Wednesday, March 11, 2009

Bacteria and Viruses

Bacteria are single celled prokaryotic organisms. Bacteria have one of three basic shapes: spherical, rodlike or spiral.

When bacteria have plenty of food, the right temperature, and other suitable conditions, they thrive and reproduce frequently.

Bacteria reproduce by binary fission, a process in which one cell divides to form two identical cells. Binary fission is a form of asexual reproduction. Asexual reproduction is a reproductive process that involves only one parent and produces offspring that are identical to the parent. Sexual reproduction involves two parents who combine genetic material to produce a new organism that is different from both parents. Some bacteria perform a simple form of sexual reproduction called conjugation. In conjugation, one bacterium transfers some of its genetic material into another bacterium.

Many bacteria can survie harsh conditions by forming edospores.

Bacteria are involved in oxygen and food production, environmental recycleing and cleanup, and health maintenance and medicine production.

A virus is a tiny, nonliving particle that enters and then reproduces inside a living cell. The organism that a virus enters and multiplies inside is called a host. Viruses are smaller than cells and vary in shape and size.

All viruses have two basic parts: a protein coat that protects the virus and an inner core made of genetic material. After a virus attaches to a host cell, it enters the cell. Once inside a cell, a virus' genetic material takes over many of the cell's functions. It instructs the cell to produce the virus' proteins and gentic material. These proteins and gentic material then assemble into new viruses.

An active virus immediately takes over the cell's functions, and uses them to produce the virus' protein and gentic material. When the host cell is full of new viruses, it bursts open and releases the new viruses.

Biomes and Biodiversity

The six major biomes on Earth are rain forest, desert, grassland, deciduous forest, boreal forest and tundra. It is mostly the climate in an area that determines its biome.

Rain Forests- Tropical rain forests are warm and humid and found near the equator. The abundant plant life in tropical rain forests provides habitats for many species of animals

Deserts- A desert is an area that receives less than 25 centimeters of rain each year. Desert organisms are adapted to lack of rain and extreme temperatures.

Grasslands- Most grasslands receive between 25 and 75 centimeters of rain each year. Grasslands do not get enough rain to support trees.

Deciduous Forests - The trees found in deciduous frests shed their leaves and grow new ones each year. These forests receive at least 50 centimeters of rain each year.

Boreal Forests - Boreal forests contain coniferous trees, which produce their seeds in cones and have leaves shaped like needles. Winters in boreal forests are long, cold, and snowy.

Tundra - The tundra is extremely cold and dry. Most of the soil is frozen all year long.

Aquatic Ecosystems - Freshwater ecosytems include streams, rivers, ponds, and lakes, while oceans, seas, and some marshes make up saltwater ecosytems. An estuary is found where the fresh water of a river meets the salt water of the ocean . Between the highest high-tide lien and the lowest low tide line is the intertidal zone. The aquatic ecosystems are home to more organisms on Earth than any other ecosystem.


From their surroundings, living things obtain food, water, shelter, and other things they need to live, grow and reproduce.

A single organism belongs to a population that includes other memebers of its species. The population belongs to a community of different species. The community and abiotic factors together form an ecosystem.

Every organism has a variety of adaptations that are suited to its specific living conditions.

There are three major types of interactions among organisms: competition, predation, and symbiosis. The three types of symbiotic relationships are mutualism, commensalism, and parasitism.

Each of the organisms in an ecosystem fills the enrgy role of producer, consumer, or decomposer. The moveemnt of energy through an ecossytem can be shown in a diagram called food chains and food webs.

The water, carbon and nirogen cycles are responsible for moving much of the earth's matter continuously through ecosystems. The water cycle is a continuous process by which water moves from Earth's surface to the atmosphere and back. Producers, consumers, and decomposers recycle carbon. In the nitrogen cycle, nitrogen moves from the air to the soil, into living things, and back into the air.