Ch. 22 - The Origin Of Species Flashcards
Speciation
The process by which one species splits into two or more species
microevolution
changes over time in allele frequencies in a population
macroevolution
the board pattern of evolution above the species level
biological species concept
a species is a group of populations whose members have the potential to interbreed in nature and produce viable, fertile offspring
reproductive isolation
the existence of biological barriers (not always physical) that impede members of two species from interbreeding and producing viable, fertile offspring
prezygotic barrier
blocks fertilization from occurring
postzygotic barrier
contribute to reproductive isolation after the hybrid zygote is formed
habitat isolation
species in the same area occupy different habitats, rarely encounter each other
temporal isolation
species mate different times of day/season/year
behavioral isolations
courtship rituals meant to attract members of on species will not attract other species
mechanical isolation
morphological differences prevent attempted mating from success
gametic isolation
sperm of one species is unable to fertilize the egg of the other species
reduced hybrid viability
combine genes may interact in ways that impair the hybrid’s development or survival in an environment
reduced hybrid fertility
hybrids may be able to survive successfully, but are naturally sterile, incapable of correctly forming gametes
hybrid breakdown
first generation are fertile and viable but the next generation are feeble or sterile
morphological species concept
characters a species by body shape and other structural features
ecological species concept
a species in terms of its ecological niche
phylogenic species concept
a species is the smallest group of individuals that share a common ancestor, forming on branch on the tree of life
allopatric speciation
gene flow is interrupted when a population is divided into geographically isolated subpopulations
sympatric speciation
occurs in populations that live in the same geographical area
polyploidy
species originate from an accident during cell division that results in extra sets of chromosomes
autopolyploid
an individual that has more than two chromosome sets that are all derived from a single species
allopolyploid
a fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combining their chromosomes
habitat differentiation
when genetic factors allow a subpopulation to exploit a habitat or resource not used by the parent population
hybrid zone
a region in which members of different species meet and mate, producing at least some offspring of mixed ancestry
reinforcement (hybrid zone)
reproductive barriers strengthen, reinforces reproductive barriers, hybrids cease to exist
fusion
reproductive barriers weaken, the two species fuse into one
stability
continuous production of hybrids
punctuated equilibria
periods of apparent stasis punctuated by sudden change or disappearance
When gene flow between two populations ceases, the potential for _____ exists.
speciation
Bird guides once listed the myrtle warbler and Audubon’s warbler as distinct species that lived side by side in parts of their ranges. However, recent books show them as eastern and western forms of a single species, the yellow-rumped warbler. Apparently, the myrtle warbler and Audubon’s warbler…
successfully interbreed and produce fertile offspring
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?
Individuals from the different populations sometimes mate with each other, but all of the resulting eggs are sterile.
Which of the following conditions is necessary for speciation to occur?
reproductive isolation
Prezygotic barriers…
prevent fertilization of gametes from members of closely related species
Three species of frogs, Rana pipiens, Rana clamitans, and Rana sylvatica, all mate in the same ponds, but they pair off correctly because they have different calls. This is a specific example of a _____ barrier, called _____.
prezygotic … behavioral isolation
Which of the following reproductive barriers actually prevents individuals of closely related species from copulating successfully?
mechanical isolation
Two species of water lilies in the same pond do not interbreed because one blooms at night and the other during the day. The reproductive barrier between them is an example of…
temporal isolation
Which of the following is an example of a postzygotic reproductive barrier
Two fruit flies of different species produce sterile offspring.
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
The phylogenetic species concept emphasizes…
common ancestry
Lake Victoria, in Africa, is home to a group of related fishes known as cichlids. Many of these fishes are similar in appearance but have different feeding habits. What is the best method for scientists to determine conclusively whether the fish are members of a population that has a lot of variation or members of entirely different species?
Observe the fish in their natural environment for possible instances of interbreeding leading to several generations of fertile offspring.
in practice, how do scientists distinguish most species?
by using the morphological species concept
Which species concept defines a species as a set of organisms with a unique genetic history?
phylogenetic species concept
Sometimes two phenotypically different populations interbreed to a limited extent, so that it is difficult to determine whether they are clearly separate species. This is not a concern to scientists because this…
may indicate that the formation of a new species is in progress
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
Which of the following evolutionary mechanisms does NOT contribute to the process of allopatric speciation?
gene flow
If a new species of plant is to be produced by means of allopolyploidy from two parental species that are 2n = 4 and 2n = 8, how many chromosomes would you expect in the somatic cells of the new species?
12
A new species can arise in a single generation…
if a change in chromosome number creates a reproductive barrier
The Galápagos finches collected by Darwin are thought to have descended from a very small parent population. Different species of finches that are confined to only one or two islands most likely arose by…
allopatric speciation
In the case of the Lake Victoria cichlids, sympatric speciation has been shown to be driven by…
sexual selection
In the Lake Victoria cichlids, what appears to be contributing to fusion of different species?
Females have a difficult time visually selecting males of the same species in the murky, polluted water.
According to the punctuated equilibrium model of evolution…
the tempo of evolution consists of abrupt episodes of speciation among long periods of equilibrium
Comparison of human fossils with living humans seems to show that there have been no significant physical changes in Homo sapiens in 30,000 to 50,000 years. What might an advocate of punctuated equilibrium say about this?
Lack of change is consistent with the punctuated equilibrium model.
What is the first thing that must happen in order for speciation to occur?
Gene flow between populations must be interrupted.
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.
The time interval between speciation events is typically…
Times between speciation events vary widely and depend on generation times, causes of speciation, environmental factors, and chance.
