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Modes of Nutrition - A Level biology revision notes.
Definitions
Nutrition - Taking Nutrients from the environment
Nutrients - Substances that are needed for
- Sources of chemical potential energy (ATP)
- Sources of molecules and atomy when are used for building up cells
Inorganic Nutrients - An inorganic substance in which the molecules of ions are relatively small and which does not contain carbon. E.g. H2O, O2, CO2 and nitrate ions.
Organic Nutrients – In an organic substance the molecules are usually relatively large and contain carbon. E.g. carbohydrates, fats and protein
Types of nutrition
Different types of organism will use different types of nutrition. There are two types of nutrition used.
Autotrophic
- The use of inorganic nutrients
- Carried out by all plants, algae and some bacteria
- Organisms which use this type of nutrition are known as AUTOTROPHS
- They need an energy source which is usually the sun but can be chemical energy
Heterotrophic
- The use of a mixture of organic and inorganic nutrients
- Organisms which use this form o nutrition are know as HETEROTROPH
Holozoic Nutrition
This is a form of heterotrophic nutrition when the nutrients that are taken into the body are passed down some form of alimentary canal. Holozoic organisms can be divided into two groups herbivores and carnivores.
Herbivores
- Feed only on plant material
- They need to break down the β1,4 glycocidic bonds in cellulose from the cell wall to gain the nutrients that they need. To do this they use the enzyme cellulase.
- Their gut has to be designed to break down cellulose. These organisms are called ruminants.
Adaptations Ruminants have
- The teeth of ruminants are very well adapted. The molars and premolars are large and broad; they have ridges and groves on the surface. The ridges and groves fit into each other. The lower jaw moves from side to side this crushes the food and increase the surface area for digestion. These is a space between the molars and the incisors this gap is called the DIASTEMA and is used to manipulate the food to be chewed over and over again. The upper jaw is a hard tough pad and the grass is cut between the teeth and the pad.
- The stomach of ruminants have four chambers. The reticulum which has no digestive function. The rumen is where fermentation with micro-organism occurs. The omasum removes water and organic acids and finally the abomasums which is also known as the true stomach and secretes enzymes.
Carnivores
- Feed entirely on the bodies of animals most carnivores are predators but some are scavengers.
Adaptations carnivores have
- Large pointed canine teeth which enables them to pierce the skin of and kill their prey.
- Their incisors are small that that of a ruminant and are used for nibbling meat of the bone.
- Their molars and premolars are sharp and act like scissor blades
- Their jaws move up and down and not side to side they bite, cut and swallow food quickly so that another animal doesn’t take it.
Saprobiontic Nutrition
- Organisms that use this type of nutrition are know as saprobionts
- They don’t invade living tissue
- They feed on dead or rotting matter
- They secrete digestive enzymes directly onto the food this called extracellular digestion and occurs outside the cell. They then reabsorb the digested products back into their cells.
- These organisms are involved in decomposing and decay. They are really important in the recycling of nutrients.
Mutulistic Nutrition
- These organisms are involved in symbiotic relationships
- An example is the bacteria Rhizobium with legumes
- The bacteria are nitrogen fixing, they convert nitrogen and hydrogen to ammonia.
- They are found in the soil and in the root nodules of legumes.
- The plants use the ammonia produced by the bacteria is used by the plants to make amino acids.
- The bacteria benefits from this relationship because they gain carbohydrate and ATP from the plant.
- The plant benefits because the ammonia produced by the bacteria allows them to flourish in nitrogen deficient soil.
Parasitic Nutrition
- This is a relationship between parasite and host. The parasite is dependent on the host for nutrition and protection. The parasite will generally do the host harm.
- Parasites are highly adapted for this type of nutrition. There are two main types of parasite ectoparasites which lived outside the organism and endoparasites which live inside the organism.
Comments
Orginally written from class notes by randdom.
