Chapter 11: Evolution of Organisms and Biodiversity of Freshwaters

Practice flashcards covering biodiversity measures, temporal and spatial evolution factors, population genetics, metapopulations, invasive species, and extinction in freshwater environments.

What is species richness?

The total number of species found in an area.

What is evenness in the context of biodiversity?

How equally represented the numbers of each species are in a community.

What is the Shannon index ($H'$), and how is it calculated?

A measure of diversity incorporating both richness and evenness, defined by the formula $H' = -\sum_{j=1}^{S} p_j \ln(p_j)$, where $S$ is species richness and $p_j$ is the proportion of species $j$.

How do changes in species richness and evenness affect the Shannon index ($H'$)?

$H'$ increases with greater species richness (more species) and with greater evenness among species.

What is the difference between $\alpha$-diversity and $\beta$-diversity?

$\alpha$-diversity represents within-habitat diversity, whereas $\beta$-diversity represents between-habitat diversity.

Based on this diagram of community samples, how do communities (A)–(D) compare to communities (E)–(H) in diversity metrics?

Communities (A)–(D) and (E)–(H) have the same total diversity and evenness, but (A)–(D) have lower $\alpha$-diversity and higher $\beta$-diversity than (E)–(H).

What is the Ecoregion concept, and how many freshwater ecoregions are identified in North America?

The classification of habitats based on $\beta$-diversity and abiotic conditions; North America contains $76$ ecoregions grouped into $8$ major regions.

How many of the $76$ North American freshwater ecoregions are located in Texas?

$8$ ecoregions: U.S. Southern Plains, Ouachita Highlands, Sabine-Galveston, East Texas Gulf, West Texas Gulf, Pecos, Upper Rio Grande, and Lower Rio Grande.

What two primary factors influence the evolution of new freshwater species?

Time available for evolution and reproductive isolation.

What defines an endemic species?

A species that has a restricted geographic distribution.

What is adaptive radiation?

The evolution of many species from a single or a few founder species.

According to this taxonomic comparison across ancient lakes, which taxonomic group comprises the majority of endemic species in Lake Baikal?

Endemic crustaceans make up the vast majority of endemic taxa in Lake Baikal.

What five short-term factors influence the local distribution and assemblage of species?

Species interactions, productivity, species introductions, habitat type, and colonization.

What are the three key characteristics of cosmopolitan species?

Life history stages that can survive transport, production of large numbers of individuals in that transportable stage, and the ability to survive (compete successfully and avoid predation) in new habitats.

What mathematical relationship describes how species richness scales with habitat area?

$S = cA^z$ (or $\log(S) = \log(c) + z \log(A)$), where $S$ is species richness, $A$ is area, $c$ is a constant measuring species per unit area, and $z$ is the slope.

How does species diversity change across the sequence of ecological succession?

Diversity is low in early and late succession and reaches its highest levels in the middle stages of succession.

What does the Dynamic Equilibrium Model propose regarding natural disturbance?

Natural disturbance decreases diversity if it exceeds species' ability to recover, but increases diversity if it removes dominant species that outcompete others.

What does the Intermediate Disturbance Hypothesis predict regarding species diversity?

Maximum diversity occurs at intermediate levels of natural disturbance frequency and intensity.

What three components comprise genetic diversity within species?

The proportion of polymorphic loci across the genome (gene diversity), the number of individuals within a species with polymorphic loci (heterozygosity), and the number of alleles per locus.

What is the Minimum Viable Population (MVP)?

The lowest number of individuals required for a population to survive in the wild against stochastic environmental or demographic events.

What is effective population size?

The members of a population that actually contribute genes to succeeding generations.

What does the concept of an extinction vortex describe?

As populations become smaller, their susceptibility to extinction accelerates exponentially.

In metapopulation dynamics, how do source and sink populations differ?

Source populations occur in prime habitats where individuals survive, multiply, and emigrate; sink populations are locations where populations would go extinct without replenishment from source populations.

Under what ecosystem conditions are major community effects from invasive species most frequently observed?

In low-diversity systems and when native assemblages are disturbed.

What distinguishes extinction from extirpation?

Extinction means no living individuals of a species exist anywhere on Earth, while extirpation means no individuals exist in the wild or natural habitat, though some may remain in captivity.

What is the estimated economic value of human waste processing performed by aquatic microbes?

More than $700\text{ billion}$ per year.