8 Characteristics of Life: Biology Key Concepts for Students

Cell

The smallest living unit that can carry out life processes.

Unicellular organisms

Single celled organisms that makeup most organisms on Earth and are self-sufficient.

Multicellular organisms

Organisms in which cells specialize to perform specific functions such as bone cells, skin cells, muscle cells, root cells, and leaf cells.

Photosynthesis

The process by which plants convert the energy from the sun into food, specifically glucose.

Stimulus

A change in the environment that living things respond to, which can be immediate or long-term.

Asexual reproduction

Reproduction involving a single parent that produces identical offspring.

Budding

A form of asexual reproduction seen in organisms like Hydra and Sponge.

Fragmentation

A form of asexual reproduction where an organism can grow from a fragment, as seen in starfish.

Binary Fission

A form of asexual reproduction in unicellular organisms where the cell divides into two identical cells.

Growth

The process of getting bigger, which requires the addition of more cells through cell division.

Development

The process of changing into an adult form or maturing.

Adaptation

The ability of organisms to change to fit their environment over a long period of time, often millions of years.

DNA

A molecule that provides instructions for making proteins and carries genetic material from parent to offspring.

RNA

A molecule that plays a role in the synthesis of proteins from the instructions provided by DNA.

Energy

All living things use energy, primarily sourced from the Sun.

Response to stimulus

Living things respond to stimuli such as shivering when cold or sweating when hot.

Stable internal environment

An organism's ability to maintain a stable internal environment to survive.

Reproduction

The process necessary for a species to survive, which can be sexual or asexual.

Adaptations of organisms

Changes in organisms that allow them to survive in their environment.

Cell division

The process that must occur to increase the number of cells in an organism.

Heredity

The passing of genetic material from parent to offspring.

Biology

The scientific study of life.

Order

An hierarchy of coordinated structures: cells, tissues, organs, organ systems.

Response to Stimuli

Alter growth or behavior based on environmental conditions.

Homeostasis

Stable internal environment inside cells and organisms.

Energy Processing

Gather energy from the environment for metabolic activities.

Growth and Development

Develop in a planned sequence, eventually becoming physically similar to parents.

Evolution

Change in the gene pool of a population over time.

Organization of Life

Biosphere to cells.

Biosphere

Includes all parts of the Earth - surface, atmosphere, and oceans, occupied by life.

Ecosystem

Includes the biological community and surrounding physical environment.

Biological Community

Made of all the populations living and interacting in one area.

Population

Includes all members of a species that live in the same area at the same time.

Organism

An individual life form.

Organ System

Group of organs that work together to perform a task.

Organ

A self-contained structure with a vital function.

Tissue

A group of cells that work together.

Scientific Method

Process of gathering evidence to answer questions about the world.

Hypothesis

A testable explanation or prediction based on the observation and the scientist's prior knowledge.

Independent Variable

New factor that is to be introduced and tested.

Dependent Variable

The measured result that is influenced by the independent variable.

Controlled Variables

Kept constant so they do not influence the dependent variable.

Control Group

Does not receive the independent variable.

Experimental Group

Receives the independent variable.

Data

Includes all of the measurements and observations made during the experiment.

Conclusion

States whether the hypothesis is supported by the experiment.

Peer review

Involves publishing the results for other scientists to review and check for error, bias, or uncontrolled variables.

Margin of error

An estimate of how different a result is from the actual value.

Reduction of margin of error

Can be reduced by increasing the sample size, or number of observations used in an experiment or study.

3% margin of error

Correlates with about a 1000-person sample size.

Experimental Design

The plan for how to conduct an experiment.

Controlled Experiment

Takes place in labs or artificial environments.

Natural Experiment

Takes place in the real-world without manipulation.

Bias

The preference for an experiment to turn out in a certain way.

Blind experiments

Reduce bias by ensuring the test subjects do not know whether they are in the experimental or control group.

Double-blind experiments

Prevent both scientists and subjects from knowing which is the experimental group.

Correlation

Observed when there are statistical variables that have a relationship that cannot be expected by chance alone.

Causation

Occurs when one variable directly influences the other.

Positive correlation

As one variable increases or decreases, the other does the same.

Negative correlation

As one variable increases, the other decreases.

None correlation

There is no observed relationship between the variables.

Pseudoscience

Appears or claims to be scientific, but does not follow scientific practices.

Historical Pseudoscience

Includes theories like spontaneous generation and the Four Elements Theory that lack formal experimental evidence.

Modern Pseudoscience

Includes beliefs such as the anti-vaccination movement and the Flat Earth Society.

Taxonomy

Classification of organisms based on DNA and traits.

Biochemistry

Study of life at the molecular level.

Microbiology

Structure and function of single-celled organisms.

Paleontology

Study of fossils and evolutionary history.

Genetics

Patterns of heredity.