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By morphology or spatial separation and also as clusters of individuals that interbreed.
Variations in ecological roles, such as producers, herbivores, predators, and detritivores.
The variation in genetic material within species
What was the Cambrian Explosion?
A rapid diversification of life (~541 Mya) where most animal phyla appeared in the fossil record
What caused the largest mass extinction?
The Late Permian
Divergent natural selection that leads to reproductive isolation and differences between species
What are the two main types of reproductive isolation?
Prezygotic barriers: Behavioral, morphological, phenological differences.
Postzygotic barriers: Hybrid sterility, embryo failure.
Mass extinctions create opportunities for diversification as new niches become available
The natural, ongoing process of species loss that occurs at a low rate over geological time.
species diversity at the local level
Beta diversity can be calculated by dividing gamma diversity by alpha diversity
Promotes species coexistence by species altering environments, resources, and competition, creating niches that reduce direct conflict and stabilizing ecological communities
What are the different dimensions of biodiversity?
Functional diversity: Different ecological roles (e.g., producers, predators).
Genetic diversity: Variation in genetic material within species.
Biomass: Most of Earth's biomass consists of plants and bacteria
What are the key processes driving speciation?
Isolation (Reproductive, Geographic).
Divergent Selection (Ecological Speciation).
Genome Shift (Polyploidization).
What does macroecology study?
Large-scale ecological patterns, including biodiversity, biomass, species abundance and ecosystem functions
How does area size affect species richness?
Larger areas tend to have more species due to increased habitat heterogeneity, colonization-extinction dynamics, and speciation.
How has human activity influenced biodiversity?
Through niche construction, habitat alteration, species introductions, agriculture, and climate change
What is adaptive radiation?
Adaptive radiation is when a single species can give rise to multiple different species or varieties, each adapted to a specific environment or resource, often after new environmental opportunities arise
What are examples of key innovations that drove diversification?
Bats: Flight + echolocation → Nocturnal niche.
Cacti: CAM photosynthesis + spines → Drought adaptation.
Rodents: Persistent incisor growth → Seed eating.
What’s the difference between neutral and niche theory?
Neutral theory: Species are functionally equivalent, and biodiversity results from random processes. Niche theory: Competition, adaptations, and environmental conditions shape biodiversity.
How does patch dynamics explain species coexistence?
Species colonize and go extinct in different habitat patches, maintaining biodiversity through ongoing turnover.
What is the mass-effect perspective in ecology?
Immigration from larger populations can prevent local extinction, affecting population sizes and community structure while helping maintain species presence in less favorable conditions
How do background and mass extinctions differ?
Background extinction: Gradual, ongoing species loss due to environmental shifts.Mass extinction: Sudden, widespread loss of species due to catastrophic events.
What does island biogeography predict about species diversity?
Larger islands: More species due to higher colonization and lower extinction rates. Smaller islands: Fewer species due to isolation and limited resources
What is beta diversity?
A measure of species turnover between different habitats or regions
What happens when species’ niches overlap?
It can lead to competition, niche differentiation, or competitive exclusion if one species outcompetes the other
How does dispersal affect biodiversity?
High dispersal rates can prevent local extinctions and maintain species diversity across fragmented landscapes
Why is species richness higher in the tropics?
Due to higher energy availability, stable climate, and greater historical accumulation of species
What techniques are used in biodiversity assessments?
Field surveys (species mapping, habitat protection).
Species-area relationships (SARs) (how biodiversity scales with area).
Biodiversity index quantifies species richness and evenness
What do species abundance distributions (SADs) show?
SADs show relative abundance of species in an area, indicating how common or rare each species is compared to others in the same ecosystem and the trend is that most species are rare and only a few are common
What percentage of extinctions are background extinctions?
Around 90%
What is phylogenetic turnover?
Changes in the species composition of a community over time, reflecting shifts in evolutionary relationships between species
A measure of evolutionary distance between species assemblages over time
What is low phylogenetic turnover?
Communities share closely related species, indicating similar evolutionary histories or weaker environmental filtering
What is high phylogenetic turnover?
Communities have distantly related species, suggesting distinct evolutionary histories or strong environmental filtering
What is environmental filtering?
It is when environmental conditions limit which species can thrive, favoring those best adapted to the specific conditions
How do modern scientists study extinctions that occurred in the last 200–300 years?
Through fossil records, molecular phylogenetics, and direct observations of species decline
Why is proving species extinction difficult?
Absence of evidence does not confirm extinction-species may persist in unexplored habitats
How does phylogenetics help in understanding extinction?
It combines fossil evidence and molecular data to model extinction patterns and predict future risks
What are some challenges in studying extinction patterns?
Gaps in data such as fossil records, lack of research on invertebrates, and limited monitoring resources for non-charismatic species and difficulty proving species absenc
What is "extinction debt"?
The idea that species may already be functionally doomed due to past environmental changes, even if they haven’t disappeared yet
Why do species with low genetic diversity face higher extinction risks?
They have reduced adaptability, making them vulnerable to disease, environmental changes, and genetic defects
What is "mutational load," and how does it relate to extinction?
The accumulation of harmful mutations that weaken a species’ survival and reproductive success over time
Why are species with specialized ecological niches more vulnerable to extinction?
They depend on specific conditions or resources that may disappear due to environmental changes
What is dispersal limitation, and how does it increase extinction risk?
Some species cannot move quickly or far enough to find new suitable habitats, leading to their decline
Why are island species more prone to extinction?
They have small populations, limited genetic diversity, and restricted migration options, making them highly vulnerable
What is an extinction cascade?
The loss of one species triggers a chain reaction of extinctions in an ecosystem
What is phylogenetic diversity, and why does it matter for conservation?
It measures the evolutionary relationships among species—losing a unique lineage means losing millions of years of evolutionary history
What are "extinction hotspots"?
Regions with high numbers of endangered species and rapid biodiversity loss, such as tropical rainforests and coral reefs
How does the fossil record help scientists study extinction?
It provides evidence of past biodiversity, extinction patterns, and environmental changes over time
What are some limitations of studying extinction through fossils?
Fossil records are incomplete, biased toward hard-bodied organisms, and difficult to precisely date
How do scientists estimate extinction rates for species with no fossil record?
They use mathematical models, phylogenetic data, and modern species distribution trends
What is the Anthropocene, and why is it significant for extinctions?
The current geological epoch, marked by human-driven environmental changes and biodiversity loss
What is a species' extinction threshold?
The population size below which a species cannot sustain itself and is doomed to extinction
Why does species richness matter in ecosystems?
Ecosystem biomass/functioning reaches ~80% efficiency with just 3-5 species.
More species increase resource utilization through niche filling and competition
What are latitudinal patterns in biodiversity?
Biodiversity tends to be higher in the tropics due to factors like energy availability, habitat heterogeneity, and historical contingencies. Neutral theory and niche partitioning also play roles in explaining these patterns
What is the prey-predator mass correlation?
Larger prey supports larger predators. Human impacts, like fishing, can disrupt this correlation by affecting species' size distributions
What are trait distributions in macroecology?
Describes how trait variation across species affects their survival and interactions on large scales, for ex. temperature optima providing insights into how species' traits reflect the environments they inhabit
What is dispersal assembly in macroecology?
Suggests that species' movement and colonization shape community composition, with dispersal abilities and habitat availability influencing biodiversity at large scales
What is the role of allometric constraints in macroecology?
Allometric constraints refer to the relationship between body size and ecological function, where larger organisms are often more efficient. This influences species' ecological roles and distributions
What is spatial heterogeneity in macroecology?
Spatial heterogeneity refers to variation in environmental conditions across space, which influences species distributions, colonization, and extinction rates
What is the relationship between mountain ranges and speciation?
Mountain ranges create geographic isolation, which can lead to increased speciation by limiting gene flow between populations
What are key innovations in macroecology?
Key innovations are traits that enable species to exploit new ecological zones, leading to increased diversification
What is the difference between alpha and gamma diversity?
Alpha diversity: Species diversity at the local level.
Gamma diversity: Species diversity at the regional level (species pool)
What is the species sorting model in community dynamics?
It’s the process where local community composition is influenced by patch quality and dispersal. Species are distributed based on their ecological needs, avoiding competition by occupying different niches
What is the mass-effect perspective in community dynamics?
Focuses on how immigration and emigration impact local species diversity. Species may be "rescued" from local extinction by immigration from areas with stronger competitors
What is the neutral perspective in community dynamics?
Assumes that species are similar in competitive ability, movement, and fitness. Diversity results from random processes like species loss (extinction, emigration) and gain (immigration, speciation)
What is the relationship between productivity and plant diversity?
High productivity (due to high nutrient availability) can reduce plant diversity at lower levels by favoring large plants, which outcompete smaller ones through shading. Herbivory can reverse this trend by limiting large plants
What is the role of dispersal in neutral theory?
In neutral theory, dispersal determines which species arrive at a location first. Larger populations are more likely to colonize new areas due to higher arrival probability, but species are assumed to be functionally equivalent
What is the Lotka-Volterra model?
illustrates species dependence, showing how the increase of one species often leads to the decline of another due to competition or predation
What is the significance of the log-normal model in species abundance distributions?
Describes how species abundances are distributed, with a few species being very abundant and many species being rare. It is one of several statistical models used to understand species abundance patterns
Why is biodiversity unevenly distributed among clades and regions?
Due to differences in rates (speciation, extinction, and time for accumulation) and opportunities (resource availability, niche subdivision, and geographic area)
What are two main types of explanations for biodiversity patterns?
Non-equilibrium (Rate-based): Higher speciation rates, lower extinction rates, or more time for species accumulation.
Equilibrium (Opportunity-based): More resources, finer niche subdivision, and larger geographic regions.
What is an example of a study system used to provide evidence for sympatric speciation?
Examples include Lord Howe plants, crater lake cichlids, and maggot flies
What key feature makes a study system suitable for studying sympatric speciation?
A confined geographical system (island, lake, host), with no barriers to gene flow that have ever existed
Name two macroecological patterns and their potential mechanisms.
Species-area relationship: The positive relation between species richness and area covered can depend on the fact that larger areas contain more niches due to landscape heterogeneity and thus larger areas also sample more species that are specialised. The species area relationship
can, however, to some degree also be generated with very simple models of neutral processes of colonisation and extinction
Body-size distributions: In aquatic systems one often finds that smaller species are much more abundant than larger species. The slope of the size-abundance relation depends both on the average ratio between predator and prey and on the energy transfer efficiency between these.
Latitudinal gradient in species richness: There are several hypotheses, but a prominent one is that the further from the equator one comes, the larger the climatic variations are. Species need to adapt to the range of climatic variations for survival resulting in larger range distributions at higher latitudes, which in turn leads to fewer species per area.
What are two main factors that have promoted biodiversity increase over time?
Continental drift and mass extinctions (which free up niche space)
How did early human global colonization affect biodiversity?
Through species extinction, translocation, habitat change, and niche modification
What is the difference between species-sorting and neutrality perspectives in metacommunities?
Species-sorting: Species occupy different niches and competition is predictable.
Neutrality: Species are equivalent competitors, and competition outcomes are random
How does dispersal function in species-sorting vs. neutrality models?
Species-sorting: Dispersal ensures species reach optimal niches.
Neutrality: Dispersal is random, shaping community differences by distance
What is the main difficulty in mapping global biodiversity?
Lack of data and spatial bias (more records in developed areas)
Name three things to consider before analyzing public biodiversity data
Who collected the data?
When was it collected?
What biases exist in species occurrence records?
How does body-size distribution affect species abundance?
Smaller species tend to be more abundant than larger species, influenced by predator-prey ratios and energy transfer efficiency
What is the latitudinal gradient in species richness?
Species richness decreases with latitude, as species near the poles must adapt to larger climatic variations, leading to fewer species per area
What are two ways humans have modified biodiversity before agriculture?
Overexploitation and extinctions of species.
Niche modifications through fire and habitat changes
What is the role of continental drift in biodiversity?
It creates new ecosystems, isolates populations, and promotes speciation by separating land masses
What does the Shannon Diversity Index measure?
Species diversity, considering both species richness and evenness in a community
Why is spatial bias a problem in biodiversity mapping?
More data is collected in developed areas and near cities, leading to incomplete global biodiversity maps
Why is rarefaction important in species richness comparisons?
It standardizes species richness by accounting for differences in sample sizes, making comparisons fairer
What is a key challenge of using public biodiversity databases?
Data may be collected inconsistently, biased toward well-studied areas, or have errors in species identification
What are two hypotheses explaining why biodiversity is higher in the tropics?
Stable climate allows for long-term species accumulation.
Higher resource availability enables finer niche partitioning
Why are crater lake cichlids a strong example of sympatric speciation?
They evolved into multiple species within the same lake without physical barriers to gene flow
What traits increase survival in a mass extinction?
Wide distribution—species in multiple habitats are less vulnerable.
Generalist diet—can adapt to new food sources
Give an example of climate change reshaping biodiversity in the last 66 million years
Paleocene-Eocene Thermal Maximum (56 Mya)—a global warming event that expanded tropical rainforests
In rarefaction, what does the y-axis represent?
The expected species richness based on a given number of individuals or samples
Which forest plot (circular vs. narrow) likely has more species?
The narrow plot—it has a larger edge area, allowing more species exchange
What happens when surrounding forests are cut down, isolating plots?
Species loss due to habitat fragmentation, but potential new colonization in isolated areas
What are the four explanations for the species-area relationship?
Sampling effect—larger areas include more individuals.
Habitat diversity—more niches support more species.
Colonization-extinction balance—larger areas receive more colonists and experience fewer extinctions.
Speciation-extinction dynamics—larger areas favor speciation and reduce extinction
What is gamma diversity?
The total species richness across multiple habitats in a region
