Chapter 1 An Introduction to Life on Earth What are the characteristics of living things? How do scientists categorize the diversity of life? What is the science of biology? Evolution: The unifying theory of biology

Characteristics of Living Things Living things have a complex, organized structure made up of organic (carbon based) molecules

Characteristics of Living Things Element % of Earth’s Crust % of Human Body Carbon 0.19 9.5 Hydrogen 0.22 63.0 Oxygen 47.0 25.5 Silicon 28.0 <0.01

Characteristics of Living Things The cell is the basic unit of life

Characteristics of Living Things

Characteristics of Living Things Living things respond to stimuli from their internal and external environment A stimulus is a change that brings about a response

Characteristics of Living Things Living things maintain their complex structure and internal environment in a process called homeostasis

Characteristics of Living Things This occurrence is known as physiological homeostasis and it is essentially a corrective mechanism. Consider the following scenario in a person: The level of glucose in the bloodstream drops   The person requires glucose in cells to meet the demand for ATP   The body detects this with a particular receptor designed for this function   These receptors release hormones, chemical messages that initiate the start of the feedback mechanism   The hormones travel to their target tissue and initiate a corrective response   In this case, the corrective response is the secretion of more glucose into the bloodstream

Characteristics of Living Things Living things acquire and use materials and energy from their environment in a process called metabolism Catabolism <-> Anabolism Cellular Respiration <-> Photosynthesis C6H12O6 + 6O2 + 6H2O <-> 12H2O + 6 CO2

Characteristics of Living Things Living things grow Materials acquired from the environment are converted into the specific molecules of the organism’s body

Characteristics of Living Things Continuity of life occurs because organisms reproduce offspring of the same type (species) Diversity of life occurs because offspring are slightly different from their parents due to sexual reproduction and mutation

Characteristics of Living Things Living things reproduce themselves using a molecular blueprint called deoxyribonucleic acid (DNA)

Characteristics of Living Things Living things, as a whole, have the capacity to evolve The theory of evolution states that modern organisms arose, with modification, from preexisting life forms

Diversity of Life

Diversity of Life

Diversity of Life

Diversity of Life (Student Completion) Domain Kingdom Cell Type Cell Number Mode of Nutrition Bacteria Archaea Eukarya Protista Fungi Plantae Animalia

Scientific Method The scientific method is the experimental testing of a hypothesis formulated after the systematic, objective collection of data.

Scientific Method The scientific method is often divided into steps. This is helpful for putting the method into context, but keep in mind that the key element of the scientific method is testing the hypothesis. In other words, can you prove that you are wrong?

Steps of the Scientific Method Observe the situation Ask a question Turn that question into a testable hypothesis Predict the outcome of your experiment Perform your experiment Analyze the results Evaluate your hypothesis

Evolution Evolution is the unifying theory that explains the origin of diverse forms of life as a result of changes in their genetic makeup. Modern organisms descended, with modification, from preexisting life-forms.

Evolution Darwin and Wallace formulated a theory of evolution in the 1800’s based on three natural processes: Genetic variation within a population Inheritance of variation by offspring of parents who carry the variation Natural selection: the survival and enhanced reproduction of organisms with favourable variations

Evolution Darwin's finches. The finches numbered 1-7 are ground finches. They seek their food on the ground or in low shrubs. Those numbered 8-13 are tree finches. They live primarily on insects. Since Darwin's time, these birds have provided a case study of how a single species reaching the Galapagos from Central or South America could - over a few million years - give rise to the 13 species that live there today.

Evolution Structures or behaviours that aid survival and reproduction in a particular environment are called adaptations