Nigerian Biomes: Mangrove, Rain Forests & Savanna

• Biomes are large natural terrestrial ecosystems, identified by their dominant vegetation
• They are terrestrial because plants form the bulk of the community
• Climatic factors like rainfall, relative humidity, temperature, wind, and light determine the type of vegetation in a biome

Local Biomes in Nigeria

• Mangrove swamps, tropical rain forests and savanna are local biomes particular to Nigeria

Mangrove Swamps

• They are found in the tropics along coastal regions and river mouths
• They are forests of small, evergreen, broad-leaved trees growing in shallow, brackish water or wet soil
• Mangrove trees possess prop roots and breathing roots called pneumatophores
• The climate is hot and wet, with a total annual rainfall above 250cm and temperature about 26°c
• In Nigeria, mangrove swamps are in the delta region of Lagos, Delta, Rivers, Bayelsa, and Cross River states

Tropical Rain Forests

• Occur in the region between the equator and latitude 5°-10°N and S
• The forests are mainly lowland
• Climate is hot and wet
• Consist of mostly evergreen broad-leaved trees that gradually shed and replace leaves throughout the year
• Trees form canopy strata with low light intensity, high humidity, and damp floors
• Trees possess thin bark
• The forest is rich in epiphytes and wood climbers
• Annual rainfall and temperature are 200cm and 27°c, respectively
• Tropical rainfall in Nigeria is found in Edo, Delta, Ondo, Imo, Lagos, Rivers state, etc

Savanna

• These are tropical grasslands in Africa, usually flat for miles and made up mainly of grasses
• Has hot, wet seasons (29°c) alternating with cool, dry seasons (18°c)
• Total annual rainfall is about 50cm-150cm
• During the dry season, grasses are dry and brown, and bush fires are common
• South Guinea savanna, the largest biome in Nigeria, has tall grasses with scattered deciduous trees, found in Enugu, Kogi, Benue, Kwara, Oyo, Osun, Ekiti State, etc
• Northern Guinea Savanna has scattered deciduous trees, sometimes with thorns, and short, numerous grasses, located in Plateau, Kaduna, Bauchi, Niger, Kano, Adamawa states, etc
• Sudan savanna has shorter grasses and fewer, more scattered trees, found in Kano and parts of Borno, Sokoto, Niger, and Bauchi states
• Sahel savanna has high temperatures and low rainfall with short, scanty grasses and tough shrubs or trees, with drought-resistant plants, located in Borno, Kastina, Sokoto, Yobe, Kano, Jigawa states, etc

World Biomes

• Abiotic factors like temperature and rainfall determine the world biomes
• World biomes include tropical rain forests, temperate forests, coniferous forests, temperate shrubland, savanna, temperate grassland, desert, tundra, and montane vegetation

Temperate Forests

• These forests have broad-leaved deciduous trees that shed leaves in winter
• These forests have a moderately wet climate with a dry or cold season

Coniferous Forests

• Coniferous forests have needle-leaved evergreen conifers like pines and firs
• They possess few trees
• They possess tall trees forming an upper story
• The forest floor is covered with a thick layer of conifer needles
• They have a cool climate with light rainfall and snow

Temperate Shrubland

• Consists of drought-resistant shrub plants and dwarf trees, often fire-resistant
• Enjoys a temperate climate with low rainfall

Temperate Grassland

• Perennial grasses grow on very fertile soil, supporting herds of grazing mammals
• Located in moderately dry climates with cold winters and hot summers

Savanna

• Tropical grassland with scattered trees and infertile soil
• Experiences a moderately dry climate with a warm, dry season and a hot, rainy season

Desert

• Has sparse vegetation with succulent perennials that have deep root systems
• Located in tropical, temperate, and afro-alpine regions with less than 25 cm annual rainfall

Tundra

• Treeless marshy vegetation composed mainly of dwarf shrubs, grasses, lichen, and moss, with few trees
• Has a cold climate with long, icy winters and a short summer with an average temperature of 10°c

Montane Vegetation

• Evergreen rainforests are located on mountain slopes, less luxuriant than tropical rainforests
• Afro-alpine vegetation found above 3000m on mountains and consists of heath, grasses, and sedges

Population Characteristics

• Include population size, density, frequency, percentage cover, and distribution
• Population size indicates the quantity of organisms of one species living together in an area at a specific time
• Population density measures a species' number per unit area or volume of habitat using the formula: Population size / Area of habitat
• Population frequency refers to the recurrence of an organism within a set area or habitat
• Percentage cover refers to how much space or area an organism occupies in its habitat
• Population growth rate is the net result of natality (birth rate) and mortality (death rate)
• Population distribution refers to how individuals of a species are arranged in a habitat, either randomly, evenly, or clumped

Factors Affecting Population

• Natality. The ability of organisms to reproduce increases population
• Mortality; Death rate
• Immigration; Movement of organisms from different habitats into a new habitat, increasing the population
• Emigration; Movement of organisms out of a habitat due to unfavourable conditions, decreasing the population
• Availability of food; Animals migrate to areas with plenty of food, increasing the population
• Seasonal climatic changes; determines if organisms stay or migrate
• Breeding season; some organisms move out of their habitats, decreasing the population
• Natural disasters; such as fire, drought, floods, and earthquakes, lead to a decrease in population through death

Measurement of Ecological Factors via Instruments

• Photometer measures light intensity
• Hydrometer measures light intensity in water
• Wind vane measures direction of wind
• Anemometer measures speed of wind
• Rainguage measures amount of rainfall
• Hygrometer measures relative humidity
• Barometer measures pressure
• Glass thermometer; measures temperature
• Colorimeter or pH scale; measures acidity or Alkalinity
• Secchi disc measures turbidity
• Sweep insect net catches insects

Feeding Relationships

• Organisms obtain energy and nutrients from the environment, forming feeding relationships
• This makes the ecosystem a functional unit
• Biotic communities are divided into producers (autotrophs), consumers (heterotrophs), and decomposers
• Autotrophs provide food for other organisms, like grasses, trees, shrubs, phytoplankton and seaweeds
• Heterotrophs include herbivores (primary consumers) that feed on plants, carnivores (secondary consumers) that feed on primary consumers, and omnivores (tertiary consumers) that feed on secondary or both
• Terrestrial heterotrophs include cows, dogs, lions, and humans, while aquatic heterotrophs include water fleas, tadpoles, larvae of insects, and fishes
• Decomposers, such as termites, larvae of houseflies, bacteria, and fungi, break down dead organic matter to release simple chemical compounds
• Consumers generally have a better chance of survival than the other biotic groups

Trophic Levels

• Energy and nutrients are transferred gradually among organisms along a feeding pathway
• The feeding pathway starts with a producer, like green plants or grass
• The producer is consumed by a primary consumer, like zebra or goat
• The primary consumer is eaten by a secondary consumer, like lion
• Decomposers turn dead producers and consumers' remains into inorganic substances that return to the non-living environment
• The trophic level pertains to each step along a feeding pathway
• The arrangement of trophic levels represents the path of energy flow among functional groups of organisms
• Trophic levels are numbered in ascending order, from one to indicate the path of energy flow
• Trophic level 1: producers or autotrophs
• Trophic level 2: primary consumers,
• Above trophic level 2 consumers can be carnivores, parasitic organisms, and scavengers
• The final consumers die and are fed upon by decomposers

Food Chain and Food Web

• A food chain transfers energy from producers to consumers
• Examples of terrestrial food chains includes: grass -> zebra -> lion
• Examples of aquatic food chains includes: Spirogyra -> tadpoles -> crabs -> kingfish
• Food energy is transferred from one organism to another in a linear form
• Food webs involve complex feeding relationships among organisms in the same environment
• A single plant could be fed upon by more than one or two organisms

Energy Flow and Ecological Pyramid

• Pyramids are diagrammatic representations in ecology, including pyramid of number, pyramid of energy and pyramid of biomass
• Pyramid of number represents the number of individual organisms at each trophic level, decreasing from the first to the last
• Pyramid of energy represents of energy present in the living organisms, decreasing from the first to the last
• Pyramid of biomass refers to the size and numbers of living organisms. Represents the total mass of the organisms in each trophic level

Energy Loss in the Ecosystem

• The ability to do work is known as energy
• All living organisms obtain energy from the food they eat
• Energy is progressively lost due to respiration and as heat down the food chain
• In most ecosystems, only about 1 - 10% of the solar energy is available to photosynthetic producers

Laws of Thermodynamics

• Thermodynamics means heat change
• The first law states that energy can neither be created nor destroyed but can change from one form to another
• The second law states that during energy conversion, there is always a decrease in the amount of useful energy and no transformation is 100 percent efficient
• During metabolic activities, some chemical energy is lost as heat energy from the body, so there will always be energy loss

Associations and Their Features

Symbiosis or Mutualism (+ +)

• Both populations benefit, and at least one relies on the other for a critical resource or function to survive

Examples of Symbiosis

• Lichen: mutualistic association between algae and fungus
  • Algae photosynthesizes using its thallus
  • Fungus gets ready-made food from the alga that absorbs rainwater that is used to photosynthesize
• Protozoa in the digestive tract of termites. Protozoa digests the cellulose in the food while protozoa are protected by the termites
• Nitrogen-fixing bacteria in the root nodules of leguminous plants called Rhizobium leguminosarium grow, multiply, and reproduce, directly fixing nitrogen into plants, increasing nitrogen requirement
• Micro-organisms in the intestinal tract of ruminants found in cattle, sheep and goat help to digest cellulose to sugars, synthesize amino acids and minerals for the organism
• Flower and insects Insects obtains food from flowers in the form of pollen and nectars while in return the insects cross-pollinate the plant

Protocooperation (+ +)

• Association between different species where both are mutually benefited but can survive individually
• This association is not obligatory

Examples of Protocooperation

• Sea anemone and hermit crab. Sea anemone provides camouflage protection to the hermit crab against predators while the hermit crab transports it to feeding ground to help it get food.
• Plover and crocodile: Plover (Pluvianus aegyptius) enters the mouth to feed on parasitic leeches. In doing so the plover obtains food and it is also freed from leeches.
• Cattle and egret: These birds feeds on parasites on the body of cattle. As the cattle benefits from parasite removal, the egret benefits by gaining food.

Commensalism (+ 0)

• Association between two organisms where only one (commensal) benefits and the other is neither harmed nor benefits

Examples of Commensalism

• Shark and Remora fish; the remora fish is attaches itself to a shark which is neither harmed nor benefits
• Oyster and crabs; a crab inhabits an oyster shell for protection and no oyster harm done
• Man and intestinal bacteria; the bacteria feeds on digested food and provides food and protection, men neither gain nor suffer

Amensalism (- 0)

• Association between two organism where on species is inhibited or killed but the order in unaffected
• Species affected is called amensal while the species killing it is called inhibitor through release of chemicals known as allochemics or allelopathic substabces

Examples of Amensalism

• Penicillin releases penicillin antibiotics to inhibit bacterial growth
• Streptomyces griseus secret chemicals inhibit bacterial growth

Parasitism (- +)

• Close association between organisms in which one (parasite) lives in or on the host at its expense
• The parasite benefits while the host is harmed

Examples of Parasitism

• Humans and tapeworm: tapeworm parasite lives in the small intestine benefits from protection and habitat while man loses nutrients it absorbs
• Mistletoe and flowering plant: mistletoe is a plant parasite living on flowering plants raised to receive sunlight
  • It absorbs water and minerals while the lost host endures

Predation (- +)

• Association where a predator kills the prey to feed.
• Usually, the predator is larger, stronger and the completely eliminates prey

Examples of Predation

• Hawk predator; the hawk catches preys and it completely eliminates it
• Lion and coat: The lion catches kills the goat with it being smaller in size