Geologic time scale Boundaries for major intervals determined by transitions in the fossil record

What is plate tectonics? Movements of Earth’s tectonic plates rafted land masses to new positions Movements had profound impacts on the directions of life’s evolution Evidence for plate tectonics theory – Distribution of global land masses – Global fossil distribution – Magnetic rocks – Seafloor spreading from mid-oceanic ridges

When did humans evolved? Approximately 20 million years ago central and east Africa was densely forested. Climatic changes resulting from plate tectonic movements and episodes of global cooling about 15 million years ago caused a replacement of the forest by a drier-adapted savanna mixed with open areas of forest. During the course of hominid evolution, periodic climate changes would trigger bursts of evolution and/or extincion.

What is population? Population – A group of individuals of the same species Population growth is affected by demographics – Population size – Population density – Population distribution – Age structure

What is speciation? Formation of daughter species from a population, routes vary in their details and duration. Population can interbreed Evolutionary process Results in diversity!

What is the pattern in life history? Each species has a life history pattern – When an individual starts reproducing – How often it reproduces – Number of offspring each time, and other traits Life histories have a genetic basis and are subject to natural selection

What is today’s human population? surpassed 6.6 billion – Geographic expansion, agriculture, medical and technological innovations are major factors – Today’s range of biodiversity is the result of historical mass extinctions and slow recoveries

What is the structure of a community? Habitat – The type of place where a species usually lives – Characterized by physical and chemical features, and other species living in it Community – All populations of all species in a habitat Species diversity – Number and relative abundance of species in a habitat