BIO 113 Exam 1 Ch. 25

evolutionary changes that produce new species and new groups of species

1. biological species concept 2. morphological species concept 3. recognition species concept 4. cohesion (pluralistic) species concept 5. ecological species concept 6. evolutionary species concept

-based on reproductive isolation -populations of a species can interbreed or are interbreeding -members of a species are reproductively isolated from other species -this concept holds up well for animals, not so well for plants or bacteria

-based on anatomical differences between species -similar to phylogenetic species concept -similar to paleontological species concept utilized to identify fossil species

descended from common ancestor; all members possess combination of certain defining traits

definition of species based on morphological differences known only from the fossil record

distinct mating adaptations by species (molecular, form, behavior) -example: male peacock's tale

-emphasizes factors that maintain the distinct form and behavior of a species -factors include such things as reproductive barriers

species are identified by where they live and how they behave, not what they look like

-emphasizes the evolutionary history of a species and the species' unique role in the environment -similar to the evolutionary lineage concept

species are derived from a single distinct lineage and have their own evolutionary tendencies and historical fate

also known as reproductive isolation mechanisms 1. prezygotic barriers 2. postzygotic barriers

impede reproduction and fertilization of the ova between species -5 barriers

1. habitat isolation 2. behavioral isolation 3. temporal isolation 4. mechanical isolation 5. gametic isolation

prevent the development of a viable, fertile offspring -3 barriers

1. reduced hybrid viability (inviability) 2. reduced hybrid fertility (sterility) 3. hybrid breakdown

-occurs when a population becomes isolated from other populations and evolves into one or more species -involves geographical isolation

can be almost anything lakes, oceans, rivers, mountain ranges, deserts, etc.

species arranged in a ring around a geographical barrier (allopatric speciation in progress)

-the environment is different for the isolated populations -if an isolated population comes from a peripheral area -if the isolated population is small

a single ancestral species has evolved into a wide array of descendant species that differ in their habitat, form, or behavior

-occurs when members of a species that are within the same range diverge into two or more different species even though there are no physical barriers to interbreeding -in this form of speciation, the populations are not geographically divergent but become genetically divergent -polyploidy

an organism has more than two sets of chromosomes -new plant species can arise through this

polyploidy in an individual

formation of polyploidy offspring from two different species

each new species continuously evolves over long spans of time -the idea is that the large phenotypic differences that produce new species are due to the gradual accumulation of many small genetic changes

-the tempo of evolution is more sporadic -species exist relatively unchanged for many generations. during this equilibrium period, genetic changes are likely to accumulate (neutral changes), however, genetic changes that significantly alter phenotype do not substantially change the overall composition of a population

structures that have evolved under one context can later take on other functions. example: stress sensors have evolved into hearing organs in some insects