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

• 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

• 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

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

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

• 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

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