All interacting populations of different species in a given area, together with the abiotic environment, constitute an ecosystem. (Note: the community is all populations; ecosystem includes community plus abiotic factors.)
Eurytherms tolerate a wide range of temperatures. Stenotherms tolerate only a narrow temperature range.
Answer: (a) Predation.
Explanation: In predation the predator benefits by killing and consuming the prey, which is harmed.
In predation and parasitism one partner benefits (+) while the other is harmed (−); thus the interaction is (+, −).
Inter-specific competition can lead to the competitive exclusion of a less fit species and eventual local extinction if they compete for the same limited resources.
r-selected species (r-strategists) produce large numbers of small offspring, reproduce early and have high population growth potential; insects are typical r-selected organisms.
A (Mutualism) — sea anemone on hermit crab (both benefit); B (Commensalism) — barnacles on whales (barnacles benefit, whale unaffected); C (Parasitism) — round worm and man (parasite benefits, host harmed); D (Competition) — birds and squirrels competing for nuts; E (Predation) — lion and deer (predator-prey).
In the typical response diagram: a Regulator maintains a nearly constant internal level despite external change (A); a Conformer’s internal level varies with the external level (B); a Partial regulator shows intermediate control (C).
Remoras or sucker fish attach to sharks, gaining transport and food scraps while the shark is generally unaffected — this is commensalism.
r-selected species produce many small offspring, have early maturity and low parental care — maximizing reproductive rate (r).
Catadromous species (e.g., some eels) live in fresh water and migrate to the sea to spawn. Anadromous species do the opposite (sea → freshwater).
To maintain homeostasis organisms 'regulate' — they use physiological or behavioural mechanisms to keep internal conditions relatively constant despite external changes.
Habitat describes the physical location and environmental conditions (abiotic and biotic) that support an organism — including shelter, food, water and mates.
A habitat is the specific place or physical environment where an organism or a population normally lives and obtains resources (e.g., pond for a frog, oak tree for a woodpecker).
Niche encompasses the species’ requirements (food, space, environmental conditions) and its interactions (competition, predation, mutualism) — often described as the species' 'way of life'.
An ecological niche is the role or functional position of a species in an ecosystem — including its habitat, resource use, interactions with other species and contribution to energy flow and nutrient cycling.
Acclimatisation occurs within the lifetime of an organism and helps maintain performance under new conditions; it is not genetic adaptation.
Acclimatisation is the reversible physiological, morphological or behavioural adjustment of an individual organism to changes in its environment (e.g., increased red blood cells at high altitude).
Factors in pedogenesis include parent material, climate, organisms, topography and time, producing distinct soil horizons and properties.
Pedogenesis is the process of soil formation from parent rock through physical, chemical and biological weathering and organic matter accumulation.
High permeability (sandy soils) allows rapid drainage; low permeability (clay soils) restricts water movement and aeration.
Soil permeability is the ability of soil to allow water and gases to pass through its pore spaces; it depends on texture, structure and pore connectivity.
Eurytherms (e.g., cockroaches) can survive large temperature fluctuations and are widely distributed; stenotherms (e.g., polar fish) have narrow thermal tolerance and restricted distribution.
Eurytherms tolerate a wide range of temperatures; stenotherms tolerate only a narrow temperature range.
Hibernation helps animals survive cold and food scarcity by conserving energy. Aestivation helps survival during high temperature or drought by reducing metabolic activity and water loss.
Hibernation is a seasonal winter dormancy with lowered metabolic rate and body temperature (example: bears, ground squirrels). Aestivation is a summer dormancy to avoid heat and desiccation (example: lungfish, some snails and amphibians).
Key characters: large scale (global or regional), defined by climate and vegetation (e.g., tropical rainforest, desert, tundra), characteristic fauna and flora adapted to conditions, distinct ecological communities and nutrient cycles, and predictable patterns of distribution and productivity.
A biome is a large geographical area with characteristic climate, vegetation and animal communities; features include dominant plant life-form, climate patterns (temperature, rainfall), soil type, zonation and similar ecological processes.
Major classification: - By salinity: - Freshwater (low salinity): lakes, ponds, rivers, streams, wetlands (marshes, swamps, bogs). - Brackish (intermediate salinity): estuaries, mangrove swamps. - Marine (high salinity): open ocean, coastal seas, coral reefs. - By habitat/zone within aquatic systems: - Lentic (standing water): ponds, lakes—zones: littoral (near shore), limnetic/epilimnion (open surface), profundal/benthic (deep). - Lotic (flowing water): rivers and streams—zones: headwaters, midstream, downstream. - Marine vertical/horizontal zones: intertidal (littoral), neritic (coastal shelf), pelagic/oceanic (open sea), benthic (sea floor), abyssal (deep ocean). - Special habitats: coral reefs (high biodiversity), estuaries and mangroves (productive, nursery grounds). Key terms: lentic, lotic, estuary, benthic, pelagic, intertidal, coral reef.
Aquatic biomes are classified by salinity and habitat type: freshwater, brackish, and marine; and by physical zones (lentic/lotic, pelagic/benthic, intertidal, etc.).
Main responses to abiotic factors: - Tolerance: species survive within a range of an abiotic factor (tolerance limits, optimum). - Regulation vs conformation: regulators maintain internal constancy; conformers change internal state with environment. - Migration: seasonal or daily movement to avoid adverse conditions (birds, fish). - Dormancy: hibernation (cold), aestivation (heat/drought) or seed dormancy to survive extremes. - Acclimatization (physiological plasticity): reversible adjustments (e.g., increased red blood cells at high altitude). - Morphological adaptations: insulating fur, fat, leaf shape, root systems. - Behavioral adaptations: burrowing, basking, nocturnality. Key terms: tolerance limits, regulator, conformer, acclimatization, dormancy.
Organisms respond by tolerance, migration, dormancy (hibernation/aestivation), acclimatization, physiological and morphological adaptations, and behavioral changes.
Classification with brief examples: - Morphological (structural): body shape, limbs, fur, beaks, leaves (e.g., thick fur in arctic mammals). - Physiological (functional): metabolic rates, temperature regulation, osmoregulation, antifreeze proteins in polar fish. - Behavioral: migration, territoriality, foraging strategies, nocturnality. - Reproductive/developmental: timing of breeding, parental care, seed dormancy, amniotic egg in terrestrial vertebrates. - Biochemical/ molecular: pigment production, enzyme adaptations to temperature, venom. Key terms: morphological, physiological, behavioral, reproductive, biochemical.
Adaptive traits: morphological (structural), physiological (functional), behavioral, reproductive/developmental, and biochemical adaptations.
Differences: - Definition: Natality = births added to a population per time; Mortality = deaths removed from a population per time. - Measure: natality often expressed as births per 1000 individuals per year or per capita birth rate (b); mortality expressed as deaths per 1000 per year or per capita death rate (d). - Effect on population: natality contributes to population growth; mortality causes decline. - Influencing factors: natality affected by fecundity, age at reproduction; mortality influenced by predation, disease, age structure, environmental stress. Key terms: birth rate, death rate, per capita rate, fecundity.
Natality (birth rate) is the number of births per unit population per time; Mortality (death rate) is the number of deaths per unit population per time. Natality increases population size; mortality decreases it.
Comparison: - J-shaped (exponential) growth: dN/dt = rN; population grows exponentially when resources are unlimited; curve rises rapidly producing a J-shape; example: introduced species in new habitat, early microbial growth. - S-shaped (logistic) growth: dN/dt = rN(1 − N/K); growth slows as population approaches carrying capacity K due to limiting resources; phases: lag, exponential, deceleration, stable equilibrium at K; plot is sigmoid (S-shaped). - Key differences: presence of carrying capacity (absent in J, present in S), long-term stability (unstable runaway in J, self-regulated in S). Key terms: exponential growth, logistic growth, carrying capacity (K), intrinsic rate (r).
J-shaped curve = exponential growth (no carrying capacity); S-shaped curve = logistic growth (includes carrying capacity K).
Main concepts: - Carrying capacity (K): maximum population size an environment can sustain; as N approaches K, resources limit growth. - Density-dependent factors: increase in effect with population density and regulate population via negative feedback: - Intraspecific competition for food, mates, space. - Predation: predators limit prey as prey density rises. - Disease and parasitism: transmission rates higher at high density. - Waste accumulation and reduced reproductive rates. - Density-independent factors: affect population regardless of density: severe weather, climate change, natural disasters, human activities. - Intrinsic biological mechanisms: territoriality, social hierarchy, delayed reproduction, stress-induced reproductive suppression. - Population cycles and oscillations: predator–prey interactions and time-lagged responses can cause regular cycles (e.g., hare–lynx). - Human influence: habitat alteration, hunting, introduction of competitors/predators. Overall regulation is interplay of environmental limits and biological responses producing dynamic equilibrium or oscillations around K. Key terms: carrying capacity, density-dependent, density-independent, negative feedback.
Population regulation occurs via density-dependent factors (competition, predation, disease), density-independent factors (weather, catastrophes), intrinsic biological mechanisms (territoriality, social behavior), and carrying capacity (K) leading to negative feedback on growth.
Aspects of soil: - Physical properties: - Texture: relative proportions of sand, silt and clay determine particle size and influence drainage and aeration. - Structure: arrangement of soil particles into aggregates (granular, blocky, platy) affecting root penetration and water movement. - Porosity and permeability: pore space governs water holding capacity and aeration. - Moisture content and water retention: influences plant-available water. - Chemical properties: - pH: acidity or alkalinity affects nutrient availability and microbial activity. - Nutrient content: levels of nitrogen (N), phosphorus (P), potassium (K), and micronutrients. - Cation exchange capacity (CEC): soil’s ability to hold and exchange positively charged ions (Ca2+, Mg2+, K+, Na+). - Organic matter/humus: improves structure, water retention and nutrient supply. - Biological properties: - Soil biota: bacteria, fungi, actinomycetes, protozoa, nematodes, earthworms contribute to decomposition, nutrient cycling and soil structure. - Biological activity affects humus formation and nutrient mineralization. - Soil profile/horizons: O (organic), A (topsoil), B (subsoil), C (parent material) horizons determine fertility and rooting depth. Key terms: texture, structure, porosity, pH, CEC, humus, horizons.
Soil properties include physical (texture, structure, porosity, moisture), chemical (pH, nutrient content, cation exchange capacity, organic matter), biological (microflora, fauna, humus), and horizons/profiles.
Comparison: - Location: Tundra — high latitudes/Arctic and Alpine regions; Taiga — just south of tundra across northern continents (boreal belt). - Climate: Tundra — extremely cold, long winters, very short, cool summers; Taiga — cold winters but milder than tundra, longer growing season, more precipitation (snow). - Vegetation: Tundra — low-growing plants: mosses, lichens, sedges, dwarf shrubs; permafrost restricts deep roots. Taiga — dense coniferous forests (spruce, fir, pine), some deciduous trees. - Soil: Tundra — permafrost, poor drainage, thin active layer; Taiga — podzolic/acidic soils, better-drained but nutrient-poor. - Fauna: Tundra — caribou/reindeer, arctic fox, lemmings, migratory birds; Taiga — moose, bears, wolves, lynx, many bird species. - Biodiversity & productivity: Tundra lower biodiversity and primary productivity than taiga. Key terms: permafrost, boreal forest, coniferous.
Tundra: treeless, cold, permafrost, low biodiversity, short growing season. Taiga (boreal forest): dominated by coniferous trees, slightly warmer, acidic soils, more biomass and longer growing season than tundra.
Common adaptations: - Locomotion: development of limbs for running, grasping; wings for flight; specialized feet/pads for climbing. - Respiration: lungs with large surface area, respiratory pigments (hemoglobin). - Water economy: efficient kidneys (urine concentration), impermeable integument, behavioral water conservation (nocturnality). - Thermoregulation: endothermy with insulation (fur, feathers), vasomotor control, sweating/panting; ectotherms use basking/shuttling. - Protection & camouflage: coloration, protective armor (scales), cryptic coloration and mimicry. - Reproduction: internal fertilization, amniotic egg, parental care to reduce desiccation and predation of young. - Sensory & behavioral: acute vision/hearing, burrowing, migration, hibernation. Key terms: amniotic egg, endothermy, osmoregulation, cryptic coloration.
Terrestrial animal adaptations include locomotory (limbs, wings), respiratory (lungs), water conservation (kidney, excretion), thermoregulation (insulation, sweating), protective coverings (skin, scales, fur), reproductive (internal fertilization, amniotic egg), behavioral (burrowing, nocturnality), and sensory adaptations.
Details: - Components: age classes usually: pre-reproductive (young), reproductive (mature), post-reproductive (old). - Age pyramid types: - Expanding (broad base): high proportion of young → rapid growth. - Stable (rectangular): similar proportions across ages → zero growth or replacement-level fertility. - Declining (narrow base): fewer young → population decline. - Importance: age distribution determines population momentum, future growth potential, dependency ratios and management strategies. - Measurement: constructed from census data; used in demography and ecology to predict birth/death rates and resource needs. Key terms: pre-reproductive, reproductive, post-reproductive, age pyramid, population momentum.
Population age distribution shows proportions in pre-reproductive, reproductive and post-reproductive age classes; depicted as age pyramids indicating expanding, stable or declining populations and predicting growth trends.
Models: - Exponential (geometric) model: - Equation: dN/dt = rN where N = population size, r = intrinsic rate of increase. - Features: constant per capita growth rate, unlimited resources, J-shaped curve, unrealistic long-term. - Logistic model: - Equation: dN/dt = rN(1 − N/K) where K = carrying capacity. - Features: growth slows as N approaches K, phases of lag, exponential, deceleration and stable equilibrium at K; S-shaped (sigmoid) curve. - Other considerations: age-structured models (Leslie matrix), metapopulation models (patch dynamics), and predator–prey oscillatory models (Lotka–Volterra). Key terms: intrinsic rate (r), carrying capacity (K), logistic, exponential, Leslie matrix, Lotka–Volterra.
Two primary growth models: exponential (geometric) growth dN/dt = rN producing J-shaped curve, and logistic growth dN/dt = rN(1 − N/K) producing S-shaped (sigmoid) curve with carrying capacity K.
Tabulated summary (interaction — effect on species A / effect on species B — brief example and ecological note): - Competition (− / −): both harmed; example: two plant species competing for light and nutrients; leads to competitive exclusion or resource partitioning. - Predation (− / +): predator benefits, prey harmed; example: lion ( + ) / zebra ( − ); regulates prey population and drives adaptations. - Parasitism (− / +): parasite benefits, host harmed (often not immediately killed); example: tapeworm/vertebrate host. - Mutualism (+ / +): both benefit; example: pollinator (bee) and flowering plant; can be obligate or facultative. - Commensalism (+ / 0): one benefits, other unaffected; example: epiphytic orchids on trees (orchid +, tree 0). - Amensalism (− / 0): one harmed, other unaffected; example: black walnut secreting juglone inhibiting nearby plants. - Neutralism (0 / 0): no significant effect on each other; rare in nature. Analysis: interactions influence population sizes, community structure, coevolution and niche partitioning. Outcomes depend on interaction strength, environmental context and availability of resources; some interactions can shift (e.g., mutualism to parasitism) depending on conditions. Key terms: competition, predation, parasitism, mutualism, commensalism, amensalism, niche partitioning, competitive exclusion.
Major two-species interactions: competition (−/−), predation/parasitism (−/+), mutualism (+/+), commensalism (+/0), amensalism (−/0), neutralism (0/0).