Characteristics of Life Exam on Thursday What Science is and is not Thinking like a scientist Science as a Way of Knowing Science and Human Values Designing An Experiment Publishing and Repeating Investigations When Experiments Are Not Possible How A theory Develops Studying Life Tools and Procedures Analyzing Biological Data Microscopes Laboratory Techniques

Characteristics of Life

Living things are made up of units called cells Living things reproduce Living things are based on a universal genetic code Living things grow and develop Living things obtain and use materials for energy Living things respond to their environment Living things maintain a stable environment Taken as a group, living things change over time

Characteristics of Life Living things are made up of units called cells (multicellular or unicellular organisms) –Cells are the smallest unit capable of sustaining life –Cell Theory All things are made up of cells All cells come from cells All cells contain a plasma membrane All cells contain DNA

Characteristics of Life Living things reproduce –Living things produce their own kind –Living reproduce by two mechanisms Sexual Reproduction –The offspring is not identical to its two parents Asexual Reproduction –The offspring is identical (clone) to its one parent

Characteristics of Life Living things are based on a universal genetic code DNA (deoxyribonucleic acid) –Nucleotide (A, G, T, and C) –Sugar group –Phosphate group 3’ end Sugar-phosphate backbone Base pair (joined by hydrogen bonding) Old strands Nucleotide about to be added to a new strand A 3’ end 5’ end New strands 3’ end 5’ end

Characteristics of Life Living things grow and develop –Growth Increase in size Replacement of dead cells –Development Differentiation – formation of specialized cells (maturation)

Characteristics of Life Living things obtain and use materials for energy –All living things need energy to survive, grow reproduce and develop –Metabolism – the total of “breaking down” reactions (catabolic) and “building up” reactions (anabolic) that occur in a cell Energy Sources –Photosynthesis –Ingesting other animals and insects (Cellular Respiration) –Decomposed organisms (Cellular Respiration)

Characteristics of Life Living things respond to their environment –Stimulus - a signal to which an organism responds External Stimulus – light, temperature Internal Stimulus – glucose level

Characteristics of Life Living things maintain a stable environment by keeping internal conditions fairly constant this process is called homeostasis –Positive feedback mechanisms Output of stimulus is increased –Blood clotting –Labor contractions –Negative feedback mechanisms Output of stimulus is decreased –Heart rate –Blood pressure

Characteristics of Life Taken as a group, living things change over time (evolution) –Populations change over time in response to their environment –Those traits that are best suited for a certain environment will be dominant in a population

The Hierarchy of Structural Organization

Atoms – group of organisms of one type that live in the same area Molecules - consists of two or more atoms Organelles – are made up of many molecules Cells – are made up of organelles (some) and molecules Tissues – specialized cells are in a tissue

The Hierarchy of Structural Organization Organs – two or more tissues make up an organ Organ Systems – two or more organs make up an organ system Organism – an individual living thing that may be composed of many organ systems (complex multicellular organisms)

The Hierarchy of Structural Organization Population – group of organisms of one type that live in the same area Community - populations that live together in a defined area Ecosystem – community and its nonliving surroundings Biosphere – the part of the earth that contains all ecosystems (any area on the earth that can sustain life)