Patterns in Nature Topic 12: Heterotrophs Obtaining Nutrients Part of the Patterns in Nature Module Biology in Focus, Preliminary Course

DOT Point Describe the role of teeth in increasing the surface area of complex foods for exposure to digestive chemicals bridlepath.wordpress.com

Heterotrophs Obtaining Nutrients Heterotrophs are living things that must feed on others because they cannot provide their own energy supply by photosynthesis. Obtaining nutrients and energy from food involves several steps: Ingestion: the intake of complex food (eating) Digestion: the breakdown of food into soluable molecules that can easily be absorbed Absorption: Basic units of food absorbed into the bloodstream Assimilation: turning the ‘food’ into tissue Egestion: elimination of wastes We’ll look at Ingestion and Digestion today gly.uga.edu

Teeth and Surface Area Most vertebrates have jaws and teeth that enable them to obtain and process foods. In this section we will mainly be referring to mammals. museumvictoria.com.au

Teeth and Surface Area The digestion of foods involves two stages: Mechanical or physical breakdown, where food is chewed and large chunks are physically broken down into smaller pieces. Chemical breakdown, where digestive enzymes act on the food to chemically break down the large complex molecules into simpler, smaller molecules. gly.uga.edu

Teeth and Surface Area Digestive enzymes function more efficiently if the food to which they are exposed has a large surface area to volume ratio. Large chunks of food are broken down by the teeth which exposes a greater surface area on which the chemicals can act. The volume of food is the same, but the overall surface area to volume ratio is increased. cspinhealthy.blogspot.com

Teeth of mammals There are four main teeth types present in mammals, each with specific functions: Incisors (front teeth): used to grasp, hold and bite food Canines (‘eye’ teeth or ‘fangs’): used for stabbing and gripping prey and for tearing flesh. Premolars (cheek teeth): used for chewing and for cutting flesh and cracking hard body parts such as bones and shells. Molars (back teeth): used for grinding and chewing gly.uga.edu

Teeth of mammals Omnivores (animals that eat both plants and animals) have all four types of teeth. The teeth of herbivores and carnivores differ in their structural detail to best cope with its specialised diet. pitlochry.pkc.sch.uk

Teeth of mammals Herbivores: are heterotrophs that consume plant material. They have front teeth adapted for tearing off vegetation and back teeth adapted to chewing an abrasive, high fibre diet. en.wikibooks.org

Teeth of mammals Herbivores: The incisors are used to bite off vegetation. The molars are broad crushing teeth with relatively large surface areas. The molars are specially equipped with ridges to help break open the cellulose cell walls of plants. In herbivores an enormous amount of chewing is needed. geocities.ws

Teeth of mammals Herbivores: Canine teeth are absent in herbivore jaws, leaving a gap called the diastema, which assists manipulation of food onto the molars, keeping chewed and un-chewed food separate. entomology.cornell.edu

Teeth of mammals Carnivores: Have powerful jaws and well developed canine teeth, conical in shape and specialised for holding and killing prey and tearing meat from the bone. freeimagesarchive.com

Teeth of mammals Carnivores: Meat is torn off in chunks, and many carnivores have molars with deep cusps to briefly chew the meat, increasing the surface area before swallowing it. Some carnivores such as cats have carnassial cheek teeth, adapted for slicing and shearing meat and they have lost their molars. geocities.ws

Teeth of mammals Carnivores: Some carnivores such as insectivores have teeth adapted to piercing and penetrating the tough cuticle of their prey. They puncture and crush the exoskeleton with their premolars and then use these teeth to shear the inner tissues. paleocene-mammals.de

DOT Point Explain the relationship between the length and overall complexity of digestive systems of a vertebrate herbivore and a vertebrate carnivore with respect to: The chemical composition of their diet The functions of the structures involved mindfulnutritionist.wordpress.com

Herbivores Diet: Plant material high in fibre and starch provides the main energy source in the diet of herbivores. This includes sugars, proteins and oils. Cellulose and other cell wall thickenings are difficult to digest and they create a barrier around the cell contents which are capable of being digested. ontariorabbits.org

Herbivores Digestive Tract: Herbivores have adaptations of their digestive tract that enables them to deal with this diet. Most large herbivores rely on microbes in their gut to digest cellulose. phs.d211.org

Herbivores Digestive Tract: To allow for the slow process of microbial fermentation, the gut of these herbivores is complex and very long relative to their body size. An increase in the length provides space to hold large quantities of food and time for microbes to break down the food so it can be absorbed. fstdt.proboards.com

Herbivores Digestive Tract: Small herbivores often eat plant tissue that has much less cell wall material and is energy rich. The gut of these organisms are usually simple and short, in comparison to that of grazers and browsers. The plant tissue in their diet is easier to digest and high in sugar. bio.davidson.edu

Carnivores Diet: Carnivores eat animal matter which is made up of cells, which the content of, is more accessible (no cell wall) and are therefore easier to digest. Animal matter is high in protein, low in fibre and usually has a higher energy content than that of plants. fstdt.proboards.com

Carnivores Diet: So even though the food of carnivores may be more difficult to obtain, it has higher nutritional value and can be consumed in lesser quantities. There is a small amount of fat and very little carbohydrates associated with their diet. bbc.co.uk

Carnivores Digestive Tract: The gut is relatively short and unspecialised, as fat and protein is relatively easy to digest. Very little undigested material is egested, due to the low fibre content of their diet. fl1504073.edublogs.org

Adaptations Adaptations for feeding are thought to be one of the main forces behind the evolutionary process. If an adaptation makes it easier for an organism to obtain food it is to their advantage because competition is reduced. Microbial fermentation is a good example nhptv.org

Homework Students to complete: -DOT Point 3.7 and 3.8 (Prelim Dot Point Text pg 40) **Reminder to hand out Table 3.2 The Digestive System of Humans (Bio in Focus Text pg152)