EXAM II Flashcards
What strongly influenced the evolution of life on the island of Hawaii after it rose above the sea surface?
The founder effect
What mechanism likely explains the genetic uniqueness of the Dunkers population? They moved and did not marry outside community.
The founder effect, inbreeding, genetic drift
What explains the haphazard changes in allele frequency in a population of Drosophila melanogaster? No effect of allele.
The allele is a neutral allele whose frequency is affected by genetic drift.
What produces variation for evolution through chance events?
Genetic drift produces variation for evolution when chance events cause allele frequencies to fluctuate unpredictably.
What does it mean when an allele is ‘fixed’ in a population?
It is an indication of no genetic variation at that locus in the population.
What is the example of artificial selection involving Buckeye butterflies?
Edith Smith bred the bluest butterflies together to produce vibrant blue butterflies for use in wedding displays.
What describes the bottleneck effect?
Sudden change in environments that alters gene frequency of a population.
What effect did an earthquake have on a ground-squirrel population by killing 98%, and the surviving having broader stripes than initial population?
Genetic bottleneck
What challenge does a population with minimal genetic variability face?
It will have difficulty responding to new challenges.
What mechanism produces variation for evolution by shuffling existing alleles?
Sexual reproduction
How does anisogamy influence mating strategies?
Males fight for access to females to secure mating opportunities.
What does the ‘good genes’ hypothesis explain?
The indirect benefit of female choice is the underlying genetic quality, or good genes, of males with elaborate or bright ornaments.
What is a mode of reproduction where female sex cells are not fertilized by sperm?
Parthenogenesis
What did McDonald and colleagues find about asexually reproducing yeast cells?
Deleterious mutations can hitchhike to fixation with beneficial mutation.
What is NOT true regarding male harlequin beetles in intrasexual selection?
Females are choosy and prefer males with larger bodies and longer forelegs.
According to the twofold cost of sex, natural selection should favor all except?
Asexual reproduction only produces clones.
In the ‘good genes’ hypothesis, ornaments may indicate that males are any of the following EXCEPT?
Able to provide a direct benefit to females.
Why are females more likely to invest additional care in offspring compared to males?
It is likely that recipients of this care are her offspring.
What is a direct benefit of female choice?
A benefit that affects a particular female directly.
What is an example of sperm competition?
Certain male seed beetles have spines on their copulatory organ that enable them to physically remove another male’s sperm from the female reproductive tract.
What was Darwin’s explanation for the evolution of bright colors in males?
Sexual Selection
What is an example of a trade-off in reproductive strategies?
Males with large testes often have better mating success but take longer to develop than those with small testes.
What is NOT considered a potential benefit of sexual reproduction?
Sexual organisms produce twice as many offspring as asexual organisms.
What is NOT a cost of sexual reproduction?
Meiosis produces recombinant chromosomes, creating gametes with unique combinations of alleles.
What does the two-fold cost of sex refer to?
The disadvantages of being a sexual rather than an asexual organism.
What can we predict about sexual selection strength?
Members of the sex subject to strong sexual selection will be competitive; members of the sex subject to weak sexual selection will choose.
What is NOT an example of a direct food benefit from female choice?
Female weaverbirds choosing males that have already manufactured a nest.
What are examples of direct food benefits that result from female choice?
Sexual cannibalism displayed by female redback spiders & the spermatophore presented by male katydids.
When is a male signal likely to be honest according to sexual selection theory?
It is condition-dependent & it is costly to produce.
What is NOT true about mate guarding?
Exclusive to a type of mating system.
What trait evolved in males to make females less attractive to other males?
Proteins in their ejaculate.
What is intrasexual selection?
Selection for the ability to successfully compete with members of their own sex to mate with the opposite sex.
What is the definition of sexual selection?
Individuals with certain inherited traits are more appealing to potential mates, making them more likely to reproduce than those without the traits.
What do guppies that live in streams with high predation risk do compared to those in lower risk streams?
Produce smaller offspring.
What is an iteroparous annual?
A plant individual that reproduces twice in its lifetime and lives for 1 year.
Why would predation on small individuals lead to delayed sexual maturity?
The delay allows more resources to be devoted into growing to a larger size that is less likely to be eaten.
What is parental investment?
The amount of time and energy given to an offspring.
What is iteroparous?
An organism that reproduces more than once during its life span.
What is TRUE regarding semelparity?
Semelparity often arises when there is a large amount of energy required for reproduction.
What does selection favor in populations with a high survival rate?
Individuals that reproduce late in life and allocate a lot of energy to delaying senescence.
Golden lion tamarins are small South American monkeys that usually give birth to twins, although they sometimes produce as many as four offspring. The young are large relative to adult body size, and are carried and protected by both parents, as well as any young from previous years that are still living in the group. Given this breeding system …What is FALSE about golden lion tamarins’ breeding system?
On average, individuals that have litters of four have the highest fitness.
What life history traits will evolution favor based on hunters’ preference for larger white-tailed deer?
Smaller adult sizes, shorter life spans, higher fecundity, and earlier times to maturity.
What does the principle of allocation state?
Life history traits are adapted to maximize fitness.
What is the least likely outcome of having a large number of offspring?
Competition with offspring for food could reduce energy for future reproduction.
Which does NOT have slow life history attributes?
Herbaceous weeds.
What has slow life history attributes?
Giant tortoise, elephant, and an oak tree.
Which does NOT have fast life history attributes?
Albatross.
What is fecundity?
The number of offspring produced by an organism per reproductive episode.
What advantage does bet hedging provide?
It has been proposed as an advantage to iteroparity.
What is senescence?
A gradual decrease in fecundity and increase in the probability of mortality.
What indicates senescence in human females?
Increased prevalence of birth defects in offspring and infertility after 30 years of age.
What characteristic of frogs that lay eggs on land where they develop directly into froglets is typical of slow life history organisms?
Fewer offspring.
Why are trade-offs among life history traits common?
Limited resources and physical limitations.
What did David Lack’s classic work on songbird reproduction conclude?
There was an optimum clutch size.
What do you expect Daphnia’s average adult size to do after the introduction of a phantom midge predator? …………In a lake in Ontario, Canada, a small, invasive invertebrate predator called a phantom midge has been introduced. This phantom midge swims around the water column and preferentially consumes the smallest individuals of the zooplankton genus Daphnia. Following the introduction of this novel predator, you expect Daphnia’s average adult size to _____, its time to reproductive maturity to _____, and its average life span to _…
Decrease, decrease, decrease.
How does the geometric growth model differ from the exponential growth model?
The geometric growth model uses regular time intervals.
What term indicates the intrinsic rate of increase in the exponential growth model?
r.
What can we conclude about lambda for a population of deer with 100 adults, 15 deaths, and 25 births?
Lambda > 1.
What is the intrinsic growth rate, r?
The highest possible per capita increase in population size under ideal conditions.
What occurs when the number of births is less than the number of deaths in an exponential growth model?
r < 0.
What is negative density dependence?
The per capita population growth rate decreases as population becomes larger.
What happens under positive density dependence?
Population growth rate increases as populations become larger.
What is an example of positive density-dependent population regulation?
Lice find mates more easily and produce more offspring when there are many lice on an individual fish.
What does the Allee effect describe?
Positive density-dependent population regulation.
What is an example of negative density-dependent population regulation?
Salamander larvae cannibalizing each other when there are too many in a pond. (When the pond contains few larvae, they mostly eat small invertebrates and have a high survival rate. When there are many salamander larvae in a pond, the larvae will also cannibalize each other and have a low survival rate.)
What is an example of density-independent population regulation?
Alpine ibex have high mortality rates during winters with heavy snow regardless of population size.
What does the logistic growth model describe? (Factors)
A maximum population size that is limited by density-dependent factors.
Under what condition is the per capita rate of increase highest in the logistic growth model?
N = K/2.
What is the most accurate statement about conservation biology of species with positive density-dependent population regulation?
If the population is small, it may not be able to increase.
What form of population growth results in an S-shaped curve?
Logistic growth.
What does an age structure pyramid with a broad base and a narrow top indicate?
The population is growing.
What can we conclude about a population with few individuals in young classes but many in medium-aged and old classes?
The population is declining.
What type of survivorship curve describes a species with high juvenile mortality but low adult mortality?
Type III curve.
The population contains 50 males and 50 females. What is the expected number of female raccoons in a park next year if R0 = 2?
100.
What does a stable age distribution indicate?
The proportion of individuals in each age class remains constant.
What type of survivorship curve are plants more likely to show?
Type III.
What is the term for individuals finding mates and reproducing more easily in larger populations?
The Allee effect.
Which is likely to follow an exponential increase in population size?
I. a population of mice that has consumed most of the food in its habitat
II. a small population of rats recently introduced to an island with many resources
III. bacteria recently placed on a new petri dish with suitable growth medium
II & III Only.
Which reflects density-independent population regulation?
I. a winter storm that kills birds with equal probability regardless of bird abundance
II. a drought that kills a higher proportion of plants when there are many plants and a smaller proportion when there are fewer plants
III. a lethal disease that is more easily transmitted when animals are found in high abundance than in low abundance
I Only.
Which reflects positive density-dependent population regulation?
I. Small populations of flowers produce fewer seeds per individual than large populations of flowers.
II. Large groups of birds are better able to detect and avoid predators than small groups of birds.
III. The probability that a forest predator will kill a squirrel does not depend on the size of the squirrel populations
I and II.
Which reflects negative density dependence?
I. A fungus infects and kills plants at a higher rate when the plants are abundant than when they are rare.
II. A group of birds has a higher per capita survival rate when it is large than when it is small.
III. A large population of deer exhausts local food supplies and has a high risk of death; a small population has plentiful food and low risk of death.
I and III.
Which accurately describes the inflection point in the logistic growth model?
I. Population growth slows after the inflection point.
II. The inflection point is equal to the carrying capacity.
III. The highest growth rate occurs at the inflection point.
I and III.
Which factors could limit a species’ carrying capacity?
I. the amount of food available
II. the number of eggs a female can produce
III. the number of nesting sites present
I and III.
What determines the maximum number of individuals a population can sustain in the logistic growth model?
K.
What is the difference in approach between the geometric growth equation and the exponential growth equation?
Geometric growth models species that reproduce at discrete times.
What community measure does Shannon’s index quantify?
Species diversity.
In the logistic growth model, which term determines the maximum number of individuals a population can sustain?
K
What is the difference in approach between the geometric growth equation and the exponential growth equation?
Geometric growth models species that reproduce at discrete times
What is the relation between habitat diversity and species diversity?
positive
Based on MacArthur and Wilson’s equilibrium theory of island biogeography at Ŝ, what happens to the number of species on the island?
the number of species on the island stays the same though the actual species present on the island may be changing.
If you were to take data from a stream collection of 100 macroinvertebrates and construct a rank abundance curve, what would it look like?
a curve initially very steeply downward on the left side and leveling off on the right
Based on the intermediate disturbance hypothesis, a community’s species diversity is increased by ________.
moderate levels of disturbance
What does the equilibrium theory of island biogeography state about the number of species on an island?
the number of species on an island reflects a balance between colonization of new species and extinction of existing species
Why do islands at equilibrium that are farther from the mainland contain fewer species than nearer islands?
farther islands have less colonization
If a stream has high richness but low evenness, which collection would best represent it?
60 caddisflies, 20 mayflies, 10 stoneflies, 5 damselflies, 4 dobsonflies, 1 cranefly
Which of the following is a correct statement about MacArthur and Wilson’s island equilibrium model?
small islands receive few new immigrants
On which type of island should we expect to see the lowest level of biodiversity when equilibrium is reached?
a small island located far from the source of colonizing species
Communities with _____ species are _____ stable.
many; more
How would adding resources such as fertilizer to an area affect the species in a community?
it would reduce richness
What does the variable (pi) used in the Shannon’s Diversity Index represent?
the relative abundance value for each of the species in the community under study
What is one plausible hypothesis to explain why species richness is higher in tropical than in temperate regions?
tropical regions generally have more available water and higher levels of solar radiation
Why do moderate levels of disturbance result in an increase in community diversity?
Habitats are opened up for less competitive species
According to the island equilibrium model, species richness would be greatest on an island that is?
large and close to mainland
In the equilibrium theory of island biogeography, equilibrium occurs where extinction _____ colonization.
Equals
What is a widely supported explanation for the tendency of tropical communities to have greater species diversity than temperate or polar communities?
Tropical communities have higher sunlight and precipitation, and are generally older than temperate or polar communities
Why are there more species in tropical areas than in places more distant from the equator?
a longer time frame without disturbances for evolution and speciation
Why do smaller islands at equilibrium contain fewer species than larger islands?
greater extinction
According to the island equilibrium model, species richness would be lowest on an island that is ________.
small and remote
As a community develops and more species enter, how will this affect the Shannon index (H) of the community?
The H will increase
What does species richness of a community refer to?
the number of different species found in the community
Which of the following characteristics is typical of biodiversity hotspots?
a large number of endemic species
At what frequency of disturbance would the most diversity be expected?
medium frequency
According to the intermediate disturbance hypothesis, why might species diversity be low under conditions of low disturbance or stress?
there may be high levels of competitive exclusion
Who described the equilibrium theory of island biogeography?
E.O. Wilson & Robert MacArthur
True or False? Humans can create ‘islands’ that are not found in water, but are fragmented landscapes, ‘stranding’ some species.
True
What 2 statements is consistent with the principle of competitive exclusion?
If two species have the same fundamental niche, one will exclude the other competing species. & Even a slight reproductive advantage will eventually lead to the elimination of the less well adapted of two competing species.
Two species of barnacles, stellate and rock barnacles, occupy the rocky intertidal zone of the Scottish coast and illustrate factors that can determine species distribution in a community. Larvae of both species settle throughout the intertidal zone, but adult barnacles occupy specific zones. The smaller stellate barnacle lives only in higher zones, where the environment dries out between high tides. The larger, faster-reproducing rock barnacle lives only at lower zones. In general, the intertidal zonation seen in the barnacles is due to
competitive interactions and predation.
A species of tree is found from the Canadian border down to the southeast United States. This is called the species’
Geographic range
An endangered frog species lives in only a few forest patches found throughout the Pacific Northwest of the United States. The Pacific Northwest is its _____, and the forest patches are its _____.
geographic range; realized niche
What phenomenon accounts for the coexistence of closely related species sharing the same limited resource?
Resource partitioning
What would happen if one close competitor species is experimentally removed from the community?
The remaining species would be expected to expand its realized niche.
What could be concluded about the fundamental and realized niches of two barnacle species excluded from the lower intertidal zone?
The fundamental and realized niches of B. balanoides are identical, but the fundamental and realized niches of C. stellatus are different.
Two species of barnacles, stellate and rock barnacles, occupy the rocky intertidal zone of the Scottish coast and illustrate factors that can determine species distribution in a community. Larvae of both species settle throughout the intertidal zone, but adult barnacles occupy specific zones. The smaller stellate barnacle lives only in higher zones, where the environment dries out between high tides. The larger, faster-reproducing rock barnacle lives only at lower zones. If rock barnacles were entirely removed from this community, what would most likely happen to the population of stellate barnacles?
They would expand their range to include both the low and high areas.
What is not true about a species’ geographic range?
The geographic area is always contiguous.
What is a valid conclusion from the removal of Balanus in an experiment?
The removal of Balanus shows that competitive exclusion prevented Chthamalus from occupying the lower tide region of its fundamental niche.
How does character displacement differ from resource partitioning?
Character displacement is directly linked to the evolution of genotypes that have allowed alternate resource use.
What happens through resource partitioning?
Slight variations in niche allow closely related species to coexist in the same habitat.
What is the pattern of density and spacing of individuals in a population called?
Spatial Structure
How might an ecologist test whether a species is occupying all of its fundamental niche?
Observe if the species expands its range after the removal of a competitor.
What is the range of abiotic conditions under which a species can persist called?
Fundamental Niche
As you study two closely related predatory insect species, the two-spot and the three-spot avenger beetles, you notice that each species seeks prey at dawn in areas without the other species. However, where their ranges overlap, the two-spot avenger beetle hunts at night and the three-spot hunts in the morning. When you bring them into the laboratory and isolate the two different species, you discover that the offspring of both species are found to be nocturnal. You have discovered an example of ________.
Resource partitioning
What is an organism’s realized niche?
The way an organism uses environmental resources and interacts with the community.
What is an organism’s fundamental niche?
All the ways an organism could interact with the environment if no limiting factors existed.
Define Resource Partitioning & Give an Example.
A way for species to reduce competition when they are occupying the same niche. An example is warblers living in different parts of the same tree or spiny mice foraging at different times.
What type of seeds dominated the initial succession on the island of Krakatau?
wind-dispersed
What is a major reason that facilitating species outnumber inhibiting species early in secondary succession?
Early settlers must facilitate each other to survive; they prepare the environment for later species.
Why were wind- and sea-dispersed seeds the first to colonize and survive on Krakatau?
In the early days of colonization, there were no forests to attract animals that could disperse seeds.
In 1988, fires in Yellowstone National Park affected over 36 percent of its area. Where the fires burned hottest, most plants, including forest trees, were killed. Where the fires were less severe, forest trees survived and only smaller plants were killed. What is most likely to happen in terms of succession in situations like this?
Secondary succession will occur in all burned areas.
Where does secondary succession take place?
It takes place in habitats that have been disturbed and contain no plants but still contain organic soil.
Which of the following is a pioneer species?
Annual plants with small, light seeds
After the 1980 eruption of Mount St. Helens, populations of small mammals and other organisms recovered much more quickly in the zones of secondary succession than in the Pumice Plain, where primary succession occurred. This more rapid recovery was aided by all of the following factors except
Areas devoid of life that provided a “blank canvas” for succession.
Why do plants in early seral stages exhibit high levels of tolerance?
Facilitation
What role do nitrogen fixers play in volcanic areas like the Hawaiian Islands?
By increasing nitrogen availability, these invaders enable the establishment of other invasive but non-nitrogen-fixing plant species.
What is one of the traits common in late-succession plant species?
few seeds
What does succession refer to?
change in Species composition over time.
What is the last seral stage in the process of succession called?
Climax community.
What usually begins primary succession?
Lichens and mosses.
Why does secondary succession occur faster than primary succession?
Soil in secondary sites can contain plant seeds and roots.
How could fire maintain pine populations in certain areas of the western United States?
Fires kill understory species, allowing pine seedlings to thrive.
Why might seed viability be longer with early-successional species?
Seeds from early-successional plants may not germinate until conditions change after a disturbance.
Why might direct observation of succession be easier in intertidal communities?
Organisms in an intertidal area have shorter generation times than organisms in terrestrial communities.
Over the course of terrestrial succession,
What is the general pattern of species richness over the course of terrestrial succession?
An increase that plateaus, followed by a slight decline.
Which of the following is NOT a trait of a pioneer species?
Shade tolerant
What are some traits of pioneer species?
Many seeds, small seeds, fast growing.
If the Surtsey volcano erupted again and a new layer of lava covered the island, would the resulting succession be considered primary or secondary?
Primary; the island would have a new, bare surface with no existing life.
What is a pioneer species?
The first species to arrive at a site.
What happens as trees grow in a forest concerning understory plants?
They shade the understory plants, decreasing their ability to receive light and carry out photosynthesis. An example of Facilitation
The presence of soil fauna increases the likelihood that many plants will be established during succession. This is an example of
Facilitation
What does a climax community generally consist of?
organisms that dominate in a given biome.
A woodland was felled, stripped of its existing vegetation, and left to undergo secondary succession. Which factor in this situation is different from primary succession and ensures that secondary succession occurs more rapidly than primary succession does?
Seeds and roots remaining in the soil can rapidly regenerate the vegetation.
When Mount St. Helens erupted, three relatively distinct zones of destruction resulted: the Pumice Plain, which was essentially sterilized and had no remaining life; the Blowdown Zone on the mountain slopes, where downed trees and vegetation were covered with mud and ash; and farther down, forests that remained standing but were also covered with mud and ash. Based on these levels of destruction, what would the likely rate of recovery be for these zones?
The lower forests would recover fastest, followed by the Blowdown Zone and then the Pumice Plain.
What is the usual response of a community after a major disturbance?
Succession
Primary succession is most likely to occur after what event?
A volcano erupts.
What type of succession is exemplified by a change in tree composition after a severe ice storm?
Secondary
What is an example of character displacement?
Finches in the Galápagos Islands are smaller on islands where bees are present, because bees compete with the finches for cactus nectar.
What does ecological niche modeling determine when assessing a species in danger of extinction?
Fundamental niche
The original eruption at Krakatau is an example of which form of succession?
Primary
Correct the statement: All species make it more challenging for new colonization.
Sometimes they inhibit, but other times they facilitate.
Throughout the stages of succession, species are sometimes what?
Sometimes replaced so community composition is in flux.
In this region, how long would it take for a bare field to return to a climax community?
100 years
What form of succession does a forest fire represent?
Secondary
Males of some species have proteins in their ejaculate that cause the female to be less attractive to other males for some period of time. Such a trait probably evolved initially through ________ but could also lead to ________ if remating is beneficial for females.
male–male competition; sexual conflict and antagonistic coevolution
The equilibrium theory of island biogeography states that the number of species on an island reflects a balance between what?
colonization of new species and extinction of existing species
A scientist has two species of paramecia that have almost identical ecological niches. The graphs demonstrate that when the populations of the two species are raised separately in the lab, they both thrive. However, when the populations share the same habitat, one of the populations crashes and the other thrives. What ecological principle does this describe?
Competitive Exclusion
After the 1980 eruption of Mount St. Helens, populations of small mammals and other organisms recovered much more quickly in the zones of secondary succession than in primary succession occurred. This more rapid recovery was aided by all of the following factors
Still-existing life that jump-started the recovery process, still-existing soil that enabled plant growth, burrowing, and other life processes, nutrients already available in the soil, and the underground burrows of small mammals that aided movement and provided habitat.
Areas formed by volcanic activity, such as the Hawaiian Islands, have a lava substrate that is nitrogen-deficient. Many successful invaders in these areas are nitrogen fixers. By increasing nitrogen availability, these invaders enable the establishment of other invasive but non-nitrogen-fixing plant species. The changes to community structure result from what?
Facilitation
What are the prezygotic isolating mechanisms?
Behavior, Habitat, Gametic, Temporal and Mechanical
What are the postzygotic isolating mechanisms?
Hybrid inviability, Hybrid sterility, Hybrid breakdown
What is a mutation?
Any change to the genomic sequence of an organism.
What is genetic drift?
Evolution arising from random changes in genetic composition of a population from one generation to the next.
What is a fixed allele?
An allele that remains in a population when all alternative alleles have disappeared.
What is gene flow?
The movement (or migration) of alleles from one population to another.
What is a genetic bottleneck?
An event in which the number of individuals in a population is reduced drastically.
What is the founder effect?
A form of genetic drift describing the loss of allelic variation when founding a new population from a very small number of individuals.
What is the inbreeding coefficient?
Probability that the two alleles at any locus in an individual will be identical.
What is inbreeding depression?
Reduction in the average fitness of inbred individuals due to expression of rare recessive alleles.
What is a beneficial mutation?
Mutations that increase the fitness of the individual that possesses it.
What is a neutral mutation?
Mutations that neither increase nor decrease the fitness of the individual that possesses it.
What is a detrimental mutation?
Mutations that reduce the fitness of the individual that possesses it.
When does a genetic bottleneck occur?
When there is a drastic reduction in population size.
Explain genetic drift and how it differs from natural selection.
Genetic Drift is random changes in allele frequencies due to chance, not fitness. Natural Selection is Alleles that increase fitness become more common over time, driven by survival and reproduction advantages.
Explain the bottleneck effect and its relationship to genetic drift.
The bottleneck effect sharp reduction in population size that reduces genetic diversity due to a smaller gene pool, leading to random changes in allele frequencies (genetic drift). AKA the bottleneck causes/leads to genetic drift
Example: Cheetahs suffered a bottleneck from climate changes and human activity, resulting in low genetic diversity and increased disease susceptibility and reduced reproductivity.
Explain the founder effect and its relationship to the loss of genetic variation.
When a small group establishes a new population, their genetic variation is not representative of the larger population.
Example: Pitcairn Island’s settlers (27 people) resulted in distinct genotype frequencies from the surrounding British population due to limited genetic variation.
Explain How does nonrandom mating affect allele and genotype frequencies? Give Example
Occurs when individuals are more likely to mate with others that share certain traits (proximity, similar phenotypes) This affects allele and genotype frequencies because it alters the distribution of alleles compared to what would be expected under random mating.
Example: Inbreeding inbreeding (nonrandom mating) can increase the frequency of homozygous genotypes, reducing genetic diversity and potentially leading to inbreeding depression
How to interpret inbreeding coefficients?
The value of F ranges from 0 to 1, where 0 indicates no inbreeding and 1 indicates complete inbreeding. A higher inbreeding coefficient suggests a higher degree of relatedness between individuals in the population, which can lead to a higher likelihood of harmful recessive alleles being expressed, decreasing fitness
Why is sexual selection widespread despite high reproductive costs?
Leads to increased reproductive success. While sexual reproduction requires more energy, it provides significant advantages, such as genetic diversity. This diversity helps organisms better cope with predators, diseases, and environmental changes, offering a long-term survival advantage, which can outweigh the immediate costs
What is the difference between sexual selection and natural selection?
Sexual Selection focuses on competition for mates or mate choice, while Natural Selection focuses on survival and fitness.
Sexual Selection is a form of natural selection that focuses on competition for mates (intrasexual selection) or mate choice (intersexual selection). It leads to traits that enhance an individual’s ability to reproduce.
Natural Selection is the process by which traits that increase survival and fitness become more common in a population.
Why is sexual selection an outcome of the evolution of sex?
Because individuals with traits that make them more attractive or competitive for mates are more likely to reproduce, driving the evolution of those traits.
Why might selection favor females who choose the male on the right (red in color)?
Females may favor the red male because his color could be a signal of “good genes”, indicating higher fitness, which would benefit offspring by enhancing their survival or reproductive success. This preference could be linked to the indirect benefits females seek, like healthier offspring.
Explain the relationship between operational sex ratio and male-male competition.
Operational Sex Ratio (OSR) refers to the number of males or females available for mating at a given time. If the OSR is male-biased (more males than females), there is increased male-male competition for mating opportunities. This intensifies sexual selection, with males competing more aggressively for females, leading to the evolution of traits like bright colors or displays.
Explain how females of a species could have high intrasexual competition. What would have to occur in a species in order for this to occur?
Females can have high intrasexual competition if their reproductive success is influenced by competition for resources or mates. This could happen if Females are competing for access to limited resources that influence reproductive success or Mating opportunities are limited and females actively compete with each other for access to the best mates.
Compare and contrast the costs and benefits of sexual reproduction.
Benefits: Greater genetic diversity, which increases the population’s ability to adapt to changing environments and resist diseases.
Costs: Finding a mate, producing mating behaviors, and the two-fold cost of sex (females only contribute half their genes).
Compare and contrast the costs and benefits of asexual reproduction.
Benefits: Faster reproduction, no need for a mate, and the ability to pass on all genes.
Costs: Lack of genetic diversity, making the population more vulnerable to diseases, predators, and environmental changes.
Explain how differential investment by males and females can lead to sexual selection.
Males typically invest less energy in reproduction (producing many small sperm), while females invest more energy (producing fewer, larger eggs). This difference leads to sexual selection, where females are selective and choose mates that offer good genetic traits, while males compete to gain access to females.
Describe the Red Queen Hypothesis and give an example.
Suggests that sexual reproduction allows species to evolve and stay ahead of constantly evolving threats like parasites, predators, and diseases. The metaphor comes from the idea that “it takes all the running to stay in the same place.”
Example: The arms race between host organisms and parasites—sexual reproduction provides variation that helps hosts adapt to evolving parasites.
Explain sperm competition and give an example.
When sperm from different males compete to fertilize the same female’s eggs. It can involve mechanisms like sperm removal or the pooling of sperm to increase swimming speed.
Example: In species like salamanders, males may release chemicals to remove or displace sperm from previous males.
Describe the example of sneaker males.
Males that adopt a strategy of sneaking into matings to avoid direct competition with larger, dominant males.
Example, in cuttlefish, some males mimic females to sneak past dominant males and mate with females.
What are direct benefits females can receive from choosing the best male?
Food, Protection, Good territory.
What are indirect benefits females can receive from choosing the best male?
Good genes that increase fitness of offspring.
Explain how a trait that appears detrimental (like a peacock tail or a brightly colored male) could evolve.
They increase visibility to predators, but they can evolve through sexual selection. These traits signal good genes (indicating fitness), so females may prefer mates with these traits, leading to the spread of the trait in the population.
Explain the relationship between operational sex ratio and intrasexual selection.
The Operational Sex Ratio (OSR) influences intrasexual selection. When there are more males than females (male-biased OSR), males will compete more intensively for access to females. This competition can lead to the evolution of traits that help males succeed in securing mates (size, aggression, displays).
Define Intrasexual.
(within the same sex) usually male vs. male.
Define Intersexual.
(between sexes) when members of the limiting sex discriminate among mates.
What are the three components of an individual’s life history?
How many offspring are produced per reproductive episode, how often the organism reproduces, and the age of first reproduction.
What is the principle of allocation?
If energy is allocated to one function (growth or reproduction), it reduces energy available for other functions.
What are the three support ideas Lack offered for his principles on clutch size?
Trade-offs with survival and future reproductive efforts, clutch size may reduce fitness, individual birds differ in reproductive capacity.
Define Semelparity.
Species that reproduce once and die.
Define Iteroparity.
Species that produce offspring repeatedly.
Define r-selected syndrome.
Predators mainly prey on adults.
Define k-selected syndrome.
Predators mainly prey on younger animals.
Describe the characteristics of a fast life history.
Organisms reproduce quickly, have many offspring, mature early, and have a short lifespan.
Example: Dandelions.
Describe the characteristics of a slow life history.
Organisms reproduce later, have fewer offspring, invest more in each offspring, and have a longer lifespan.
Example: Chimpanzees.
Describe the principle of allocation and give an example.
Energy invested in one function reduces energy available for other functions.
Example: A plant may allocate more energy to producing larger seeds, which may result in fewer seeds produced.
Describe and give an example of an ecological trade-off.
When an organism must balance energy allocation between competing needs.
Example: A bird may invest more energy in producing a few large eggs with a higher survival rate, but at the cost of producing fewer eggs overall.
Define evolutionary fitness.
An organism’s ability to survive, reproduce, and pass on its genes to the next generation. It is a measure of reproductive success.
Describe the relationship between offspring size and offspring number.
Generally, there is a trade-off between offspring size and number. Larger offspring may have a higher chance of survival but fewer can be produced, while smaller offspring can be produced in larger numbers but may have lower survival rates.
Explain Lack’s Principle and why clutch sizes tend to be smaller than predicted.
States that a bird’s clutch size is adapted to correspond with the maximum number of offspring that parents can raise successfully, considering their ability to provide enough food.
Clutch sizes tend to be smaller than predicted because of the trade-off between the number of offspring and parental care.
Describe the relationship between growth, age at sexual maturity, and lifespan.
There is a trade-off between energy spent on growth and reproduction. Organisms that invest in growth tend to mature later but may live longer and produce more offspring over time. Smaller, fast-growing organisms tend to reach sexual maturity earlier but have shorter lifespans.
Explain the results of Endler and Reznick’s experiment with guppies and their predators.
Showed that in high-predation environments, guppies had smaller sizes, produced more small offspring, and matured faster (“fast” life history). In low-predation environments, guppies invested more in growth and had fewer, larger offspring.
What are population models used to predict?
The size of populations in the future which inform how populations can be managed.
Define growth rate.
The number of individuals added to the population minus the number of individuals that die.
Define negative density-dependence.
The rate of population growth decreases as population density increases.
Examples:
Competition (for resources such as food and space.)
Increased mortality (due to disease or predation as population density rises.)
Define carrying capacity.
The number of individuals the environment can support.
Define demography.
The study of vital statistics of a population and how they change over time.
Define age structure.
The proportion of the population that occurs at different age classes.
Define Type I survivorship curve.
Low death rates during early and middle life, with an increase in death rates among older age groups.
Define Type II survivorship curve.
A constant death rate over the organism’s life span.
Define Type III survivorship curve.
High death rates for the young and a lower death rate for survivors.
Define life table.
An age-specific summary of the survival and reproductive rates within a population.
Define cohort life table.
Identify individuals born at the same time and keep records from birth.
Define static life table.
Record age at death for individuals.
Age distribution is where you what?
Calculate the difference in proportion of individuals from each age class.
What is the net reproductive rate (R0)?
Average number of individuals produced in its lifetime.
Describe the exponential growth model.
Describes how a population grows without limits under ideal conditions.
Describe the geometric growth model.
Used for populations that reproduce in discrete, non-overlapping generations. It assumes growth occurs at regular time intervals (yearly)
Describe the logistic growth model.
Describes population growth that is initially exponential but slows as the population approaches the carrying capacity (K), where resources are limited.
Differentiate between exponential, geometric, and logistic growth.
Exponential Growth:
Continuous growth with no limits (ideal conditions). Describes populations growing at a constant rate indefinitely. Produces a J-shaped curve.
Geometric Growth:
Discrete, non-overlapping generations. Population size increases at a constant ratio per time period. Produces a stepped growth pattern.
Logistic Growth:
Growth starts exponentially, but slows as the population reaches carrying capacity.Describes real-world populations with limited resources. Produces an S-shaped curve.
Predict the effect of carrying capacity on population growth rate.
As the population approaches the carrying capacity K, the growth rate slows and eventually levels off. The growth rate reaches zero when N=K
Logistic Growth shows this effect as an S-shaped curve, with the population increasing rapidly at first and then slowing down as it nears K. Once at K, the population stabilizes.
What is Exponential Growth?
Continuous growth with no limits, describing populations growing at a constant rate indefinitely. Produces a J-shaped curve.
What is Geometric Growth?
Discrete, non-overlapping generations where population size increases at a constant ratio per time period. Produces a stepped growth pattern.
What is Logistic Growth?
Growth that starts exponentially but slows as the population reaches carrying capacity, describing real-world populations with limited resources. Produces an S-shaped curve.
What effect does carrying capacity have on population growth rate?
As the population approaches carrying capacity (K), the growth rate slows and eventually levels off, reaching zero when N=K.
Define density dependent growth factors and give examples.
Affect population growth based on the population size (density). As the population increases, the effect of these factors becomes stronger.
Examples: Competition (for food, space, and mates), Disease (transmission increases with population density), Predation (intensifies as population density increases), Territoriality (limited space as density increases).
Define density independent growth factors and give examples.
Factors that affect population growth regardless of population size, causing dramatic changes in population size.
Examples: Natural disasters (hurricanes, earthquakes), Climate changes (temperature extremes), Pollution (habitat destruction not dependent on density).
What is Positive Density Dependent Growth (Allee Effect)? and give exmxaples
As population density increases, the growth rate also increases, often due to cooperative behaviors or increased reproductive success in larger groups.
Examples: Cooperative hunting in wolves or lions, Pollination in plants that rely on a certain number of individuals.
Define Dispersal.
The movement of individuals from one area to another, typically involving leaving the area of origin and not returning.
What is the Intermediate Disturbance Hypothesis?
States that moderate levels of disturbance can foster greater diversity than either high or low levels of disturbance.
What are two key factors affecting latitudinal gradients of species richness?
Evolutionary history and climate.
Why might tropical environments have greater species richness?
Because there has been more time for speciation to occur.
What are two key biogeographic factors affecting species diversity?
Latitude and Area.
What is a major determinant in biodiversity?
Nutrient Availability.
Why is there a negative relationship between nutrient availability and algal and plant species diversity?
Due to competitive exclusion and eutrophication.
What does the island equilibrium model say?
Larger islands have more species, and islands closer to the mainland have more species. Large and close islands should have the most.
What happens when the island equilibrium model reaches equilibrium?
The rate of immigration is equal to the rate of extinction.
What does H’ represent?
Value of Shannon diversity index.
What does pi represent?
Proportion of the i’th species within the community.
What does S represent?
Number of species in the community.
What does ln represent?
Natural logarithm of pi.
How many species are there when the Shannon index is 0?
Only one species.
Define Absolute abundance.
The number of individuals of each species.
Define Species evenness or relative abundance.
The proportion of individuals in a community represented by each species.
Describe a Speciose habitat.
A habitat is speciose if it has a high number of species (high species richness). For example, a tropical rainforest.
Describe an Even habitat.
A habitat is even if the species within it are distributed more equally, with no species dominating the community.
How can you compare speciose vs. even habitats?
By looking at the rank-abundance curve, which shows the relative abundance of each species.
Define Rank-Abundance Curve.
Shows the relative abundance of each species in a community, ranked from the most to the least abundant.
What does the slope of the rank-abundance curve reflect?
Evenness: A steep slope indicates that a few species are dominant (low evenness), while a gentler slope means species are more evenly distributed (high evenness).
What does the number of points on a rank-abundance curve represent?
Indicates species richness: more points = higher species richness.
Explain what features of an environment lead to higher species diversity?
Environmental complexity, stable climate, resource availability, and low disturbance.
Environmental Complexity: More complex habitats varied vegetation, more microhabitats) tend to have higher diversity. Climate: (Stable, warm, and wet climates, like in the tropics, support more species.) Resource Availability: (A balance of resources, such as nutrients, supports more species.) Low Disturbance: Environments with moderate disturbance often have higher diversity (Intermediate Disturbance Hypothesis).
Explain what features of an environment lead to lower species diversity?
Harsh Environments: Extreme climates (deserts, polar regions) typically support fewer species. Monotonous Habitats: Simple habitats with little environmental complexity often support fewer species.
Why are the tropics so biodiverse?
Due to evolutionary history, stable climate, and higher primary productivity.
Evolutionary History: Tropical environments have had more time for speciation to occur, as they have been relatively stable over long periods.
Stable Climate: The warm and wet climate of the tropics allows for high rates of species growth and survival, contributing to biodiversity.
Higher Primary Productivity: The high sunlight and precipitation levels in the tropics increase plant productivity, which supports a greater variety of herbivores and predators.
Define Biodiversity Hotspot and give an example.
A region that is rich in species and threatened by human activity. Example: The Amazon Rainforest.
How could nutrient availability reduce species diversity?
When nutrients like nitrogen and phosphorus are added in excess (through fertilizers), they can lead to competitive exclusion. This happens because fast-growing species (like certain algae or plants) outcompete slower-growing species when nutrient levels are high.
Example : in aquatic environments, excess nutrients can lead to eutrophication, where algae blooms occur, reducing light and oxygen in the water and leading to lower species diversity.
How do evapotranspiration rates relate to diversity patterns?
High evapotranspiration indicates abundant water availability and a productive environment, supporting greater biodiversity.
Essentially, more water availability supports more plant growth, which in turn supports more herbivores and predators.
Describe the relationship between area and species richness.
Generally positive; larger habitats tend to have more species due to diverse microhabitats and ecological niches.
Additionally, larger areas can support larger populations, reducing the risk of species extinction
Explain the relationship between island size and species richness.
Larger islands tend to have higher species richness due to more resources and habitats, supporting larger populations.
Larger islands also support more individuals, which can reduce extinction rates, thus maintaining higher species diversity.
Explain the relationship between island distance from the mainland and species richness.
Closer: Islands that are closer to the mainland generally have higher species richness because they are more accessible for species to colonize. Higher immigration rates from the mainland lead to greater species diversity on islands near the mainland.
Distant: Islands that are farther from the mainland have lower species richness because the immigration rate is slower, and species have a harder time reaching the island. These islands are also more likely to experience higher extinction rates.
Describe the intermediate disturbance hypothesis and give an example.
Low Disturbance: In environments with low disturbance, dominant species may outcompete others, leading to lower species diversity.
High Disturbance: In environments with high disturbance (e.g., frequent fires, storms), many species are excluded, especially those that are slow-growing or vulnerable to frequent changes.
Moderate Disturbance: Intermediate levels of disturbance allow both fast-growing species and slow-growing, competitive species to coexist, leading to higher diversity.
An example that supports this hypothesis comes from the work of Lubchenco, who manipulated snail density in intertidal pools. When an intermediate number of snails were present, more algal species were observed. The snails created disturbances that prevented any one algal species from dominating, allowing for greater species diversity.
Define Evapotranspiration.
The sum of water evaporated from the soil and transpired by plants, occurring in warmer, wetter climates.
Explain the Island Equilibrium Model.
This model suggests that larger islands support more species because they have more resources and habitats, which can accommodate more species.
Define Ecological Succession.
The process by which the species composition of a community changes over time.
Define Primary Succession.
The development of communities in habitats initially devoid of plants and organic soil, such as sand dunes or lava flows.
Define Secondary Succession.
The development of communities in habitats that have been disturbed but still contain organic soil.
Define Pioneer Species.
species that are first to colonize new habitats created by a disturbance. (Usually referring to species like bacteria, lichen, moss, or those that are able to survive harsh, barren environments after primary succession. ) Also used to describe species in secondary succession that are able to grow quickly and are often nitrogen fixers
Define Climax Community.
The final stage of ecological succession where the community is stable with consistent species composition and interactions.
Define Resistance.
Ability to maintain structure and function in the face of potential disturbance.
Define Resilience.
Ability to recover from disturbance and return to its pre-disturbed state.
Define Facilitation in ecological succession.
The presence of one species increases the probability that a second species can become established.
Define Inhibition in ecological succession.
One species decreases the probability that a second species will become established.
Define Tolerance in ecological succession.
The probability that a species can become established depends on its dispersal ability and ability to persist under environmental conditions.
Differentiate between primary and secondary succession.
Primary Succession occurs in habitats that are initially devoid of plants and organic soil. It typically happens in places like bare rock, sand dunes, or lava flows where there is no existing soil. The first species to colonize these areas are pioneer species like lichen and moss.
Example: The recovery of life on an island after a volcanic eruption, such as the Krakatoa eruption in 1883.
Secondary Succession occurs in habitats that have been disturbed but still contain organic soil. The disturbance might be something like a forest fire, agricultural abandonment, or logging. Since soil is still present, secondary succession is much faster than primary succession. Example: the regrowth of vegetation in the Virginia Piedmont region after farming or disturbance.
Differentiate between resistance and resilience.
Resistance refers to an ecosystem’s ability to maintain its structure and function in the face of potential disturbances. It’s the ability to withstand change without losing its key characteristics. Resilience refers to an ecosystem’s ability to recover from disturbances and return to its pre-disturbed state. It’s about how quickly the ecosystem can bounce back after a disturbance.
Explain how biodiversity impacts ecosystem stability.
Biodiversity enhances ecosystem stability because ecosystems with higher species diversity tend to have more complex interactions among species, which helps them recover more effectively from disturbances. A study on invertebrate herbivores and predators showed that greater species richness in experimental plots led to more stable ecosystems. High biodiversity means that a greater variety of species can play different roles in maintaining the ecosystem, making it more adaptable and resilient to changes or disturbances.
Why do early successional species possess different adaptations? What are those adaptations?
Tend to possess adaptations that allow them to quickly colonize disturbed or barren environments.
Adaptations: High seed production (with small seeds that can be dispersed by wind or animals.) Fast growth rates (to rapidly take advantage of available resources.) Low shade tolerance, (since they need to survive in environments with little to no canopy cover.)
Why do late successional species possess different adaptations? What are those adaptations?
Possess adaptations for stability and persistence in more mature, competitive environments.
Adaptations: Larger seeds (that require animals for dispersal.) Slow growth rates (but a longer lifespan.) High shade tolerance,( allowing them to thrive in environments with more competition for light.)
Why is it difficult to observe succession in most ecological communities?
It occurs over long time periods, often hundreds to thousands of years, so it’s difficult to observe the entire process within a human lifetime.
Additionally, many ecosystems are subject to disturbances (like fires, storms, or human activities) that can interrupt or alter the natural succession process. These disturbances may lead to partial succession or even a resetting of the successional process.
How is community resilience different from community resistance?
Community resistance refers to an ecosystem’s ability to maintain its structure and function despite disturbances. It means that the ecosystem does not change significantly when faced with a disturbance.
Community resilience, on the other hand, refers to the ability of the community to recover and return to its original state after being disturbed. While resistance is about withstanding disturbances, resilience is about bouncing back after one has occurred.
Explain the Biomass Accumulation Model.
Describes stages through which forest ecosystems pass as they recover after a disturbance. The Reorganization phase, Aggradation phase, Transition phase and Steady-state phase.
Define the Reorganization phase.
The ecosystem loses biomass and nutrients as the community begins to reorganize.
Define the Aggradation phase.
Biomass and nutrient levels increase, reaching their peak as the ecosystem matures.
Define the Transition phase.
Biomass levels begin to decline after reaching the peak during the aggradation phase. This is because resources may become depleted, and some species may die off, making way for new dynamics in the ecosystem.
Define the Steady-state phase.
Biomass fluctuates around a stable mean as the community stabilizes.
Why does biomass level off or decrease during the transition phase?
Because of competition for limited resources, the natural death of certain species, and changes in the ecosystem’s structure that can lead to a reduction in overall biomass until a new equilibrium is reached.
What are the Necessary Criteria for Character Displacement?
- Differences in character are greater in sympatry than allopatry.
- Differences did not derive from different founder groups.
- Differences between sympatric and allopatric populations have genetic basis.
- Variation in the character must have a known effect on use of resources.
Define Niche Partitioning.
Two or more species coexist while sharing resources in a way that reduces niche overlap.
Define Character Displacement.
When niche overlap is high, competition is high. Thus, individuals in a population that can better utilize resources will be selected for. They evolve different traits over time to reduce competition.
Example: Warbler species. In areas where both the Pine Warbler and Yellow-throated Warbler live together, they exhibit differences in their feeding habits and body size, enabling them to avoid competition for food. These differences are more pronounced when the species are sympatric (living in the same area) than when they are allopatric (living in separate).
Define Fundamental Niche.
Set of conditions under which an organism can survive and reproduce.
Define Realized Niche.
Set of conditions that are actually used by an organism (or population) considering its interactions with other organisms (including predation and competition)
Define Habitat Range.
The place or physical setting that an organism lives in. The habitat of an organism is determined by its niche.
What does allopatric mean?
Living in separate.
Define Habitat Range.
The place or physical setting that an organism lives in. The habitat of an organism is determined by its niche.
Define Niche Range.
The range of abiotic and biotic conditions it can tolerate as well as the interactions it has with predators, competitors, parasites, and mutualists.
Define Geographic Range.
The area that a species could be found during its lifetime.
Define Niche.
An organism’s role within its ecological community.
Who first defined abiotic and biotic factors and why?
Grinnell (1917) to better understand the distribution of California Thrashers in relation to physical (abiotic) environment factors.
What was a niche originally defined as?
Was a space into which a statue was placed.
How might urbanization impact a species’ ecological niche?
It can alter the availability of resources (such as food, water, shelter), introduce new competitors, predators, or diseases, and change abiotic factors like temperature, light, and air quality. Urbanization can create fragmented habitats, force species to adapt to new environments, or displace species that cannot adapt to the new conditions.
Example: Urban heat islands might push species that prefer cooler temperatures out of the area, while certain urban-adapted species like pigeons or raccoons might thrive.
Can an organism influence its own niche? If so, how?
Yes, an organism can influence its own niche. This is often seen through behaviors that modify the environment or the resources it uses.
Example: Beavers build dams, which can change the landscape by creating wetlands and altering water flow, thus influencing the availability of resources for other species.
What might some consequences of not understanding the concepts of niches be?
It could have consequences like conservation, resource management, and invasive species control. Species could be poorly managed, leading to habitat destruction or mismanagement. It could lead to the introduction of invasive species that outcompete native species, disrupting ecosystems. Biodiversity could be harmed due to inaccurate predictions about species’ needs and tolerances, leading to poor planning for conservation efforts.
Define ecological niche and differentiate from the term habitat.
An ecological niche refers to the role and function of an organism within its ecological community, including how it interacts with both biotic (other organisms) and abiotic (environmental) factors. This encompasses where the species lives, what it eats, when it feeds, how it reproduces, and its interactions with other species.
A habitat, on the other hand, is simply the physical space or place where an organism lives. While the habitat is the ‘address’ of the organism, the niche is its ‘profession’ or role in the environment.
Describe Gause’s Competitive Exclusion Principle and give an example.
States that two species competing for the same limited resources cannot coexist indefinitely. One species will eventually outcompete the other, leading to the exclusion of the less competitive species.
Example: The protozoan species Paramecium aurelia and Paramecium caudatum. When grown together in the same environment, P. aurelia outcompetes P. caudatum, leading to the exclusion of the other.
Explain the concept of niche partitioning and give an example.
Niche partitioning occurs when two or more species coexist in the same habitat by utilizing different resources or utilizing the same resources at different times, reducing direct competition.
Example: Warbler species living in the same tree. Each species of warbler feeds in different parts of the tree to avoid competition, thus partitioning the niche and enabling them to coexist.
How could two species occupy the same niche without leading to exclusion?
Through niche partitioning. This happens when the species divide the resources in some way (through spatial, temporal, or resource partitioning) so that they don’t compete directly.
Example: Two species of mice may occupy the same habitat but one may be nocturnal and the other diurnal, thus avoiding direct competition for food.
Differentiate between semelparity and iteroparity. Give examples of semelparous and iteroparous organisms.
Semelparity: Organisms reproduce once and then die.
Example: Salmon and periodic cicadas.
Iteroparity: Organisms reproduce multiple times during their life.
Example: Lions and humans.
Explain the “grandmother hypothesis”
Suggests that human menopause or ancestral females evolved because older females contribute to the survival of their grandchildren, enhancing the fitness of their genes. This is seen in orcas, where older females lead the pod and improve survival during lean years.
Explain the experiments that Endler and Reznick conducted on guppies in Trinidad.
They studied how predation influences guppy life history. They transplanted guppies between high-predation (low elevation) and low-predation (high elevation) pools in Trinidad. Thye found that in High Predation Guppies matured earlier, reproduced more frequently, and had smaller offspring (faster life history). In Low Predation areas Guppies matured later, had fewer but larger offspring (slower life history). The result was that Predation pressures shape life history strategies, with high predation favoring fast reproduction and low predation favoring larger, slower reproduction.
Exponential and Geometric models reveal similar population increases over time. Both J curves, how do their data differ?
Exponential data is based on continuous data whereas geometric uses discrete.
