Unit 5 Study Review

Provide four examples of life history traits that could be measured to describe an organism’s life history

When reproduction begins, reproduction frequency, offspring amount per reproduction, organism lifespan

Explain why organism face evolutionary trade-offs

Energy and resources can only be used once, so using it for reproduction or survival means the other loses that resource

Two examples of evolutionary trade-offs and their influence on each other

Using nutritional value for pregnancy takes it away from the mother. Having many offspring means fewer resources for each individual

What are two major sources of genetic variation in populations?

Mutation and sexual reproduction

What are two reasons that a change in DNA sequence may not result in a change in phenotype

A mutation can occur in a non-coding region, or the mutation in the coding region doesn’t actually change the protein

Briefly describe the five assumptions of the Hardy-Weinberg equilibrium

No mutation - No change in DNA sequence

Random mating - mating doesn’t revolve around a specific pattern

No gene flow - No individuals immigrating or emigrating

No selection - All individuals have an equal chance at surviving and passing genes

Infinite population size - Population restrictions don’t limit genetic variations

If a population that is in Hardy-Weinberg equilibrium has the allele frequencies p and q at a locus, what are the expected genotype frequencies of the heterozygotes and homozygotes in the population?

p² = 25%, q² = 25%, 2pq = 50%

If you know the frequency of allele p, what equation would you use to determine the frequency of allele q?

q = 1 - p

What equation would you use to calculate the expected genotype frequencies in the population?

p² + q² + 2pq = 1

Describe three ways a population might violate the Hardy-Weinberg equilibrium assumption of random mating

Inbreeding, Assortative Breeding, Isolation by DIstance

Describe three ways a population might violate the Hardy-Weinberg Equilibrium assumption of random mating.

Inbreeding, Assortative Breeding, Isolation by Distance

Describe three modes of selection that can be observed at the phenotypic level in a population.

Directional Selection - When one extreme or the other of a phenotype is favored.

Disruptive Selection - When both extremes, but not the intermediate of a phenotype is favored

Stabilizing Selection - When only the intermediate of a phenotype, not either extreme, is favored

What are two mechanisms that can lead to balancing selection?

Frequency-Dependent Selection and Heterozygote Advantage

By what mechanism is the allele for sickle-cell disease maintained in human populations?

Heterozygote Advantage

Briefly describe the two components that make up species diversity in a community.

Species Richness - The total variation of species in a community

Relative Abundance - The percentage of a species when compared to all others in a community

What index could you use to compare the species diversity of two communities?

Shannon Diversity Index (H), with higher numbers (H=1.39 over H=0.71) meaning higher diversity

What are two benefits of diversity in communities

Higher diversity can prevent the establishment of introduced species. Higher diversity can lead to greater recovery to environmental distress.

Briefly describe five types of species interactions and classify them as negative (-/-), exploitative (+/-), or positive (+/+ or +/0).

Predation - when a predator eats its prey (+/-)

Parasitism - one organism gains nourishment from another organism (+/-)

mutualism - both members benefit (+/+)

commensalism - one individual benefits while the other is unharmed (+/0)

herbivory - an organism eats parts of plant or algae (+/-)

Provide four examples of an ecological disturbance.

Storms, fires, flooding, droughts

Describe the relationship between species diversity and low, moderate, and high levels of disturbance in regard to the intermediate disturbance hypothesis

Low - competitive exclusion takes over leading to low diversity

Moderate - sets back dominant species to allow peak diversity

High - Intense and frequent disruptions leads to low populations and diversity

What is the main difference between energy and chemical elements in terms of their interaction with ecosystems?

Energy is transformed until it is eventually lost as heat, chemical elements are repeatedly recycled through the biotic components.

Describe which trophic levels decomposers interact with.

Provide the inorganic matter that primary consumers require. Feed on primary consumers corpses. Breaks down the corpses of all other trophic levels.

Provide an example of a decomposer.

Fungi

List three factors that can limit ecosystem productivity.

Light, Nutrient, Water

Which has the highest production efficiency: mammals/birds, insects/microorganisms, or fish? Which has the lowest? 

insects/microorgansims; mammals/birds

What is the average trophic efficiency at each trophic level?

Primary Producers - 1-5%

Primary Consumers - 10%

Secondary Consumers - 10%

Tertiary Consumers - 10%

What percentage of net primary production is available to primary consumers? To secondary consumers? To tertiary consumers?

10%; 1%; 0.1%

What are the implications of trophic efficiency for feeding the world’s human population?

Roughly 10% is transferred from one trophic level to the next, with 90% lost as heat and metabolic maintenance

Briefly explain why studying communities is important for understanding and potentially preventing zoonoses.

Because diseases spread through complex interactions between species.

Provide four examples of intraspecific mechanisms that regulate population growth. For each mechanism, briefly describe how it regulates the population.

Disease - Pathogens and parasites spread easily due to close proximity

Intrinsic Factors - Chemical consequences of overpopulation can include birthing patterns, and increase stress

Competition - Individuals of species use the same resources, taking them away from each other

Territoriality - Physical defense for space pushes out individuals who lose access to resources and mating

How do genetic drift, founder effect, and bottleneck effect relate to population size? 

How do these processes cause a change in the gene pool of a population?

genetic drift - The population size isn’t too affected, but the gene pool becomes less diversified, especially in smaller populations

founder effect - creates a separate small population that can lead to a heavily skewed gene pool

bottleneck effect - an event occurs that drastically reduces the population size, leaving the gene pool randomized and heavily limited.

How might gene flow act in opposition to selection to influence the genetic composition of a population?

The gene pool gets pulled in an opposite direction with gene flow, often creating situations of maladaptive alleles.

Briefly describe the difference between the bottom-up model and top-down model of community organization. 

For each model, explain how changing the abundance of the highest or lowest trophic level would affect biomass at the other levels.

Bottom-up is measured by the abundance of resources toward primary producers, and Top-down is measured by the amount of predation on other consumers.

Top predators eating more herbivores would increase the plant biomass, while less top predators eating less herbivores would decrease plant biomass.

Plant biomass increasing means more resources for herbivores which means more resources for top predators. Lower biomass means less resources for all.

Explain how foundation species, keystone species, and ecosystem engineers have large effects on their communities. 

Provide an example species for each term.

Foundation Species - Provide stable conditions for their communities, such as coral providing shelter and food.

Keystone Species - Heavily affect species diversity despite low abundance, such as grey wolves that act as predators that keep herbivory in check.

Ecosystem Engineers - Modify, maintain, or create physical habitats for communities, such as beavers creating dams that create new habitats.

Describe the equations for NPP and NEP including a description of R_a and R_T.

NPP = GPP - R_a. NPP is net primary production determined by gross primary production minus the energy needed for cellular respiration in primary producers.

NEP = GPP – R_T. NEP is net ecosystem production determined by gross primary production and the energy needed for cellular respiration in all organisms.

Why are NPP and NEP useful metrics for understanding ecosystems?

NPP measures the actual amount of chemical energy and organic matter. NEP measures the carbon balance in an ecosystem, with a positive NEP being a carbon sink, meaning carbon is absorbed at a faster rate, while a negative NEP being a carbon source, meaning carbon is released faster.

Explain the difference between r-selection and K-selection. Include a description of the population densities each type of selection is associated with.

r-selection - associated with low and fluctuating densities, prioritizing high growth rates and large amounts of offspring, common in rodents and insects.

K-selection - associated with high, stable population densities, prioritizing high investments in limited offspring, common in whales and humans.

Explain how r-selection and K-selection relate to the logistic growth model.

r-selection means the early part of the logistic growth model where species excel in small populations with high resources, K-selection is the leveled out part of the logistic growth model where species thrive with scarce resources and large populations.

Provide two life history characteristics that are associated with r-selection and K-selection

r-selection - many offspring with low parental care, short lifespan

K-selection - low offspring with high parental care, long lifespan