Invitation to Biology Chapter 1

1.1 Life’s Levels of Organization We understand life by thinking about nature at different levels of organization Nature’s organization begins at the level of atoms, and extends through the biosphere The quality of life emerges at the level of the cell

Making Sense of the World Nature is everything in the universe except what humans have manufactured

A Pattern in Life’s Organization Atoms Fundamental building blocks of all substances Molecules Consisting of two or more atoms Cell The smallest unit of life Organism An individual consisting of one or more cells

A Pattern in Life’s Organization Population Individuals of the same species in the same area Community Populations of all species in the same area Ecosystem A community and its environment Biosphere All regions of the Earth where organisms live

Levels of Organization in Nature

Levels of Organization in Nature

Emergent Properties Each level of organization in nature has emergent properties – a characteristic of a system that does not appear in any of its component parts

1.1 Key Concepts: Levels of Organization We study the world of life at different levels of organization, which extend from atoms and molecules to the biosphere The quality of “life” emerges at the level of cells

1.2 Overview of Life’s Unity All living things have similar characteristics Continual inputs of energy and the cycling of materials maintain life’s complex organization Organisms sense and respond to change DNA inherited from parents is the basis of growth and reproduction in all organisms

Energy and Life’s Organization The capacity to do work Nutrients Atoms or molecules essential in growth and survival that an organism cannot make for itself

Producers and Consumers Acquire energy and raw materials from the environment Make their own food (photosynthesis) Consumers Cannot make their own food Get energy by eating producers and other organisms

Organisms Sense and Respond to Change Organisms sense and respond to change both inside and outside the body by way of receptors Receptor A molecule or cellular structure that responds to a specific form of stimulation

Homeostasis Homeostasis Organisms use receptors to help keep conditions in their internal environment within ranges that their cells can tolerate

Organisms Grow and Reproduce Organisms grow, develop, and reproduce using information in their DNA, a nucleic acid inherited from parents Information encoded in DNA is the source of an individual’s distinct features (traits)

Same Materials, Many Products 20 amino acids are the building blocks used to build a great variety of proteins

1.2 Key Concepts: Life’s Underlying Unity All organisms consist of one or more cells, which stay alive through ongoing inputs of energy and raw materials All sense and respond to change; all inherited DNA, a type of molecule that encodes information necessary for growth, development, and reproduction

1.3 Overview of Life’s Diversity Of an estimated 100 billion kinds of organisms that have ever lived on Earth, as many as 100 million are with us today

Scientific Naming Each type of organism is given a two-part name that includes genus and species names Genus A group of species that share unique features Species Individuals that share one or more heritable traits and can interbreed (if sexually reproducing)

Classification Systems Classification systems group species by their shared, heritable traits All organisms are classified into three domains Bacteria, archaea, and eukaryotes Eukaryotes include plants, animals, protists and fungi

Comparison of Life’s Three Domains

1.3 Key Concepts: Life’s Diversity Many millions of kinds of organisms, or species, have appeared and disappeared over time Each kind is unique in some aspects of its body form or behavior

One-Way Flow of Energy and Cycling of Materials through an Ecosystem

1.4 An Evolutionary View of Diversity A theory of evolution by natural selection is an explanation of life’s diversity

Variation and Mutation Information encoded in DNA is the basis of traits an organism shares with others of its species Mutations are the original source of variation in traits

Adaptation Some forms of traits are more adaptive than others, so their bearers are more likely to survive and reproduce Over generations, adaptive traits tend to become more common in a population; less adaptive forms of traits become less common or are lost

Evolution and Natural Selection Evolution is change in a line of descent Traits that characterize a species can change over generations in evolving populations Natural selection is an evolutionary process Differential survival and reproduction among individuals that vary in the details of their shared, heritable traits

1.4 Key Concepts: Explaining Unity in Diversity Theories of evolution, especially a theory of evolution by natural selection, help explain why life shows both unity and diversity Evolutionary theories guide research in all fields of biology

1.5 Critical Thinking and Science Critical thinking is judging the quality of information Science is limited to that which is observed Helps minimize bias in judgments by focusing on testable ideas about observable aspects of nature

A Guide to Critical Thinking

1.6 How Science Works Scientists make and test potentially falsifiable predictions about how the natural world works

Observations, Hypotheses, and Tests Researchers make observations, form hypotheses (testable assumptions), and make predictions about what might occur if the hypothesis is correct

A Scientific Approach

About the Word “Theory” A hypothesis that is inconsistent with results of scientific tests (evidence) is modified or discarded A scientific theory is a long-standing hypothesis that is used to make useful predictions

Examples of Scientific Theories

Some Terms Used in Experiments Tests that can support or falsify a prediction Variable A single characteristic in a set of individuals that differs from the control group in an experiment

Some Terms Used in Experiments Experimental group Group with a single variable characteristic to be tested against a control group in an experiment Control group Group identical to the control group, except for the variable

1.7 The Power of Experimental Tests Researchers unravel cause and effect in complex natural processes by studying the effects of one variable at a time

Potato Chips and Stomach Aches Researchers tested the prediction that Olestra® in potato chips causes cramps Experimental group: Olestra chips Control group: regular chips

Experiment: Olestra and Stomach Cramps

Butterflies and Birds Why does the peacock butterfly flick its wings when birds are near? Researchers tested two hypotheses Wing spots deter predatory birds Hissing and clicking sounds deter predatory birds

Results: Peacock Butterfly Experiment

Asking Useful Questions Scientists try to design single-variable experiments that yield quantitative results When studying humans, isolating a single variable is not often possible

1.8 Sampling Error in Experiments Researchers experiment on subsets of a group Results may differ from results of the same experiment performed on the whole group Sampling error is a difference between results from a subset and results from the whole Small sample size increases the likelihood of sampling error in experiments

A) Natalie, blindfolded, randomly plucks a jelly bean from a jar A) Natalie, blindfolded, randomly plucks a jelly bean from a jar. There are 120 green and 280 black jelly beans in that jar, so 30 percent of the jelly beans in the jar are green, and 70 percent are black. B) The jar is hidden from Natalie’s view before she removes her blindfold. She sees only one green jelly bean in her hand and assumes that the jar must hold only green jelly beans. C) Blindfolded again, Natalie picks out 50 jelly beans from the jar and ends up with 10 green and 40 black jelly beans. Figure 1.12 Demonstration of sampling error. D) The larger sample leads Natalie to assume that one-fifth of the jar’s jelly beans are green (20 percent) and four-fifths are black (80 percent). The sample more closely approximates the jar’s actual green-to-black ratio of 30 percent to 70 percent. The more times Natalie repeats the sampling, the greater the chance she will come close to knowing the actual ratio. Stepped Art Fig. 1-12, p. 16

Summary of Life’s Characteristics

1.5-1.8 Key Concepts: How We Know Biologists make systematic observations, predictions, and tests in the laboratory and in the field They report their results so others may repeat their work and check their reasoning