Grade 11 Life Sciences - Module 7: Population Ecology & Human Impact on the Environment

Comprehensive practice flashcards covering Module 7: Population Ecology and Human Impact on the Environment.

Population

A group of organisms of the same species that occupy the same area at the same time where they can interbreed freely.

Species

A group of organisms with similar characteristics that can interbreed and have fertile offspring.

Habitat

The specific place where the group of organisms making up a population occurs.

Population size

The total number of individuals present in a specific population.

Population density

The number of individuals of a population per unit area (for example, $10\text{ sheep per hectare}$).

Direct techniques

Sampling methods that involve counting every single individual in a population, suitable for large, sessile, stationary, or slow-moving organisms (such as human censuses or aerial counts).

Indirect techniques

Methods that involve counting a representative portion of a population and using that sample to mathematically estimate the total population size.

Mark-recapture method

An indirect population estimation technique in which a first sample is captured, counted, and marked, released to disperse freely, and followed by a second capture to calculate total population size using $P = \frac{M \times S}{T}$.

Quadrat

A square sampling frame of known surface area (such as $1\,\text{m}^2$) placed randomly on the ground to count plants, sessile animals, or slow-moving organisms.

Natality

The birth rate of a population, which causes an increase in population size.

Mortality

The death rate of a population, which causes a decrease in population size.

Immigration

The one-way movement of individuals into a population from another area, causing an increase in population size.

Emigration

The one-way movement of individuals out of a population to another area, causing a decrease in population size.

Closed population

A population with no immigration or emigration occurring, meaning changes in population size are determined solely by births and deaths.

Limiting factors

Specific environmental factors or resources (such as shortage of food, water, space, shelter, or diseases) that prevent unlimited growth by decreasing birth rates or increasing death rates.

Environmental resistance

The combined total of all limiting factors that prevent a population from reproducing at its maximum theoretical rate.

Carrying capacity

The maximum total number of individuals of a population that a specific environment can sustainably support.

Geometric (J-shaped) growth form

A growth pattern characterized by an initial slow lag phase followed by rapid exponential growth under optimum conditions, ending abruptly when environmental resistance takes effect.

Logistic (S-shaped) growth form

A growth pattern characterized by a lag phase, an accelerating exponential phase, a decelerating phase, and an equilibrium phase that stabilizes around the carrying capacity.

Lag phase

An initial period of slow population growth where individuals adapt to a new habitat, mature sexually, and locate mates.

Exponential phase

A phase in which a population grows rapidly and doubles at regular intervals because environmental resistance is minimal or absent.

Stationary phase

An equilibrium phase in logistic growth where population numbers remain relatively constant, stabilizing around the carrying capacity because natality approximately equals mortality.

Density-independent factors

Limiting factors that regulate population size regardless of how crowded the population is, such as extreme rainfall, temperature fluctuations, and natural disasters.

Density-dependent factors

Limiting factors that take greater effect as population density rises, such as intraspecific resource competition, predator detection, and parasite transmission.

Stable population

A population whose numbers fluctuate consistently around the carrying capacity of its environment.

Unstable population

A population that experiences habitat deterioration, leading to a lowered carrying capacity and an increased mortality rate.

Predation

A feeding interaction where one organism (the predator) hunts, kills, and consumes another organism (the prey).

Intraspecific competition

Competition occurring between individuals of the same species for limited resources such as food, water, territory, or mates.

Interspecific competition

Competition occurring between individuals of different species in the same habitat that rely on shared, limited resources.

Competitive exclusion

The ecological principle stating that two species requiring the exact same limited resource cannot occupy the same ecological niche indefinitely, resulting in one species outcompeting the other to extinction or emigration.

Resource partitioning

The coexistence of competing species in the same habitat made possible by utilizing resources differently, such as feeding at different times of day or foraging at different heights.

Mutualism

A symbiotic relationship between two different species in which both organisms benefit from the interaction.

Commensalism

A symbiotic relationship between two different species in which one organism benefits while the other is neither helped nor harmed.

Parasitism

A symbiotic relationship between two different species in which one organism (the parasite) benefits at the direct expense of the other (the host), which is harmed.

Fertility rate

The number of births per $1000$ female individuals of child-bearing age ($15\text{--}44\text{ years}$) per year.

Population pyramid

A graphical diagram used to represent the age structure and gender distribution of a population.

Age structure distribution

The proportion or number of individuals belonging to pre-reproductive, reproductive, and post-reproductive age groups within a population.

Greenhouse gases

Atmospheric gases—such as carbon dioxide ($CO_2$), methane ($CH_4$), nitrous oxide ($N_2O$), and water vapour—that absorb and trap infrared heat radiating from the Earth.

Greenhouse effect

The natural process wherein atmospheric gases absorb, reflect, and re-radiate thermal energy, maintaining a warm, stable global temperature suitable for life.

Global warming

The rapid increase in average global temperatures caused primarily by excessive emissions of greenhouse gases from human industrial and agricultural activities.

Climate change

Significant, long-term shifts in regional or planetary weather patterns, temperature, rainfall, and air pressure observed over a period of $30\text{ to }50\text{ years}$.

Carbon footprint

The total amount of greenhouse gases, expressed in tons of carbon or $CO_2$ released per year, generated by human activities.

Carbon sinks

Natural reservoirs, particularly forests and oceans, that accumulate and store large amounts of atmospheric $CO_2$ through photosynthesis.

Deforestation

The extensive cutting down or burning of forests, which removes vital carbon sinks and contributes up to $20\%$ of global greenhouse gas emissions.

Desertification

The land degradation process by which semi-arid or arid regions lose their vegetation cover and are transformed into desert due to human pressures and climate stresses.

Ozone layer

A protective layer in the stratosphere that absorbs harmful ultraviolet ($UV\text{-}B$) radiation from sunlight before it strikes Earth.

Wetland

A piece of land saturated by surface water or groundwater, characterized by waterlogged soil, aquatic vegetation, natural pollutant filtration, and flood control.

Eutrophication

The excessive accumulation of nutrients (especially nitrogen and phosphorus) in aquatic ecosystems, resulting in algal blooms, sunlight obstruction, bacterial decomposition, and oxygen depletion.

Food security

A nation's capacity to provide all individuals with physical and economic access to sufficient, safe, and nutritious food to maintain a healthy life.

Biological control

A pest management method that utilizes a pest's natural natural enemies, such as predators or parasites, to control its population without chemical damage.