Heterotrophs

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Heterotrophs

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

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Heterotrophs

• All animals
• All fungi
• Some bacteria

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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

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

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Example of passive feeding techniques

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

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Example of active feeding technique

• Lion hunting prey

• Humans fishing

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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

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Directly dependent

• Cow (heterotroph) eats grass (autotroph)

• Fungi (heterotroph) consume organic material such
  as carbon found in logs (autotroph)

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Indirectly dependent

• Cow (heterotroph) eats grass (autotroph)
• Other animals (heterotrophs) eat cow (heterotroph)

OR
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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

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Exchanges between cultures
Boiling water Killed organisms

• Tea and coffee (1800s)
• Sugar
• White flour
• Changes in Australian diet from aboriginal to
  European to multicultural

Tooth decay
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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.

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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

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1. Ingestion of food

• Occurs when a food source in the environment is
  captured and taken into an animals mouth
• EATING!

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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
  SAV
• SAV ratio identifies how many units of external
  surface area are available to supply each unit
  of internal volume.
• As a shape decreases in size, SAV 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)

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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

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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

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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

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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

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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

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Parts of the tooth
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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

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Crackers!
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Next lesson

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