The Organization of Living Things Chapter 4 Section 3

Key Concept As multicellular organisms develop, their cells differentiate (change & separate) and form levels of organization Why it Matters: so Humans (we are multicellular) can have different kinds of cells, tissues, organs, and organ systems

Unicellular Organisms “uni-” = one Prokaryotes are unicellular organisms Some algae, some protists, and some eukaryotes (yeasts), are unicellular Can still do everything they need to stay alive Benefits over multicellular organisms: Need fewer resources Can live in harsher conditions

Multicellular Organisms “multi-” = more than one Plants, animals, some protists, and most fungi are multicellular Start as a single cell  many cells  cells differentiate (change) into different types of cells  cells group together

Multicellular Characteristics Larger size = have less predators and have more options of things to eat Longer life – organism will continue to live even if a single cell dies Specialization – each type of cell has a specific job, making the organism more efficient

Levels of Organization 1st Level: Cells 2nd Level: Tissues 3rd Level: Organs 4th Level: Organ Systems Cells  Tissues  Organs  Organ Systems

Level 1 : Cells Cells can be specialized (have a certain function) Function = job Function is related to the cell structure Structure = how parts of the cell are put together Shape Material it’s made from Structure of a brain cell is different from muscle cell

Level 2: Tissues Tissue = group of cells that work together to do a specific job Ex: Heart muscle tissue is made of heart muscle cells Animals have 4 types of tissue: nerve, muscle, connective, protective Plants have 3 types of tissue : transport, protective, ground

Level 3: Organs Organ = structure that is made up of 2 or more tissues working together to get a specific job done Ex: Stomach – muscle tissue moves food, special tissues make chemicals to digest food, connective tissue holds stomach together, nervous tissue sends messages back and forth between the stomach and brain

Level 4: Organ Systems Organ system = group of organs working together to perform a specific function Each organ system has a specific job Ex: Digestive system is made of several organs including the stomach and intestines

Structure of Animals Cells -basic unit of an animal’s structure -become specialized _______________________________ Tissues -made of cells that work together to perform a specific function __________________________________________ Organs -made of different types of tissues that work together to perform a specific function ____________________________________________________ Organ Systems -made of organs that work together to perform a specific function _____________________________________________________________ Organisms