What is Science? A way of learning and thinking about the natural world using experimentation to make conclusions Scientists collect information, look for patterns and connections, and propose explanations Science is always changing with new observations, tests, equipment, viewpoints, and discoveries that lead to new theories and revising old ones Important to YOUR life Should the government have your DNA? Does a person begin at conception? Did we evolve?

How Science Works Observation Being with an observation using the senses Gather information from observations called data Data can be quantitative or qualitative Make logical inferences using data Ex- If 100 samples from the lake contain algae, then all the water contains algae

How Science Works Hypothesis After the observation, scientists ask a question about what they noticed This leads to forming a hypothesis or an educated guess for a set of observations “If… then…” statement- If fertilizer is added to a plant, then it will grow faster. Uses prior knowledge, logical inferences, and informed imagination

How Science Works Experiment The hypothesis is tested in a controlled experiment where only 1 variable is tested Control- group in which all conditions are kept the same Variable- all conditions kept the same except for the single condition being tested for Independent Variable (IV)- changed on purpose, manipulated, what “I” do/change Dependent Variable (DV)- changes according to the IV, depends on the IV, what you measure

How Science Works Results Data is measured and recorded from the experiment Charts and tables are created of the data Data is also analyzed to see if hypothesis was correct or not

How Science Works Conclusion The results are explained and the hypothesis is shown as true or false Any errors and limitations in the experiment are discussed If the hypothesis was shown false, it will be tweaked and another experiment will be performed

How Science Works Other Issues Controlled experiments are not always possible in the lab, for ethical reasons or if there is a large sample size Hypothesis – Theory - Law

Experiment Example Observations- plants die in the dark Q- Does the color of light affect plant growth? Hypothesis- If plants are under colored lights, then they will not grow as fast as under white lights Experiment- Set up 5 plants in separate closets with red bulbs and one with white. Measure grow in cm for 10 days. All plants receive same amount of water, soil, etc.

Experiment Example Control- Plant under white light (no “treatment”) IV- plants with colored lights (manipulation, I changed) DV- growth of the plants with colored lights (depends on…. Color) Results- All 5 plants died, and the one with white light grew 4 cm Conclusion- Hypothesis correct…. What does this mean?

Real Example In the 1600s, the main hypothesis for how life starts was that it starts from abiotic matter This was called spontaneous generation or abiogensis In 1668, Francesco Redi proposed that life came from life, called biogenesis Observation- Flied land on meat uncovered and maggots appear

Hypothesis- Flies produce maggots

Real Example In the 1800s, scientists continued to argue over abiogensis In 1864, Louis Pasteur’s experiment finally proved biogensis using broth and S-shaped flasks and observing bacterial growht Bacteria would only grow if the flask was normal and exposed to air Flasks with S-shape would not allow growth

Biology Study of life Organism- any living thing Species- organisms that can produce offspring that can breed

Characteristics of Life Made up of cells -Cells are the smallest unit of life -Organisms can be made of one cell, called unicellular -Organisms can be made of many cells, called multicellular

Characteristics of Life 2. Reproduce- Sexually involves sex cells from two parents fusing to make the first cell of a new organism Asexually involves one parent using itself to create a new organism

Characteristics of Life 3. DNA- living things are made up of the genetic code DNA DNA acts as a blueprint that directs the growth and development of an organism DNA also dictates that organisms will only reproduce their own kind

Characteristics of Life 4. Grow and Develop They go through specific life stages from young to adult to old 5. Energy Energy is obtained in photosynthesis from the sun for plants, and in food for animals 6. Respond Stimulus- a signal to which an organisms responds External- come from the environment Internal- come from within the organism

Characteristics of Life 7. Homeostasis- Living things must maintain a stable internal environment despite changes 8. Evolve/Adapt- As a group living things must be able to adapt over time, or evolve Desert plants have thicker “skin” The greater the diversity within a species, the greater chance of surviving environmental changes

Levels of Organization Biosphere- all of earth’s ecosystems Ecosystem- communities and their abiotic surroundings Community- populations that live together in a defined area Population- group of the same organisms that live in a defined area Organism- one individual living thing

Levels of Organization Organ System- a group of organs working together, like the digestive system Organ- a group of tissues working together, like the heart Tissue- a group of cells working together, like muscle tissue Cell- the smallest functional unit of lie, like a muscle cell Molecules- groups of atoms that form chemicals like water and DNA. NOT alive

Tools Light Microscope Transmission electron microscope Light passes through lenses to magnify a specimen Transmission electron microscope A beam of electrons reveals the inside of a specimen up to 100,000x Scanning electron microscope A beam of electrons scans the outside of specimens up to 10,000x