Summary
Highlights
An ecosystem includes all living things (animals, plants, microorganisms) within a certain area, relying on each other for survival. Organisms require food, water, air, and sometimes a mate for survival. Abiotic (non-living) factors like light, temperature, water levels, pH, wind, and carbon/oxygen levels, along with biotic (living) factors such as food, predators, and pathogens, significantly impact a community. Changes to these factors can have drastic effects, for example, new predators or pathogens can devastate a community, and temperature changes can eliminate food sources.
Animals and plants adapt to their environments for survival. Cacti, for instance, have shallow roots, spines, and water-storing leaves for desert conditions. Snow foxes blend in with white fur, have small ears to conserve heat, and thick coats. Food chains begin with the sun providing energy, which plants convert and are then consumed by other organisms. We (humans) are top consumers, while herbivores like cows eat plants directly. The direction of the arrow in a food chain indicates 'eaten by'.
To study what grows in a field, a quadrat (e.g., a meter square) can be randomly thrown to count plants. The field's size must be estimated to calculate the total plant population. A transect is a more ordered method, involving taking measurements along a line, for example, from a hedge, to observe changes related to light intensity or water distance.
The carbon cycle describes the movement of carbon, present in organic compounds (any compound containing carbon). Carbon exists as carbon dioxide in the air and oceans, as organic compounds in plants and animals (living or dead), and in fossil fuels. Processes like combustion (burning fossil fuels), photosynthesis (plants taking CO2), and respiration (plants and animals releasing CO2) move carbon. Dead organisms and their organic compounds can become fossil fuels or decay, releasing carbon back into the air. This complex, long-term process is vital for ecosystems.
The water cycle begins with the sun warming surface water, causing evaporation. Water vapor rises, cools, and condenses to form clouds. When clouds are heavy, precipitation (rain) occurs. Water can then percolate into mountains (picking up ions and salts), flow into rivers, seep into soil, or run off saturated ground into bodies of water. Plants absorb water for photosynthesis and release it back into the atmosphere through transpiration, restarting the cycle.
Microorganisms are crucial for breaking down organic matter, recycling components back into the system. Decay and decomposition are influenced by temperature, water, and oxygen. Microorganisms have optimal temperature ranges for their enzymes; extreme temperatures (too low or too high) inhibit their activity. They also require a specific amount of water and oxygen for respiration; too much water can lead to oxygen deprivation, and too much oxygen can be toxic.
Humans profoundly impact biodiversity (the variety of plants and animals in habitats). Activities like monoculture (planting a single crop), deforestation for logging or land use, and pollution (air, water, plastic) reduce biodiversity. Pollution can alter water chemistry, introduce harmful chemicals into the food chain, and affect animal respiration and camouflage. Deforestation destroys habitats, leads to soil erosion, and releases nutrients, particularly in vital ecosystems like rainforests.
Peat, essentially compressed decomposed plant matter, forms over millions of years and is a non-renewable resource often harvested for fuel. Its removal destroys valuable habitats. Gases like carbon dioxide, water vapor, and methane contribute to global warming, leading to climate change – not just rising temperatures, but also localized cooling, drier conditions, and increased wind. This affects animal habitats and food sources, such as polar bears losing ice caps for resting, and diseases spreading as temperatures change on mountains. Food security can be compromised if an area becomes too hot or cold for food production.
Food chains can be represented by pyramids of numbers or biomass, illustrating trophic levels. Approximately 10% of energy transfers between trophic levels, with the rest lost as respiration, waste, or movement. Food security means ensuring a stable food supply. Countries relying heavily on imports are vulnerable to external factors like climate, trade agreements, and transport. Increasing domestic food production enhances security. Sustainable practices are crucial, balancing yield increases (e.g., using fertilizer) with environmental impact and considering production methods' land intensity and ecological effects. Sustainable fishing, with proper net sizes, quotas, and methods like line-hauling, prevents overfishing and protects endangered species. Developing new food sources, such as culturing microorganisms, can also contribute to food security.