What are the Characteristics of Living Things? Pg. 16 Composed of one or more cells Reproduction Universal Genetic Code Growth & development Energy use and metabolism Response to stimuli Maintenance of homeostasis Capacity for change (adaptation)

Cells Smallest unit capable of all life functions Unicellular Organisms - Entire organism is made up of one single cell Unicellular Organisms - Entire organism is made up of one single cell EX. Bacteria and protists Multicellular Organisms - The organism is made up of many cells Multicellular Organisms - The organism is made up of many cells Cells have specialized functions within the organism Cells have specialized functions within the organism EX. Trees, Humans, Mushrooms

Organization Atom Molecule Organelle Cell Tissue Organ Organ System Multicellular Organism

Reproduction All organisms reproduce in order for their species to continue life Asexual reproduction- involves only a single parent; the offspring would then be genetically identical to its parent Sexual reproduction- involves 2 parents; this produces genetically diverse offspring

Universal Genetic Code Genes carry hereditary information Genes are composed of DNA Determines the inherited traits of every organism on earth Heredity is the reason children resemble their parents

Growth & Development Single Celled Organisms – Grow to larger size Multicellular Organisms – Differentiation for specialized functions

Energy Use & Metabolism Metabolism- the sum of all chemical processes that occur within a living organism in order to maintain life Organisms use energy to carry out every day functions All organisms MUST acquire energy somehow Ex. Plants require Sunlight Humans require food

Organisms react to stimuli: Light Light Temperature Temperature Odor Odor Sound Sound Gravity Gravity Heat Heat Water Water Pressure Pressure An example is a plant’s leaves and stems growing toward light

A stable state of conditions in the body that are necessary for life Body temperature Body temperature Blood volume Blood volume pH balance pH balance Water balance Water balance

Adaptation A process that enables organisms to become better suited to their environment A process that enables organisms to become better suited to their environment Species obtain adaptations through evolution over great periods of time Species obtain adaptations through evolution over great periods of time Evolution- organisms change over time through natural processes that select individuals with the best adaptations

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What is Geologic Time? “Eons” – Largest -“eras” -“periods” -“epochs” Usually the oldest sections are shown on the bottom and the most recent sections are shown on the top

How is Time Divided? Major changes in Earth’s history mark the boundaries between the sections Most sections have been divided because a major organism developed or went extinct.

Precambrian Time

Time from the formation of the Earth (~4.6 billion years ago) to 542 million years ago The Earth was very different then -there was no oxygen or living things The first organisms appeared in the oceans 3.6 billion years ago -They were called Prokaryotes

Prokaryotes Only one cell and no nucleus Cyanobacteria – the first organisms on Earth Through photosynthesis, they released oxygen into the air As oxygen began to build up, the ozone was formed The ozone protects the Earth against the sun’s harmful rays (deadly to land organisms) Because of the ozone, organisms could now live on land too!

Eukaryotes After another 1 billion years, more complex organisms developed called Eukaryotes Many cells with a nucleus Evolved into organisms on Earth today

Paleozoic Era Began 542 million years ago and ended 251 million years ago Divided into 6 periods Many new life forms appeared during the 1 st period, the Cambrian Period = “Cambrian Explosion” For the first time on Earth, organisms had hard parts (shells, exoskeletons) Some organisms that were alive during this period still exist today (ferns and salamanders) but they were giants!

Cambrian Life The fossil record shows evidence of many types of marine life early in the Paleozoic Era. These and other unfamiliar organisms dwelt in the sea during the Cambrian Period, a time when animals with hard parts evolved.

Permian Extinction The largest mass extinction happened 251 million years ago Marked the end of the Paleozoic Era and the start of the Mesozoic Era Scientists are not sure what caused this mass extinction (maybe climate change & volcanoes) 90% of ocean life and 78% of land life died Reptiles and amphibians survived!

Mesozoic Era

Began 251 million years ago Surviving reptiles and amphibians evolved into many other species (like dinosaurs) = “Age of Reptiles”

Cretaceous-Tertiary Extinction Another mass extinction happened 65 million years ago Marked the end of the Mesozoic Era and the beginning of the Cenozoic Era All of the dinosaurs and half of the other animals & plants went extinct Scientists think an asteroid hit Earth, the dust clouds blocked out the sun, plants died, then herbivores, then carnivores.

Cenozoic Era

Began 65 million years ago and continues today Scientists know the most about this Era because the fossils are in the top rock layers and are easier to find Land & climate has changed a lot What big change will happen that will end this era & start the next?

Determining How Old Things Are

Fossil Record When comparing fossils found in rock layers, the deeper the layer, the older the fossil.

Water carries small rock particles to lakes and seas Dead organisms are buried by layers of sediment, which forms new rock. The preserved remains may later be discovered and studied.

Radiocarbon Dating

Method of Radiocarbon Dating

Radiometric Dating: History dinosaurs humans first life origin of Earth en.wikipedia.org/wiki/Image:Eopraptor_sketch5.png © World Health Org. © NASA first complex cells

Geologic Time and Earth History