Chapter 2: The Science of Chapter 2: The Science of BiologyBiology

1. Investigate and understand the natural world

2. Explain events in the natural world

3. Use those explanations to make useful predictions.

State the Problem

Form a Hypothesis

Set Up a Controlled Experiment

Record Results

Analyze Results

Draw a Conclusion

Publish Results

• A hypothesis should be tested by an experiment in which only one variable, the independent variableindependent variable, is changed at a time.

• The result that you measure is called the dependent variabledependent variable

• All other variables, the controlscontrols oror controlled variablescontrolled variables, should be kept unchanged, or controlled.

Controlled Variables:jars, type of meat,location, temperature,time

Manipulated Variables:gauze covering thatkeeps flies away from meat

Section 1-2

In 1668, Francisco Redi proposes an experiment to prove that maggots do not arise from meat “out of nowhere.”

Identify the following components of Redi’s experiment:

•Dependent variable

•Independent variable

•Controlled variables

According to the diagram, what should Redi conclude?

• A hypothesis is a prediction, or educated guess about why or how something occurs in nature.

• A theory is when a particular hypothesis is supported by many scientists after rigorous testing.

• Biology: The study of life or living and once-living things.

• Living things share 8 characteristics.

• No single characteristic sufficiently describes a living thing.

Characteristics of Living ThingsCharacteristics of Living Things

Characteristic DescriptionMade of cells Many microorganisms such as bacteria are unicellular;

Plants and animals are multicellular

Reproduce Maple trees reproduce sexually; Hydra reproduce asexually through budding

Based on a universal genetic code (DNA)

Flies produce flies, dogs produce dogs, seeds from maple trees produce maple trees

Obtain and use materials and energy

Plants obtain their energy from the sun; Animals obtain their energy from the food they eat

Grow and develop Flies begin life as eggs, then become maggots, then become adult flies.

Respond to their environment

Leaves and stems of plants grow towards light

Maintain homeostasis Despite changes in the temperature of the environment, a robin maintains a constant body temperature.

As a group, change over time (evolution)

Plants that live in the desert survive because they have become adapted to the conditions of the desert.

What are cells?What are cells?• Cells – collection of

living matter enclosed by a barrier that separates the cell from its surroundings.

• Organisms consisting of only one cell are unicellular (bacteria)

• Organisms consisting of more than one cell are multicellular (dogs, trees, humans)

2 Types of Reproduction2 Types of ReproductionSexual reproduction: requires two cells from different individuals unite to produce the first cell of a NEW organism.

Asexual reproduction: a single organism can reproduce without the aid of another.

Growth and DevelopmentGrowth and Development• Most living things go through a

cycle of change called development.

• A single cell that starts an organism’s life divides and changes again and again to form the many and varied cells of an adult organism.

• As this process continues, organisms experience a process called aging in which the organism becomes progressively less efficient and eventually dies.

Obtaining and Using Obtaining and Using EnergyEnergy• All organisms require

energy to build the substances that make up their cells.

• Metabolism: the total sum of all chemical reactions in the body.

• Anabolism: process in a living thing that involves putting together or synthesizing, complex substances from simpler ones (Example?)

• Catabolism: process in a living thing that involves the breakdown of complex substances into simpler ones (Example?)

Anabolism

Catabolism

Catabolism

Responding to Their Environment

• Stimulus - anything in the environment that causes an organism to react. (Examples?)

• Irritability – the ability of living things to respond to stimuli. (Plant leaves, stems & roots)

• Homeostasis – an organism’s ability to maintain constant or stable conditions that are necessary for life. . . Examples?