Explain that Living organisms are composed of cells.
Explain that Living organisms are composed of cells.
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Living organisms are fundamentally composed of cells, which are often referred to as the basic units of life. This concept is a cornerstone of biology and is encapsulated in the cell theory, which states that:
- All living organisms are made up of one or more cells: This includes unicellular organisms, such as bacteria and protozoa, as well as multicellular organisms like plants, animals, and fungi.
- The cell is the basic unit of structure and organization in organisms: Cells provide structure to living organisms and perform essential functions necessary for life. Each cell type has a specific role that contributes to the organism’s overall functioning.
- All cells arise from pre-existing cells: This principle highlights that cells do not spontaneously generate; instead, they divide and reproduce from existing cells, ensuring continuity of life.
Types of Cells
Cells can be broadly categorized into two types:
- Prokaryotic Cells: These are simpler cells without a nucleus or membrane-bound organelles. They are typically smaller and include bacteria and archaea.
- Eukaryotic Cells: These are more complex and contain a nucleus and various organelles (like mitochondria, endoplasmic reticulum, etc.). Eukaryotic cells make up plants, animals, fungi, and protists.
Functions of Cells
Cells perform a variety of functions essential for life, including:
- Metabolism: Cells carry out biochemical reactions that convert nutrients into energy.
- Growth and Reproduction: Cells can grow and divide to form new cells, allowing for growth and reproduction of the organism.
- Response to Stimuli: Cells can respond to environmental changes, which is crucial for survival.
- Homeostasis: Cells help maintain a stable internal environment despite external changes.