International Journal of Marine Science, 2024, Vol.14, No.2, 120-129 http://www.aquapublisher.com/index.php/ijms 123 2 Biodiversity and Ecological Adaptation Strategies 2.1 Changes in species diversity Changes in species diversity have always been a key factor in maintaining ecological balance and ecosystem functions. Over time, countless species have evolved under the influence of natural selection, and environmental changes, human activities and other factors have also led to the extinction of species and the emergence of new species. Species extinction is often caused by the inability of certain key populations in the ecosystem to adapt to rapidly changing environments or excessive human development activities, thus losing the basis for their survival. On the contrary, the emergence of new species is usually the result of natural selection and evolution, reflecting the ability of life to adapt and evolve to environmental changes. However, in modern times, human activities have accelerated the rate of species extinction, and the formation rate of new species has been far unable to keep up, leading to a sharp decline in biodiversity. Reductions in species diversity have profound consequences for ecosystem functioning. Each species plays a specific role in the ecosystem in which it lives, and each layer, from basic producers to apex predators, is critical to maintaining ecological balance. The loss of species means that certain functions in the ecosystem may be weakened or eliminated, such as pollination services, soil formation and nutrient cycling, which are necessary to maintain ecosystem health and human well-being. Therefore, reduced species diversity directly affects ecosystem stability, resilience, and productivity. Genetic diversity is the cornerstone for species to adapt to environmental changes. It is not only related to the survival and reproduction of individual organisms, but also the key to species' response to external stress, disease and environmental changes. Higher genetic diversity means there are more genetic variations in a population, which provides richer "raw materials" for natural selection, thereby enhancing the species' adaptability and evolutionary potential. However, when a species faces extreme environmental pressure or a sharp decline in population, genetic diversity will be affected, reducing the species' ability to adapt to new environmental challenges and further exacerbating the species' extinction risk. 2.2 Adaptation mechanism and evolution In nature, biological populations respond to environmental changes through various adaptive mechanisms and evolutionary processes, including phenotypic plasticity, genetic adaptation, and interaction and co-evolution between species. Phenotypic plasticity is an important mechanism for species to adapt to environmental changes, which allows organisms to exhibit different physiological and behavioral characteristics under different environmental conditions without involving changes in genes. This plasticity allows individuals to respond quickly to environmental changes throughout their lives to survive and thrive in different environments (Fox et al., 2019). Complementing phenotypic plasticity is genetic adaptation, a longer-term process involving genetic variation and natural selection that enables species to adapt to specific environmental conditions during evolution. Mutation is the basis of genetic adaptation and provides the raw material for natural selection. Under new environmental conditions, certain mutations may confer higher survival and reproductive advantages to organisms. These beneficial mutations are subsequently retained through the process of natural selection, thus promoting the adaptation and evolution of species. Over time, these adaptive variations accumulate, potentially leading to the formation of new species. Interactions between species, such as predation, symbiosis, competition, etc., also play a key role in the evolution process. These interactions change as the environment changes, prompting the species involved to coevolve. A plant may evolve more sophisticated defense mechanisms to resist predation by herbivores, and the herbivores may subsequently evolve the ability to overcome these defense mechanisms. This process of co-evolution not only deepens the interdependence between species, but also increases the complexity and stability of the ecosystem.
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