Characteristics of Living Things

Key Ideas 5.2a – Homeostasis in an organism is constantly threatened. Failure to respond effectively can result in disease or death.

Biology Biology – Study of living things More than 1 million different kinds of living things All living things are similar in many ways Organism = Living thing

Signs of Life A living organism will show all of the following Signs of Life: Highly organized and contain many complex chemical substances Made up of one or many cells, which are the smallest unit that can be said to be alive Living things use energy Have definite form and limited size Limited life span

Signs of Life A living organism will show all of the following Signs of Life: Living things grow Respond to changes in the environment Able to reproduce Evolve or change, over long periods of time. This is a characteristic of groups of organisms, not of individuals

Non-Living Things Non-living things may show one or a few of the Signs of Life, but they never show all of them

Life Processes

Life Processes Life processes are necessary for maintaining a fairly constant environment within an organism, in spite of the constantly changing external environment All living things must maintain homeostasis Homeostasis – The condition of a stable (balanced) internal environment in an organism Dynamic Equilibrium – The body stays balanced by taking action whenever the balance is disturbed Metabolism – all chemical reactions occurring within the cells of an organism Regulation – all of the activities that help maintain an organism’s homeostasis

Life Processes To maintain homeostasis, organisms carry out the same basic life functions: Regulation Transport Nutrition Excretion Respiration Growth Synthesis Reproduction

Transport Transport – process by which substances enter and leave cells and become distributed within the cell Transport involves both  Absorption – process by which end products of digestion and other dissolved substances are taken into the cells and fluids of the organism Circulation – distribution of materials within an organism Usable materials enter the cells directly from the environment Waste materials leave the cell and into the environment Multicellular animals use a circulatory system

Multicellular plants use structures to transport substances from roots to the leave

Multicellular animals use a circulatory system

Transport Diffusion – movement of molecules from high concentration to low concentration. It requires no energy (passive transport). Active Transport – requires the use of energy, usually moving molecules from a low concentration to high concentration (against the flow of diffusion) Osmosis – diffusion of water into or out of the cell. If water diffuses into the cell, the cell swells (gets larger) and may burst. If it loses water (being put in salt water for example) it will shrivel up.

Nutrition Nutrition – when organisms take materials from its external environment and changes them into forms it can use Nutrients – substances that an organism needs for energy, growth, repair or maintenance Types of Nutrition: Producers (Autotrophs) – make their own food Consumers (heterotrophs) – cannot make their own nutrients so they obtain ready made nutrients by eating other organisms

Nutrition Photosynthesis is carried out by plants, algae and blue- green bacteria (autotrophs). It takes the radiant energy of the sun and puts it in the bonds of sugar molecules Photosynthesis formula: 6 CO2 + 6 H2O  C6H12O6 + 6 O2 Photosynthesis occurs in the chloroplast of plant cells Photosynthesis only stores energy in food (glucose). We need respiration to get the energy out of the food. Ingestion – taking in of food from the environment Digestion – breakdown of complex food materials into simpler forms that an organism can use

Nutrition Plants have stomates (holes) in their leaves that let them exchange the gasses used in photosynthesis Guard cells open and close the stomates to keep the plant from dehydrating Guard cells only protect plants from water lose Xylem and phloem carry food and water through a plant

Excretion Excretion – removal of the waste from the organism’s body Organisms produce wastes substances that cannot use and that may be harmful if accumulated in the body Waste are products of many chemical reactions that occur in cells

Respiration Respiration – process that takes energy from sugar molecules and places it in molecules of ATP ATP is the energy source of all living things Organisms obtain their energy by releasing the chemical energy stored in nutrients Aerobic Respiration – breakdown of sugar into carbon dioxide and water that requires oxygen and yields more ATP for a molecule of glucose Anaerobic Respiration – breakdown of sugar into carbon dioxide and water without oxygen and yields less ATP for a molecule of glucose

Respiration When humans are forced to get energy from anaerobic respiration, we produce lactic acid that damages muscles (the burn you feel during exercise) Photosynthesis and aerobic respiration are opposite reactions!

Growth Growth – process by which living organisms increase by size Cellular Specialization – process that involves different cells becoming specialized for different functions Organisms can repair and replace worn-out parts

Synthesis Synthesis – ability to combine simple substance chemically to form more complex substances Assimilation – incorporation of materials into the organism's body

Reproduction Reproduction – process by which living things produce new organisms of their own kind Types of Reproduction: Asexual – single individual produces an identical offspring Sexual – two parents and the offspring is not identical to either parent

Metabolism Metabolism – all chemical reactions occurring within the cells of an organism Build complex substances from simpler ones and processes that break down complex substances into simpler ones Releases and uses energy