22.1 The Rise of Evolutionary Thought

• Lamarck proposed the first formal theory of evolution that species are not static but change through time.

• Darwin claimed that instead of being unimportant, variation among individuals in a population was the key to understanding the nature of species which is viewed as population thinking.

22.2 The Pattern of Evolution: Have Species Changed, and Are They Related?

• Descent with modification is the pattern component of the theory of evolution by natural selection makes two predictions about the nature of species:

  • Species change through time

  • Species are related by common ancestry.

• A fossil is any trace of an organism that lived in the past.

• The fossil record consists of all the fossils that have been found on Earth and described in the scientific literature.

• Extant species refers to species that are living today.

• Sedimentary rocks form from sand or mud or other materials deposited in layers at locations such as beaches or river mouths.

• Geologic time scale is a sequence of named intervals called eons, eras, and periods that represented the major events in Earth history

• Extinct species are species that no longer exist.

• A transitional feature is a trait in a fossil species that is intermediate between those of ancestral (older) and derived (younger) species.

• A vestigial trait is a reduced or incompletely developed structure that has no function, or reduced function, but is clearly similar to functioning organs or structures in ancestral or closely related species.

• Evidence from the fossil record and living species indicates that life is ancient and that species have changed through the course of Earth’s history.

• Phylogenetic tree is a branching diagram that depicts the ancestor-descendant relationships among species or other taxa

• Homology is a similarity that exists in species due to common ancestry.

• Homology can be recognized and studied at three levels:

  • Genetic homology is similarity that occurs in DNA nucleotide sequences, RNA nucleotide sequences, or amino acid sequences.

  • Developmental homology is similarity in developmental structures or processes.

  • Structural homology is a similarity in adult morphology, or form.

22.3 The Process of Evolution: How Does Natural Selection Work?

• He chose certain individuals with desirable traits to reproduce, thus manipulating the composition of the population by a process called artificial selection.

• Darwin distilled the process of evolution by natural selection into four simple postulates ( criteria) that form a logical sequence:

  • Viαriαtion exists among individual orgαnisms that mαke up a populαtion.

  • Some of the trait differences are heritable.

  • Survivαl αnd reproductive success re highly vαriαble

  • The subset of individuαls thαt survive best αnd produce the most offspring is not a random sαmple of the population.

• Natural selection occurs when individuals with certain heritable traits produce more surviving offspring than do individuals without those traits

• Evolution by natural selection occurs when

  • heritable variation leads to

  • differential reproductive success.

• Biological fitness is the ability of an individual to produce surviving, fertile offspring relative to that ability in other individuals in the population.

• An adaptation is a heritable trait that increases the fitness of an individual in a particular environment relative to individuals lacking the trait.

• Adaptations increase fitness-the ability to produce viable, fertile offspring.

22.4 Evolution in Action: Measuring Natural Selection in Populations Today

• Instead of comparing groups created by direct manipulation under controlled conditions, natural experiments allow researchers to compare treatment groups created by an unplanned change in conditions.

22.5 Debunking Common Misconceptions about Natural Selection and Evolution

• Lamarck proposed that

  • individuals change in response to challenges posed by the environment

  • the changed traits are then passed onto offspring

• The key claim is that the important evolutionary changes occur in individuals.

• Acclimatization is a change in an individual’ s phenotype that occurs in response to a change in natural environmental conditions.

• A fitness trade-off ( or simply trade-off) is a compromise between two traits that cannot be optimized simultaneously.

• Genetic correlation is when selection on one trait causes a change in another trait