Ch 10 bio knowledge check
Analogous structures
" are structures that have similar functions and developed as a result of convergent evolution, forming from different starting materials in unrelated species. For example, the wings of insects, birds, and bats are all used for flying, but developed independently in each group of animals" Excerpt From: Jay Phelan. "What Is Life?." iBooks.
In Charles Darwin wrote: "We may look with some confidence to a secure future of great length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection." Give three reasons why he was wrong
"(a) Natural selection requires time, sometimes more time than is allowed by the rate at which changes are occurring in the environment. The world's environments are constantly changing and require continual evolutionary change if organisms are to maintain fitness. No single, perfect organism for all environments will ever evolve. (b) Because mutations occur regardless of the needs of the organism, new mutations (i.e., new alleles) may not be those required for the organism to adapt to changes may not be those required for the organism to adapt to changes in its environment. (c) More than one allele may be suitable for selection in an environment, and thus there is no single optimal adaptation"
When evolutionary biologists speak of a "molecular clock," what do they mean?
"A molecular clock is a way for biologists to determine how long two different species have been evolving separately. The longer the two species have been evolving separately, the greater are the differences in their genetic sequences. For example, humans and chimpanzees share many genes, whereas fruit flies and humans share much fewer genes. " Excerpt From: Jay Phelan. "What Is Life?." iBooks.
How did Darwin's time on the Beagle help him develop his ideas on evolution?
"Darwin found many fossils that were very similar to species still living in the same area. He also noticed that finches on the Galápagos Islands, which he assumed were all of the same species, had different physical characteristics on different islands. Biologists at the Zoological Society in London later found that there were 13 different finch species. All of these species closely resembled a single species of finch on the closest mainland, in Ecuador." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
Describe three important components to an organism's evolutionary fitness.
"Fitness is a measure of the reproductive success of individuals. (a) An organism's fitness depends on the environment in which it lives. The organism may be fit in one environment, but less fit in another environment. (b) Fitness is relative to that of other organisms in the same environment. The fitness of one individual is measured against that of other individuals with specific genotypes and phenotypes. (c) The relative fitness of an individual is measured against that of other individuals of the same species in the same population. Those individuals that reproduce more frequently than others are more fit, irrespective of the age at which they die." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
What does it mean when fixation for an allele occurs in a population?
"Fixation for an allele occurs as a result of genetic drift, when an allele frequency becomes 100% in a population. As a result, there is no genetic variation for that gene. This can be detrimental because the population may be less able to adapt to environmental changes." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
Describe one benefit of conducting research on evolution in a population of short-lived species such as fruit flies.
"Fruit flies reach maturity in about two weeks, so a scientist can include many generations during an experiment on starvation resistance. With an organism having a late age of maturity, it would require many years to complete a study such as the starvation resistance experiments" Excerpt From: Jay Phelan. "What Is Life?." iBooks.
Describe three commonly held Western beliefs about the natural world that were overturned in the 18th and 19th centuries.
"It was commonly thought that: (a) as in the Biblical account, the earth was only about 6,000 years old; (b) the earth had not changed very much over time, with the exception of the occasional earthquake, flood, or volcanic eruption; and (c) all species, including humans, were created at the same time, and species never change or die out"
How does modern medicine alter the selective pressures on birth weight in humans?
"Most babies weigh between 7 and 8 pounds at birth, as a result of stabilizing selection. Modern medicine has enabled very-low-weight, premature babies to survive, and very large babies to be delivered through Caesarean births. This has prevented selection against extremes in the size of babies born, and greater numbers of babies of extreme size (small or large) may become more prevalent in the future." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
How is biogeography useful when studying the evolutionary history of a population?
"Scientists in the field of biogeography have observed that species migrate to nearby locations and adapt to their new habitats. Different species living less than 100 miles apart and occupying drastically different habitats resemble each other more than they resemble species many thousands of miles away that occupy very similar habitats. This suggests shared common ancestors among species that are close together geographically. An example is found on the continent of Australia. Many niches in Australia that are occupied by marsupials would elsewhere be occupied by placental mammals. For example, the Tasmanian wolf, now thought to be extinct, occupied the same type of habitat as gray wolves. However, the Tasmanian wolf is much more closely related to other marsupials living in Australia than to gray wolves found thousands of miles away." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
Do recessive alleles tend to decrease in frequency in a population? Why or why not?
"The frequency of a recessive allele does not change in a population as long as the allele does not affect reproductive success. If a recessive allele does affect reproductive success, its frequency will change. Recessive alleles that adversely affect reproduction will decrease in frequency, and those that improve reproductive success will increase in frequency." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
How does the increasing frequency of antibiotic-resistant strains of bacteria represent an example of evolution in progress?
"The use of an antibiotic creates environmental pressure, and bacteria with one or more alleles imparting resistance to that antibiotic are more likely to reproduce than those that do not possess such alleles. Over time, bacteria with antibiotic-resistance alleles become more frequent in the population. Should another antibiotic be introduced, other alleles present in the population that impart resistance to that antibiotic will become more frequent over time." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
Homologous structures
"develop in related species in which the same structures are modified to perform different functions. An example is the modification of the bones making up the forelimbs of mammals. All mammals have a common ancestor, but the bones of the forelimbs have been modified for different functions, such as flying, swimming, and walking." Excerpt From: Jay Phelan. "What Is Life?." iBooks.
Mutations
- almost always random with respect to the needs of the organism. -A mutation is any change in an organism's DNA. -Most mutations are harmful or neutral for the organism in which they occur -The origin of genetic variation is mutation
What can be concluded from comparing differences in molecular biology among different species?
Genetic similarities and differences demonstrate species relatedness.
evolution
a genetic change in a population over time. A change in allele frequency in the population occurs as a result of natural selection, mutations, genetic drift, and/or migration..
Selecting for increased starvation resistance in fruit flies:
can produce populations in which the average time to death from starvation is 160 hours
Maze-running behavior in rats
is a heritable trait
Evolution:
is responsible for the increased occurrence of antibiotic-resistant bacteria.
Adaptations shaped by natural selection
may be out of date, having been shaped in the past under conditions that differed from those in the present.
gene flow
movement of alleles from one population to another
When a small group of individuals colonizes a new habitat, an evolutionary event is likely to occur, because:
small founding populations are rarely genetically representative of the initial population.
"Survival of the fittest" may be a misleading phrase to describe the process of evolution by natural selection, because:
survival matters less to natural selection than does reproductive success.
In a population in which a trait is exposed to stabilizing selection:
the average value for the trait stays approximately the same, and the variation for the trait decreases.
