Ch. 14 Review Questions Defining Species1. Distinguish between microevolution andspeciation. Speciation isdifferent from microevolution in a very certain way. Microevolution is thechanging of a species gradually based on alleles in the gene pool. Speciationcompletely divides the original into two new daughter species. The alterationsare so immense that the new generation is classified as a completely differentspecies.
Speciation occurs usually with an isolation aspect of some sort. 2. Compare the definitions, advantages, anddisadvantages of the different species concepts. A species is abody of populations whose components can mate and have offspring that canreproduce.
The biological concept is advantageous because it is broad enoughthat even organisms far away from each other are considered part of the samespecies. It is deleterious because it can sometimes cause conflicts because itis solely based off reproductive success. Sometimes, scientist can’t determinethe mating process of some organisms and fossils don’t provide muchinformation. However, the morphological species concept can be used withoutsexual relations knowledge but it is very subjective and opinionated. Theecological species concept can be used based on diet instead of appearance.
Itall depends on the situation. 3. Describe five types of prezygotic barriers andthree types of postzygotic barriers that prevent populations of closely relatedspecies from interbreeding.
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Prezygoticbarriers are those that halt reproduction or fertilization through organisms. Forexample, habitats sometimes interfere with animals’ chances of ending uptogether. Some garter snakes are aquatic while some live on land. Also,temperature can be considered a barrier. Some organisms only breed duringcertain seasons and if the seasons don’t match up with their counterpart thenthey cannot mate. Mechanical issues may also pose a clash. Some flowers have tobe fertilized with a certain beak shape.
It’s like putting puzzle piecestogether. Just like humans, behavior can also cause problems. Actions andawkwardness can be a blockage to the chemistry to mate. Last but not least, onthe smaller level, gametes can be incompatible and not able to conceive anembryo. Postzygotic barriers occur after birth.
Sometimes the hybrid genes donot fully develop or function causing the organism to have a low survival rateand not make it to reproduce. Hybrids may survive, but be sterile. For example,a mule is sterile.
If a hybrid does survive and produce offspring, theoffspring might be weak and unable to reproduce. Mechanisms of Speciation4. Explain how geologic processes can fragmentpopulations and lead to speciation.
The act of geologic processesseparating species is called allopatric speciation. If a geographic barrierdevelops, it can divide a population to where on certain alleles are present incertain areas. This is more impactful on animals that are limited in mobility.For example, if fish are separated because a lake is subsidized, they cannottravel to reconnect with the rest of their population. That gene pool mustcontinue to reproduce without the alleles that were lost in the division.
Thisand environmental factors lead to the development of two or more new species. 5. Explain how reproductive barriers might evolvein isolated populations of organisms. Refer to studies of laboratory-raisedfruit flies and monkey flowers. Reproductivebarriers, like attraction and ability to mate, may evolve when organisms are incertain conditions.
For example, fruit flies were experimented on and twogroups were isolated. One group was fed maltose, while the other was fedstarch. They both started digested the substance they were fed more easily.When time to mate, they preferred a mate that grew up in the same environment. Thisis an example of a prezygotic barrier. This not only leads to evolution, but itcould also lead to speciation. Preference is a huge factor in the developmentof reproductive barriers in organisms, especially pollinators.
Flowers, wantingto be pollinated, gradually changed their shape and color to make them moresimple and desirable to pollinators. Monkey flowers practiced this and the twocolors never interbreed now. 6.
Explain how sympatric speciation can occur,noting examples in plants and animals. Sympatricspeciation can happen creating a new species even when the parent species andnew species are cohabitating an area. This can happen when a discrepancyhappens during cell division. An additional set of chromosomes creates anorganism considered polypoid. A tetraploid plant has four sets of chromosomes.Because it creates diploid daughter cells, it cannot mate with the alreadyexisting plants.
Therefore, since interbreeding is not an option, it isconsidered a new species. Every once in a while, sympatric speciation occurs inanimals. If it does, it would mostlikely be a byproduct of isolation of habitats and sexual preference.
7. Describe the circumstances that led to theadaptive radiation of the Galápagos finches. The Galapagosislands match the characteristics of a habitat that encourages adaptive radiation.It has a diverse body of organisms and the islands are far enough apart so thatisolated reproduction car occur.
After arriving to the island, the founderpopulation probably evolved from environmental driven adaptations. Reproductivebarriers contributed to the allelic difference in the now 14 different speciesof finches. The beaks altered to match the birds’ diet to the best of itsability.
8. Explain how coloration and properties of lighttransmission in water has led to speciation in Lake Victoria. Female cichlidswere more attracted to males that possessed brighter colors. This is aconsidered a reproductive barrier, and the gene is limited. This creates a newgene pool, which continues to become a new species.
The amount of lighttransmitted affects the diet of certain cichlids. Because of different diet, thesetwo species separate themselves in the interbreeding processes. 9. Explain how hybrid zones affect speciation.Describe examples of reinforcement and fusion in hybrid zones. Hybrid zonesare areas where two different species reproduce together.
Gene flow permits thehybrid zone to exist by knocking down reproductive barriers. Hybrids are born.Reinforcement is natural selection adding more physical support to theoffspring of hybrids. This is because they sometimes aren’t as fit as theirparents, so reinforcement eliminates less strong hybrids. Therefore,eliminating barriers that could cause problems when reproducing. Fusion is twospecies coming together as one. It is also known as “reverse speciation”because they are opposites.
Reproductive barriers aren’t stable and two speciesmate with each other so much, they merge into one. 10. Compare the gradual model and the punctuatedequilibrium model of evolution. Explain how each model applies to the fossilrecord. Punctuatedequilibrium is the really really long process of evolution. Speciation is allof a sudden visible in the species after a long time of little alteration. Itis a big jump in the appearance in spurts of time.
The gradual model ofevolution is like a stair case. You see a small amount of change until youreach the new species. Change is constantly happening slowly. It createsuncertainty in the fossil record because it cannot be distinguished in thestrata. Speciation has created many dramatic alterations in the fossil record.
