Ch.27

Fusion of populations example

occur whenever populations of the same species comes into contact

Temporal prezygotic isolation example

Bishop pines and Monterey pines release their pollen at different times of the year

Polyploid individuals are reproductively isolated from the original diploid population and thus evolutionary individuals because

Breeding between diploid and tetraploids generally result in sterile offspring

Reinforcement of divergence

If hybrid offspring have low fitness natural selection favors fitness natural selection of traits that prevent interbreeding between the population

Extinction of one population

If one population of species is a better competitor for shared resources then the porter competitor may be driven to extinction

Creation of a new species

If the combination of genes in hybrid offspring allows them to occupy distinct habitat or use novel resources, they may form a new species

postzygotic isolation

The offspring of mating between members of different species do not survive or reproduce

Extinction of one population example

Townsend warblers may be driving hermit warblers to extinction

Reinforcement of divergence example

Appears to be come in fruit fly species that occupy the some geographic area

Genetic isolation results from

Lack of gene flow and genetic

If one species (2n=10) crosses with another species (2n=18), producing an allopolyploid offspring, what is the ploidy of the offspring?

2n=18+10=28

The biological species concept can be applied only to which of the following groups? A. bird species living today B. dinosaurs and bird species living today C. dinosaurs D. bacteria

A.

What is true about speciation? A. It is the result of genotype frequencies diverging B. It is a result of isolation or increase gene flow C. it is the result of solely natural selection D. all of the above E. none of the above

A. (allele should be) B. (decrease gene flow) C. solely D. E. Correct

A. biological species concept B. morphospecies concept C. phylogenetic species concept 1. Homologous traits 2. Reproduction 3. Size and shape

A. 1 B. 3 C. 2

Even though symmetric population are not geographically isolated they may become reproductively isolated by

Adapting to different ecological niches via disruptive selection

Species

An evolutionary independent population or group of population

Subspecies

Are populations that live in discrete geographical areas and have distinguishing features

Which of the following describes vicariance? A. small population coalesce into one large population B. a population is fragmented into isolated populations C. individuals colonize a novel habitat D. individuals disperse and found a new population

B.

In the case of the seaside sparrow, how did the species identified by the biological species concept, the morphospecies concept and the phylogenetic species concept conflict?

Based on biological and morphospeices criteria (breeding range and morphological traits) are species with six subspecies of seaside sparrows were recognized. However, based on phylogenetic criteria (comparison of gene sequence) biologist concluded that seaside sparrows represent only two monophyletic groups.

Unlike animal gametes plant reproductive cells do not differentiate until late in life. Why are plants much more likely than animals to produce diploid gametes and polyploidy offspring?

Cells that differentiate later in life undergo many rounds of mitosis, so are more likely to accumulate mutations

Reproductive isolation concept is difficult to apply when

Closely related populations do not happen to overlap with each other geographically

monphyletic group

Consists of an ancestral population all of its descendants and only those descendants

What is true about speciation? A. species are identified using 3 criteria B. it is a splitting event that creates less than 2 groups from 1 C. the result is less than 1 evolutionary independent population D. all of the above are true E. none of the above are true

D

A large amount of gene flow is now occurring amount human populations due to intermarriage among people from different ethnic groups and religion of the world. Is this phenomenon increasing or decreasing racial differences in our species? Explain

Decreasing gene flow tens to equalize allele frequencies among populations.

Which studies in this chapter represent direct observation of speciation? Which are indirect studies of historical speciation events?

Direct observation- Galapagos finch colonization, apple maggot flies, maidenhair ferns Indirect observation- snapping shrimp, sunflowers

Geographic isolation happens in two ways

Dispersal viscariance

Hybrid sterility example

Easter meadowlarks and western meadowlark are almost identical morphologically but their hybrid offspring are usually infertile

Two events can initiate the process of sympatric speciation

External events (disruptive selection) for extreme phenotype based on different ecological niches. Internal events (chromosomes mutation)

Gene flow, genetic drift and natural selection all usually result in adaptive selection. True or False

False

True or False? Gene flow increase the divergence of populations?

False

Hybrid zone formation

Hybridization occurs in a well defined geographical area. This area may move overtime or be stable.

Criterion of reproductive isolation cannot be evaluated in

Fossils or in species that reproduce asexually

Possible outcomes of secondary contact between populations

Fusion of the populations Reinforcement of divergence Hybrid zone formation Extinction of one population Creation of new species

Speciation results from

Genetic isolation and genetic divergence

Geographic isolation of population via dispersal or vicariance produces

Genetic isolation due to the interruption of gene flow the 1st requirement for speciation

When the ranges of two different species meet, a stable hybrid zone occupied by hybrid individuals may form. How is this possible?

Hybrid individuals may have intermediate characteristics that are advantageous in a give region.

Hybrid viability

Hybrid offspring do NOT develop normally and die as embryos

Hybrid sterility

Hybrid offspring mature but are sterile as adults

postzygtic isolation types

Hybrid viability Hybrid sterility

Creation of a new species example

Hybridization between sunflowers give rise to a new species with unique characteristics

All over the world, natural habitats are being fragmented into tiny islands as suburbs, ranches, and farms expand and roads are built to connect them. Explain why this lead to extinction. Then explain how it could lead to speciation.

If the isolated population and habitat fragments are small enough, the species is likely to dwindle to extinction due to inbreeding and loss of genetic variation or catastrophes like a severe storm or a diseases outbreak. If the isolated populations survive, they are likely to diverge into new species because they are genetically isolated because habitats may differ.

Mechanical prezygotic isolation example

In alpine skypilots (a flowering plant) the length of the floral tube varies. Bees can primate in population with short tubes but only hummingbirds can pollinate in populations with long tubes

Gametic barrier prezygotic isolation example

In sea urchin a protein called binding allows sperm to penetrate eggs. Differences in the amino acid sequences of binding case mating's to fail between closely related populations

allopolypoid

Individuals are created when parents that belong to different species mate and produce an offspring with two different sets of chromosomes

Autopolyploid

Individuals are produced when a mutation results in a doubling of chromosome # and the chromosomes all come from the same species

polyploidization is virtually

Instantaneous

Hybrid zone

Is a geographic area where interbreeding occurs and hybrid offspring are common.

speciation

Is a splitting event that creates two or more distinct species from a single ancestral species

synapomorphy

Is a trait that is found in certain groups of organisms and their common ancestor

phylogenetic species concept disadvantages

It can be applied to any population (fossil, asexual, sexual). It is logical because different synaporphies only if they are isolated from gene flow and have evolved individuals

What distinguishes a morphospecies?

It has distinctive characteristics, such as size shape or coloration.

morphospecies concept disadvantages

It may lead to the naming of two or more species when there is only one polymorphic species with differing phenotype. It cannot identify cryptic species which differ in traits other than morphology. The morphological features used to distinguish species are subjective.

Hybrid zone formation example

Many stable hybrid zones have been described; the hybrid zone between hermit and Townsends warblers appear to have moved overt time

Gametic barrier prezygotic isolation

Mating fail because eggs and sperm are incompatible

Mechanical prezygotic isolation

Mating's fail because male and female reproductive structures are incomplete

Sister species

Meaning that they are each others closest relative

polyploidy

Occurs when an error in mitosis or mitosis results in a doubling of the chromosome # - a massive mutation.

Habitat prezygotic isolation example

Parasites that begin to exploit new host species are isolated from their original population

viscariance

Physical splitting up of a habitat

Why have polyploids been so successful

Polyploidy have higher levels of heterozygosity then their diploid relatives. Can tolerate higher levels of self-fertilization. Genes can duplicated chromosomes can diverge independently increasing genetic variation in the population.

Behavioral prezygotic isolation

Population do NOT interbreed because their courtship displays differ

Temporal prezygotic isolation

Populations are isolated because they breed at different times

Habitat prezygotic isolation

Populations are isolated because they breed in different habitats

allopatry

Populations that are geographically separated

prezygotic isolation

Prevents individuals of different species from mating

Biological species concept main criteria from identifying species

Reproductive isolation because no gene flow occurs between populations that are reproductively isolated from each other

morphospecies concept

Researchers identify evolutionary independent lineages by different size shape or other morphological features

Genetic divergence results from

Selection, genetic drift, and mutation proceed independently in the isolated population

Sexual selection is a type of natural selection that favors individuals with traits that increase their ability to obtain mates, such as females choice for bright orange beaks in zebra finches. Propose a scenario where sexual selection could contribute to divergence in sympatric speciation.

Sexual selection can promote divergence because it affects gene flow directly

Why are genetic isolation and genetic divergence occurring in apple maggot flies, even though populations occupy the same geographical area?

Small populations coalesce into one large population.

Sympatry

Together homeland species live in the same geographical area

Explain how isolation and divergence are occurring in apple maggot flies of the four evolutionary processes (mutation, gene flow, gene drift, selection), which two are most important in causing this event?

Some flies breed on apple fruits other breed on hawthorn fruits. This reduces gene flow, because apple fruits and hawthorn fruits have different scents and other characteristics is causing the population to diverge.

Dispersal and colonization followed by genetic drift and natural selection is thought to be responsible for

Speciation of Galapagos finches and many other island groups

prezygotic isolation types

Temporal Habitat Behavioral Gametic barrier Mechanical

Biological species concept

The definition of a species as a population or a group of populations that are reproductively isolated from other groups

Why is reinforcement an appropriate name for the concept that natural selection should favor divergence and genetic isolation if populations experience postzygotic isolation?

The selected trait reinforce differences that evolved while the populations were isolated from one another.

Fusion of the populations

The two populations freely interbreed

Behavioral prezygotic isolation example

To attract males fireflies, female fireflies give a species specific squences of flashes

A friend says that apple maggot flies prefer apple fruit scents because they need to in order to survive. Another agrees and adds that the flies acquire the ability to distinguish the apple scents by spending time on the fruit, and that's why their offspring prefer apples. What's wrong with these statements?

Two things: 1. Some flies happen to have alleges that allow them to respond to apple scents; others happen to have alleges that allow them to respond to hawthorn scents. There is no need involved. 2. The alleges for scent response exist; the are not acquired by spending time on the fruit.

Hybrid viability example

When ring necked doves mate with rock doves less than 6% of eggs hatch

Two types of polyploidy

autopolyploid allopolypoid

phylogenetic species concept

identifies species based on the evolutionary history of population

What concept is widely applicable. Useful when biologists have no data on the extent of gene flow and it is equally applicable to sexual, asexual or fossil species

morphospecies concept

Reproductive isolation can result from a wide variety of events and processes

prezygotic isolation postzygotic isolation