Lesson Notes By Weeks and Term v3 - Senior Secondary 1
Basic Ecological Concepts
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Basic Ecological Concepts
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Subject: Biology
Class: Senior Secondary 1
Term: 3rd Term
Week: 2
Theme: The Organism And Its Environment
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Name components of anyecosystem. Measure or estimate sizes of some ecosystems. Relate the dynamic nature of an ecosystem to its size. Mention major local (Nigerian)biotic communities. Give names of or ganismstypical of each community. Briefly describe different typesof communities in (a) tropicalregions (b) temperate regions. Name ecological factorscommon to all habitats. Briefly describe each of the factors pointing out 'the ir relativeimportance. Mention the factors whichaffect water-retentivity of soil,types and determine the amountof water each soil type can hold.
Every ecosystem is composed of two main interactive components:
A. Biotic Components (Living Organisms): These are categorized based on their roles in the energy flow within the ecosystem.
Producers (Autotrophs): Organisms that can produce their own food using energy from sunlight (photosynthesis) or chemical reactions (chemosynthesis). They form the base of the food chain.
Examples in Nigeria: Green plants (e.g., maize, cassava, mango trees, oil palms), algae (e.g., in freshwater ponds or the Atlantic Ocean), and some bacteria.
Consumers (Heterotrophs): Organisms that obtain energy by feeding on other organisms.
Primary Consumers (Herbivores): Feed directly on producers.
Examples in Nigeria: Grasshoppers, goats, sheep, cattle (e.g., Fulani herds in the Sahel), antelopes (e.g., in the Guinea Savanna). Secondary Consumers (Carnivores/Omnivores): Feed on primary consumers.
Examples in Nigeria: Lizards, snakes, lions (e.g., in Kainji Lake National Park), domestic cats. Tertiary Consumers (Top Carnivores/Omnivores): Feed on secondary consumers.
Examples in Nigeria: Eagles, leopards, humans (e.g., fishing in the Niger River).
Decomposers (Saprophytes/Detritivores): Organisms that break down dead organic matter (dead plants and animals, waste products) into simpler inorganic substances, returning nutrients to the soil for producers. They are crucial for nutrient cycling.
Examples in Nigeria: Bacteria, fungi (e.g., mushrooms found in rotting wood or soil), earthworms, termites (e.g., common in savannas).
B. Abiotic Components (Non-Living Factors): These are the physical and chemical factors that influence living organisms and the ecosystem.
Climatic Factors: Light, temperature, water (rainfall), humidity, wind.
Edaphic Factors (Soil-related): Soil type, pH, mineral composition, water content, organic matter.
Topographic Factors: Altitude, slope, aspect (direction of exposure).
Chemical Factors: Salinity (e.g., in coastal waters of Lagos), oxygen levels (e.g., in aquatic environments), nutrient availability. Ecosystem sizes vary enormously, from a small puddle to a vast ocean. Measurement techniques depend on the scale and type of ecosystem.
Direct Measurement (Small Ecosystems): For very small, contained ecosystems like a pond or a cultivated plot, direct length, width, and depth measurements can determine volume or area.
Quadrat Method: Used for estimating population density or coverage of sessile (non-moving) organisms (like plants) in a defined area. A square frame (quadrat, e.g., 0.5m x 0.5m or 1m x 1m) is randomly placed in the ecosystem, and organisms within it are counted or estimated. This is extrapolated to the entire area.
Example: Estimating weed cover in a school garden.
Indirect Measurement (Large Ecosystems): Mapping and Geographic Information Systems (GIS): Using satellite imagery, aerial photographs, and digital mapping tools to delineate boundaries and calculate the area of large ecosystems like forests (e.g., Cross River National Park), deserts (e.g., parts of Borno State), or marine zones.
Transect Method: A line is drawn across an ecosystem (e.g., a tape measure). Organisms are sampled at regular intervals along this line, or within a specified distance from the line (belt transect). Useful for observing changes in vegetation or species distribution across an environmental gradient.
Example: Studying vegetation change from a river bank into a drier savanna area.
Estimation based on Known Features: For example, estimating the size of a river ecosystem based on its known length and average width. The boundaries of ecosystems can be defined by prominent physical features (e.g., a lake's edge, a mountain range) or by ecological gradients (e.g., changes in vegetation type). Ecosystems are not static; they are constantly changing and evolving.
This dynamic nature is driven by: Energy Flow and Nutrient Cycling: Energy enters (usually from the sun) and flows through the ecosystem, while nutrients are cycled and reused. These processes are continuous.
Population Fluctuations: Populations of organisms within an ecosystem constantly change due to births, deaths, immigration, emigration, and interactions (predation, competition).
Ecological Succession: The gradual process of change in species composition and community structure over time, leading to a more stable climax community.
Climatic and Environmental Changes: Seasonal variations (e.g., wet and dry seasons in Nigeria), long-term climate change, natural disasters (e.g., floods, droughts, wildfires) can significantly alter ecosystems.
Human Impact: Deforestation, pollution, urbanization, agriculture, and other anthropogenic activities cause significant and often rapid changes to ecosystems.
Relation to Size: Smaller Ecosystems: Tend to be more susceptible to rapid and drastic changes. A small pond, for example, can quickly dry up during a drought or be overwhelmed by a single pollutant source. They often have less biodiversity and are therefore less resilient.
Larger Ecosystems: Generally exhibit greater stability and resilience due to their larger scale, higher biodiversity (more species, more complex food webs), and capacity to absorb disturbances. Changes might occur more slowly or be localized.
However, even large ecosystems can be fundamentally altered by extensive disturbances like climate change or widespread deforestation (e.g., the shrinking Lake Chad basin). Nigeria's diverse geography supports several major biotic communities, primarily categorized by climate and vegetation.
Mangrove Swamps: Characteristics: Found along the coastal areas and in the Niger Delta, characterized by brackish (salt and fresh) water, tidal influences, and specialized salt-tolerant vegetation. The soil is often waterlogged and anaerobic.
Typical Organisms: Red mangrove (Rhizophora spp.), white mangrove (Laguncularia racemosa), black mangrove (Avicennia germinans), mudskippers, crabs, periwinkles, specialized insects, estuarine fish.
Freshwater Swamp Forests: Characteristics: Occur inland from mangrove swamps, along rivers and floodplains in the Niger Delta and other riverine areas. Experience seasonal or permanent flooding with freshwater. High humidity.
Typical Organisms: Raffia palm (Raphia hookeri), Pandanus spp., various aquatic plants, hippopotamuses, crocodiles, manatees, many fish species.
Tropical Rainforest: Characteristics: Found in the South-South, South-East, and parts of the South-West (e.g., Edo, Cross River, Ondo States)*. Characterized by high annual rainfall (>2000mm), consistently high temperatures, dense multi-layered canopy, and extremely high biodiversity. Little seasonal variation in temperature.
Typical Organisms: Tall trees (iroko, mahogany, obeche, oil palm), epiphytes (orchids, ferns), climbers (lianas), chimpanzees, gorillas (rare, Cross River Gorillas), monkeys, snakes, snails, diverse insects, colourful birds.
Derived Savanna: Characteristics: A transitional zone between the tropical rainforest and the Guinea Savanna, often created by human activities like burning and deforestation of former forest areas. It exhibits characteristics of both, with patches of forest within grassland.
Typical Organisms: Mixture of forest remnants and savanna species.
Guinea Savanna: Characteristics: Occupies the largest land area in Nigeria, covering the Middle Belt. Characterized by tall grasses (up to 3m) interspersed with scattered trees (e.g., shea butter tree, baobab). Experiences distinct wet and dry seasons (usually 6-7 months wet).
Typical Organisms: Elephants (rare), roan antelopes, hartebeests, lions (very rare), baboons, monitor lizards, guinea fowl, numerous insects, various grasses (Andropogon, Hyparrhenia).
Sudan Savanna: Characteristics: Lies north of the Guinea Savanna (e.g., Kaduna, Kano, Borno States). Characterized by shorter grasses and more widely scattered, smaller, often thorny trees (e.g., acacia, doum palm). Longer dry season (7-9 months) and lower annual rainfall (500-1000mm).
Typical Organisms: Giraffes (very rare), warthogs, gazelles, various birds of prey, acacia trees, date palm, baobab.
Sahel Savanna: Characteristics: The extreme northern part of Nigeria (e.g., Sokoto, Yobe, Borno States), bordering the Sahara Desert. Very sparse vegetation, very short grasses, thorny shrubs, and isolated trees (e.g., desert date). Very long dry season (>9 months) and low, erratic rainfall (2000mm) and consistently high temperatures (20-35°C) throughout the year, with high humidity.
Characteristic 2: Extremely high biodiversity, with dense, multi-layered evergreen broadleaf vegetation, including tall trees (e.g., iroko, mahogany) and numerous lianas and epiphytes.
Sahel Savanna: Characteristic 1: Very low and erratic annual rainfall (9 months).
Characteristic 2: Sparse vegetation consisting of very short grasses, scattered thorny shrubs, and drought-resistant trees (e.g., date palm, acacia), with overall low biodiversity compared to rainforests.
Commentary: This question tests the ability to recall and differentiate major Nigerian biomes based on key features.
Sustainable Agriculture and Food Security: Understanding soil water retention is vital for farmers in Nigeria, especially in regions prone to drought (e.g., Northern Nigeria). Knowledge of soil types helps farmers choose suitable crops, implement irrigation strategies, and use organic fertilizers to improve soil structure and water retention, thereby increasing food production and ensuring food security. This directly impacts the economy and livelihoods of many Nigerians.
Environmental Conservation and Management: Knowledge of Nigerian biotic communities (e.g., tropical rainforests, mangrove swamps) highlights the country's rich biodiversity. This understanding is critical for conservation efforts (e.g., establishment of national parks like Gashaka Gumti, Cross River National Park) and managing threats like deforestation, pollution (e.g., oil spills in the Niger Delta), and desertification (e.g., in the Sahel region). It informs sustainable resource utilization, protecting natural habitats for future generations.
Urban Planning and Development: Ecological concepts are crucial for informed urban planning. When new cities or infrastructure projects are developed (e.g., new housing estates in Abuja or Lagos), understanding the existing ecosystems, their components, and their dynamic nature helps minimize negative environmental impacts. This includes assessing the impact on local flora and fauna, managing waste, and ensuring adequate green spaces, contributing to healthier and more sustainable communities.