Micro and Macroevolution Spring 2024 PDF

Micro and Macroevolution Chapter 8  What we know about genetics Each individual has a genetic blueprint (genotype) that determines their physical and physiological characteristics (phenotype) ○ Variation of genotype exists among individuals of...

Micro and Macroevolution Chapter 8  What we know about genetics Each individual has a genetic blueprint (genotype) that determines their physical and physiological characteristics (phenotype) ○ Variation of genotype exists among individuals of the same species Individuals pass on heritable traits to offspring ○ Sexual reproduction and meiosis Gene pool: all the alleles that exist within a population  Genetics Terminology Genetics: branch of biology that focuses on the inheritance of traits Heredity: transmission of traits from parent to offspring; inheritance Trait: characteristic of an individual Gene: a sequence of DNA that codes for a specific protein Allele: different versions of a gene Genes and Inheritance  Genotype vs. Phenotype Phenotype: observable features of an individual ○ Ex. Yellow seeds, white flowers Genotype: the alleles found within a particular individual ○ One allele from mother and one from Codes for father Only one allele expressed as the phenotype ○ Denoted as letters Genotype Phenotype Ex: YY or Yy for yellow seeds  Characterizing the Genotype Dominant allele: allele that determines the phenotype of a heterozygous individual ○ Denoted with a capital letter. Ex:Y or R Recessive allele: allele whose phenotype is only expressed in homozygous individuals ○ Denoted with a lowercase letter. Ex: y or r Homozygous: having two identical alleles of a certain gene ○ Ex:YY or yy Heterozygous: having two different alleles of a certain gene ○ Ex:Yy or Rr  Genetic Diversity Genetic diversity: genetic variation among individuals of the same species Adaptive potential ○ Disease resistance ○ Antibiotic resistance  Types of Evolutionary Change Microevolution: evolutionary change resulting from a change of the allele frequencies of a population Macroevolution: Large-scale change occurring over long periods of time that results in the formation of new species (speciation) 2 species 1 species Time Microevolution in Captive Tigers  How does microevolution occur? Population: Individuals of the same species that live in the same area at the same time and have the potential to interbreed Five mechanisms of evolutionary change within a population 1) Mutation 2) Gene flow 3) Genetic drift 4) Natural selection 5) Sexual selection  Mutation Mutation: a permanent change in an organism’s DNA Are random ○ *Organisms can not will change Primary way new alleles are created Only mutations that affect reproductive cells can be inherited Can be positive (beneficial) or negative (deleterious) towards fitness ○ Deleterious mutations eliminated through purifying selection  Mutation: Sickle Cell Anemia A single mutation alters the shape of the hemoglobin Sickle shaped red blood cells can clog blood vessels causing pain and death Images from evolution.berkeley.edu and web.md.com  Beetle Case Study: Mutation 1) Mutation occurs in the DNA of a beetle resulting in a new brown phenotype 2) Brown beetle survives and produces offspring, increasing frequency of allele for brown phenotype in the population Mutated gene results in brown coloration Image from evolution.berkeley.edu  Gene Flow Gene flow: the movement of alleles from one population to another Random with respect to fitness Occurs through migration of individuals Can reduce genetic differences between populations  Beetle Case Study: Gene Flow Individuals with brown allele in genotype migrate to a different population and increase genetic variability of new population  Genetic drift Genetic drift: a random shift in change in the allele frequencies of a population Often due to random mating and death within a population Random with respect to fitness Reproduction results in increase in homozygous recessive individuals Most pronounced in small populations  Genetic drift A subset of the population First generation Second generation Third generation will reproduce each A gene frequency =.5 a gene frequency =.5 A gene frequency =.7 a gene frequency =.3 A gene frequency = 1 a gene frequency = 0 generation. Those who die and those who reproduce each generation is random. Frequency of alleles can shift depending on which individuals reproduce ○ Can lead to loss of alleles  Beetle Case Study: Genetic Drift By random occurrence the brown alleles increased in the second generation  Genetic Drift Genetic drift is most pronounced in smaller populations  Genetic Drift in Small Populations Genetic bottleneck: a sudden reduction in the alleles of a population Ex. Elephant seals Genetic Bottleneck  Genetic Drift in Small Populations Founder effect: a change in allele frequencies that occurs when a new population is established Alleles of founders are random with respect to fitness Alleles of founders shape the alleles of the new populations  Natural Selection Natural selection: The process by which individuals with certain heritable traits tend to produce more surviving offspring than do individuals without those traits ○ Natural “selection” is a non-random process ○ Only process to consistently influencing adaption of within a population's  Natural Selection Selective pressure: Any factor that reduces the survival and/or reproductive success of a portion of the population ○ Environmental conditions Temperature, rainfall ○ Predation/prey Evolutionary arms race  Natural Selection Biological fitness: ability of an individual to produce viable offspring, relative to other individuals of the same species ○ “Survival of the fittest” Adaptation: heritable trait that increases the fitness of an individual relative to individuals lacking that trait in the same environment ○ Adaptations do not occur because of want or need  Artificial Selection Artificial Selection: the selective breeding of plants or animals for a desired trait.  Beetle Case Study: Natural Selection Green beetle phenotype is easier for predator to find against brown bark. Green genotype is reduced and brown phenotype is increased in population  Natural Selection: Peppered Moth Peppered moth Two morphs ○ Gray with black spots ○ Black In 1848 gray morph ≈ 98% of population, by 1900 black morph ≈ 95% of population ○ Industrial revolution Coal factories covered forests in soot Increased environmental standards has led to an increase in gray morph  Natural Selection: Bacteria Antibiotic resistance: rapid evolution in bacteria that is the result of selection by antibiotics and the rapid reproduction and variation in bacteria Mutated bacteria with antibiotic resistant gene Population Bacteria divide and one Antibiotic resistant New population of of bacteria bacteria contains a mutation bacteria survives antibiotic resistant bacteria grows  Natural Selection: Human Disease Disease resistance: some individuals within the population have genes that make them resistant to certain diseases Bubonic plague Ebola and HIV Natural Selection: Galapagos Finches  Natural Selection: Sickle Cell Anemia Sickle cell anemia is a recessive trait Carriers have strong resistance to malaria Carriers of sickle cell trait selected for in malaria stricken regions  Coevolution Coevolution: the process where two species reciprocally influence the other’s evolution Predator and prey interactions Competitive species Mutualistic relationships ○ Pollinators and plants  Evolutionary Arms Race Evolutionary arms race: Coevolution between predator and prey species where adaptations in one species influence the evolution of counter adaptations in the other species Garter snake and rough skinned newt  Sexual Selection Sexual selection: members of one sex choose their mates based on certain traits or behaviors. ○ Typically female choice ○ Males often compete for mates ○ Can have fitness trade-offs (bright colors are easy for predators to see) ○ Can lead to sexual dimorphism: phenotypic differences in the males and females of the same species  Mechanisms of Microevolution Mutation: A permanent change in an organism’s DNA. Random with respect to fitness Gene flow: The transfer of alleles from one population to another. Random with respect to fitness Genetic drift: The shift in the allele frequencies of a population due to random mating or death Natural Selection: The process by which individuals with certain beneficial traits produce more surviving offspring than individuals without those traits. Sexual Selection: The process by which individuals with certain desirable traits reproduce more than individuals without those traits. Summary of Evolutionary Mechanisms Mutations are they only mechanism to produce new alleles Genetic drift and gene flow are greatest in small populations Natural selection can produce adaptations Mutations, genetic drift and gene flow are random while natural selection and sexual selection are non-random Mechanisms of microevolution are precursors to large scale change (Macroevolution)  Check Your Understanding True or False: Evolution occurs when some individuals in a population survive longer than other individuals in the population True or False: Mutations in somatic cells can result in evolutionary change True or False: Genetic drift is more pronounced in small populations  Check Your Understanding Which of the following mechanisms of evolutionary change are non-random with respect to fitness? a. Gene flow b. Mutation c. Natural selection d. Genetic drift  Check Your Understanding Which of the following is not an example of natural selection? a. The evolution of antibiotic resistant bacteria b. A sudden reduction in alleles due to a genetic bottleneck c. The addition of new alleles to a population d. The coevolution of predator and prey species e. More than one of the above is not an example of natural selection  Evolution of a New Species Microevolution: Small-scale evolutionary change resulting from a change of the allele frequencies of a population Macroevolution: Large-scale evolution occurring over long periods of time (geologic time) that results in the formation of new species (speciation) Speciation: Development of a new species through evolutionary processes  What is a Species? Biological species concept: species are groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups Reproductive isolation: the inability of individuals from two populations to produce offspring with each other, thereby making it impossible for gene exchange between the populations Between 3 million and 15 million species exist on earth ○ Only 1.8 million species have been described ○ 99% of all species that have existed are extinct!  How Do New Species Arise? Geographic separation of population into two or more separate populations that no longer interbreed ○ Geological event ○ Migration into a new area Shift in allele frequencies of separate populations ○ Genetic drift, natural selection, gene flow, sexual selection, mutation Changes in allelic frequencies of populations results in differences that prevent individuals from each population from interbreeding with one another  Describing Species Ways species differ Physical appearance ○ Adaptations Behavior ○ Mating behavior ○ Vocalizations Geographic range Habitat type Ecological niche DNA ○ Molecular differences  Evolution After Geographic Isolation Allopatric speciation: speciation that results from the geographic isolation of populations by a barrier that prevents interbreeding between populations  Vicariance vs. Dispersal Vicariance: splitting of an organisms native range through the formation of a barrier to gene flow Dispersal: movement of organisms to locations outside of their native range 🡪 California gnatcatcher Black-tailed gnatcatcher 🡪 Chimpanzee Bonobo  Allopatric Speciation Common in island chains (archipelagos) ○ Ex. Drosophila on Hawaiian Islands  Adaptive Radiation Adaptive radiation: process in which organisms diversify rapidly, especially when exposed to a new environment with different challenges, new resources, and available niches ○ After mass extinction events Cambrian explosion ○ Archipelagos Galapagos finches  Biotic Interchange Biotic interchange: when barrier between previously separated biotas breaks down, resulting in drastic changes to biodiversity Great American Biotic Interchange Isthmus of Panama connected North and South America ○ Heading south: Bear, Cat, Camel, Horse, Elephant, Dog and Pig families ○ Heading north: Anteater, Porcupine, Armadillo, Sloth, and Possum families  Biotic Interchange Connection of North and South America at the Panama isthmus led to the vicariance of the pork fish populations.  Speciation Without Isolation Sympatric speciation: speciation without geographic separation ○ Ecological niche: The role of a species within its ecosystem ○ Polyploidy: organisms containing more than two paired sets of chromosomes Most common in plants  Evolutionary Novelties Novel and complex structures arise from gradual modifications to existing structures https://youtu.be/c4lrEM6Txtk  Evolutionary Trends Evolutionary trends are not goal oriented Interactions between organisms and their current environment drive evolution, not the desire for certain traits Classifying Organisms: Taxonomy Domain Kingdom Phylum (plural, phyla) Class Order Family Genus (plural, genera) Species  Phylogenetic Trees Phylogeny: evolutionary history of a group of organisms Ancestral trait: a characteristic that existed in an ancestor Derived trait: a characteristic that is a modified form of an ancestral trait Synapomorphy: a shared, derived characteristic ○ Used to support evolutionary relationships Phylogenetic trees can be used to depict taxonomic classification and evolutionary relationships 1 = Last common ancestor between Mustelidae and Canidae 2 = Last common ancestor between coyotes and gray wolves Interpreting Phylogenetic Trees Synapomorphies are placed on the phylogeny to depict the groups with the derived traits Interpreting Phylogenetic Trees Eggs Hair Can be rotated on axes and still represent same evolutionary history Interpreting Phylogenetic Trees  Check Your Understanding True or False: Given enough time microevolutionary changes can result in speciation True or False: Populations of the individuals that can interbreed but are geographically separated are considered different species True or False: Sympatric speciation occurs when two populations of the same species are geographically separated  Check Your Understanding What are the two ways that speciation can occur? What are the names of the different processes? Provided an example of each type of speciation.  Check Your Understanding Write the names of the listed organisms in the correct location in the phylogeny below. Place the synapomorphies in the correct location on the phylogeny. Species list Bat Wolf Coyote Bear Eagle Rabbit Mouse Adaptations Feathers Backbone Mammary glands Carnassial teeth (flesh eating teeth)