科學：小學教師指南/食物鏈

食物鏈（食物網）是指生物之間的一種等級序列，每個生物都依賴於下一個生物作為食物來源。它是指生態系統中生物進食的順序。食物鏈是生態系統中食物能量從一個生物體傳遞到另一個生物體的路徑。

能量是完成工作或引起變化所需的。食物鏈中所有能量的來源都是太陽。
太陽 - 我們太陽系的中心恆星，為地球提供熱量和光線。

你知道嗎？食物鏈最早由 9 世紀的阿拉伯裔非洲科學家和哲學家阿爾-賈希茲提出，後來在查爾斯·埃爾頓 1927 年出版的一本書中廣為人知，該書還介紹了食物網的概念。

食物鏈長度

食物鏈的長度是一個連續變數，它提供了能量傳遞的度量和生態結構的指標，其值隨著從最低營養級到最高營養級線性連線的增加而增加。食物鏈經常用於生態建模（例如三物種食物鏈）。它們是對真實食物網的簡化抽象，但在其動態和數學意義上很複雜。生態學家已經制定並檢驗了關於與食物鏈長度相關的生態模式性質的假設，例如隨著生態系統規模的增加而增加的長度、每個連續水平能量的減少，或者長食物鏈長度不穩定的命題。食物鏈研究在生態毒理學研究中起著重要作用，追蹤環境汙染物的途徑和生物放大作用。

生產者

also known as autotrophs, is an organism that uses sunlight to make its own food for energy. They make up the first level of every food chain. Autotrophs are usually plants or one-celled organisms. Nearly all autotrophs use a process called photosynthesis to create “food” (a nutrient called glucose) from sunlight, carbon dioxide, and water.Plants are the most familiar type of autotroph, but there are many other kinds. Algae, whose larger forms are known as seaweed, are autotrophic. Phytoplankton, tiny organisms that live in the ocean, are also autotrophs. Some types of bacteria are autotrophs. For example, bacteria living in active volcanoes use sulfur compounds to produce their own food. This process is called chemosynthesis.

消費者

Are the living organism who will depend on other organism to survive. The second trophic level consists of organisms that eat the producers. These are called primary consumers, or herbivores. Deer, turtles, and many types of birds are herbivores. Secondary consumers eat the herbivores. Tertiary consumers eat the secondary consumers. There may be more levels of consumers before a chain finally reaches its top predator. Top predators, also called apex predators, eat other consumers. Consumers can be carnivores (animals that eat other animals) or omnivores (animals that eat both plants and animals). Omnivores, like humans, consume many types of foods. Humans eat plants, such as vegetables and fruits. We also eat animals and animal products, such as meat, milk, and eggs. We eat fungi, such as mushrooms. We also eat algae, in edible seaweeds like nori (used to wrap sushi rolls) and sea lettuce (used in salads).

分解者

Are the living organism (bacteria) that will break down other living organism. Detritivores and decomposers are the final part of food chains. Detritivores are organisms that eat nonliving plant and animal remains. For example, scavengers such as vultures eat dead animals. Dung beetles eat animal feces. Decomposers like fungi and bacteria complete the food chain. They turn organic wastes, such as decaying plants, into inorganic materials, such as nutrient-rich soil. Decomposers complete the cycle of life, returning nutrients to the soil or oceans for use by autotrophs. This starts a whole new food chain.

食物鏈中能量流動的示例。

太陽給草提供能量
草給老鼠提供能量
老鼠給蛇提供能量
蛇給鷹提供能量
死亡的動物和植物給蚯蚓（分解者）提供能量

生產者 = 植物

消費者 = 老鼠

分解者 = 細菌

例如，草從陽光中獲取自身食物。兔子吃草。狐狸吃兔子。當狐狸死亡時，細菌會分解它的屍體，並將其返回土壤，為草等植物提供養分。

任何特定的物種可能會吃一種食物或多種物種，消費者可能會以相似的生物為食。倉鴞可能會吃老鼠；老鼠可能被麻雀鷹、蛇或任何其他眾多肉食性動物吃掉。

植物是食物鏈中的第一級，被稱為初級生產者。植物和蔬菜透過光合作用過程製造自己的食物和能量。植物透過利用陽光、空氣中的二氧化碳和土壤中的水，並將它們轉化為糖的形式來製造自己的食物。消費者有三個等級，初級消費者是指以植物為食的生物，是食物鏈中的食草動物。次級消費者吃初級消費者。老鼠可能是初級消費者，而貓可能是次級消費者，還有第三級消費者被稱為三級消費者，它們是以次級消費者和初級消費者為食的。狼可能是三級消費者，它吃貓和老鼠。

分解者會分解死物中的營養物質並將它們返回土壤。生產者然後可以利用土壤中的營養物質和元素。分解者完成了系統，將必要的分子返回給生產者。