Adaptations for
nutrition
BY2
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Types of nutrition
Nutrition is the process by which organisms obtain energy to maintain life
functions and matter to create and maintain structure. There are various
ways in which this can be done:
Autotrophic nutrition
Autotrophic organisms utilise an energy source to make their own
organic molecules from simple inorganic molecules e.g. green plants,
algae and some bacteria carry out photosynthesis to make organic
glucose from the inorganic molecules ………….. ……………… and ……………….,
using energy from the ………………
Some bacteria synthesise organic compounds using energy derived from
…………………………..….. reactions e.g. bacteria respiring at deep sea
hydrothermal vents. This is known as chemosynthesis.
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Heterotrophic nutrition
Heterotrophic organisms consume complex organic food material and break it down into
smaller, soluble molecules which they then absorb and assimilate.
Heterotrophs include animals, fungi, some protoctista and some bacteria.
There are several different types of heterotrophic nutrition:
1. Holozoic feeders – these organisms have specialised digestive systems
Carnivores –
Herbivore –
Omnivores –
Detritivores -
2. Saprophytes (or saprobionts) feed on …..…….. or
decaying material and do not have specialised digestive
systems. They carry out external digestion in which they
feed by secreting extracellular ………………….. e.g. amylase or
cellulase onto the food material outside their body. They
then absorb the soluble products of digestion (e.g. glucose
monomers) by diffusion. All fungi and some bacteria are
saprophytes.
3. Parasites are organisms that live in or on another
organism, the host. The parasite gains nourishment and
causes harm to the host.
4. Mutualism is a close association (symbiosis) between
members of two different species, in which both organisms
benefit from the relationship. e.g. ………………………………………
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Identify the types of nutrition carried out:
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Human digestive system
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Human digestive system
(alimentary canal)
Functions of the digestive system
•Ingestion –
•Mechanical digestion –
•Chemical digestion –
•Absorption –
•Egestion -
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Structure of the mammalian gut wall
Vein
Artery
Nerve
Lymph vessel
Longitudinal muscle
Serosa
Circular muscle
Muscularis
Lumen
Submucosa
Mucosa
Ileum T.S.
Photomicrograph
Plan diagram
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Peristalsis
Describe how the longitudinal and circular muscles work together to move a bolus of
food in one direction along the gut
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Which component of our diet helps stimulate peristalsis? explain why
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Glands in the gut
Glands produce large amounts of secretions, some of which contain digestive enzymes.
There are three types of glands in the gut:
1. Large glands found outside the gut with secretions passing through tubes or ducts into
the gut cavity.
• Salivary glands – produce saliva which contains mucus to lubricate the food and amylase
which breaks down its substrate ___________ into maltose.
• Liver • Pancreas -
2. Glands in the form of cells in the MUCOSA – secretions pass directly into the gut cavity
•Gastric glands in the stomach mucosa secrete gastric juice, this contains:
- Hydrochloric acid - Endopeptidase -
•Glands found at the base of the villi in the small intestine mucosa. These secrete digestive
enzymes exopeptidase, lipase and maltase.
3. Glands in the form of cells in the SUBMUCOSA – secretions pass directly into the gut
cavity
•Brunner’s glands in the submucosa of the duodenum secrete alkaline mucus
What is the function of this alkaline mucus ?
•
•
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Organisms with a varied diet require more than one type of enzyme to completely digest
carbohydrate, protein and lipid substrates present in the ingested food.
Digestive enzymes
Enzyme
Substrate
Product
Gland/s it is
secreted from
Site of
action
Salivary amylase
Endopeptidases
Pancreatic amylase
Exopeptidases
Maltase
Lipase
1. Explain the difference between an endopeptidase and an exopeptidase.
2.
Which enzymes are involved in the complete digestion of
a) Carbohydrates?
b)
Proteins?
c)
Lipids?
3. Note: BILE is NOT an enzyme. It is produced by the liver and stored in the gall bladder
Functions of Bile:
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Ileum
The ileum is well adapted for absorption as it has the following features :
•
•
•
•
Specialised cells in the mucosa of the ileum:
1. Columnar epithelial cells give 2 adaptations of
these cells
•
•
2. Goblet cells what do these cells secrete?
why?
Label a goblet cell and an epithelial cell
on the micrograph
T.S. Ileum showing cells of the villi
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A villus
Substance
Method of absorption
Glucose
Amino acids
Fatty acids and glycerol
Which blood vessel transports absorbed nutrients to the liver?
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Large intestine
The large intestine is about 1.5 metres long and is divided into the caecum, the appendix,
the colon and the rectum. By the time it reaches the rectum, indigestible food, sloughed
off cells, bacteria and undigested cellulose (dietary fibre) are egested as faeces.
What is absorbed in the large intestine?
•
•
•
Uses of the products of digestion
Glucose
Amino acids
Lipids
Uses of
products of
digestion
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Summary sheet
annotate this to help consolidate what you have learnt about the digestive system.
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Adaptation for different diets
Reptiles and amphibians swallow food immediately
when caught, but in mammals food is retained in the
mouth whilst it is cut up and chewed.
Mammals have a palate that separates the nasal cavity from
the mouth. This allows the food to be retained in the mouth
rather than swallowed whole between breaths. Different
mammals have different gut and dental adaptations specialised to their diet.
Dentition
Teeth are important in the …………………….. digestion of food. Chewing is important as it
makes it easier to swallow and also increases the ……..………… …………….for enzyme action.
Human teeth are relatively unspecialised as humans are…………………………….. However there
are four different types of teeth with different functions.
Tooth Type
Function
Incisors
Canines
Molars and
pre molars
Question. How many teeth do humans have altogether?
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Herbivore adaptations
.
This diet is cellulose based. Cellulose is difficult to digest.
Herbivore teeth are adapted for GRINDING to
increase surface area for bacterial cellulase action.
Herbivore dentition:
Features of grazing herbivore dentition:
•
Incisors and horny pad:
•
Canines:
•
Molars:
•
Diastema:
•
Jaw movement:
•
Open roots:
Carnivore adaptations
Carnivore dentition
Carnivorous mammals have teeth adapted for catching and killing prey, cutting or
crushing bones and for tearing meat.
Features of carnivorous dentition:
•
Small sharp incisors:
•
Large curved canines:
•
Premolar/molars:
•
Carnassials:
•
Powerful jaw muscles:
•
Jaw movement:
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Adaptations of the gut: Ruminant Herbivores
•Ruminants are animals such as cows and sheep which mainly eat grass and forage.
•This food contains a lot of cell walls made out of …………………….. which they are
unable to digest as they do not produce the enzyme ………………………………
•To overcome this, they have a specialised stomach composed of 4 chambers.
One of these chambers, the RUMEN, is where MUTUALISTIC ………………. live.
Cellulose digestion:
•
The grass is chewed, mixed with saliva and swallowed. In the rumen it is
churned and mixed with bacteria that secrete cellulase to digest ……………….,
forming β-glucose. The glucose is fermented (under anaerobic conditions) to
form organic acids which are absorbed into the blood, providing energy for the
cow. The waste products are carbon dioxide and methane which are passed
out. The saliva contains urea which the bacteria can use as a nitrogen source
to manufacture amino acids and proteins.
•
The contents of the rumen are regurgitated to the mouth via the reticulum,
where the grass is rechewed – this is known as chewing the ……………
•
When the rumen contents are reasonably liquid they pass to the omasum where
………… is reabsorbed and the abomasum (the true stomach) for digestion of
protein.
•
The bacteria in the rumen are kept separate from the acid found in the
abomasum. Once the bacteria enter the abomasum they are killed by the acid.
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And provide an important source of …………..for the animal.
Non-ruminant herbivores
e.g. rabbit
In the rabbit the caecum is enlarged to accommodate the cellulose
digesting bacteria.
As the bacteria are towards the end of the gut, regurgitation is not
possible. Instead, refection (or copraphagy) occurs, where the rabbit
ingests faecal pellets so that the material passes through the gut twice to
increase efficiency of digestion.
Question
Why are the guts of herbivores longer than those of carnivores and
omnivores?
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Parasite nutrition.
Definition of a parasite:.
The pork tapeworm – a parasite of the gut.
Taenia solium, the pork tapeworm has two hosts
•
the primary host is the human where it lives in its adult form in the
intestines.
•
the secondary host is the ………….. where it lives in the muscle as
cysts.
The adult tapeworm.
Add the labels hooks, suckers and proglottid (segment)
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Tapeworm lifecycle
(note you do not need to memorise the details of this.)
Fill in the labels.
Using the diagram to help you, what simple precautions should be taken to avoid
becoming infected with tapeworm?
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PROBLEMS FACED BY THE TAPEWORM
ADAPTATIONS THAT THE TAPEWORM
HAS EVOLVED
Gut is in constant motion (peristalsis
and stomach churning)
Extremes of pH along the gut, exposure
to digestive enzymes and the host’s
immune response
Reproduction
- Unlikely to find a mate in host
- High offspring mortality
- Difficult for eggs to reach a new host
Host death
Question:
1.
Why does the tapeworm not require a digestive system?
2. How is the tapeworm adapted to gain its nutrients?
(hint- think about the size and shape of the organism)
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