source

Examples of source in the following topics:

• Energy and Nutrient Requirements for Prokaryotes

  • Prokaryotes need a source of energy, a source of carbon, macronutrients, and micronutrients to survive.
  • To live, prokaryotes need a source of energy, a source of carbon, and some additional nutrients.
  • Chemotrophs that can use organic compounds as energy sources are called chemoorganotrophs.
  • Just as prokaryotes can use different sources of energy, they can also utilize different sources of carbon compounds.
  • Table 1 summarizes carbon and energy sources in prokaryotes .

• Protists as Primary Producers, Food Sources, and Symbionts

  • Protists function as sources of food for organisms on land and sea.
  • Protists are essential sources of nutrition for many other organisms.
  • Protists do not only create food sources for sea-dwelling organisms.

• Transportation of Photosynthates in the Phloem

  • Plants need an energy source to grow.
  • Sources are the structures that produce photosynthates for the growing plant.
  • The sugars produced in the sources, such as leaves, must be delivered to growing parts of the plant.
  • The products from the source are usually translocated to the nearest sink through the phloem.
  • Sucrose is actively transported from source cells into companion cells and then into the sieve-tube elements.

• Managing Fisheries

  • Overfishing leads to fishery extinctions, loss of a food source, and affects many other species in ways that may be impossible to predict.
  • For approximately 1 billion people, aquatic resources provide the main source of animal protein.
  • In addition to humans losing the food source, these alterations affect many other species in ways that are difficult or impossible to predict.
  • In addition to humans losing the food source, these alterations affect many other species in ways that are difficult or impossible to predict.
  • In addition to eliminating major food sources, overfishing is a threat to aquatic biodiversity.

• The lac Operon: An Inducer Operon

  • The lac operon is an inducible operon that utilizes lactose as an energy source and is activated when glucose is low and lactose is present.
  • As mentioned previously, E. coli is able to use other sugars as energy sources when glucose concentrations are low.
  • One such sugar source is lactose.
  • The cell can use lactose as an energy source by producing the enzyme b-galactosidase to digest that lactose into glucose and galactose.
  • Transcription of the lac operon is carefully regulated so that its expression only occurs when glucose is limited and lactose is present to serve as an alternative fuel source.

• Strategies for Acquiring Energy

  • Photosynthetic and chemosynthetic organisms are grouped into a category known as autotrophs: organisms capable of synthesizing their own food (more specifically, capable of using inorganic carbon as a carbon source).
  • Photosynthetic autotrophs (photoautotrophs) use sunlight as an energy source, whereas chemosynthetic autotrophs (chemoautotrophs) use inorganic molecules as an energy source.
  • Photoautotrophs, such as plants, algae, and photosynthetic bacteria, serve as the energy source for a majority of the world's ecosystems.
  • Many chemoautotrophs in hydrothermal vents use hydrogen sulfide (H2S), which is released from the vents, as a source of chemical energy.

• Nutrients from Other Sources

  • Some plants cannot produce their own food and must obtain their nutrition from outside sources.
  • This may occur with plants that are parasitic or saprophytic: ingesting and utilizing dead matter as a food source.

• Food Requirements and Essential Nutrients

  • Carbohydrates or sugars are the primary source of organic carbons in the animal body.
  • Protein catabolism provides a source of organic nitrogen.
  • Fatty foods are also significant sources of energy because one gram of fat contains nine calories.
  • Each of these food sources provides different nutrients the body cannot make for itself.
  • Meats are the best source of amino acids, although some amino acids can also be obtained from vegetables and grains.

• Energy Sources

  • The availability of energy and nutrient sources affects species distribution and their adaptation to land or aquatic habitats.

• Freshwater Biomes

  • Rivers and streams are continuously moving bodies of water that carry large amounts of water from the source, or headwater, to a lake or ocean.
  • The origin point of streams (source water) is usually cold, low in nutrients, and clear.
  • Because the source channel is narrow, the current is often faster here than at any other point of the river or stream.
  • As the river or stream flows away from the source, the width of the channel gradually widens and the current slows.
  • The water is as clear as it is near the source since phytoplankton can be suspended in slow-moving water.