Top 100 Biology Facts to Know for the Year

Top 100 Biology Facts You Need to Know for the Year!

A controlled experiment should have only 2 variables: the independent (which you change from one experimental group to another) and the dependent – or responding variable (which changes due to the other). For example, if you study how the amount of salt in a person’s diet affects their blood pressure, then the amount of salt is the independent variable and the blood pressure level is the dependent variable.
In nearly all experiments it is desirable to have a control group. This group receives no treatment (is under normal conditions) and is used to compare the other experimental groups to it.
A hypothesis is a prediction about the outcome of an experiment.
Line graphs are used to show change over a period of time (ex: the height of a tree over a ten year period of time).
Bar graphs are used to compare one group to another (ex: boys’ heights vs. girls’ heights).
Pie, or circle, graphs are used to look at the proportion or the percentage of a group (ex: the percentage composition of soil – organic matter, mineral matter, clay, etc.)
The X-axis on a graph is on the horizontal axis, and the Y-axis is on the vertical axis.
All good scientists use their senses to make observations.
Inferences are conclusions a person makes based upon their observations and past experiences (ex: if a dark cloud appears it is inferred that it will soon rain).

Chemicals of Life: Biochemistry
Living things are made of 4 basic elements: carbon, hydrogen, oxygen, and nitrogen.
All living things are composed of 4 types of organic molecules: carbohydrates, lipids, proteins, and nucleic acids.

Cell Structure
All living things are composed of cells.
Cells performing the same function are organized into tissues (examples: nerve tissue, epithelial [skin, etc.] tissue, contractile [muscle] tissue, and connective [cartilage, tendons, ligaments, blood] tissue.
Several different types of tissues working together for a common function form organs, and a group of organs working to perform a process is a system.
Prokaryotes are cells without a nucleus and eukaryotes are cells that contain a nucleus.
The nucleus is the control center of the cell and contains DNA.
Cell membranes, made of a double layer of lipids and proteins, surround all cells and are semi-permeable to allow some materials in and keep some materials out.
Cells are filled with cytoplasm, a fluid in which the little cell organs, called organelles, are suspended.
Mitochondria are the organelles in the cell that produce the energy needed to operate.
Ribosomes are the places where proteins are made during translation.
Plant cells have cell walls made of cellulose that support the cell.
Plant cells have vacuoles (which provide a place for storage) and chloroplasts (which are the sites of photosynthesis).

All living things use energy to survive and the source of this energy ultimately comes from the sun.
Plants can use the sun’s energy to produce their own food and are called producers or autotrophs.
Nearly all other organisms must get their food from other organisms and are called consumers or heterotrophs.
During photosynthesis, plants take in carbon dioxide (CO2) through the stomata in their leaves and water (H2O) through their roots to form glucose (C6H12O6) and give off oxygen (O2).
To produce energy, organisms undergo cellular respiration. During this process organisms use glucose which combines with oxygen and produces ATP energy along with water and carbon dioxide as by products.