Unit 4: Pt. 1 Community Ecology AP Environmental Science

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

Habitat fragmentation causes significant decline in species diversity Reduce species richness Reduce amount of functional habitat Cause isolation of a species 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 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 Using migration corridors to link smaller habitat patches

Bridges over roads Tunnels under roads

Who benefits from wildlife corridors?

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

Three Major Factors Affect Species Diversity Latitude (distance from equator) Depth (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 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 distance from the mainland

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

General principles of island colonization 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

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

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

Sea Otter: A keystone species

Sea otters feed on the sea urchin which eats the base of the kelp plants (killing the kelp plants)

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

In 1505, the Portuguese became the 1st 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

The last dodo bird was killed in 1681 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

Fish are an excellent indicator of watershed health because: Live in water all of their life Differ in their tolerance levels to amount and types of pollution Are easy to collect Live for several years Are easy to identify

Benthic macroinvertebrates are good indicators because: Live in water for all or most of their life Stay in areas suitable for their survival Are easy to collect Differ in their tolerance to amount and types of pollution Are easy to identify Often live for more than one year Have limited mobility Are integrators of environmental condition

Possible Causes of Amphibian Declines Loss of habitat Prolonged drought Pollution (pesticides, nitrates, pH) Increases in ultraviolet radiation Increase parasitism Overhunting Epidemic diseases Immigration or introduction of alien predators and competitors

Amphibians of all shapes and sizes

Five Basic Types of Interactions Between Species Interspecific competition Predation Parasitism Mutualism commensalism

“sucking” disc does not harm shark Remora Commensalism

Bacteria in your intestines

Significant Niche Overlap – one of the competing species must Migrate to another area Shift its feeding habits or behavior through natural selection or evolution Suffer a sharp population decline Become extinct in that area

How Species Avoid Predators Run, swim, fly fast Highly developed sense of smell or sight Protective shells Thick bark Spines camouflage Parts that break off Chemical warfare Warning coloration Behavioral strategies Puffing up Mimicry Schooling Living in large groups Spreading their wings

Avoiding predators

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

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

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

Three Aspects of Stability Persistence – resist disturbance Constancy – keep within limits Resilience – bounce back

Does species diversity affect ecosystem stability? Simple ecosystem food web vs. complex and more diverse ecosystem Elimination of one species from complex ecosystem has little effect on rest of food web (unless it was a keystone species) Arctic tundra less stable than temperate deciduous forest – result is arctic tundra experiencing drastic population shifts

Immature Ecosystem vs. Mature Ecosystem Small plant size Low species diversity Simple food web Mostly generalized ecological niche Mostly producers, few decomposers Efficiency of nutrient cycling is low Large plant size High species diversity Complex food web Mostly specialized ecological niche Mixture of producers, consumers, decomposers High efficiency of nutrient cycling

Negative feedback loops promote stability in a dynamic system Role of positive and negative feedback loops in the stability of an ecosystem Negative feedback loops promote stability in a dynamic system Positive feedback loops usually leads to one or more populations being wiped out (local extinction) Positive feedback loop = causes a system to change further in the same direction (positive refers to the direction of change, rather than desirability of the outcome) Negative feedback loop = causes a system to change in the opposite direction

Positive feedback loop A warmer atmosphere will melt ice and this changes the Earth’s albedo which further warms the atmosphere An increase in temperature will melt the permafrost in the tundra causing a release of trapped carbon dioxide and methane (both are greenhouse gases)

Negative feedback loop Predator-prey relationship The moose population will rise and fall in response to the wolf population

Positive and negative feedback loops coupled together The settlers of Easter Island found plenty of natural resources The Islanders had many children and the population went up The island’s tree and soil resources were used faster than they could be renewed Without trees Islanders could not build traditional seagoing canoes All of the island’s natural resources were used up Both the population and the civilization collapsed

Example of negative feedback loop An example of negative feedback is body temperature regulation. If blood temperature rises too high, this is sensed by specialized neurons in the hypothalamus of the brain. They signal other nerve centers, which in turn send signals to the blood vessels of the skin. As these blood vessels dilate, more blood flows close to the body surface and excess heat radiates from the body. If this is not enough to cool the body back to its set point, the brain activates sweating. Evaporation of sweat from the skin has a strong cooling effect, as we feel when we are sweaty and stand in front of a fan. Read more: Homeostasis - Biology Encyclopedia - cells, body, examples, function, human, process, system, organisms, blood http://www.biologyreference.com/Ho-La/Homeostasis.html#ixzz11mSI4EzD

Example of positive feedback loop An example of its beneficial effect is seen in blood clotting. Part of the complex biochemical pathway of clotting is the production of an enzyme that forms the matrix of the blood clot, but also speeds up the production of still more thrombin. That is, it has a self- catalytic , self-accelerating effect, so that once the clotting process begins, it runs faster and faster until, ideally, bleeding stops. Thus, this positive feedback loop is part of a larger negative feedback loop, one that is activated by bleeding and ultimately works to stop the bleeding. Read more: Homeostasis - Biology Encyclopedia - cells, body, examples, function, human, process, system, organisms, blood http://www.biologyreference.com/Ho-La/Homeostasis.html#ixzz11mSpKQyy