#12 Levels of Organization in Living Things (English)

LEVELS OF ORGANIZATION IN LIVING THINGS

Hierarchy of structures

Organisms are made from organizations of smaller structures:

 Organelle: a specialized part of a cell that has its own function, e.g. the nucleus or the mitochondrion

Cell: the smallest part of a living structure that can operate as an independent unit e.g. the red blood cells.

Tissue: a group of cells with similar structures, working together to perform a shared function e.g. muscle tissue

Organ: a structure made up of a group of tissues, working together to perform specific functions e.g. the heart

Organ system: a group of organs with related functions, working together to perform body functions e.g. respiratory system

Organism: an individual made of organ systems, which work to keep that organism alive e.g. a cat

Specialized Cells

Cell	Function	Adaptations	Appearance
Root hair cell – found on the outside of plant roots.	To help to anchor the plant in the soil and to absorb water and mineral ions from the soil.	- Thin cell walls - easy for minerals to pass through. - Elongated shape for more surface area.
Xylem cell – found in plants	Transport water and mineral ions from the roots to all the other parts of the plant.  They also support the plant.	- Lots of these arranged end to end, form a long, continuous tube that runs from the root, up the stem and into the leaves of plants (xylem vessel). - No cytoplasm so water passes freely. - Wall contains lignin, a strong, waterproof substance.
Red blood cell	Transport oxygen from the lungs to all the other parts of the body.	- No nucleus - Flexible and small – it can squeeze through the tiniest of blood capillaries, taking oxygen as close as possible to the cell that needs it. - Contains hemoglobin, the oxygen-carrying molecule. - Biconcave shape – large surface area.
Muscle cell – found in many different animal cells.	Contract to get structures closer together.	- Many nuclei - Made up of many strands of protein that slide over each other, making the cell contract.
Ciliated cell – found in animals.	Help to sweep dirty mucus up the bronchi and the trachea towards the back of the throat, where it is swallowed.	- Have tiny hairs called ‘cilia,’ which beat together in a rhythmic way to sweep the mucus, keeping it away from the lungs.