Ecological Sampling and Species Assessment

What does the Lincoln-Petersen index calculate in the mark-release-recapture technique?

• The number of species in a habitat

• The estimated population size of a species

• The rate of migration of a species

• The species evenness of a community

Which of the following is a key assumption of the mark-release-recapture technique?

• Marked individuals are more likely to be recaptured than unmarked individuals

• The population size changes significantly between the capture and recapture events

• Marked individuals mix randomly and evenly throughout the population

• The marking process must cause visible injury to the organism

What is species richness?

• The relative abundance of each species in a community

• The total number of different species present in a given area

• The ratio of predators to prey in an ecosystem

• The biomass of all species combined in a habitat

• 100

• 150

• 200

• 250

A student is sampling the distribution of plant species across a field. Which sampling technique would be most appropriate to investigate whether there is a change in species distribution along an environmental gradient, such as from a shaded woodland edge to an open meadow?

• Random quadrat sampling

• Systematic sampling using a transect

• Mark-release-recapture

• Capture-recapture with pitfall traps

Two woodland areas, Area A and Area B, each contain 4 species with the following numbers of individuals: **Area A:** Species 1: 25, Species 2: 25, Species 3: 25, Species 4: 25 **Area B:** Species 1: 85, Species 2: 5, Species 3: 5, Species 4: 5 Which statement correctly compares the two areas?

• Area A has greater species richness but lower species evenness than Area B

• Area B has greater species richness and greater species evenness than Area A

• Both areas have equal species richness, but Area A has greater species evenness

• Both areas have equal species richness and equal species evenness

• 0.53

• 0.63

• 0.73

• 0.83

A researcher is studying a population of water voles along a riverbank. In the first capture, 30 voles are marked and released. In the second capture, 45 voles are caught, of which 9 are marked. However, it is later discovered that some marked voles had lost their tags before recapture. How would this affect the population estimate calculated using the Lincoln-Petersen index, and why?

• The estimate would be unaffected, as lost tags do not influence the formula

• The estimate would be lower than the true population size, as fewer recaptured individuals appear marked

• The estimate would be higher than the true population size, as fewer recaptured individuals appear marked

• The estimate would be higher than the true population size, as more individuals would be captured in the second sample

A conservation ecologist is comparing two grassland sites to determine which should be prioritised for protection. Site X has 12 species with relatively equal abundances, whilst Site Y has 18 species but is heavily dominated by one invasive grass species. Using your understanding of both species richness and species evenness, evaluate which site may be considered more ecologically diverse and justify your reasoning.

• Site Y is more ecologically diverse solely because it has a higher species richness

• Site X is more ecologically diverse because species richness is the only valid measure of biodiversity

• Site Y is more ecologically diverse because the invasive species increases overall biomass

• A diversity index accounting for both species richness and evenness would likely rate Site X as more diverse, as its high evenness offsets its lower richness compared to the dominance-skewed Site Y

A student conducts a mark-release-recapture study on a population of grasshoppers in a meadow. They mark 60 individuals and release them. One week later, they recapture 80 individuals, of which 24 are marked. However, the weather during the week was unusually cold, significantly reducing grasshopper movement. Evaluate how this environmental condition would affect the validity of the population estimate and suggest what the likely outcome would be.

• The estimate would be valid because temperature does not affect grasshopper behaviour

• The estimate would be an overestimate because reduced movement means marked individuals are less likely to mix randomly, increasing the proportion of marked individuals recaptured

• The estimate would be an underestimate because reduced movement means marked individuals are less likely to mix randomly, increasing the proportion of marked individuals recaptured

• The estimate would be valid because the same number of individuals were marked and recaptured