Invitation to Biology

Organization Within An Organism

Atoms are organized into molecules

In multicelled species, cells are organized into tissues, organs, and organ systems

All organisms consist of one or more cells

Organization of Groups of Organisms

Population • All individuals of one species in a specific area

Community • All populations in a specific area

Ecosystem • A community interacting with its environment

Organization of Life on Earth

Biosphere • All regions of Earth that hold life• Land, water, and atmosphere

Levels of Organization

Levels of Organization

Overview of Life’s Unity

Organisms require energy and materials to sustain their organization and activities• Nutrients are required for growth and survival• Producers make their own food• Consumers eat other organisms

Ecosystem: Energy Flow and Material Cycling

Overview of Life’s Unity

Organisms sense change• Receptors respond to stimulation• Responses keep internal conditions within ranges

that cells can tolerate (homeostasis)

Overview of Life’s Unity

Organisms grow and reproduce• Based on information encoded in DNA• Inheritance transmits DNA from parents to

offspring through reproduction mechanisms• Development transforms first cell into an adult

KEY CONCEPTS:LIFE’S UNDERLYING UNITY

All organisms are alike in key respects:• Consist of one or more cells• Live through inputs of energy and raw materials • Sense and respond to changes in their external

and internal environments • Cells contain DNA (molecule that offspring inherit

from parents; encodes information necessary for growth, survival, and reproduction)

So Much Unity, So Many Species

The world of life, past and present, shows great diversity

Classification systems organize species in ever more inclusive groups

Genus and Species

Species: One kind of organism

Each species has a two-part name • First part: Genus name • Combined with the second part, it designates one

particular species

Domains

Current classification groups all species into three domains • Bacteria (single-celled prokaryotes)• Archaea (single-celled prokaryotes)• Eukarya (protists, plants, fungi, and animals)

Bacteria and ArchaeaBacteria

Archaea

Eukarya

Eukarya

Eukarya

Eukarya

An Evolutionary View of Diversity

Life’s diversity arises from mutations • Changes in molecules of DNA which offspring

inherit from their parents

In natural populations, mutations introduce variation in heritable traits among individuals

Variation in Heritable Traits

Some trait forms are more adaptive than others• Bearers are more likely to survive and reproduce

Over generations, adaptive forms of traits tend to become more common in a population• Less adaptive forms of the same traits become

less common or are lost

Evolution

Populations evolve • Traits that help characterize a population (and a

species) can change over generations

Evolution • Change which occurs in a line of descent

Selection

Natural selection• In natural populations• Differential survival and reproduction among

individuals that vary in one or more heritable traits

Artificial selection• Breeding of captive populations• Traits selected are not necessarily adaptive

Artificial and Natural Selection

Critical Thinking and Science

Critical thinking is a self-directed act of judging the quality of information as one learns

Science is a way of looking at the natural world• Helps minimize bias in judgments• Focuses on testable ideas about observable

aspects of nature

How Science Works

Researchers generally• Observe something in nature • Form hypotheses (testable assumptions) about it• Make predictions about what might occur if the

hypothesis is not wrong • Test their predictions by observations,

experiments, or both

Experiments

Tests used to support or falsify a prediction• Variable characteristic is measured and changed• In the control group, variables do not change

A Scientific Approach

HypothesisOlestra® causes intestinal cramps.

PredictionPeople who eat potato chips made with Olestra will be morelikely to get intestinal cramps than those who eat potato chipsmade without Olestra.

Experiment Control Group Experimental Group

Percentages are about equal. People who eat potato chipsmade with Olestra are just as likely to get intestinal crampsas those who eat potato chips made without Olestra.These results do not support the hypothesis.

Conclusion

Eats regularpotato chips

Eats Olestrapotato chips

93 of 529 peopleget cramps later(17.6%)

89 of 563 peopleget cramps later(15.8%)

Results