palaeoecology Palaeoecology is the study of the interactions of organisms with each other and with their environment in the geological past. It thus borrows heavily from the modern discipline of ecology although its emphases are different. Modern biologists can sample populations on scales of years and describe environments in detail, while palaeontologists are limited by the data they can collect and generally work on timescales of thousands or millions of years. Despite these restrictions, palaeoecology is important because of its value in helping to reconstruct ancient environments and in understanding fossils as once-living organisms.

The ecosystem is the largest unit of ecological study and consists of a portion of the physical environment, however large or small, together with all the organisms it contains. Within this the habitat is the environment in which the organism lives; its niche is its position in the habitat, including its relationship with other organisms. Study may be at the level of the individual or encompass populations of two or more individuals or communities of two or more species. Modern organisms are grouped according to the role they play in the flow of energy through the ecosystem. Primary producers such as plants convert nutrients and light into organic compounds, which are then consumed by herbivores. In their turn the herbivores are eaten by carnivores or by scavengers and, eventually, all organisms are broken down by bacteria into nutrients that return to the environment.

In order to study the ecology of fossil organisms, palaeoecological inference is used extensively. This uniformitarian approach is based on the assumption that the general laws governing the functioning of organisms have not changed with time. Producers, herbivores, carnivores, and decomposers were present in the past, and although the complexity of ecosystems has increased, the laws governing the flow of energy through them are assumed not to have changed. Some interactions, particularly predator–prey relationships, are independent of inference from modern communities; thus, for example, teeth marks in an ammonite show that it was bitten by a mosasaur. Other relationships require more inference, as in the study of ancient reefs. Modern reefs consist mostly of corals that live in symbiotic relationship (in which both gain an advantage) with algae. The algae need sunlight to photosynthesize and the corals provide the framework to hold them near the surface. Similar reefs can be seen in Cenozoic and Mesozoic rocks and a similar relationship can be inferred.

The functions of various features in fossils can also be inferred by comparison with modern organisms; in many instances, however, these features may be unknown in modern taxa. In order to interpret these so that an understanding of adaptation and mode of life can be developed a coherent methodology such as the paradigm approach is used. In this system optimum structural designs for all possible functions of the feature are developed and the design that appears most similar is considered most likely to be correct.

Other areas of palaeontology are important in the study of palaeoecology. Taphonomy deals with the processes that affect an organism from death to burial, and is necessary for an understanding of the extent to which the preserved organisms accurately reflect the living communities. Ichnology deals with tracks and trace fossils and therefore provides evidence of the soft-bodied members of communities that otherwise leave no record.

David K. Elliott

Paleoecology

Paleoecology is the study of fossil organisms and their relationship to ancient environments. Paleoecology falls under the broader category of paleontology (the study of fossils). A person who studies and investigates paleoecology is called a paleoecologist. The study of paleoecology is important to scientists because it reveals so much about such natural aspects of ancient history as wind conditions, climates, temperatures, and ocean activity. Critical to the field of paleoecology is the intense concentration of chemicals found in fossils; such chemical data reveals much information about the world of long, long ago.

The field of paleoecology was developed by American geologist (a person who studies the history of Earth) Kirk Bryan (1888–1950). Bryan focused his investigations on weather changes from the past by using information from ancient soils and pollen. His work gathered enough interest from the scientific community to help develop the field of paleoecology.

Paleoecologists can find clues about the ancient environment and the organisms that lived during a particular time on Earth by examining fossil organisms, the different varieties of those fossils, and the sediment in which they were found. Sediment is made up of rock particles, minerals, and fossil organisms that, due to the forces of weather and time, have deposited on top of each other, forming layers. These layers compress and harden, forming sedimentary rock.

Sediment also collects at the bottom of an estuary (area of water where the sea meets a river). Each layer of sediment represents a piece of time in history. Paleoecologists take core samples of the sediment—by pushing a tube down into the estuary and pulling out a sample of the muddy bottom—that provide a historical record of the past. Material found closest to the top of the tube is the youngest sediment; material near the bottom of the tube sample is the oldest. (The idea of sediment layers is similar to that of tree rings, which reveal the age of a tree.)

For example, marine (sea-dwelling) fossils have a significant accumulation of chemicals in their skeletons. By studying these chemicals, paleoecologists can draw conclusions about what was happening in the environment and what was living in the areas surrounding oceans. Because

of what is recorded in fossils found in water environments, paleoecologists most frequently study these types of fossils.

Words to Know

Fossils: The remains, traces, or impressions of living organisms that inhabited Earth more than ten thousand years ago.

Paleontology: The scientific study of the life of past geological periods as known from fossil remains.

Sediment: Sand, silt, clay, rock, gravel, mud, or other matter that has been transported by flowing water.

Sedimentary rock: Rock formed from compressed and solidified layers of organic or inorganic matter.

[See also Fossil and fossilization; Paleontology ]

palaeoecology The study of the relationships of fossil organisms to each other and to their environments. It involves the study both of the fossils and of the surrounding rocks in which they are found. Trace fossils may provide information on the behaviour of the organism.

palaeoecology The application of ecological concepts to fossil and sedimentary evidence in order to study the interactions of the Earth's surface, atmosphere, and biosphere in pre-historic and geologic times.

palaeoecology The application of ecological concepts to fossil and sedimentary evidence to study the interactions of Earth surface, atmosphere, and biosphere in former (prehistoric) times.

palaeoecology The application or ecological concepts to fossil and sedimentary evidence to study the interactions of Earth surface, atmosphere, and biosphere in former (prehistoric) times.

palaeoecology The application of ecological concepts to fossil and sedimentary evidence to study the interactions of Earth surface, atmosphere, and biosphere in former times.