Descent with Modification
CHAPTER 22
DESCENT WITH MODIFICATION:
A DARWINIAN VIEW OF LIFE
State the two major points Darwin made in The Origin of Species concerning the Earth's biota.
Darwin’s view of life contrasted sharply with the accepted viewpoint: the Earth was only a few thousand years old and was populated by unchanging life forms made by the Creator during a single week. Thus, On the Origin of Species, not only challenged prevailing scientific views, but also challenged the roots of Western culture. The two major points were that 1. species evolved from ancestral species and were not specially created and 2. that Natural selection is a mechanism that could result in this evolutionary change.
Describe Carolus Linnaeus' contribution to Darwin's theory of evolution.
Known as the father of taxonomy, the naming and classifying of organisms, he developed a system of binomial nomenclature still used today. The clustering of species in taxonomic groups did not imply evolutionary relationships to Linnaeus, but id did to other scientists.
Describe Jean Baptiste Lamarck's model for how adaptations evolve.
Lemarck believed that evolution was driven by an innate tendency toward increasing complexity, which he equated with perfection. As organisms attained perfection, they became better and better adapted to their environments. Thus, Lamark believed that evolution responded to organisms’ felt needs.
Explain what evidence convinced Darwin that species change over time.
Darwin perceived the origin of new species and adaptation as closely related processes; new species could arise from an ancestral population by gradually accumulating adaptations to a different environment. For example, two populations of species could be isolated in different environments as each adapted to local conditions.
Explain why variation was so important to Darwin's theory.
Variation was important to Darwin’s theory because without it, natural selection would not be possible.
Define and state the basic principles in natural selection.
Natural selection is this differential success in reproduction, and its product is adaptation of organisms to their environment. Natural selection occurs from the interaction between the environment and the inherent variability in a population. Variations in a population arise by chance, but natural selection is not a chance phenomenon, since environmental factors set definite criteria for reproductive success.
Using some contemporary examples, explain how natural selection results in evolutionary change.
Natural selection allows for more frequency of the genes needed by the individual to survive. Thus, since the genes change and there is a preference over which ones to get, evolutionary change occurs.
Describe how molecular biology can be used to study the evolutionary relationships among organisms.
An organism’s hereditary background is reflected in its genes and their protein products. Thus, two species considered to be closely related by other criteria should have a greater proportion of their DNA and proteins in common than more distantly related species.
Explain the problem with the statement that Darwinism is "just a theory".
Darwinism is no longer a theory because it has been proven countless times by fossil records and fields of biology such biogeography, comparative anatomy and molecular biology.
Explain the problem with the statement that Darwinism is "just a theory".
Darwinism is no longer a theory because it has been proven countless times by fossil records and fields of biology such biogeography, comparative anatomy and molecular biology.
CHAPTER 23
THE EVOLUTION OF POPULATIONS
Explain what is meant by the "modern synthesis".
Modern synthesis is the focus on populations as units of evolution
Explain how microevolutionary change can affect a gene pool.
Microevolutionary change affects a gene pool by changing allele or genotype frequencies in an existing population.
In their own words, state the Hardy-Weinberg theorem.
The Hardy Weinberg theorem basically states that if a population is large, shows no random mating, is totally isolated, shows no net mutations, and has reproductive success for all individuals then no evolution will occur.
Describe the usefulness of the Hardy-Weinberg model to population geneticists.
This model would help these geneticists realize the gradual change of a certain population over time because of little or no change in allele and genotype frequencies.
Explain how genetic drift, gene flow, mutation, nonrandom mating and natural selection can cause microevolution
Each of these examples causes mircoevolution because they all affect the allele frequencies of a population. They introduce a change in alleles or genotypes.
Distinguish between the bottleneck effect and the founder effect.
The bottleneck effect describes a population that undergoes a dramatic decrease in size. The founder effect describes allele frequencies in a migrating group differ, by chance, from their population of origin.
Explain why mutation has little quantitative effect on a large population.
Mutation is not harmful and has no effect in most cases, it is also adaptive. Mutation is always on a small scale so it could never have a lasting effect on a large population.
Give the cause of nearly all genetic variation in a population.
Genetic variation is caused by genetic drift, non random mating, natural selection, mutation and gene flow.
Explain how genetic variation is preserved in a natural population.
Genetic variation is preserved through diploidy (presence of two copies of each chromosome) and polymorphism (heterozygous advantage and frequency dependent selection).
Describe what selection acts on and what factors contribute to the overall fitness of a genotype.
Acting on phenotypes, selection indirectly adapts a population to its environment by increasing or maintaining favorable genotypes in the gene pool. The overall fitness of a genotype depends on whether its positive effects outweigh any harmful effects it may have on the survival and reproductive success of the organism.
Distinguish among stabilizing selection, directional selection and diversifying selection.
Stabilizing selection acts against extreme phenotypes and favors the more common intermediate variants. Directional selection shifts the frequency curve for variations in some phenotypic character in one direction or the other by favoring what are initially relatively rare individual the deviate from the average for that character. Diversifying selection occurs when environmental conditions are varied in a way that favors individual in both extremes of a phenotypic range over intermediate phenotypes.
Give at least four reasons why natural selection cannot breed perfect organisms.
*Organisms are locked into historical constraints.
*Adaptations are often compromises.
*Not all evolution is adaptive.
*Selection can only edit variations that exist.
CHAPTER 2 4
THE ORIGIN OF SPECIES
Define biological species (E. Mayr).
Biological species is a population or group of populations whose members have the potential to interbreed.
Describe some limitations of the biological species concept.
Some limitations of the biological species concept are that the criterion of interbreeding is useless for organisms that are completely asexual in their reproduction; it is also inadequate as a criterion for grouping extinct forms of life, and if two populations are geographically segregated from each other, they do not interbreed, although they may be so much alike that they are placed in the same species on morphological grounds.
Distinguish between prezygotic and postzygotic isolating mechanisms.
Prezygotic barrier is a reproductive barrier that impedes mating between species or hinders fertilization of ova if interspecific mating is a hempted. Postzygotic barrier is any of several species-isolating mechanisms that prevents hybrids produced by two different species from developing into viable, fertile adults.
Describe five prezygotic isolating mechanisms and give an example of each.
There are five different types of prezygotic isolating mechanisms.
Habitat Isolation is when two species that live in different habitats within the same area encounter each other rarely, for example, two species of parasites living on different hosts will not have a chance to mate.
Behavioral Isolation is that special signal that attracts mates, as well as elaborate behavior unique to a species like male fireflies of different species signal to females of their kind by blinking their lights in particular patterns.
Temporal Isolation is when two species that breed during different times of the day, different seasons, or different years cannot mix their gametes.
Mechanical Isolation, is when closely related species may attempt to mate, but fail to consummate the act because they are anatomically incompatible.
Gametic Isolation is when even if the gametes of different species meet, they rarely fuse to form a zygote. Gamete recognition may be based on the presence of specific molecules on the coats around the egg, which adhere only to complementary molecules on sperm of the same species.
Distinguish between allopatric and sympatric speciation.
Allopatric speciation is a mode of speciation induced when a geographical barrier segregates the ancesteral population.
Sympatric speciation is a mode of speciation occurring because of a radical change in the genome that produces a reproductively isolated subpopulation in the midst of its parent population.
Describe the adaptive radiation model and use it to describe how it might be possible to have many sympatric closely related species even if geographic isolation is necessary for them to evolve.
1. One island in this cluster of three is seeded by a small colony founded by individuals of species A, blown over from a mainland population.
2. Its gene pool isolated from the parent species, the island population evolves into species B as it adapts to its new environment.
3. Storms or other agents of dispersion spread species B to a second island,
4. where the isolated colony evolves into species C.
5. Later, individuals from species C recolonize the first island and cohabit with species B, but reproductive barriers keep the species distinct.
6. A colony of species C may also populate a third island,
7. where it adapts and forms species D.
8. Species D is dispersed to the two islands of its ancestors,
9. forming a new species, E, on one of those islands.
The story could go on, with a series of allopatric speciation episodes made possible by the combination of isolation and occasional dispersal.
Define sympatric speciation and explain how polyploidy can cause reproductive isolation.
Sympatric speciation is a mode of speciation occurring because of a radical change in the genome that produces a reproductively isolated subpopulation in the midst of its parent population. Polyploidy can cause reproductive isolation because it causes extra sets of chromosomes, which then can leave the offspring sterile since no other organism would be able to match up correctly because of unpaired chromosomes.
List some points of agreement and disagreement between the two schools of thought about the tempo of speciation (gradualism vs. punctuated equilibrium).
One view of speciation is that it usually occurs gradually by an accumulation of micro evolutionary changes in gene pools. In contrast, the punctuated equilibrium model views species as changing most when they bud from an ancestral species and then undergoing relatively little change for the rest of their existence.
CHAPTER 26
EARLY EARTH AND
THE ORIGIN OF LIFE
Provide evidence to support the hypothesis that chemical evolution resulting in life's origin occurred in 4 stages:
a. Abiotic synthesis of organic monomers: Through conducting many experiments, now we know that the atmosphere of early Earth probably included CO, CO2, and N2, and was less reducing than the Miller-Urey model, and thus, less favorable to formation of organic compounds.
b. Abiotic synthesis of polymers: abiotic synthesis and accumulation of monomers, or small organic molecules, that are the building blocks for more complex molecules.
c. Formation of protobionts: they maintain and internal chemical environment different from their surroundings and exhibit some of the properties associated with life.
d. Origin of genetic information: makes it possible for molecular aggregates to pass along not just samples of key molecules but also instructions for making more of those molecules.
Describe Whittaker's five-kingdom system.
The five-kingdom system recognizes the two fundamentally different types of cell, prokaryotic and eukaryotic, and sets the prokaryotes apart from all eukaryotes by placing them in their own kingdom, Monera. The prokaryotes are bacteria. Organisms of the other four kingdoms all consist of cells organized on the eukaryotic plan.
The kingdoms Plantae, Fungi, and Animalia are multicellular eukaryotes, each kingdom defined by characteristics of structure and life cycle.
Describe three alternatives to the five-kingdom system and explain the rationale for each.
*The six-kingdom system divides the prokaryotes into two kingdoms based on molecular evidence for an early evolutionary divergence.
*The three-domain system assigns even more significance to the ancient evolutionary split between eubacteria and archaebacterial by using a super kingdom called the domain.
*The eight-kingdom system splits the protists into three kingdoms.