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Introduction to Biology
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The World of Biology
Chapter 1.2

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Biology – The Study of Life
• • • • Life arose more than 3.5 billion years ago First organisms (living things) were single celled Only life on Earth for millions of years Organisms changed over time (evolved)

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• New organisms arose from older kinds • Today there are millions of species • They inhabit almost every region of Earth today

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Themes of Biology
• Cell structure and function • Stability and homeostasis • Reproduction and inheritance • Evolution • Interdependence of organisms • Matter, energy, and organization 5

Cell Structure and Function
• Cell basic unit of life • All organisms are made of and develop from cells • Some composed of only a single cell (unicellular) which is usually identical to parent

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Cells
• Most organisms are composed of many cells (multicellular) – Cells are different (undergo differentiation) • Cells are small • Cells are highly organized

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• Cells contain specialized structures (organelles) that carry out the cell’s life processes • Many different kinds of cells exist • All cells surrounded by a plasma membrane • Contain a set of instructions called DNA (genetic information) 8

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Stability and Homeostasis
• Organisms must Maintain very stable internal conditions - HOMEOSTASIS • Temperature, water content, chemical content, etc. must be maintained

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Reproduction and Inheritance
• All organisms produce new organisms like themselves REPRODUCE • Organisms transmit hereditary information to their offspring INHERITANCE

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DNA
• Genetic Information in all cells • Deoxyribonucleic Acid • DNA contains instructions for traits GENES • Make the structures and complex chemicals necessary for life

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Reproduction
• All species have the ability to reproduce – Not essential to survival of individual but is essential for continuation of a species

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Sexual Reproduction
• Hereditary information from two different organisms of the same species are combined

• Egg and sperm à zygote (fertilized egg)
• Zygote contains hereditary information from both parents

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Asexual Reproduction
• Hereditary information from one, usually unicellular, organism that divides ( binary fission) • Resulting cells contain identical hereditary information • Genetic information from single parent

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Growth
• Grow occurs as the result of cell division and cell enlargement • Cell division is the formation of two cells from a preexisting cell • New cells enlarge as they mature • When a cell grows to a size where its surface area isn’t big enough for its volume, Copyright Cmassengale volume the cell divides 15

Development
• The process by which an adult organism arise is called development – Repeated cell divisions and cell differentiation

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Matter, Energy and Organization
• Living things are highly organized • Require a constant supply of energy to maintain their orderly state

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• In multicellular organisms, cells and groups of cells (tissues) are organized by their function – Cells à tissues – Tissues à organs – Organs à systems – Systems à – ORGANISM 18

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Energy Use
• Use energy in a process called metabolism – Sum of all chemical processes • Require energy to maintain their molecular and cellular organization, grow and reproduce

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Energy
• ALL energy comes from the SUN (directly or indirectly) • Photosynthesis is the process by which some organisms capture the energy from the sun (solar) and transform it into energy (chemical) that can be used by living things

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Autotrophs
• Organisms that make their own food are called autotrophs • Phototrophs – use solar energy (photosynthesis) to get energy • Convert H2O and CO2 into...
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