22 The Origin of Species Fleur Ferro, Community College of Denver 22 The Origin of Species Questions prepared by Fleur Ferro, Community College of Denver Jung Choi, Georgia Institute of Technology Michael Dini, Texas Tech University

Cynotilapia afra, introduced at West Thumbi Island in Lake Malawi in the 1960s, has split into two genetically distinct populations, located at the north and south ends of the island. How can scientists determine whether these populations are now different species, according to the biological species concept? See whether the two populations are morphologically different from each other: coloring, bone structure, and so on. Determine whether captured individuals from the two different populations will mate and produce offspring in a laboratory fish tank. Determine whether individuals from one population will interbreed with individuals from the other population when introduced into each other’s native habitats. Answer: C

Cynotilapia afra, introduced at West Thumbi Island in Lake Malawi in the 1960s, has split into two genetically distinct populations, located at the north and south ends of the island. How can scientists determine whether these populations are now different species, according to the biological species concept? See whether the two populations are morphologically different from each other: coloring, bone structure, and so on. Determine whether captured individuals from the two different populations will mate and produce offspring in a laboratory fish tank. Determine whether individuals from one population will interbreed with individuals from the other population when introduced into each other’s native habitats. 3

Examine the fossil record in lake sediments. Cichlids in Lake Victoria are thought to have diversified from a relatively few species to 600 species in about 12,000 years (the last time the lake dried up). What is the best way to test this hypothesis? Examine the fossil record in lake sediments. Look for morphological characteristics shared among Lake Victoria species that are distinct from the species present in other lakes. Look for genetic characteristics shared among Lake Victoria species that are distinct from species present in other lakes. This is not a testable hypothesis. Answer: C A phylogenetic analysis should provide the most conclusive answer: The Lake Victoria species should form one or a few clades distinct from the clades in other African great lakes. 4

Examine the fossil record in lake sediments. Cichlids in Lake Victoria are thought to have diversified from a relatively few species to 600 species in about 12,000 years (the last time the lake dried up). What is the best way to test this hypothesis? Examine the fossil record in lake sediments. Look for morphological characteristics shared among Lake Victoria species that are distinct from the species present in other lakes. Look for genetic characteristics shared among Lake Victoria species that are distinct from species present in other lakes. This is not a testable hypothesis. 5

areas such as large plains that facilitate migration of animals In what type of environment is a scientist most likely to find examples of ongoing speciation? areas that have a large range of altitudes, such as mountains and deep valleys areas such as large plains that facilitate migration of animals extreme physical environments that are marginal for supporting life areas that are already species-rich areas that have undergone recent environmental disturbance or change Answer: E 6

areas such as large plains that facilitate migration of animals In what type of environment is a scientist most likely to find examples of ongoing speciation? areas that have a large range of altitudes, such as mountains and deep valleys areas such as large plains that facilitate migration of animals extreme physical environments that are marginal for supporting life areas that are already species-rich areas that have undergone recent environmental disturbance or change 7

behavioral isolation or mechanical isolation Sea urchins are broadcast spawners: They release their gametes into the water without courtship. Which of these reproductive isolation mechanisms is most likely affecting sea urchins? behavioral isolation or mechanical isolation gametic isolation or temporal isolation habitat isolation Answer: B 8

behavioral isolation or mechanical isolation Sea urchins are broadcast spawners: They release their gametes into the water without courtship. Which of these reproductive isolation mechanisms is most likely affecting sea urchins? behavioral isolation or mechanical isolation gametic isolation or temporal isolation habitat isolation 9

ecological/habitat isolation temporal isolation You spot a sea snake while you are in a boat on the ocean and remark about how similar it looks to a snake that lives in central Illinois. However, you know that they are most likely separate species due to which of the following reproductive barriers? behavioral isolation gametic isolation ecological/habitat isolation temporal isolation Answer: C Snakes living in the ocean are most likely never going to come into contact with snakes living in the center of a continent. 10

ecological/habitat isolation temporal isolation You spot a sea snake while you are in a boat on the ocean and remark about how similar it looks to a snake that lives in central Illinois. However, you know that they are most likely separate species due to which of the following reproductive barriers? behavioral isolation gametic isolation ecological/habitat isolation temporal isolation 11

ecological/habitat isolation temporal isolation The century cactus flowers every 100 years. A similar cactus flowers every 50 years. If the 50-year-cactus pollen has the correct characteristics to fertilize the century cactus, which reproductive barrier will most likely be working against that possibility? behavioral isolation gametic isolation ecological/habitat isolation temporal isolation Answer: D They produce flowers on different schedules. 12

ecological/habitat isolation temporal isolation The century cactus flowers every 100 years. A similar cactus flowers every 50 years. If the 50-year-cactus pollen has the correct characteristics to fertilize the century cactus, which reproductive barrier will most likely be working against that possibility? behavioral isolation gametic isolation ecological/habitat isolation temporal isolation 13

reduced hybrid fertility hybrid breakdown Several species of amphibians are able to read each other’s mating rituals and understand them, tend to be fertile at the same time, and are usually similar in size. However, when they attempt to mate, they never produce offspring. Which of the following barriers is most likely the cause of this? behavioral isolation gametic isolation reduced hybrid fertility hybrid breakdown Answer: B If they fail to create any offspring, gametic isolation would be the most likely cause. Options C and D are not correct because they refer to offspring that two separate species create. Option A is not correct because it was stated in the question that the mating rituals were working. 14

reduced hybrid fertility hybrid breakdown Several species of amphibians are able to read each other’s mating rituals and understand them, tend to be fertile at the same time, and are usually similar in size. However, when they attempt to mate, they never produce offspring. Which of the following barriers is most likely the cause of this? behavioral isolation gametic isolation reduced hybrid fertility hybrid breakdown 15

punctuated equilibrium. allopatric speciation. sympatric speciation. The fossil record shows that species remain constant for long periods of time, but then speciation episodes occur rapidly. This is indicative of gradualism. punctuated equilibrium. allopatric speciation. sympatric speciation. Answer: B Punctuated equilibrium suggests that once the process of speciation begins, it can be completed relatively rapidly. 16

punctuated equilibrium. allopatric speciation. sympatric speciation. The fossil record shows that species remain constant for long periods of time, but then speciation episodes occur rapidly. This is indicative of gradualism. punctuated equilibrium. allopatric speciation. sympatric speciation. 17

morphological species concept. ecological species concept. When differentiating between two species of fish, you notice that one species stay near the surface and feed on floating algae while the other species are bottom feeders. This is using the morphological species concept. ecological species concept. phylogenetic species concept. Answer: B This is viewing species based on their ecological niche. 18

morphological species concept. ecological species concept. When differentiating between two species of fish, you notice that one species stay near the surface and feed on floating algae while the other species are bottom feeders. This is using the morphological species concept. ecological species concept. phylogenetic species concept. 19