Week 24 Flashcards
(37 cards)
What is species richness?
Species richness is the number of species in a specified area at a specified time.
What are the three types of diversity related to species richness?
Alpha diversity (within a smaller area), Beta diversity (rate of change across habitats), and Gamma diversity (species richness in an entire region).
What is species evenness and how is it different from species richness?
Species evenness refers to how evenly individuals are distributed among species in an area, while richness is the total number of different species present.
How many species are currently described on Earth?
Approximately 2.1 million species are described.
Why might the current number of described species be inaccurate?
Due to underrepresentation of certain groups and taxonomic discrepancies.
What does the geological history of species show us about extinction?
Fossil records show extinction events, but they are incomplete and biased toward species with preservable hard parts.
What are species accumulation curves and what do they help determine?
They estimate the number of species based on monitoring and help understand how sampling effort affects species discovery.
What does a species area curve demonstrate?
Larger areas tend to have more species due to more habitats, niches, and resilience to immigration and emigration effects.
Why is species richness typically higher at the equator?
Due to higher productivity, speciation rates, and habitat complexity at equatorial latitudes.
How does productivity influence species richness?
Productivity varies by scale and can both increase and decrease richness depending on competition and resource distribution.
What is the relationship between competition and species richness?
Competition affects species richness differently depending on resource availability; it may limit richness when resources are low or high.
What are key differences in species richness between temperate and tropical regions?
Tropical regions tend to have higher species richness due to greater productivity, stable climates, and more niches.
What is one way to define species rarity in a community?
By the proportion of individuals—species with abundance below a certain percentage (e.g., 10%) are considered rare.
What are three ways to define rarity using abundance data?
- Proportion of species (lowest x%)
- Proportion of total individuals (x% or less of total)
- Proportion of maximum (x% or less of most common species)
How can range and abundance combinations affect rarity classification?
A species can be considered rare if it has low abundance and/or a narrow range.
Why might recorder effort affect assessments of rarity?
Areas with fewer observations may incorrectly appear to have rarer species due to under-sampling.
What is a key finding about species abundance and range from bird data?
Most species have both low abundance and small ranges, making them rare.
What pattern did RSPB reports show about species abundance over 50 years?
60% of 3,148 species surveyed declined in abundance.
What does the ‘sky at night effect’ refer to in ecology?
It illustrates the broad variation in species’ abundance and range; few species have high values for both.
How quickly can abundance change in species like elder aphids?
Very rapidly—highlighting that rarity is dynamic, not static.
What was concluded from the freshwater streams study (1985-1986)?
Species that were abundant before were also abundant after recolonization, showing stability in abundance patterns.
How can range size reduction affect population size?
Effects vary: some show linear decline, some sharp initial drops, and others show delayed effects.
How does diet specialization relate to rarity?
Monophages (specialized diet) typically have smaller ranges and are rarer than polyphages (generalists).
What plant example shows dispersal ability’s effect on rarity?
Dog’s mercury (limited dispersal, rarer) vs. dandelion (high dispersal, common).
