Community Ecology AP Environmental Science Milton High School

Habitat fragmentation causes significant decline in species diversity Reduce species richness Reduce species richness Reduce amount of functional habitat Reduce amount of functional habitat Cause isolation of a species Cause isolation of a species Possibility of genetic drift or inbreeding Possibility of genetic drift or inbreeding

Edge Effects Associated with Habitat Fragmentation Can Reduce Biodiversity Makes many species vulnerable to stresses such as predators and fires Makes many species vulnerable to stresses such as predators and fires Creates barriers that can prevent some species from colonizing new areas and finding food and mates Creates barriers that can prevent some species from colonizing new areas and finding food and mates

Edge effect

Conservation Biologists Protect Biodiversity Preserving large areas of habitat Preserving large areas of habitat Using migration corridors to link smaller habitat patches Using migration corridors to link smaller habitat patches

Tunnels under roads Bridges over roads

Species diversity Species richness – number of different species Species richness – number of different species Species evenness – abundance of individuals within each of those species Species evenness – abundance of individuals within each of those species

The Most Species-rich Environments Tropical forests Tropical forests Coral reefs Coral reefs Deep sea Deep sea Large tropical lakes Large tropical lakes

Three Major Factors Affect Species Diversity Latitude (distance from equator) Latitude (distance from equator) Depth (aquatic systems) Depth (aquatic systems) Pollution (aquatic systems) Pollution (aquatic systems)

Number of Species Found on an Island Determined by a Balance Between: Rate at which new species immigrate to the island Rate at which new species immigrate to the island The rate at which species become extinct on the island The rate at which species become extinct on the island

Two features of an island which affects its immigration and extinction rate Island’s size Island’s size Island’s distance from the mainland Island’s distance from the mainland

Canary Archipelago What can you predict about how each island was colonized by wild species?

1)The closer the island is to another land mass, the higher the probability of colonization. 2) The older the island, the more likely it will be colonized. 3) The larger the island, the more species are likely to be established. 4) The geographic isolation reduces gene flow between populations. 5) Over time, colonial populations become genetically divergent from their parent population due to natural selection, mutation, and/or genetic drift General principles of island colonization

Explain Robert MacArthur and E.O. Wilson’s Theory of Island Biogeography? How is this theory applied to the management of National Parks? Island Biogeography

Critical Roles of Keystone Species Pollination of flowering plant species Pollination of flowering plant species Dispersion of seeds by fruit-eating animals Dispersion of seeds by fruit-eating animals Habitat modification (Gopher tortoise) Habitat modification (Gopher tortoise) Predation by top carnivores to control populations of various species Predation by top carnivores to control populations of various species Improving the ability of plant species to obtain soil minerals and water Improving the ability of plant species to obtain soil minerals and water Efficient recycling of animal wastes Efficient recycling of animal wastes

The Dodo bird inhabited the island of Mauritius in the Indian Ocean

In 1505, the Portuguese became the 1 st humans to set foot on Mauritius  Dodo bird source of food for the sailors  Dutch used the island as a penal colony and brought pigs and monkeys which ate the eggs of the dodo bird

A combination of human exploitation and introduced species significantly reduced the dodo population The last dodo bird was killed in 1681

Scientists discovered a certain species of tree was becoming quite rare on Mauritius. All of the remaining trees of their species were about 300 years old and no new trees had germinated since the late 1600’s.

Was it coincidence that the tree had stopped reproducing 300 years ago and that the dodo bird had become extinct 300 years ago?

The dodo ate the fruit of the tree and the seed only became active and could grow after passing through the digestive tract of the dodo bird. Scientists discovered the turkey’s digestive tract accomplishes the same task and they are now using turkeys to begin a new generation of the tree - Tambalacoque

Biological indicator species are unique environmental indicators as they offer a signal of the biological condition of a particular habitat Using bioindicators as an early warning of pollution or degradation in an ecosystem can help sustain critical resources

Examples of Primary Succession Bare rock exposed by glacial retreat or severe soil erosion Bare rock exposed by glacial retreat or severe soil erosion Newly cooled lava Newly cooled lava An abandoned highway or parking lot An abandoned highway or parking lot Newly created shallow pond or reservoir Newly created shallow pond or reservoir

Pioneer species start soil formation process by: Trapping wind-blown soil particles and tiny pieces of detritus Trapping wind-blown soil particles and tiny pieces of detritus Producing tiny bits of organic matter Producing tiny bits of organic matter Secreting mild acids that slowly fragment and break down the rock Secreting mild acids that slowly fragment and break down the rock Lichen

Examples of Secondary Succession Abandoned farmlands Abandoned farmlands Burned or cut forests Burned or cut forests Heavily polluted streams Heavily polluted streams Land that has been dammed or flooded Land that has been dammed or flooded

The End