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

1. 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– 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