Special Creation
The idea that the world came to be through a higher being. Includes the ideas that species are independent and immutable and that life on Earth is only around 6,000 years old.
Pattern Component
The first component of a scientific theory. This component is a statement about facts and how things are.
Process Component
The second component of a scientific theory. This component is the mechanism that produces a pattern.
Scientific Revolution
Replaces an existing idea about nature with a radically different idea; often considered "revolutionary
Plato
Claimed that every organism was an example of a "perfect essence" created by god and that these types were unchanging.
Typological Thinking
An idea that proposes that species are unchanging and that variations among these species are unimportant/misleading
Aristotle
Ordered organisms into the linear "great chain of being." His ideas were still popular in the 1700s.
Great Chain of Being
Aristotle's typological model that organized species into a fixed, linear sequence based on increasing size and complexity. Humans were at the top of this chain.
Central claims: species are fixed types and some species are better/more complex than others.
Jean-Baptiste Lamarck
First to propose a formal theory of evolution:
1. Simple organisms originate at the base of the "Great Chain of Being" by spontaneous generation.
2. Organisms evolve by moving up the chain over time.
3. Evolution is progressive, or always producing "bette
Inheritance of Acquired Characters
A Lamarckian idea that an individual's phenotype changes in response to environmental challenges AND is then passed onto offspring.
Darwin and Wallace
Proposed that change in species through time 1. does not follow a linear, progressive pattern and 2. is based on variation among individuals in populations.
Population
Consists of the total number of individuals of the same species living in the same area at the same time.
Population Thinking
Not typological. The idea that variation among individuals is the key to understanding evolution.
Descent with Modification
PATTERN OF EVOLUTION.
The idea that change over time produced modern, modified species from ancestral species.
1. Species change through time
2. Species are related through common ancestry
Fossils
Traces of organisms that lived in the past
Sedimentary Rocks
Form in layers from sand or mud; younger layers are deposited on top.
Geologic Time Scale
A record that indicates the ages of fossils based on their relative positions in sedimentary rock.
Eons --> era --> period --> epoch
Radioactive Decay
Researchers assign absolute ages based on this: they steady rate of conversion of unstable "parent" atoms into stable "daughter" atoms
Radiometric Dating
Based on decay rates and the ratio of parent:daughter atoms is rock samples. Used to determine the absolute age of a fossil. Indicates that Earth is about 4.6 billion years old and life on Earth is about 3.4-3.8 billion years old.
Extinct
Species that no longer exist, which is evidence that 1. species are dynamic and 2. the array of species living on Earth has changed through time.
Law of Succession
Fossil species are strikingly similar to living species in the same geographic areas. Evidence that 1. species change through time and 2. extinct and extant organisms are related and represent ancestors and descendants.
Transitional Features
Traits in a fossil species that are intermediate between ancestral and derived species.
ie: gradual change from aquatic fin to terrestrial limb
Vestigial Trait
A reduced or incompletely developed structure in an organism that has no (or reduced) function. Clearly similar to functioning organs or structures in closely related species.
ie: reduced wings in flightless birds; coccyx bone and goose bumps in humans
1.
Phylogenic Tree
A diagram that illustrates the ancestor-descendant relationships among taxa. Shows common ancestry.
ie: Gal�pagos Island finches share one common ancestor.
Homology
A similarity that exists in species descended from a common ancestor.
Genetic Homology
A similarity in the DNA nucleotide sequences, RNA nucleotide sequences, or amino acid sequences.
ie: eyeless gene in flies/aniridia gene in humans = 90% identical
Developmental Homology
A similarity seen in embryos of different species.
ie: gill and tail pouches in embryos of chickens, humans, and cats
Structural Homology
A similarity seen in adult morphology.
ie: most vertebrates have a common bone structure plan in limbs.
Speciation
A process that results in one species splitting into two or more descendant species.
1. Powerful evidence that extant species are the descendants of extinct species.
2. Supports the claim that all organisms are related by descent from a common ancestor.
Evidence for Evolution
Species are not static, but change through time:
1. Life on Earth is ancient and most species have gone extinct.
2. Fossil species frequently resemble living species found in the same area.
3. Transitional features document change in traits through time.
Internal Consistency
The observation that data from independent sources agree in supporting predictions made by a theory. The most powerful evident for any scientific theory.
Artificial Selection
The breeding of plants and animals to produce desirable traits. Darwin used pigeons as an example of evolution by natural selection.
Thomas Robert Malthus
Wrote "An Essay on the Principle of Population." Described a "struggle for existence," ie: many more individuals are born than can survive.
Darwin's Four Postulates
Darwin's process of evolution by natural selection broken down into four criteria:
1. Individuals in a population vary in their traits.
2. Some of these differences are heritable and passed onto offspring.
3. In each generation, many more offspring are pr
Evolution
A change in the allele frequencies of a population over time.
Biological Fitness
The ability of an individual to produce surviving, fertile offspring relative to that ability in other individuals in the population.
Adaptation
A heritable trait that increases an individual's fitness in a particular environment relative to individuals lacking that trait. Occurs when the allele frequencies in population change in response to natural selection.
Selection
Differential reproduction as a result of heritable variation.
Natural Experiment
An experiment that allows researched to compare treatment groups created by an unplanned change in conditions (the conditions were not created artificially; ie: a drought).
Polygenic Trait
One whose phenotype is influenced by more than one gene
Take Home 1:
Evolutionary change occurs in populations, NOT individuals. Natural selection only sorts existing alleles in organisms, it doesn't change them.
Take Home 2:
Individuals with alleles that result in self-sacrificing behavior die and do not produce offspring, so these alleles are eliminated from the population.
Take Home 3:
Adaptations do NOT occur because organisms want or need them. There is also no such thing as a "higher" or "lower" being.
Take Home 4:
Evolution does NOT perfect organisms. Some traits are nonadaptive, some traits cannot be optimized due to fitness trade-offs, and some traits are limited by genetic constraints.
Acclimatization
Occurs when an individual's phenotype changes in response to changes in the environment. The individual's genotype remains fixed and the changes are not passed onto offspring because no alleles have changed.
Silent Mutations
Changes in the DNA sequences that do not result in a change in the amino acid sequence of the protein encoded by the gene. Extremely common. Do not change the phenotype and thus cannot be acted on by natural selection and are not adaptive.
Genetic Correlation
Occurs when selection favoring alleles for one trait causes a correlated but suboptimal change in an allele for another trait.
Pleiotropy
A single allele affects multiple traits
Fitness Trade-Off
A compromise between traits in terms of how those traits perform in the environment.
Because selection acts on many traits at once, every adaptation is a compromise.
ie: the size of eggs or seeds that an individual makes and the number of offspring it can