Biodiversity and Ecology Exam 2
Unit 5: Biodiversity and Conservation Biology
Definitions to Know
Biodiversity: The variety of life in the world or a particular habitat.
Species Diversity: The number of different species and the abundance of each species in a given area.
Genetic Diversity: The total number of genetic characteristics in the genetic makeup of a species.
Ecosystem Diversity: The variety of ecosystems in a given place.
Endemic: Native species confined to a specific geographical area.
Conservation Biology: A field of science that focuses on the protection and management of biodiversity.
Fragmentation: The process of breaking larger habitats into smaller, isolated patches.
Invasive Species: Non-native species that spread widely and cause harm to ecosystems.
Biodiversity Hotspot: Regions that are both a significant reservoir of biodiversity and under threat from humans.
Conservation Hotspot: Areas identified for their ecological significance and urgency for conservation efforts.
Distribution of Biodiversity
Taxonomy: Biodiversity is not evenly distributed across taxonomy; certain taxonomic groups may exhibit higher diversity.
Geography: Biodiversity is also uneven geographically. For example, tropical regions typically have higher biodiversity than temperate regions due to stable climates and ecological interactions.
Reasons for Decline in Biodiversity
Habitat loss and degradation: Greater in terrestrial ecosystems.
Climate change: Affects both marine and terrestrial ecosystems.
Pollution: Often more impactful in aquatic environments.
Overexploitation of resources: This can occur in both marine and terrestrial environments.
Importance of Biodiversity
Ecosystem Services: Supports ecosystem productivity, resilience, and function.
Cultural Significance: Contributes to cultural identities and practices.
Medicinal Resources: Many medicines are derived from plants and animals.
Economic Benefits: Contributes to agriculture, forestry, and fisheries.
Current Extinction Rates
The current extinction rate is significantly higher than historical rates, often referred to as the sixth mass extinction.
Threats from Habitat Fragmentation
Fragmentation limits species' movement, reduces population sizes, and isolates populations, increasing extinction risk.
Unit 6: Population and Conservation Genetics
Key Terms
Population: A group of individuals of the same species living in a specific area.
Evolution: Change in the heritable characteristics of biological populations over successive generations.
Quantitative Trait: A trait that is determined by multiple genes and is measured on a continuous scale.
Polygenic Trait: A trait that is influenced by multiple genes.
Phenotypic Variation: The observable differences in traits among individuals in a population.
Genetic Variation: Differences in DNA among individuals, which can affect traits.
Phenotypic Plasticity: The ability of an organism to change its phenotype in response to environmental conditions.
Heritability: The proportion of observed variation in a particular trait that can be attributed to inherited genetic factors.
Natural Selection: The process by which organisms better adapted to their environment tend to survive and produce more offspring.
Strength of Selection: The magnitude of natural selection acting on a trait.
Response to Selection: The change in the average value of a trait over time due to selection.
Allele Frequencies: The relative frequency of an allele at a genetic locus in a population.
Genotype Frequencies: The proportion of different genotypes in a population.
Gene Pool: The total collection of genes and alleles in a population.
Hardy-Weinberg Equilibrium: The condition under which allele and genotype frequencies remain constant in a population if no evolutionary forces act on it.
Mutation: A change in the DNA sequence of an organism's genome.
Migration: Movement of individuals into or out of a population.
Gene Flow: Transfer of genetic material between populations.
Genetic Drift: Random changes in allele frequencies in a population.
Sampling Error: The error caused by observing a sample instead of the whole population.
Fixation: When all individuals in a population carry only one allele for a particular gene.
Bottleneck: An event that drastically reduces the size of a population, leading to a loss of genetic diversity.
Founder Effect: Genetic difference that arises when a small group of a population becomes isolated from the larger population.
Random Mating: Mating that occurs without regard to the genotypes or phenotypes of the individuals.
Assortative Mating: A non-random mating pattern where individuals with similar phenotypes are more likely to mate.
Inbreeding: Mating between closely related individuals.
Inbreeding Depression: Reduced biological fitness due to inbreeding.
Heterozygosity: The presence of different alleles at one or more loci.
Questions
Continuous Variation from Discrete Alleles: Describe how skin color varies continuously despite being influenced by discrete alleles (e.g., multiple genes contributing to shades along a spectrum).
Head Circumference: Discuss whether this trait exhibits genetic variation or phenotypic plasticity.
Natural Selection and Evolution: Examine if natural selection can occur without resulting in evolution and vice versa, with explanations.
Strength vs. Response of Selection: Compare and provide numerical examples illustrating which is greater.
Graphical Features of Genetic Drift: Identify characteristics from simulation graphs that distinguish population sizes.
Processes Affecting Hardy-Weinberg Equilibrium: List and analyze five processes affecting H-W equilibrium, their impact on allele frequency, and potential for adaptation.
H-W Equilibrium Steps: Step through a process to assess H-W equilibrium from genotype frequencies.
Assessing Genotype Frequencies: Determine if a specific set of genotype frequencies is feasible for given allele frequencies.
Distribution of Bill Length in Finch Populations: Create sketches for the expected distributions after generations of selection for larger bill size, considering heritability.
Influence of Genetic Drift and Gene Flow: Discuss how these processes influence genetic diversity and differentiation in populations.
Fragmentation Effects: Assess how genetic drift and gene flow endanger populations within fragmented landscapes.
Sampling Error Example: Provide a practical example of sampling error outside class topics.
Allele Fixation: Explain what it means for an allele to reach fixation and whether frequencies can change thereafter.
Inbreeding Effects: Discuss the implications of inbreeding on genetic diversity.
Mutts vs. Purebreds: Explore reasons for longevity differences between mixed breed and purebred dogs.
Conservation Corridors: Outline the goals and effects of habitat corridors on genetic structure, referencing prairie chickens as an example.
Captive Breeding Decisions: Justify the focus on preserving limited species rather than multiple small populations in conservation efforts.
Note
These concepts are critical in understanding population dynamics and conservation strategies.
Experiment to Test Heritability of Swimming Speed in Atlantic Salmon
Objective: To test the heritability of swimming speed in Atlantic salmon.
Method:
Select a sample population of Atlantic salmon to assess swimming speed.
Measure and record the swimming speed of individual salmon at a young age (e.g., juvenile stage).
Conduct breeding experiments to produce a controlled second generation using both parents from the fastest individuals and both parents from slower individuals.
Measure swimming speeds in the offspring and compare with the parental speeds.
Expected Results:
(a) If heritability is high, offspring swimming speeds will closely resemble the parental speeds, leading to a steep positive correlation graph, indicating strong genetic influence.
(b) If swimming speed is not heritable, offspring swimming speeds will be randomly distributed and not correlate with parents, resulting in a scatter plot without a discernible trend.
Ladybug Distastefulness Experiment
Strength of Selection Calculation:
Initial mean distastefulness = 4.8 ATU
Mean after predation = 6.8 ATU
Change in mean distastefulness = 6.8 - 4.8 = 2.0 ATU
Strength of selection (S) can be calculated as the difference between mean before and after predation related to the mean initially:
S = (Mean_after - Mean_initial) / Mean_initial = (6.8 - 4.8) / 4.8 ≈ 0.42.
Heritability Calculation (h^2):
Offspring mean distastefulness = 5.3 ATU, meaning that the heritable increase would be associated with the selection measure.
The formula for heritability could incorporate the response to selection and strength of selection:
h^2 = (Mean_offspring - Mean_initial) / S = (5.3 - 4.8) / 2.0 = 0.25.
Earlobe Gene Frequencies
Population Data: 500 individuals total:
120 homozygous dominant (AA)
230 heterozygous (Aa)
150 homozygous recessive (aa)
(a) Frequency of the dominant allele, p = (2(120) + 230) / (2*500) = 0.58.
(b) Allele frequency calculations to check Hardy-Weinberg equilibrium:
p^2 + 2pq + q^2 = 1
If p = 0.58 (AA), q = 0.42 (aa, derived as 1-p), calculate:
Expected AA = (0.58)^2 = 0.3364 => 337
Expected Aa = 2pq = 2(0.58)(0.42) = 0.4872 => 487
Expected aa = (0.42)^2 = 0.1764 => 176
Compare with observed frequencies. If expected matches observed, in H-W equilibrium.
Sickle-Cell Allele Frequencies
Allele Frequency Calculation:
(a) Frequency of HbA = 1 - HbS frequency = 1 - 0.04 = 0.96.
(b) Predicted percentage of heterozygotes: 2pq = 2(0.96)(0.04) = 0.0768, or 7.68%.
Cystic Fibrosis Frequency Among Newborns
Calculated Frequency:
Frequency of CF allele (q) = 0.02, the frequency of homozygous recessive (q^2) = (0.02)^2 = 0.0004 or 0.04% among newborns.
Change in Allele Frequency Over Generations
Expected Change:
Both regular homozygous and heterozygous individuals maintain fitness of 1.
Fitness of cystic fibrosis homozygous = 0. Conclusion: The frequency of the CF allele is expected to decrease significantly over the generation due to natural selection favoring the normal alleles.
These analyses employ key concepts in population genetics and natural selection, serving to illuminate genetic principles underlying evolutionary biology in the context of varying traits and heritability.
Unit 7: Population Dynamics
Key Terms with Examples
Allee Effect: A phenomenon where individuals have a more difficult time surviving or reproducing if the population size is too small, such as when small populations of African elephants face challenges in mating due to insufficient numbers.
Demographic Stochasticity: Variability in population growth due to random differences among individuals, such as random variations in birth rates among sea turtle hatchlings caused by environmental factors.
Environmental Stochasticity: Variability in population growth due to unpredictable changes in the environment, for example, forest fires that can drastically reduce the population of local species like koalas.
Population Dynamics: The study of how populations change over time, exemplified by the dramatic fluctuations of the moose population on Anticosti Island due to predation and resource availability.
Immigration: The movement of individuals into a population, such as the arrival of migratory birds into a breeding area during the spring.
Emigration: The movement of individuals out of a population, as seen when young salmon leave their natal rivers in search of larger bodies of water to inhabit.
Intrinsic Effects: Effects that stem from the biological characteristics of individuals, like the genetic predisposition of Cheetahs to have larger litter sizes compared to other large cats.
Exponential Growth: Growth pattern where the population size increases at a constant rate; an example is the rapid multiplication of bacteria in a nutrient-rich environment.
Carrying Capacity (K): The maximum number of individuals an environment can support sustainably, for instance, a lake with a carrying capacity of 1000 fish due to limited food and space.
Density Independent: Factors that affect population size regardless of density, such as a hurricane that affects species like sea oats equally irrespective of their local population size.
Density Dependent: Factors that have an increasing effect as population density increases; an example includes competition for food among rabbits in a high-density area.
Logistic Growth: Population growth that levels off as the population approaches carrying capacity, illustrated by the growth pattern of gray wolves as they adapt to limited food resources in a national park.
Intrinsic Rate of Increase (r): The rate at which a population increases under ideal conditions, exemplified by housefly populations that can grow rapidly in optimal environments.
Age Structure: The distribution of individuals among different ages in a population, like the age structure seen in human populations, where a large proportion of the population may fall into younger age categories.
Age Class: A group of individuals of the same age; for example, all one-year-old juvenile deer in a forest.
Survivorship: The proportion of individuals that survive to a certain age, such as the survivorship of oak trees, which have a high likelihood of reaching old age.
Survivorship Curve: A graph showing the number or proportion of individuals surviving at each age, like type I survivorship seen in humans, where most individuals live to middle age or beyond.
Fecundity: The potential reproductive capacity of an individual or population, illustrated by insects such as fruit flies, which can produce hundreds of offspring in a short period.
Life Table: A table that summarizes the mortality and survival of a population; for example, a life table for sea turtles detailing survival rates across different age classes.
Life History: The series of changes undergone by an organism, like the life history of salmon, which includes stages from eggs to fry to adult fish returning to spawn.
Allocation: How organisms distribute their resources to growth and reproduction; for instance, plants may allocate more resources to root development in nutrient-poor soil.
Trade-off: Balancing different traits that influence reproductive success, where investment in one trait may reduce investment in another, such as birds choosing between larger offspring or producing more smaller offspring.
Dispersal: The movement of organisms from one location to another, like the spread of dandelion seeds by the wind.
Metapopulation: A group of spatially distinct populations, such as isolated prairie dog colonies that exist in fragmented grasslands.
Rescue Effect: When immigration from a larger population helps sustain small, isolated populations, for instance, when birds from a nearby habitat migrate to bolster a declining local colony.
Population Viability Analysis: A method used to assess the likelihood that a population will survive over a given time period, often applied in conservation efforts for species such as the Florida panther.
Demographic Risks of Small Population Size
Inbreeding Depression: Small populations are susceptible to inbreeding, leading to reduced genetic diversity and fitness. For instance, Florida panthers have experienced inbreeding due to small population sizes, resulting in health issues.
Demographic Stochasticity: Small populations are affected more by random events impacting birth and death rates, such as a few bad years of reproduction greatly affecting endangered species like the California condor.
Vulnerability of Small Reserves
Species confined to small reserves can become vulnerable due to limited resources, reduced genetic diversity, and increased exposure to threats such as disease or human encroachment, as seen in island species like the Hawaiian honeycreepers.
Basic Processes Affecting Population Size
Births: Increase population size, such as the growing number of domestic cats in urban areas due to high reproduction rates.
Deaths: Decrease population size, as seen in melting polar ice affecting the survival of polar bears.
Immigration: Introduces new individuals like newcomer wolves enriching genetic diversity in a pack.
Emigration: Removes individuals, exemplified by young elephants leaving their natal herds.
Exponential Growth Equation: N(t) = N(0)e^(rt) where N(t) is the population size at time t, N(0) is the initial population size, r is the intrinsic rate of increase, and t is time.
Incorporating Carrying Capacity
Logistic Growth Equation: dN/dt = rN(1 - N/K)
When N < K, the growth is similar to exponential. The population experiences slower growth as it approaches K.
Density-dependent Processes Limiting Growth
Competition for resources, like in trees competing for sunlight.
Predation, where increased predator populations reduce prey numbers, as observed in lynx and snowshoe hare cycles.
Disease transmission, which spreads more easily among densely populated mice.
Population Models
Exponential Model: More appropriate for new bacteria colonizing the nasal passages.
Logistic Model: More suitable for a stable population of elephants, the human population since 1900, newly invasive plant species, and long-lived lab fruit flies.
Population Size Changes
Calculate using the exponential growth equation: N(t) = N(0)e^(rt); apply for logistic growth considering K.
Comparison of Growth Rates
Ranking for ΔN/Δt and r at different time points can vary based on environmental factors affecting growth rates.
Carrying Capacity Exceedance
Populations can temporarily exceed K due to abundant resources but will face a crash once resources deplete, resembling boom-bust cycles seen in locust plagues.
Metapopulation Recognition
Recognizing metapopulations is crucial for conservation as it informs reserve designs that account for habitat connectivity essential for species survival.
Habitat Fragmentation Effects
Fragmentation can isolate populations, diminishing genetic diversity and making them more susceptible to local extinction events, similar to patterns seen in fragmented forest habitats affecting amphibian species.
Individual Contributions to Population Size
Not all individuals contribute equally; for instance, dominant male lions may sire more offspring than others, impacting population dynamics.
Life Table Importance
Life tables provide insights into age-specific survival and reproductive rates, crucial for management plans of species like Atlantic salmon.
Maturation Rates and Vulnerability
Slow maturation leads to high vulnerability; for example, sea turtles take many years to reach reproductive age, making them vulnerable to overfishing and habitat loss.
Trade-offs in Life History
Trade-offs occur as organisms allocate resources; for example, rabbits might balance between size and number of offspring produced based on resource availability.
Increasing Population Growth Rate
Increase reproductive output through habitat restoration that supports breeding.
Enhance juvenile survival by establishing protective measures against predators.
Encourage immigration by creating corridors for movement between fragmented habitats.
Fecundity and Fitness
High fecundity does not guarantee high fitness; environments often limit survival rates, as in the case of species that produce numerous offspring but few survive.
Long-term survival in adverse conditions may not equate to high fitness due to competition for resources leading to trade-offs, linking to senescence theories in ecology.
The intrinsic rate of increase of 0.6 per generation indicates that the birth rate exceeds the death rate for this population. Specifically, there is a net growth, as the population is increasing with each generation.
To determine how many generations are needed for the population to more than triple in size, we can use the exponential growth formula:N(t) = N(0) * e^(rt)
We want N(t)/N(0) > 3, which implies:3 < e^(0.6 * t)
Taking the natural logarithm of both sides:ln(3) < 0.6 * t=> t > ln(3)/0.6 ≈ 1.83 generations.
Therefore, it would take at least 2 generations for the population to more than triple in size.
For the rabbits in Australia, starting with 24 rabbits and a per capita growth rate of 1.2 per year, we can again use the exponential growth model. The formula is:N(t) = N(0) * e^(rt)Substituting the values:N(5) = 24 * e^(1.2 * 5) = 24 * e^(6) ≈ 24 * 403.43 ≈ 9675 rabbits.
For the stray cats on CofC campus with a carrying capacity of 100, maximum intrinsic rate of increase (r max) of 1.4, initial population of 10, and a generation time of 5 years: Use the logistic growth equation.dN/dt = rN(1 - N/K)Starting from 10 cats in 2020, doing calculations every 5 years until 2035 will give:
2020: 10 cats
2025: 22 cats
2030: 30 cats
2035: 38 cats
Without specific graphs provided, a life-history tradeoff typically would be indicated in a graph where increasing clutch size leads to a decrease in offspring survival.
For the cricket frog eggs: (a) To predict how many frogs reach reproductive maturity, if we use a survivorship curve (assumption for this example): If the life table suggests a constant survival rate, calculate that percentage from total eggs. (b) The total offspring produced is calculated from the reproductive output noted in the life table for maturity years. (c) The type of survivorship curve can be determined by examining the survival data over time, likely reflecting Type III curve if many eggs survive, but few reach maturity.
For the cohort of 1000 lizards: Survival to 2010: 800 (80%)Survival to 2011: 200 (25% of 800)Survival to 2012: 40 (20% of 200)Survival to 2013: 20 (50% of 40)Constructing a life table with x = age, l(x) = survivors at age x, and m(x) = offspring per female. Based on reproduction in different years, calculate population growth using net reproduction rate R0 = Σ(lx * mx). An R0 greater than 1 indicates growth, less than 1 indicates shrinkage, and equal to 1 indicates stability.