Agricultural Ecology

The origins of agriculture can be traced back to Mesopotamia, whence it spread to the fertile crescent of southwestern Asia. In Africa, ancient climatic changes forced humans to make adaptations in their way of life. About 10,000 years ago, as drought and desertification spread from the north into central Africa, nomadic hunter-gatherers began to settle and live by fishing and planting the seeds culled from wild grains in the wet ground left behind by seasonally receding lakes. In the boundary...

Clitellata Oligochaetes and Leeches

Unlike polychaetes, the clitellates exhibit a relatively uniform body plan with homogeneous segmentation. The oligochaetes and leeches are united in this class by the clitellum, a reproductive structure that produces mucous cocoons. Clitellates are hermaphroditic, with single individuals capable of producing sperm and eggs. Development is direct (no tro-chophore larvae) from eggs deposited in cocoons. The subclass Oligochaeta contains more than 6,000 species distributed among at least...

Medicine The Benefits of Biodiversity to

Biodiversity is essential to the maintenance of human health. Extracts from many species of plants and, to a lesser extent, animals are critical to treating infections, disease, and other illnesses. According to the World Health Organization, about 80 percent of people in the developing world still depend primarily on traditional medicine, and 85 percent of that medicine is derived from plants (Farnsworth et al. 1985). Biodiversity plays a central role in Western medicine also 57 percent of the...

Positive Interactions

Positive interactions are cooperative relationships between species that result in better growth, reproduction, and survival for at least one species involved in the interaction, without negatively affecting the other species (Morin, 1999 Stiling, 1999). Positive interactions influence biodiversity by creating alliances between species that allow them to coexist. The benefits of these associations are numerous. They include the provision of food, habitat, and more specialized services such as...

Preservation of Species

The conservation of species involves the use of strategies and techniques that can be classified into three broad approaches in the wild, in captivity, and in-vitro (germ cells). Knowledge of these approaches is essential to understanding how conservation management practices conserve biodiversity in real life applications. In the wild, or in-situ, conservation is defined by the Convention for Biological Diversity (1992) as the conservation of ecosystems and natural habitats and the maintenance...

Topsoil Formation

Topsoil is the upper layer of the soil profile. It is composed of minerals and rock particles, humus, dead and decaying organic matter, water, and an array of living creatures. The kinds of animals are specific to the location, but in general they include rodents, earthworms, insects, fungi, bacteria, protozoans, and viruses. It is these life forms that digest and decompose the organic matter by feeding on their dead and dying tissues, creating humus. These organisms leave their waste behind as...

Topsoil Loss of

When soil is exposed, it is removed by wind and rain. For example, rain pounding on the surface of soil breaks it apart, making it easy for running water to carry it away. At first, erosion may be sheets of water running down a slope. However, as time goes on, flowing water may become concentrated in tiny channels, or rills. With time these may enlarge to gullies, making the fields unusable because equipment can't get around. As the gullies enlarge and widen by lateral erosion, the stream banks...

What You Can DoChange Your Energy

The amount of energy we use and the ways we use it affect earth's biodiversity in every corner of the globe. As we burn fossil fuels to generate electricity, run our cars, and heat our homes, we release gases that contribute to global climate change, acid rain, and air and soil pollution. Ultimately, our reliance on fossil fuels is leading to a less habitable planet for ourselves and other species. By using energy more wisely and transitioning to cleaner, renewable energy sources, we promote a...

Haplochromine Cichlids of Lake Victoria

The haplochromine cichlid fish of Lake Victoria demonstrate both the exuberance of species radiation and the tragedy of mass extinction, the first to occur during historical times. These tiny, colorful fish, which constituted 80 percent of the fish biomass in Lake Victoria prior to 1978, now account for less than 2 percent (Kaufman, 1992). This decline has been caused by a combination of human influences. The cichlids are a very large and diverse family of freshwater, perchlike fish...