population and community

What is a population?

A group of organisms of the same species living in the same area at the same time.

What mechanism is used to distinguish one population from another of the same species?

Reproductive isolation.

What is a population sample?

A subset of individuals selected from a larger population to make generalizations about the whole.

Why is randomness important in sampling procedures?

It ensures every member has an equal chance of selection, minimizing bias and ensuring the sample is representative.

What sampling methods are typically used for sessile organisms?

Quadrat sampling, transect lines, or plot sampling.

What sampling methods are typically used for motile organisms?

Mark-recapture, netting, or trapping.

What is a quadrat?

A simple rectangular frame used to randomly sample and count individuals in a defined area.

How is population size estimated using quadrats?

By counting individuals or estimating percentage coverage within randomly placed or systematically arranged frames.

Why is quadrat sampling ineffective for motile organisms?

Because motile organisms move out of or into the frame during the sampling process.

Describe the capture-mark-release-recapture method.

Individuals are captured, marked, and released; after time for reintegration, a second sample is taken to count marked versus unmarked individuals.

What are two requirements for marking animals in mark-recapture studies?

The mark must not be easily removable and must not adversely affect the animal's survival.

What is the formula for the Lincoln Index?

Estimated Population = (n1 × n2) ÷ n3

What does 'n1' represent in the Lincoln Index?

The number of individuals captured, marked, and released in the first session.

What does 'n3' represent in the Lincoln Index?

The number of marked individuals recaptured in the second session.

What is carrying capacity?

The maximum number of a species that can be sustainably supported by a particular environment.

What shape does a population growth curve take as it approaches carrying capacity?

A sigmoidal (S-shaped) curve.

What are density-dependent limiting factors?

Environmental conditions influenced by the relative size of a population, such as food availability, predation, and disease.

What are density-independent limiting factors?

Environmental conditions not influenced by population size, such as weather, climate, and natural disasters.

How do density-dependent factors act as a negative feedback loop?

Increased population leads to resource depletion, which reduces the population size, allowing resources to recover.

What happens to the lynx population when the snowshoe hare population increases?

The lynx population increases due to the greater availability of prey.

What causes the decline of the snowshoe hare population after initial growth?

Resource depletion (vegetation) and increased mortality due to starvation and predation.

Why does the lynx population decline after the hare population drops?

Due to starvation and reduced reproductive success caused by a lack of prey.

What is the effect of reduced predation pressure on hare populations?

It allows the hare population to recover as vegetation resources replenish.

What does the symbol 'κ' represent in population ecology?

Carrying capacity.

What type of feedback loop regulates predator-prey populations?

A negative feedback loop

What is biotic potential?

The maximal growth rate for a given population

Under what conditions do populations grow exponentially?

When resources are unlimited

What shape is an exponential growth curve?

J-shaped

What is environmental resistance?

Factors that slow population growth as it approaches carrying capacity

What shape is a population growth curve that plateaus at carrying capacity?

Sigmoidal (S-shaped)

Define an intraspecific relationship.

An interaction occurring between individuals of the same species

Give an example of cooperation in meerkats.

Dividing roles where some watch for predators while others hunt or watch young

How do robins demonstrate intraspecific competition?

They are fiercely territorial and aggressive toward other robins

How do oak trees compete with each other?

They compete for light, water, and minerals when growing in close proximity

Define an ecological community.

Multiple populations of different species living in the same area at the same time

Define an interspecific relationship.

An interaction between different species within a community

What is the key difference between predation and parasitism?

Predation results in the immediate death of the prey, while parasitism benefits the parasite without immediately killing the host

What is pathogenicity?

A relationship where a microorganism causes disease in a host

What is mutualism?

An interspecific relationship that benefits both species involved

What do rhizobia bacteria provide to legume plants?

Fixed nitrogen (ammonia) converted from atmospheric nitrogen

What do legume plants provide to rhizobia bacteria?

Carbohydrates (glucose) for cellular respiration

How do mycorrhizal fungi benefit orchids?

They supply water, minerals, and organic compounds, enabling germination and growth

What do orchids provide to mycorrhizal fungi?

Carbohydrates and other organic compounds

What do zooxanthellae provide to hard corals?

Oxygen and organic nutrients like glucose, glycerol, and amino acids via photosynthesis

What is commensalism?

A relationship where one species benefits and the other is neither helped nor harmed

Give an example of an interspecific competition.

Lions and hyenas competing for resources

Give an example of herbivory.

A rabbit eating a carrot

Why is initial population growth often slow?

Due to a shortage of reproducing individuals that may be widely dispersed

What do corals provide to their symbiotic zooxanthellae?

A protected environment, access to sunlight, and CO2 for photosynthesis.

What percentage of a coral's energy needs is provided by zooxanthellae?

Up to 90%.

What is coral bleaching?

The breakdown of the mutualistic relationship where coral polyps expel their symbiotic algae.

What are the potential environmental consequences of coral reef disappearance?

Loss of shoreline protection and habitat, leading to altered coastal ecosystems.

Define endemic species.

Plants, animals, or microorganisms native to and found only within a specific geographic region.

Define invasive species.

Organisms introduced intentionally or unintentionally into a region where they are not native, often causing environmental harm.

How do invasive species affect the realized niche of endemic species?

They introduce new competition, predation, and diseases, reducing available resources like food and habitat.

Why are Ring-necked Parakeets considered invasive in the Netherlands?

They are aggressive competitors for nesting sites, highly adaptable in their diet, and have a high reproductive rate.

What native birds do Ring-necked Parakeets compete with for nesting sites?

Woodpeckers and nuthatches.

What is the primary limitation of using field observations to prove interspecific competition?

It can indicate competition if one species impacts another's presence, but it cannot definitively prove it.

List three experimental approaches to determine interspecific competition.

Laboratory experiments, field observations by random sampling, and field manipulation by species removal.

What is the purpose of the chi-squared test in ecological fieldwork?

To determine if there is a statistically significant association between the distribution of two species.

What does a positive association between two species typically indicate?

Predator-prey or symbiotic relationships.

What does a negative association between two species typically indicate?

Competition for the same resources.

What is the null hypothesis for a chi-squared test of association?

There is no statistically significant association between the two species.

What is the alternative hypothesis for a chi-squared test of association?

There is a statistically significant association (positive or negative) between the two species.

What p-value is generally required to consider a chi-squared result statistically significant?

Less than 0.05.

What are the five steps to perform a chi-squared test?

Identify hypotheses, construct a frequency table, apply the formula, determine degrees of freedom, and identify the p-value.

What is an example of a laboratory experiment to test competition?

Growing two plant species in separate and combined pots and measuring their growth.

What is an example of field manipulation to test competition?

Removing invasive plants from specific plots to observe the impact on native plant growth.

What data is typically recorded in a quadrat for a chi-squared association test?

The presence or absence of two potentially competing species within the sampled areas.

How does higher average ocean temperature impact coral reefs?

It can trigger coral bleaching, causing the expulsion of symbiotic algae.

What is the effect of lower ocean pH on coral reefs?

It can negatively impact coral health and structural integrity, contributing to reef degradation.

What statistical tests can be used for analyzing interspecific competition data?

ANOVA, t-tests, regression analysis, and the chi-squared test.

What is the alternative hypothesis (H1) in a chi-squared test for species association?

There is a statistically significant association between the two species.

What is the null hypothesis (H0) in a chi-squared test for species association?

There is no significant difference between the distribution of the two species; their distribution is random.

What is the formula for calculating expected frequency in a chi-squared test?

(Row total × Column total) / Grand total

What is the formula for the chi-squared statistic?

Sum of (Observed frequency - Expected frequency)^2 / Expected frequency

How are degrees of freedom calculated when comparing two species?

Total number of species observed - 1

What p-value threshold is typically used to determine statistical significance?

p < 0.05 (less than 5% probability that results are due to chance)

What is the critical chi-squared value required for significance with 1 degree of freedom?

3.841

What is dynamic equilibrium in predator-prey relationships?

A state where predator and prey populations are intertwined, with predator numbers rising and falling in response to prey availability.

What is the typical time lag between prey population peaks and predator population peaks?

1-2 years

What is top-down control in an ecosystem?

Predators control the abundance and distribution of their prey, influencing lower trophic levels.

What is bottom-up control in an ecosystem?

The availability of resources (nutrients/light) affects primary producers, which then influences herbivore and carnivore populations.

Define allelopathy.

A biological phenomenon where an organism produces biochemicals (allelochemicals) that influence the growth, survival, or reproduction of other organisms.

What are the two roles of caffeine in plants like coffee and cacao?

A defense mechanism against herbivores and an inhibitor of competing plant growth.

What are antibiotics in an ecological context?

Allelochemicals produced by microorganisms to kill or inhibit the growth of competing microbial species.

Which fungus produces penicillin?

Penicillium

How does penicillin kill bacteria?

It binds to the enzyme transpeptidase, inhibiting bacterial cell wall synthesis.

What are bacterial cell walls primarily composed of?

Polysaccharides called peptidoglycan.

What is the primary difference between top-down and bottom-up control?

Top-down emphasizes predation and competition, while bottom-up emphasizes resource availability.

What happens to the predator population when prey numbers decline?

The predator population experiences reduced food availability, leading to a decrease in their numbers.

Are allelochemicals always detrimental to other organisms?

No, they can have either inhibitory/detrimental effects or beneficial/stimulatory effects.

What is the result of a chi-squared value being higher than the critical value?

The null hypothesis is rejected, and the results are considered statistically significant.

What is the relationship between the Canada lynx and the snowshoe hare?

A classic example of oscillating predator-prey population cycles in North American boreal forests.

Why is the chi-squared test used in ecology?

To determine if the distribution of two species is random or if there is a significant association between them.

What does 'negative feedback' mean in the context of predator-prey populations?

A regulatory mechanism where an increase in one population eventually leads to a decrease in the other, maintaining balance.

What is the primary function of transpeptidase in bacteria?

It builds the peptidoglycan chains that make up the bacterial cell wall.