Speciation Catalyst Drill Examine the picture below Would

Speciation

Catalyst Drill: Examine the picture below. Would you say that these organisms belong to the same species of not? Explain your answer.

Objective: Students will be able to understand the concept of speciation by taking notes and analyzing real-world scenarios. 1. What is the definition of a “species”? 2. What causes speciation?

Speciation • Disruption of Genetic Equilibrium • Formation of Species

What causes Speciation? • Disruption of genetic equilibrium leads to changes in the gene pool of a population. • Natural selection causes the most significant genetic changes in a population, however, such changes do not necessarily lead to speciation.

How do species come about? • Speciation( formation of new species) results in many related populations of organisms.

Morphological Species Concept • Morphological Species Concept: the idea that organisms can be classified by differences in their appearance • Using this concept, scientists can readily communicate about the characteristics, behavior, and relationships of organisms. • The morphological concept of species is limited because it does not account for the reproductive compatibility of morphologically different organisms.

Biological Species Concept • Biological Species Concept: the idea that organisms can be classified by their ability to breed with one another • Using both the biological and morphological concepts of species, modern scientists have arrived at the current definition of the term species.

Biological Species Concept • It defines species in terms of interbreeding • Limitation: Can not be used for extinct species whose compatibility can not be tested. *Species- morphologically similar species that can interbreed to produce fully fertile offspring.

• Species: a group of individuals that look similar and whose members are capable of producing fertile offspring in the natural environment

How do species give rise to other different species?

Isolated Populations • For a new species to arise, interbreeding of the population of fertile offspring must somehow cease among members of a formerly successful breeding population. • For this to occur, populations or segments of populations must somehow become isolated. • Two Forms of Isolation: • Geographic Isolation • Reproductive Isolation

Geographic Isolation • A geographically isolated subpopulation would become genetically very different ( due to mutation, maintaining gene pool, hindering gene flow, other environmental pressures) • As a result members may fail to successfully interbreed with members of related parental group. Thus long geographical isolation may lead to reproductive isolation.

Reproductive Isolation • Reproductive Isolation: the inability of formerly interbreeding organisms to produce offspring – Reproductive isolation can occur through disruptive selection. Two Types: a. Prezygotic- Differences in mating times; b. Postzygotic- death / sterility of offspring

Pre zygotic Isolation • Reduce the chance of hybrid formation ( no new alleles are formed) • Geographic isolation( diff. places) • Ecological isolation(utilize diff. resources) • Behavioral Isolation (diff. mating rituals) • Temporal Isolation(Mating at diff. seasons) • Mechanical isolation( structural differences) • Prevention of gamete fusion( gametes function poorly)

Post Zygotic Isolation • Developmental ( poor development of embryo) • Hybrid unviability (adults do not survive in nature • Hybrid sterility ( hybrids are sterile/reduced fertility)

Rates of Speciation • Punctuated Equilibrium: a theory that speciation may occur during brief periods of rapid genetic change • Gradualism: a theory that speciation may occur through a gradual change of adaptations

Prezygotic versus Postzygotic • 5 minutes to complete handout

Wolves of Yellowstone • Read questions now • Answer questions as you watch video