The organisation of living things
The characteristics of living things What do living things have in common? What makes them different from non-living things? Vital functions All living things perform (realizan) the vital functions: Nutrition: transform food into nutrients and energy. Some living things make their own food (like plants) and some others eat other living things (consumers). Sensitivity or intereaction (relación): the perception of changes that occur in the environment and inside the body. Reproduction: allows (permiten) living things to produce offspring (crías) like themselves (idénticos).
B. The size (tamaño) of living things Living things that you can see by the naked eye (a simple vista) are called macroscopic beings. Those living things which are so small that you need a microscope to observe them are called microscopic beings or micro-organisms. 2. The cell A cell is the smallest (la más pequeña) unit of life. It is a living things because it performs the three vital functions. All living things are made of cells.
Animal and plant cells: The cell membrane is the outer part (parte de fuera) and is involved (involucrada) in the function of sensitivity. Cytoplasm is a viscous (viscoso) liquid inside the cell. The organelles (orgánulos) perform (realizan) some functions. The nucleus contains the material necessary to reproduce the cell and to direct (dirigir) the activities of the cell. The nucleus is separated from the cytoplasm by a membrane. Plant cells also (también) contain: Chloroplasts: green organelles that contain chlorophyll. The cell wall is a rigid structure that surrounds (rodea) the cell membrane.
B. Organisation of cells: Living organisms can be unicellular (their single –única – cell performs –lleva a cabo – all the functions needed) or pluricelullar (living things are composed of two or more cells coordinated to perform the vital functions). In pluricellular beings, the cells are different because they are specialized. The cells of the same type are grouped (agrupadas) together to form a tissue (tejido). For example: - Muscle cells are elongated (alargadas). Tissues shrink (se encogen) and strech (se alargan) and this allows muscles to move. - Epithelial cells are flat (planas). They form the skin (piel). They insulate the body and protect it. - Nerve cells are star-shaped (forma de estrella) with long extensions or “arms”. These cells establish connections and then transmit information to all parts of the body.
In multicellular, cells are grouped to form different levels of organisation: - The first level of organisation are the cells. - Several cells which perform the same function group to form a tissue. - Several tissues which perform the same function group to form an organ (for example, the stomach). - Several organs that perform a function jointly (conjuntamente) form a system (for example, the digestive system). All these levels of organisation result in an organism (organismo).