Evidence for Evolution Study Guide

Evolution Study Guide theory of evolution - the process of evolution explains the diversity and unity of life - species change over time - the modern species are a result of descent with modification evidence for evolution - evidence comes from direct observations, fossil records, homology, and biogeography - direct observations: we can literally watch a species change over time (ex. insect populations become resistant to pesticides) - a form of microevolution - fossil records: characteristics in modern species can be seen in past fossils - descent with modification is clear in the fossil records of modern species - characteristics in modern species can be connected to fossil ancestor - homology: characteristics in related species can have underlying similarity even with differing functions - homologous structure: similar anatomy from common ancestors - embryonic homologies: similar early development - vestigial organs: structures with little to no use - molecular homologies: similar DNA and amino acid sequences - biogeography: geographic distribution of species - pangea phenotypic diversity - descent with modification - new forms appearing in fossil records - all species descended from a few original types of life - modification by natural selection - those who have traits that allow them to survive, survive and then reproduce → new traits keep getting passed on as they allow them to survive better in their environment - variation exists in every population due to random changes in a heritable genetic information - in a given environment, there will be overpopulation that leads to competition - some individuals adapt better so that they can get the resources they need more easily - the better-adapted individuals reproduce and pass on those traits evolutionary fitness - the ability to survive and pass on traits is defined as evolutionary fitness - the more alleles you pass on the more “fit” you are considered heterozygote advantage - it is when a single allele doesn’t cause disease but is instead good for the person - ex. sickle cell trait that protects from malaria in heterozygotes but causes disease in homozygotes types of selection on phenotype frequencies - directional selection - an extreme phenotype is favored over other phenotypes causing allele frequency to shift over time (in the direction of that phenotype - ex. larger black bears can survive extreme cold better than small ones - disruptive (diversifying) selection - extreme values for a trait are favored over the intermediate values - ex. small beaks for small seeds, large beaks for large seeds - stabilizing selection - intermediate values for a trait are favored over the extreme values - ex. a narrow range of human birth weight genetic drift, gene flow, mutation, and sexual selection - genetic drift - change in the gene pool of a population due to random chance (the population is small or limited to a geographic range) - bottleneck effect: - the majority of a population is wiped out - alleles found in survivors will greatly influence future generations - leads to a loss of genetic diversity - the founder effect - a small group of individuals split off a larger population - descendants have a disproportionate showing of traits - gene flow - movement of individuals or gametes/spores between populations - can alter allele frequencies in a population without any selective pressure - can decrease the fitness of a population or increase the fitness - ex. windblown pollen moves these alleles between populations (is beneficial to the plant life near the mines, but not further out) - mutation - - random mutations can introduce new alleles into a population - different individuals having specific alleles sexual selection - “reproduction of the fittest” - even if a trait hinders survivability, it may still help them reproduce - logic is that if the male survived with the trait, they must have some genetic advantage - intense competition between males biological species - a group of populations whose members have the potential to interbreed in nature and produce fertile offspring (exceptions: hybrids) - other definition of species: - ecological model - distinguishes species by their ecological roles or habitat - morphological model - distinguishes species by key structural differences reproductive isolation - premating isolating mechanisms - geographic separation / allopatric speciation - a physical barrier divides a population - sympatric speciation - live in same place but does not interbreed - temporal isolation - gametic isolation - mechanical isolation - habitat isolation - behavioral isolation - different pollinators - postmating isolating mechanisms - gamete incompatibility - sperm cannot fertilize the egg - hybrid inviability - hybrids do not survive or cannot reproduce (behavioral wise) - hybrid infertility - egg and sperm do not develop (cannot reproduce) speciation - punctual equilibrium - more immediate - graduated equilibrium - more gradual - polyploid speciation - two different plants reproduce and then there's a baby plant and it gets 2 sets of chromosomes so now there's a new hybrid species and it fertilizes itself evolutionary origins - fossil records - lower rock layers have simpler the organisms - evidence of transitional animals (fish → amphibians) - homology - homologous structures - embryonic development - vestigial structures - molecular homology early earth - earth formed about 4.6 billion years ago - prokaryotes came at around 3.8 billion years ago - how did life arise - small organic molecules were synthesized - small molecules → macromolecules - were packaged into protocells - self-replication molecules allowed for inheritance - Oparin and Haldane - early atmosphere: h2o vapor, n2, h2, h2s methane, ammonia - energy: lightning and uv radiation - conditions favored synthesis of organic compounds - Miller and Urey - tested Oparin-Haldane hypothesis - simulated conditions in lab - produced amino acids - proved that organic molecules can be created from inorganic molecules - abiotic synthesis - RNA monomers have been produced spontaneously from macromolecules - - - small organic molecules polymerize when concentrated on hot sand, clay, or rock protocells - may have been fluid-filled vesicles with membrane-like structures - vesicles with RNA capable of replication are called protocells - in water, lipids and other organic molecules can spontaneously form vesicles with a lipid bilayer - adding clay and increase the rate of vesicle formation - vesicles exhibit simple reproduction and metabolism and maintain an internal chemical environment the first genetic material was probably RNA and not DNA - RNA molecules called ribozymes have been found to catalyze many different reactions - natural selection has produced self-replicating RNA