- Slides: 10
EVOLUTION An Introduction
Evolution l l l Evolution = a change over time In biology, it is the series of facts, observations, and hypotheses about the history of life. Evolution is the unifying principle of biology. It explains how living things are related, from the smallest cells to the largest animals.
It Began With Charles Darwin l l l In 1831, the HMS Beagle set sail from Britain on a five year cruise Charles Darwin was the ship’s naturalist While on the voyage, Darwin studied the plants and animals he saw, collecting samples
The Voyage of the HMS Beagle
Living Diversity l Darwin was overwhelmed by the living diversity he saw (variety of plants of animals) l Scientists estimate that there as many as 31 million different species on Earth – only 1. 75 million have been identified
Living Diversity l l l Today, we call it biodiversity Biodiversity is defined as the variety of living organisms, the genetic information they contain, and the biological communities in which they live There are three levels of biodiversity: ecosystem diversity, species diversity, and genetic diversity
What is an ecosystem? l l l Ecosystems are communities of organisms and their environments. Ecosystem diversity includes the variety of habitats, living communities, and ecological processes in the living world. There are so many ecosystems because there is so much life.
What is a species? l A species is a group of similar looking organisms that can successfully reproduce fertile offspring. l Each species has its own gene pool, which is the set of genes that are shared by all members of the species.
Species Diversity l l l Species diversity is the variety of species that exist on Earth. In an ecosystem, each species (plants, animals, unicellular organisms) are important for the health and survival of the whole ecosystem. The more species that live in an ecosystem, the better for that ecosystem.
Genetic Diversity l l l In general - refers to the sum total of all the different forms of genetic information carried by all organisms living on Earth today Within a species – refers to the total variety of alleles in the gene pool Individuals within the same species may share the same genes, but they can still look and act very different.