Ch. 5 Adaptations and Natural Selection Flashcards
The structure of an organism ultimately affects ______ (and therefore fitness)
survival
When relating to structure and function, a change in one results in
change in other
Prior to the mid 19th century, the apparent match between organism and environment was seen as the work of
a creator
Natural history was thought of as cataloging the creations of a divine architect. This was reflected in the _____ ______
Scala Naturae
Scala Naturae
- the great chain of being
- a concept derived from Aristotle’s proposed tree of life
- life had a hierarchical order with lesser organisms at the bottom and man sitting atop the list
Who brought the most widely accepted view of the natural world into question with one basic idea: couldn’t there have been enough time for generations and generations to differ in their success?
Charles Darwin
Where did Darwin first get his idea for the Origin of Species?
voyage of the HMS Beagle (1831)
-22 years old
In the Origin of Species, Darwin includes one figure which depicts what?
- shows evolution
- phylogenetic relatedness
- extinction
- speciation
Biological evolution
genetic change over time (generations)
Natural selection
the differential success of individuals within a population that results from interactions with their environment
What are the 4 Tenants of Natural Selection?
- more offspring are produced than survive (competition)
- Organisms produce offspring with different traits (variability)
- traits are genetic (inherited)
- Offspring experience differences in survival (and reproduction): (adaptation)
Why is natural selection not about:
- survival of the fittest
- longest-lived
- fastest
- most intelligent
- prettiest
none of these matter unless they improve an individual’s ability to pass their genes on to the next generation
Evolutionary Stable Strategies
a strategy that once adopted by a population, cannot be invaded by an alternative strategy
Why are most strategies not evolutionarily stable?
something else wins eventually
_______ are a product of natural selection
adaptations
adaptation
any heritable behavioral, morphological, or physiological trait of an organism that maintains or increases fitness of an organism in a given environment
Fitness
long-term reproductive success; relative reproductive success of one individual compared to members of the same species in a particular environment
______ are the units of inheritance
genes
Genes
what pass adaptations to offspring; stretches of DNA that code for a functional product
Alleles
variations in genes; alternative forms of the same gene
Ultimately, the genotype produces the ______
phenotype
Natural selection can achieve similar results from completely different __________
sources of material (genes)
The _______ is the physical expression of the genotype
phenotype
Qualitative traits
discrete, categorical traits (presence/absence)
Quantitative traits
measurable traits (ex. height, weight, etc.)
Heritability
a statistic used that estimates how much variation in a phenotypic trait is due to genetics and not environment
The expression of most phenotypic traits is affected by the _______.
environment
Phenotypic plasticity
the ability of a genotype to give rise to different phenotypic expressions under different environmental conditions
Reaction norm
the set of phenotypes expressed by a single genotype across a range of environmental conditions
Acclimation
organisms respond to brief changes in environmental conditions
Genetic variation occurs at the level of the ________.
population
Genetic differentiation
occurs when there is genetic variation among subpopulations
Gene pool
the sum of the genetic variation across all individuals of a population
Evolution
change in gene frequency over time
Phenotypic evolution
change in the average phenotypic trait over time
Natural selection is a product of what two conditions?
- heritable variatioin
- variation results in differential survival and reproduction
Target of selection
the phenotypic trait that selection acts directly upon
Selective agent
the environmental cause of the fitness difference among organisms with different phenotypes
What are the three different types of natural selection?
- directional
- disruptive
- stabilizing
Directional selection
when natural selection shifts the average phenotype away from the previous average
Stabilizing selection
occurs when there is selection against the extreme phenotypes
Disruptive selection
occurs when there is selection against an intermediate phenotype
Mutation
random and unpredictable change in a gene
What is the ultimate driver of evolution?
mutations
Genetic Drift
change in allele frequency due to random chance
Migration
movement of individuals into or out of a local population
Gene flow
movement of genes between populations
Five processes that can drive evolution
- natural selection
- mutation
- genetic drift
- migration
- non-random mating
Clines
measurable, gradual change in a population along an environmental gradient
Clines can produce complicated species interactions. An example is
ring species; a connected series of neighboring populations which can interbreed, but the two “end” populations cannot
Adaptations reflect _____ and ______.
trade-offs; constraints
Constraints
limitations imposed on an organism due to their adaptations to their local environment
Trade-offs
an increased ability in one task often results in a decreased ability in another
