Characteristics of Life Unit 1

What do living things do? #1: Made of one or more cells  Unicellular: organisms consisting of a single cell  Multicellular: organisms made up of many cells

What do living things do? #2: Display organization Each structure in an organism has a specific function (job)

What do living things do? #3: Grow and develop All organisms start off as one cell!

What do living things do? #4: Reproduce Species = a group of organisms that can mate and produce fertile offspring All living things pass on their DNA to offspring.

What do living things do? #5: Respond to stimuli Stimulus = anything that is part of either an organism’s external or internal environment that causes a reaction Response = organism’s reaction to stimulus. Does not have to be movement! atch?v=dTljaIVseTc tch?v=F3Oj2er-91s

What do living things do? #6: Require energy Autotrophs = capture energy from the sun to produce their own food. Heterotrophs = obtain energy from consuming other organisms.

What do living things do? #7: Maintains homeostasis Homeostasis = regulation of internal conditions to maintain balance or normal conditions Ex – sweat to maintain cool temperature. Then feel thirsty and drink water to replace fluids.

What do living things do? #8: Adaptations evolve over time Adaptation = a characteristic that helps an organism survive in its environment

Do all living things need oxygen?  Not all living things require oxygen!  Many anaerobic organisms can survive without oxygen  These are mostly bacteria and parasites  Ex) clostridium botulinum, which causes the disease botulism and is used for BOTOX In 2010, scientists discovered the first multicellular organisms that don’t use any oxygen – tiny animals that live deep underwater

Scientific Method and Experiments Unit 1

Scientific Knowledge There are two types of scientific knowledge:  A theory is an accepted explanation of something in nature that has been supported by many observations and experiments.  A theory is subject to change as new evidence arises.  A law is a description of something that happens in nature. It DOES NOT explain why.  Laws are generally accepted to be true and universal.  A theory can NOT turn into a law.

Scientific Knowledge  Scientific knowledge is based on evidence from nature, through observations and inferences.  Observation = a direct collection of information  Recording information from the five senses  Objective = based on facts, measurable  Inference = using observations and prior knowledge to draw conclusions  Subjective = can change based on different interpretations or points of view

Observations vs. Inferences Monkey Death Wish!  Write down your observations about what’s going on during the video.  BPw&noredirect=1 BPw&noredirect=1

Scientific Knowledge  The best scientific knowledge is gained through experimentation.  The scientific method is a set of steps that allow scientists to gather information and answer questions as objectively as possible.

Scientific Method Step #1: Ask Questions  Questions must be able to be solved through experimentation  Scientists base their questions on: 1. Observations 2. Prior knowledge 3. Related research

Scientific Method Step #2: Do background research  Scientists research their topic to see what has already been done

Scientific Method Step #3: Form a Hypothesis  Hypothesis = a possible explanation to the research question that can be tested by experimentation  Ex) Using larger amounts fertilizer will increase plant growth

Step #4: Design an Experiment  Experiment = an investigation in a controlled setting to test a hypothesis  Let’s look at an experiment:  A farmer wants to maximize the growth of his corn plants. He thinks that iron might help corn grow taller.  Hypothesis: If the farmer adds iron to his corn crop, then the corn will grow taller. ?

Step #4: Design an Experiment  Control Group = a baseline group used for comparison that receives normal, neutral, or no treatment.  How do we know if the iron has an effect? The farmer will grow a control group of corn plants with NO IRON.  Experimental Group = the group(s) exposed to the variable that is being tested.  The group of corn plants that DOES receive iron. ? ?

Step #4: Design an Experiment  Variable = any factor that changes in an experiment.  Independent Variable (IV)= the variable that is changed by the experimenter on purpose. “I change” the IV. Ex) Iron added to the corn  Dependent Variable (DV)= the variable that is measured (changes in response to the IV) Ex) height of the corn ? ?

Step #4: Design an Experiment  Constants: factors that are kept the same between all trials.  Anything that could affect the experiment should be held constant. What should be kept constant in the farmer’s corn experiment?

Step #4: Design an Experiment  Error occurs when something affects the results by mistake. Ex) some corn plots receive more water than others  To minimize experimental error, scientists should:  Have as many trials as possible  Only change ONE variable in an experiment  Keep as many factors constant as possible  Invalid Data: any data that is an outlier or doesn’t fit the pattern of the rest is likely not accurate ?

Step #5: Collect Data  Data = Information gained from observations  Quantitative Data: numerical data (quantities – time, temperature, length, mass, area, etc.)  Qualitative Data: descriptions of what our senses detect (qualities – NOT numbers) Ex) height of corn plant – quantitative or qualitative? Ex) color of rabbit’s fur –quantitative or qualitative? Quantitative data is always better for an experiment.

Data Collection Tools  Scientific tools include microscopes, computers, graphing calculators, and probeware.  Probeware measures data in real time Ex) Sensors for temperature, pH and dissolved oxygen

Step #6: Analyze the Data  Questions that scientists ask:  “Has my hypothesis been supported?”  “Is more data needed?  “Are different procedures needed?” Tables and graphs are good tools for data analysis The IV is on the bottom (X axis) and the DV is on the left (Y axis)

What if the hypothesis isn’t supported?  An experiment always provides valuable data  Even if the hypothesis isn’t supported, the scientists have learned something new and can design a new experiment.

Step #7: Report Conclusions  Scientific research must undergo peer review to publish research in scientific journals (the most current and reliable sources of scientific information)  Peer review = the process where published experiments are evaluated by others. This is important to make sure experiments are objective and unbiased.