BSC 2011: Ch 24

A new species of plant evolved by allopolyploidy from two species of plant that are 2n = 6 and 2n = 12. What would the diploid number of chromosomes be in this new species?

18 In this situation, the gametes from the parents would be n = 3 and n = 6. They would combine for a total of 9, which after doubling is 18.

A new species of plant arises as an allopolyploid from two other plants, one with a diploid number of 14 and one with a diploid number of 18. What would the diploid number of the new species most likely be?

32

What is genetic drift?

A change in allele frequencies caused by random events

In the oceans on either side of the Isthmus of Panama are 30 species of snapping shrimp; some are shallow-water species, others are adapted to deep water. There are 15 species on the Pacific side and 15 different species on the Atlantic side. The Isthmus of Panama started rising about 10 million years ago. The oceans were completely separated by the isthmus about 3 million years ago. In the figure, the isthmus separates the Pacific Ocean on the left (side A) from the Atlantic Ocean on the right (side B). The seawater on either side of the isthmus is separated into five depth habitats (1-5), with 1 being the shallowest. -A1 and B5 -A5 and B5 -A1 and A5 -Both A1/A5 and B1/B5 should have the greatest, but equal amounts of, genetic divergence

A5 and B5

A new species of plant is discovered that closely resembles a known species. Upon further examination, it is discovered that the new species has a tetraploid number of 4n = 12, while the known species has a diploid number of 2n = 6. Which of the following statements provides a reasonable explanation for the evolution of this new species of plant?

An error in cell division occurred in the known species, leading to the development of an autopolyploid tetraploid offspring that evolved into the new species.

___ ___ occurs when two species' courtship rituals do not elicit any response from each other.

Behavioral isolation

Prezygotic barriers can occur in what three ways?

By impeding members of different species from attempting to mate, by preventing an attempted mating from being completed successfully, or by hindering fertilization if mating is completed successfully.

Imagine that part of a population of South American finches is blown by a storm onto an island far offshore and manages to survive and reproduce there for a period of 10,000 years. After that period, a climate change results in lower sea levels and the reconnection of the island with the mainland. Members of the formerly isolated island finch population can now interact freely with members of the original mainland population. Which of the following observations would, by itself, lead you to conclude unequivocally that the island finch population had evolved into a distinct species, according to the biological species concept?

Correct answer: Individuals from the different populations sometimes mate with each other, but all of the resulting eggs are sterile. Incorrect answers: 1. Hybrid offspring of matings between individuals from the two populations do not look like either parent. 2. The island birds all have red feathers, but the mainland birds have green feathers. 3. The preferred food of the island birds is quite different from the diet of mainland birds. 4. Individuals from the different populations frequently direct courtship behavior toward members of the other population.

A mating between a tetraploid individual and a diploid individual produces biologically fit offspring.

False

The last ice age produced many different species mainly because populations dispersed and colonized new habitats.

False

True or False, Hybrids are the only offspring produced in a hybrid zone.

False, other offspring are produced as well.

___ refers to two or more populations re-establishing gene flow and forming one species.

Fusion

___ ___ occurs when gametes from different species do not fertilize each other.

Gametic isolation

What prevents speciation from occurring in sympatric populations?

Gene flow

Which of the following evolutionary mechanisms does not contribute to the process of allopatric speciation?

Gene flow

What is the first thing that must happen in order for speciation to occur?

Gene flow between populations must be interrupted.

At which point in the adaptation of a population is it clear that speciation has occurred?

Gene pool changes establish reproductive barriers between two populations.

These three things affect allopatric speciation: ___ ___ can result in reproductive isolation of allopatric populations, increasing the likelihood of speciation. Because ___ are random, when they occur in isolated allopatric populations they increase the likelihood of speciation occurring. ___ ___ can result in reproductive isolation of allopatric populations, increasing the likelihood of speciation.

Genetic drift; mutations; Natural selection

___ separation is not always necessary for speciation and it may be gradual, not catastrophic.

Geographic

___ is the broad pattern of evolution above the species level.

Macroevolution

Which of the following reproductive barriers actually prevents individuals of reproductively compatible related species from copulating successfully?

Mechanical isolation

How can an allopolyploid plant become a biologically fit new species?

Nondisjunction event during mitosis

Which of the following organisms is most likely to be subject to allopatric speciation?

Pine trees in Alaska and pine trees on the island of Madagascar

In which of the following groups has sympatric speciation been most important?

Plants

Which of the following statements about reinforcement is true?

Reinforcement is a type of natural selection.

___ is the process by which one species splits into two or more species.

Speciation

Which of the following statements correctly describes one aspect of the punctuated model of evolution?

Species tend to change rapidly in a short period of time.

Which term is used to describe populations that live close enough to interbreed?

Sympatry

There are two groups of pine trees that appear to be very similar phenotypically and genotypically. However, one releases pollen in January, when the female structures of that group are receptive, and one in March. What kind of reproductive barrier is this?

Temporal isolation

___ ___ occurs when two similar species have sexual readiness at different times.

Temporal isolation

Two hypothetical species of sparrow, A and B, overwinter together in mixed flocks in Costa Rica. In spring, species A goes to the east coast of North America, and species B goes to the west coast. What can you say about the isolating mechanisms of these two species? -They must have strong prezygotic isolating mechanisms to spend winter in such close proximity. -Reinforcement must be occurring when they winter together. -Their winter habitat has no bearing on their degree of reproductive isolation. -They must have strong postzygotic isolating mechanisms to spend winter in such close proximity.

Their winter habitat has no bearing on their degree of reproductive isolation.

How many genes must change in order to form a new species?

There is no set number of genes or loci that produces a new species. Genetic and environmental factors interact.

Which of the following statements about autopolyploid individuals is true?

They contain more than two haploid sets of chromosomes.

A flood that separates a population of frogs onto opposite sides of a lake is an example of a vicariance event that may result in allopatric speciation.

True

Which of the following is an example of a postzygotic reproductive barrier?

Two fruit flies of different species produce sterile offspring.

Sympatric speciation typically occurs by all of the following mechanisms except __________.

a geographic barrier splitting a population

A hybrid zone is defined as __________.

a region in which members of different species meet and mate, producing at least some offspring of mixed ancestry

In ___ ___ , gene flow is interrupted when a population is divided into geographically isolated subpopulations. For example, the water level in a lake may subside, resulting in two or more smaller lakes that are now home to separated populations.

allopatric speciation

Reproductive isolation may then arise as a by-product of ___ ___ or drift having caused the populations to diverge genetically.

allopatric speciation

The evolution of multiple species of snapping shrimp following the formation of the Isthmus of Panama is an example of __________.

allopatric speciation

An infertile hybrid may be able to propagate itself asexually (as many plants can do). In subsequent generations, various mechanisms can change a sterile hybrid into a fertile polyploid called an ___.

allopolyploid

The ___ are fertile when mating with each other but cannot interbreed with either parent species; thus, they represent a new biological species.

allopolyploids

Sympatric speciation does not seem to have been an important factor in ___ speciation.

animal

An ___ is an individual that has more than two chromosome sets that are all derived from a single species. In plants, for example, a failure of ___ ___ could double a cell's chromosome number from the original number (2n) to a tetraploid number (4n).

autopolyploid; cell division

Regardless of whether they have complex or simple spatial patterns, hybrid zones form when two species lacking complete ___ to reproduction come into contact.

barriers

The behavior of a male blue-footed boobie during the courtship ritual elicits no response from the masked boobie. The reproductive barrier between them is an example of __________.

behavioral isolation

According to the __________, a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring—but do not produce viable, fertile offspring with members of other such groups.

biological species concept

According to the ___ ___ concept, a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring—but do not produce viable, fertile offspring with members of other such groups. Thus, the members of a ___ ___ are united by being ___ ___, at least potentially.

biological species; biological species; reproductively compatible

3 Species concept=

biological, morphological, and phylogenetic

The morphological species concept distinguishes species by __________.

body shape and other structural features

morphological species concept is the similarity in ___. It is easy to apply and works for ___ and ___ species. Researchers may disagree on ___.

body structures; asexual and extinct; which structures are important

The morphological species concept DEFINES species based on ___ ___.

common ancestry

Postzygotic barriers __________.

contribute to reproductive isolation after a hybrid zygote has been formed

biological species concept depends on the ability of a species to ___. It goes hand-in-hand with ___.objective. It is not applicable to ___ or ___ species

create viable, fertile offspring; gene flow concept; extinct or asexual

The ___ ___ concept defines species based on their ecological niche.

ecological species

phylogenetic species concept is common ___. It is based on actual ___, and it works for _ and __ species. It requires good ___

evolutionary history; relationships; asexual and extinct; evolutionary histories

With ___ ___, mating occurs, but the gametes are not compatible.

gametic isolation

Hybridization would mark the beginning of ___ ___ between two formerly isolated populations.

gene flow

The ___ ___ of evolution states that species tend to change slowly over a long period of time.

gradual model

Two different species of frogs mate successfully and produce fertile hybrid offspring. However, the offspring of the hybrids do not develop completely to adulthood. This is an example of which type of reproductive barrier?

hybrid breakdown

With ___ ___, mating occurs, but the second-generation hybrid is not viable.

hybrid breakdown

With ___ ___, mating occurs, but the resulting hybrid is weak and unlikely to survive to reproduce.

hybrid inviability

With ___ ___, mating occurs, but the resulting hybrid is sterile.

hybrid sterility

With ___ ___, mating cannot occur successfully due to incompatibility of reproductive parts.

mechanical isolation

You are confronted with a box of preserved grasshoppers of various species that are new to science and have not been described. Your assignment is to separate them into species. There is no accompanying information as to where or when they were collected. Which species concept will you have to use?

morphological

The ___ ___ concept can be applied to asexual and sexual organisms and can be useful even without information on the extent of gene flow

morphological species

The ___ ___ concept defines a species as the smallest group of individuals that share a common ancestor, forming one branch on the tree of life.

phylogenetic species

Most ___ hybrids are sterile because the set of chromosomes from one species cannot pair during meiosis with the set of chromosomes from the other species.

polyploid

An accident during cell division that results in extra sets of chromosomes.

polyploidy

Most causes of speciation are relatively slow, in that they may take many generations to see changes, with the exception of _____. -colonization -polyploidy -reinforcement -natural selection

polyploidy

Sympatric speciation can occur if gene flow is reduced by such factors as ___, ___ ___, and ___ ___.

polyploidy; habitat differentiation; sexual selection

A horse and a donkey can reproduce successfully, producing a mule. However, the mule is sterile. This is an example of a __________ barrier called __________.

postzygotic; reduced hybrid fertility

Prezygotic barriers __________.

prevent fertilization of gametes from members of closely related species

Three species of sea stars all mate near the same reef by secreting their gametes into the water, but none of the gametes from the different species fertilize each other. This is an example of a __________ barrier called __________.

prezygotic; gametic isolation

___ ___ are periods of apparent evolutionary stasis punctuated by sudden change.

punctuated equilibria

Developmental errors may reduce survival among hybrid embryos. Or problems after birth may cause hybrids to be infertile, known as ___ ___ ___, or decrease their chance of surviving long enough to reproduce.

reduced hybrid fertility

If biological species are defined in terms of reproductive compatibility, the formation of a new species hinges on ________.

reproductive isolation

Since hybrids are produced in a hybrid zone, ___ ___ does not totally limit mating between individuals of the two populations.

reproductive isolation

The biological species concept defines species based on ___ ___.

reproductive isolation

In the case of the Lake Victoria cichlids, sympatric speciation has been shown to be driven by __________.

sexual selection

Reproductive isolation is necessary for __________ to occur.

speciation

Though polyploidy can stop gene flow almost instantaneously, it is not very common, nor is it necessary for ___ to occur.

speciation

When gene flow between two populations ceases, the potential for __________ exists.

speciation

According to the punctuated equilibrium model of evolution, __________.

the tempo of evolution consists of abrupt episodes of speciation among long periods of equilibrium

The time interval between speciation events __________.

vary widely and depend on generation times, causes of speciation, environmental factors, and chance

Hybrid zones are typically located .....

wherever the habitats of the interbreeding species meet.

A hybrid ___ could not be established until gene flow had already been interrupted for some length of time.

zone