Ch. 24 Origin of Species

Postzygotic barriers

block development of viable, fertile individuals

Polyploidy

condition in which an organism has extra sets of chromosomes Two types: Autopolyploid Allopolyploid

Biological species concept

Species is a group of populations whose members have the potential to produce fertile offspring.

Reinforcement

reinforcing reproductive barriers for hybrid species Hybrids are usually less fit then their parents species.

If goats are crossed with sheep, embryos will form but cease development and spontaneously abort. This is an example of: A) a prezygotic mechanism. B) hybrid inviability. C) hybrid sterility. D) hybrid breakdown.

B) hybrid inviability.

Anagenesis (phyletic evolution)

one species replaces another over time, straight path evolution accumulation of heritable change in population

Prezygotic barriers

prevent formation of zygote

Reproductive isolation

prevents one species from interbreeding with other species. Two categories: 1. Prezygotic barriers: prevent formation of zygote 2. Postzygotic barriers: fertilization occurs, zygote forms, but barriers block development of viable, fertile individuals

Microevolution

changes over time in allele frequencies in a population

Species Concept: How to Distinguish Species

1. Phylogeny 2. Biology: ability to interbreed, produce fertile offspring 3. Analysis of ancestry 4. Ecology: niche occupied

Ecological species concept

A definition of species in terms of ecological niche or habitat the sum of how members of the species interact with the nonliving and living parts of their environment.

Allopolyploid

A fertile individual that has more than two chromosome sets as a result of two different species interbreeding and combining their chromosomes.

Which one of the following is reproductive isolating mechanisms is particularly important to flowering plants? A) gametic isolation B) hybrid inviability C) hybrid stability D) temporal isolation E) habitat isolation

A) gametic isolation

Evolutionary changes that create new species and groups of species are most accurately referred to as: A) natural selection. B) macroevolution. C) microevolution. D) horizontal gene transfer. E)vertical descent.

B) macroevolution.

When gene flow between two populations ceases, the potential for __________ exists. (Concept 24.1) SHOW HINT A)sexual reproduction B)speciation C) hybridization D) fusion E) sexual selection

B)speciation

When a single species is transformed into a different species over the course of many generations, this is most accurately referred to as: A) extinction. B) endosymbiosis. C) cladogenesis. D) anagenesis. E) polymorphism.

D) anagenesis.

Evolutionary species concept

Defines species according to evolutionary history and common ancestors

Cladogenesis (branching evolution)

One species divides into 2 or more species New species arises from population that buds from parent species The original species still exists More common form of speciation Usually due to separation of population into isolated groups Ex. Galapagos finches

Hybridization

Prior to complete reproductive isolation, the zones where two populations can interbreed are known as hybrid zones.

Adaptive Radiation on islands:

Single ancestral species evolves into numerous descendant species Each differs in habitat, behavior, or form adaptations to feeding have produced species with notable differences in beak morphology. Examples: Honeycreepers, Galapagos Finches

Autopolyploid

an individual that has more than two chromosome sets that are all derived from a single species

Interspecies hybrid

offspring forms when 2 closely related (but different) species mate Hybrid is typically sterile ex. Donkey x house= mule tiger x lion= tigon or tiglon (liger)

Macroevoluation

the board pattern of evolution above the species level

Speciation

the process by which one species splits into two or more species

Allopatric speciation

the process of speciation that occurs with geographic isolation; the separated populations evolve differently in the separate environments and eventually form distinct species.

Gradualism (Speed of speciation)

(Continuous) The theory that evolution occurs slowly but steadily for a long time span

Causes of Allopatric Speciation:

1. Founder effect 2. Geological change (example, continental drift) 3. Adaptive radiation on islands

Punctuated equilibrium (Speed of speciation)

(Sporadic) The theory that species evolve during short sudden periods of rapid bursts of change in species "Sudden" means 10's of thousands of years

Subspecies

Distinctive variant forms of a species which are separated geographically and generally interbreed only where ranges overlap

POSTZYGOTIC BARRIERS (after zygote forms) 1. Reduced hybrid viability (hybrid inviability) 2. Reduced hybrid fertility (Hybrid sterility)

1. Reduced hybrid viability (hybrid inviability) Embryo dies early in development 2. Reduced hybrid fertility (Hybrid sterility) Viable, vigorous hybrid cannot reproduce (fails to form functional gametes) Example: mule (cross between male donkey and female horse) is sterile and has no functional gametes (photo below)

The concept that the tempo of evolution is sporadic is known as ________________, while the concept that the tempo of evolution is continuous is known as ______________. A) punctuated equilibrium; gradualism B) Darwinism; neo-Darwinism C) revolutionism; conservatism D) gradualism; Darwinism E) conservatism; punctuated equilibrium

A) punctuated equilibrium; gradualism

Which of the following is the first step in allopatric speciation? A) genetic drift B) doubling of chromosome number C) geographical isolation D) development of a reproductive isolating mechanism

C) geographical isolation

PREZYGOTIC BARRIERS (before zygote formation) 1. Habitat Isolation 2. Temporal Isolation 3. Behavioral Isolation 4. Mechanical Isolation 5. Gametic Isolation

1. Habitat Isolation Geographical (no contact) Ecological (no contact) -utilization of different portions of a contiguous habitat -example: two closely related lizards live in your yard, but one lives and feeds in the upper canopy of the trees while the other lives and feeds on the ground. 2. Temporal Isolation Timing is everything! Example: two species of frog live in the same pond, but one species only breeds in June and the other only breeds in August 3. Behavioral Isolation Courtship rituals (i.e. bird songs) Their songs are distinct, a behavioral difference that helps prevent interbreeding between the two species. 4. Mechanical Isolation Ex: Mismatched genitalia do not fit together Body design is such that mating is impossible with another species Mismatched size mates interspecific mating impossible 5. Gametic Isolation Incompatible gametes (even if you mate with another species, the sperm cannot fertilize the egg)

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? A.) Individuals from the different populations sometimes mate with each other, but all of the resulting eggs are sterile. B. ) Hybrid offspring of matings between individuals from the two populations do not look like either parent. C.) Individuals from the different populations frequently direct courtship behavior toward members of the other population. D.) The preferred food of the island birds is quite different from the diet of mainland birds. E) The island birds all have red feathers, but the mainland birds have green feathers.

A.) Individuals from the different populations sometimes mate with each other, but all of the resulting eggs are sterile. The biological species concept defines a species as a population whose members interbreed successfully to produce viable, fertile offspring but who cannot produce viable, fertile offspring with members of other species.

Which of the following is an example of a postzygotic reproductive barrier? A.)Two pheasant species perform different courtship dances. B.) Two fruit flies of different species produce sterile offspring. C.) One species of frog mates in April, but another mates in May. D.) The sperm of a marine worm can only fertilize eggs of the same species. E.) One species of flower grows in forested areas, another in meadows.

B.) Two fruit flies of different species produce sterile offspring. This scenario represents reduced hybrid fertility.

Question 12: 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 A. ) is quite rare B.) may indicate that the formation of a new species is in progress c.) is true for almost every species D.) happens only among plants, not among animals E.) supports the theory of punctuated equilibrium

B.) may indicate that the formation of a new species is in progress This could indicate that although a reproductive barrier is becoming established, it is not yet complete.

Which of the following reproductive barriers actually prevents individuals of closely related species from copulating successfully? A.) hybrid inviability B.) mechanical isolation C.) hybrid breakdown D.) gametic isolation E.) hybrid sterility

B.) mechanical isolation With mechanical isolation, mating cannot occur successfully due to incompatibility of reproductive parts.

Which of the following conditions is necessary for speciation to occur? A.) mass extinction B.) reproductive isolation C.) interbreeding among neighboring populations D.) sympatric speciation E.) adaptive radiation

B.) reproductive isolation The biological species concept hinges on reproductive 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 A.) ecological isolation B.) temporal isolation C.) gametic isolation D.) hybrid breakdown E.) mechanical isolation

B.) temporal isolation The gametes of species that breed during different times of the day, different seasons, or different years do not have an opportunity to combine and create a zygote.

At which point in the adaptation of a population is it clear that speciation has occurred? A) Gene pool changes adapt a population to a local environment. B) An allopatric separation occurs. C) Gene pool changes establish reproductive barriers between two populations. D) Viable, fertile hybrids occur. E) All of the listed responses are correct.

C) Gene pool changes establish reproductive barriers between two populations. This is an example of separate species being created.

According to the experiment of Diane Dodd, can adaptive divergence of allopatric fruit fly populations lead to reproductive isolation? A) No. After several generations, the formation of a reproductive barrier (mechanical isolation) was evident, but not absolute. B) Yes. After several generations, the reproductive barrier (behavioral isolation) between the starch- and maltose-fed populations was complete. C) No. After several generations, the formation of a reproductive barrier (behavioral isolation) was evident, but not absolute. D) No. Even after several generations, there was no evidence of a reproductive barrier forming between the populations. E) Yes. After several generations, the reproductive barrier (mechanical isolation) between the starch- and maltose-fed populations was complete.

C) No. After several generations, the formation of a reproductive barrier (behavioral isolation) was evident, but not absolute. The starch flies were more apt to mate with other starch flies and the maltose flies were more apt to mate with other maltose flies, but some interbreeding still did occur.

American sycamore (Platanus occidentalis) and European sycamore (Platanus orientalis) are tree species that will interbreed if planted nearby but will not normally interbreed because they occur on different continents. This is an example of: A) mechanical isolation. B) temporal isolation. C) habitat isolation. D) behavioral isolation. E) gametic isolation.

C) habitat isolation.

The process of evolutionary changes that result in formation of new species is called: A) temporal evolution. B) microevolution. C) macroevolution. D) serial evolution.

C) macroevolution.

Question 11: 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 A.) Compare DNA sequences, because the DNA of members of the same species should be identical. B.) Do studies on comparative anatomy, especially looking for homologous structures. C.) Observe the fish in their natural environment for possible instances of interbreeding leading to several generations of fertile offspring. D.) Study the fossil record. E.) All of the listed responses are correct.

C.) Observe the fish in their natural environment for possible instances of interbreeding leading to several generations of fertile offspring. The biological species concept defines a species as a population whose members interbreed successfully to produce viable, fertile offspring but who cannot produce viable, fertile offspring with members of other species.

Prezygotic barriers A) are necessary in order for speciation to occur B) prevent a hybrid zygote from developing into a viable, fertile adult C.) prevent fertilization of gametes from members of closely related species D) only occur in asexual organisms E.) prevent donkeys and horses from mating

C.) prevent fertilization of gametes from members of closely related species Prezygotic barriers act prior to fertilization to prevent interbreeding between sibling 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 __________. A.) prezygotic ... temporal isolation B.) prezygotic ... gametic isolation C.) prezygotic ... behavioral isolation D.) postzygotic ... hybrid breakdown E.) postzygotic ... mechanical isolation

C.) prezygotic ... behavioral isolation It occurs before fertilization and is due to different reproductive behaviors in sibling species.

Geological Change Separates the original population into separate groups.

Caused by continental drift, earthquake, volcanic eruption, erosion, etc.

Which of the following statements about meiosis is correct? A) In meiosis, each cell division produces two genetically identical daughter cells. B) Crossing over cannot occur during meiosis. C) Meiosis in a diploid cell produces diploid daughter cells. D) Meiosis produces cells that differ genetically from the parent cell.

D) Meiosis produces cells that differ genetically from the parent cell. If you had trouble with this question, review the following material: Meiosis in a diploid cell produces two haploid cells that differ genetically from one another and from the diploid parent cell. This occurs in part because in meiosis, the independent assortment of homologous chromosomes results in each daughter cell receiving one of 2n (where n is the haploid chromosome number) possible combinations of the maternal and paternal chromosomes. Another reason is that crossing over may occur during meiosis, thereby producing recombinant chromosomes that carry genes derived from two different parents.

In a species that has two chromosomes, suppose that a male has genotype aa for a gene on chromosome 1 and genotype bb for a gene on chromosome 2. If a female of this species has genotype AA for the gene on chromosome 1 and genotype BB for the gene on chromosome 2, which of the following represents the possible genotypes in a cell of their offspring? A.) AB on chromosome 1, ab on chromosome 2 B.) AA on chromosome 1, bb on chromosome 2 C.) Aa on chromosome 1, Bb on chromosome 2 D) aB on chromosome 1, Ab on chromosome 2

D) aB on chromosome 1, Ab on chromosome 2 If you had trouble with this question, review the following material: Each sperm produced by the male contains one copy of chromosome 1 (carrying the a allele) and one copy of chromosome 2 (carrying the b allele), whereas each egg produced by the female contains one copy of chromosome 1 (carrying the A allele) and one copy of chromosome 2 (carrying the B allele). Thus, when any egg and sperm cells unite, the offspring cells will have genotype Aa on chromosome 1 and genotype Bb on chromosome 2.

When hybrids form between species of cotton, Gossypium barbadense, G. hirsutum, and G. tomentosum, they grow well and are fertile, but their progenies' seeds die or the seedlings wilt and die. This is an example of: A) a prezygotic mechanism. B) hybrid inviability. C) hybrid sterility. D) hybrid breakdown.

D) hybrid breakdown.

According to the punctuated equilibrium model of speciation: A) most evolution occurs in sympatric populations. B) given enough time, most existing species will branch gradually into new species. C) speciation is usually due to a single mutation. D) most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

D) most new species accumulate their unique features relatively rapidly as they come into existence, then change little for the rest of their duration as a species.

Which one of the following is not an example of a prezygotic reproductive isolating mechanism? A) failure of gametes to unite B) differences in sexual attraction C) morphological incompatibility D) sterile interspecies hybrids E) geographic barriers

D) sterile interspecies hybrids

A windstorm transports a few seeds of a plant species from Island A, where the species is abundant, to Island B, where prior to this event the plant species was not found. The environmental conditions on the two islands are very similar, but the islands are located far away from one another. Over time, a small population of this plant becomes established on Island B. A biologist samples plants on both islands and finds that allele frequencies on Island A differ substantially from allele frequencies on Island B at several genetic loci not known to affect survival or reproduction. Based on this information, the observed genetic changes mostly likely resulted from A.) genetic drift. B.) mutation. C.) gene flow (after the species became established on Island B). D.) natural selection.

D.) natural selection. If you had trouble with this question, review the following material: Since, the environmental conditions on the two islands are very similar and the genetic loci sampled are not known to affect survival or reproduction, it is not likely that the observed differences were caused by natural selection. Gene flow causes populations to become more similar genetically over time, not more different. However, the observed differences could well be caused by genetic drift, the fluctuation of allele frequencies from one generation to the next in a population due to chance events; for example, the founder effect often causes members of a new population (such as that on Island B) to differ genetically from members of the source population (Island A).

Even if mating occurs between a female fruit fly of the species Drosophila pulchrella and a male D. suzukii, the sperm will not be able to fertilize the eggs. This is an example of: A) mechanical isolation. B) temporal isolation. C) habitat isolation. D) behavioral isolation. E) gametic isolation.

E) gametic isolation.

In which of the following pairs of populations is allopatric speciation most likely to occur? A.) fruit flies on bananas and fruit flies on oranges B.) mountain lions in the canyons of Wyoming and in the nearby canyons of Utah C.) whale populations of the same species located on opposite sides of the Atlantic Ocean D.) bacteria in a hospital and bacteria in a nursery E) pine trees in Alaska and pine trees on the island of Madagascar

E) pine trees in Alaska and pine trees on the island of Madagascar This is geographic isolation that could lead to allopatric speciation, for it is unlikely that pollen from one locale could get to the other locale.

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 __________. (Concept 24.1) SHOW HINT A) are almost identical in appearance B.)have undergone coevolution C.) are merging to form a single species D) live in the same areas E) successfully interbreed and produce fertile offspring

E) successfully interbreed and produce fertile 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? A.) a geographic barrier B.) hybrid inviability C.) mechanical isolation D.) gametic isolation E.) temporal isolation

E.) temporal isolation Temporal isolation occurs when two similar species have sexual readiness at different times.

Founder Effect

Small population becomes relocated to new location that is geographically separated and has no further contact with the rest of the original population Example: Galapagos finches arrived on islands far from their mainland home

Sympatric Speciation

The formation of new species in populations that live in the same geographic area Biological factors, such as chromosomal changes and nonrandom mating, reduce gene flow Cause: abrupt genetic changes can result through random mutation This type of speciation is very rare in animals (usually occurs in plants)

Speed of speciation

The time (tempo) it takes for a new species to arise varies

Species

a group of organisms whose members have the ability or potential to interbreed in nature and produce a viable, fertile offspring.