotype between the 2 homosygotes § Sounds like the theory of “Blended Inheritance” BUT this is NOT true Polygenic traits: § Polygenic traits- depend on more than one gene o Most inherited traits are polygenic o The phenotype reflects the activity of more than one gene o Example: eye color is encoded by multiple genes Environmental Effects: § Skin color is a polygenic trait that is influenced by the environment EVOLUTION: Prevailing viewpoint before Darwin: § The Earth was young (6,000 years old) § Each species was created at the same time and does not change or die out § The number of species never changes o Then found fossils of Mammoths, Giant Gorund sloth, and Irish Elk o Then noticed similar species with key differences Scientists (do not need to memorize): Georges Buffon: Suggested that the earth was much older than previously believed Georges Cuvier: documenting fossil discoveries Jean-Baptiste Lamarck: Suggested that living soecies might change over time Charles Lyell: Argued that geological forces had gradually shaped the earth and continue to do so (plate tectonics, formation of volcanoes, etc.) Prevailing Viewpoints: § Advances in science led to awareness of changes in lines of descent of species § 18 - and 19 - century naturalists tried to reconcile traditional beliefs with evidence of change What is evolution? § Evolution is genetic change in a population over time § Evolution is not a theory centered around the origin of life on earth o Most evolutionary biology focuses on how life has changed and diversified over time, regardless of how it started Voyage of HMS Beagle: § Darwin’s observations on a voyage around the world in 1831 led to new ideas about species What Darwin never knew: § Darwin’s interest in o Similarities in traits (extinct vs living species) o Differences in traits (finches) § Notices variation in beaks in finches between islands § Depends on food source- Thick short beaks for breaking seeds and thin long beaks for getting pollen out from flowers o Artificial selection (be able to describe what this is) Darwin, Wallace and Natural Selection: § 1858: Wallace sent Darwin his ideas on evolution by natural selection § both presented at a conference § Darwin published On the Origin of Species in 1859 (sold out on the first day) Theory of Natural Selection: § Natural selection o Differential survival and reproduction among individuals of a population whose traits vary o One mechanism of evolution § à Some individuals survive better & reproduce more than others in that population 3 conditions for Natural Selection: 1. Variation for a trait a. Example: speed in rabbits 2. Heritability a. Example: each rabbit representing a different speed has offspring 3. Differential reproductive success a. Example: predators are able to catch up with the slower rabbits, and therefore are dying. So over time, the amount of faster rabbits should increase in the rabbit population. • More offspring produced than can survive • Competition for resources • Some are better competitors, increases ability to survive & reproduce (pass along trait that made them successful) • Note: We are talking about the average phenotype in a population (change in population, NOT individual) Theory of Natural Selection continued: • Heritable traits that allow for greater reproductive success become more common in a population over time • Fitness is a measure of relative reproductive success o “Survival of the Fittest” § Could be the fastest, could be camouflage, could be an effective defense mechanism (like venom) Evolution by Natural Selection: • The result of natural selection is a population that is well- adapted to its current, local environment o NOT a “perfect” organism o Environment is always changing, so its important that organisms are changing to fit the environment § Adaption- traits that positively influence the survival and the chance of reproduction • Pocket mice- able to blend in on red sand, but on black rock, they were obvious • Dark mouse first appeared from a mutation, and this dark mouse was able to blend into rock better, concealing it from predators • Then this dark mouse was able to reproduce and create darker colored mice • This population was created black because they reproduce so quickly • NOTE: Mutations are random but natural selection is NOT random • • Evolution can (and does) repeat itself o Example: Pocket mice hundreds of thousands miles apart both became darker colored • Evolution is NOT progressive • In each generation, the alleles that code for traits with better fitness tend to increase in frequency o “good enough” individuals survive Artificial selection- the differential reproductive success is determined by humans rather than nature • If the environment changes, which alleles are favored may also change o Traits may no longer be adaptive o Example: Dark lava rock forming, change form light background to dark background “…evolution produces a tree, not a ladder, and we are just one of many twigs on the tree.” • Charles Darwin sketched a diagram of an evolutionary tree showing • Phylogenetic Tree Average beak size evolution example: In years of drought, bigger, thicker beaks are favored. However, during wet years, smaller beaks are favored. • NOTE that average beak size within a population continues to fluctuate according to the food supply. 3 Modes of Natural Selection: • Natural Selection may favor the: 1) Intermediate Phenotype a. “Stabilizing selection” b. What length tail is better in the environment? c. 2) One Extreme Phenotype a. “Directional Selection” b. longer tails have more stabilityà population shifts towards the longer tail length 3) Both extremes in phenotypes a. “Disruptive Selection” b. Stabilizing Selection: • Intermediates phenotype favored; extreme phenotypes less fit • Example: Birth weight in humans (Less & more than average 7 lb. babies were at risk of mortality) Directional Selection: • One extreme phenotype is most fit • Average color shifts over time • Example: Peppered Moth o Camouflage was better with peppered coloration o Then, pollution caused colors of the tree to change, and then the darker colored moth was favored Disruptive Selection: • Extreme phenotypes are favored; intermediate phenotype selected against • Coho Salmon: o Male will defend territory o Female will lay eggs, then male has the right to fertilize those eggs o Stronger, larger males are able to defend their territory and therefore are able to reproduce o Small males are not able to defend territory. They are still fit because they are able to sneak into territory and fertilize a bunch of eggs and have offspri ng • Can lead to the evolution of two separate species Mechanisms of Evolution: 1) Natural Selection o Sexual Selection 2) Mutation 3) Migration 4) Genetic Drift Mechanism: Sexual Selection: • Some traits confer greater fitness because they are attractive to the opposite sex • Birds of paradise • Darlington’s Peacock Spider o Call attention of drab females by brining up brightly color abdomen and shake & shimmy • Manakin Courtship o Survival risk is outweighed by securing a mate with beautiful, bright feathers OR cleaning the area for a courtship dance Mechanism: Mutation: • Mutations can create a new allele in an individual o Creates a change in allele frequency in the population o Evolution with the mechanism of mutation • The ultimate source of genetic variation in a population o Fuels evolution • Misconception: mutations arise when “needed” o If mutation is beneficial, it will become more prevalent in the population o RANDOM PROCESS Evolution of Antibiotic Resistance: • Staph is susceptible (killed) by Penicillin (in 1940’s) • Some bacteria are naturally resistant to penicillin (mutation) o All the resources to themselves o More reproductively fit (more offspring) à therefore, soon all of the infection is resistant • Today, most Staph bacteria is resistant to penicillin o MERSA is completely resistant to all antibiotics Mechanism: Migration: • Migration into and out of a population affects gene flow o After a group of individuals migrates form one population to another, both populations can experience a change in their allele frequencies and, consequently, experience evolution. Mechanism: Genetic Drift • Genetic Drift is a change in allele frequency that occurs purely by chance o Example: Tsunami destroys entire environment (plants and animals) and effects the iguana population o Totally random event wiped them out o Much more pronounced in small populations than large populations § In small population, there is less genetic diversity o Populations that survive is completely by luck o The Founder’s Effect- § A group of individuals may leave a population and become the founding members of a new, isolated population § The new population will be dominated by the genetic features present in the founding members (higher allele frequency) o Genetic Bottleneck- § The new population will be dominated by the genetic features present in the surviving members § Totally random which beads “fall out of the bottle” • Allele frequency changes • Example: Northern elephant seals have reduced genetic variation o Hunting in the late 1800’s reduced population size to ~100 individuals (blubber for lamp oils) o Now more than 150,000, but the population lacks the level of genetic diversity seen in less intensely hunted population Week 8 Biology 1101 Notes Macroevolution: • Small changes (microevolution) lead to large scale changes in life’s panorama (macroevolution) o Example: Grand Canyon was formed by the Colorado River (many small changes over many years) • Over time, changes in allele frequency in a population can lead to new species Species Concepts: • How do we define “species”? o “The concept of a species is a fuzzy one because humans invented the concept to help get a grasp of the diversity of the natural world.” o Morphological Species Concept: § Physical bodies; bone structures; pattern of teeth o Phylogenetic Species Concept § Evolutionary relatedness between groups; similarities in DNA, RNA or protein; would they be grouped together on the tree o Biological Species Concept § Most commonly used; § Two individuals belong to the same species if they can reproduce and offspring must be viable (survive) and fertile (reproduce) Speciation- one species is split into two or more species • Requires genetic divergence and reproductive isolation (look below for more on isolation) -Species are important for humans so we know what animals are poisonous or if it’s dangerous Reproductive isolation: • BSC emphasizes reproductive isolation, which m akes gene flow between groups impressible • Reproductive isolating mechanisms prevent gene flow between species • Pre-zygotic isolation- prevent fertilization (no zygote can be formed) • Example: o Ecological isolation- desert fox and arctic fox live in such different environment, therefore, they are never in contact and are therefore in pre-zygotic isolation (never come in contact) o Temporal isolation: not active/fertile at different times (One cricket mates in one season and another kind of cricket mates in different season) o Behavioral isolation: different activities are not attractive to another species (different flash patterns of firefly species) o Gametic isolation: Gametes cannot unite; “lock and key”; gametes only fit with the same species • Post-zygotic isolation- prevent viable/fertile offspring • Examples: o Hybrid inviability- Gametes unite, but cannot produce a viable embryo (goat and sheep) o Hybrid infertility- hybrids lack the ability to make or deliver viable gametes (ex: liger, the hybrid offspring of a lion and a tiger) Kruthi Bhat Spatial arrangements and isolations: • Allopatric speciation occurs when a geographic barrier (river, canyon, mountain, etc.) causes one group of individuals to be reproductively isolated from another group (the end result, the two cannot reproduce together) • Sympatric speciation- occurs in the absence of a physical barrier o Example: Cichlid fish in Africa- shallow versus deep water fish because shallow water has a different environmental pressures than the deeper water (l ight, plants, viability, etc.) Reproductive Isolation cont.: • Speciation: the splitting of one species into two or more species o Requires reproductive isolation and genetic divergence Adaptive radiation- a speciation event on steroids- the splitting into multiple species EVIDENCE: Fossil Record: • The fossil record offers physical evidence of past life o Change over time • Missing links: fossils that demonstrate a link between groups of species believed to have a shared o Tiktaalik § Transition between one lifestyle and another (fish and land animals) § Fins turned into arm like structures where it could prop itself up and crawl out of the water § Defensive mechanism to “get out of the way” of predators § No genetic recipe The fossil record is incomplete: • Favors species with: o Hard parts o Dense populations o Wide distribution o Persisted a long time Biogeography: • Biogeography: study of the distribution of species across the planet • Related organisms originated in one place, then spread to other accessible places, adapted to their new environment o Example: Placental mammals: Group of mammals that are able to nourish unborn offspring through a placental. o Marsupials- offspring are born underdeveloped and continue nourishment in a pouch § Land-bridge between North & South Americas are able to compete • Placental mammals outcompeted marsupials in competition for land, so placental mammals took over • However, in Australia, there is no competition, so there are more marsupials and more of a diversity Comparative Anatomy: • Similarities in patterns of embryonic development suggest shared ancestory. • Relationships among the embryos (early development) • Because they are so similar, the ancestor that links all of thee would have a similar development • Organisms with very different ways of life often share common anatomical structures due to descent from common ancestors o Homologous structures § Similar body parts that reflect shared ancestry § Bone patterns in limbs (one bone, two bones, gaggle of bones, then digits) o Convergent Evolution: § Similar characteristics due to similar environmental conditions, although they are not closely related (Evolved INDEPENDANTLY) • Ex: Porcupine and hedgehog are not related but rather have been in similar environmental pressures o Analogous Structures § Result of convergent evolution § Did not evolve in shared ancestor (Evolved INDEPENDANTLY) • Example: Bats, birds, and insects all have wings o Vestigial Traits: § Evolution is not perfection § Examples of traits that are hold overs from past ancestors § Links modern day species with past ancestors § No good evolutionary reason to be weeded out § Example: Goosebumps (help insulate body heat when you have a lot of hair), Tailbone, whale’s hipbones Molecular Data: • All species use the same genetic code and the same 20 amino acids • Most likely inherited from a common ancestor o Cytochrome C: a protein used in ETC Science and Religion? • Dichotomy? o Testable & Falsifiable using the scientific method o Scientists cannot test if there is a god o We do not day if there is a god involved or not • Nature of science is different from religion • Science does not and cannot confirm or refute the involvement of a higher being Write a scenario that explains Biology 1101 Week 9 Notes: Virus: • Many scientists do not consider to be alive o Don’t respond to stimuli o Cannot reproduce on their own o DNA and RNA Viral Replication: • Virus attaches to host membrane • Goes to host cell nucleus • Nucleus replicates virus’s DNA • Make viral proteins • Sometimes the virus will then burst out of host cell, killing the host cell in the process The evolutionary Tree of Life: Understanding Phylogenies: • “Understanding a phylogeny is a lot like reading a family tree” • Time is on the vertical axis (read from bottom to top) • Nodes represent speciation events o Ancestral lineage • Tips represent descendants of that ancestor • We can use phylogenies to understand patterns of shared ancestry among species • Unique vs shared history • B and C are more closely related than either are to A • “…each lineage has ancestors that are unique to that lineage and ancestors that are shared with other lineages- common ancestors.” • Read at the NODES • Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like • Reading left to right indicates nothing about level of “advancement” • These phylogenies are equivalent: Misconceptions about Human Evolution : • The phylogeny of living species most closely related to us looks like this: • It is a common misconception It is important to remember that: • Humans did not evolve from chimpanzees • Humans and chimps are “evolutionary cousins” and share ancestor common ancestor that was neither chimpanzee nor human • Humans are not “higher” or “more evolved” than other living lineages. Since or lineages split, humans and chimps have each evolved traits unique to their own lineages Classification System: • Did – DOMAIN o Bacteria o Archaea o Eukarya • King – KINGDOM o Protists o Plants o Fungi o Animals • Philip – PHYLUM o Chordata • Come – CLASS o Mammailia • Over – ORDER o Artidactyla • For – FAMILY o Giraffidae • Good – GENUS o “Giraffa” • S – SPECIES Bacteria: • Split between bacteria and archaea/eukarya • All share a common ancestor • Single-celled prokaryotes • Asexual reproduction o Horizontal gene transfer o Mechanisms: Bacterial Classification: • Three basic shapes: o Coccus (round) o Bacillus (rod) o Spirillum (spiral) • Gram Stain o Differentiates between 2 major groups o Based on cell wall structure § Gram positive: cell walls allows absorption of color § Gram negative: Structure of cell wall do not absorb stain as much and remain a light pink • Important to know so we know what kind of antibiotic to treat with Bacteria and Antibiotic Use: • Taking antibiotics could kill off “good bacteria • When residential bacteria outweigh the harmful bacteria, they can out compete the harmful bacteria and kill it off • When they do not, the left over harmful bacteria are the founders of a new population and next time Patient B takes the drug, it will be ineffective (needs stronger) o Critically important to take all of your antibiotics Benefits of Bacteria: • “Normal flora” • Probiotic therapy: swamp your body with benign/helpful bacteria to outnumber harmful bacteria o Fight bacteria with bacteria Archaea: • Similarities with Bacteria: o Appearance o Prokaryotes o Single-celled • But molecular comparisons revealed bif differences o DNA o Cell wall o Flagella • “Extremophiles” o Hydrothermal vents o Acidic water o Salty water § Most proteins would denature • Found almost everywhere o Including in your intestines § Break down recalcitrant bonds in beans, release methane • Can’t break down beans but archaea can § Gut- “Microbial community” EUKARYA (nucleus, membrane-bound organelles, uni- and multi- cellular) Protists: • Extremely diverse o Share one feature: eukaryotes • Defined by exclusion o Do not belong to ant other kingdom • Classification being reconsidered o May be as many as 20 kingdoms • May be reclassified eventually “Plant-like” Protists: • Algae: photosynthetic protist living in water • Range in size o May be uni- or multi- cellular o Important source of energy for environment o Kelp forest- largest § “Fish nurseries” • Use different photosynthetic pigments o Yellow, gold, brown, red and green “Fungus-like” Protists: • Plasmodial Slime molds • Cellular slime molds • Slime mold • Water mold o Irish potato famine o Single-celled but they behave as a “super-organism” o Produced by cell division, therefore they have the same genes “Animal-like” Protists: • Most uni-cellular o All animals are multi-cellular • Giardia o Boil water when camping • Chagas disease • African sleeping sickness • Malaria o Caused by protist but transmitted by mosquitos Fungi: Basics • Domain: Eukarya • Kingdom: Fungi • Similar to plants, but… o Lack chloroplasts o Do not photosynthesize o Some are unicellular (ex: yeast) o Heterotrophic § Mostly decomposers o Have chitin in cell walls § Chitin in animal kingdom • Fungi are more closely related to animals than plants (phylogeny) Fungi: Structure: • The body of most fungi is a network of thin filaments o Provides a large surface area for absorbing nutrients o Penetrates the fungus’s food source o Secrete enzymes that break down organic molecules o Absorb resulting nutrients TYPES of fungi: Fungi: Yeasts: • Yeasts are unicellular fungi • Useful for producing alcoholic beverages and bread • Used in genetic experiments requiring a simple eukaryotic cell Fungi: Chyrids: • Primitive fungi that produce swimming spores o Flagellum • “The worst infectious disease ever recorded among vertebrates in terms of the number of species impacted, and its propensity to drive them to extinction” o amphibians worldwide Fungi: Mycorrhizae: • Mycorrhizal fungi form symbiotic relationships with plants o Aids plants in absorption of nutrients in exchange for carbohydrates (glucose from photosynthesis) o Mutually beneficial relationship o Very common o Form sheath over plant root (access to a lot more nutrients) Fungi: Lichens: • Relationships between fungus and photosynthesizer (green algae or cyanobacteria) • Can live in extreme conditions and is important in making soil, but is sensitive to pollution (don’t need soil for nutrients) • Lichens can secrete enzymes into rocks and digest it into soil • Help ecosystems recover from degraded state of life Plants: Basics • Domain: Eukarya • Kingdom: Plantae • Multicellular Eukaryotes • Well-developed tissues • Mostly terrestrial and sessile o Ensure light source • Exhibit embryo protection o Nourish growing embryo • Photoautotrophic o “self-feeders” Plants: Major Groups: Plants: Life on Land: • Green Algae (protists) live surrounded by water o Water, minerals o Support o Reproduction Plants: Life on Land (475 mya) • To adapt to life on land, plants evolved features that allow them to… o Resist drying out (absorb and retain water) o Absorb nutrients o Stand upright without outside support o Reproduction not dependent on water • These features appeared over time Plant Adaptations: 1. Embryo protection • All plants nourish a multicellular embryo in the body of the female plant o This feature distinguishes plants from green algae • First appeared in the non-vascular plants (the bryophytes) • First node 2. Vascular Tissue • Distinguishes vascular plants form non -vascular plants • Xylem: o Water absorbed and transported through xylem o Water & nutrients absorbed from roots and then transported up toward the leaves • Phloem: o Take the sugars produced in photosynthesis and transport throughout the plant § Also provides structural support (grow vertically and stay upright) 3. Seeds • Distinguishes plants with seeds from the seedless vascular plants • Seed: an embryo and stored nutrients within a protective coat (2) Non-vascular Plants (Bryophytes) • Simplest, most primitive plants • Lack roots and vascular tissue o Water and nutrients move by diffusion o Small in size o Dependent on water for reproduction • Example: Mosses, liverworts, hornworts (3) Seedless Vascular Plants: • Includes club mosses, horsetails, and whisk ferns • First to evolve vascular tissue o Larger than bryophytes as a result • Uses spores for reproduction o Single-cell: DNA, RNA, proteins o Wind-dispersed Vascular Seed Plants (Gymnosperms): • The first plants to evolve seeds; use seeds for dispersal rather than spore • Most are cone-bearing (conifers) • “Naked seeds” – pinecones – not enclosed by a fruit • Do not produce flowers or fruit • Examples: Conifers: pine, spruce, cycads, ginkos • 160 mya, gymnosperms dominated forests • Very successful o Deserts to tundra o Sea level to tree line o Taller and older than any other plants
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