Population Dynamics and Ecological Sampling

An ecology student deployed a $1\text{ m}^2$ quadrat 10 times in a farmland ecosystem in Nigeria to estimate the population of a weed species. The total count of the weed recorded across all 10 quadrats was 50. What is the estimated population density of the weed per square metre?

During an ecological survey of a savanna ecosystem in Nigeria, 40 grasshoppers were captured, marked with non-toxic paint, and released back into their habitat. A second sample of 50 grasshoppers captured two days later contained 10 marked individuals. What is the estimated total population size of grasshoppers in this habitat?

An ecologist used a $2\text{ m} \times 2\text{ m}$ quadrat frame thrown randomly 15 times across a $1.2\text{ hectare}$ ($12,000\text{ m}^2$) savanna habitat in Yankari Game Reserve to estimate the population size of the variegated grasshopper (*Zonocerus variegatus*). A total of 180 grasshoppers were counted across all 15 quadrat throws. What is the estimated total population of *Zonocerus variegatus* in the entire $1.2\text{ hectare}$ study area?

An ecology student investigated the population of *Tridax procumbens* in a cassava farmland in Ogun State using a $0.5\text{ m} \times 0.5\text{ m}$ quadrat frame. Across 10 random quadrat throws, the total number of *Tridax procumbens* plants counted was 80. What is the estimated population density of *Tridax procumbens* per square metre ($\text{m}^{-2}$) in the farmland?

Match each ecological sampling instrument with its most appropriate application or target organism group during a field study in a Nigerian savanna ecosystem.

An ecology student investigated the population density of water hyacinth (*Eichhornia crassipes*) in a section of a freshwater creek in Bayelsa State. A quadrat frame measuring $0.5\text{ m} \times 0.5\text{ m}$ was randomly thrown $20$ times across the sampling site. The cumulative count of water hyacinth plants recorded across all $20$ quadrat throws was $150$. What is the estimated population density of water hyacinth in $\text{plants/m}^2$?

During a field study of an intertidal mangrove swamp in Cross River State, a student used a $0.5\text{ m} \times 0.5\text{ m}$ quadrat frame to sample the periwinkle (*Tympanotonus fuscatus*) population. Across $10$ randomly placed quadrat throws, a total count of $180$ periwinkles was recorded. What is the estimated population density of *Tympanotonus fuscatus* per square metre in this habitat?

An ecologist conducted a survey in an abandoned oil palm plantation in Edo State to determine the density of Siam weed (*Chromolaena odorata*). Using a $1\text{ m} \times 1\text{ m}$ quadrat frame thrown randomly 20 times across the field, a total of 160 Siam weed plants were counted. What is the estimated population density of Siam weed in this plantation?

During an ecological study of an agricultural fish pond in Ibadan, Oyo State, a student employed the mark-release-recapture technique to estimate the population size of tilapia (*Oreochromis niloticus*). In the initial sampling, $120$ fish were captured, marked with harmless plastic tags, and released back into the pond. Two days later, a second sample of $150$ fish was netted, out of which $30$ individuals were found to be marked. What is the estimated total population size of tilapia fish in the pond?

An ecology student investigated the population of spear grass (*Imperata cylindrica*) on a $400\text{ m}^2$ plot in Jos, Plateau State. A rectangular quadrat measuring $1.0\text{ m} \times 0.5\text{ m}$ was thrown randomly 16 times across the plot, yielding a total count of 120 spear grass plants. What is the estimated population density of spear grass in $\text{plants/m}^2$?

Match each population ecology term on the left with its correct definition on the right.

In population ecology studies across Nigerian savanna ecosystems, several factors govern population size and growth rate. Match each population dynamic concept on the left with its corresponding ecological description on the right.

An ecology student sampled the population of guinea grass (*Panicum maximum*) in a $600\text{ m}^2$ pasture plot in Kaiama, Kwara State, using a $0.5\text{ m} \times 0.5\text{ m}$ quadrat frame. The counts of grass clumps recorded from 10 randomly placed quadrats were 4, 6, 3, 7, 5, 2, 8, 4, 6, and 5. What is the estimated total population of guinea grass clumps in the entire pasture plot?

An ecological survey was conducted in the Borgu sector of Kainji Lake National Park to estimate the population size of grasscutters (*Thryonomys swinderianus*). In the initial phase, $80$ grasscutters were captured, marked with ear tags, and released back into the habitat. One week later, a second sample of $100$ grasscutters was captured, out of which $20$ individuals retained their mark. If post-marking field monitoring established that $10\%$ of all originally marked animals lost their tags during the interval, what is the estimated total population size of grasscutters in the study area?

An ecological researcher investigated the population of freshwater snails (*Bulinus globosus*) in a stream marsh measuring $250\text{ m}^2$ near Oguta Lake, Imo State. Using a quadrat frame of size $0.5\text{ m}^2$, the researcher randomly threw the quadrat $10$ times across the sampling site and recorded snail counts of $4, 6, 3, 5, 7, 2, 8, 4, 5,$ and $6$. Based on these sample measurements, what is the estimated total population size of *Bulinus globosus* in the entire $250\text{ m}^2$ marsh area?

An biology student placed a $1\text{ m}^2$ quadrat 10 times randomly in a grassland plot within Yankari Game Reserve to estimate the population density of wild marigold (*Tithonia diversifolia*). A total of 150 wild marigold plants were counted across all 10 quadrat samples. What is the population density of the wild marigold plants in organisms per square metre?

An ecologist conducted a mark-release-recapture study to estimate the population size of fiddler crabs (*Uca tangeri*) in a mangrove swamp along the Bonny Estuary in Rivers State. During the first sampling session, $150$ crabs were captured, marked with non-toxic waterproof paint, and released back into the habitat. One week later, a second sample of $120$ crabs was captured from the same area, of which $40$ were found to be marked. What is the estimated total population size of fiddler crabs in this sampled area?

A biology researcher used a $0.5\text{ m}^2$ quadrat thrown 20 times at random to estimate the population of Mexican sunflower (*Tithonia diversifolia*) in a cashew orchard measuring $500\text{ m}^2$ in Ilorin. If a total of 160 plants were counted across all quadrat throws, what is the estimated total population size of *Tithonia diversifolia* in the orchard?

An ecology student placed a $0.5\text{ m}^2$ quadrat $10$ times at random within a plot in Okomu National Park to estimate the population of Siam weed (*Chromolaena odorata*). If a total count of $120$ Siam weed plants was recorded across all sample throws, what is the estimated population density of Siam weed in plants per square metre?

During a field study on population dynamics in a secondary forest plot in Ogun State, $80$ African giant land snails (*Archachatina marginata*) were captured, tagged, and released back into their habitat. A fortnight later, a second sample of $50$ snails was collected, revealing that $16$ of them bore the original tags. What is the estimated total population size of these snails in the forest plot using the Lincoln Index?