IB Biology Unit 1

1.1 Introduction to Cells

Cell Theory: All living organisms are made of one or more cells Cells are the smallest units of life Cells come from pre-existing cells Living organisms are able to respond to the environment, obtain nutrition, respire. metabolize, excrete waste products, grow and reproduce.   Metabolism Response Growth Reproduction Excretion Nutrition Homeostasis

Atypical cells that challenge the Cell Theory Striated muscle cell A tissue made of repeated units called sacromeres Challenge idea that cells have one nucleus per cell, each cell is multinucleated Giant algae (Acetabularia) A cell of gigantic size, 0.5 to 10 cm in length Have a small root-like structure called a rhizoid Challenge idea that cells are simple in structure and in small size Aseptate fungal hyphae Long threads with many nuclei Have no dividing cell walls called septa Possess a shared, continuous cytoplasm

Calculating Magnification 1000 nanometres = 1 micrometre  1000 micrometers = 1 millimetre