Learning Materials
Features
Discover
Chapter 18: Problem 21
In a hybrid zone, in addition to interacting, what else do two closely related species do? a. compete b. reproduce c. transition d. fuse
Over 30 million students worldwide already upgrade their learning with 91影视!
These are the key concepts you need to understand to accurately answer the question.
All the tools & learning materials you need for study success - in one app.
Get started for free
There are years of drought in a small, relatively isolated community. During the drought, small seeds with thin shells become rare. Large seeds with hard cases become increasingly common. The large, tough seeds are successfully eaten by birds with large and broad beaks. Assuming that the drought continues and the population of birds in the community stays isolated, what predictions for the population can you make under the influence of natural selection? a. The birds with small, thin beaks will grow larger, broader beaks to be able to eat the larger seeds. This will result in subsequent generations having a higher percentage of birds with large, broad beaks. b. There will be more birds with small, thin beaks dying and more birds with large, broad beaks surviving. Differential reproduction of birds with large, broad beaks will result in subsequent generations having a higher percentage of birds with large, broad beaks. c. The species will diverge into two species, one with small, thin beaks and one with large, broad beaks. The two species will then compete for resources. d. There will be neither phenotypic nor genotypic changes in the population.
Genes important in the embryonic development of animals have been relatively well conserved during evolution. This means they are more similar among different species than many other genes. What explains this genetic conservation across animal species? a. Changes in the genes that are important to embryonic development have been relatively minor because there are no selective pressures on an individual before it is born b. Changes in the genes that are important to embryonic development have been relatively minor because not much time has elapsed since the divergence of the various animal taxa. c. Changes in the genes that are important to embryonic development have been relatively minor because early embryos are very fragile and even small mutations can result in death d. Changes in the genes that are important to embryonic development have been relatively minor because mutational tweaking in the embryo has magnified consequences in the adult.
Mutations in the glucose 6-phosphate dehydrogenase (G6PD) gene can cause a rare anemia when inherited. However, homozygotes with this mutation are less prone to malaria infection, a disease that historically was the most widespread deadly disease among humans. Predict how this mutation would affect the fitness of individuals living in countries where malaria is endemic.
Describe how an adaptation, such as better running speed, relates to natural selection. a. Natural selection produces beneficial adaptations, such as better running speed, in individuals that run more frequently b. Natural selection randomly mutates individuals鈥� genetic code until it produces beneficial adaptations, such as better running speed c. Natural selection produces adaptations, such as better running speed, to help individuals survive and reproduce d. Natural selection reproduces individuals with favorable genetic traits-such as the adaptation of better running speed-over time.
In 1952, the Miller-Urey experiment showed that an electrical discharge in a gas-phase mixture of ammonia, hydrogen, methane, and water produced five amino acids. When the experiment was conducted, evidence indicated that this mixture was representative of the Hadean (early Earth) atmosphere. The experiment was repeated in the presence of jets of hot steam, simulating Hadean volcanic eruptions and producing an even larger variety of amino acids. A. Consider the following criticisms of the 鈥渙rganic soup鈥� model and justify the selection of data that other experiments might provide regarding the origin of life on Earth. 鈥� Biopolymers on Earth have a left-hand symmetry at the carbon adjacent to the carboxylic acid carbon, and these experiments produced mixtures of both leftand right-hand symmetries. 鈥� No peptide bonds between amino acids were mobserved. 鈥� Early Earth鈥檚 atmospheric oxygen concentration is known to have been very low, implying the absence of an ozone layer to filter high-energy ultraviolet (uv) radiation. 鈥� Ammonia decomposes when it absorbs high-energy uv radiation, but diatomic nitrogen does not. Models of the abiotic synthesis of biomolecules suffer from a 鈥渃hicken and egg鈥� dilemma. Proteins are needed to synthesize DNA and RNA, and DNA and RNA are needed to synthesize proteins. Which molecules came first? B. In light of the following observations, evaluate the hypothesis that nucleotides arose from a prebiotic mixture. 鈥� Nuclei acids are not found in experiments like those of Miller and Urey. 鈥� Purines and pyrimidines decompose at high temperature, and Earth was bombarded by meteors and comets during the Hadean eon. 鈥� Bonds in the purine and pyrimidine rings of nucleic acids are broken by high-energy uv radiation. 鈥� Carl Sagan and colleagues synthesized ATP from a mixture of adenosine, ribose, and phosphate when exposed to uv radiation. 鈥� Ribose has never been synthesized in experiments like those conducted by Miller and Urey. 鈥� Ribose has a left/right symmetry, and the righthanded form occurs in Earth organisms. Continuing with the analogy, if neither the chicken nor the egg came first, then both must have arisen together. Some regard simultaneous innovations in both catalysis and information storage and retrieval as too improbable. In samples of meteorites, both amino acids and nucleic acids have been found. The amino acids are mixtures of left- and right-handed symmetries, although some have shown a significant bias toward the left-handed form (J. Elisa et al., ACS Central Science, 2016). The arrival from space of the seeds of biomolecules is called panspermia. Carl Sagan (1966) and Francis Crick (1973), one of the first to describe the structure of DNA, regarded panspermia as the only plausible origin of life on Earth. In fact, their belief was in directed panspermia, the intentional seeding by intelligent aliens. C. Describe the questions that must be addressed for panspermia to be a scientific hypothesis about the origin of life on Earth and describe the reasons for the directed panspermia revision of this hypothesis. To avoid the conflicting chicken-and-egg claims that 鈥減rotein catalyst was first鈥� and 鈥淒NA information storage was first,鈥� two alternatives have emerged regarding the origin of life on Earth. Consider two simple ideas: 1) water blocks uv radiation, and cracks in the ocean floor (hot vents) provide a temperature difference that generates a source of entropy; and 2) ribosomes are composed of RNA. D. Describe one of the following as a hypothesis concerning the origin of life on Earth: 鈥� Reactions among molecules in the vicinity of hot vents became organized in space and time, eventually developing structures that foreshadow the proton gradient upon which metabolism is based. This alternative is the basis for what is referred to as the metabolism-first hypothesis. 鈥� The catalytic properties of the ribosome reflect the self-catalytic polymerization of nucleotides with sequential structures conserved in modern DNA, the catalytic properties conserved in proteins, and the catalytic properties of the ribosome whose core structure is RNA. This alternative is the basis for what is referred to as the RNA-first hypothesis.
What do you think about this solution?
We value your feedback to improve our textbook solutions.
Explanations 
Textbooks 
Flashcards 
91影视 AI 
Notes 
Study Plans 
Study Sets 
Find a degree 
Magazine