Search Results

10 | 25 | 50 | 100 items per page

2,097 results

Image

Equilibrium number of species (Sequilibrium) is determined by the intersection of the immigration ( I ) and extinction ( E ) rate curves. P is the maximum number of species in the source pool.

Image

from article Biofilm

Biofilms are highly structured communities of microorganisms that are surface-associated or attached to one another, and are enclosed within a self-produced protective extracellular matrix. Biofilm formation and actions involve a number of stages:…

Image

from article Ctenothrissiformes

A Cretaceous ctenothrissiform fossil, Ctenothrissa sp. (order Ctenothrissiformes), on a limestone matrix found in Lebanon. Size: 90 mm (3.5 in.). (Photo courtesy of The Virtual Fossil Museum)

Image

from article Ecosystem

Image

from article Ecosystem

Image

from article Ecosystem

Food chains are limited by energy transfer. In this illustration, energy is transferred from the Sun to a plant (producer) to a primary consumer and to a secondary consumer. Energy is used by the producer and consumer organisms and is lost to the…

Image

from article Ecosystem

Image

from article Ecosystem

General model of the carbon cycle in ecosystems: (A) carbon dioxide (CO2) from the air; (B) carbon from decomposition; (C) carbon from fossil fuels; (D) natural events (for example, forest fires and volcanoes) release CO2 into the air. (Copyright ©…

Image

from article Biodiversity

Global biodiversity hotspots. There are more than 30 biodiversity hotspots located around the world. These areas have experienced severe habitat losses (at least 70%) as the result of human activities, hampering the work of conservationists in their…

Image

from article Biodiversity

A regional analysis of 25 oceanic regions shows that 92% of all known biodiversity falls into a dozen groups, of which crustaceans (for example, crabs, shrimps, and lobsters), mollusks (for example, snails, bivalves, squids, and octopus), and fish…

Image

from article Biodiversity

Image

from article Hyperbolic geometry

Examples of simple hyperbolic knots and links. (a) Figure-8 knot. (b) Whitehead link.

Image

from article Urodela

A typical member of the order Urodela: the longtail salamander (Eurycea longicauda). (Credit: Ryan Hagerty/U.S. Fish and Wildlife Service)

Image

from article Urodela

Southern dwarf siren (Pseudobranchus axanthus), which has undergone limb degeneration and retains only tiny forelimbs. (Credit: U.S. Geological Survey)

Image

from article Urodela

Image

from article Urodela

California tiger salamander (Ambystoma californiense). (Credit: John Cleckler/U.S. Fish and Wildlife Service)

Image

from article Urodela

The two-toed amphiuma salamander (Amphiuma means). (Credit: Southeast Ecological Center, U.S. Geological Survey)

Image

from article Urodela

The northern red salamander (Pseudotriton ruber ruber) is a member of the family Plethodontidae. (Credit: Alicia Lafever/U.S. National Park Service)

Image

from article Environmental management

Environmental management seeks to provide solutions to the practical problems that humans encounter or create, including the production of garbage and waste. (Credit: Walter Zerla/Getty Images)

Image

from article Environmental management

Without proper environmental management, economic and industrial development often lead to environmental pollution, especially in urban environments. (Credit: Simon Alvinge/123RF)

Image

from article Chicxulub impact crater

Bouguer gravity anomaly map over the Chicxulub impact crater. The coastline is designated by a thin white line, cenotes (natural pits) and sinkholes are designated by black dots, and the city of Mérida and the town of Chicxulub Puerto are designated…

Image

from article Chicxulub impact crater

Seismic line imaging of what lies beneath the seafloor, showing the Chicxulub impact crater. The crater includes many faults that can be grouped into an exterior ring fault, a series of outer ring faults, and a series of inner ring faults. Within…

Image

from article Marine ecology

Marine ecology investigates the basic structural and functional relationships within and among living populations and their physical–chemical environments in marine ecosystems. In this photograph, a cold water reef in California is host to a…

Image

from article Marine ecology

The snaking waterways of a mangrove estuary in northwestern Madagascar. (Credit: Michael Fay/Getty Images/National Geographic RF)

Image

from article Marine ecology

Estuary salt marshes in the Grand Bay National Estuarine Research Reserve, Mississippi. (Credit: P. R. Hoar/National Oceanic and Atmospheric Administration)

Image

from article Marine ecology

Coral bleaching in the lagoon of Huahine Island, French Polynesia. Coral bleaching is the response of corals to environmental stress in which they eject the single-cell algae that live within the transparent coral tissue, making the white coral…

Image

from article Graptolithina

Sketches of portions of pterobranch and graptolite colonies showing the dwelling tubes and the constructional units of the graptolite skeleton. (a) Young Rhabdopleura compacta colony with founder zooid and first asexual bud (Recent). Benthic…

Image

from article Graptolithina

Scanning electron micrograph of a graptolite (Pseudoclimacograptus scharengergi) showing the fuselli (horizontal ridges) that compose graptolite thecae, and the cortical bandages (oblique strips) that were deposited on top of the fuselli (Middle…

Image

from article Graptolithina

Hypothetical form of zooids that inhabited colony tubes, based on a planktic graptolite. Large zooids are shown with possible oarlike swimming organs used to move the colony through the ocean water and tentacles for feeding. Also shown are two…

Image

from article Graptolithina

Examples of some planktic graptolites, reconstructed to show three-dimensional form.

Image

from article Swamp, marsh, and bog

Young cypress trees growing out of a swamp located in the Florida Everglades. (Credit: Getty Images)

Image

from article Plant vulnerability to climate change

Subarctic tundra and vegetation of the Denali National Park and Preserve in Alaska. As a result of climate change and the resultant poleward and upward shift of plant ranges, plants and their ecosystems may become particularly vulnerable. (Credit:…

Image

from article Plant vulnerability to climate change

Blue grama (Bouteloua gracilis) growing in Montana. As a result of warming temperatures, this type of grass could face decreased productivity, allowing forbs to increase and making the ecosystem less tolerant of drought and grazing. (Credit: Matt…

Image

from article Plant vulnerability to climate change

Modeled distribution of suitable climate space in Europe for stiff sedge (Carex bigelowii), which is an Arctic-Alpine plant: (a) during the period 1961–1990 (green color = suitable climate space during the 1961–1990 period); (b) climate model…

Image

from article Plant vulnerability to climate change

The endangered western prairie fringed orchid (Platanthera praeclara) is declining across much of its range in North America. (Credit: U.S. Fish and Wildlife Service)

Image

from article Palaeonisciformes

Mimia toombsi (Gardiner & Bartram, 1977), Late Devonian, Gogo, Australia. One of the earliest palaeonisciforms, reaching 15 cm (6 in.) long, and known by complete fossils. (Reprinted with permission from B. G. Gardiner, The relationships of the…

Image

from article Palaeonisciformes

Chirodus granulosus (Young, 1866) was a deep-bodied palaeonisciform that grew to 10 cm (4 in.) and lived in Carboniferous coal swamps of Britain. The teeth formed cutting blades that may have been used to crop vegetation. This reconstruction is…

Image

from article Biological insect control

The emerald ash borer (Agrilus planipennis) is an invasive pest insect that damages ash tree species in North America and Europe. Researchers are searching for natural enemies against the borer in its native range (Asia) to use as biological control…

Image

from article Cladoselache

Cladoselache fyleri, from the Upper Devonian of Cleveland. (After S. E. Bendix-Algreen, 1975)

Image

from article Paleocopa

Paleocopa. (a) Ogmoopsis nodulifera, left valve; from the Ordovician of Sweden. (b) Eurychilina subradiata, right valve showing wide complete frill; Ordovician of Minnesota. (c) Sulcicuneus porrectinatium, male and female carapaces; Devonian of…

Image

from article Marine conservation

A marine conservation biologist surveying marine invertebrates in a Mediterranean marine protected area in the Gulf of Gökova, Turkey. (Credit: Images & Stories/Alamy Stock Photo)

Image

from article Marine conservation

Bleached Acropora coral in shallow water, French Polynesia. Warming climates have affected marine habitats, with numerous marine species being depleted, threatened, or endangered. (Credit: Seaphotoart/Alamy Stock Photo)

Image

from article Marine conservation

An oil slick off a beach along the South Devon coast of England. Restoration efforts undertaken by marine conservationists attempt to return compromised habitats to ecologically functional, more pristine conditions. (Credit: Richard Packwood/Getty…

Image

from article Social mammals

Meerkats (Suricata suricatta) are notable social mammals. Here, they are looking for danger outside of their den. (Credit: Alta Oosthuizen/Shutterstock)

Image

from article Social mammals

An adult female African lion (Panthera leo) nurses four cubs. The early ingestive behavior (nursing) of mammals has a high degree of social significance. (Credit: Glow Images)

Image

from article Social mammals

Mexican spider monkeys (Ateles geoffroyi vellerosus) are primates that display many examples of social behavior and organization. (Credit: Oksana Kunka/123RF)

Image

from article Circle