The scientific study of life Dual biology Chapter 1 The scientific study of life

1.1 What is life? Biology is the scientific study of life, but what makes something alive? Scientists have come up with a list of five qualities that, in combination, constitute life: A. Life is organized(from small to large) Atomsmoleculesorganellescellsorganismspopulations communitiesecosystemsbiosphere Organisms are more than just a collection of parts. When they interact they create new complex functions called emergent properties. This is why structure and function are so closely tied.

B. Life requires energy Countless chemical reactions sustain life on a cellular level. These reactions allow organisms to grow, repair and reproduce. The sum of the reactions is called metabolism. Organisms are divided into three broad categories based on energy source and raw materials Producers Consumers decomposers These interact in a complex food web- no system is 100 percent efficient. Energy is always lost as heat. Ecosystems depend on a continuous input of energy(usually the sun)

C. Life maintains internal constancy Living things must sense and react to stimuli. Being able to maintain a state of internal constancy or equilibrium is called homeostasis.

D. Life reproduces itself, and grows and develops Types of reproduction: (how DNA is passed from one generation to the next) Asexual reproduction- DNA comes from one parent Sexual reproduction- DNA comes from two parents- offspring are genetically different from either parent. genetic diversity is healthy for populations and ecosystems

E. Life evolves How are living things so well suited to their environment? Organisms have adaptations- inherited characteristics or behaviors that enable an organism to survive and reproduce successfully.

Adaptive traits come from competition Adaptive traits come from competition. Organisms that are better suited to the environment live to reproduce and pass traits down to offspring. This is called natural selection. Natural selection is the mechanism of evolution. Evolution is the change in genetic makeup of a population over time.

1.2 The Tree of life includes many branches How do scientists organize and classify living things? Taxonomy- study of classification Basic unit of classification is species. Closely related species are grouped into a genus. Scientific names are made up of genus and species together. Ex. Homo sapiens The broadest division is the domain. All living things fit into one of three domains: Bacteria, Archaea, and Eukarya Domains are divided into kingdoms.

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1.3 Scientists study the natural world A. the scientific method has multiple interrelated parts. Scientific method- a general way of using evidence to answer questions and test ideas Parts of the scientific method Observations and questions- Hypothesis- a testable explanation for one or more observations Data collection- Analysis and peer review

b. An experimental design is a careful plan An experiment is an investigation carried out in controlled conditions. Characteristics of a valid experiment: Sample size- larger sample size gives more accurate results Variable- changeable element in an experiment Types- independent variable- what the experimenter controls and changes in the experiment Dependent variable- the response that the investigator measures Standardized variable- anything the investigator holds constant for all subjects in the experiment

Controls Well designed experiments involve a control- this gives a basis for comparison Placebo-in some types of experiments, participants are given an inert substance that resembles the independent variable. Double blind design- in medical experiments neither the researcher or the participants know if they are given the medicine or the placebo. This allows researchers to avoid bias.

Statistical anyalysis Statistical analysis uses mathematical tools to help researchers interpret data.

C. Theories are comprehensive explanations A scientific theory is an explanation for a natural phenomenon. Theories are broad in nature and are widely accepted.

D. Scientific inquiry has limitations Experimental evidence may lead to multiple interpretations Experimental evidence may misinterpreted The scientific community may be slow to accept scientific evidence Scientific inquiry cannot answer questions of morality, ethics or religion.