Exam 1 Flashcards
Ch. 20, 21, 22, 23
Evolution
- Descent with modification
- Genetic change in a population over multiple generations
- How an entity changes through time
Descent
The inheritance of traits
Modification
The change in inheritable traits
Genetic Variation
The differences in alleles of genes found within individuals in a population
Darwin’s 3 Main Ideas
- Descent with modification explains life’s unity
- Descent with modification explains life’s diversity
- Descent with modification explains how organisms are suited to life in their environments
Allele Frequencies
frequencies of alleles of a gene from generation to generation
Population Genetics
The study of properties of genes in a population
What is the Hardy-Weinberg Principle
- It describes how allele and genotype frequencies in a population remain constant over generations, under certain conditions
- Provides a baseline expectation for genetic variation in a population, assuming that no evolutionary forces are acting on it
Hardy-Weinberg Equilibrium
- Allele frequencies in a population will remain in equilibrium from one generation to the next if the following five conditions are met:
1) No mutation occurs
2) No Gene Flow (No Immigration or Migration occurs)
3) Random mating is occurring
4) The population size is large
5) No natural selection is occurring
5 Agents of Evolutionary Change
- Mutation
- Gene Flow
- Genetic Drift
- Nonrandom mating
- Natural Selection
Gene Flow
The movement of alleles from one population to another
- Animal physically moves into a new population
- Drifting of gametes or immature stages of plants or animals into an area
- Mating of individuals from adjacent populations
Nonrandom Mating
Assortative Mating
- Phenotypically similar individuals mate
- Increases the proportion of homozygous individuals
Dissasortative Mating
- Phenotypically different individuals mate
Produces excess of heterozygotes
Genetic Drift
Allele frequency may change by chance due to a small population
- Can lead to loss of alleles in isolated populations and uncommon alleles
Ex. Founder Effect and Bottleneck Effect
Founder Effect
One or a few individuals disperse and become the founders of a new isolated population
- Some alleles are lost and others change in frequency
- Huge diversity —> Small diversity
Bottleneck Effect
A drastic reduction in population size due to a sudden environmental change
- Results in loss of genetic verity
Fitness
The most fit phenotype is the one that produces the greatest number of offspring
Parental Investment
The energy and time each sex invests in producing and rearing offspring
Intrasexual Selection
Individuals of one sex compete with each other for the opportunity to mate
Intersexual Selection
Mate choice
- When the female gets to choose the mate based off characteristics they want
Secondary Sexual Characteristics
Characteristics that attract the opposite sex
Sexual Dimorphism
Differences between sexes
Sperm Competition
Features that increase the probability that a male’s sperm will fertilize an egg
Sensory Exploitation
Evolution in males of a signal that attracts the opposite sex
Frequency-Dependent Selection
The fitness of a phenotype depends on its frequency within the population (The success of a trait is not constant; it changes depending on how common or rare it is)
- fitness (reproductive success) of a phenotype or genotype depends on its frequency relative to other phenotypes or genotypes in the population
Negative Frequency-Dependent Selection
When rare phenotypes are favored by selection
- Rare forms are preyed upon less frequently
Positive Frequency-Dependent Selection
When common phenotypes are favored by selection
- Eliminates variation
- Oddballs are preyed upon
Oscillating Selection
Selection favors one phenotype at one time and another phenotype at another time
Heterozygote Advantage
Heterozygotes are favored over homozygotes
Disruptive Selection
Acts to eliminate intermediate types (middle ground/medium sized)
Directional Selection
Acts to eliminate one extreme (eliminates either big or small/leans towards having more of either one)
Stabilizing Selection
Acts to eliminate both extremes (eliminates big and small but not medium individuals)
Constructive Gene Flow
Spread beneficial mutation to other populations
Constraining Gene Flow
Can impede adaptation by a continual flow of inferior alleles from other populations
Darwin’s Selection Hypothesis
- Phenotypic variation must exist in the population
- Variation must lead to differences among individuals in lifetime reproductive success
- Phenotypic variation among individuals must be genetically transmissible to the next generation
Industrial melanism
Phenomenon in which darker individuals come to predominate over lighter ones
Artificial Selection
The process by which humans intentionally breed plants or animals to promote the occurrence of desirable traits.
Experimental Selection
When scientists intentionally apply specific pressures (like environmental changes or selective breeding) on a group of organisms in a controlled setting, such as a lab, to see how their traits change over generations
Agricultural Selection
The process by which humans intentionally breed plants and animals to enhance desirable traits for farming
Domestication
The process by which humans tame and breed wild animals or cultivate wild plants over many generations to develop traits that are more beneficial or desirable for human use
Fossil
The preserved remains of once-living organisms
How are fossils created
- Organism is buried in sediment
- Calcium in bone/other hard tissue mineralizes
- Surrounding sediment hardens to form rock
Homologous Structures
Structures with different appearances and functions that all derived from the same body part in a common ancestor
Vestigial Structures
Have no apparent function, but resemble structures ancestors possessed
Pseudogenes
Non-functional sequences of DNA that resemble functional genes but have lost their ability to code for proteins due to mutations
Biogeography
Study of the geographic distribution of species
Convergent Evolution
The process in which unrelated or distantly related organisms independently evolve similar traits or features due to having to adapt to similar environments or ecological niches
Darwin’s Critics
1) Evolution is not solidly demonstrated (just a theory)
2) There are no fossil intermediates
3) The Intelligent Design Argument
4) Evolution violates the Second Law of Thermodynamics
5) Proteins are too improbable
6) Natural Selection do not imply evolution
7) The Irreducible Complexity Argument
Speciation
The process by which one species splits into two or more species
Microevolution
Consists of changes in allele frequency in a population over time
Macroevolution
Refers to broad patterns of evolutionary change above the species level
Biological Species Concept
- A group of populations who members have the potential to interbreed in nature and produce viable, fertile offspring
- They do not breed successfully with other populations
How do species form
- Reproductive Isolation
Reproductive isolation
The existence of biological barriers that impede two species from producing viable, fertile offspring
Hybrid
The offspring between different species
Reproductive Isolation can be classified by
Prezygotic Barriers (before fertilization) and Postzygotic Barriers (After fertilization)
Prezygotic Barriers
Block fertilization from occurring by:
- Impeding different species from attempting to mate
- Preventing the successful completion of mating
- Hindering fertilization if mating is successful
Habitat Isolation
(Prezygotic)
When two species encounter each other rarely, or not at all, because they occupy different habitats
- Not isolated by physical barriers
Temporal Isolation
(Prezygotic)
Species that breed at different times of the day, different seasons, or different years cannot mix their gametes
Allochrony
(Prezygotic)
Species using the same area or resource, but at different times
Behavioral Isolation
(Prezygotic)
Courtship rituals and other behaviors unique to a species are effective barriers
Ex. When different courts in ACOTAR have different ways of showing love (making love)
Mechanical isolation
(Prezygotic)
Morphological differences prevent successful mating
Gametic isolation
(Prezygotic)
Sperm of one species may not be able to fertilize eggs of another species
Postzygotic Barriers
Prevent the hybrid zygote from developing into a viable, fertile adult by:
- Reduced hybrid viability
- Reduced hybrid fertility
- Hybrid breakdown
Reduced Hybrid Viability
(Postzygotic)
Genes of the different parent species may interact and impair the hybrid’s development or survival
Reduced Hybrid Fertility
(Postzygotic)
Even if hybrids are vigorous, they may be sterile
Hybrid Breakdown
(Postzygotic)
Some first generation hybrids are fertile, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile
The biological Species Concept cannot be applied to
fossils or asexual organisms
The Morphological Species Concept
Defines a species by their structural features
- Applies to sexual and asexual species byt relies on subjective criteria
The Ecological Species Concept
views a species in terms of its ecological niche
- Applies to sexual and asexual species
- Emphasizes the role of disruptive selection
The Phylogenetic Species Concept
Defines a species as the smallest group of individuals on a phylogenetic tree
- Applies to sexual and asexual species
- Can be difficult to determine the degree of difference required for separate species
Speciation can occur in two ways:
- Allopatric Speciation
- Sympatric Speciation
Allopatric Speciation
Forms a new species while geographically isolated (different country)
Sympatric Speciation
A subset forms a new species without geographic separation (same country)
What is interrupted in allopatric speciation
Gene Flow is interrupted when a population is divided into geographically isolated subpopulations
What can happen in allopatric speciation
Two populations may evolve independently through:
- Mutation
- Natural Selection
- Genetic Drift
- Reproductive Isolation may arise as a result of genetic divergence
Sympatric Speciation occurs when
Gene Flow is reduced between groups that remain in contact through factors including:
- Polyploidy
- Habitat Differentiation
- Sexual Selection
Polyploidy
The presence of extra sets of chromosomes due to accidents during cell division
- Offspring have reduced fertility
Autopolyploid
An individual with more than two chromosome sets, derived from one species
- Offspring have reduced fertility
Allopolyploid
A species with multiple sets of chromosomes derived from different species
- Cannot interbreed with either parent species
Sympatric Speciation can also result from:
- Habitat differentiation
- Sexual Selection
Hybrid Zone
A region in which members of different species mate and produce hybrids
hybrids usually have reduced
Fitness compared to their parent species
When closely related species meet in a hybrid zone, what are the possible outcomes
- Reinforcement
- Fusion
- Stability
Reinforcement
Occurs when hybrids are less fit than the parent species
- Natural Selection reinforces reproductive barriers, and lowers the rate of hybridization over time
Fusion
Fusion of the parent species into a single species may occur if the hybrids are as fit as the parents
- Allows substantial gene flow between species
Stability
Stability of the hybrid zone may be achieved if extensive gene flow from outside the hybrid zone overwhelm selection
- Increased reproductive isolation inside hybrid zone
Punctuated Equilibria
Species experience long periods of relative stability (equilibrium) in their evolutionary history, punctuated by short, rapid bursts of significant change
Macroevolution
The cumulative effect of many speciation and extinction events
Systematics
The study of evolutionary relationships
Phylogeny
The evolutionary history of an organism, including which species are closely related and in what order related species evolved
- Often represented in the form of an evolutionary tree.
Ancestral Characteristics
Similarity that is inherited from the most recent common ancestor of an entire group
Derived Characteristic
Similarity that arose more recently and is shared only by a subset of the species
Cladistics
A technique used for creating hierarchies of organisms that represent true phylogenetic relationship and descent
- Classifies organisms by common descent
Phylogenetic Tree
Represents a hypothesis about evolutionary relationships
Rooted Tree
includes a branch to represent the most recent common ancestor of all taxa in the tree
Sister Taxa
Groups that share an immediate common ancestor
Basal Taxon
Diverges early in the history of a group and originates near the common ancestor of the group
Polytomy
A branch from which more than two groups emerge
Cladogram
Depicts a hypothesis of evolutionary relationships
Clade
a group of species that share a common ancestor
Synapomorphy
Derived character shared by clade members
Plesiomorphies
ancestral states
Symplesiomorphies
Shared ancestral states
Homology
Similarity due to shared ancestry
Analogy
Similarity due to convergent evolution
Hemoplasies
Analogous structures or molecular sequences that evolved independently
Homoplasy
A shared character state that has not been inherited from a common ancestor
- Can result from convergent evolution and evolutionary reversal
Parsimony
Favors the hypothesis that requires the fewest assumptions
Maximum Parsimony
Assumes that the tree that requires the fewest evolutionary events is the most correct one (The one that most likely happened)
Molecular Homologies
Similarities at the molecular level (such as in DNA, RNA, or proteins) between different species that indicate a common evolutionary ancestry
Molecular Clock
The rate of evolution of a molecule is constant through time
- Divergence in DNA can be used to calculate the times at which branching events have occurred
Taxonomy
The science of classifying living things
Binomial Nomenclature
The two part scientific name of a species (Also know as a Binomial)
What’s the first part of a Binomial Nomenclature called
genus
What’s the second part of a Binomial Nomenclature called
Specific Epithet
What part is capitalized and what part is italicized in a Binomial Nomenclature
- First letter of genus is capitalized
- The entire species name is italicized
Name the Hierarchical Classifications from broad to narrow
King Phillip Came Over For Good Soup
- Domain
- Kingdom
- Phylum
- Class
- Order
- Family
- Genus
- Species
Monophyletic Group
Includes it’s ancestor and all descendants
Paraphyletic Group
Includes some but not all descendants of an ancestor
Polyphyletic Group
Includes some with different ancestral lineage
Biological Species Concept (BSC)
Defines species as groups of interbreeding populations that are reproductively isolated
- Cannot be applied to allopatric populations
- Can be applied only to sexual species
Phylogenetic Species Concept (PSC)
Defines that species is a population or set of populations characterized by one or more shared derived characters
- Can be applied to both sexual and asexual species
