IB Biology Review with Complete Solutions

IB Biology Review with Complete Solutions cell theory -All living things are composed of cells -cells come from preexisting cells -Cells are smallest unit of life Challenges to cell theory: muscle fibres -They are fused cells, so they're long and have multiple nucleus -challenges cells are autonomous units Challenges to cell theory: Giant algae -certain species may grow large -challenges idea cells are microscopic and larger organisms are composed of many Challenges to cell theory: aseptate fungal hyphae -filamentous hyphae that are not partitioned will have continues cytoplasm -Challenges idea living structures are composed of discrete cells Functions of life Metabolism: living things undertake essential chemical reactions Reproduction: Living things produce offspring Sensitivity: living things are responsive to stimuli Homeostasis: living things maintain a stable internal environment Excretion: living things require the removal of waste products Nutrition: living things exchange materials with their environment Growth: living things can move and change shape or size Acronym: MR SHENG Metabolic functions of paramecium and chlorella Paramecium: Heterotrophic for nutrition, engulfs food and absorbs gases through absorption, and solids are removed through anal pore, liquids through vacuole Chlorella: autotrophic, contains chlorophyll for photosynthesis, all essential materials are both absorbed and eliminated through passive absorption Importance of surface size and volume Volume: Rate of metabolism Surface area: rate of exchange between cell and environment As cell grows, volume increases faster than SA Cells therefore can't get too big or the cell will burn more nutrients than it is taking in--cell growth limited Adaptations cells can make to maximize SA:Vol -Cells may adopt elongated or flattened shapes -Cells may possess cellular extensions (ex: root hairs) or fold to plasma membrane -cells may reduce volume by including larger central vacuoles, as plant cells do Why is an intestine cell shaped like it is? Has microvilli to increase SA (allows for more material absorption) advantages and disadvantages of light and electron microscopes Light: Can view living specimens and natural colors, but lower magnification and lower resolutions Electron: higher magnification and resolution, but can only view dead specimen and view is monochrome--false color Differences between transmission electron micrograph and a scanning electron micrograph Transmission electron microscopy (TEM) generate