Ecology

=** ECOLOGY **= flat

**Animal Migration**


 * To animals, migration is crucial to their survival of their species.
 * Migration is a large scale movement of the animal species from one place to another.
 * Migrations are usually tied into seasonal changes in weather, feeding, or mating/breeding patterns -- but not all.
 * **Irruptive migrations** don't follow any pattern at all.
 * Nomadic species move from one place to another whenever they are out of food supply in one area.
 * When ever member of the species migrates, its called a **complete migration.**
 * When some members migrate and some stay in the same place, its called **partial migration.**
 * Usually happens when the range of species is fairly large enough that some of the members live in a place that is fairly warm, while others live in a region that gets too cold in the winter.
 * Ex. Barn Owls
 * **Altitudinal migration** are used by some animals that live in mountainous areas.
 * They travel to lower altitudes when winter snow hits the upper mountains.
 * Ex. Some spotted owl do this


 * When a drastic change in the environment or climate, it can result in **removal migration**.
 * When human development drains swamplands, clear-cuts forests, species will try to move to a different area and not return to their original home.
 * Caribou hold the world record for longest overland migration -- over 2000 miles each year.
 * Most migrations are food - driven

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 * Other reasons why animals migrate:
 * to find essential minerals eg wildebeest, African elephant
 * to find shelter or avoid harsh winter weather eg Mexican free-tailed bat, red-sided garter snake, monarch butterfly, Caribbean spiny lobster
 * to search for a mate eg male sperm whale, Australian giant cuttlefish
 * to give birth, lay eggs or raise young eg grey whale, European toad, green turtle, emperor penguin
 * to moult in a safe place eg walrus, shelduck, yellow-lipped sea krait (a venomous sea snake)
 * to flee overcrowded conditions eg Norway lemming, desert locust
 * Migration is dangerous and to stay alive, migratory animals have evolved in lots of ways to reduce risks such as:
 * travel in ** groups ** for protection
 * ** hitch a lift ** on ocean currents, favourable winds or rising currents of warm air called thermals
 * ** stop en route ** to rest and refuel
 * feed intensively before setting off to lay down fat reserves as fuel – a form of behaviour called ** hyperphagia **
 * ** radical physical transformation ** . Some birds develop larger, more powerful breast muscles that are used in flight and shrink non-essential organs – otherwise they would be too heavy.

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="Magnetic Map" Found to Guide Animal Migration=


 * According to a few studies, the reason that why some migrating animals, birds, salmon etc, never seem to get lost because the migration routes and navigation skills are hard-wired into the animal's brains.
 * Studies of loggerhead turtles revealed that hatchlings have the ability to sense the direction and strength of Earth's magnetic field, which they use for navigating along the turtles' regular migration route.
 * Their migration begins and ends on the shore of easter Florida, and they circuit around the Sargasso Sea, the entire journey takes them 5 - 10 years to complete.
 * Studies showed they put these turtles that have never been exposed to water, and yet they were still able to process the magnetic informatiom and change their swimming direction accordingly to avoid the cold waters.
 * Researchers do not know how the turtles sense them magnetic field or what part of the brain is involved.
 * Mole rats also dig tunnels up to 200m long and build their nests in the southernmost tip of their burrows. As the direction of the of the magnetic field changed, so did the moles' nests.

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= Diel vertical migration =

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 * Usually involves migration into food-filled shallow water at night, and descent into relatively food-depleted depths during the day. Normal DVM is when migration occurs at dawn and dusk.
 * 2 general patterns:
 * Nocturnal migration (as above): most common
 * Reverse migration: surface rise during the day, night- time descent to a maximum depth.
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Occurs in freshwater and marine systems
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Occurs in all major groups of zooplankton
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Ex. of Diel vertical migrators
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Crustacea: dominant group: copepods, especially the calanoids, and euphausiids (krill)
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Siphonophores
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Chaetognaths
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Squid
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Fish
 * <span style="margin-bottom: 0px; margin-left: 0px; margin-right: 0px; margin-top: 0.5em; padding-bottom: 0px; padding-left: 3em; padding-right: 0px; padding-top: 0px;">Protists: Reverse DVM (down at dusk, up at dawn)


 * [[image:http://www.mbari.org/seminars/1998/oct21_steinberg.jpg height="275" caption="external image oct21_steinberg.jpg"]] ||

=Gene Flow (Gene Migration)=

Gene flow, also called gene migration, the introduction of genetic material (by interbreeding) from one population of a species to another, thereby changing the composition of the gene pool of the receiving population. The introduction of new alleles through gene flow increases variability within the population and makes possible new combinations of traits. In human beings gene flow usually comes about through the actual migration of human populations, either voluntary or forced. [|Britannica]

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: normal;">**Human Development is a Major Barrier to Gene Flow**
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: normal;">Human development can fragment ecosystems into isolated islands and in the process seriously reduce the genetic variation of the creatures on those islands.
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: normal;">A great challenge facing conservation biologists is the maintenance or establishment of corridors or connections between these isolated fragments in order to maintain a healthy genetic variation through the facilitation of gene flow.

<span style="border-collapse: collapse; color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: normal;">Human Mobility Generates High Gene Flow

 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: normal;">While human constructions, occupation, and activity may pose barriers to other species, humans themselves are the most mobile and wide-ranging animal on the planet.
 * <span style="font-family: Arial,Helvetica,sans-serif; font-size: 12px; line-height: normal;">Genetic analyses of humans of different geographical regions and races reveal tremendous rates of gene flow and a subsequent mixing of many human gene pools or the “dilution of the races” as it has been called.

===<span style="border: 0px none initial; font-family: Arial,Helvetica,sans-serif; font-size: 13px; margin: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding: 0px;">Mechanisms of Evolution ===
 * Evolution encompasses changes on 2 very different scales:
 * From an increase in the frequency of a gene for colored spots on the feathers of a bird (//<span style="border: 0px none initial; font-family: Arial,Helvetica,sans-serif; font-size: 12px; margin: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding: 0px;">microevolution //)
 * To something as grand in scale as the evolution of the entire bird lineage (//<span style="border: 0px none initial; font-family: Arial,Helvetica,sans-serif; font-size: 12px; margin: 0px; outline-color: initial; outline-style: initial; outline-width: 0px; padding: 0px;">macroevolution //).
 * Despite the scale on which it happens, evolution at both levels is driven by the primary mechanisms of natural selection, mutation, genetic drift, and gene flow.

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=Forest Migration=

<span style="line-height: 1.5em; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0.4em;">**Forest migration** is the movement of large seed plant dominated communities in geographical space over time. <span style="line-height: 1.5em; margin-bottom: 0.5em; margin-left: 0px; margin-right: 0px; margin-top: 0.4em;">The emphasis of forest migration is placed on the movement of the tree communities that make up the forest community. Though an individual tree is permanently fixed in a location, tree populations may migrate over the landscape through generations. Tree migration is controlled by two overlying forces:
 * 1) Environmental suppression and dispersal capacity of the population by seed.
 * 2) Though the true rate of forest expansion is difficult to quantify, efforts are being made to evaluate and predict past, current, and future rates and extents of forest movements.

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 * <span style="font-family: Verdana,Geneva,Arial,Helvetica,sans-serif; font-size: 11px; line-height: normal;">We need to migrate user and computer accounts from one forest to another.
 * <span style="font-family: Verdana,Geneva,Arial,Helvetica,sans-serif; font-size: 11px; line-height: normal;">Strange enough, most sites that come up when searching forest migration are computer related.
 * <span style="font-family: Verdana,Geneva,Arial,Helvetica,sans-serif; font-size: 11px; line-height: normal;">Cross forest migration with exchange server

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=Seeds Dispersal/Migration=

**Seed dispersal** is the movement or transport of seeds away from the parent plant. >>> [|Source] [|Source]
 * Plants have limited mobility and consequently rely upon a variety of dispersal vectors to transport their propagules, including both abiotic and biotic vectors.
 * Seeds can be dispersed away from the parent plant individually or collectively, as well as dispersed in both space and time.
 * The patterns of seed dispersal are determined in large part by the dispersal mechanism and this has important implications for the demographic and genetic structure of plant populations, as well as migration patterns and species interactions.
 * There are five main modes of seed dispersal:
 * gravity
 * Seeds fall to the ground.
 * wind
 * The kind of seeds which are often wind dispersed are smaller seeds that have wings or other hair-like or feather-like structures.
 * Plants that produce wind blown seeds, like the dandelion, often produce lots of seeds to ensure that some of the seeds are blown to areas where the seeds can germinate.
 * ballistic
 * Several kinds of plants "shoot" seeds out of pods. The seeds can travel quite a few feet from the plant this way.
 * water
 * Many aquatic plants and plants that live near water have seeds that can float, and are carried by water.
 * Plants living along streams and rivers have seeds that float downstream, and therefore become germinate at new sites.
 * The size of the seed is not a factor in determining whether or not a seed can float. Some very large seeds, like coconuts, can float. Some small seeds also float.
 * animals
 * Some plants, like the burr at left, have barbs or other structures that get tangled in animal fur or feathers, and are then carried to new sites.
 * Other plants produce their seeds inside fleshy fruits that then get eaten be an animal. The fruit is digested by the animal, but the seeds pass through the digestive tract, and are dropped in other locations
 * Some animals bury seeds, like squirrels with acorns, to save for later, but may not return to get the seed. It can grow into a new plant.