Unit 7; Natural Selection
What are the five conditions that must be met for a population to be in Hardy-Weinberg equilibrium?
-no mutations -random mating -no natural selection -extremely large population size -no gene flow
In what ways is evolution supported (i.e., what are some evidence of evolution?
-the fossil records. -comparative morphology -biogeography
White fur color (w) is recessive to black fur color (W)in mice. 22 mice have a white coat in a population of 200. Knowing this, calculate the frequency of the r allele.
22/200 = 0.110.11 + p = 1 where .89 = p0.11 ^ 2 = frequency
When did early Earth form?
4.6 billion years ago
Mutation
A change in a gene or chromosome.
genetic drift
A change in the gene pool of a population due to chance
Population
A group of individuals that belong to the same species and live in the same area
natural selection
A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits.
Adaptation
A trait that helps an organism survive and reproduce
fitness
Ability of an organism to survive and reproduce in its environment
biotic factors
All the living organisms that inhabit an environment
Phenotype
An organism's physical appearance, or visible traits.
How does ecological stress affect the rate of extinction?
Anytime there is ecological stress,exctinction rates can quicken.
Does the fossil record provide a complete picture of life in the past? Why or why not?
Because not all organisms leave a trace behind when they die, the fossil record is not complete. While the picture of the past is incomplete, the fossil record shows how fossils were organized to provide evidence about the history of life on Earth, including how organisms have changed over time.
In general, how are prezygotic and postzygotic barriers similar? In general, how are they different?
Both types maintain isolation and prevent gene flow between the populations Prezygotic-prevent mating or hinder fertilization Postzygotic-prevent a hybrid zygote from developing into a viable fertile adult
Evolution
Change in a kind of organism over time; process by which modern organisms have descended from ancient organisms.
can an organism's physical environment influence evolutionary change? why or why not?
Changing environmental conditions influence which organisms survive and reproduce, which, in turn, can lead to evolutionary changes in populations.
gene pool
Combined genetic information of all the members of a particular population
From the evidences you listed in question #1, which would give scientists the most accurate information?
DNA
Why might analyzing DNA sequences be more accurate than analyzing amino acid sequences when creating a phylogenetic tree?
DNA yields more phylogenetic information than protein, the nucleotide sequences of a pair of homologous genes having a higher information content than the amino acid sequences of the corresponding proteins, because mutations that result in non-synonymous changes alter the DNA sequence but do not affect the amino acid sequence.
Describe the Miller Urey experiment.
Demonstrated that energy from lighting might have helped create Earth's first organic molecules.
What is the earliest known fossil?
Earliest fossil evidence is 3.5 bya, cyanobacteria.
True or false: natural selection acts on genotype.
False
directional selection
Form of natural selection in which the entire curve moves; occurs when individuals at one end of a distribution curve have higher fitness than individuals in the middle or at the other end of the curve
What evidence supports your explanation to problem #1?
Fossil data, biogeography and morphology
List at least 3 items, or pieces of "evidence" that can be used to create a cladogram/phylogenetic tree
Fossil records, DNA, proteins, homologues structures
How did artificial selection influence Darwin's thinking?
From artificial selection, Darwin knew that some offspring have chance variations that can be inherited. In nature, offspring with certain variations might be more likely to survive the "struggle for existence" and reproduce. If so, they would pass their favorable variations to their offspring.
Why might species that live in different geographical areas sometimes resemble each other?
Gene flow: the transfer of alleles between populations. Members of a species often resemble each other because their populations are connected by gene flow
bottleneck effect
Genetic drift resulting from the reduction of a population, typically by a natural disaster, such that the surviving population is no longer genetically representative of the original population.
founder effect
Genetic drift that occurs when a few individuals become isolated from a larger population and form a new population whose gene pool composition is not reflective of that of the original population.
What is the difference between genotype frequencies and phenotype frequencies in a population?
Genotype frequencies refer to how alleles combine. Allele frequencies refer to an alleles relative distribution in the population
How do homologous structures differ from analogous structures?
Homologues structures- characteristics that are similar in 2 species because they share a common ancestor. Analogous structures-structures that are similar but have separate evolutionary origins
How can the principle of parsimony be applied to phylogenetics?
If there are conflicts among characters use the principle of parsimony and you use the hypothesis that requires the fewest assumptions
How can natural selection promote reproductive isolation in allopatric and sympatric speciation?
In allopatric speciation, groups become reproductively isolated and diverge due to a geographical barrier. In sympatric speciation, reproductive isolation and divergence occur without geographical barriers.
What does the phrase "non-selective pressures" mean?
In the bottle neck effect floods,famine,fires,huricanes,hunting
Research the bottleneck effect on cheetahs. A. What has happened to their population? b. How has this affected their genetic diversity? c. If a new disease were to be introduced into the cheetah population, what effect could it have? Why? Be specific.
In this bottleneck the cheetahs of North America and Europe went extinct, leaving extant only the species' Asian and African populations b. As large mammals died out across the world, the number of surviving cheetahs dwindled, which caused extreme inbreeding. c. The cheetah species is more likely to become extinct because alleles would begin to die out allowing few to survive.
Why is genetic variation important to survival?
It allows natural selection to increase or decrease frequency of alleles already in the population; enables some individuals to adapt to the environment while maintaining the survival of the population.
What is the purpose of calculating Hardy-Weinberg equilibrium?
It determines what the genetic makeup of the population would be if it were not evolving. This is then compared to actual data. If there are NO differences, then the population is not evolving. If there are differences, then the population may be evolving.
Why is evolution a theory?
It is not 100% proven or complete but scientists argue on how it happened
What factors contribute to phenotypic variation in a population?
Mutations, genetic drift, migration/gene flow, natural selection
How does artificial selection differ from natural selection?
Natural selection is any selection process that occurs as a result of an organism's ability to adapt to its surroundings. Artificial selection, on the other hand, is selective breeding that is imposed by an external entity, usually humans, in order to enhance the frequency of desirable features.
stabilizing selection
Natural selection that favors intermediate variants by acting against extreme phenotypes
How is it possible for two species that look similar, to be less related than two species who look completely different?
Nature selects the traits that give an organism an advantage over others. These traits are found in many other organisms. What they evolved from differs, but their mutations remain the same/similar.
abiotic factors
Nonliving components of environment.
What is the main difference between phylogenetic trees and cladograms?
Phylogenetic trees diagrams that represent the evolutionary history of a group of organisms. Similar to cladograms except trees show the amount of change over time measured by fossil
Explain how evolution is an ongoing process in all living organisms?
Populations continue to evolve genomes change.
Research an example of natural selection and identify the selective pressure.
Predation, competition and disease are examples of selection pressures.
How does the RNA World Hypothesis help to explain a pre-cellular stage of life?
Proposes that RNA could have been the earliest genetic material, helps explain the pre-cellular stage of life
What evidence supports the endosymbiotic theory? Think back to Unit 2
Single stranded, circular DNA is found exclusively in prokaryotes. This evidence supports the endosymbiosis theory because these characteristics would allow the mitochondria and chloroplasts to survive on their own.
Biogeography
Study of past and present distribution of organisms
. Due to the over prescription of antibiotics, many strains of bacteria are developing resistance. Can this resistance evolve (i.e., can the level of resistance change over time)? Provide an explanation for your reasoning.
That means the germs are not killed and continue to grow. Resistant infections can be difficult, and sometimes impossible, to treat.
When comparing DNA sequences of two closely related species what would you expect to find? What about between two distantly related species?
The DNA of two closely related organisms should be expected to be similar. As time passes and organisms become more distant, there has been more time for mutations to occur.
How does the idea of descent with modification explain the unity and diversity of life?
The descent with modification observes that living organisms are closely related and have large differences due to their modification from a common ancestor, resulting in the diversity of life.
How does species diversity correlate to the survival of the species?
The more genetic diversity in a population the better it can respond to changes in the environment.
If a species goes extinct, it opens up a new niche. How can this potentially lead to speciation of another species?
The niche can then be exploited by a different species
How is sexual selection similar to directional selection?
The response to sexual selection will depend on genetic variation in trait expression, more precisely on how much genetic variation there is in the direction of selection. The less the genetic variation aligns with the direction of sexual selection, the higher the genetic constraints for trait evolution
What are "emergent diseases"? How do they come about?
The spread of existing infections and the emergence of new ones in many areas of the world can be caused by poor sanitary conditions, hygiene and a lack of clean drinking water.
True or False: organism can adapt to their environments if they try to
True
True or false: mutations can lead to new alleles.
True
What are some vestigial structures in humans? Describe what they structures/features may have been useful for in the past. You may use the internet to research this
Vestigial structure are structures that are conserved even though they no longer have a use like tailbone and appendix, No one knows the original function of the appendix, but Charles Darwin proposed that it once was used by primates to digest leaves. Now the appendix in humans seems to be a depository for good bacteria used in the colon to aid digestion and absorption, though surgical removal of the appendix causes no observable health problems. It is believed that human ancestors once had tails and lived in trees, and the coccyx would be where the tail was attached to the skeleton.
Fill in the blank: Nodes represent _____.
common ancestors
organism of the same species with different genotypes will always have different have different phenotypes? do you agree? why or why not?
different genotypes can lead to the same phenotype. This happens because genes have different alleles.
descent with modification
each living species has descended, with changes, from other species over time
selective pressure
environmental conditions that select for certain characteristics of individuals and select against other characteristics.
disruptive selection
favors individuals at both extremes of the phenotypic range
What does it mean if a trait is "highly conserved"?
gene that has essentially remained unchanged throughout evolution.
gene flow
movement of alleles from one population to another
natural selection only does what is best for the species. do you agree with this statement or not?
natural selection has no foresight or intentions. it simply selects among individuals in a population, favoring traits that enable individuals to survive and reproduce, yielding more copies of those individuals' genes in the next generation.
Is the Hardy-Weinberg model realistic?
no, it is a theoretical model that is used in comparison to actual data to determine whether a population is undergoing evolution.
Think back to unit 6, where are genes that code for antibiotic resistance found in bacteria?
plasmids are small DNA circles outside the bacterial chromosome. Several antibiotic resistance genes can be present on the same plasmid.
The frequency of individuals who express a recessive disease in a population is 5%. What variable in the Hardy Weinberg equations does the 5% refer to? Why?
q2 because it's recessive.
fixed
refers to an allele for which all members of a population are homozygous
Evolutionary fitness is measured by _______________________
reproductive success
How is our general understanding of the phrase "survival of the fittest" misleading?
survival is only one aspect of selection, and not always the most important.
If an organism has a more favorable trait, then it will be more likely to ___________ and _______________
survive and reproduce.
Many scientists agree that we are currently in the sixth mass extinction. How does this mass extinction differ from those that occurred in the past?
the sixth mass extinction is driven by human activity, primarily (though not limited to) the unsustainable use of land, water and energy use, and climate change.
competition
the struggle between organisms to survive in a habitat with limited resources
True or False: a species can diverge while living in the same geographical area
true
sexual selection
when individuals select mates based on heritable traits
