Natural Selction and Adaptation | HUman interactions within natural ecosystems

Adaptation

The ability of an organism to withstand extremes of physical conditions in its environment

Acclimation

A short-term, reversible physiological change in an individual organism in response to environmental conditions; not inherited

Population-level adaptation

Long-term change in a population based on inherited genetic traits that improve survival in specific environments

Evolution

Gradual change in populations over time driven by natural selection acting on inherited variation

Natural selection

The process by which individuals with favourable traits survive, reproduce, and pass on those traits to the next generation

Charles Darwin and Alfred Wallace

Scientists who developed the theory of evolution by natural selection to explain adaptation at population level

HMS Beagle voyage

Darwin’s global expedition during which he made key observations about variation, survival and reproduction

Variation in populations

All populations show differences in appearance and behaviour among individuals

Heritable traits

Characteristics that can be passed from parents to offspring through genes

Environmental traits

Characteristics strongly influenced by environment and weakly inherited

Over-reproduction

The ability of populations to produce more offspring than can survive under limited resources

Population stability

Despite over-reproduction, natural populations tend to remain relatively stable over long periods due to limiting factors

Survival of the fittest

Individuals best adapted to their environment survive and reproduce more successfully

Darwin’s theory of natural selection

Individuals of the same species compete for the same resources; those best adapted survive and reproduce

Competition in natural selection

Occurs because individuals of the same species have identical resource requirements

Effect of competition

Leads to high mortality, displacement, predation, disease and movement into unfavourable environments

Outcome of competition

Only individuals best adapted to obtaining resources survive and reproduce

Natural selection and genetic diversity

Natural selection acts on pre-existing genetic variation in a population

Selective pressure

Environmental or resource-based conditions that favour individuals with advantageous traits

Favourable genes

Genes that increase survival and reproductive success under specific environmental conditions

Inheritance of favourable traits

Surviving individuals pass advantageous genes to offspring, increasing their frequency in the population

Adaptive radiation

Diversification of a common ancestor into multiple species adapted to different ecological niches (e.g. Darwin’s finches)

Adaptation over time

Populations gradually become better suited to their environment as survivors reproduce

Requirement for adaptation

Sufficient survivors must remain to maintain a viable breeding population

Selective elimination

Individuals unable to tolerate environmental conditions are removed from the population

Humans and natural ecosystems

Humans depend on natural ecosystems because they are connected to both biotic (living) and abiotic (non-living) components, meaning ecosystem changes directly affect human survival and well-being

Human dependence on ecosystems

The human economy depends on ecosystem services because natural ecosystems provide essential resources and processes that cannot be fully replaced by human systems

Ecosystem services

Benefits provided by ecosystems that support life and human activities, including regulation of air, water, climate and nutrient cycles

Life-support services of ecosystems

Include air and water purification, biogeochemical cycling, decomposition of wastes, climate regulation, soil fertility maintenance, biodiversity maintenance and pollination; these processes maintain ecosystem balance and support life systems

Importance of ecosystem services

These services support agriculture, pharmaceuticals and industries by maintaining conditions needed for crop growth, resource production and environmental stability

Food resources from ecosystems

Natural ecosystems provide food through forests (wildlife and crops), coral reefs and seagrass beds (fisheries), supporting both subsistence and commercial food supply

Medicinal resources from ecosystems

Ecosystems provide natural compounds used in traditional and modern medicine; loss of biodiversity reduces potential sources of future drugs

Recreation and aesthetic benefits

Ecosystems provide tourism, leisure and aesthetic enjoyment; in the Caribbean this includes beaches, coral reefs and wildlife, which also generate income through tourism

Religious and cultural significance

Natural ecosystems have spiritual, cultural and traditional importance for indigenous and local communities, influencing cultural identity and practices

Revenue generation from ecosystems

Natural ecosystems provide raw materials that support industries such as forestry, fisheries and mining, which contribute to national income and employment

Examples of natural resources used in industries

Timber, non-timber forest products, fisheries and minerals; these resources are harvested and processed to support economic development

Coastal protection by ecosystems

Mangroves, coral reefs, beaches and seagrass beds reduce wave energy, prevent coastal erosion and protect human settlements and infrastructure from storm damage

Importance of coastal ecosystems

Without these ecosystems, coastal areas would experience increased erosion, flooding and higher costs for artificial sea defences

Climate regulation by ecosystems

Forests and aquatic ecosystems absorb carbon dioxide, reducing greenhouse gas concentration and helping to moderate global warming

Role of forests in climate regulation

Trees act as carbon sinks by absorbing CO₂ during photosynthesis and storing carbon in biomass, reducing the enhanced greenhouse effect

Role of aquatic ecosystems in climate regulation

Oceans and aquatic systems absorb large amounts of CO₂, helping buffer atmospheric carbon levels and regulate climate

Genetic resources from ecosystems

Ecosystems provide genetic material used in medicine and agriculture, supporting drug development and improving crop yields and disease resistance

Importance of genetic resources

Genetic diversity allows development of improved crops and medicines, reducing reliance on synthetic alternatives and increasing resilience in agriculture

Importance of ecological integrity

Maintaining ecological integrity ensures ecosystems remain functional, stable and capable of supporting life and human needs over time

Ecological integrity maintains

Maintains species diversity, ecosystem diversity and habitat diversity, which increases resilience against environmental change

Ecological integrity supports

Supports continuous cycling of matter and efficient energy flow through ecosystems, ensuring long-term sustainability

Ecological integrity reduces

Limits competition pressure for scarce resources by maintaining balanced populations and resource availability

Ecological integrity ensures

Maintains ecosystem productivity, allowing ecosystems to continue providing goods and services needed by humans

Link between ecosystem degradation and humans

When ecosystems are damaged, services such as food supply, climate regulation and coastal protection are reduced, directly affecting human health, economy and safety