AP Biology Chapter 24 Notes

AP Biology Chapter 24 Notes The Origin of Species

What you need to know…  The difference between ______and ______.  The biological concept of ______.  ______and ______barriers that maintain reproductive isolation in natural populations.  How ______and sympatric ______are similar and different.  How an ______or an ______chromsomal change can lead to sympatric speciation.  How ______equilibrium and ______describe 2 different tempos of speciation.

______- the origin of new species, is at the focal point of evolutionary theory ______evolution consists of adaptations that evolve within a population, confined to one gene pool ______evolution refers to evolutionary change above the species level

Concept 24.1: The biological species concept emphasizes reproductive isolation  ______species concept - states that a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring; they do not breed successfully with other populations o Gene flow between populations holds the phenotype of a population together  ______isolation is the existence of biological factors (barriers) that impede two species from producing viable, fertile offspring o ______are the offspring of crosses between different species (Ex. Mule)  Label the Pictures  

 ______barriers block fertilization from occurring by: o Impeding different species from attempting to ______o Preventing the successful ______of mating o Hindering ______if mating is successful o Include: . Habitat isolation (next slide) -Two species encounter each other ______, or not at all, because they occupy different habitats, even though not isolated by physical barriers . behavioral isolation (next slides) -Courtship rituals and other behaviors ______to a species are effective barriers . temporal isolation (next slides) -Species that breed at different ______of the day, different seasons, or different years cannot mix their gametes . mechanical isolation (next slides) -Morphological differences can prevent successful ______. gametic isolation (next slides) - Sperm of one species may not be able to fertilize eggs of another species

 ______barriers prevent the hybrid zygote from developing into a viable, fertile adult: o ______hybrid viability (next slides) - Genes of the different parent species may interact and ______the hybrid’s development o Reduced ______fertility (next slides) - Even if ______are vigorous, they may be ______o Hybrid ______- (next slides) - Some first-generation hybrids are ______, but when they mate with another species or with either parent species, offspring of the next generation are feeble or sterile

 The biological species concept cannot be applied to fossils or asexual organisms (including all prokaryotes) o The ______species concept defines a species by structural features . It applies to sexual and asexual species but relies on subjective criteria o The ______species concept views a species in terms of its ecological niche . It applies to sexual and asexual species and emphasizes the role of disruptive selection o The ______species concept: defines a species as the smallest group of individuals on a phylogenetic tree . It applies to sexual and asexual species, but it can be difficult to determine the degree of difference required for separate species

Concept 24.2: Speciation can take place with or without geographic separation  Speciation can occur in two ways: o Allopatric speciation (next slides) - gene flow is ______or ______when a population is ______into geographically isolated subpopulations o Sympatric speciation (next slides) - speciation takes place in geographically ______populations  ______is the presence of ______sets of chromosomes due to accidents during cell division  An ______is an individual with more than ______chromosome sets, derived from one species  An ______is a species with ______sets of chromosomes derived from different species

Concept 24.3: Hybrid zones provide opportunities to study factors that cause reproductive isolation  A ______zone is a region in which members of different species mate and produce hybrids o A hybrid zone can occur in a ______band where adjacent species meet o Hybrids often have ______fitness compared with parent species o The distribution of hybrid zones can be more complex if parent species are found in multiple habitats within the same region o When closely related species meet in a hybrid zone, there are three possible outcomes: . ______of reproductive barriers . ______of reproductive barriers . ______formation of hybrid individuals

Concept 24.4: Speciation can occur rapidly or slowly and can result from changes in few or many genes  ______equilibrium to describe periods of apparent stasis punctuated by sudden change  Gradualism - gradual ______in a species’ existence  Label the picture 

You should now be able to… 1. Define and discuss the limitations of the ______species concepts 2. Describe and provide examples of ______and ______reproductive barriers 3. Distinguish between and provide examples of ______and ______speciation 4. Explain how ______can cause reproductive isolation 5. Define the term ______and describe three outcomes for hybrid zones over time