1 A View of Life

2 The Human Genome Project mapped the complete set of human genes Genomics analyses the DNA sequence of an organism While genomics will lead to breakthroughs in science, it also raises ethical concerns –Safeguarding the privacy of genetic information, for example

3 Living organisms composed of cells –Unicellular organisms Single cell –Multicellular organisms Many cells organized to form tissues, organs, and organ systems

4 Cells –Plasma membrane regulates passage of materials –Specialized molecules (usually DNA) contain genetic instructions –Internal structures called organelles perform specific functions

5 Types of cells –Prokaryotic cells, exclusive to bacteria and microscopic organisms –Eukaryotic cells contain a variety of organelles, including a nucleus, which houses DNA

6 Biological Growth –Increase in the size of cells, the number of cells, or both Development –Includes all the changes that take place during an organism’s life –Structures and body form are adapted to an organism’s functions

7 Metabolic processes –Chemical reactions and energy transformations –Essential to nutrition, growth and repair of cells, and conversion of energy –Regulation of metabolic processes maintains homeostasis

8 Stimuli –Physical or chemical changes in the internal or external environment –The organism responds to, for example, changes in Light Temperature, pressure, or sound The chemical composition of soil

9 Locomotion –Simpler organisms Amoeboid movement The beating of cilia or flagella –Animals Move by contracting muscles Some are sessile and have cilia or flagella –Plants respond to light, water, etc.

10 Asexual and Sexual Reproduction

11 Adaptation –Populations evolve to better survive –Adaptations Characteristics that enhance an organism’s ability to survive in a particular environment May be structural, physiological, behavioral, or a combination

12 Biological Organization Hierarchy

13 The cell –Consists of atoms and molecules –Is the basic unit of life –In multicellular organisms, associates to form tissues

14 Tissues –In animals, an example is muscle –In plants, an example is epidermis Tissues are organized into organs Tissues and organs form organ systems

15 Population –Members of a species that live in the same area at the same time Community –Populations that live together and interact Ecosystem –A community and the environment

16 To carry on life processes, an organism must have –Precise instructions –Communication among cells This information is coded and delivered by –Chemical substances –Electric impulses

17 DNA is the large molecule that makes up genes Genes specify instructions for making every living organism Watson and Crick worked out structure of DNA in 1953

18 DNA consists of two chains of atoms twisted into a helix

19 DNA contains “recipe” for proteins Proteins determine structure and function of cells and tissues

20 In multi-cellular organisms, communication with and among cells is critical Some proteins are important in this communication Cell-to-cell communication is a complex process called cell signaling

21 Information transmitted from one part of the body to another is important in regulating life processes Information is transmitted by –Hormones –Neurotransmitters and their receptors

22 Evolution is the unifying concept of biology Biology –Hierarchical classification scheme –Identifies the approximately 1.7 million species of living organisms

23 Systematics studies the diversity of organisms and their evolutionary relationships –Taxonomy is the science of naming and classifying organisms

24 Binomial system of nomenclature –Developed in the 18th century by Linnaeus, a Swedish botanist –Names and classifies organisms –Basic unit is a species –Each species assigned a two-part name –Genus species

25 Binomial system of nomenclature uses a series of taxonomic categories from species to domain Domain, Kingdom, Phylum, Class, Order, Family, Genus, species

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27 Each category is more general and more inclusive than the one below it

28 Natural selection –Theory of evolution developed by Darwin and Wallace –The Origin of Species by Natural Selection published in 1859 –Sometimes called “survival of the fittest”

29 Natural selection based on four observations –Members of a species show variation –Organisms produce many more offspring than will survive –Organisms compete –Only some survive to reproduce

30 Egg masses of the wood frog— Many more produced than can survive

31 Variation among individuals –Result of different varieties of genes that code each characteristic –Ultimate source of variation is random mutation Chemical or physical changes in DNA that can be inherited Modifies genes

32 Every cell of an organism requires nutrients Certain nutrients are used as fuel for cellular respiration Virtually all cells carry on cellular respiration

33 A self-sufficient ecosystem contains three types of organisms –Producers –Consumers –Decomposers

34 Ecosystems depend on continuous input of energy Organisms can neither create energy nor use it with complete efficiency During every energy transaction, some is lost to the environment as heat

35 Energy Flow in an ecosystem

36 The scientific method involves systematic thought –Deductive reasoning draws conclusions from premises –Inductive reasoning begins with observations and draws conclusions or extrapolates

37 The scientific method involves ordered steps: –Observation –Hypothesis –Experimentation (data) –Conclusion

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