Biology Keypoints; BASIC ECOLOGICAL CONCEPTS; These topics are suitable for biology students in the following classes. JAMB, Post-UTME, IJMB and WAEC/NECO students.
Ecology is defined as the study of living organisms in relation to their environment.
The terms associated with an organism in the study of ecology include Environment, Habitat and Ecological niche.
Environment: The environment of an organism consists of factors found in its surroundings that affect it. E.g the food, water and air that it takes in, the animals that prey on it, the diseases that affect it, the physical condition of the place like temperature, light, humidity etc
Habitat: It is the place where an organism lives that is suitable to its way of life. E.g Aquatic habitats (freshwater ponds, streams, Oceans etc), Terrestrial habitats ( bush, farmlands, deserts etc), and Arboreal habitats (tree trunks and tree tops).
Ecological niche: This is when an organism is confined to a particular part of the habitat. E.g A caterpillar and an aphid which live on the same plant occupy different positions (ecological niche) on the plant, the caterpillar leaves on the leaves and feeds on them while the aphid lives on the young shoot and suck sap from it.
ORGANISATION LEVELS IN ECOLOGY
The organisation levels of ecology increase in size and complexity from:
Population – Community – Ecosystem – Biosphere.
- POPULATION: This involves all organisms of the same kind living together in the same habitat. E.g Tilapia fish in a stream, Swarm of bees on a tree.
- COMMUNITY: This involves a population of living organisms living together in a habitat. E.g In a freshwater pond, the community includes microorganisms such as bacteria; animals such as copepods, snails, and fishes; plants such as thread-like algae, reed-like plants etc.
- BIOSPHERE: This is the part of the earth where life is found. The biosphere is the largest and highest level of organisation and is composed of various ecosystems. It includes the part of the hydrosphere, atmosphere and lithosphere.
- The largest number of living organisms is found in the hydrosphere.
- The next largest is found in the lithosphere, mainly on the land surface.
- The atmosphere has the least amount of living organisms.
- ECOSYSTEM: The ecosystem is a self-supporting unit that is made up of a living (biotic component) and a non-living (abiotic component) part.
- Biotic components: these consists of the producers (autotrophs), consumers (heterotrophs) and decomposers (saprophytes).
- Abiotic components: these include sunlight, water, air, inorganic nutrients, temperature, humidity etc.
CHARACTERISTICS OF AN ECOSYSTEM
The flow of energy: this is determined by their feeding relationship ( producers-consumers-decomposers).
Recycling of inorganic nutrients.
- Biomes are natural terrestrial ecosystems.
- The type of vegetation in a biome is determined by climatic factors, especially rainfall and temperature.
- Regions throughout the world which have similar climates have similar biomes. For example:
- In equatorial and tropical areas where the temperature is around all year round, tropical forests occur
- In temperate regions, coniferous and deciduous forests occur
- In cold arctic regions, treeless plains (tundra) occurs
- Forests give way to tropical and temperate grassland when the annual rainfall is low and to deserts when rainfall is extremely low
- Climate also changes with height above sea level; as a result, different biomes occur on a mountainside.
LOCAL BIOMES: The following local biomes are present in Nigeria
- Mangrove swamps: these are forests of small, evergreen, broad-leaved trees growing in shallow, brackish water or wet soil. They are found along coastal regions and river mouths. In Nigeria, mangrove swamps are found in the delta region of Lagos, Bendel, Rivers and Cross River states.
- Tropical rain forests: they are dense and made up of many types of broad-leaved trees that are mostly evergreen. They are mainly in the lowlands but they also extend up to hillslopes to a height of 600 or 900m. In Nigeria, rain forests are found in Oyo, Bendel, Imo, Cross-River, Ogun, Ondo and Rivers states.
- Montane forests: are characterized by low temperatures, high rainfall and high relative humidity. Trees are tall but few and scattered. It is the biotic community of mountains. It is also one of the main biomes of the Nigerian biotic community.
- Savanna: these regions have a hot, wet season which alternates with a cool, dry season. This can be divided into three belts which are:
- The Northern and Southern Guinea savannas: In Nigeria, can be found in the parts of Kaduna, Kwara and Benue states.
- The Sudan savanna: In Nigeria, can be found in Kano, parts of Borno, Sokoto, Niger, and Bauchi states.
- The Sahel savanna: In West Africa, can be found around Lake Chad.
The major biomes of the world include Tropical rainforests, Temperate forests, Coniferous forests, Temperate shrubland, Savanna, Temperate grassland, Desert, Tundra and Mountain vegetation.
Types of Organisms: this lists the various types of populations that are found in the habitat.
Dominant species: In any community, one or a few species are dominant over the others either in number or size or both.
These include population size, frequency, density, percentage cover and distribution.
FACTORS AFFECTING POPULATION
- Migration of organisms to other habitats.
- Invasion or colonization by new species.
- Increase in natality (birth rate) or mortality (death rate).
These factors operate during:
- Seasonal climatic changes.
- Changes in availability of food.
- Breeding periods.
- Unfavourable natural events such as fires, floods and droughts.
CONDUCTING POPULATION STUDIES
- The method of studying the population of a habitat is known as Sampling.
- To study the population of a habitat you pick at random small areas of the habitat and carry out the necessary investigations as you cannot study the whole habitat at once.
To conduct population studies:
- Choose the habitat to be studied.
- Select the sampling method to be used.
- Collect, count and record the different types of organisms present.
- Identify the different organisms (use a key where necessary).
- Repeat the population studies at intervals.
- Collection of Specimen.
- Collection of Plants.
- Quadrat sampling.
- Transect method.
- Keeping collected plants.
- Collection of animals.
- Capture-Recapture method.
- Collection of soil animals.
- Keeping collected animals.
DETERMINING POPULATION CHARACTERISTICS
- FREQUENCY: this can be determined by the total number of times the species appeared in the number of plots covered by the quadrat.
It is calculated by dividing the number of plots in which the species occurs by the total number of tosses of the quadrat and multiplying by a hundred.
- DENSITY: This is calculated by dividing the average number of times the species occurs within the quadrat (frequency per quadrat) by the area of the quadrat.
- PERCENTAGE COVER: This is calculated by multiplying the average area of the cross-section of the stem by the number of plants per quadrat and expressing the product as a percentage.
Abiotic factors determine the type of biotic community found in a habitat.
Abiotic factors common to all habitats include temperature, rainfall, light, hydrogen ion concentration, wind and pressure.
FACTORS AFFECTING AQUATIC HABITATS
These factors include Salinity, density, turbidity, water flow or current, tidal movements and waves, dissolved gases and the nature of the substratum.
FACTORS AFFECTING TERRESTRIAL HABITATS
The main factors that affect terrestrial habitats include Land surface, Soil and Relative humidity.
Other abiotic factors that affect terrestrial habitats include rainfall, temperature, wind, light, pressure and pH.
MEASURING INSTRUMENTS FOR VARIOUS ABIOTIC FACTORS
- Temperature: Thermometer
- Rainfall: Rain gauge
- Light: Photometer
- Relative humidity: Hygrometer
- Wind: Wind-vane
- Pressure: Barometer
- Water depth: Metre rule
- Turbidity: Secchi disc
- Slope: Slope gauge