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