Evolution, Ecology and Animal Behavior - Biology
A student observes a population of 100 eagles in Hardy-Weinberg equilibrium. The eagle's allele for a pointed beak is dominant, and the allele for a rounded beak is homozygous recessive. If 9 eagles were found to have a rounded beak in the population, what is the allele frequency of the pointed beak?
0.70 The equation for the Hardy-Weinberg equilibrium is: p2 + 2pq + q2 = 1. We also know that p + q = 1, where p (pointed beak) and q (rounded beak) are the dominant allele and recessive allele frequencies, respectively. p2 = homozygous dominant (pointed beaks) 2pq = hybrids (pointed beaks) q2 = homozygous recessive (rounded beaks) 9 eagles display rounded beaks, which means they are homozygous recessive for the allele. q2 gives us the number for the homozygous recessive individuals, so if 9% of the population is recessive, then we know that: 0.09 = q2; q = 0.30. Thus, according to p + q = 1, the frequency of the dominant allele must be p = 1 - 0.30 = 0.70.
A population of fish is in Hardy-Weinberg equilibrium. Red-colored scales are a dominant trait and blue-colored scales are a recessive trait. In the population, 36% of the fish display red-colored scales. What percent of the population in the next generation is expected to be homozygous dominant?
4% The Hardy-Weinberg equation is p + q = 1, and p2 + 2pq + q2 = 1, where: p2 = homozygous dominant 2pq = heterozygous q2 = homozygous recessive The general strategy for all Hardy-Weinberg problems is that we have to find the individual values of p and q, and then use those values to solve for what the question is asking. We're given that 36% of the population shows a dominant phenotype, and this number includes both homozygous dominant and heterozygous dominant phenotypes. If 36% show the dominant phenotype, then 64% of the population shows the recessive phenotype. In accordance to the above equations: q2 = 0.64 q = 0.80 p = 0.20 p2 = (0.20)2 = 0.04 X 100 = 4%
A population of sheep is in Hardy-Weinberg equilibrium. The trait for black wool is dominant, and the trait for white wool is recessive. Out of 100 sheep, 84 were found to have black wool. How many sheep are heterozygous?
48 The Hardy-Weinberg equation is p+q=1, and p2 + 2pq + q2 = 1, where: p2 = frequency of homozygous dominant 2pq = frequency of heterozygous q2 = frequency of homozygous recessive p = allele frequency for the dominant form q = allele frequency for the recessive form The general strategy for all Hardy-Weinberg problems is to find the individual values of p and q, and then use those values to solve for what the question is asking. If 84 sheep display the dominant trait (black wool), then we know 16 sheep (or 16% of the population) must show the recessive trait (white wool). These 16 sheep must be homozygous recessive, or represent q2 in our equation (NOTE: They do not represent only q, the allele frequency. We have to calculate for q since the allele frequency was not given to us, only the frequency of homozygous recessives was given). The gene frequency for the recessive trait is q2 = 0.16, so q = 0.40. We can then see that p = 0.60 using p+q=1. To find the amount of heterozygotes we use: 2pq = (2)(0.40)(0.60) = 0.48 x 100 sheep = 48 sheep.
Which female shows a higher rate of fitness within her population?
A female who has 3 offspring and they all live. Fitness is best defined as an organism's ability to reproduce and pass on inherited traits to their offspring. Heritability is not significant for the female who has no offspring. The female [B] has 100% viability for her offspring and has the most amount of surviving offspring out of all the other choices, making her the most fit.
Which of the following are best characterized by brackish water? A. A river emptying into an inland lake. B. A mangrove leading to an estuary. C. A stream in a tropical forest. D. A freshwater marsh and lake. E. Seawater washing onto a beach.
A mangrove leading to an estuary. Brackish water means a mix between salt and fresh water, which would be found in an estuary. An estuary is a specific area where freshwater meets seawater. A mangrove swamp often grows near an estuary and is characterized by a mix of salt and freshwater. Some marshes can be brackish, but D specifically stated that this marsh was freshwater, and thus not characterized by brackish water.
A species of desert plant secretes a chemical into the surrounding soil that kills seeds from any other species of plant that attempts to germinate in that area. What is this an example of?
Allelopathy Allelopathy is type of interference competition, where the establishment of other individuals who would compete for a mutual resource is prevented, in this case using a toxic chemical. Intraspecific competition (E) occurs when competition occurs within the same species; in this case the plant is competing with all the other species of plants in the area.
A population of lions becomes separated by a river. Which process may eventually diverge them into separate species?
Allopatric speciation Allopatric speciation is when a geographic barrier, such as a river, separates a population. Sympatric speciation is when a population forms a new species without a geographic barrier; this can proceed via hybridization, polyploidy, or balanced polymorphism. Disruptive selection is a process where extreme values for a trait are favored over intermediate values, and often contributes to sympatric speciation. Adaptive radiation is the rapid diversification of new organisms, often due to a change in the environment and new available resources.
A scientist thinks she has discovered a new species of beetle. Which of the following would help determine if the beetle is a new species or not? A. Compare proteins from the beetle's eggs to other known species B. Compare physical differences between the new beetle and known beetles C. Sequence the DNA of the new beetle D. Attempt to breed the beetle with other known beetles E. Compare the beetle's behavioral patterns
Attempt to breed the beetle with other known beetles The hallmark of a new species is the inability to interbreed. If the beetle can breed with other known beetles, then it is not a new species. However, if it is unable to interbreed, then this would be a new species of beetle. Sequencing the DNA could find some similarities, but ultimately this does not define a new species. Physical differences between individuals can vary vastly inside a group of species, so this is not a useful way to distinguish between different species.
All of the following are assumptions in Hardy-Weinberg equilibrium EXCEPT for one. Which one is the EXCEPTION? A. No mutations B. Equal inflow and outflow of individuals C. Random mating D. No random increases or decreases of alleles. E. Sufficiently large population
Equal inflow and outflow of individuals To remember the requirements for Hardy-Weinberg equilibrium, use the mnemonic "Large Random M&M". Large populations to minimize the effects of genetic drift. Genetic drift is the random increase or decrease of allele frequencies. A special type of genetic drift is the "founder effect", which occurs when a group of emigrating individuals do not reflect the allele frequencies of the original population. Random mating. Individuals do not seek a particular type of individual to mate with, for example they do not mate only with nearby individuals or express sexual selection. No Mutation: There cannot be any mutations to introduce new allels in the population. No Natural selection: The environment is not impacting the allele frequencies, and all traits are neutral. No Migration: This can also be written as no gene flow. The population must be isolated. This is why [B] is wrong, no amount of gene flow into or out of the population can occur.
An earthworm will retreat when prodded with a stick, but after a few prods it will begin to ignore the stimulus and no longer retreat when prodded. What type of learning occurred?
Habituation Habituation allows animals to distinguish between useful and meaningless stimuli. After several non-threatening prods, the worm will assume the stimuli will not harm it and can be ignored. Imprinting occurs when a specific behavior is acquired due to a specific stimulus during a critical period. An example is a young gosling adopting a shoe as its mother, because it is the first visual stimuli it sees upon birth. This behavior is irreversible, and the gosling will even reject its real mother once the critical period passes. Associative learning occurs when an individual associates a stimulus with a specific response. A classic example is when a dog salivates at the sound of the bell, because it has learned to associate the sound of a bell with food. Observational learning occurs when an individual copies the behavior of another individual without any reinforcement of the behavior. An example is when one monkey discovers she can easily wash away the sand on a potato if she holds it in water. Soon after, all of the monkeys began washing their potatoes in the water. Insight occurs when an animal performs a behavior that leads to a desirable outcome, despite having no previous experience. For example, a chimpanzee will learn on her own to stack boxes to reach a banana on the ceiling.
An insect moves randomly at different speeds depending if it is in a favorable environment or not. Which of the following describe this insect's movement pattern?
Kinesis Animals typically have three types of movement. The first is kinesis, where the animal will move in a random direction. The animal will slow down if it is in a favorable environment and speed up if it is in an unfavorable environment. This way, the animal will spend more time in a favorable environment. Taxis is when an animal moves in a specific direction after receiving a stimulus. The animal can move either towards or away from the stimulus. A type of taxis is phototaxis, which is exemplified by flies being attracted towards lightbulbs at night. Migration is the long distance movement of animals based on the season. Birds will often migrate from the north towards the south to avoid cold winters with a lack of resources.
Fungi often grow alongside plant roots and receive some products of photosynthesis. In return, the fungus grows to retrieve nutrients from the soil and returns them to the plant. This is an example of:
Mutualism This is an example of mutualism because both the fungus and the plant benefit. The fungus gets products of photosynthesis so it does not need to find an energy source, and the plant gets necessary nutrients such as phosphorous and nitrogen. This is called a mycorrhizal interaction and is extremely important for the majority of plants today.
Which of the following statements is true about evolution? A. Individuals evolve in response to environmental pressures. B. Natural selection will choose the strongest individual. C. Natural selection is a random process. D. Natural selection will always progress in one direction. E. Natural selection occurs when individuals must compete to survive.
Natural selection occurs when individuals must compete to survive. Evolution refers to the changes in populations or groups of species. More specifically, evolution refers to the changes in allele frequencies in populations over time. Natural selection is the gradual, non-random process where alleles become more or less common as a result of the individuals interactions with the environment. Given limited resources, some individuals will not survive. Only the most fit individuals will be able to survive and pass on their genes to the next generation. Overtime, the accumulation of favorable traits and alleles in a population results in evolution. Choice [A] is false because individuals do not evolve, populations do. Individuals generally do not change their traits once they are born. Choice [B] is false because the strongest individual may not be the most fit individual. Choice [C] is false because evolution is a non-random process where the most fit individuals are "selected". Lastly, choice [D] is false because natural selection can choose different sets of alleles as the environmental pressures change.
Which biome is characterized by coniferous forests and cold winters?
Taiga Coniferous forests (trees with needles for leaves) and cold winters are typical of taigas. The tundra is an extremely cold biome that is characterized by the presence of permafrost, soil that remains permanently frozen. During the summer the topsoil melts and produces a grassland. The artic is not really a biome, and is usually in reference to a tundra. A chaparral is not a biome but more like a community characterized by mild wet winters and hot dry summers. It exists primarily in California and the Mediterranean.
Which biome is characterized as the largest biome on Earth with long harsh, snowy winters, short rainy and humid summers and with a landscape dominated by conifers?
Taiga Deciduous forests do have winters, but they are not characterized as harsh or very snowy and this biome is known for having 4 distinct seasons each year. The savanna biome has small grasses, small shrubs, scattered trees, and have both dry and rainy seasons. The tundra biomes are best defined as regions that have short growing season, cold temperatures all year round and have a layer of permafrost over the soil. The taiga biome has long, cold winters and very short rainy seasons. Taiga does have vegetation with most of the tree covering being provided by conifers like spruce, fir and pine trees. Tropical deserts are characterized as having extremely high temperatures with sporadic rainfall. The only biome that accurately fits the description in the question is D.
What is the fundamental niche of an organism?
The environmental conditions where an organism can potentially live The fundamental niche of an organism is simply the range of environmental conditions an organism can live in, where there is no influence from predators. The realized niche is where the organism actually lives in the environment.
The individual with the most fitness in a population is defined as:
The individual with the greatest number of offspring Fitness is defined as an organism's ability to survive and produce offspring. This is done with the intention of passing on their genes to the next generation. The strongest individual or the most attractive may be traits that help the individual's fitness, but ultimately fitness is defined as the ability to pass on genes and produce offspring.
Which of the following describes the law of parsimony? A. The phylogenetic tree that has the least amount of assumptions is the most preferred. B. The driving force for evolution is divergent evolution. C. Homoplasy can help us develop phylogenetic trees. D. The individual with more fitness will ultimately outcompete others. E. Life evolved from the oceans, to land, and then air.
The phylogenetic tree that has the least amount of assumptions is the most preferred. The law of parsimony, or Occam's Razor, says that when choosing between competing hypotheses, the one that makes the least amount of assumptions is the most preferred. Another way to say it is that the simplest explanation is probably the most accurate. When developing phylogenetic trees, the tree that explains the evolution of organisms with the least amount of assumptions is most likely the correct one.
All of the following are associated with individuals in a population with a r-selected life history strategy EXCEPT for one. Which one is the EXCEPTION? A. They exhibit rapid growth (J-shaped curve). B. They produce many offspring. C. They receive little or no parental care. D. They have a long life span. E. They reach maturity quickly.
They have a long life span. Life-history strategies include K-selected species and r-selected species. r-selected species are exemplified by insects and grasses. These individuals reproduce quickly to take advantage of an opportunity. Their offspring are often small, mature quickly, require little parental care, and die quickly (therefore Choice [D] is false). In contrast, humans exemplify K-selected species. The population size remains relatively constant (at carrying capacity, K). Humans produce a few offspring of larger size and require a significant amount of parental care until they mature.
Plants release most of their water into the hydrological cycle by:
Transpiration The hydrologic cycle is a fancy term for the water cycle. There are three main stages to all of the biogeochemical cycles. They all begin in a reservoir, assimilate into biological organisms, and then are released back into the environment. In the case of water, plants release most of their water by evapotranspiration. This is the process where water vapor escapes through the leaves stomata, which creates a net "pull" up through the plant and brings in more water from the roots.
Which biome is characterized by high temperatures, heavy rainfall, and allows little light to reach the ground?
Tropical rain forest The biome that is characterized by high temperature and heavy rainfall is the tropical rain forest. Rain forests have an extensive canopy so that little actually grows on the forest floor. Epiphytes, which are plants that commensally grow on other plants, are often found here as an adaptation. Temperate deciduous forests have warm summers, cold winters, and moderate precipitations. These forests lose their leaves during the winter. The taiga is characterized by having a coniferous forest (pines, firs, trees with needle leaves) and cold winters. The tropical savanna is a grassland with scattered trees. They have high temperatures, but receive moderate rainfall and allow light to reach the ground.
Sea urchins graze upon small grasses that grow on the bottom of a lake. After the introduction of an exotic sea urchin, the small grasses became over grazed and absent. To solve the problem, a species of otter is introduced into the lake to predate upon the sea urchins, and the balance between the sea urchins and small grasses is restored. What would be the appropriate term for the otter that was introduced?
keystone predator The otter would be considered a SECONDARY consumer, the urchins are the primary consumers, and a hypothetical predator of the otter would be a tertiary consumer. Since the otter is responsible for preventing overgrazing of the small grasses by predating on the out of control urchin population, it is termed a keystone predator that exerts a "top-down" effect on the ecosystem. It is a "key" organism to maintain balance in a community.
What are the two abiotic factors that determine the distribution of terrestrial biomes?
rainfall and temperature Biomes are classified based on the biological effects of temperature and rainfall on vegetation. The majority of biomes are dependent on these two factors. For example, deserts have a lack of rainfall and very high temperatures, giving them their characteristics. In contrast, rainforests have lots of rainfall and warm temperatures, providing an environment for a biologically diverse biome. Many descriptions you see on biomes will have a chart displaying their average temperature and rainfall throughout the year.
An entire forest is leveled after a forest fire. The process by which organisms will repopulate an area is called:
secondary succession Succession is the process that ecological areas go through to repopulate a community. Following a forest fire, the environment begins from the producer's level and must first grow small grasses, then small shrubs, before consumers and higher-level consumers will repopulate the area. In the event of a volcano, this would be an example of primary succession, as there is no soil to sustain plants. Instead, bacteria populate the area, and eventually give rise to soil and plants and animals. Homeostasis refers to the internal regulation of an organism. Biological regeneration is a distractor answer choice testing your true knowledge of the topic at hand.
