BIO 211 Exam 5

What is evolution?

the change in frequency (relative abundance) of alleles (or phenotypes of a heritable trait) in a population over time (or from one generation to the next)

What evidence is there for evolution?

1\) Structural similarities (structural homology) imply common ancestry.• Fossil record• Extant species2\) Developmental similarities (developmental homology) imply common ancestry.3\) Genetic similarities (genetic homology) imply common ancestry.4\) Evolution observed• Artificial selection• Emergence of drug- and pesticide-resistant populations by natural selection

What are the four processes of evolution?

mutation, natural selection, genetic drift, gene flow

Mutation

structural change in genetic information (e.g., change in nitrogenous-base sequence of DNA = point mutation)• The mechanism by which new alleles (raw material for evolution) ariseRandom production of new alleles

Natural selection

occurs in a population when individuals with a favorable heritable phenotype (adaptation or adaptive trait) produce the most surviving offspring• This is the primary mechanism for evolution.Example of evolution by natural selection - pesticide resistance in insects and weedsExample of evolution by natural selection - change in bill size in the ground finch, Geospiza fortis)

Genetic drift

change in allele frequencies in a population due to chance• Potentially important mechanism of evolution in small populationsRandom changes in allele frequencies; most important in small populations

Gene flow

occurs when individuals immigrate or emigrate to a new populationMovement of alleles between populations;reduces differences between populations

potential positive and negative effects of mutations

• Non-harmful alleles have evolutionary potential, increasing the likelihood that population survives environmental change• Most have harmful or neutral effects on the individual

potential positive and negative effects of natural selection

• Adaptive heritable traits (and alleles) become or remain more common

potential positive and negative effects of genetic drift

• Loss of alleles increases extinction risk due to reduced evolutionary potential and increased likelihood of inbreeding depression• loss of alleles• Inbreeding depression - low average fitness in a population due to high frequency of individuals that are homozygous for a harmful (defective) allele

potential positive and negative effects of Gene flow

• Increased genetic similarities between populations• Increased genetic diversity in a population by adding alleles

Fitness

number of offspring produced by an individual relative to other members of the population

Founder effect

change in allele frequencies as a result of the migration of a small subgroup of a populationcan result when new population is formed by a few individuals

Genetic bottleneck

a sudden reduction in the number of alleles in a populationcan result when a large population is reduced to a small number of individuals

Inbreeding depression

low average fitness in a population due to high frequency of individuals that are homozygous for a harmful (defective) allele

What is speciation?

emergence of new species from an ancestral species

what criteria are used to distinguish species

• Reproductive isolation (Biological Species Concept)Reproductive isolation between populations (don't breed or produce viable, fertile offspring)• Morphological differences (Morphospecies Concept)Morphologically distinct populations• Genetic differences (Phylogenetic Species Concept)Genetic differences between populations(differences in DNA base sequences)

how do evolutionary processes influence speciation?

• Gene flow• Mutations• Natural selection

Allopatric speciation

speciation in geographically isolated populations

How can an understanding of evolution benefit humankind?

1\) Knowledge of genetic similarities (phylogenetic relationships) among taxa is used to identify:• model organisms in medical research• biological indicators of environmental health2\) Knowledge of the concept of natural selection can assist in:• developing strategies for combating pathogens and pests that are less likely to result in drug and pesticide resistance3\) To prevent extinctions, knowledge of effects of genetic drift and gene flow is used in: • designing breeding programs that maintain genetic diversity in captive populations• preserving and restoring habitat patches of sufficient size and proximity to maintain genetic diversity in populations

What is "ecology"

the study of how organisms interact with each other and non-living components of their environment

Why is the study of ecology important?

Ecology generates understanding of what determines the geographic distribution, abundance, and diversity of organisms. This allows us to:• preserve and restore populations and ecosystem services (e.g., maintain a sustainable fishery).• improve human health (e.g., disease ecology).• assess human impacts on the biosphere (e.g., effects of human-generated climate change)

What factors determine the geographic distribution and abundance (e.g., population size or density) of a species?

1\. Geographic origins2\. dispersal capacity3\. Abiotic (non-living) factors determining geographic distribution and abundance of a species include:• sunlight - required for photosynthesis• temperature - affects enzyme function and metabolic demands• water - dissolves and transports nutrients and other molecules• nutrients - required for biosynthesis• habitat (non-living forms) - a place to live4\. Biotic (living) factors determining geographic distribution and abundance of a species include:• prey availability• negative interactions (competition, consumption)• positive interactions

tropical wet forest

biome characterized by abundant trees; high species diversity and organism abundance are due to:• abundant sunlight• high temperature• high water availability (abundant precipitation)• abundant biotic resources

arctic tundra biome

biome characterized by low-lying plant growth forms; low species diversity and organism abundance are due to:• low amounts of sunlight• low temperature• low availability of water and nutrients (due to low precipitation and permafrost)Descending cold air warms up and absorbs water, resulting in low precipitation.

How is human land use affecting species diversity in terrestrial biomes?

1\) Natural biomes are being replaced by anthropogenic biomes, in which species diversity and biological production are dramatically reduced.unfavorable abiotic conditions for most species.2\) dispersal is reduced due to increased distance between favorable habitats (i.e., habitat fragmentation).3\) diminished regional species pool4\) reduces abundance of biotic resources.

In oceans and lakes, how do species diversity and abundance of organisms change across a depth and nutrient abundance gradient? Why do observed patterns occur?

1\) In oceans and lakes, organism abundance and species diversity are typically greatest: • in shallow water (littoral zone) where sunlight reaches the bottom and nutrients are replenished by streams or upwelling.

How are human activities affecting species diversity in aquatic biomes?

1\) Due to human activities, aquatic biomes are eliminated (e.g., drainage of wetlands) or degraded by inputs of pollutants.

What is population ecology?

ecological study that is focused on a population

Can you recognize an example of an investigation conducted at this level of ecological study?

What percentage of a sockeye salmon population can be harvested by humans each year, without causing a long-term decline in numbers?

Population

all individuals of one species that inhabit a geographic area (they can interbreed)

What is the long-term pattern in global human population change, and what associated ecological changes have occurred?

1\) Declining resource availability - from overconsumption/unsustainable use, and destruction of ecosystems2\) Degradation of the biosphere - from pollution3\) Climate change - increased greenhouse gas concentrations in atmosphere lead to higher temperatures, and greater frequency/intensity of droughts and storms 4\) Reduced ecosystem services - declining biological production and species diversity results in fewer natural resources, less air and water purification, and reduced carbon sequestration

Logistic growth

a model for predicting population change over time (assumption: begin with small population and abundant resources) Nt+1 = rmaxNt[(K-Nt)/K] + NtNt = population size at beginning of a time intervalrmax = intrinsic rate of increase (a constant value based on reproductive potential of the species)K = carrying capacity of the environment (a constant value based on estimate of maximum population size the ecosystem can support) Nt+1 = population size at next time interval

What ecological and biological factors limit population size/density and affect change patterns?

• Density-independent factors• Density-dependent factors• Life history strategies

Density-independent factor

magnitude of effect is unrelated to population density; usually an abiotic factor, including: • temperature - or another environmental factor that can either reduce (as a stressor) or increase population size • a physical disturbance - event that kills a high percentage of the population quickly (e.g., fire, severe storm)

Density-dependent factor

magnitude of effect increases with population density; usually a biotic factor, including:• competition for resources (food, habitat)• consumption (predation, parasitism)

Life history strategy

describes how an individual allocates resources to reproduction, growth, and survivorship• r-selected strategy - high fecundity (high rmax), low survivorship (flies)• K-selected strategy - low fecundity (low rmax), high survivorship) (humans)

How can knowledge of population ecology be applied to use resources sustainably and preserve populations?

1\) Knowledge of population ecology is used to establish optimal and sustainable harvest practices (e.g., fisheries and wildlife management)2\) Metapopulation theory is used to preserve populations (and prevent extinctions) in human-altered landscapesA well-managed landscape will support metapopulations that enable: • re-colonization of habitat patches following local extinctions• a stable total population size • gene flow to maintain genetic diversity in small populations

Metapopulation

a "population of smaller populations", partially separated by inhospitable habitat, but connected by migration (dispersal)

What is community ecology?

ecological study that is focused on a community

Can you recognize an example of an investigation conducted at this level of ecological study?

Which species do salmon interact with through consumer-prey interactions, and how are populations of salmon and other species affected?

Community

all organisms occupying the same geographic area (they can interact)

In the profiled case study, what ecological factors caused increased population densities of ticks in forest or woodland habitat (increasing risk of Lyme disease in humans)?

Lyme disease - caused by bacterium (Borrelia); ticks are vectors • Infection rates in humans are increasing. Knowledge of interactions in biological communities helps us understand why.

What are the measures of community structure that we discussed?

1\) Species composition2\) Species richness3\) Population density

Species composition

the species constituting the community

Species richness

the number of species per unit of habitat area (a specific measure of species diversity)

Population density

the number of individuals of a species per unit of habitat area (a specific measure of abundance)

Commensalism

A relationship between two organisms in which one organism benefits and the other is unaffected• This "positive interaction" increases species richness in a community.

Mutualism

• This "positive interaction" increases species richness in a community. • Examples include relationships between 1) pollinators and flowering plants, 2) mycorrhizal fungi and plant roots, 3) gut bacteria and animal host

Competition

reduces species richness in a community• A niche is the range of resources a species can use, or conditions it can tolerate.• Niche overlap indicates intensity of interspecific competition• Competitive exclusion of one species may occur if two species occupy the same niche.• Competitive release - species with overlapping niches may coexist if the resource they compete for is not in limited supply (e.g., when population densities of competing species are all low).

Consumption

• Tends to reduce prey or host population densities

Determinants of community structure

1\) In terrestrial ecosystems, the size of the regional species pool declines with increasing latitude.2\) Dispersal to a habitat (immigration) increases when similar habitat is nearby.3\) Abiotic factors• Nonliving resources (e.g., habitat) have positive effects on species richness.• Severe disturbances or stressors tend to reduce species richness.4\) Biotic factors (interspecific interactions)

Severe disturbance

(e.g., fire) removes most or all plant life from the area.• Very low species richness at this stage

Pioneer stage

First stage of primary succession that begins with hardy organisms that can grow and reproduce under adverse conditions.• Dominant plants - non-woody plants (r-selected life history strategies)• Species richness - low but increasing• Causes for increasing species diversity - minimal competition; plants improve soil quality and provide resources to consumers, commensals, mutualists

Intermediate stage

• Dominant plants - shrubs and small trees• Species richness - high and increasing• Causes for increasing species diversity - plants improve soil quality and provide resources to consumers, commensals, mutualists

Climax stage

• Plant community - tall trees• Species richness - high but no longer increasing and may be declining• Causes for stabilized or declining species diversity - intense competition among plants for light

What is ecosystem ecology?

ecological study that is focused on an ecosystem

Can you recognize an example of an investigation conducted at this level of ecological study?

How do interactions between salmon and other species influence energy and nutrient flow pathways in a stream?

Ecosystem

all organisms (biotic) and nonliving (abiotic) components of a geographic area (habitat differences often define ecosystem boundaries)

primary production

occurs when autotrophs capture energy in sunlight (or inorganic molecules) and transform it to energy (carbohydrates and other carbon-containing molecules) that can be stored and used by organisms

gross primary production (GPP)

total amount of energy captured by primary production per unit area and time (i.e., total autotroph production)

net primary production (NPP)

amount of GPP used for growth and reproduction (NPP = GPP - R). NPP represents energy in autotroph biomass.R = cellular respiration

In what terrestrial biome would NPP be highest? Why?

NPP is generally higher in ecosystems with high temperature, abundant water and sunlight (i.e., abiotic factors limiting photosynthesis)

In what type of aquatic habitat would NPP be highest? Why?

NPP highest in shallow water where sunlight reaches the bottom, and where nutrients (nitrogen, phosphorus) are abundant

How does energy flow through ecosystems?

1\) Consumers determine NPP flow pathway through trophic (feeding) interactions2\) With each trophic transfer, energy is lost (primarily by cellular respiration).3\) Production of consumers is limited by NPP. • Due to energy transfer inefficiencies, net production of consumers/heterotrophs (NP) is much lower than primary producer/autotroph production (NPP).• On average, net production (biomass) at one trophic level is only 10% of the trophic level below it.

How and why does net production (NP or biomass) differ at high and low trophic levels? Why is this knowledge useful?

On average, net production (biomass) at one trophic level is only 10% of the trophic level below it.

How does energy flow through ecosystems?

Energy flows through ecosystems in a one-way stream, from primary producers to various consumers

Using phosphorus as an example, how do nutrients cycle through ecosystems?

1\) For primary production to occur, autotrophs must absorb nutrients (e.g., nitrogen, phosphorus, carbon) from their environment. 2\) Nutrients are transferred to consumers (with energy) by trophic interactions.3\) Unlike energy, nutrients cycle through ecosystems.

How do humans alter ecosystem processes, and in doing so, reduce ecosystem services?• Energy flow• Nutrient cycling• Biomagnification of industrial pollutants

1\) Energy flow• Species at upper trophic levels require large amounts of food.• Due to habitat loss, food resources are increasingly insufficient to support their populations.• Loss of species at top trophic levels negatively affects species diversity and ecosystem services.2\) Nutrient cycling• Nutrient cycling in terrestrial ecosystems is altered by additions (e.g., fertilizer) and losses (e.g., by removing plants that absorb nutrients and hold soil in place).• NPP in an ecosystem declines when nutrient exports exceed imports.• Excessive nutrient inputs from terrestrial ecosystems cause increased NPP in aquatic ecosystems (eutrophication).• Aquatic species diversity declines due to resulting anoxia and high cyanotoxin abundance.3\) Biomagnification of industrial pollutants - body concentrations of heavy metals and synthetic organic chemicals increases with trophic level • These substances are lipophilic, and top-level consumers eat lots of prey over their long lifespan.

What is global ecology?

the study of interactions among organisms and abiotic components within the entire biosphere

Can you recognize an example of an investigation conducted at this level of ecological study?

How will climate change affect sockeye salmon geographic distribution and abundance?

Biosphere

the zone above, on, and below the earth's surface (i.e., subsurface) where life exists

What are the major reservoirs and transfer processes of the water cycle?

1\) Water cycles between reservoirs that include a) the atmosphere b) organisms c) earth surface and subsurface2\) Water transfer processes include: precipitation, evaporation, uptake and release by organisms, and surface and subsurface flo

How do human activities alter the water cycle, and how are human-induced changes to the water cycle affecting human welfare?

1\) Reductions in plant biomass and increases in air temperature alter the water cycle, leading to:• increased runoff and evaporation• altered precipitation patterns (more extreme precipitation events and droughts)

What are the major reservoirs and transfer processes of the carbon cycle?

1\) Carbon cycles between reservoirs that include: a) the atmosphereb) organismsc) the earth's subsurface (soil, sediment, fossils).2\) Transfer processes between reservoirs• Processes reducing atmospheric carbon include: uptake by plants (photosynthesis), and storage in biomass and earth's subsurface• Processes increasing atmospheric carbon include: cellular respiration, and burning of wood (deforestation) and fossil fuels

How do human activities alter the carbon cycle?

1\) Human activities increase atmospheric carbon concentrations. 2\) The environmental consequence (climate change) has negative effects on human welfare.

What is climate change, and what are the causes

change in long-term temperature and precipitation patterns due to global warmingCause - increasing atmospheric concentrations of greenhouse gases (e.g., CO2) trap heat generated by the sunAtmospheric concentrations of greenhouse gases are increasing due to: • Fossil fuel combustion/burning• Declining plant biomass

How is climate change influencing biological production and species diversity, and human welfare?

1\) Impacts on the water cycle, and resulting effects• Increased evaporation leads to extreme precipitation events and droughts; soil moisture is declining in most geographic areas• Melting polar ice increases sea level, reducing land area• Global-scale declines caused by increased temperatures and changes in the water cycle• Extinction-avoidance for many species depends on capacity for long-range dispersal (geographic range shift) or adaptation (may require extensive genetic diversity) to changing conditions• Some ecosystems may be lost (e.g., coral reefs are succumbing to warming water, and acidification from CO2 inputs to ocean).• Declining abundance and diversity of vital natural resources (water, land, food) and other ecosystem services• Extreme weather events threaten human health and safety

What is biodiversity?

the variety of life in the world or in a particular habitat or ecosystem.

What are the four major causes for global declines in biodiversity that were discussed in class?

1\) Habitat loss 2\) overexploitation of natural resources are primary causes for declining biodiversity.3\) Pollution• Nutrient pollution (anoxia and toxic algal blooms are consequences of eutrophication in aquatic ecosystems)• Industrial chemicals (have immediate and long-term toxic effects; biomagnification)• Plastics and other garbage (kill animals in many ways)4\) Climate change• Declines in biodiversity and biological production are expected because many species cannot survive rapidly changing conditions.

Why is preservation of biodiversity essential for human well-being?

1\) Ecosystem services - almost all species benefit humans• Organisms are sources of food, fuel, building materials, medicine• Plants produce oxygen and regulate water and carbon cycles (making earth habitable).• Species providing these services depend on other species for their survival (e.g., plants depend on fungi and pollinators).

What actions can preserve biodiversity?

1\) Address the human population growth issue.2\) Restore and protect ecosystems.3\) Use resources in a sustainable manner.• Apply population ecology data to establish harvest limits.• Enact and enforce laws to prevent overexploitation of resources.4\) Use fewer resources and generate less pollution.

Long petals increase the fitness of certain flowers by increasing their ability to attract pollinators. What does fitness mean in this context?

Fitness is the ability of flowers with long petals to produce more surviving offspring than do flowers with short petals.

A dairy farmer chooses to mate a male bull only with the female heifers that always make the greatest amount of milk, rather than heifers that produce a small amount of milk. What process is the dairy farmer employing when producing the next generation of calves?

Artificial selection

Which statement about genetic drift is correct?
The direction of evolutionary change due to genetic drift is random.
Genetic drift results from migration of new individuals into a population.
Genetic drift becomes increasingly important with increasing population size.
Genetic drift increases adaptation of individuals to their environment.

The direction of evolutionary change due to genetic drift is random.

Which of the following is the most predictable outcome of increased gene flow between two populations?
higher average fitness in both populations
increased genetic driftincreased genetic difference between the two population
slower average fitness in both populations
decreased genetic difference between the two populations

decreased genetic difference between the two populations

Mutation is the only evolutionary mechanism that ________.

is the ultimate source of variation in natural populations

Which evolutionary mechanism increases genetic variation in a population?

mutation

Toucans disperse seeds of key forest species such as jucara palms by eating the fruit and defecating the seeds in new locations, sometimes more than a kilometer away. In the Brazilian Atlantic rain forest, jucara palms are becoming isolated in smaller "islands" of forest because of human activities. If toucans are disappearing in these fragments, is the genetic diversity of palms likely to increase or decrease within forest fragments? Why?

Toucans are able to fly between the forest fragments and transfer palm seeds, thereby maintaining genetic diversity in the fragments through gene flow. If the toucans disappear, the genetic diversity of palms would decrease in the forest fragments over time.

Bird guides once listed the myrtle warbler and Audubon's warbler as distinct species. Recently, these birds have been classified as eastern and western forms of a single species, the yellow-rumped warbler. Which of the following pieces of evidence, if TRUE, would be cause for this reclassification?

The two forms interbreed often in nature, and their offspring have good survival and reproduction.

Which is the first step in allopatric speciation?

physical isolation of two populations

Which level of ecological study focuses the most on abiotic factors?

ecosystem ecology

Which of the following are important biotic factors that can affect the structure and organization of biological communities?

predation, competition

How does solar radiation (per unit area) vary with increasing latitude?

It decreases.

Turnover of water in temperate lakes during the spring and fall is made possible by which of the following?

The changes in the density of water as seasonal temperatures change

Why is there a trade-off between survivorship and fecundity?

Resources such as time and energy are limited, so survivorship and fecundity cannot both be maximized simultaneously.

As N approaches K for a certain population, which of the following is predicted by the logistic equation?

The growth rate will approach zero.

Why do populations grow more slowly as they approach their carrying capacity?

Density-dependent factors lead to fewer births and increased mortality.

Which of the following could be a density-independent factor limiting human population growth?

earthquakes

Epiphytic orchids grow harmlessly on their host trees, and they derive their resources from the air and from rain, rather than from their host plant. Which of the following is the best description of this species interaction?

Commensalism