Ch 1: Biology in the 21st Century Pt. 1 

1. The Study of Life

Earth is home to an incredible diversity of life

• Different types of life live almost everywhere on earth.

The Biosphere

• Biosphere: All living things and all the places they are found on earth.
  • Includes the environment, atmosphere, and organisms found in the area.
  • All parts of the biosphere are connected.

Biodiversity

• Biodiversity: The variety of life across the biosphere.
  • Greater biodiversity is found near the equator because more living things can live in warmer climates than in cold climates.
• Species: A type of living thing that can reproduce by breeding among themselves.
  • 2 million out of the estimated 10 million species on earth have been identified.
  • Every year, biologists discover 10,000 new species

All Organisms share certain characteristics

• Biology: The scientific study of all forms of life.
• Organism: Any individual living thing.
• Cells: The basic unit of life.
  • All organisms are made up of one or more cells.
• Living things use chemical energy to survive.
  • Chemical energy is received through absorbing sunlight or eating other organisms.
• Metabolism: All of the chemical processes that build up or break down materials.
  • Metabolism in organisms needs energy.
• All organisms need to react to their environment to survive.
  • Physical reactions called stimuli include light, temperature, and touch.
• Organisms pass down genetic material when they reproduce.
• DNA: The genetic material found in all organisms.
  • Full name is deoxyribonucleic acid.
• Single-celled organisms reproduce by dividing into two.
• Multicellular organisms reproduce from two parents.
• Organisms develop according to instructions carried by DNA and RNA.

2. Unifying Themes of Biology

All levels of life have systems of related parts

• System: An organized group of related parts that form a whole.
  • The whole system’s characteristics come from the interaction of the different parts.
  • Two organisms that interact with each other can be a system.
• Ecosystem: A physical environment with different species that interact with other species and nonliving things.
• Different biologists study different systems.

Structure and function are related in biology

• Structure correlates with function
  • Parts of a cell have structured in certain ways to have different uses.
  • Different types of cells themselves are structured to fit certain purposes.
  • Parts of living things are structured to work in a way that is most beneficial.

Organisms must maintain homeostasis to survive in diverse environments

• Homeostasis: The maintenance of constant internal conditions in an organism.
  • Important for cell function to have regulated conditions.
• Homeostasis is usually maintained with Negative feedback
• Negative feedback causes a response that should return the system to its original state when a change in a system occurs.
  • For instance, when it’s cold, a response humans have is to shiver, which is a technique to warm the body.

Evolution explains the unity and diversity of life

• Evolution: The change of genetic material in living things over time.
  • Long-term response to an environment.

Adaptation

• Evolution can occur through natural selection and adaptation.

• Natural Selection is when organisms with a certain genetic trait survive and reproduce better than organisms without the trait.

• Adaptation: An inherited trait that gives an advantage to organisms with that trait.

  • Adaptations occur through MANY generations as traits are passed down.

• One species might branch into two when the different traits become more common in the species’ population.

Unity and Diversity

• Shared traits in organisms are a result of common evolutionary descent.
• Natural selection can lead to the evolution of new species.

3. Scientific Thinking and Processes

Like all science, biology is a process of inquiry

• Science is a human process of trying to understand the world around us.
• Scientific Inquiry is based on curiosity and skepticism, and also requires evidence.
  • Skepticism uses critical thinking to analyze results.

Observations, Data, and Hypotheses

• Observation: using senses and tools to study the world
• Observation is important for categorizing and studying organisms.
• Data: Information that is collected through observation.
  • The two general types of data are qualitative data and quantitative data.
• Qualitative data is used to report what happens with sights, sounds, and smells.
• Quantitative data can be measured or counted to report how something happens.
• Hypothesis: A proposed answer for a scientific question.
  • Scientists use observations and data to form hypotheses.

Testing Hypotheses

• If the hypothesis is valid, predictions can be made of what will happen in a situation.
• A hypothesis can either be nonsignificant or statistically significant after seeing if the data supports the hypothesis.
  • A nonsignificant outcome would mean the data shows little or no effect.
  • A statistically significant outcome would mean the data shows an effect that isn’t just a chance.
• When data does not support a hypothesis, the hypothesis is rejected.
• Peer Review is when results are evaluated by other scientists.

Biologists use experiments to test hypotheses.

• Experiments: a process where scientists study factors (independent and dependent variables) to find cause-and-effect relationships.
• Independent variable: A factor that is changed in an experiment.
• Dependent variable: A factor that changes based on the independent variable.
  • This is what is measured and observed during an experiment to see the impacts of the independent variable.
• Constants: The conditions in the experiment that don’t change
  • Scientists use a control group/condition to study the independent variable.
  • A control group or control condition doesn’t change.

A theory explains a wide range of observations

• Theory: a proposed explanation for observations and results supported by evidence.
  • Theories can never be truly proved and can change over time through new evidence.