Living Environment Regent

UNIT ONE: Science of the Living Environment 

A. Terms: 

1. Observation: What is seen or measured. 

2. Inference: A conclusion based on observation or evidence. 

3. Hypothesis: An untested prediction. A good hypothesis states both cause and effect (“If then” statement). 

4. Theory: A broad explanation of natural events that is supported by strong evidence. 

B. Graphing 

C. Controlled Experiment: Compares the results of an experiment between two groups. 

1. Experimental group: Group being tested or receiving treatment. (ex: new drug) 

2. Control group: “Normal” group. Should be identical to experimental group in every way except one: it does not receive the treatment (i.e.: no drug, or given the original drug or a placebo). 

3. Placebo: A sugar pill or other “fake” treatment given to the control group so subjects do not know which group they are in. 

4. Independent Variable: Variable that is being tested (ex: new drug). In a graph the independent variable is always plotted on the X axis. 

5. Dependent Variable: Variable that is measured at the end of an experiment; the results (ex: does patient get better?) The dependent variable is always plotted on the Y axis. 

D. Characteristics of a good experiment. 

1. Can be repeated by anyone and get the same results. 

2. Have large sample size/many test subjects. 

3. Are performed for longer periods of time.

4. Test only one variable. 

5. Are peer reviewed – examined by several scientists to determine its accuracy. 

6. Does not have to agree with the hypothesis. A scientist’s guess is allowed to be incorrect – and usually is. 

7. Is objective – the experiment and conclusion are fair and unbiased. Fact and opinion are not mixed. 

UNIT TWO: Characteristics of Living Things 

A. All living things must maintain homeostasis. 

1. To maintain homeostasis, organisms carry out the same basic life functions: nutrition, excretion, transport, respiration, growth, synthesis, regulation and synthesis. Know these terms! 

2. All life processes make up an organism’s metabolism. 

3. Failure to maintain homeostasis causes disease and death. 

B. Nutrition: 

1. Autotrophs make their own food, while heterotrophs eat other organisms. 

2. Photosynthesis is carried out by plants, alga and blue-green bacteria (autotrophs). It takes the radiant energy of the sun and puts it in the bonds of sugar molecules. Photosynthesis occurs mostly in the chloroplast of plant cells. 

a. Plants have stomata, small holes in their leaves that let them exchange the gasses used in photosynthesis. Guard cells open and close the stomata. 

C. Respiration: Organisms get energy by breaking the bonds of sugar molecules. The released energy is used to make a molecule of ATP, which gives all organisms their energy. 

1. Aerobic respiration requires oxygen, and yields more ATP (energy) for a molecule of sugar than anaerobic (no oxygen) respiration. 

2. When humans are forced to get energy from anaerobic respiration, we produce lactic acid that damages muscles (“the burn” you feel during exercise). 

3. Photosynthesis and Aerobic Respiration are opposite reactions! They are also important in cycling oxygen, carbon, hydrogen and water through the environment. 

D. Transport:

1. Diffusion: movement of molecules from high concentrations to low concentrations. Requires no energy (passive transport). 

2. Active Transport requires the use of energy, usually moving molecules from a low concentration to a high concentration (against the flow of diffusion). 

3. Osmosis is the diffusion of water into or out of the cell. If water diffuses into the cell, the cell swells and may burst. If it loses water (being put in salt water for example) it will shrivel up. 

E. Regulation: coordination and control of other life functions. 

1. A stimulus is a change in the environment that you respond to. 

2. A neuron is a nerve cell. 

3. An impulse is the electrical signal carried by the nerves. Neurotransmitters are chemicals that help carry the impulse. 

4. A hormone is a chemical signal secreted by different glands in the body. Examples of hormones include insulin, adrenaline, testosterone and estrogen 

5. Receptor molecules are proteins on the surface of the cell membrane that receive signals from the nervous and endocrine system. These are needed for your cells to communicate and work together. 

F. Chemistry 

1. The most common elements in living things are (in order) Carbon, Hydrogen, Oxygen and Nitrogen (CHON). 

2. Organic Compounds have Carbon AND Hydrogen (ex: C6H12O6 is organic, H2O, CO2, and NO3 are not). Organic molecules are also larger than inorganic molecules. 

3. Carbohydrates are sugars and starches. All carbohydrates are made from simple sugars (like glucose) and they supply energy. 

4. Lipids store energy and include fats, oils and waxes. They are made from fatty acids and glycerol. 

5. Proteins are made from amino acids. Proteins also make hormones and many body and cell structures, so as far as your body is concerned, proteins are by far the most important of these three organic molecules. 

a. It is the SHAPE of proteins and how they fit together that determines what proteins do. 

b. Four specific jobs of proteins:

1) make enzymes 

2) make receptor molecules on the cell membrane

3) make antibodies 

4) make hormones 

c. Enzymes are catalysts – they affect the rates of chemical reactions. 

1) lock and key model – one type of enzyme fits one type of molecule. Change its shape and the enzyme will no longer work. 

2) very high temperatures cause proteins and enzymes to lose their shape so that they no longer work properly. This is why high fevers are dangerous. 

6. pH: The pH scale measures the strengths of acids and bases. A low pH (0-6.9) is an acid, a high pH (7.1-14) is a base, and 7 is neutral (water). 

G. Cells - Cells are the basic unit of life. All living things (except viruses) are made of cells. 

1. You must know the cell theory (all living things are made of cells). 

2. You must know the differences between plant and animal cells. 

3. You must know the following organelles:
cell membrane, cell wall, nucleus, chloroplast, cytoplasm, ribosome, vacuole, mitochondria 

4. The cell membrane is made of lipids and proteins. It shows selective permeability – that is only some molecules can pass through it (typically small molecules like water and oxygen). Large molecules (like starch or protein) need to be moved by facilitated diffusion or active transport. 

a. NOTE: Students often assume cells have a cell wall OR a cell membrane. ALL cells have a cell membrane, including those with cell walls (plants, fungi, some bacteria and protists). The cell wall is mostly for protection; the cell membrane is needed to control movement into and out of the cell. The animal kingdom is the only kingdom that completely lacks cell walls. 

H. Classification 

1. Organisms are classified mostly by evolutionary history. Those with common ancestors are grouped together. 

2. Kingdoms are large groups of related organisms (fungi, bacteria, protists, animals, plants). 

3. A species is able to successfully reproduce amongst its members.

4. A scientific name is made up of an organism’s Genus and species.