ch 15
section 1
1. During his travels, Darwin made numerous observations and collected evidence that led him to propose a revolutionary hypothesis about the way life changes over time.
2. Darwin observed that the characteristics of many animals and plants varies noticeably among the different islands of the Galapagos.
3. Evolution is the gradual change in an individual ovr a given amount of time, usually it takes centuries or more in order to acheive this. Evolution is concidered a theory because its a well supported testable explanation of phenomena that have occurred in the natural world.
4. A fossil is a preserve remains of ancient organisms.
5. This finding would affect his understanding of life’s diversity because it proves that all of these animals, though plentiful, and striking werenot abl to survive up to this day. So, the range in which animals differ is far less due to natural and necessary adaptations.
section 2
1. Hutton and lyell helped scientists recognize that earth is many millions of years old, and the processes that changed earth in the past are the same processes that operate the present.
2. Lamarck proposed that by selective use or disuse of organs, organisms aquired or lost certain traits during their lifetime. These traits could then be passed on to their offspring. Over amounts of time, this process led to change in species.
3. Malthus reasoned that if the human population continues to grow unchecked, sooner or later there would be insufficientliving space and not enough food for everyone. War, famine, and disease limited the growth of human populations.4. Lamarck’s views on evolution are incorrect to his lack of knowledge in how traits are inherited. He did not know that an organism’s behavior had no effect on its inheritable characteristics.
5. Malthus’s theory that if the human population continued to grow unchecked our world would be overrrun, actually applies more so to the animal and plant populations in our world. Since humans generally give birth to only 1 offspring, or 2 if they’re lucky, the amount of offspring is far less than the average animal and plant. So it is more logical to think that these animal and plant species would be the ones to overrun our world someday, but due to natural causes they cannot, thankfully.
section 3
1. In artificial selection, nature provided the super variation among different organisms, and humans, selected those super variations that they found useful.
2. Over time, natural selection results in changes in the inherited characteristics of a population. These changes increase a species’ fitness in its environment.
3. Darwin argued that living things have been evolving on Earth for millions of years. Evidence for this process could be found in the fossil record, the geographical distribution of living species, homologous structures of living organisms, and similarities in early development.
4. The struggle for existance means that members of each species compete regularly to obtain food, living space, and other necessities of life. This is based on Malsus’s work because he stated that every species picks and chooses to use, or not use the abilities it has. (i.e. birds kept trying to fly, so now they can) One of the possible reaons for doing this was because of the competition for food, living space, and etc…The need for superiority was apparent, and still is.
5. Lamarck’s theory of evolution is different from Darwin’s because he believed that prefered traits were passed onto offspring due to the parents will to achieve the preferred traits (i.e. big muscles) but Darwin thought the preferred trait was passed on because animals with those traits were more fit to survive. Although, they are similar because they both stated that in the end the best traits will override the obsolete traits.
16-1
1. There are two main sources of genetic variation: mutations and the gene shuffling that results from sexual reproduction.
2. The number of phenotypes produced for a given trait depends on how many genes control the trait.
3. A gene pool is the combined genetic information of all the members of a particular population. The gene pool controls the allele frequency because it contains all the genes of the entire population, and these genes control what alleles will be dominant or recessive in the population. So, if it is black fur versus brown fur, a majority would be heterozygus black , then homozygus brown, and the least least common would be homozygus black furred organisms.
4. In a species in which there are many variations and two separate species can be distinguished by counting the number of phenotypes produced for the given trait, and that trait depends on how many genes control the trait.
16-2
1. Natural selection on single-gene trais can lead to changes in allele frequencies and thus to evolution. Phenotypes are affected in three ways: directional selection, stabilazing selection, or disruptive selection. Directional selection occurs when ones at the end of the curve have higher fitness than ones in the middle of at the other end. Stabilizing selection takes place when individuals near the center of a curve have higher fitness than ones at either end.When ones at the upper and lower ends of the curve have higher fitness than individuals near the middle, disruptive selection takes place.
2. In small populations, ones that carry a particular allele may leave more descendants than the other ones with out it, just by chance. Over time, a series of chance occurances of this type can cause an allele to become common in a population.3. The 5 conditions are needed to maintain genetic equilibrium random mating; the population must be very large; and there can be no movement into or out of the population, no muations, and no natural selection.
4. The Hardy-Weinberg principle states that allele frequencyies in a population will remain constant unless one or more factors cause those frequencies to change.
5. Directional selection occurs when ones at the end of the curve have higher fitness than ones in the middle of at the other end. When ones at the upper and lower ends of the curve have higher fitness than individuals near the middle, disruptive selection takes place. So, they are basically just the opposite of eachother.
16-3
1. As new species eveolve, populations become reproductively isolated from eachother.
2. Speciation in the Galapagos finches occurred by founding of a new population, geographic isolation, changes in the new population’s gene pool, and reproductive isolation, and ecological competition.
3. Behavioral isolation can play a role in the evolution of a species because it is when two populations are capable of interbreeding but have differences in courtship rituals or other types of behavior. For example the eastern and western meadowlarks are similar birds whose habitats overlap in the center of the US, but since the songs each species uses to attract a mate doesn’t work on the other species, they are not attracted to eachother.
4. These two frogs are isolated by temporal isolation. Because of this isolation the two species will reproduce at different times.
