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An unmanned space probe was sent to Mars to check for signs of life on the planet. How could such a probe confirm the existence of life? Unit One: The Nature of Life BIOLOGY It is the study of living things Characteristics of Life Each living thing is called an organism Organisms have the following characteristics: 1) Living things are highly organized and contain many complex chemical substances 2) Living things are made up of one or more cells, which are the smallest units that can be said to be alive Organisms cont’d Living things use energy Living things have a definite form and a limited size Living things have a limited life span Living things grow Organisms cont’d Living things respond to changes in the environment Living things are able to reproduce Groups of living things evolve, or change, over time Non-living objects may show one or a few of these characteristics but never all There are some “borderline” cases: Viruses- can be stored like chemicals in a bottles but when inside living cells, they will reproduce (but they still don’t have all the characteristics of living things) Life Processes Living things carry out many different kinds of processes Nutrition Transport Respiration Synthesis and Assimilation Growth Excretion Regulation Reproduction Many of these life processes are required for maintaining a constant environment within an organism despite its changing external environment The condition of a constant internal environment is known as homeostasis Nutrition All organisms take materials from its external environment and changes it into a more usable form Nutrients are the substances that an organism needs for energy, growth, repair or maintenance Taking in food from the environment is ingestion Digestion is the breakdown of food materials into simpler forms Transport This is the process by which substances enter and leave cells and become distributed within the cells Transport varies between single celled organisms and multi-cellular organisms Ex. Circulatory system in humans Respiration All life processes require a constant supply of energy Respiration deals with energy released within cells This may or may not involve breathing Synthesis and Assimilation Synthesis is when organisms are able to combine simple substances chemically to form more complex substances Synthesis produces materials that can become part of the structure of an organism It also allows the organism to `grow The incorporation of materials into the organism’s body is called assimilation Growth Growth is the process by which living organisms increase in size This is one of the results of the assimilation of nutrients Growth in animals usually follows a pattern and will end Some plants will continuously grow Excretion All organisms produce waste Waste, if accumulated, can be harmful to the body Removal of wastes is excretion Regulation All activities that help to maintain an organism’s homeostasis make up the process of regulation Ex. Digestive system Ex. Nervous system Ex. Excretory system Reproduction This is the process by which living things produce new organisms of their own kind 2 types: Asexual (single individual produces offspring identical to the parent) Sexual (2 parents and offspring are not identical to either parent) Metabolism All the chemical reactions occurring within the cells of an organism are called its metabolism This includes processes that build up complex substances from simpler ones and breaks down complex substances into simpler ones Questions How are humans and crystals, such as those that form on a window, alike in terms of their signs of life? How are they different? Looking at the pictures shown previously, list all the characteristics that prove an organism is living. (rock, plant, mouse, paramecium, dead tree, cockroach, kitten) Questions List 4 ways in which a car is like a living thing. List 4 ways a car is not a living thing. In PAIRS ONLY- create a mnemonic device that will help you remember all 9 life processes Ex. Planets- My Very Eager Mother Just Served Us Nachos