Welcome to the 2015 – 2016 School Year! Mrs. Mollberg

Exploring Life An Invitation To Biology Chapter 1

Overview: Biology’s Most Exciting Era Biology is the scientific study of life Biologists are moving closer to understanding : – How a single cell develops into an organism – How plants convert sunlight to chemical energy – How the human mind works – How living things interact in communities – How life’s diversity evolved from the first microbes

Concept 1.1: Biologists explore life from the microscopic to the global scale The study of life extends from molecules and cells to the entire living planet Biological organization is based on a hierarchy of structural levels

A Hierarchy of Biological Organization 1.Biosphere: all environments on Earth 2.Ecosystem: all living and nonliving things in a particular area 3.Community: all organisms in an ecosystem 4.Population: all individuals of a species in a particular area 5.Organism: an individual living thing

A Hierarchy of Biological Organization (continued) 6.Organ and organ systems: specialized body parts made up of tissues 7.Tissue: a group of similar cells 8.Cell: life’s fundamental unit of structure and function 9.Organelle: a structural component of a cell 10. Molecule: a chemical structure consisting of atoms

Ecosystems The biosphere Organisms Populations Communities Cells Organelles Molecules Tissues Organs and organ systems Cell 1 µm Atoms 10 µm 50 µm

A Closer Look at Ecosystems Each organism interacts with its environment Both organism and environment affect each other The dynamics of an ecosystem include two major processes: – Cycling of nutrients, in which materials acquired by plants eventually return to the soil – The flow of energy from sunlight to producers to consumers – Energy flows through an ecosystem, usually entering as light and exiting as heat

LE 1-4 Sunlight Ecosystem Heat Chemical energy Consumers (including animals) Producers (plants and other photosynthetic organisms)

A Closer Look at Cells The cell is the lowest level of organization that can perform all activities of life The ability of cells to divide is the basis of all reproduction, growth, and repair of multicellular organisms

LE µm

The Cell’s Heritable Information Cells contain DNA, the heritable information that directs the cell’s activities DNA is the substance of genes Genes are the units of inheritance that transmit information from parents to offspring Each DNA molecule is made up of two long chains arranged in a double helix Each link of a chain is one of four kinds of chemical building blocks called nucleotides

LE 1-7 DNA double helixSingle strand of DNA Nucleotide Cell Nucleus DNA

Two Main Forms of Cells Characteristics shared by all cells: – Enclosed by a membrane – Use DNA as genetic information Two main forms of cells: – Eukaryotic: divided into organelles; DNA in nucleus – Prokaryotic: lack organelles; DNA not separate in a nucleus

LE 1-8 Membrane Cytoplasm EUKARYOTIC CELL PROKARYOTIC CELL DNA (no nucleus) Membrane 1 µm Organelles Nucleus (contains DNA)

Concept 1.3: Biologists explore life across its great diversity of species Biologists have named about 1.8 million species Estimates of total species range from 10 million to over 200 million

The Three Domains of Life At the highest level, life is classified into three domains: – Bacteria (prokaryotes) – Archaea (prokaryotes) – Eukarya (eukaryotes) Eukaryotes include protists and the kingdoms Plantae, Fungi, and Animalia

LE 1-15 Bacteria 4 µm 100 µm 0.5 µm Kingdom Plantae Protists Kingdom Animalia Kingdom Fungi Archaea

Unity in the Diversity of Life Underlying life’s diversity is a striking unity, especially at lower levels of organization In eukaryotes, unity is evident in details of cell structure

LE 1-16a Cilia of windpipe cells Cilia of Paramecium 15 µm 5 µm

LE 1-16b Cilia of windpipe cells Cilia of Paramecium Cross section of cilium, as viewed with an electron microscope 0.1 µm

Concept 1.5: Biologists use various forms of inquiry to explore life Inquiry is a search for information and explanation, often focusing on specific questions The process of science blends two main processes of scientific inquiry: – Discovery science: describing nature – Hypothesis-based science: explaining nature

Discovery Science Discovery science describes nature through careful observation and data analysis Examples of discovery science: – understanding cell structure – expanding databases of genomes

Types of Data Data are recorded observations Two types of data: – Quantitative data: numerical measurements – Qualitative data: recorded descriptions

The Role of Hypotheses in Inquiry In science, a hypothesis is a tentative answer to a well- framed question A hypothesis is an explanation on trial, making a prediction that can be tested

LE 1-25a Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb Observations Question

LE 1-25b Hypothesis #1: Dead batteries Hypothesis #2: Burnt-out bulb Test prediction Test falsifies hypothesis Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Test prediction Test does not falsify hypothesis

A Closer Look at Hypotheses in Scientific Inquiry A scientific hypothesis must have two important qualities: – It must be testable – It must be falsifiable

The Myth of the Scientific Method The scientific method is an idealized process of inquiry Very few scientific inquiries adhere rigidly to the “textbook” scientific method

Designing Controlled Experiments Scientists do not control the experimental environment by keeping all variables constant Researchers usually “control” unwanted variables by using control groups to cancel their effects

A Case Study in Scientific Inquiry: The Potato Chip Hypothesis: Olestra causes intestinal cramps Prediction: People who eat potato chips with Olestra will be more likely to get intestinal cramps than those who eat potato chips made without Olestra Experiment: -Control Group: Regular potato chips -Experimental Group: Eats Olestra chips Results: 93 of 529 from control group had cramps, while 89 of 563 from olestra group had cramps Conclusion: What do you think?

Limitations of Science The limitations of science are set by its naturalism – Science seeks natural causes for natural phenomena – Science cannot support or falsify supernatural explanations, which are outside the bounds of science

Theories in Science A scientific theory is much broader than a hypothesis A scientific theory is: – broad in scope – general enough to generate new hypotheses – supported by a large body of evidence – Examples: atomic theory, theory of evolution, theory of gravity – They remain theories Why?

A Law In Science Been observed in every circumstance without fail Laws of thermodynamics – We know how they behave but sometimes not exactly WHY they behave

Model Building in Science Models are representations of ideas, structures, or processes Models may range from lifelike representations to symbolic schematics