Introduction to Biology
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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
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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
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Science as a way of knowing
– Use observations, questions, and experiments to explain the natural world
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Interdependence in Nature
– All organisms are linked together and with their environment
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Matter and Energy
– Matter and energy is transferred from organism to organism
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Cellular basis of life
– Cells grow, respond to their surroundings and reproduce
– Multicellular and unicellular
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Information and heredity
– DNA is different in every organism
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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
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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
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Structure and function
– All organisms use some kind of structure that has evolved in ways that make
particular function possible
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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
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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