Introduction to Biology Chapter 1

Characteristics of Life Cells: Cell theory: all living things are made of cells, cells are the basic unit of structure and function, cells come from pre-existing cells Cellular structures: plasma membrane, cytoplasm, DNA Prokaryotes: no internal membrane-bound organelles Eukaryotes: internal membrane-bound organelles, including a nucleus Unicellular versus multicellular: generalists versus specialists

Characteristics of Life… Growth Increase in size Increase in number of cells Or both Development Increase in complexity Changes in function

Characteristics of Life… Internal regulation Metabolism – chemical reactions and energy transformations Example: Homeostasis – maintenance of internal balance

Characteristics of Life… Response to stimuli Changes – physical or chemical; internal or external… sensory information Examples: Responses – reactions can be physical or chemical

Characteristics of Life… Reproduction Asexual – simple organisms Advantages: Disadvantages: Sexual – complex organisms

Characteristics of Life… Evolution On the population scale Means to change over time Become more ‘suited’ to the environment… more adapted Examples:

Organism organization Atom (one kind of thing) … molecules (different atoms) … macromolecules (different functional groups) … organelles (one function) … cells (all functions of life) … tissues (one type of cell) … organs (several tissue types; one function) … organ systems (several organ types; one function) … organism (all the organ systems must work together)

Ecological organization Individual organism (species) … population (all members of one species in one place at one time) … community (all the populations in an area) … ecosystem (the community and nonliving parts of an area) … biosphere (all places on Earth where life can exist)