Heterotrophs Food for heterotrophs Changes in food through time What animals need for digestion Mechanical breakdown of food

Heterotrophs All animals All fungi Some bacteria

Heterotrophs Heterotrophs obtain energy for living and material for building and repairing their structure from organic matter in their surroundings Heterotrophs are therefore consumers Organic matter used by heterotroph is its food

Each heterotroph has structural and physiological features, and displays behaviours, that assist it in obtaining food Feeding techniques may be active or passive

Example of passive feeding techniques Whale sharks- swimming with large mouth open, consuming krill and large quantities of water which is then filtered.

Example of active feeding technique Lion hunting preyHumans fishing

Heterotrophs as consumers Heterotrophs are either directly or indirectly dependent on organic compounds produced by autotrophs Unlike autotrophs, they cannot survive on inorganic matter For organic material to become food for a heterotroph, it must be able to be broken down and used by the heterotroph to supply it with the chemical energy for living and repairing its own structure

Directly dependent Cow (heterotroph) eats grass (autotroph) Fungi (heterotroph) consume organic material such as carbon found in logs (autotroph)

Indirectly dependent Cow (heterotroph) eats grass (autotroph) Other animals (heterotrophs) eat cow (heterotroph) OR

Food changes through time The production and use of food is basic to human survival and an integral part of our culture. Major events impacting the food we eat –Discovery of fire –Growing our own crops –Domesticating animals –Exploration and trade with other cultures

Exchanges between cultures Tea and coffee (1800s) Sugar White flour Changes in Australian diet from aboriginal to European to multicultural Tooth decay Boiling water Killed organisms

What animals need for digestion Digestion – first step after food is eaten enabling heterotrophs to access the nutrients and energy in it Some nutrients in food (minerals, vitamins) will dissolve and readily enter cells. Other nutrients (fats, proteins) are too large to pass through cell membranes. These larger nutrients must be broken down into smaller units to allow absorption. Digestion is the chemical process of breaking down large organic molecules to a size that can be absorbed.

Four steps before a substance becomes available to cells of an animal 1.Ingestion of food 2.Mechanical breakdown of the ingested food 3.Secretion of various digestive enzymes onto the food 4.Absorption of digested food

1. Ingestion of food Occurs when a food source in the environment is captured and taken into an animal’s mouth EATING!

2. Mechanical breakdown of the ingested food Large pieces of food being broken down into smaller pieces This is to do with surface area to volume ratio SA:V SA:V ratio identifies how many units of external surface area are available to ‘supply’ each unit of internal volume. As a shape decreases in size, SA:V ratio increases As food is broken down into smaller and smaller pieces, although total volume of food stays the same, total area of food exposed to enzymes increases (faster digestion)

3. Secretion of various digestive enzymes onto the food Digestive enzymes catalyse (speeds up) the breakdown of organic molecules into smaller units that can cross cell membranes This breakdown of complex organic molecules is digestion After this has occurred, the energy and matter contained in the organic molecules become available for use by the animal

4. Absorption of digested food The organic molecules (now small enough) pass through membranes of cells lining the digestive tract and then pass into body fluids Different animals eat different kinds of food The way in which an animal digests food depends on which kinds of food it eats

Mechanical breakdown of food As mentioned, food is broken down to provide the largest possible surface area for enzyme action After it is broken down, food is mixed with digestive enzymes In animals (like us), jaws and teeth play an important role in this process

Jaws and teeth The jaws surround the mouth and are opened and closed by muscles Teeth are hard bony appendages found on the jaws on many animals Movement of toothed jaws breaks food into pieces YOU ALL KNOW THIS! YOU DO IT ALL THE TIME! Most living vertebrates also do this

Different kinds of teeth Four different types found in most mammals 1. Incisors- sharp endges, cut food, get food into mouth 2. Canines – are pointed, pierce and tear food 3. Premolars – have rigid surgaces to grind the food so it is easy to swallow 4. Molars – same as premolars These are in order from the front of the jaw to the back

Parts of the tooth

Differences between animals Most mammals have different kinds of teeth Some mammals (dolphins) have teeth that all have the same structure designed for eating fish (they do not chew) Carnivorous mammals- eat meat, use teeth an jaws to chew their food Herbivores- eat fruit, leaves, grass. They do not have canine teeth Omnivores- eat both plant and animal material and so have characteristics of both types Diagram showing the difference, text book P.106

Crackers!

Next lesson What happens after the food is broken down and ready for digestion?