Chapter 17 - Origin of Species

Example of Sympatric speciation

Cichlid fish in rift lakes of east Africa hundreds of species conditions for this in ecologically and behaviorally diverse group. phenotypic plasticity, aggressive behavior, territoriality, consume specialized diets available in microhabitats.

Adaptive radiation

Evolution of many species from a single species in a relatively short period of time Evolution of many new species from a common ancestor as a result of introduction to new environments.

Sexually

In ______ reproducing species the process of speciation is always the result of genetic isolation developing between populations formerly connected by gene flow

Types of adaptation to local environment that don't affect reproductive biology

Morphology (anatomy) physiology behavor

allopatric

Primary means of speciation. species or population is geographically separated.

____ may prevent fertilization from taking place

RMIs - Reproductive isolating mechanisms

Breeding seasons different is an example of

Reproductive isolating mechanism

Differences in habitat choices. Habitat requrements of different species may prevent them from crossing paths. This is example of

Reproductive isolating mechanism

Gene Flow

The migration of genes into a population from other populations by interbreeding Movement and interbreeding of individuals from different geographic populations Habitat is divided into chuncks separated by area of less suitable or unsuitable habitat

True

True or False No specific number of years or generations that are necessary for speciation to occur Can be quick (Few generations) or long process (thousands or millions of years)

To remain part of the same species in the long term, its sub-populations must be linked by ______ _____. It may be slow encouraging adaptation of local populations to their local environment.

gene flow

The _____ the gene flow, the _____ the differences develop over time and the more ______ the species is.

greater fewer Stable

The consequence of episodic hybridization is to _____ genetic variation on which selection can later act. Example: Homo sapieans and neaderthals interbred and our ancestors picked up beneficial alleles, new variation with other populations of humans

increase

Allopatric/Peripatric/Parapatric speciation

involve geographic isolation to varied degrees

Sexual isolation of related species should be ______ when different species are sympatric or overlapping geographicall

strongest

Mechanisms facilitating reproductive isolation - isolation can be caused by a combination or just one.

1) Different seasonal breeding season 2) Dietary differences 3) Habitat differences or preferences 4) Behavioral differences in mating and foraging for food

Speciation initiated by geographical isolation occurs in three steps

1) Geographical isolation 2) local adaption 3) reproductive isolation

2 modes of speciation differentiated by whether geographical isolation occurs

1) allopatric 2) Sympatric

3 most common reproductive isolating mechanisms

1) death of gametes, zygote or early embryo 2) formation of a hybrid with low viability 3) Hybrid sterility or inferiority

If hybridization bad, why does it appear in nature

1) species ranges overlap vary little (allopatric), weaker isolating mechanisms. Benefit to have traits that make them less likely to interbreed is small and doesn't spread through population via natural selection Example: Carolina and Black capped chickadees in north america. 2) accidently happens in species that breed in water and release eggs and sperm there.(fish and amphibians) 3) when 2 related species overlap geographically only interbreed out of deseration. Cant find viable mate, too young or low ranking.

Mechanisms that prevent interbreeding between different populations

1) timing of breeding during the year 2) activity patterns during the day 3) behavioral 4) habitat preference 5) Changes in reproductive biology 6) fertilization or embryonic development

founder effect

A decrease in genetic variation caused by the formation of a new population by a small number of individuals from a larger population.

Reproductive Isolating Mechanisms (RIMs)

Any structure or function that is genetically determined and prevents interbreeding between organisms. May occur before fertilization (pre-zygotic) or after fertilization (post sygotic) Can be simple or complex differences i.e. simple (coloration or mating behavior prevents or makes unlikely two species will recognize each other) or i.e. complex (phycially impossible because of morphological changes)

Galapagos finches found by Darwin

Example of adaptive radiation

True

Much of evolution is about populations maintaining characteristics the enabled them to separate in the first place. True or False

Allopatric speciation process

a) split into 1 or more new geographical areas b) allow genetic differentiation to occur c) groups can come back into contact d) result in selection for increased reproductive isolation between them e) speciation is complete when gene flow between group can no longer occur even when two new species occcupy same locality.

sympatric speciation process

a) when species splits into one or more groups that occupy different ecological zones (niches) such as special habitats, region or different food sources in locality. b) increased genetic differentiation between groups c) permits selection for reproductive isolation mechanisms d) eventually lead to complete speciation e) result in new species species in each late are more closely related to each other than they are with the species they are most closely resemble in other lake.

Mechanisms that reduce gene flow (gene exchange) between populations _____ the formation of distinctive groups

accelerate

process of _______ speciation begins with formation of distinct seperate populations

allopatric

Species where colonizer are capable of transcending geogrphical barriers and moving into new environments often become ______ of entirely new groups

ancestors

Hybridization is bad because

dead end for parents waste of time and energy little or no evolutionary fitness for them offspring unlikely or may be: - sterile or reduced fertility - odd appearance - odd behavior - mistiming of mating behaviors Example: Liger hybrid male lion and female tiger (only in captivity) due to different habitat preferences and social organization. However, may encounter each other in India.

ecotypes, varieties, races, subspecies or separate sibling species

distinct groups within species that still interbreed and produce viable offspring are called

gene flow

glue that keeps populations part of the same species, done by homogenizing them genetically Movement between populations spreads mutations around keeping them similar enough to meet definition of species

Gene flow is ______ between populations of non-migratory birds than migratory species. Differences are ____ likely to build up between populations of migratory species and those are more likely to ____ into ____ species

greater more split distinct

Example of peripatric speciation

hawaiian island Fruit flies (drosophpilia)

small populations evolve ______ rapidly than larger ones

more

allopatric speciation

other place occurs due to geographic location that prevents gene flow between populations evolutionary change between populations initiated by geographical separation or because intervening geographical populations become extinct.

3 steps in the process of allopatric speciation - occurs when

population is divided due to a natural physical barrier or intervening geographical populations that connect populations on either side become extinct. Must be exposed to differential selection in new environment for speciation to be initiated and must adapt phenotypically in response. individuals in populations have built up enough differences they no longer meet definition of a species and can not produce fully viable offspring under natural conditions

Hybrid offspring

result of mating between members of related yet distant species

sympatric speciation.

same place occurs between populations occupying the same geographic range occurs within a population

sympatric speciation

selection for different habitats within locality could accumulate increased genetic variability through disruptive selection The formation of a new species as a result of a genetic change that produces a reproductive barrier between the changed population (mutants) and the parent population. No geographic barrier is present.

_____ traits undergo greater selection for differences between populations during speciation. Greater selection for uniformity within species after attaining speciation.

sexual

sympatric

species or populations whose geographical distributions coincide or overlap The formation of new species in populations that live in the same geographic area

If the pattern of disruptive selection and assortive mating for color form continues, ____ speciation seems inevitable

sympatric

Example of Allopatric speciation

tamarin monkeys sperated by opposite sides of amazon river Where wide - opposite banks do not interbreed, they diverge toward seperate species Where narrow - still interbreed and they do no diverge significantly

sympatric speciation occurs when

there are mechanisms that reduce gene flow within a population in absence of initiating geographic isolation of the populations occuring Controversial evidence it occurs if there is a disruptive selection on a trait and assortive mating based on that trait in a population with similar phenotypes prefer to breed with each other. occurs in hamlet fish each of 9 color mimics different fish species. Colors occured through disruptive selection on color patterns breed with same color morph more than other color morphs. color forms genetically different, but not so much they cannot breed and produce offspring.

Peripatric speciation

when population is divided because of budding off of a small completely isolated founder colony from larger population founder effect results in decrease in genetic diversity in new population compared to original one. Small founding group of colonizers cannot bring all of the alleles from original population small isolated population will be subject to genetic drift, inbreeding, and may be exposed to new adaptive landscapes in their new habitat.

evolutionary successful hybridization took place in 2 different ________ ________ __________ species. Created asexual all female whip tailed lizard. very big fitness payofff for that one male and one female.

whip-tailed lizard