EVS Chapter 6: Biosphere

What are the 9 Planetary Boundaries?

Climate Change, Biosphere integrity, Stratospheric ozone depletion, Ocean acidification, Biogeochemical flows, Land-system change, Freshwater change, Atmospheric aerosol loading, Novel Entities.

What is the definition of a biosphere?

The part of Earth that contains all ecosystems.

What is a biome?

A large region with the same plant life and climate.

Define ecosystem.

A community and its nonliving surroundings.

What is a community in ecological terms?

Populations that live together in a defined area.

What is a population?

A group of organisms of one type that live in the same area.

What is the Primitive Soup Theory?

A theory suggesting that inorganic components can create organic compounds under early Earth conditions.

What is the Ocean Floor Oases theory?

Life thrives in aphotic environments around hydrothermal springs, supported by chemotrophic bacteria.

What does the Clay Hypothesis propose?

Clay minerals can absorb organic molecules and catalyze the polymerization of amino acids and nucleotides.

What is the Panspermia Theory?

The theory that life exists throughout the universe and is distributed by space dust, meteoroids, and comets.

What is the geological timeline for the oldest known sedimentary rocks?

3.76 billion years ago.

What is evolution?

A complex, branching process where different species evolve in diverse directions, driven by chance and natural selection.

What are the 5 mechanisms of evolution?

Variability, Heritability, Genetic Drift, Selection, Speciation.

What is genetic drift?

Random fluctuations in the frequency of a particular gene version within a population.

Define natural selection.

The process where the best-adapted individuals survive and reproduce, spreading advantageous traits.

What is the difference between allopatric and sympatric speciation?

Allopatric speciation occurs with physical/geographic isolation, while sympatric speciation occurs without physical separation.

What does LUCA stand for?

Last Universal Common Ancestor.

What is the baseline extinction rate?

Approximately 1 species per million years.

What distinguishes mass extinctions from normal extinctions?

Mass extinctions kill off massive numbers of species rapidly, while normal extinctions occur at a constant, slow rate.

What are the anthropogenic causes of current extinctions?

CO₂-driven global warming, land use changes, resource exploitation, pollution, diseases, and invasive species.

Why is understanding evolution important?

It helps predict how biodiversity will react to environmental changes and informs effective protection strategies.

What is population ecology?

The study of factors affecting a population and how it changes over time.

What is a metapopulation?

A group of spatially separated populations of the same species that interact at some level.

What are the three categories of spatial distribution?

Random, uniform, and clumped.

Define population density.

The number of individuals within a population per unit area.

What are the characteristics of high population density?

Easier to find mates, provides protection, but increases competition and vulnerability to predation.

What are the downsides of low population density?

More difficult to find mates and lower genetic diversity within a specific area.

What are density-independent factors?

Limiting factors affecting a population that are unaffected by population density.

What are density-dependent factors?

Limiting factors whose influence is affected by the population density.

What is exponential growth in populations?

Growth caused by a constant growth rate, occurring only under ideal conditions.

What is carrying capacity?

The maximum population size of a species that the environment can sustain indefinitely.

What is environmental resistance?

The non-realization of biotic potential due to environmental conditions that are not sufficiently favorable.

What are r-strategies in reproductive strategies?

Strategies characterized by high growth rates and low chances of survival, typical in unstable environments.

What are K-strategies in reproductive strategies?

Strategies characterized by long lifespans and late reproduction, typical in stable environments.

What does a survivorship curve show?

The probability of death of an organism with age, indicating mortality rates over time.

What is Type I survivorship?

Characterized by more deaths in older age groups, typical of species that produce few offspring but care for them.

What is Type II survivorship?

Characterized by equal mortality rates across all age groups.

What is Type III survivorship?

Characterized by more deaths in younger age groups, with little parental care invested.

What led to the extinction of the passenger pigeon?

Mass hunting and habitat destruction, compounded by low genetic diversity.

What is the paradox of the passenger pigeon's population size?

Despite a large population, genetic diversity was low due to natural selection removing harmful mutations.

What are the ethical considerations of de-extinction?

Feasibility, risks to existing species, ethics of ownership, and potential ecosystem impacts.

What defines a community in ecology?

A set of animal, plant, and microorganism populations that interact in a given area at a given time.

What is community ecology?

The study of interactions between populations in a community and the evolution of these communities.

What is species richness?

The raw number of different species in a given community.

What is alpha diversity?

Describes species diversity within a specific area, accounting for both species richness and their relative abundance.

What does the Shannon Diversity Index (H') measure?

It quantifies alpha diversity; higher values indicate greater diversity.

What is the Pielou Evenness Index (J)?

Evaluates the distribution of individuals within species to assess community diversity.

What is the rule of thumb regarding species diversity and community stability?

Greater number and variety of species lead to greater diversity and community stability.

What does the Pielou Evenness Index (J) measure?

It evaluates the distribution of individuals within species to examine the community's degree of diversity, varying between 0 (dominance of a single species) and 1 (equal distribution).

What is mutualism in interspecific interactions?

An interaction where both species benefit, characterized by cooperation that is advantageous but not essential for survival.

Define commensalism.

An interaction where one species benefits while the other suffers no damage or benefit.

What is predation?

An interaction where one species (the predator) consumes another (the prey), driven by cyclical adaptations.

What is parasitism?

An interaction where one species benefits by harming the host, which can be an endoparasite (inside the host) or ectoparasite (on the host).

What is competition in ecological interactions?

An interaction where organisms compete for the same resources, leading to decreased availability for both.

Define amensalism.

An interaction where one organism is harmed while the other remains unaffected.

What is an ecological niche?

The position, habitat, and role a species occupies within an ecosystem, including its use of biotic and abiotic resources.

What is the difference between a fundamental niche and a realized niche?

The fundamental niche is the theoretical set of conditions for survival and reproduction, while the realized niche is the actual conditions used after accounting for interactions.

What does Gause's Principle of Competitive Exclusion state?

Two species with the exact same ecological niche cannot coexist sustainably; one will be eliminated over time.

What are Lotka-Volterra Equations?

A pair of equations describing the cyclical dynamics of predator-prey biological systems.

What is coevolution?

An evolutionary 'arms race' where coexisting species must constantly adapt to survive against each other.

What are the three types of functional groups in a food chain?

Producers (autotrophs), primary consumers (heterotrophs), and secondary/tertiary consumers (carnivores).

What is a keystone species?

An organism with a massive impact on its environment relative to its abundance; its removal can drastically change the ecosystem.

What is a trophic cascade?

A series of reciprocal changes through the food chain triggered by adding or removing a top predator.

Define ecological succession.

The chronological appearance of species in an environment following a disturbance, leading to increased diversity until equilibrium is reached.

What is primary succession?

Succession that occurs in a completely barren area where all vegetation and soil life were eliminated, starting with pioneer species.

What is secondary succession?

Succession that occurs in a habitat previously occupied but not completely disrupted, allowing for faster recolonization.

What is the role of invasive species?

Exotic organisms that spread and dominate a community, outcompeting native species and reducing biodiversity.

What is the difference between resistance and resilience in ecosystems?

Resistance is the ability to withstand disturbances, while resilience is the capacity to recover from them.

What are decomposers and detritivores?

Decomposers break down dead organic matter, while detritivores break down waste from living organisms.

What is an energy pyramid?

A representation showing that the majority of energy is lost as heat during respiration as it moves up the food chain.

What is the significance of fire in ecosystems?

Natural fires are essential for many ecosystems, but they can threaten human life and release large amounts of CO₂.

What are autogenic and allogenic engineer species?

Autogenic species modify the environment via their own structures, while allogenic species actively modify the physical structure of the ecosystem.

What is the impact of human activity on invasive species?

Human activities often introduce invasive species, which can dominate communities and disrupt local ecosystems.

What is the role of pioneer species in succession?

Pioneer species help form soil and allow biodiversity to increase in both primary and secondary succession.

What is a system in ecological terms?

A network of relationships involving exchanges of energy or matter.

What are the three types of systems?

Isolated system (no exchange), closed system (exchange of energy but not matter), open system (exchange of both energy and matter).

What is an example of a closed system?

Modern Earth, where energy can enter and leave but physical matter cannot.

What is feedback in ecological systems?

Interaction where the disturbance of one variable causes a change in a second variable, which influences the initial variable.

What is a negative feedback loop?

A process that attenuates disturbances, allowing for regulation (e.g., predator-prey dynamics).

What is a positive feedback loop?

A process that accentuates disturbances and pushes the system towards extremes (e.g., greenhouse effect).

How is energy transferred in ecosystems?

Energy is transferred and transformed, with each trophic level losing 90% of energy as heat.

What is primary production?

The rate at which organic matter (biomass) is generated from mineral matter and energy input.

What is net primary production (NNP)?

Carbon remaining after respiration of autotrophs, used to produce biomass available to heterotrophs.

What are biogeochemical cycles?

Processes that recycle, transport, and redistribute nutrients within ecosystems.

What is organic matter mineralization?

The transformation of organic carbon and nutrients into inorganic forms.

What are sources and sinks in nutrient cycles?

Sources emit more nutrients than they accumulate; sinks accumulate more nutrients than they emit.

What is the carbon cycle?

The cycle involving sources, sinks, and flows of carbon through the atmosphere, living organisms, and geological formations.

What are the main sources of atmospheric CO₂?

Respiration, decomposition, volcanism, forest fires, and human activities.

What role do phytoplankton play in the ocean carbon cycle?

They use dissolved CO₂ for photosynthesis, creating organic matter and releasing oxygen.

What is the 'Weathering Thermostat'?

A natural cycle that regulates Earth's habitability by balancing CO₂ levels through weathering processes.

How does human activity impact the carbon cycle?

Through emissions from changes in reservoirs, leading to increased atmospheric CO₂ and climate change.

What is nitrogen fixation?

The process by which soil bacteria convert atmospheric N₂ into ammonia, making it usable by plants.

What is the Haber-Bosch process?

The synthetic production of fertilizer by combining N₂ and hydrogen to synthesize ammonia.

What is the phosphorus cycle?

The cycle that involves the movement of phosphorus from rocks to soil, plants, animals, and back to soil.

What is eutrophication?

The over-enrichment of water bodies with nutrients, leading to harmful algal blooms and ecosystem collapse.

What factors shape terrestrial biomes?

Temperature and precipitation.

What are the main characteristics of the tundra biome?

Cold temperatures, short growing season, limited tree growth, and permafrost.

What defines the taiga (boreal forest) biome?

Northern coniferous forests with strong seasonal variations and poor, acidic soils.

What is the role of decomposers in nutrient cycling?

They convert organic nitrogen from waste and dead organisms back into ammonia.

How do nutrients circulate globally?

Through geological processes such as atmospheric circulation, erosion, and climatic conditions.