Biology: Exploring Life Chapter 1

Life’s Levels of Organization Define the Scope of Biology Emergent properties At what level does life emerge?

Living Organisms Interact with their Environments, Exchanging Matter and Energy Sunlight To be successful, an ecosystem must be able to: Recycle chemicals necessary for life Move energy through the ecosystem Energy enters as light and exits as heat Heat Producers Cycling of Chemical Nutrients Chemical energy Heat Consumers

Living Organisms Interact with their Environments, Exchanging Matter and Energy Life requires interactions between living (biotic) and nonliving (abiotic) components Biotic components Producers: Photosynthetic organisms that provide food for a typical ecosystem Consumers: Eat plants (or animals that profit from plants) Abiotic components Chemical nutrients required for life

Cells are the Structural and Functional Units of Life Two distinct groups of cells exist Prokaryotic cells Simple and small; lack membrane bound organelles Ex’s. Bacteria Eukaryotic cells Have membrane bound organelles Plants, animals, fungi and protists are composed of eukaryotic cells

Prokaryotic cell Eukaryotic cell DNA (no nucleus) Membrane Nucleus Figure 1.3 Contrasting the size and complexity of prokaryotic and eukaryotic cells. This figure indicates that the eukaryotic cell is subdivided into functional compartments (organelles) by membranes. Nucleus (contains DNA) Organelles

Cells are the Structural and Functional Units of Life Form generally fits function By studying a biological structure, you determine what it does and how it works.

The Unity of Life: All forms of life Have Common Features DNA is the genetic (hereditary) material of all cells A gene is a discrete unit of DNA The chemical structure of DNA accounts for its function (replication and transmission to daughter cells) The diversity of life results from the differences in the sequence of chemical bases in DNA

Diversity Results from Differences in DNA Sequence

The Unity of Life: All forms of life Have Common Features Seven Characteristics Shared by All Living Things Order—the complex organization of living things Regulation—an ability to maintain an internal environment consistent with life Growth and development—consistent growth and development controlled by DNA Energy processing—acquiring energy and transforming it to a form useful for the organism

The Unity of Life: All forms of life Have Common Features Response to the environment—an ability to respond to environmental stimuli Reproduction—the ability to perpetuate the species Evolutionary adaptation—acquisition of traits that best suit the organism to its environment

(3) Growth and development (4) Energy processing (1) Order (2) Regulation (3) Growth and development (4) Energy processing Figure 1.4B Some important properties of life. (5) Response to the environment (6) Reproduction (7) Evolutionary adaptation

The Diversity of Life Can be Arranged Into Three Domains Domain Bacteria—prokaryotic, mostly unicellular, microscopic Domain Archaea—prokaryotic, mostly unicellular, microscopic oldest and most extreme Domain Eukarya—eukaryotic cells, uni/multicellular with membrane bound organelles . Teaching Tips 1. An excellent introduction to the domains and kingdoms of life is presented at http://www.ucmp.berkeley.edu/exhibits/historyoflife.php.

Domain Eukarya Includes Four Kingdoms: K. Animalia, K. Plantae, K Domain Eukarya Includes Four Kingdoms: K. Animalia, K. Plantae, K. Fungi, K. Protista K. Protista K. Plantae K. Fungi K. Animalia

EVOLUTION, THE CORE THEME OF BIOLOGY

Evolution Explains the Unity and Diversity of Life In 1859, Charles Darwin published On the Origin of Species by Means of Natural Selection The book accomplished two things Presented evidence to support the idea of evolution Proposed a mechanism for evolution called natural selection

Evolution Explains the Unity and Diversity of Life Natural selection was inferred by connecting two observations Individuals within a population inherit different characteristics and vary from other individuals (A population is varied!!!) A population can produce far more offspring than the environment can support; those individuals that have inherited traits best suited for the environment will survive to produce offspring of their own

Population with varied inherited traits 1 Population with varied inherited traits 2 Elimination of individuals with certain traits Figure 1.6B An example of natural selection in action. 3 Reproduction of survivors

Evolution Explains the Unity and Diversity of Life Natural selection is an editing mechanism It results from exposure of heritable variations to environmental factors that favor some individuals over others Over time this results in evolution of new species adapted to particular environments

Killer whale Pangolin Pangolin Figure 1.6C Examples of adaptations to different environments. Killer whale Pangolin

THE PROCESS OF SCIENCE

Scientists Use Two Main Approaches to Learn About Nature Two approaches are used to understand natural causes for natural phenomena Discovery science—uses verifiable observations and measurements to describe science Hypothesis-based science—uses the data from discovery science to explain science. This requires proposing and testing of hypotheses

Scientists Use Two Main Approaches to Learn About Nature There is a difference between a theory and a hypothesis A hypothesis is a proposed explanation for a set of observations A theory is supported by a large and usually growing body of evidence

With Hypothesis-based science, We Pose and Test Hypotheses We solve everyday problems by using hypotheses An example would be the reasoning we use to answer the question, “Why doesn’t the flashlight work?” Using deductive reasoning we realize that the problem is either the (1) bulb or (2) batteries. The hypothesis must be testable and falsifiable

Test prediction Test prediction Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burned-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Figure 1.8A An example of hypothesis-based science. Test prediction Test prediction

Test falsifies hypothesis Observations Question Hypothesis #1: Dead batteries Hypothesis #2: Burned-out bulb Prediction: Replacing batteries will fix problem Prediction: Replacing bulb will fix problem Figure 1.8A An example of hypothesis-based science. Test prediction Test prediction Test falsifies hypothesis Test does not falsify hypothesis