1. 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

2. Characteristics of life YouTube - 8 Characteristics of Living Things.mov Living things are made up of cells –Cell is the smallest unit of an organism that is considered to be alive Living things reproduce –All organisms reproduce sexually or asexually. –What’s the difference? –Asexual reproduction When hereditary information from different organisms is not combined A cell splits into two and one cell gives rise to 2 cells Example- bacteria and plants –Sexual reproduction When hereditary information from 2 parts of a single organism or when 2 organisms of the same species is combined Example- humans, dogs, plants

3. Living things are based on a universal genetic code. –All organisms store complex information needed for life, growth and reproduction in a molecule called DNA Living things grow and develop –Start from single fertilized egg, divides again and again-differentiation Living things obtain and use material and energy –Metabolism-organism builds up and breaks down materials through chemical reactions Living things respond to their environment –Stimulus- a signal to which organism detects and responds to

4. Characteristics of Life Living things maintain a stable internal environment –Homeostasis-organisms maintain a relatively stable internal environment Taken as a group, living things evolve –Basic traits passed on from parents don’t change, but over generations, given groups of organisms typically evolve, or change May find 2.5 billion unicellular organisms in a single gram of fertile soil The world of biology is very diverse and rich

5. Themes of Biology Science as a way of knowing –Use observations, questions, and experiments to explain the natural world Interdependence in Nature –All organisms are linked together and with their environment Matter and Energy –Matter and energy is transferred from organism to organism Cellular basis of life –Cells grow, respond to their surroundings and reproduce –Multicellular and unicellular Information and heredity –DNA is different in every organism Unity and diversity of life –All living things are fundamentally alike at molecular level –All composed of common set of carbon-based molecules, all use protein to build structures, and carry out their functions, all store information in common genetic code

6. Evolution –Explains the inherited similarities as well as the diversity of life –Also known as a change in allele frequency in a population over time –Natural Selection is the most important driving force behind evolution -It says organisms with favorable traits are better able to successfully reproduce than organisms that lack these traits Structure and function –All organisms use some kind of structure that has evolved in ways that make particular function possible Homeostasis –All organisms expend energy to keep conditions inside their cells within certain limits –Examples: temperature, water content, food intake –Examples: dogs-pant, seals-fat layer Science, Technology, and Society –Many scientific discoveries raise ethical questions

7. 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