Adaptations for Nutrition
BY2 Biology
Nutrition
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The process organisms use to get
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energy to maintain life functions and
matter to build and maintain their structure (from nutrients)
Types of Nutrition
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Autotrophs - use simple inorganic materials to
manufacture complex organic compounds (also
called producers)
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Ex: photosynthesis - plants use carbon dioxide,
water and light energy to make sugars
Ex: chemosynthesis - bacteria around deep sea
vents-use carbon dioxide and sulphur compounds
(as energy) to create organic compounds
Heterotrophs - consume complex organic
food material (also called consumers)
What do heterotrophs need to live?
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They make energy using:
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Food (organic compounds such as carbohydrates,
protein..)
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Oxygen
food
They build bodies using:
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food for raw materials
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amino acids, sugars,
fats, nucleotides
ATP
O2
ATP energy for synthesis
This includes animals, fungi, some protoctists and some bacteria
Overview of food processing
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Ingest
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taking in food
Digest
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mechanical digestion
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chemical digestion
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intracellular
digestion
Digested food moves across cell membrane
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diffusion
active transport
Assimilate
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breaking down food into soluble molecules small
enough to be absorbed into cells
uses enzymes (hydrolysis)
Absorb
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breaking up food into smaller pieces
use compounds in the body
Egestion
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undigested extracellular material passes out of
digestive system (ex: cellulose in humans)
extracellular
digestion
Types of Heterotrophic Nutrition
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Holozoic feeders:
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Take food into their bodies and break is down during digestion
Have specialised organs in a digestive system (gut)
After digestion, the nutrients are absorbed into the body
Saprophytes (saprobionts):
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Fungi and some bacteria
Feed on dead or decaying matter
No specialised digestive system
Secrete enzymes onto the food source outside their body for extracellular digestion and absorb the soluble products by diffusion
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(enzymes include protease, amylase, lipase, cellulase)
Some are decomposers and help to recycle nutrients in the
ecosystem
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Parasites:
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Highly specialised organisms
Feed on other living organisms (a host)
Some live inside the host (endoparasites) other live on the
outside (ectoparasites)
The host is always harmed
Ex: tapeworm, potato blight (fungus), plasmodium (causes
malaria)
Mutualism (symbiosis):
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2 different species live in a helpful relationship
Ex: cows use bacteria in their stomach to help digest cellulose
and the bacteria gain nutrients from the broken plant material
for growth and energy
How do animals get their food?
filter (suspension) feeding
fluid feeding
substrate feeding
bulk feeding
Food types/feeding mechanisms
Heterotrophs
Opportunistic
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Herbivore: eat autotrophs
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Carnivore: eat other animals
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Omnivore: both
Feeding Adaptations
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Suspension feeders - sift food from
water (baleen whale)
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Substrate feeders -live in or on their
food (leaf miner) (earthworm:
deposit-feeder)
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Fluid-feeders -suck fluids from a
host (mosquito)
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Bulk-feeders: eat large pieces of food
(most animals)
Digestive systems
Simple More complex
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In simple organisms:
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feeding on only one type of food
the gut is undifferentiated
In more advanced organisms:
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Often have a varied diet,
the gut is divided into various parts along its length and each
part is specialised to carry out particular functions
Organisms with a varied diet require more than one type of
enzyme to carry out the digestion of the different food substrates
Human Digestive System
Overview animation
Mouth (buccal cavity)
mechanical digestion by teeth to
break up food
(mastication/chewing)
moistens food by mixing with
saliva to lubricate it for swallowing
chemical digestion - amylase
digests starch
saliva
Contains:
• water (to soften food)
•mucus (to protect the lining of the
digestive system)
•amylase (breaks starch to
maltose)
•mineral ions to keep mouth pH
alkaline (act as a buffer)
•Anti-bacterial chemicals to kill
germs
Swallowing (& not choking)
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Epiglottis
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problem: breathe & swallow through same orifice
flap of cartilage
closes trachea (windpipe) when swallowing
food travels down esophagus
Esophagus
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move food along to stomach by peristalsis
stomach
acid (secreted from oxyntic cells in wall) kills germs
stores food for up to 4 hrs (sphincter at each end)
mixes food by moving wall with contractions (churning)
gastric juice secreted from glands (peptic cells) in stomach wall
digest proteins
secretes mucus (from goblet cells) to protect stomach lining from
acid and enzymes
Gastric juice
Contains:
•Acid (pH =2) kills germs
and provide optimum pH
for pepsin
•Peptidase enzymes (ex:
pepsin) to hydrolyse
protein to polypetides
cardiac
sphincter
pyloric
sphincter
Human Digestion
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Peristalsis: rhythmic waves of contraction by smooth muscle
Sphincters: ring-like valves that regulate passage of material
Accessory glands: salivary glands; pancreas; liver; gall bladder
(secrete digestive juices)
Tissue Layers
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The gut wall consists of four tissue layers surrounding
a central cavity (lumen)
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Serosa – tough connective tissue to protect the wall and
reduce friction with other organs when it moves)
Muscle Layer – longitudinal muscle and circular muscle
running in different directions
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Cause peristalsis when circular muscles contract and longitudinal relax)
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Submucosa – connective tissue with blood vessels and
lymph vessels to carry away absorbed food
 Has nerves to coordinate peristalsis
Mucosa- secretes music to lubricate and protect the
mucosa
 Secretes digestive juices in some areas
 Absorbs digested food in others
Glands
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There are a number of different glands which produce
digestive secretions:
 Some are found in the wall of the gut with the secretions passing
directly into the gut cavity
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Mucus secreting glands (submucosa)
Gastric glands (mucosa)
Glands at base of villi (mucosa)
Others are found outside the gut with the secretions
passing along ducts into the gut cavity
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Salivary
Pancreas
Liver
The human alimentary canal
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Consists of:
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buccal cavity
Tongue
Salivary glands
Oesophagus
Stomach
Duodenum
Ileum
Colon
Rectum
Anus
associated organs; liver and pancreas
Small intestine
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Function
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major organ of digestion & absorption
chemical digestion
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absorption through lining
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digestive enzymes
over 6 meters!
small intestine has huge surface area = 300m2 (~size of tennis court)
Structure
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3 sections
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duodenum = most digestion
jejunum = absorption of nutrients & water
ileum = absorption of nutrients & water
Duodenum
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1st section of small intestine
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acid food from stomach mixes with digestive juices from
accessory glands:
 Liver
 gall bladder
 pancreas
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Glands in wall also
secrete: alkaline juice
(optimum for enzymes)
and mucus (lubrication
and protection)
Duodenum
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Enzymes on the tip of the villi complete digestion:
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Maltase
Endopepsidase
Exopepsidase
Liver
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Digestive System Functions
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produces bile salts
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stored in gallbladder until needed
Help neutralise stomach acid
breaks up fats by lowering the surface tension of lipids
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act like detergents to breakup fats into tiny droplets (emulsifier)
Circulatory System
Connection
bile contains colors from
old red blood cells
collected in liver =
iron in RBC rusts &
makes feces brown
Pancreas
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Secretes pancreatic juice via pancreatic
duct
Digestive enzymes
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Endopeptidases (protein peptides)
Pancreatic amylase (starch  maltose)
Lipase (lipids  fatty acids + glycerol)
Buffers
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reduces acidity
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alkaline solution rich in bicarbonate (HCO3-)
buffers acidity of material from stomach
Absorption by Small Intestines
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Adaptations for absorption
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Very long
Highly folded for higher surface area
Folds contain finger-like villi
Villi contain microvilli
Absorption by Small Intestines
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Absorption through villi & microvilli
 Glucose and amino acids are absorbed by diffusion and
active transport into capillaries and then travel via the hepatic
portal vein to the liver.
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There are lots of mitochondria present in these cells
Fatty acids and glycerol are passed into the lacteal, then
through the then through the lymphatic system to the blood
stream opening at the thoracic duct.
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A longitudinal section through a villus - you can see the
'brush border' created by the microvilli, the arrow points
to mucus in a goblet cell
mouth
break up food
moisten food
digest starch
kill germs
liver
produces bile
- stored in gall bladder
break up fats
pancreas
produces enzymes to
digest proteins & starch
stomach
kills germs
break up food
digest proteins
store food
small intestines
breakdown all foods
- proteins
- starch
- fats
- nucleic acids
absorb nutrients
Large intestine
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4 parts:
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Caecum
Appendix
Colon
Rectum
Function
 re-absorb water and mineral salts in colon
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use ~9 liters of water every day in digestive juices
> 90% of water reabsorbed
not enough water absorbed
back to body
 diarrhea
 too much water absorbed back to body
 constipation

Flora of the large intestine
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Living in the large intestine is a rich
flora of harmless, helpful bacteria
 Escherichia coli (E. coli)
 bacteria produce vitamins
 vitamin K, folic acid & other B vitamins
 generate gases
 by-product of bacterial
metabolism
 methane, hydrogen sulfide
Rectum
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Last section of large intestine
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eliminate faeces
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undigested materials
 mainly
cellulose from plants (roughage or fiber)
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Salts
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extracellular waste
Cellulose fibre is required to provide bulk and
stimulate peristalsis.
cells that have sloughed off
 masses of bacteria
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mouth
break up food
moisten food
digest starch
kill germs
liver
produces bile
- stored in gall bladder
break up fats
pancreas
produces enzymes to
digest proteins & carbs
stomach
kills germs
break up food
digest proteins
store food
small intestines
breakdown food
- proteins
- starch
- fats
absorb nutrients
large intestines
absorb water
Summary of enzymes
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Called hydrolases as they catalyse the
hydrolysis of molecules
Enzyme group
Enzyme
Location
Substrate
Products
Other
Carbohydrases
Amylase
Mouth
Duodenum
Pancreas
Starch
Maltose
Maltose is further broken down
Maltase
Duodenum
Maltose
Glucose
Glucose used as an energy source in
respiration
Excess glucose is converted to fat
Proteases
Peptidase
(ex: pepsin)
Stomach
Duodenum
Pancreas
Polypeptides
then amino
acids
Amino
acids
Endopeptidases hydrolyse peptide bonds
within the protein
Exopeptidases hydrolyse peptide bonds
near the end of proteins
Amino acids are absorbed for protein
synthesis
Excess amino acids cannot be stored so
is deaminated, whereby the removed amino
groups are converted to urea and
the deaminated remainder is converted to
carbohydrate and stored
lipase
Lipase
Pancreas
Fats
Fatty acids
& glycerol
Lipids are used for membranes and
hormones, and the excess is stored as
fat.
Review
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digestive system in humans
Overview animation
Evolutionary adaptations to different diets
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Adaptations of herbivore vs. carnivore
 specialization in teeth
 length of digestive system
 number & size of stomachs
Evolutionary adaptations to different diets
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Animals have different diets and methods of feeding.
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Ex: Retiles and amphibians-swallow food whole immediately so no
need for teeth for chewing
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Mammals cut and chew food before swallowing and so have
adapted different types of teeth
Dentition
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Mechanical digestion (cutting and chewing food)
increases surface area for enzyme action and make
swallowing easier
Mammals have evolved different types of teeth with each
type being specialised for a different function
Teeth
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There are differences
between the teeth of
carnivores and herbivores
reflecting their differing diets
Carnivore teeth
Adapted for:
 Catching/piercing skin & killing – large, curved pointed
canines
 Crushing bones – premolars and molars
 Tearing meat – canines
 Scrape meat off the bone - incisors
 Carnassials – specialized molars (cheek teeth) that slide past
each other like scissors to cut and crush
Jaw
 Powerful with strong muscles
 Does not move side to side (to prevent dislocation)
 Greater vertical movement to open wide to capture prey
Herbivore Teeth
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Must grind plant material
(due to cellulose) before swallowing
Adapted for:
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Cutting plants - Incisors on the lower jaw only and a horny
pad on the upper jaw to cut against or help to pull grass (no
canines).
Grinding - wide molars and premolars (cheek teeth) that
interlock/fit into each other. These teeth get worn down but can
regrow throughout life
Jaw:
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Diastema – gap between front teeth and premolars at side
where the tongue can push the cut grass to the grinding surface
at the back and push food to the back over again and again
Moves in a circular grinding action on the horizontal plane
Omnivore Teeth
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both kinds of teeth
Example: 32 Human teeth (adult)
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8 incisors (chisel shape) for biting and cutting
4 canines (pointed) for tearing
8 premolars
12 molars (flat) for grinding
Length of digestive system
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Carnivores
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No need to digest cellulose
or starch so less chemical
digestion in mouth
More acid in stomach (so can
often eat rancid food)
short digestive system
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protein easier to digest than
cellulose
Herbivores & omnivores
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long digestive system
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more time to digest cellulose
symbiotic bacteria in gut
Symbiotic organisms
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How can cows digest cellulose efficiently?
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symbiotic bacteria in stomachs help digest cellulose-rich meals
rabbit vs. cow adaptation: eat feces vs. chew cud
Ruminants
additional
mechanical digestion
by chewing food
multiple times after
mixing it with
enzymes
caprophagy
ruminant
Ruminants (ex: cows and sheep)
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Eat mainly grass, a large proportion of which consists of
cellulose cell walls
Have a 4 chambered stomach
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Process:
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Food chewed and mixed with saliva
Then passed to the rumen (first stomach) in which
mutualistic bacteria live and break down cellulose to
glucose (since ruminants do not have the enzyme cellulase)
Glucose is fermented to an organic acid and absorbed into
the blood for energy. Waste gases include carbon dioxide and
methane
Ruminants
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plant material is passed up from the rumen and reticulum back into
the mouth periodically until it is completely chewed up (known as
chewing the cud).
Material is then passed from the rumen and reticulum (no real
function) into the omasum (next chamber) where water is
absorbed
Then it is passes to the abomason (last chamber) where
hydrochloric acid and protease digest protein
Then the material continues into the small intestine for absorption
of products
The Bacteria
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Mutualistic - both benefit – mammals gets food broken
down further and bacteria gets food supply brought to it and
shelter
bacteria must be kept in an isolated area with optimum pH
(not killed by pH in other parts of gut)
More bacteria than in caecum, so more efficient at breaking
down cellulose
When bacteria die they get passed along the digestive system
as a source or protein
Rabbits
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Coprophagy is consumption of faeces by
animals.
Rabbits do not have a complex ruminant
digestive system.
They must extract excess amount of
nutrition from grass by giving their food a
second pass through the gut.
Soft fecal pellets or partially digested food
are excreted and consumed immediately
Consuming this matter is important for
adequate nutritional intake of vitamin B 12.
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http://www.bozemanscience.com/digestive-system