UNIT 5 Feeding Relationships

7/28/2019 UNIT 5 Feeding Relationships

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Biology Form 4 Page 56 Ms. R. Buttigieg

UNIT 5 Feeding RelationshipsUNIT 5 Feeding RelationshipsUNIT 5 Feeding RelationshipsUNIT 5 Feeding Relationships

Some common terms, which shall be used in this unit, are:

EcosystemA reasonably self-contained area together with all its living

organisms

Habitat

The physical or abiotic part of an ecosystem, i.e. a defined areawith specific characteristics where the organisms live, e.g. oakforest, deep sea, sand dune, rocky shore, moorland, hedgerow,

garden pond, etc.

CommunityThe living or biotic part of an ecosystem, i.e. all the organismsof all the different species living in one habitat.

Population The members of the same species living in one habitat

Ramla located along the northern shore of Gozo is an example of a sand-dune ecosystem

a.Name two different habitats in this site:

________________________________________, _____________________________________

b. Give an example of a community in this area

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

c. Give an example ofthree different populations that can be found in this area:

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

d. Name two threats to this area:

________________________________________

________________________________________

________________________________________

________________________________________


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5.1 Plants as producers.5.1 Plants as producers.5.1 Plants as producers.5.1 Plants as producers. (see GCSE Biology pg. 35 44)All the energy in the world comes from the sun, but the organisms that are capable of making

direct use of it are the plants. For this reason they are called theprimary producers.

External and internal features of a leaf as an organ for photosynthesis. (see book pg. 50-53)

Function of Leaves:

a. Increase surface area for Photosynthesis.

b. Gas exchange (CO2 in, O2 out).

c. Site of transpiration, evaporation of water that helps pull water up from roots.

Structure of leaves - The leaves are the part of a plant where most photosynthesis takesplace.

EXTERAL STRUCTURE: Leaf Blade: Wide flattened area

of leaf for concentrating sunlight

on photosynthetic cells.

Petiole: Short stem that

attaches leaf to main stem orbranch.

Veins: Vascular bundles within

leaf for transport.Node: Growth region of stemwhere leaves or new branches

arise.

Axillary bud: Baby leaf or stem


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Internal Leaf Structure:

1. Waxy cuticle - this gives the leaf a waterproof layer, which lets in light.

2. Upper epidermis - provides an upper surface. Light passes through.

3. Palisade cells - are packed full of chloroplasts, so lots of photosynthesis

4. Spongy mesophyll - Collection of damp, loosely packed cells. Gas exchange.

5. Lower epidermis is the layer of cells on the lower surface. Has stomata.

6. Air spaces - allow contact between air and moist cell surfaces.

7. Stoma - a hole in the leaf from which gases diffuse through.

8. Guard cells - change shape to close the stoma.

Photosynthesis takes place in the mesophyll cells

inside a green plant's leaves.

As you can see there are two kinds of mesophyll cells

- palisade mesophyll and spongy mesophyll. The

mesophyll cells contain tiny organelles calledchloroplasts, which contain a green chemical calledchlorophyll. Chlorophyll enables the light energy from

sunlight to be converted into chemical energy for the

photosynthesis reaction.


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The importance of PHOTOSYTHESIS

Factors affecting the rate of photosynthesis.

These are mainly the amounts of:

o water

o carbon dioxideo sunlighto temperature.

1. The amount of water is effected by how much is taken up through the roots and howmuch is lost from the leaves. If less water is available in the leaf then photosynthesis

will occur more slowly.

2. Sometimes photosynthesis is limited by the level of carbon dioxide. Even if there is

plenty of light a plant cannot photosynthesise if it has run out of carbon dioxide. If

there is less carbon dioxide around then photosynthesis will occur more slowly.

3. Without enough light a plant cannot photosynthesise very fast, even if there is

plenty of water and carbon dioxide. Increasing the light intensity will makephotosynthesis faster.

4. Temperature can be a limiting factor too. If it gets too cold the rate of

photosynthesis will slow right down; equally, plants cease to be able to photosynthesise

if it gets too hot.

If you plot the rate of photosynthesis against the levels of these three limiting factors

you get graphs like the ones on the next page.


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Fate of carbohydrate products in the plant.

The glucose produced in the photosynthesis reaction can be converted to sucrose and carried to

other parts of the plant in phloem vessels.

Complete:

Green plants make their own food by ______________________ . Green __________________

in the chloroplasts of the leaves traps the suns ________________. Raw materials for this

process are carbon ___________________ and ___________________. Sugars are made in the

leaves and are soon changed to ___________________. The waste products of this process is

the gas ___________________.


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Questions from Past Papers

The diagram below shows the internal structure of a leaf.

a) Name the parts labelled:

A __________________________ B ___________________

C ___________________________ D ___________________ (4)

b) Part A and part B are both adapted to facilitate photosynthesis. Explain how.

______________________________________________________________________________

______________________________________________________________________________

______________________________________________________________________________

___________________________________________________________________________ (4)

c) Give one other adaptation of leaves for photosynthesis.

______________________________________________ (1)

d) The cuticle of the leaf in the diagram is waxy. State one way in which a waxy cuticle may be

helpful to a plant.

_______________________________________________________________ (1)

e) State one importance of stomata to plants.

______________________________________________________________ (1) Total 11 marks


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The following diagram shows the apparatus used in an experiment to show the affect of light

intensity on the rate of photosynthesis.

a) List four factors which must be kept constant in this experiment while intensity of light is

being changed.

1______________________ 2_________________

3 ______________________ 4 _________________ (4)

b) Bubbles of a gas are being produced during the experiment. Name the gas.

____________________________ (1)

c) How can you test that your answer to b is correct?

_______________________________________________________________ (2)

d) How can the bubbles of gas, being produced, help to measure and compare the rate of

photosynthesis?

_______________________________________________________________ (1)

e) Why was the paper clip used?

_______________________________________________________________ (1)

f) Name one other factor besides light that may limit the rate of photosynthesis.

____________________________________________ (1)

g) Give a word equation for photosynthesis.

_______________________________________________________________ (3)

Total 13 marks


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Animals as consumers.

Nutrition in plants is known as autotrophic nutrition as they make their own food. We

refer to nutrition in animals as holozoic nutrition where complex food is taken into a

specialist digestive system and broken down into small pieces to be absorbed

This consists of 5 phases:

ingestion - taking large pieces of food into the body

digestion - breaking down the food by mechanical and chemical means

absorption - taking up the soluble digestion products into the body's cells

assimilation - using the absorbed materials

egestion - eliminating the undigested material

The stages in a protist1

The shots below show Amoeba proteus in the process of eating another protist calledTetrahymena.

1. Sensing the organism 2. Forming pseudopodium 3. Pseudopodium formation

4. Pseudopodium circling it 5. Pseudopodium closed 6. Tetrahymenabeing digested

Ingestion: Stages 1 to 4 in the shots above show ingestion where the organism (food) is beingtaken into the Amoebas body.

Digestion: Stage 5 shows the beginning of digestion where breaking down of the food is startedin the amoebas body in what we refer to as a Food vacuole.

Absorption: The food is distributed through the entire cell

Assimilation It is used for processes in theAmoeba such as respiration.

Egestion Any waste food is egested as the food vacuole moves towards the amoebasperiphery and breaks open releasing the waste material out of the cell.

1http://130.158.208.53/WWW/PDB/Images/Sarcodina/ap/feeding.html -Amoeba proteus feeding


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The Stages in a Human

Make sure you know the following: -

o Be able to draw and label the diagram of the human alimentary canal - Book pg. 99, figure 11.5

o Structure and function of the human gut and its associated glands Book pg. 97-102

o Be able to draw and label the villus structure Book pg. 102, figure 11.10

Some brief notes:

1. Ingestion Food is taken into the body through the mouth.

2. Digestion also starts in the mouth.

o Food broken then mixed with saliva, which moistens it and adds the enzyme salivaryamylase, which begins to digest starch.

o Tongue helps to form the food into a small, moist ball called a bolus, which can beeasily swallowed.

o The bolus is squeezed down the oesophagus (gullet) by wavelike contractions of thesurrounding muscle. This is called peristalsis. (See pg. 98 figure 11.3)

Work out pg. 98 numbers 1- 3

The start of the process of digestion occurs inthe mouth using the teeth and tongue.

There are 4 types of human teeth:

1. Incisors for cutting.

2. Canines for piercing.

3. Pre-molars for cutting and rushing.

4. Molars for crushing and grinding.


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As food passes down the digestive system different secretions are added to the food inorder to digest the large molecules.

Mouth Saliva is released from salivary glands. It contains amylase and digests starch to maltose.

Stomach Makes gastric juice, containing protease (pepsin) and hydrochloric acid. The acid killsmicrobes and creates to best pH for the protease to digest proteins.

The liver makes bile that contains bile salts. They break the large fat droplets down into smallerdroplets. Bile is stored in the gall bladder.

The pancreas makes more protease and amylase. It also makes lipase to digest the fats to fatty acidsand glycerol.

The small intestine makes enzymes such as maltase. This digests maltose to glucose.

Answer the following:

a. Name the enzyme that digests proteins ____________________

b. Explain why lipase does not digest starch ________________________________________________

____________________________________________________________________________________

c. Why does boiling an enzyme preven it from working? _______________________________________

____________________________________________________________________________________

d. What is the function of bile? ___________________________________________________________

e. Why does the stomach produce acid? ___________________________________________________

____________________________________________________________________________________


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Work out GCSE Biology pg. 101 numbers 1-4

The Small Intestines Apart from secretion of some enzymes, these have the important

function of food absorption that is made possible with the help of the villi. (sing: villus)

Although we refer to the small intestines as a whole thing, in reality, it is divided into two part

the duodenum and the ileum. It is adapted for absorption as:

1. Has a thin lining2. A good blood supply3. A very large surface area (due to the villi)


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The Large Intestines By the time food gets here, it consists mainly of fibre, dead cells,

bacteria and water. As it passes along the large intestine some of the water is absorbed

into the blood. The solid waste or faeces are stored in the rectum, and eventually areegested from the anus.


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Cellulose digestion: an adaptation of herbivorous mammals as primary consumers. See pg. 295-6

Dentition: -

Lower jaw loosely articulated, allowing side to side and up and down movement.

Incisors long, chisel shaped, forward-pointing for cropping grass.

No canines

Diastema for manipulation grass.

Broad, ridged, premolars and molars for grinding grass.

Open roots to allow teeth to grow continuously.

Cattle and sheep are herbivores and ruminants. Ruminants digestive systems allow a high

proportion of cellulose to be digested. Ruminants have 4 stomachs (rumen, reticulum,

omasum and abomasum).

Long intestine gives time for digestion.

Large caecum and appendix containing bacteria which secretes cellulase.

Four stomachs to help the digestion of cellulase.

1) Food is swallowed and lands in the rumen. This contains bacteria, some protists and yeasts. Food

remains here for up to 30 hrs. The food is often regurgitated to be chewed again (chewing the cud).

The microbes break down the cellulose (with cellulase).

2) Next food enters the reticulum, sometimes food enters here first. Food moves between the

rumen and reticulum fairly freely.

3) As the food enters the omasum, where water and organic acids are removed. No enzymes are

secreted.

4) From here on it follows a similar path as in the human gut, with enzymes being secreted etc.

NB. many of the bacteria etc are also taken in with the food and digested, which makesprotein digestion from the rumen even more efficient, as the microbes can convert low

grade protein and urea into a high grade version that can be digested by the cow.


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1. The diagram shows the skull of a mammal from theside.

i) What would this mammals diet have been?

______________________________________________

____________________(1)

ii) Give two (2) features, shown in the diagram, which support your answer in 2i.

a) __________________________________________________________________

b) _______________________________________________________________(1,1)

(total 3 marks)

2 a) Explain the difference between Digestion and Egestion (3)

b) Protein is an important constituent of a balanced diet.(i) What are proteins?

(ii) Name one importance of proteins to organisms.

(iii) Where does digestion of proteins start in humans?(iv) Name an enzyme that digests proteins. (2, 1, 1, 1)

c) A student claims that nuts are rich in oil and protein. Describe two separate simple tests by

which the student can show that nuts are rich in these two nutrients. (3, 4)

3. The following diagram shows part of the digestive system of a mammal.

(i) Label the parts marked.

A:___________________________(1)

B:__________________________ (1)

C: __________________________(1)

D:__________________________ (1)

E:__________________________ (1)

F:__________________________ (1)

G:__________________________(1)

H:__________________________(1)

I: __________________________(1)

(ii) Use the letters in the diagram to complete the following sentences.

a) Bile is produced in _____________ and stored in _____________. (2)

b) ____________ is highly acidic. (1)

(12 marks)


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Ways of representing feeding relationships. (read GCSE Biology pg. 224-227)

Food Chains and Food webs

o Food Chains and webs begin with energy from the sun.o A food chain shows us what eats what in a community.o The arrowsin the food chain show the transfer of food energy between organisms.

Food chains always begin with the sun (which isnt written each time), and then

there is a green plant (can include leaves, fruits or seeds) Each step in the food chain is called a trophic level

A food web is made up of interconnected food chains.

Arrange the organisms below in a food chain:

____________________________________________________

Some terms worth knowing:

o Producers - green plant or organism that carries out photosynthesiso Primary consumer The organism that eats the producero Secondary consumer - The organism that eats the primary consumer.o Tertiary consumer - The organism that eats the secondary consumer.o Detritivores - animals that feed off all dead plants and animals.

o Scavengers - carnivores that eat that dead remains of animals killed by predators.

o Decomposers microbes that feed on dead and decaying material.

Apply these terms for the organisms in the food chain you wrote above


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1. Look at the seashore food web:

Sea bird

crab starfish

dog whelk

barnacle limpet mussel

small algae

a) How many primary consumers are there? Name them

_________________________________________________________________________

b) How many secondary consumers are there? Name them

_________________________________________________________________________

c) Draw a food chain with 5 links from this food web

_________________________________________________________________________

d) Suppose all star fish died from pollution. What would happen to the number of:

i. Mussels ______________________________________________

ii. Small algae ____________________________________________

2. Complete the paragraph below:

Producers are able to make their own _________________. Producers are fed upon by

herbivores or _________________ consumers. These in turn provide food for

_________________ consumers. Dead and _________________ matter provides food for

_________________ and Detritivores. Feeding relationships can be shown in food

________________ and in food _________________.

Pyramids of numbers and biomass

A pyramid of numbers

tells us the number of organisms involved in a food chain.

A pyramid of biomass

tells us the mass of the organisms involved in a food chain.


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Pyramids of numbers

o This tells us how many organisms are involved at each stage in the food chain.o At each trophic level the number of organisms gets less.

What happens to the numbers of individualsas you go up the pyramid? _______________

o Sometimes a pyramid of numbers does not look like a pyramid at all as it doesnt take

into account the size of the organisms.

Pyramids of biomass

o This takes into account the size of the organisms at each level.

o It looks at the mass of each organismo If we take the information from the pyramid of numbers and multiply it by the

organisms mass we get a pyramid shape again.


Discuss pg. 229 number 4

Work this on a separate sheet: The table shows information about a food chain.

Producer Primary Consumer Secondary Consumer Tertiary Consumer200 leaves 100 caterpillars 5 trushes 1 kestrel

a) Draw a pyramid of numbersb) The average mass of each organism is:

leaf (5g), caterpillar (4g), trush (70g), kestrel (250g)

Knowing this draw a biomass pyramid

c) What difference can you see between the two pyramids?

parasites

ladybirds

greenfly

rosebush

190 000

200 000

1 500 000


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1. ____________________ are animals that are eaten only by decomposers after they die.

Secondary consumerTop carnivore

Carnivores

2. Animals that only eat other animals are called ______________________

HerbivoresCarnivores

3. What part does the sun play in food chains and webs?

It provides the energy to start a food chain

It transfers food energy between organisms It links the food chains

4. The arrows in food webs and food chains show the transfer of food energy betweenorganisms.

TrueFalse

5. An animal that eats other plants and animals is called a _______________

ProducerConsumer

Energy flow through an ecosystem. (see GCSE Biology pg. 231 233)

Energy flows through ecosystems in one direction, typically from the Sun, through

photosynthetic organisms or producers, to herbivores to carnivores and decomposers.

Energy is transferred through the trophic levels in food chains and food webs and is

dissipated.

At each link in a food web, some energy is stored in newly made structures but much

energy is lost into the environment as heat.

Continual input of energy from sunlight is required to keep this process going.


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Efficient food

So little energy is left by the

end of a food chain that theycannot get too long. In fact the

shorter they are the better.

Losing one trophic level means that

you get more energy at the end. It ismore efficient.

Intensively reared livestock are

kept in restricted conditions so thatthey do not waste energy moving

around. However, apart from the

ethical questions, they still end upwasting energy from their food.

Land can feed more people if used

for crops. However some land such

as hillsides and marshy areas arenot suitable for crops and so rearing

animals on it is the most efficient

use.


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Work out the following:

For every square metres of grass that it eats, a cow gets 3000kJ of energy. It uses 100 kJ for

growth, 1000kJ are lost as heat and 1900kJ are lost in faeces.

a) What percentage of the energy in one square metre of grass

i) is used for growth? ____________________________________________________________

ii) passes through the gut and is not absorbed? ________________________________________

b) If beef has an energy value of 12kJ per gram, how many square metres of grass are needed to

produce 100g of beef ___________________________________________________________

_____________________________________________________________________________

1. a) Write a balanced equation ( in words or symbols) summarising the process of

photosynthesis. (3)

b) Name two environmental factors that can affect the rate of photosynthesis. (2)

c) Draw a large labelled diagram to show the internal cellular structure of the leaf. (5)

d) Describe an experiment to show that chlorophyll is necessary for photosynthesis to

occur. (5)

(15 marks)

2. Use the following terms to complete the paragraph:

photosynthesis ; energy ; sun ; food/carbohydrates ; 90%

Food chains, webs and pyramids are ways of representing the flow of

__________through an ecosystem. The original source of energy is the _____________.

Green plants use this energy to manufacture ______________________ in the process of

___________________. At each step in the food chain, ________________ of the energy

is lost as it passes from one trophic level to another.

(5 marks)


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3. Study this food web and answer the questions that follow.

i) From the diagram name (a) one producer (b) 2 primary consumers.

a) One producer: _____________________________________________(1)

b) Two primary consumers: ________________ ; ________________(1,1)

c) One secondary consumer: ____________________________________(1)

ii) From the food web shown above, construct a food chain with four links.

______________ ______________ _____________ _____________ (2)

iii) Name the ultimate source of energy for this food web.

______________________________________________________________(1)

iv) Explain why only 10% of energy is transferred from one trophic level to another.

______________________________________________________________

______________________________________________________________(2)

(total 9 marks)

4. Explain the terms community and populations in relation to ecosystems.

i) Community:___________________________________________________

______________________________________________________________.

ii) Populations:___________________________________________________

_____________________________________________________________(2,2)

(total 4 marks)

Exam tips

Don't worry if you have never heard of the organisms used in a food chain and web question. There willalways be enough information for you to work out the answer.

When looking at a food web, check carefully which way the arrows are pointing. Remember the arrowsrepresent a flow of materials orenergy, so the arrow should go from the organism which is beingeaten to the animal which is eating it.

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UNIT 5 Feeding Relationships