Chapter 15: Processes of Evolution Flashcards
What is evolutionary theory?
It is a bundle of theories
Who was Jean Baptiste Lamark?
He was an evolutionary biologist that studied the evolution giraffes neck.
Charles Darwin was the first of what?
He was the first one to articulate a plausible mechanism for evolution that was derived from different fields of study.
What is Thomas Robert Malthus known for?
Population growth is potentially exponential while the growth of the food
supply is linear. Only a fraction of any population will
survive and reproduce.
Uniformitarianism Theory
is the assumption that the same natural laws and processes that operate in our present-day scientific observations have always operated in the universe in the past and apply everywhere in the universe
What did Darwin do in 1831?
He began a 5-year voyage around the world on a
Navy survey vessel, the HMS Beagle.
What did Charles Darwin discover during his five-year journey?
The finches beaks were all different from each other and had different functions
What are the three thories Darwin made up?
- Species change over time due to environmental changes
- Divergent species share a common ancestor
- The mechanism that produces change in natural selection (testable)
What is the essence of Darwin’s natural selection theory?
- Heritability (it has to be passed on)
- Variation is needed to evolve
- competition for survival of species
Why is natural selection so important?
It is the first evolutionary theory that could be tested
What does the evolutionary term “Fitness” refer to?
It refers to the individual’s ability to leave an offspring and allows the individual to survive and reproduce
What is evolutionary fitness?
It is the number of offspring plus the number of future descendants
Indirect fitness/inclusive fitness
An indirect way for an organism to pass on their genes from a sibling who has an offspring
What is adaptation in terms of evolution?
The adjustment or changes in behavior, physiology, and structure of an organism to become more suited to an environment.
What are the two simple rules of Natural Selection?
- Evolution doesn’t have to be elegant, it just has to work
2. evolved organisms can have defects as long as they can still survive and reproduce
What is modern synthesis?
describes the fusion (merger) of Mendelian genetics with Darwinian evolution that resulted in a unified theory of evolution
Population
a group of individuals of a single species that live and interbreed in a particular geographic area at the same ti time
Mutations
- Occur randomly
2. Can be deleterious, beneficial, or neutral (have no effect)
Deleterious
Something that can kill
Recombination
is a process by which pieces of DNA are broken and recombined to produce new combinations of alleles
Gene Flow
Migration or mating of individuals between populations that introduces variation
Genetic Drift
is a mechanism of evolution in which allele frequencies of a population change over generations due to chance (sampling error). It is faster in smaller population
Population Bottlenecks
occur when a random disaster occurs and a few individuals survives (passes through a narrow neck of a bottle)
Founder effect
Occurs when new individuals that find a new place to live and colonize (special bottleneck)
Allele Frequencies
refers to how common an allele is in a population. It is determined by counting how many times the allele appears in the population then dividing by the total number of copies of the gene.
Gene Pool of a Population
consists of all the copies of all the genes in that population
Genotype Frequencies
shows how a population’s genetic variation is distributed among its members
Biological evolution
Refers to changes in the genetic makeup of populations over time
Sexual Selection
Occurs when individuals of one sex mate preferentially with a particular individual of the opposite sex
Hardy-Weinberg Equilibrium
allele frequency = the number of copies of the allele in the population divided by the total number of copies of all alleles in the population
What are to conditions that must be met for a population to be at Hardy-Weinberg Equilibrium?
- There is no mutation
- There is no selection among genotypes
- There is no gene flow
- Population size is infinite
- Mating is random
Qualitative traits
influenced by alleles at one locus; often discrete qualities (black vs white, smooth vs wrinkled).
Quantitative traits
influenced by alleles at more than one
locus; likely to show continuous variation (body size)
Stabilizing selection
Acts to reduce variation without changing the mean value of a trait (birth weight)
Directional selection
Acts to shift the mean value of a trait toward one extreme ( Texas Longhorn cattle)
Disruptive selection
favors both extremes of trait values, resulting in a bimodal character distribution ( bill size in the black-bellied seedcracker of West Africa.)
The Paradox of Sex
Sexual reproduction results in new combinations of genes and produces a genetic variety that increases evolutionary potential.
Purifying Selection
Selection against any deleterious mutations to the usual gene sequence
What are the disadvantages of the paradox of sex?
- Recombination can break up adaptive combinations of
genes
2.Reduces the rate at which females pass genes to offspring - Dividing offspring into genders reduces the overall
reproductive rate
Muller’s ratchet
In the absence of genetic recombination, deleterious mutations accumulate with each replication
Sexual recombination does not directly influence the
frequencies of alleles. Rather, what does it do?
it generates new combinations of alleles on which natural selection can act.
Synonymous substitution
don’t affect phenotype because most amino acids are specified by more than one codon
Nonsynonymous substitution
changes the result of amino acids and can be deleterious, selectively neutral, or (more rarely) advantageous
pseudogenes
copies of genes that are no longer functional
Lateral Gene Transfer
individual genes, organelles, or genome fragments move horizontally from one lineage to another. this can be advantageous to species
