Unit 4 Review
Darwin Longhand (~4 sentences)
-A long time ago, some individuals of the ancestral population of the _____________ experienced a mutation that led to the ability ___________________________. -Because this mutation occurred in sex cells (or unicellular organisms), the trait was heritable. -Individuals with the trait of _________________ had a greater fitness than those without it because, individuals with the ability _________________________ allowed them to _______________________ (something that helps them survive better). -The trait of ___________ then became more frequent in the population of the _________________ over multiple generations.
Inheritance of Acquired Characteristics
-Proposed by Lamarck -not a true theory -behavioral changes modified traits & these traits were then inherited by offspring -ex. giraffes --> feeding on top leaves stretched neck/legs & this trait was then passed on to next generations
Founder Effect
-a few individuals of the original population move to a new location and found a new population -the few individuals are a random sample of the population; they don't move for a specific reason (not because of the trait) -allele frequency often changes from original population
Homology
-a similarity that occurs due to descent from a common ancestor
Lactase Persistance
-all mammals can digest lactose as babies, because of the enzyme lactase, but as they get older, the gene for lactase is stopped being transcribed due to the selective & differential nature of transcription -1/3 of humans can still digest lactose into adulthood as they continue to have the lactase enzyme, making them lactase persistent -in lactase persistent people, the gene for lactase does not get turned off when it should & the gene remains on -a T-C switch in the noncoding region of the gene
Acclimation
-an individual being fitted to its environment (a phenotypic change)
Vestigial Structures
-anatomical features that have no current function but resemble structures of their presumed ancestors
Evolution
-any change in allele frequency within a population over time/generations
Stabilizing Selection
-average remains the same, but the extremes don't do well
Genetic Drift
-changes in allele frequency within a population that occurs due to random chance -more likely to occur in a small size population -not likely in infinitely large populations
Disruptive Selection
-extreme values become favored -the most common trait is no longer good
Evidence for Evolution
-fossil records, radiometric dating, genetic information, the distribution of organisms around the world, and physical similarities shared by different species -vestigial traits
Gene Flow
-immigration/emigration of individuals in a population
Natural Selection
-individuals with heritable traits that make them better suited to their native environment tend to flourish & reproduce, where as other individuals are less likely to survive & reproduce -certain traits become more prevalent in a population over time
5 Evolutionary Mechanisms
-mutation -gene flow -genetic drift -nonrandom mating -natural selection
Biological Success
-not determined by the survival of individuals, but by FITNESS (# of viable offspring each individual produces)
Mutations
-occur by random chance in any cells within any individuals -S phase for point mutations -meiosis (prophase 1) for chromosomal mutations -for mutations to be heritable, the mutation must occur in a sex cell
Descent with Modification
-passing traits from parent to offspring -species change over time, give rise to new species, & share a common ancestor -a fundamental idea behind Darwin's theory of evolution
Hardy Weinberg Principle
-provides the null hypothesis for evolutionary studies -predicts the allele frequency within a population when evolution is not taking place
Misconceptions of the Typical Picture for Evolution
-shows only an individual, but evolution is based on population -shows only a few generations, but evolution is usually much, much longer -it suggests that the human form is the end goal of evolution, but evolution doesn't have an end goal; also the human form is just one of many other successful ways if living - we are not at the top -it does not show the branching/tree view of evolution -it shows evolution too linearly, but evolution sometimes has setbacks & it is much more messy
Homoplastic Trait
-similar traits that have evolved independently in different lineages
Bottleneck Effect
-some members of the original population die due to random chance events (ex. plague, natural disaster)
Homologous Structures
-structures that are similar to each other because they evolved from a common ancestor
Phylogeny
-the evolutionary history of a species or group of related species
Directional Selection
-the most common trait shifts
Population
-the number of organisms of the same species that live in a particular geographic area at the same time with the ability of interbreeding -unit of evolution -in order to measure allele frequency, you need more than an individual (you need a population)
Adaptation
-the process by which a species becomes fitted to its environment -the result of natural selection acting upon heritable variation over several generations -a trait is considered an adaptation when: it is prevalent among individuals within a population, it increases the fitness of individuals
4 Postulates
-traits are variable among individuals of a population -traits are heritable -there's a difference in fitness among individuals of the population -the difference in fitness is due to the variable trait
Convergent Evolution
-two species from different lineages have independently evolved similar characteristics because they occupy similar environments -analogous structures = convergent traits (similar characteristics) -ex. wings of bats & birds -contrasts with evolution by common ancestry
Balancing Selection
-works to keep the distribution the same as it is
Hardy Weinberg Equations
Allele Frequency: p + q = 1 Genotype Frequency: p2 + 2pq + q2 = 1 -You can compare the predicted/calculated frequencies to the actual/observed frequencies - if they're the same, evolution is not taking place; if they're different, evolution is taking place
True/False: Evolution occurs only by the process of natural selection.
False -evolution can occur by any of the 5 mechanisms (mutation, gene flow, genetic drift, nonrandom mating, or natural selection)
True/False: An individual organism is capable of evolving because evolution is one of the criteria for "life".
False -evolution happens in a population, not within an individual
True/False: Mammals are more evolved compared to bacteria.
False -mammals are more complex, but not more evolved -both species have been doing well in their environments for just as long as the other, so it cannot be a comparison of who is more evolved
True/False: Natural selection involves a population trying to adapt.
False -natural selection is a natural process based on mutation & other random events/environmental conditions, so there is no "end goal" they are "trying" to get to
True/False: Natural selection occurs by random chance.
False -the traits that arise may be random, but the actual process of natural selection is not -some individuals have a greater chance of surviving than others based on the traits they have
True/False: Evolution progresses toward perfection.
False -there is no goal in evolution - no perfect way of living or perfect form of life; it's all about picking what is best from what is available
True/False: An individual organism is capable of adapting to the environment.
False -an individual acclimates; adaptation is for a population/species
Charles Darwin's Birthday
February 12, 1809
Hardy Weinberg Assumptions
For NO evolution.... -no mutation -no gene flow -no natural selection -no genetic drift -random mating If all of these are met, then a population is not evolving and it is at Hardy Weinberg Equilibrium.
Publication Date for the Origin of Species
November 24, 1859
True/False: Adaptation only occurs by the process of natural selection.
True
