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What Does Migration Mean In Biology

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C Acquiring And Designating Habitat For The Benefit Of Species Individuals And Populations

BS Biology Major in Medical Biology as a Means to Lessen Professional Migration

This legal approach involves delineating a boundary around an identified area and protecting, conserving, and managing the area and the animal and plant populations within. Three applications of this approach are: 1) designation of existing federal land, 2) federal acquisition of full or partial interests in state or private lands, and 3) federal designation of state or private lands as special areas. First, existing public lands may be designated as national parks, wilderness areas, marine sanctuaries, wild and scenic rivers, and national wildlife refuges. In particular, public lands may be designated as migration corridors. Second, property interests in state or private lands can be acquired in full or partially, typically as easements. Lastly, state or private land may be designated as special areas, such as a migration corridor. Designation of state or private land as a special area may be valuable to draw public attention to the area and to motivate further actions such as acquisitions, funding, and restoration.

Acquisitions and designations are likely to be most effective for migratory species that occupy and use a few delineated sites. For example, acquisitions will be most readily identified and likely produce the most bang for the buck when applied to obligate, narrow-fronted migrations moving along relatively narrow corridors or those that gather in mass aggregations at a limited number of stopover, breeding, and overwintering sites.

A Holistic View Of Migration

Recognition that the various phenomena comprising migration occur across a series of organizational levels helps greatly to distinguish them, refine our separate knowledge of each, and develop both descriptive and explanatory understandings by drawing from lower and higher levels . Nevertheless, migration is a single phenomenon, and we should aim to recognize its unitary structure. This has been attempted by in the form of a conceptual model of what they termed a migration system . The model incorporates both components and processes and explicitly considers the environment in which the migrant population survives as well as the migrants’ responses and adaptations to it. The four system components are as follows: A migration arena comprising the environment to which the migrants are adapted a migration syndrome, which is the suite of traits enabling migratory activitythis suite comprising both locomotory capabilities and a set of responses to environmental cues that schedule and steer the locomotory activity the genetic complex that underlies the syndrome and a population trajectory comprising the route followed by the migrants, the timing of travel along it, the points along it where migration temporarily ceases, and the times when these points are occupied for breeding and other key life stages.

Migration: Meaning Types And Effects

After reading this article you will learn about:- 1. Meaning of Migration 2. Types of Migration 3. Concepts 4. Effects

Meaning of Migration:

Migration is the third factor for changes in the population, the other being birth rate and death rate. As compared to birth rate and death rate, migration affects the size of population differently. Migration is not a biological event like birth rate and death rate, but is influenced by the social, cultural, economic and political factors.

Migration is carried by the decision of a person or group of persons. The changes occurring in the birth rate and death rate do not affect the size and structure of the population on a large scale, while migration, at any time, may cause large scale changes in the size and structure of the population.

The study of migration is of vital importance because the birth rate, death rate and migration determine the size of population, the population growth rate and thus the structure of population. In addition, migration plays an important role in determining the distribution of population and supply of labour in the country.

Thus, the study of migration is also useful for formulating economic and other policies by the government, economists, sociologists, politicians, and planners along with demographers

Migration may be permanent or temporary with the intention of returning to the place of origin in future.

Types of Migration:

Migration is of the following types:

Immigration and Emigration:


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Predation And Parasitism Risk

Partial migration may confer some reduction in the risk of predation or parasitism, by movement into an enemy free space, resulting in improved survival for migrants. However, the role of trophic interactions has received relatively little attention in the partial migration literature and has rarely been studied in migratory insects . Nonetheless, there is evidence that migration can reduce the prevalence of infection from the protozoan parasite, Ophryocystis elektroscirrha in monarchs , with resident populations having higher infection rates than migrant populations , providing evidence of migratory escape from contaminated environments.

C Geographic Variation In Migrations: Implications For Conservation

Biology Bonanza Quiz

The existence of geographic and intra-specific variation in migrations described abovethat is, the degree to which the distances or routes traveled by migrants vary among different subgroups poses both challenges and opportunities for conservation of migrations that must be considered.

With respect to challenges, for example, the research efforts required to obtain knowledge of patterns of migratory connectivity between breeding and wintering grounds and to characterize the migratory routes and stopover requirements for particular animal groups becomes greater, more expensive, and more logistically demanding when intra-species variation must be considered. However, once this knowledge is obtained, only certain subspecies or races may prove to exhibit migratory behavior or traverse imperiled landscapes on their journey. Here lies the opportunity: armed with the knowledge of which populations migrate, conservation specialists will be better able to design policies and management strategies that are targeted, smaller-scale, more efficient, and ideally more effective at protecting the most important migrations per se rather than the migratory species as a whole. If limited funds and resources are mandated to protect a particular migration, prioritization efforts would be aided by a clear understanding of which geographic variants exhibit the most ecologically or culturally valuable, or the most imperiled migrations.

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V Migrations As Dynamic Phenomena: Responses To Environmental Change

In addition to the spatial variation in migratory biology observed both among and within populations, migrations also vary within species across another important axis: time. Over both contemporary and historical time scales, the characteristics of migrations are constantly changing in response to shifting environmental conditions. As anthropogenic climate change and habitat alteration progress at alarming rates, this reality must be an especially important aspect of research, policy, and management agendas for migrationboth with respect to researching and mitigating the detrimental effects of altered environments on migrations, but also insofar as the habitat ranges and phenologies of migratory animals represent moving targets.

Below, we highlight two examples from the Dark-eyed Junco, both of which illustrate how human activities may have led to dramatic shifts in migratory processes over time, even over just a few decades. While these examples are striking because we can time their occurrence, the diversity of migratory phenomena across closely related species and populations , as well as additional contemporary examples that also demonstrate recent and rapid shifts in migration in response to changing climates and urbanization, indicate that migrations can be quickly gained, lost, or altered as environments change.

Adaptations And Resource Use: Migration Immigration Emigration

Many animals migrate, traveling each year in search of better weather, more food, or a mate. The best known migrating animals are birds, which typically migrate south in the winter to avoid cold weather, and come back north in the summer to raise their young. The map below show the migration route of the Swainson’s hawk.

Other animals migrate too. Humpback whales, for instance, will swim thousands of miles north each year just to feed, and they only eat during the summer! In the winter, they swim thousands of miles back to mate and have their young.

Immigration and emigration are not the same as migration, because they are permanent. Immigration means an animal establishes a home in a habitat because it has resources it can utilize or because the habitat is ideal for them. Emigration means an animal leaves its home because the habitat is no longer ideal for them and they need to find a more suitable environment. Animals that immigrate or emigrate do not return to the land they left. Immigration can allow new populations of a species to form and emigration can cause local populations to decline.

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What Is Cell Migration And What Is Its Physiological Relevance

Cell migration is the directed movement of a single cell or a group of cells in response to chemical and/or mechanical signals. It is a fundamental cellular process that occurs throughout life, starting during embryonic development and continuing until death, and at times it can contribute to pathogenic states in disease.

In a developing embryo, cell migration is the driving factor for various morphogenetic events. For instance, during gastrulation in very early embryos, groups of cells migrate as sheets to form the three germ layers. Subsequently, cells from the germ layers migrate to various target locations, where they specialize into distinct cell populations that make up various tissues or organs in the embryo.

In adult organisms, cell migration occurs during vital cellular processes such as tissue renewal and repair, wherein old or damaged cells are replaced by the migration of newly formed cells from the underlying tissue layers. Such events are essential to maintain tissue integrity and homeostasis. Cell migration also plays a role in mediating immune responses during infections, in which phagocytic cells such as neutrophils circulating in the bloodstream migrate to the infected tissues and destroy the invading pathogens.

Migration: Definition And Scope

Migration | Definition of migration
Chapter 2 Migration: definition and scope
Oxford University Press

This chapter defines migration as a function of its physiological and behavioral characteristics and how natural selection acts on these. Migration is then described in terms of its ecological outcomes. The pioneering studies of J. S. Kennedy on migratory aphids are discussed, showing how migration can be experimentally characterized. The properties of migration from initiation to conclusion are elaborated. From comparisons across diverse taxa, it is stressed that migration syndromes include undistracted movement and are based in a common set of flexible traits rather than a phylogenetically ancient genome. These traits define migration irrespective of route followed. The latter is an outcome. The one-way movements often called dispersal probably include migrations because many display the defining characteristics. Dispersal is better considered a population phenomenon, meaning scattering of individuals, along with other phenomena of population redistribution that concentrate organisms, namely aggregation and congregation. All are potential outcomes of the individual behavior of migration. Natural selection acts primarily on individuals, so migration is best defined as a property of individuals. There is a closed hierarchy of organizational levels concerning migration with the highest level, natural selection, acting on the lowest level, the genes underlying migration syndromes.

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Ii Existing Ecological Typologies Of Migration

Aphids, bats, caribou, dolphins, elephants, fish, giraffes, and hummingbirdsâsuch are just a few examples of the hundreds of animal taxa, together encompassing tens of thousands of individual species that demonstrate some type of migratory behavior. Although migratory organisms share the unique and fundamental âneed to move,â the variety of migratory animals and the diverse characteristics of their particular migrations require careful consideration if effective generalizations and distinctions are to be made in the context of law, policy, and management strategies. Focusing conservation agendas on protecting or restoring the phenomena of migration will require cross-disciplinary dialogue about fundamental but complicated questions such as, âWhat is a migration?,ââWhich types of migrations are currently most imperiled?,â or âAre certain categories of migrations ecologically more valuable than others?â

How Do Birds Navigate

Migrating birds can cover thousands of miles in their annual travels, often traveling the same course year after year with little deviation. First-year birds often make their very first migration on their own. Somehow they can find their winter home despite never having seen it before, and return the following spring to where they were born.

The secrets of their amazing navigational skills arent fully understood, partly because birds combine several different types of senses when they navigate. Birds can get compass information from the sun, the stars, and by sensing the earths magnetic field. They also get information from the position of the setting sun and from landmarks seen during the day. Theres even evidence that sense of smell plays a role, at least for homing pigeons.

Some species, particularly waterfowl and cranes, follow preferred pathways on their annual migrations. These pathways are often related to important stopover locations that provide food supplies critical to the birds survival. Smaller birds tend to migrate in broad fronts across the landscape. Studies using eBird data have revealed that many small birds take different routes in spring and fall, to take advantage of seasonal patterns in weather and food.

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Causes Of External Migration

External migrations may be due to different factors, such as:

  • Wars, military, political or civil conflicts, as well as other reasons of force majeure that force them to leave the country of origin .
  • Bad living conditions in the country of origin and better in the country of destination, which causes economic migration.
  • Personal reasons that lead to pursuing foreigners, such as falling in love or individual life opportunities.

Migration As A Form Of Individual Movement

Migration: Meaning and Concepts

Although the outcome of migration can be viewed as a population process, it is useful to focus first on the migratory behavior of individuals, as this underlies the collective aspects. Further, because natural selection acts primarily on individuals, understanding the function of migration, and how migration systems are maintained and evolve, will ultimately concern the genotypes and phenotypes of individual migrants .

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Iii Typology Of Existing Legal Approaches

This Part presents a classification of legal approaches used in existing conservation laws that are relevant for the protection of migratory animals and their migrations as phenomena of abundance. We discuss exemplars for each of five approaches, and examine the approaches that are likely to be most effective for particular migratory species and migrations.

In general, existing conservation laws are not optimally effective for protecting migratory species and their migrations while still abundant because those laws typically focus our attention on species declines, viable populations, and reactive conservation actions. Maintaining minimal viable populations, however, may not sustain the ecological, psychological, cultural, and economic benefits associated with migrationsâthese benefits of migration, as well as the persistence of the migratory behavior itself, likely require abundances higher than minimum viable populations. The leading illustration of this limitation is the Endangered Species Act . The ESA, while offering protections for listed species that migrate, is not fundamentally concerned with protecting the functional benefits derived from the process of migration. Rather, the ESA is generally concerned with protecting the benefits that flow from the existence of the species, and therefore the minimum demographically viable population will suffice for this purpose.

A Funding Assistance Coordination And Information Generation And Exchange

A common approach used by existing federal conservation laws is to authorize the transfer of funds from the United States government to domestic state, local, or private projects, or to foreign countries that are important ecologically but less able to fund conservation projects. Such projects may include land acquisition, restoration, education, and research activities. Often associated with authorization of funding and technical assistance for conservation projects are incentives to promote cooperation, coordination, and information generation and sharing among stakeholders. Funding and assistance are often tools of choice for influencing land uses on state, local, and private property because of their voluntary nature, although funding of third-party conservation projects typically requires federal approval based on specified criteria.

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What Happens At The Telophase

During telophase, the chromosomes arrive at the cell poles, the mitotic spindle disassembles, and the vesicles that contain fragments of the original nuclear membrane assemble around the two sets of chromosomes. This dephosphorylation results in the formation of a new nuclear membrane around each group of chromosomes.

B Gaps In Migration Conservation

What Is Migration? (In Animals)

In Part I, we stated that effective conservation of migrants requires coordinated work by researchers, policy makers, and managers. Such coordination can be difficult precisely because the three disciplines view migrants differently, as we have illustrated in the previous Parts. Here, we identify places where efforts to conserve migratory species are incompletely coordinated among the three disciplines.

1. Gaps in Scientific Information to Support Conservation of Migratory Species

Managers, in contrast, may need similar kinds of data for many species or contextsâat most modest new ground for science, but important for conservation of a diversity of species. Similarly, although year-to-year variation in behavior and demography is important to science from time to time in order to answer certain kinds of questions, it is of ongoing interest to managers in order to assess the status of the species they manage.

The Department of the Interior , the research arm of the Forest Service, the states , and programs designed to support hunting and fishing support research that generally seeks to meet wildlife and land management needs of state and federal natural resource agencies. However, migration studies are not broadly identified as a priority for such research.

2. Gaps in Laws and Policies

a. Gaps in Addressing Fragmentation and Obstacles
b. Jurisdictional Gaps
c. Taxonomic Gaps
d Gaps in Spatial Coverage
e. Limitations on Protection at Ecologically Relevant Levels

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Iii Geographic And Subspecific Variation In Migration

Migration is rarely a unitary phenomenon even in those species usually regarded as classic migrants.

Distinguishing between migratory and non-migratory species might sound like an ordinary exercise for field biologists, but if one looks closely, many species elude such simple categorizations. In a few casessuch as the long-distance, complete, and obligate migrations exhibited by Arctic Terns all members of the species must migrate or die. For the Arctic Terns, the limited geographic distributions of their specific breeding and wintering habitat, as well as the dramatic environmental fluctuations at the poles, ensure that staying behind or making only part of the journey is not an option. Even among Arctic Terns, however, variation exists in the form of the migratory routes taken between the contiguous polar rangesthe species splits into tracks, traveling down different coasts of the Americas, Eurasia, and Africa.

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