• Describe how nutrients and digestion provide materials for energy and growth.
  • List the six nutrients required by heterotrophs.
  • Describe how plants use nutrients.
  • Describe three feeding types.

Describe the tube concept as it applies to nutrition.


All organisms must have a way of obtaining essential nutrients
Essential nutrients are basic raw materials for creating structures, perform life functions, and provide energy
Organisms that produce their own food are called autotrophs
Autotrophs include clorophyll-containing plants, bacteria, and protists as well as chemosynthetic bacteria
Organisms that rely on other organisms for food are called heterotrophs
Heterotrophs include animals, fungi, and some plants, bacteria, and protists
Nutrients must be in a form that can readily pass through the organism's cell membranes
Many organisms produce digestive enzymes that reduce food to a form from which nutrients can be absorbed

How Green Plants Use NutrientsEdit

Green plants need only minerals to survive, not preformed organic molecules
There is no need for a digestive system, minerals are absorbed from the soil
Green plants can make use of the elements of carbohydrates or amino acids if available
Pitcher plant and Venus flytrap are insect-eating plants which also have clorophyll-containing leaves so can photosynthesize
These plants live in bogs where the water is acidic and low in nitrogen compounds
Insects are high in protein and thus rich in nitrogen-containing amino acids

Feeding Devices and BehavioursEdit

Heterotrophs require various ways of finding and seizing food as well as bringing food into their digestive systems

Filter FeedingEdit

Move water through a straining device which holds food behind while allowing water to pass
Whales, clams, oysters, mussels, scallops, and other shellfish, as well as some ducks use filter feeding to filter food from their surroundings

Fluid FeedingEdit

Involves piercing and sucking fluid from plants and animals
Mosquitoes and leeches feed on blood and use anti-coagulants to stop the blood from clotting while they feed
Tape worms attaches itself to the intestinal lining of a host animal and absorbs nutrient-rich fluids from its host's digestive tract

Other Devices and BehavioursEdit

Many insects and most vertebrates ingest large quantities of food at a time and do not need to feed continuously
Some examples of gathering/feeding devices used are an elephant's trunk, the lips and tongue of a cow, and human hands

Digestion: Essential Food ProcessingEdit

In single-celled organisms food is taken in by pinocytosis but must still be acted upon by enzymes in order for the organism to use the nutrients
Larger organisms such as fish, frogs, birds, and mammals food is broken down and transported to cells by the digestive and circulatory systems
Digestive system breaks food down into substances that can be absorbed by circulatory system
Nutrients are transported to cells and again absorbed
Processes and structures involved in digestion: digestive tract, movement of food through the tract, chemical digestion of food, organs such as the liver, pancreas, and call bladder, and the roles of nutrients, diet, and health

The Tube ArrangementEdit

The tube enables digestion to be carried out in small isolated portions of an organism's internal environment
In open tube arrangement animal has an intake (mouth) at one end and outlet (anus) at the other end
Food proceeds along tube and is digested along the way
In closed tube arrangement a single opening allows entry of food and exit of wastes
digestive enzymes may enter the tube at one area (invertebrates) or at many points along its length (vertebrates)

Intracellular DigestionEdit

Protists generally do not have tubes though some like the paramecium have the beginning of one
Amoeba engulf food particles by phagocytosis
in both cases food is enclosed in a vacuole into which digestive enzymes are secreted
As the vacuole follows a path through cytoplasm it shrinks as water and products of digestion leave it
Finally vacuole reaches cell boundary (often at particular point) where indigestible residue is expelled and the vacuole disintegrates
Intracellular digestion occurs in some other organisms such as clams and sea anemones along with extracellular digestion
Extracellular digestion is more common among animals