A cell, they are the tiniest living thing on earth.
Answer:
Biofuels are renewable fuels that are produced from biomass, organisms that were formed and stopped living a short time ago. The energy in the biofuels is called bioenergy. The major constituents of biomass are cellulose, lignin, starch and sugar, but many plants also contain other organic compounds that are beneficial for energy recovery from the material due to their physical structure and chemical composition. The difference between biofuels and fossil fuels is that fossil fuels take millions of years for new formation while new biomass for biofuels is constantly being formed. This means that biofuels can usually be considered carbon neutral as the carbon dioxide emitted during combustion is constantly bound to new biomass in a closed cycle.
<span>a. Fish have a single central heart; earthworms have several hearts.
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Multi cellular organisms are made up of billions of cells each specialized to a unique role and these cells are organized into structural and functional units such as tissues and organs.
For each cell and organ to function optimally, it requires oxygen and nutrients and needs carbon dioxide and metabolic waste taken away in a continuous, never ending process.
<span>A mechanism is needed to accomplish the important function of transporting the relevant materials to and from the cell. The circulatory system fits this bill splendidly. It is a specialized organ system which allows blood and lymph to flow through the entire body carrying nutrients such as glucose, amino acids and electrolytes as well as oxygen to each cell, at the same time carting away carbon dioxide and all sorts of metabolic waste over to excretory organs to be expelled from the body.
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<span>Most children acquire a firm sense of gender identity by the age of three</span>
