Summary
Highlights
This lesson introduces biodiversity and stability. The objective is to explain how species diversity increases the probability of adaptation and survival of organisms in changing environments. Building on module 6, which covered evolution and natural selection leading to biodiversity, this module explores how biodiversity influences ecosystem stability.
Biodiversity describes the variety of life forms in different ecosystems. An ecosystem with high biodiversity has numerous species, while one with low biodiversity has fewer. Examples are given: a rainforest has high biodiversity, while a rice field has low biodiversity. A cattle farm and a cornfield also have low biodiversity, contrasting with the high biodiversity found in an ocean.
Biodiversity holds significant economic and ecological value. Organisms are sources of food, medicine, clothing, and shelter. The direct economic value refers to species providing basic human needs, such as food, clothing, shelter, medicine, and energy. An example is the rosy periwinkle plant, a valuable medicine that is also extremely poisonous.
Indirect economic value refers to benefits produced by organisms without direct consumption or use. Examples include trees reducing floods, preventing landslides and soil erosion, and absorbing carbon dioxide. Aesthetic value is derived from the visual or artistic enjoyment provided by species, such as forested landscapes, natural parks, and mountains for spiritual meditation.
Biodiversity is crucial because it sustains the flow of energy in the food web and contributes to environmental stability. Stability is defined as the resilience to withstand changes in the environment. A greater diversity generally leads to greater stability.
This section focuses on population growth. A population is a group of organisms of the same species living in a certain area. Ecologists study why population sizes increase or decrease. Population growth is determined by birth rate (natality) and death rate (mortality). If the birth rate exceeds the death rate, the population grows; if the death rate is higher, the population decreases.
Population density refers to the number of organisms per unit area. Limiting factors prevent populations from growing continuously. Two main types exist: density-independent and density-dependent. Density-independent factors include natural disasters (floods, earthquakes, fires), amount of sunlight, temperature (e.g., global warming effects), and human activities. These factors impact populations regardless of their density.
Carrying capacity is the maximum number of organisms an environment can support. When resources are abundant, populations experience exponential growth, forming a J-shaped curve. However, with limited resources or when approaching carrying capacity, population growth exhibits logistic growth, resulting in an S-shaped curve.
Density-dependent limiting factors include diseases and parasites, which spread faster in crowded areas. Competition for resources also limits growth, favoring organisms with better adaptations. Predation increases when prey are plentiful, leading to increased predator reproduction. Emigration occurs when populations exceed carrying capacity, causing individuals to move to new areas for resources, with immigration being the opposite.
Humans have a responsibility to maintain a clean and healthy ecosystem. The lesson concludes by encouraging learners to complete their module tasks, emphasizing the importance of learning science.