Introduction to Biology Estimated 5-30 million species Only 2 million have been identified Only a few thousand have been studied Believed that life arose 3.5 billion years ago What is biology? –It’s the study of life, the study of all living things –Biology is extremely varied and diverse –Unified by certain themes

Characteristics of life Characteristics of Life Introduction

4 Big Ideas of Biology Evolution –This is the central dogma (core idea) of biology and explains how species develop adaptations in an ever-changing environment. –Natural Selection is the mechanism by which evolutionary change occurs Energy and Homeostasis –All life is based on atoms and molecules, which in turn are involved in the formation of cells, the basic units of life. –All life is characterized by energy flow and chemical cycling.

Big Ideas Continued Information and Signaling –The key to life’s diversity lies in differing sequences of DNA molecules, and the key to survival lies in maintenance of homeostasis using feedback and other signaling mechanisms. Interactions and Systems –Biological organization starts with atoms and cells, moves to organisms, populations, and communities which form ecosystems. –Biodiversity is influenced by the environment and is impacted by evolution and extinction.

Levels of Organization Molecules-groups of atoms; smallest unit of most chemical compounds Cells- smallest functional unit of life Groups of cells- tissues, organs, and organ systems Organism- Individual living thing Population- Group of organisms of one type that live in the same area Community- Populations that live together in a defined area Ecosystem- Community and its nonliving surroundings Biosphere- The part of Earth that contains all ecosystems