Biology 112 Exam 2

Lamarck was the first naturalist to propose a theory that species “evolved” over time - His hypothesis was that species evolve through use and disuse and the inheritance of acquired traits - The mechanisms he proposed were incorrect (?) but his insight was revolutionary

Wallace was a naturalist working principally in Indonesia who independently from Darwin developed a theory of evolution based on natural selection almost identical to that which Darwin was writing - In June 1858, Darwin received a manuscript from Wallace discussing this idea. This was the push for Darwin to finish his “Origin”

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 Current species are descendants of ancestral species – Descent with Modification

 Natural selection is a mechanism for this evolutionary process

Darwin’s theory lacked a satisfactory theory of heredity

While Darwin proposed that traits must be inherited from generation to generation he did not know what could control this Mendel’s work was at the time obscure The unification of Mendel’s theory of heredity and Darwinian evolution between 1920-1940 led to our modern theory of evolution

the change in allele frequencies in a population over time

Individuals whose inherited traits give them a higher probability of surviving and reproducing in a given environment tend to leave more offspring than other individuals.

Requirement 1: Differential success in reproduction

Requirement 2: Variation among individuals in a population must be heritable

Requirement 3: Selected phenotypes result in organisms that are better adapted to their environment

It is not searching for perfection but searching to survive and the organisms with the best traits do so.

Direct observations of evolutionary change, The fossil record, Homologies, Biogeography, and Molecular Biology

Microevolution-The Change at the population level. Also the change in the allele frequencies in a population over generations.

Macroevolution-An Evolutionary change above the species level. Such as change include the origin of a new group of organisms through a series of speciation events and the impact of mass extinctions on the diversity of life and its subsequent recovery

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Notes

Directional-Occurs when conditions favor individuals. Example the 3 darker mice examples survived better than the brighter two. Common when a pop environment changes or when members of a pop migrate to a new habitat.

Stabilizing-Intermediate (middle) phenotypes survive or reproduce more successfully than do extreme phenotypes. Such as the middle shade of fur mouse.

Diversifying-Individuals on both extremes of a phenotypic range survive or reproduce more successfully than do individuals with intermediate phenotypes. Brightest and Darkest mouse both survive better.

Gene Flow-The transfer of alleles from one population to another.

Genetic Drift-Process in which chance events cause unpredictable fluctuations in allele frequencies from one generation to the next.

It is more significant in small population sizes.

Bottleneck Effect-Most of individuals die/are destroyed somehow (disease, cataclysmic event…)

Founder Effect-A small group of individuals gets separated from the rest – e.g. birds blown off course during migration.

Because there could be so much diversity within the species and there are different concepts of what a species is.

Biological-The key is Reproductive Isolation- different species cannot interbreed and produce fertile or viable offspring.

Morphological-Characterizes a species in terms of its body shape, size, and other structural features

Pylogentic-Defines a species as a set of organisms with a unique genetic history based on molecular/DNA structure

Ecological-An ecological species considers the interaction of the organism with its entire environment It inhabits only a specific niche or adaptive environment and this influences the phenotype

 Prezygotic barriers  Block Fertilization from occurring.

 Postzygotic barriers  Often prevent the hybrid zygote from developing into a viable, fertile adult

Allopatric-The formation of new species in populations that are geographically isolated from one another.

Sympatric-The formation of new species in populations that live in the same geographic area.

Polyploidy-An organism possesses more than two complete chromosome sets. It is the result of an accident of cell division. More common in plants.

 Adaptive radiation is the evolution of diversely adapted species from a common ancestor upon introduction to new environmental opportunities  This group evolved from a single introduction from western North America  Adaptation to different ecological habitats in the islands has resulted in an incredible diversity of isolated forms.