Mr G Science chapter 2 notes

Abiotic factor = Non-living physical or chemical element of an ecosystem (e.g., temperature, light, pH).

Biotic factor = Living component of an ecosystem affecting organisms (e.g., predators, competition).

Population = Group of individuals of the same species living in a specific area.

Population density = Number of individuals per unit area.

Natality = Birth rate in a population.

Mortality = Death rate in a population.

Limiting factors = Environmental factors that restrict population growth (e.g., food, water, space).

Carrying capacity (K) = Maximum population size an environment can sustainably support.

Biotic potential = Maximum reproductive capacity of a population under ideal conditions.

r-selected species = Species with many offspring, low parental care, rapid growth (e.g., insects).

K-selected species = Species with few offspring, high parental care, populations near carrying capacity (e.g., elephants).

S-curve = Population growth that slows and stabilizes at carrying capacity due to limiting factors.

J-curve = Exponential population growth without leveling off, usually unsustainable.

Fundamental niche = Full potential habitat of a species without competition or limiting factors.

Realized niche = Actual habitat occupied by a species, limited by competition or other factors.

Example fundamental vs realized niche = Balanus barnacles live across wide rocky shore (fundamental), but restricted to lower shore due to Chthamalus competition (realized).

Predation = One species hunts and eats another.

Example predation = Lion (Panthera leo) preying on zebra (Equus quagga).

Herbivory = Animal feeds on plants.

Example herbivory = Eastern cottontail rabbit (Sylvilagus floridanus) eating grasses.

Parasitism = One organism benefits, other is harmed.

Example parasitism = Tapeworm (Taenia solium) in human intestines.

Mutualism = Both species benefit.

Example mutualism = Clownfish (Amphiprion ocellaris) and sea anemone (Heteractis magnifica).

Competition = Species compete for the same limited resource, harming both.

Example competition = Red squirrel (Sciurus vulgaris) vs. grey squirrel (Sciurus carolinensis) for habitat.

Energy flow = Transfer of energy through trophic levels in an ecosystem.

Producers = Autotrophs that create organic matter from sunlight or chemicals.

Consumers = Organisms that eat producers or other consumers for energy.

Decomposers = Organisms that break down dead matter (e.g., fungi, bacteria).

Bioaccumulation = Build-up of toxins in an organism over time.

Biomagnification = Increase in toxin concentration at higher trophic levels.

Example bioaccumulation/biomagnification = Mercury accumulating in tuna fish.

Food chain example = Grass → Grasshopper → Frog → Snake → Decomposer.

Deforestation impact = Removes producers, reduces energy flow, releases CO₂, disrupts carbon and nitrogen cycles.

Temperature = Measured with thermometer.

Light intensity = Measured with lux meter.

Soil pH = Measured with pH meter or test kit.

Water availability = Measured with soil moisture probe.

Nutrient levels = Measured with chemical soil/water tests.

Denitrification = Bacteria convert nitrates into nitrogen gas, returning N₂ to atmosphere.

Nitrogen fixation = Conversion of nitrogen gas into nitrates by bacteria or lightning.