1. Biodiversity Studied in a relatively new field called Conservation Biology Consists of three components: 1.Species 2.Genes 3.Ecosystems

2. The Biological Species Concept The biological species concept defines a species as –A population or group of populations whose members can interbreed and produce fertile offspring

3. Other Species Concepts The _____concept –Classifies organisms based on observable phenotypic traits The _____concept –Defines a species by its ecological role The phylogenetic species concept –Defines a species as a set of organisms representing a specific evolutionary lineage

4. Speciation requires: 1.Genetic variation 2.Natural Selection 3.Reproductive Barriers

5. Mutation, sexual recombination, gene flow, and genetic drift can generate variation needed for speciation Mutations, or changes in the nucleotide sequence of DNA –Can create new alleles

6. Sexual recombination –Generates variation by shuffling alleles during meiosis (independent assortment), and cross overs A1A1 A2A2 A1A1 A3A3 A1A1 A1A1 A2A2 A3A3 A2A2 A1A1 A3A3 and X Parents Meiosis Gametes Fertilization Offspring, with new combinations of alleles Figure 13.12 Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

7. Gene flow –Is the movement of individuals or gametes between populations. Occurs in plants by ____ and _____ –Can alter allele frequencies in a population Genetic drift –Is a change in the gene pool of a population due to chance –Can alter allele frequencies in a population

8. Natural selection – Leads to differential reproductive success in a population – Can alter allele frequencies in a population

9. Natural selection can alter variation in a population in three ways Stabilizing selection – Favors intermediate phenotypes Directional selection – Acts on individuals at one of the phenotypic extremes Disruptive selection – Favors individuals at extremes of the phenotypic range

10. Three possible effects of natural selection Original population Stabilizing selection Original population Evolved population Frequency of individuals Phenotypes (fur color) Directional selection Disruptive selection Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

11. Reproductive barriers keep species separate Reproductive barriers –Serve to isolate a species’ gene pool and prevent interbreeding –Are categorized as prezygotic or postzygotic

12. Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

13. Prezygotic Barriers Prezygotic barriers –Prevent mating or fertilization between species

14. Seasonal Flowering Differences - In temporal isolation - Three orchid species of the genus Dendrobium live in the same tropical rain forest and all flower after thunderstorms. One flowers eight days after the storm, a second species nine days after, and a third species ten days after the storm

15. In behavioral isolation –There is little or no sexual attraction between species, due to specific behaviors Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

16. In mechanical isolation –Female and male sex organs or gametes are not compatible Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

17. Morphological differences in flowers allow them to be specifically adapted to certain pollinators. Pollen is transferred only between plants of the same species with the same floral anatomy. Length of the stigma and style and growth of the pollen tube Is often important in mechanical isolation of plants. In mechanical isolation of plants:

18. In microhabitat differences – Two species occupy different microhabitats Ex. Quercus coccinea (scarlet oak) and Q. velutina (black oak) of eastern USA are isolated in different microhabitats. Scarlet oak grows in wet habitats adjacent to black oak in dry upland habitats

19. In gametic isolation – Two species can chemically distinguish between pollen of the same species and that of different species. Germination of pollen from foreign species is retarded by chemical components in the stigma and style

20. Postzygotic Barriers Postzygotic barriers –Operate after hybrid zygotes are formed

21. One postzygotic barrier is hybrid sterility –Where hybrid offspring between two species are sterile and therefore cannot mate Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

22. Geographic isolation on east and west slopes of the Rockies, eastern and western Great lakes, and on the eastern and western slopes of the Appalachians has resulted in new species of organisms. Isolated ponds in deserts has led to new species of pupfish and plants Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings In allopatric speciation a population is geographically divided.

23. New species can also arise within the same geographic area as the parent species In sympatric speciation –New species may arise without geographic isolation –Microhabitat isolation as in red (moist) and black (dry) oaks –Gametic isolation where species can chemically distinguish their own pollen and destroy that of other species

24. Many plant species have evolved sympatrically by polyploidy (DE VRIES and BOEDIJN 1923) –Multiplication of the chromosome number due to errors in cell division Parent species Meiotic error Self- fertilization Offspring may be viable and self-fertile Zygote Unreduced diploid gametes 2n = 6 Diploid 4n = 12 Tetraploid O. gigas Oenothera lamarckiana Copyright © 2005 Pearson Education, Inc. Publishing as Benjamin Cummings

25. AABB AB AA BB DD ABD AA BB DD   Triticum monococcum (14 chromosomes) Wild Triticum (14 chromosomes) Sterile hybrid (14 chromosomes) Meiotic error and self-fertilization T.turgidum Emmer wheat (28 chromosomes) T.tauschii (wild) (14 chromosomes) Sterile hybrid (21 chromosomes) Meiotic error and self-fertilization T.aestivum Bread wheat (42 chromosomes) Polyploid plants clothe and feed us Many plants, including food plants such as bread wheat –Are the result of hybridization and polyploidy

26. Polyploidy is a common mechanism for sympatric speciation: Hybrid polyploids (allopolyploids) have characteristics of both parents. They have more genes and enzymes to deal with changes in the environment and thus are often better adapted than the parent species. Since their chromosome numbers are doubled chromosomes can no longer pair with parent chromosomes during meiosis and thus are reproductively isolated from their parents. Many plant species have been shown to undergo this type of rapid sympatric speciation. Invertebrates and lower chordates also often speciate in this manner.

27. Adaptive radiation can also be rapid and may occur in new or newly vacated habitats In adaptive radiation, the new species –Occur when mass extinctions or colonization provide organisms with new environments –Ex. Over the course of millions of years, the descendants of the pioneer plant in the Hawaiian silversword `ohana (family) evolved into 28 distinct species in three genera, occupying many different habitats.

28. Flowering rosette of the extremely rare Mauna Kea silversword (Argyroxiphium sandwicense subsp. sandwicense) Copyright © The Botanical Society of America