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What defines a population?

A group of organisms of the same species living in the same area at the same time that typically interbreed.

Why is population size often estimated instead of counted directly?

Because some organisms are too numerous or too mobile to count, leading to sampling errors.

What is random quadrat sampling used for?

Estimating population size of sessile organisms by randomly sampling squares in a grid.

What method estimates population size for motile organisms?

Capture-mark-release-recapture and the Lincoln Index formula.

What is carrying capacity?

The maximum number of organisms an ecosystem can support, determined by resources like food, water, and shelter.

What are density-dependent factors? Give examples.

Factors that regulate population size based on density, such as disease, predation, and competition.

What are density-independent factors?

Factors like natural disasters or weather that affect populations regardless of density.

Describe the sigmoid (logistic) population growth curve.

It shows rapid growth initially (exponential phase), then slows as resources limit growth, eventually stabilizing at carrying capacity.

What is natural selection?

A process where organisms with favorable traits reproduce more successfully, causing these traits to become more common over generations.

How do mutations and sexual reproduction contribute to variation?

Mutations introduce new alleles, and sexual reproduction reshuffles alleles to create new combinations.

What role does overproduction of offspring play in natural selection?

It leads to competition for limited resources, favoring individuals with advantageous traits.

What is fitness in evolutionary terms?

The ability of an organism to survive, reproduce, and pass on its genes.

What are density-independent factors in natural selection?

Abiotic factors like temperature, salinity, or drought that affect survival regardless of population density.

Define directional, stabilizing, and disruptive selection.

Directional: Favors one extreme phenotype; Stabilizing: Favors intermediate phenotypes; Disruptive: Favors two extreme phenotypes, which may lead to speciation.

What is ecosystem stability?

The ability of an ecosystem to remain consistent over time, often dependent on factors like genetic diversity and nutrient recycling.

How can deforestation affect ecosystem stability?

Loss of forests disrupts water cycles, reduces biodiversity, and destabilizes the ecosystem.

What is a keystone species? Give examples.

A species that has a disproportionate impact on its ecosystem. Examples: Wolves, sea otters, beavers.

What is competitive exclusion?

The principle that two species competing for the same resources cannot coexist indefinitely; one will outcompete the other.

What is niche partitioning?

The process by which competing species use resources differently to coexist.

Define primary and secondary succession.

Primary succession: Occurs on bare rock, starting with pioneer species like lichen; Secondary succession: Occurs in areas where soil already exists.

How does energy flow in an ecosystem?

Energy flows through food chains and food webs, starting with producers and moving through various consumer levels.

Why are there fewer organisms at higher trophic levels?

Energy is lost at each trophic level due to respiration, heat, and inefficiencies, reducing available energy.

What is an energy pyramid?

A diagram showing the energy transfer between trophic levels in an ecosystem, with producers at the base and top predators at the apex.

What is primary production?

The accumulation of carbon compounds in autotroph biomass.

What is secondary production?

The accumulation of carbon compounds in heterotroph biomass, which is lower than primary production due to energy loss.

What role do decomposers play in an ecosystem?

Decomposers recycle nutrients by breaking down dead organisms, feces, and organic matter into simpler compounds.

What is the difference between autotrophs and heterotrophs?

Autotrophs use external energy sources to synthesize carbon compounds; heterotrophs obtain carbon compounds from other organisms.

What is the carbon cycle?

The process by which carbon is recycled in ecosystems through photosynthesis, feeding, respiration, and decomposition.

How do ecosystems act as carbon sinks or sources?

Carbon sink: More carbon is absorbed; Carbon source: More carbon is released.

What causes energy loss in trophic levels?

Energy is lost as heat during respiration, in waste materials, and through inefficiencies in energy transfer between organisms.

What is the Keeling Curve?

A graph showing annual fluctuations in atmospheric CO₂ due to seasonal changes in photosynthesis, as well as a long-term increase due to human activities.

How does combustion contribute to the carbon cycle?

Burning of biomass, fossil fuels, or peat releases stored carbon dioxide back into the atmosphere.

What are anthropogenic causes of climate change?

Human activities, such as burning fossil fuels and deforestation, increase greenhouse gases like CO₂ and methane in the atmosphere.

What is the greenhouse effect?

The process where greenhouse gases trap heat in the atmosphere, warming the Earth.

What are positive feedback loops in global warming?

Melting ice reduces reflectivity (albedo), thawing permafrost releases methane, leading to more warming.

How can boreal forests reach a tipping point?

Warmer temperatures, reduced snowfall, and increased drought can lead to forest browning and carbon loss.

What is ecological succession?

The gradual process of change in species composition and ecosystem structure over time.

What is the difference between primary and secondary succession?

Primary succession starts on bare rock without soil; secondary succession starts where soil is present.

What is cyclical succession?

In some ecosystems, communities cycle repeatedly rather than forming a stable climax community.

What are climax communities?

Stable ecosystems that arise when succession reaches an endpoint under specific environmental conditions.

How can human activities cause arrested succession?

Activities like grazing or draining wetlands can prevent ecosystems from reaching their climax community.

What is the purpose of classifying organisms?

To organize species into groups for easier study and to reflect evolutionary relationships.

What is a clade?

A group of organisms with a common ancestor and shared characteristics.

How are cladograms constructed?

Using DNA, RNA, or amino acid sequence data to show evolutionary relationships.

What is a molecular clock?

A method of estimating divergence times between species based on the accumulation of mutations.

What are homologous structures?

Structures with similar anatomy due to shared ancestry but different functions.

What are analogous structures?

Structures with similar functions but different evolutionary origins.

What is speciation?

The process by which one species splits into two or more distinct species.

What are the roles of reproductive isolation and differential selection in speciation?

Reproductive isolation prevents gene flow; differential selection pressures lead to divergence in traits.

Compare allopatric and sympatric speciation.

Allopatric: Caused by geographic isolation; Sympatric: Occurs without geographic barriers.

What is adaptive radiation?

Rapid diversification of a species into multiple forms that occupy different ecological niches.

What are prezygotic and postzygotic barriers?

Prezygotic: Prevent mating or fertilization; Postzygotic: Result in infertile or nonviable offspring.

What is top-down control in ecosystems?

Population size is controlled by predators at the top of the food chain.

What is bottom-up control in ecosystems?

Population size is limited by the availability of nutrients and primary producers.

What is allelopathy?

A process where plants release toxic compounds to limit the growth of other plants.

What are antibiotics in plants?

Compounds produced to kill bacteria, such as those from California bay and coffeeberry.

What is sexual selection?

Selection based on traits that increase an organism’s chance of attracting a mate.

What is the gene pool?

The total collection of genes and alleles in a population.

How does natural selection affect allele frequency?

Traits that increase survival or reproduction become more common, altering allele frequencies.

What are the three types of natural selection?

Directional: Favors one extreme phenotype; Stabilizing: Favors intermediate traits; Disruptive: Favors two extremes.

What is the Hardy-Weinberg equation?

Used to calculate allele and genotype frequencies in a population.

What are the conditions for Hardy-Weinberg equilibrium?

1. No mutations, 2. No gene flow, 3. Random mating, 4. Large population size, 5. No natural selection.

What is artificial selection?

Human-driven selection for specific traits in crops or animals.

What is convergent evolution?

When unrelated species evolve similar traits due to similar environments.

What is divergent evolution?

When a single species evolves into multiple species with different traits.

What is polyploidy?

A condition where a plant has more than two sets of chromosomes, often leading to rapid speciation.

Why is rRNA used in classification?

rRNA base sequences provide evidence of evolutionary relationships due to slow mutation rates.

What are the three domains of life?

Archaea, Bacteria, and Eukarya.

What is parsimony analysis?

A method to construct cladograms by assuming the smallest number of evolutionary changes is most likely.

What is a habitat?

The place where a species, population, or community lives.

What is range of tolerance?

The range of abiotic conditions a species can survive in.

What abiotic factors affect species distribution?

Temperature, pH, salinity, oxygen, and humidity.

What are the requirements for coral reef formation?

1. Temperature: 23-29°C, 2. High salinity: 32-42 ppt, 3. Clear water, 4. pH above 7.7.

What are biomes?

Groups of ecosystems with similar abiotic conditions and organisms.

Give an example of an adaptation in a hot desert species.

Camels store fat in their humps to convert to water when needed.

What is an ecological niche?

The role of a species in its ecosystem, including interactions with biotic and abiotic factors.

What is the difference between obligate aerobes and anaerobes?

Obligate aerobes require oxygen; obligate anaerobes cannot survive in oxygen.

What is mixotrophic nutrition?

Organisms that can switch between autotrophic and heterotrophic modes of nutrition.

What are saprotrophs?

Organisms that digest organic material externally and absorb nutrients.

What is the difference between producers and consumers?

Producers are autotrophs that create biomass; consumers are heterotrophs that eat other organisms.

What is the role of decomposers?

Recycle nutrients by breaking down dead organic matter.

Why are energy transfers inefficient?

Energy is lost as heat, in respiration, or as waste at each trophic level.

What limits the number of trophic levels?

Energy loss at each level results in insufficient energy for higher levels.

What are keystone species?

Species that have a disproportionately large impact on ecosystem stability.

What is eutrophication?

Nutrient enrichment of aquatic systems causing algal blooms and dead zones.

What is biomagnification?

The increasing concentration of toxins in organisms at higher trophic levels.

What is rewilding?

Restoring natural processes by reintroducing species and reducing human impacts.

What is a carbon sink?

An ecosystem that absorbs more carbon than it releases.

How does deforestation contribute to climate change?

Reduces carbon sinks and increases atmospheric CO₂.

What are the long-term effects of global warming?

Rising sea levels, increased droughts, loss of biodiversity, and tipping points in ecosystems.

What is transcription?

The process of synthesizing RNA from a DNA template.

What are the steps of transcription?

Initiation, Elongation, Termination.

What is the role of RNA polymerase?

It synthesizes the RNA strand by adding complementary RNA nucleotides.

What is the difference between the sense and antisense strands of DNA?

Sense strand matches RNA; antisense strand serves as the template for RNA synthesis.

What modifications occur to the pre-mRNA in eukaryotes?

5’ capping, Polyadenylation, Splicing.

How does transcription differ between prokaryotes and eukaryotes?

Prokaryotes have simultaneous transcription and translation; eukaryotes have separate processes.

What is translation?

The process of synthesizing a polypeptide chain from an mRNA template.

What are the steps of translation?

Initiation, Elongation, Termination.

What is the role of tRNA in translation?

Matches codon on mRNA to ensure correct amino acid addition.

What is a codon?

A sequence of three nucleotides on mRNA that specifies a single amino acid.