Monday, August 16, 2010

Animals and amphibians

Looking for animal facts? You've come to the right place. Animals are one of the basic groups of life on Earth. They all share a handful of traits—they move, they feed on other organisms, they're multicellular and they reproduce sexually. Animals inhabit nearly every corner of the globe including frozen tundra, tropical forests, parched deserts, deep ocean vents, and mountain peaks. To better understand animals, scientists sort them into subgroups including amphibians, arthropods, birds, cnidarians, fishes, insects, mammals, molluscs and reptiles.


Basic Animal Facts

Let's begin with the basics. Animals belong to the Kingdom Animalia, a group also known as the Metazoa. Animals are multicellular organisms that are capable of locomotion and rely on other organisms to obtain their nourishment. There are many different groups of animals, among which the better known groups are amphibians, birds, invertebrates, fishes, mammals, and reptiles.

Amphibians

Amphibians are four-limbed vertebrates that include salamanders, newts, caecilians, frogs, and toads. Early amphibians arose during the Devonian Period, 370 million years ago, and were the first vertebrates to venture out from the water and adapt to life on land. Despite their early colonization of land, most amphibians have never fully severed their ties with aquatic habitats.

Arthropods

Arthropods are invertebrates that include insects, spiders, crustaceans, scorpions, and centipedes. Arthropods are bilaterally symmetrical and have segmented bodies. Their body is covered with an exoskeleton and many arthropods have compound eyes. Arthropods are a highly successful group of animals—they account for over three quarters of all known living and fossil organisms.

Birds

Birds are four-limbed vertebrates that have wings, feathers, hollow bones, and other adaptations for an aerial lifestyle. Flight consumes a great deal of energy and consequently these warm-blooded animals have high metabolic rates. Birds evolved from reptiles during the Mesazoic Era about 150 million years ago. Today, an estimated 9000 species of birds inhabit our planet.

Cnidarians

Cnidarians are a group of invertebrates that includes jellyfish, hydra, sea anemones, corals, and sea pens. Cnidarians have radial or biradial symmetry. The basic body form of cnidarians is simple, consisting of a stomach sac with a single opening. The life cycle of many cnidarians includes a free-swimming medusa and a sessile polyp.

Fishes

Fishes were among the first vertebrates to evolve. The earliest known fishes were the ostracoderms, a now-extinct group of jawless fishes that appeared in the Cambrian Period. Other early fish include the conodonts and the agnanthans. Fish later evolved jaws and diversified into a number of lineages including cartilaginous fishes, ray-finned fishes and lobe-finned fishes.

Insects

Insects are a highly successful group of invertebrates. With somewhere between 750,000 and 30 million species of insects alive today, insects account for more species of animals than any other class of animals. The body of an insect is made up of a head, thorax, abdomen, a pair of compound eyes, a pair of antennae, and a set of complex mouthparts.

Mammals

Mammals are four-limbed vertebrates that have mammary glands, hair, a diaphram, a four-chambered heart, and a large cereberal cortex. Seventy million years ago when reptile diversity declined, mammals took over habitats once unavailable to them. Mammals have successfully adapted to and colonized a wide variety of habitats including land, air, and water.

Molluscs

Molluscs are a highly diverse group of invertebrates that include squid, octopuses, cuttlefish, nudibranchs, snails, slugs, limpets, sea hares, mussels, clams, oysters, scallops and many other groups of organisms. There are more than 100,000 species of molluscs making them second in diversity to only the arthropods. The branch of zoology devoted to the study of molluscs is known as malacology.

Reptiles

Reptiles are four-limbed, cold-blooded vertebrates that evolved from amphibians about 340 million years ago. There are two characteristics that distinguished early reptiles from amphibians and enabled them to colonize terrestrial habitats more extensively than their ancestors: scales and the ability to lay hard-shelled amniotic eggs.
Lions are definitely not loners. In fact, lions are unique among felids in that they are the only species of cat that forms social groups. All other cats are solitary hunters that, outside of mating season, shy away from others of their kind.
The two social groups that shape the lives of lins are prides and coalitions. A pride is a group of 1 to 18 female lions and their young. A coalition is a group of 1 to 9 male lions. A coalition of males competes with other male coalitions for exclusive access to a pride of females. A coalition that wins a pride remains associated with the pride for a period of about 3 to 4 years. After that time, challenges from other coalitions of nomadic males often prevail and the resident coalition is displaced.
When one coalition ousts another from its place within a pride, the consequences are fatal for any unweaned cubs sired by the previous coalition's males. The incoming coalition males kill the cubs and evict any subadult males from the pride. Adult females are thus hastened to return to estrous and mate with the new males.

Within the pride-coalition group, males compete with one another to form pairs with females. Once all males have paired off with females, they prevents other males from mating with their mate. But often there are more females than there are males and the unpaired females choose among the males as mates. In this case, unpaired females often prefer darker-maned males, as they are more likely to have greater vitality, fighting prowess and social status than their lighter-maned counterparts.

Refs:

Kingdon J. 2007. The Kingdon Field Guide to African Mammals. Harcourt Brace & Company. New York, NY. 464 p.
Photo (top) © Denny Allen / Getty Images. Photo (bottom) © Adam Jones / Getty Images.
The Adelie penguin (Pygoscelis adeliae) is perhaps the most familiar of all Antarctic penguin species. The Adelie was named after the wife of French polar explorer, Dumont d'Urville. Adelies are on average smaller than all other species of penguins.
Adelie penguins are known to form large colonies, sometimes consisting of more than 200,000 pairs of birds. They breed on rocky coasts and islands where each mating pair constructs a nest made out of stones. In early November, the female lays two light-green eggs and the parents take turns incubating the egg and foraging for food in the sea (Burnie and Wilson 2001, 267).
The color pattern of Adelie penguins is the classic penguin pattern. Adelies have a bright white belly and chest which contrasts sharply with their black back, wings, and head. Adelie penguins have white rings around their eyes. Adelies grow to heights of 46-61cm and weights of 4-5.5kg. The plummage of both sexes is similar.
The Adelie penguin population is considered stable and is perhaps increasing. There are an estimated 2 to 2.6 million pairs. Because the Adelie population is dependent on the abundance of krill in the seas surrounding Antarctica, scientists use these birds as indicator species to gauge the health of the waters around the earth's southernmost landmass.
  • Mass: 3.6-5kg
  • Length: 69 cm, average
  • Diet: mostly Antarctic krill, some small fish and cephalopods
  • Breeding Season: early spring to summer
  • Clutch Size: usually 2 eggs
  • Time to Hatching: 24-39 days
  • Time to Fledging: 28 days (average)
  • Sexual Maturity: 3-6 years (female) 4-6 years (male)

Classification:

Range and Habitat:

Adelie penguins inhabit rocky coasts, ice floes, and islands along the coastline of Antarctica. They forage in the waters surrounding Antarctica. Their distribution is circumpolar.

Refs:

  • Burnie D, Wilson DE. 2001. Animal. London: Dorling Kindersley. 624 p.
  • Fawkes R. 1999. Pygoscelis adeliae, Animal Diversity Web. November 21, 2005.

Amphibians

  •             Red-eyed Tree Frog

    Photo © Alvaro Pantoja / Shutterstock.
    The red-eyed tree frog (Agalychnis callidryas) belongs to a diverse group of frogs known as the new world tree frogs (Family Hylidae). Read more about the red-eyed tree frog.

    Axolotl

    Photo © Aureapterus / iStockphoto.
    The Axolotl (Ambystoma mexicanum) is a salamander native to Lake Xochimilco in central Mexico. Axolotl larvae do not undergo metamorphosis so when they reach maturity, the retain gills and remain entirely aquatic.

  • Fire Salamander

    Photo © Gorpenyuk / iStockphoto.
    The fire salamander (Salamandra salamandra) is black with yellow spots or yellow stripes that inhabits the deciduous forests of southern and central Europe.

  • Leopard Frog

    Photo © Gilles DeCruyenaere / Shutterstock.
    Leopard frogs belong to the genus Rana, a group of frogs that inhabit tropical and subtropical regions of North America and Mexico. Leopard frogs are green with distinct black spots.

  • Banded Bullfrog

    Photo © Loong Kok Wei / Shutterstock.
    The banded bullfrog (Kaloula pulchra) is a frog native to Southeast Asia. It inhabits forests and rice fields. When threatened, it can "puff up" so that it appears larger than normal and secretes a toxic substance from its skin.

  • Green Tree Frog

    Photo © Frank Yuwono / Shutterstock.
    The green tree frog (Litoria caerulea) is a large frog that is native to Australia and New Guinea. Its color varies depending on the temperature of the surrounding air and ranges from brown to green.

  • Smooth Newt

    Photo © Steve McWilliam / Shutterstock.
    The smooth newt (Lissotriton vulgaris) is a species of newt common throughout many parts of Europe.

  • Painted Reed Frog

    Photo © EcoPrint / Shutterstock.
    The painted reed frog (Hyperolius marmoratus) is a native to the eastern and southern parts of Africa where it inhabits temperate forests, savannas, and shrublands.

  • Mexican Burrowing Cacilian

    Photo © Franco Andreone / Wikimedia Commons.
    The Mexican burrowing caecilian (Dermophis mexicanus) is a limbless amphibian that inhabits a range from southern Mexico to northwest Colombia.

  • alifornia Newt

    Photo © Mguntow / iStockphoto.
    The California newt (Taricha torosa) inhabits coastal regions of California as well as the Sierra Nevadas. This newt produces tetrodotoxin, a potent toxin also produced by pufferfish and harlequin frogs. There is no known antidote for tetrodotoxin.
    Amphibians (Class Amphibia) are one of the six basic groups of animals. Amphibians include frogs, toads, caecilians, newts and salamanders. Amphibians are the descendents of the first vertebrates to make the move from life in water to life on land. Despite their early colonization of terrestrial habitats, most lineages of amphibians have never fully severed their ties with aquatic habitats.
    1. Amphibians are divided into three groups which include newts and salamanders, frogs and toads, and caecilians.
    Newts and salamanders (Order Caudata) are slender-bodied amphibians that have a long tail and four legs. Newts spend most of their life on land and return to water to breed. Salamanders, in contrast, spend their entire lives in water.
    Frogs and toads (Order Anura) belong to the largest of the three groups of amphibians. Adult frogs and toads have four legs but do not have tails.
    Caecilians (Order Gymnophiona) are the least-known group of amphibians. Caecilians have no limbs and only a very short tail. They have a superficial resemblance to snakes, worms, or eels but are not closely related to any of these animals.
    2. There are between 5,000 and 6,000 species of known amphibians alive today.
    The IUCN estimates that there are about 6,000 known species of frogs, toads, salamanders, and caecilians. Other sources place the estimated number of amphibian species at about 5,000. Of the three groups of amphibians, frogs and toads are the most diverse, with about 29 families and 4,380 species. Newts and salamanders are the second most diverse group of amphibians, with about 10 families and 470 species. There are only 3 families of caecilians and 170 species (Burnie and Wilson 2001, 22).
    3. The first amphibians appeared approximately 370 million years ago during the Devonian Period.
    During the Devonian Period (408-360 Myr BP), a group of primitive fleshy-finned fishes known as the crossopterygians gave rise to the first amphibians. These creatures were the first vetebrates to colonize terrestrial habitats. The world of those early amphibians was quite different than it is today. There were no birds, no mammals, and no reptiles on land. There were only invertebrates and an assortment of prehistoric plants such as club mosses, ferns, and liverworts. The earliest fossil amphibian is considered to be Ichthyostega, an animal that had four limbs and lungs (Avers 1989).
    4. Amphibians were the first four-limbed vertebrates.
    Early amphibians evolved two pairs of jointed limbs from fleshy-fins of their fish-like ancestors. Amphibians were therefore the first tetrapods, backboned animals that have four limbs. The innovation of limbs enabled early amphibians and their descendents to support their body on land and to move more freely in terrestrial habitats. In addition to the challenge of movement, the transition from water to land presented amphibian ancestors with other adaptive challenges such as breathing air and preventing desiccation (Tudge 2000, 390).
    5. Amphibians have a simple body structure, when compared to other vertebrates.
    Most adult amphibians have 4 limbs with 4 digits on the front limbs and 5 digits on the hind limbs (caecilians are the exception to this rule, having no limbs or digits). Most frogs and toads have a large head, muscular hind limbs, and no tail. Salamanders are long-bodied and have a tail, some species have a reduced number of digits or even lack hind limbs entirely. Amphibians lack a rib cage and have only short ribs. They also lack a diaphram.
    6. Amphibians have delicate, permeable skin.
    The skin of amphibians is delicate and lacks the protection that scales (a characteristic of reptiles) or hair (a characteristic of mammals) provides these other groups of animals. Amphibian skin is permable to water and is characterized by having numerous mucous glands that help keep their skin from drying out. All amphibians also have poison glands in their skin that produce a range of toxins depending on the species, some toxins are merely unplatable while others are lethal.
    7. A group of salamanders known as the plethodontids have no lungs.
    The plethodontids, also called "lungless salamanders" must absorb oxygen through their skin and mouth to breath since they lack lungs. Of all salamanders, the plethodontids are the most diverse group, with about 376 species. They inhabit regions of North America, Central America, South America, southern Europe, Sardinia, and Korea.
    8. Most amphibians have a life cycle that progresses through three stages.
    Most amphibian species have a life cycle that involves three stages, egg, larva, and adult. The transition from larva to adult is known as metamorphosis and in some amphibians such as frogs, toads, salamanders, and newts, the transformation is dramatic. Most amphibians lay their eggs in water (though a few species lay their eggs on land). The eggs of amphibians have no hard shell and instead are encased in a gelatinous mass to prevent the egg from drying out. The life cycle of frogs and toads is perhaps the best know amphibian life cycle, with the tadpole being the larval stage.
    9. The largest amphibian is the Chinese giant salamander (Andrias davidianus).
    As such, it is also the largest salamander in the world, growing to lengths of up to 6 feet. Other large amphibians include the Japanese giant salamander (Andrias japonicus) and the goliath frog (Conraua goliath).
    10. Amphibians are declining around the world.
    According to the IUCN, nearly one-third of all amphibians are known to be threatened or extinct. The largest numbers of threatened species are found in Colombia, Mexico, and Ecuador. Amphibians in the Caribbean are also under grave threat where high percentages of the amphibians that live in the region are threatened or extinct. In recent years, scientists and conservationists have been working to raise public awareness of a global decline in amphibian populations.

    Refs:

    • Burnie D, Wilson DE. 2001. Animal. London: Dorling Kindersley. 624 p.
    • Avers CJ. 1989. Process and Pattern in Evolultion. Oxford: Oxford University Press. 590p.

    Why Amphibians Are in Decline

    Reasons Amphibian Numbers Are Falling Around the World

    In recent years, scientists and conservationists have been working to raise public awareness of a global decline in amphibian populations. Herpetologists first started noting that amphibian populations were falling at many of their study sites in the 1980s. Those early reports were anecdotal and many experts doubted that the observed declines were cause for concern (the argument was that populations of amphibians fluctuate over time and the decline could have been merely natural variation).
    But by 1990, a significant global trend had emerged—one that overstepped normal population fluctuations. Herpetologists and conservationists started voicing their concern for the worldwide fate of amphibians. Their message was alarming: of the estimated 5,918 known species of amphibians that inhabit our planet, a staggering 1,856 species were listed as endangered, threatened or vulnerable on the IUCN Red List (Global Amphibian Assessment 2007).
    Amphibians are considered to be indicator species for environmental health: they have delicate skin that readily absorbs toxins from their environment; they have few defenses and can fall prey to non-native predators; they rely on both aquatic and terrestrial habitats at various times during their life cycle. If amphibians populations are in decline, it is likely that the quality of the habitat in which they live is suffering.
    There are numerous known factors that contribute to amphibian declines—habitat destruction, pollution, the effects of introduced species. Yet research has revealed that even in pristine habitats—those that lie beyond the reach of the bulldozer and crop-duster—amphibians are disappearing at a shocking rate and without explanation. Scientists are now looking to global phenomena for explanations. Climate change, emerging diseases, and increased exposure to UV-B radiation (due to ozone depletion) are all additional factors that could be contributing to falling amphibian populations.
    So it seems the question 'Why are amphibians in decline?' has no simple answer. Instead, amphibians are disappearing due to a complex mixture of factors which include:
    1. Alien Species—Native amphibian populations can suffer decline when alien species are introduced into their habitats. There are a number of ways an introduced species can impact populations of native amphibians. For instance, an amphibian species may become the prey of the introduced species. Alternatively, the introduced species may compete for the same resources required by the native amphibian. It is also possible that the introduced species may form hybrids with the native species and in doing so reduce the prevalence of the native amphibian within the resulting gene pool.
    2. Over-Exploitation—Amphibian populations in some parts of the world suffer decline because they are captured for the pet trade or are harvested for human consumption.
    3. Habitat Alteration and Destruction—Alteration and destruction of habitat has devastating effects on many organisms and amphibians are no exception. Changes to water drainage, vegetation structure, and habitat composition all impact the ability of amphibians to survive and reproduce. For example, the drainage of wetland areas for agricultural use of the land directly reduces the habitat available for amphibians which require aquatic habitat for breeding and foraging.
    4. Global Changes (Climate, UV-B, and Atmospheric Changes)—Global climate change presents a serious threat to amphibians because altered precipitation patterns will likely result in changes to wetland habitat on which amphibians rely. Additionally, increases in UV-B radiation due to ozone depletion have been found to severely impact some species of amphibians.
    5. Infectious Diseases—Significant amphibian declines have been associated with infectious diseases such as chytrid fungus and iridoviruses. A chytrid fungal infection known as chytridiomycosis was first discovered in populations of amphibians in Austrailia but also has been found in Central America and North America.
    6. Pesticides and Toxins—The widespread use of pesticides, herbicides, and other synthetic chemicals and pollutants has severely impacted many amphibian populations. In 2006, scientists at the University of California, Berkeley found that mixtures of pesticides were causing amphibian deformities, reducing reproductive success, harming development, and increasing susceptability to diseases such as bacterial meningitis.

    Refs:

    Things You Can Do To Protect Wildlife

    Little Actions You Can Take to Help Animals

     

    "Whatever you do will be insignificant, but it is very important that you do it."
    ~ Mahatma Gandhi
    It is often easy to feel overwhelmed in the face of species loss and habitat destruction. The problem is large and complex—it's common for individuals to feel powerless. Yet, everything we do is vitally important. We may only do a little bit in the grand scheme of things, but together our seemingly small actions add up to a lot.

    1. Protect Wildlife Habitat

    Photo © Paul Tessier / iStockphoto.
    Perhaps the greatest threat that faces many species is the widespread destruction of habitat. Deforestation, farming, over-grazing and development all result in irreversible changes—soil compaction, erosion, desertification, and alteration of local climatic conditions. Such land use practices vastly alter or even eliminate wildlife habitat. In areas where rare species are present, habitat destruction can quickly force a species to extinction. By protecting habitat, entire communities of animals can be protected together and when communities are kept intact, less conservation intervention is required to ensure species survival. Parks, reserves, and other protected lands are too often the only habitats left untouched by habitat destruction.

    2. Join a Conservation Organization

    Photo © Hidesy / iStockphoto.
    There is a wide range of conservation organizations working to protect endangered animals and habitats. Different organizations have different objectives—some work to protect a small plot of land or to protect whales, others focus on establishing good environmental policies in local government. If you have a specific area of interest, you can often find an organization that is working to protect the species or habitats you're most concerned about. By joining in, you can support well-organized, ongoing efforts to protect species and habitats. And if you want to participate in conservation field work, you can often get involved in specific programs within many conservation organizations that rely to a great extent on help from volunteers.

    3. Reduce the Threat of Invasive Species

    Kudzo, from Japan, growing over vegetation in southeast United States.Photo © LightScribe / iStockphoto.
    The spread of non-native species has greatly impacted native populations around the world. Invasive species compete with native species for resources and habitat. They can even prey on native species directly, forcing native species towards extinction. Another way to reduce the threat of invasive species is to incorporate native plants in your garden and to welcome native animals into your yard.

    4. Recycle and Reduce Energy and Goods Consumption

    Photo © SchulteProductions / iStockphoto.
    By recycling and (reusing as much as we can, we reduce our impact on the environment. Additionally, by reducing the energy we consume, we take a little of the burden off our natural resources (and our pocketbooks). You can also reduce your carbon footprint by first calculating your current carbon footprint and then reduce the amount of carbon you consume. For more information see: Ten Things to Do to Reduce Carbon Emissions.

    5. Minimize use of Herbicides and Pesticides

    Photo © BirdImages / iStockphoto.
    Herbicides and pesticides may keep yards looking nice but they are in fact hazardous pollutants that affect wildlife at many levels. Many herbicides and pesticides take a long time to degrade and build up in the soils or throughout the food chain. Some groups of animals such as amphibians are particularly vulnerable to these chemical pollutants and suffer greatly as a result of the high levels of herbicides and pesticides in their habitat.

    6. Place Decals on Windows to Deter Bird Collisions

    Photo © Missing35mm / iStockphoto.
    Daniel Klem Jr. of Muhlenberg College has estimated that as many as one billion birds in the United States die each year due to collisions with windows. You can help reduce the number of collisions simply by placing decals on the windows in your home and office. Other simple steps you can take to reduce the likelihood of collisions are to re-evaluate feeder placement, draw shades and curtains during brightest parts of day, install tilted window glass, and put screens on outside of windows.

    7. Slow Down When Driving

    Photo © Serega / iStockphoto.
    Many native animals have to live in developed areas and this means they must navigate a landscape full of human hazards. One of the biggest obstacles to wildlife living in developed areas is that created by roads. Roads divide habitat and present a constant hazard to any animal attempting to cross from one side to the other. So when you're out and about, slow down and keep an eye out for wildlife.

    8. Voice Your Concerns and Get Involved Locally

    Photo © Chris Gramly / iStockphoto.
    By letting local and national governments know that you're concerned about endangered species, you're increasing the likelihood that someone will do something about it.

    9. Change Your Career

    Photo © Lingbeek / iStockphoto.
    This may sound extreme but for some people getting involved in the protection of threatened and endangered animals is so important that a career change that enables you to work directly with species of concern may be the most rewarding way of doing so. If you're seeking more information on changing your career, you may want to check out The Working Zoologist.

    10. Share Your Enthusiasm for Wildlife and Nature

    Photo © Creatista / iStockphoto.
    Encourage others to learn about nature, enjoy watching wildlife, and value protecting habitats and species with which we share this planet.
     


     


     

     
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