Chapter 14 The Origin of Species Lecture by Joan Sharp.

Chapter 14 The Origin of Species Lecture by Joan Sharp

14.2 There are several ways to define a species
Taxonomy is the branch of biology that names and classifies species and groups them into broader categories Carolus Linnaeus developed the binomial system of naming organisms – binomial nomenclature Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. Copyright © 2009 Pearson Education, Inc.

The biological species concept - population or group of populations whose members have the potential to interbreed in nature and produce fertile offspring Reproductive isolation prevents gene flow and maintains separate species Members of different species do not usually mate with each other. If members of one species do mate with members of another species, the offspring will probably not be fertile. Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. Copyright © 2009 Pearson Education, Inc.

Morphological – based on observable traits Ecological – identifies organisms based on their niches Phylogenetic – smallest group of individuals that share a common ancestor and forms one branch on the tree of life Point out that this is the concept actually used by most field biologists, who recognize their species by morphological traits. Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Before lecturing about species concepts, consider a short writing assignment. Have students work individually or in small groups, without the benefit of books, to define a species. Copyright © 2009 Pearson Education, Inc.

Figure 14.2A Similarity between the eastern spotted skunk (top) and western spotted skunk (bottom).

14.3 Reproductive barriers keep species separate
categorized as: 1. prezygotic – before the zygote forms 2. postzygotic - after zygotes form Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples always help to bring a point home. Copyright © 2009 Pearson Education, Inc.

Table 14.3 Reproductive Barriers between Species.

Prezygotic Barriers Prezygotic barriers prevent mating or fertilization between species In temporal isolation, two species breed at different times (seasons, times of day, years) In habitat isolation, two species live in the same general area but not in the same kind of place Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples always help to bring a point home. Copyright © 2009 Pearson Education, Inc.

Figure 14.3A Habitat isolation: Two closely related species of garter snake reproductively isolated because one lives on land (left) and the other lives mainly in water (right).

Figure 14.3B Behavioral Isolation: Courtship ritual in blue-footed boobies as a behavioral barrier between species.

Prezygotic Barriers In behavioral isolation, there is little or no sexual attraction between species, due to specific behaviors In mechanical isolation, female and male sex organs are not compatible In gametic isolation, female and male gametes are not compatible Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples always help to bring a point home. Copyright © 2009 Pearson Education, Inc.

Figure 14.3C Mechanical isolation: Because these snails' shells spiral in opposite directions, their genital openings (indicated by arrows) cannot be aligned and mating cannot occur.

Figure 14.3D Gametic isolation: Gametes of these red and purple urchins are unable to fuse because proteins on the surface of the eggs and sperm cannot bind to one another.

Postzygotic Barriers In reduced hybrid viability, most hybrid offspring do not survive In reduced hybrid fertility, hybrid offspring are vigorous but sterile In hybrid breakdown, the first-generation hybrids are viable and fertile, but the offspring of the hybrids are feeble or sterile The process of speciation depends on whether reproductive barriers prevent gene flow between populations Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples always help to bring a point home. Copyright © 2009 Pearson Education, Inc.

Figure 14.3E Reduced hybrid fertility: A horse (above left) and a donkey (above right) may produce a hybrid, sterile offspring, a mule.

If two related species live in the same area, would natural selection favor the evolution of prezygotic or postzygotic reproductive isolating mechanisms? Prezygotic reproductive isolating mechanisms are much less costly than postzygotic reproductive isolating mechanisms, which lead to provisioning and (in some species) care of an offspring that is an evolutionary dead end. Student Misconceptions and Concerns 1. Students might have never considered how species are naturally kept separate and unique. Instead, students may consider species as fixed entities, especially the species to which they belong. To help ease students into the topic, consider pointing out that species do not reflect an even spectrum of diversity. Instead, there are many groups of clearly related organisms (owls, grasses, sharks, beetles, butterflies, trees, mushrooms, and bacteria, for example). Ask students to consider why such grouping exists. Could such grouping represent shared ancestry? Teaching Tips 1. Identify or have your students find several commonly recognized and related species of plants or animals in your area and find out what reproductive barriers keep these species from interbreeding. Local examples always help to bring a point home. Copyright © 2009 Pearson Education, Inc.

MECHANISMS OF SPECIATION
MECHANISMS OF SPECIATION Copyright © 2009 Pearson Education, Inc.

14.4 In allopatric speciation, geographic isolation leads to speciation
In allopatric speciation, populations of the same species are geographically separated, separating their gene pools Changes in the allele frequencies of each population may be caused by natural selection, genetic drift, and mutation, unaffected by gene flow from other populations Student Misconceptions and Concerns 1. Students must understand that species do not evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate; it is reactive. Species do not deliberately change. There is no plan. As teachers, we must take care that our descriptions of evolution accurately reflect its process. The use of the passive voice in descriptions of evolution is one way of doing this. 2. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × = 31,557,600) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 3. Students also need to be reminded that 1 billion is 1,000 million. Many students (and some politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The isolation of a few individuals from a parent population may result from a catastrophic weather or geological event. Ask your students to think back to news footage of torrential rains, massive debris rocketing down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geological events may be rare in our lifetimes but are frequent enough to play a role in speciation. Copyright © 2009 Pearson Education, Inc.

Gene flow between populations is initially prevented by a geographic barrier The Grand Canyon and Colorado River separate two species of antelope squirrels Student Misconceptions and Concerns 1. Students must understand that species do not evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate; it is reactive. Species do not deliberately change. There is no plan. As teachers, we must take care that our descriptions of evolution accurately reflect its process. The use of the passive voice in descriptions of evolution is one way of doing this. 2. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × = 31,557,600) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 3. Students also need to be reminded that 1 billion is 1,000 million. Many students (and some politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The isolation of a few individuals from a parent population may result from a catastrophic weather or geological event. Ask your students to think back to news footage of torrential rains, massive debris rocketing down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geological events may be rare in our lifetimes but are frequent enough to play a role in speciation. Copyright © 2009 Pearson Education, Inc.

A. harrisi A. leucurus South North
Figure 14.4 Allopatric speciation of geographically isolated antelope squirrels. Ask students for other examples of suitable barriers, then make the point that the size and nature of the barrier vary from species to species. South North

Likelihood of allopatric speciation increases when a population is small and isolated A small population may have a different gene pool due to the founder effect Genetic drift and natural selection may have a greater effect in a small population in a new habitat Explain to your students that species do not evolve—or arise—because of need. Biological diversity exists and the environment selects. Evolution is not deliberate. It is reactive. Species do not decide or plan to change. Student Misconceptions and Concerns 1. Students must understand that species do not evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate; it is reactive. Species do not deliberately change. There is no plan. As teachers, we must take care that our descriptions of evolution accurately reflect its process. The use of the passive voice in descriptions of evolution is one way of doing this. 2. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × = 31,557,600) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 3. Students also need to be reminded that 1 billion is 1,000 million. Many students (and some politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The isolation of a few individuals from a parent population may result from a catastrophic weather or geological event. Ask your students to think back to news footage of torrential rains, massive debris rocketing down a river, and the struggles of animals to haul themselves onto these rafts. Better yet, show them a short news clip of such events. Dramatic weather and geological events may be rare in our lifetimes but are frequent enough to play a role in speciation. Copyright © 2009 Pearson Education, Inc.

14.5 In sympatric speciation, speciation takes place without geographic isolation
In sympatric speciation, new species may arise within the same geographic area as a parent species Gene flow between populations may be reduced by factors such as polyploidy, habitat differentiation, or sexual selection Student Misconceptions and Concerns 1. Students must understand that species do not evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate; it is reactive. Species do not deliberately change. There is no plan. As teachers, we must take care that our descriptions of evolution accurately reflect its process. The use of the passive voice in descriptions of evolution is one way of doing this. 2. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × = 31,557,600) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 3. Students also need to be reminded that 1 billion is 1,000 million. Many students (and some politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The Silvery Salamander, Ambystoma platineum, is a triploid, all female species living in parts of the U.S. Midwest. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. A good starting point for learning more about this species is Copyright © 2009 Pearson Education, Inc.

Many plant species have evolved by polyploidy, the multiplication of the chromosome number due to errors in cell division Student Misconceptions and Concerns 1. Students must understand that species do not evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate; it is reactive. Species do not deliberately change. There is no plan. As teachers, we must take care that our descriptions of evolution accurately reflect its process. The use of the passive voice in descriptions of evolution is one way of doing this. 2. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × = 31,557,600) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 3. Students also need to be reminded that 1 billion is 1,000 million. Many students (and some politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The Silvery Salamander, Ambystoma platineum, is a triploid, all female species living in parts of the U.S. Midwest. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. A good starting point for learning more about this species is Copyright © 2009 Pearson Education, Inc.

Sympatric speciation in animals more commonly occurs through habitat differentiation and sexual selection Remember the cichlids in Lake Victoria! Remind students that speciation events like the ones you are discussing are ongoing and are not limited to the distant past. Student Misconceptions and Concerns 1. Students must understand that species do not evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate; it is reactive. Species do not deliberately change. There is no plan. As teachers, we must take care that our descriptions of evolution accurately reflect its process. The use of the passive voice in descriptions of evolution is one way of doing this. 2. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × = 31,557,600) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 3. Students also need to be reminded that 1 billion is 1,000 million. Many students (and some politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. The Silvery Salamander, Ambystoma platineum, is a triploid, all female species living in parts of the U.S. Midwest. It is believed to have formed by the hybridization of two related species thousands of years ago. It is an unusual example of sympatric speciation in animals. A good starting point for learning more about this species is Copyright © 2009 Pearson Education, Inc.

Mating behavior often involves elaborate courtship rituals
Careful communication is an essential prerequisite for mating In many species, prospective mates must perform an elaborate courtship ritual The ritual confirms that individuals are of the same species, of the opposite sex Student Misconceptions and Concerns 1. Some students may believe that humans are somehow exceptional and that their behavior is not governed by the same principles as animal behavior. Other students may acknowledge these associations, but remain skeptical when it comes to individual examples. Behaviors, just like our biochemical and cellular structure, reveal our close kinship with animals and our descent from common ancestors. Teaching Tips 1. Students may believe that mating behavior is just about attracting a mate. As the authors note in Module 35.14, mating behavior also functions to confirm that an individual is a member of the species, establish that they belong to the opposite sex, and signal their intentions. For some species, such as spiders, miscommunication can result in death! Copyright © 2009 Pearson Education, Inc.

Figure 35.14A Male cuttlefish displaying colors for female.

Figure 35.15 A male jawfish with his mouth full of eggs.

14.10 Adaptive radiation may occur when new opportunities arise
In adaptive radiation, many diverse species evolve from a common ancestor Adaptive radiations occur When a few organisms colonize new unexploited areas After a mass extinction Adaptive radiations are linked to new opportunities: lack of competitors, varying habitats and food sources, evolution of new structures Provide examples: Darwin’s finches underwent an adaptive radiation after the ancestral finches colonized the new volcanic islands. The mammals underwent an adaptive radiation after the mass extinctions that ended the Cretaceous Period. Student Misconceptions and Concerns 1. Students must understand that species do not evolve because of need. Biological diversity exists and the environment selects. Evolution is not deliberate; it is reactive. Species do not deliberately change. There is no plan. As teachers, we must take care that our descriptions of evolution accurately reflect its process. The use of the passive voice in descriptions of evolution is one way of doing this. 2. Most of us are unable to comprehend the vast lengths of time considered by geologists. Exercises and examples can increase this comprehension. Consider the number of seconds in a year (60 × 60 × 24 × = 31,557,600) or how much money you could spend each day if you spent $1 million a year ($1,000,000/365 = $2,739.73/day). 3. Students also need to be reminded that 1 billion is 1,000 million. Many students (and some politicians) easily confuse million and billion without realizing the scale of the error. Teaching Tips 1. An analogy might be made between the specialized functions of finch beaks and the many types of screwdrivers (or pliers) that exist today. Each type of screwdriver (Phillips, flathead, long-handled) represents a specialization for a particular job or a generalist approach, useful in a variety of applications. 2. Numerous examples of adaptive radiations exist in the Hawaiian Islands. Hawaiian honeycreepers (birds), fruit flies, and species of the plant genera Cyrtandra and Geranium are excellent examples for additional illustration. Copyright © 2009 Pearson Education, Inc.

Time Figure 14.11A Punctuated equilibrium model.

Figure 14.11B Gradualism model.
Time

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