CARA'S TIPSEcology II: habitats, populations, nutrient cycles, soil, ecological factors
JAMBWAECNECO
What the syllabus asks
JAMB: Ecology: factors affecting distribution of organisms, ecological instruments, population, nutrient cycling, soil
WAEC: Ecology: ecological factors (abiotic and biotic) and their measurement, habitats (aquatic and terrestrial) and adaptations, population studies (estimating population size, density, factors affecting population), nutrient cycling (carbon, nitrogen, water cycles), soil (formation, types, properties, fertility), ecological succession
NECO: Ecology: ecological factors (abiotic and biotic) and their measurement, habitats (aquatic and terrestrial) and adaptations, population studies (estimating population size, density, factors affecting population), nutrient cycling (carbon, nitrogen, water cycles), soil (formation, types, properties, fertility), ecological succession
What you will learn
- Distinguish between abiotic and biotic factors and describe how each affects organisms.
- Name instruments for measuring ecological factors and state what each measures.
- Describe adaptations of organisms to aquatic and terrestrial habitats.
- Estimate population size using quadrats and capture–recapture, and explain factors that change populations.
- Describe the carbon, nitrogen and water cycles.
- Describe soil formation, components, types and fertility.
- Explain ecological succession.
Key points
- Abiotic factors: temperature, water, light, wind, pH, salinity, soil; biotic: predation, competition, parasitism, mutualism, disease, humans.
- Instruments: thermometer, rain gauge, hygrometer, anemometer, wind vane, light meter, pH meter, secchi disc, hydrometer.
- Aquatic organisms have gills, streamlining, air spaces; mangroves have stilt roots and pneumatophores.
- Dry-land organisms reduce water loss: thick cuticles, spines, deep roots, concentrated urine.
- Quadrats estimate plants; capture–recapture N = n₁n₂/m estimates animals.
- Growth curve: lag, log, stationary, decline.
- Carbon cycle: photosynthesis removes CO₂; respiration, decay, combustion add it.
- Nitrogen cycle: fixation, ammonification, nitrification (Nitrosomonas then Nitrobacter), denitrification.
- Soil: mineral particles, humus, water, air, organisms; loam is best; sand drains fast, clay waterlogs.
- Succession: pioneer → seral stages → climax; primary on bare rock, secondary on cleared soil.
Start here: Ecological factors: abiotic and biotic
Why do mangrove trees grow along the creeks of the Niger Delta but not in the Sahel? Why do mosquitoes multiply in the rainy season? The answers lie in ecological factors, the conditions that decide where organisms can live and how many of them there are.
Abiotic factors
- Temperature affects enzyme activity, so it controls growth and activity. Lizards bask in the morning sun to warm up.
- Rainfall and humidity decide how much water is available. They separate the rainforest of the south from the savanna of the north.
- Light is needed for photosynthesis and controls the flowering and behaviour of many organisms.
- Wind increases transpiration and disperses seeds and pollen.
- pH of soil and water affects which plants and animals can live there.
- Salinity (saltiness) separates freshwater from marine life.
- Soil type and topography (slope, altitude) also matter. The Jos Plateau is cooler than Lafia because it is higher.
Biotic factors
- Predation: hawks eat chicks; predators control prey numbers.
- Competition: weeds compete with maize for light, water and nutrients.
- Parasitism: ticks feed on cattle and weaken them.
- Mutualism: rhizobium bacteria in groundnut root nodules fix nitrogen while receiving food.
- Disease and human activity (bush burning, deforestation, pollution).
Show solution
Continue this lesson in the free app →
Practice questions
- leguminous plants
- grasses
- cassava
- palms
Show answer
A: leguminous plants
Rhizobium in legumes (beans, groundnut) fixes atmospheric nitrogen.
- nitrification
- nitrogen fixation
- ammonification
- denitrification
Show answer
D: denitrification
Denitrifying bacteria return N₂ to the air, often in waterlogged soils.
- the physical environment
- a food chain
- all the organisms of one species in an area
- all the species in an area
Show answer
C: all the organisms of one species in an area
For example, all the tilapia in a pond.
- a habitat
- all the populations of different species in an area
- one species
- non-living factors
Show answer
B: all the populations of different species in an area
Living organisms together.
- Temperature
- Predators
- Parasites
- Competition
Show answer
A: Temperature
Non-living.
Key words
- Ecology
- The study of living things in relation to each other and their environment.
- Habitat
- The place where an organism lives.
- Population
- All organisms of one species in an area.
- Community
- All the populations living together in an area.
- Ecosystem
- A community interacting with its non-living environment.
- Niche
- The role of an organism in its ecosystem.
- Abiotic factor
- A non-living factor such as temperature or pH.
- Biotic factor
- A living factor such as predation or competition.
- Quadrat
- A square frame used to sample organisms.
- Population density
- Number of individuals per unit area or volume.
- Nitrogen fixation
- Conversion of nitrogen gas into nitrogen compounds.
- Nitrification
- Conversion of ammonia to nitrites then nitrates by bacteria.
The Cara's Tips app teaches every topic from the very basics, with quick checks, worked examples and exam practice. It works offline.
Open this lesson in the free appDownload for Android