NATIONAL QUALIFICATIONS CURRICULUM SUPPORT
Biology
Unit 3: Living Together
Symbiosis and Social Behaviour
Student Materials
Graeme Steele
[HIGHER]
The Scottish Qualifications Authority regularly reviews
the arrangements for National Qualifications. Users of
all NQ support materials, whether published by
Learning and Teaching Scotland or others, are
reminded that it is their responsibility to check that the
support materials correspond to the requirements of the
current arrangements.
Acknowledgement
Learning and Teaching Scotland gratefully acknowledges this contribution to the National
Qualifications support programme for Biology.
The publisher gratefully acknowledges permission to use the following sources: Deep Sea
World resource made through a collaboration of our author Graeme Steele and Deep Sea
World; image of chimpanzees from Royal Zoological Society, Edinburgh © RZSS; image of
Members of our Vampire Bat Colony © The Centre for Conservation of Specialized Species; 3
images of Dr. Jane Goodall with chimpanzees © The Jane Goodall Institute / Derek Bryceson,
© The Jane Goodall Institute / Fernando Turmo, © The Jane Goodall Institute / Hugo Van
Lawick; image of wolves © WolfPhotography.com; image from
http://www.uwphoto.net/pages/gallery_si04-666.html © photography by Jim Christensen;
image from http://chemistry.csudh.edu/faculty/jim/lembehsmall/hermit.jpg © Jim Lyle; image
of Fire Ant colony from
http://hydrodictyon.eeb.uconn.edu/people/adams/FireAntColony.jpg.jpg; image of pea pod
© 2011 Microsoft Corporation. Clipart; image of a tick, photograph by William Needham on
Hiker’s Notebook website; image of an adult flea, photo courtesy CDC/Vector Ecology &
Control Laboratory, Fort Collins, Colo; image of a tapeworm © dogbreedinfo.com; image of
veteran oak tree covered in lichen, mosses and ferns © Lorne Gill/SNH; image of Rhizobium
nodules © Courtesy J. Wynne. Reproduced by permission from Compendium of Peanut
Diseases, 2nd Ed., 1997, American Phytopathological Society, St. Paul, MN, USA; image of a
hummingbird © Fotolia;
Every effort has been made to trace all the copyright holders but if any have been inadvertently
overlooked, the publishers will be pleased to make the necessary arrangements at the first
opportunity.
© Learning and Teaching Scotland 2011
This resource may be reproduced in whole or in part for educational purposes by educational
establishments in Scotland provided that no profit accrues at any stage.
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LIVING TOGETHER (H, BIOLOGY)
© Learning and Teaching Scotland 2011
Contents
Activity 1: Walkabout/talkabout carousel
4
Activity 2: Symbiosis card sort
5
Activity 3: Types of symbiosis
9
Activity 4: Branching keys
10
Activity 5: Symbiosis revision
11
Activity 6: The prisoners’ dilemma
12
Activity 7: Odd one out
14
Activity 8: Jane Goodall
18
Activity 9: Chimpanzee behaviour and expressions
(see separate pdf file)
19
Activity 10: Chimpanzee hierarchy (see separate pdf file)
20
Activity 11: Social behaviour continuum
21
Activity 12: Symbiosis
23
Solutions to Activity 5
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STUDENT MATERIALS
Activity 1: Walkabout/talkabout carousel
Instructions
1.
Split into 5 groups.
2.
Each group must put one of the following headings onto the poster .
3.
You have 3 minutes to add as much detail to this poster as you can.
4.
Move to the next poster after this time and add/amend information on
this poster.
5.
Repeat until back at first poster.
6.
Each group must take a turn to feedback to the whole group from the
poster they started with.
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STUDENT MATERIALS
Activity 2: Symbiosis card sort
Instructions
1.
Print out following pages and cut into individual cards with a matching
picture.
2.
Make three categories to place cards into; parasitism, mutualism, social
behaviour.
3.
read out statement 1.
4.
place the photo of the organism into one of th e three categories.
5.
Read out statement 2.
6.
choose to move the photo to a new category or leave it in same place .
7.
continue until all statements read and final decision made as to
category.
8.
repeat with all cards.
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STUDENT MATERIALS
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
6
Bacteria live in the intestines of a cow.
The bacteria get a constant source of
moisture and food.
The bacteria get a stable habitat to live
in (temperature and pH).
The bacteria break down cellulose.
Without the bacteria the cow would not
be able to break down the grass cell
walls.
www.co2calculator.wordpress.com
Oscar the chocolate labrador lives with
his owner, Mr Fraser.
Oscar recently cost Mr Fraser £90 in
vet’s bills.
Mr Fraser gives the dog food and water
whenever it is needed.
Oscar gets to sleep on the end of Mr
Fraser’s bed.
Oscar makes Mr Fraser very happy.
Some species of shrimp live with a fish
called a goby.
The shrimp digs a house by moving
sand around.
The goby lives in the house the shrimp
digs out.
The shrimp is blind and uses its feelers
to check the goby is nearby.
If the goby notices danger and retreats
into the home the shrimp does too.
A hermit crab is able to carry an
anemone on its back.
The anemone is put there by the crab.
The weight of the anemone makes it
harder for the crab to move around.
Food scraps from the crab can get to
the anemone.
The anemone will stop an octopus from
eating the crab.
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www.uwphoto.net
STUDENT MATERIALS
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
A tick is a small invertebrate that can live on
larger animals.
It bites into the other organism and buries its
head into the organism’s skin.
Here it feeds on blood from the organism.
The blood is stored in an expandable pouch
on the tick.
The organism loses blood and may get an
infection, eg Lyme disease in humans.
© Gary Alpert
Ants work together.
Most will never get to breed.
They can get more food by working
cooperatively.
The colony will die if each type of ant
does not do its job.
Since the ants are closely related, similar
genes will be passed on.
http://hydrodictyon.eeb.uconn.edu/people/adams/FireAntColony.jpg.jpg
1.
2.
3.
4.
5.
1.
2.
3.
4.
5.
Bodungo chimps are social animals.
Chimps form close relationships with
each other.
By being in a group they share food
and resources.
A young male is unlikely to become
the most dominant male in the group.
By living together as a large group the
troop is likely to be successful and
their genes will be passed on.
© RZSS
Malaria kills many African children each
year.
It is caused by a protist.
Mosquitoes carry protists for part of their
lifecycle.
The mosquito transfers the protist when
feeding on human blood.
The protist needs both vectors to complete
its lifecycle.
LIVING TOGETHER (H, BIOLOGY)
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STUDENT MATERIALS
1.
2.
5.
Birds frequently live in trees.
They use parts of an old tree to make their
nests.
The bird gains an advantage of a home to live
in.
The tree gains little from the relationship,
maybe some fertiliser.
The bird does nothing to harm the tree.
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LIVING TOGETHER (H, BIOLOGY)
3.
4.
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STUDENT MATERIALS
Activity 3: Types of symbiosis
There are two basic types of symbiosis. Remember that symbiosis is the
relationship between two organisms of different species that benefits one or
both organisms:
 mutualism – a symbiotic relationship that benefits both organisms involved
 parasitism – a symbiotic relationship that benefits one organism while
harming the other.
Decide which type of symbiosis is described in each sentence below.
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
A tick living on a dog.
A tapeworm living in a sixth-year student’s intestines.
A bird building its nest in a tree. The bird’s faeces fertilise the soil.
A hermit crab carrying a sea anemone on its back.
A bristle worm living with the hermit crab.
Head lice living on a human scalp.
Mistletoe putting its roots into its host tree.
Ants and an acacia tree living together and both receiving benefit.
Bees and a flower.
Bacteria living in the intestines of a cow to help it break down
cellulose.
A clownfish and a sea anemone.
A sixth-year student and their pet.
A rhino and a tick bird.
Lichen – a composite organism of a fungus and an alga that benefits
both.
Cleaner fish eating parasites off of a grouper fish.
Bacteria, Rhizobium, that live in nodules on plants roots and fix
nitrogen, using energy from the plant, which the plant is able to then
use.
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STUDENT MATERIALS
Activity 4: Branching keys
Make a branching key/protocol for finding out what type of sym biosis is
being shown. You need to distinguish between mutualism and parasitism.
Example of a branching key:
Check it works with the various examples – possibly use the symbiosis
worksheet.
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STUDENT MATERIALS
Activity 5: Symbiosis revision
1.
Explain the term ‘symbiosis’.
2.
Define the term ‘parasitism’.
3.
Why is it necessary for a parasite to keep its host alive?
4.
Explain how parasites and their hosts interact to maintain a stable
relationship.
5.
Describe the three ways that parasites can be transmitted.
6.
Describe, in general, the structure of most parasitic cycles.
7.
Many parasites have resistant larval forms incorporated into their life
cycles. Suggest a reason for this.
8.
Explain, in evolutionary terms, how most parasites have become host
specific.
9.
Describe the phenomenon of mutualism.
10.
Describe the relationships that exist between the following organisms:
(a)
(b)
(c)
fungi and algae in lichens
corals and algae
cleaner shrimp and fish.
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STUDENT MATERIALS
Activity 6: The prisoners’ dilemma
The prisoners' dilemma game can be played online here:
http://serendip.brynmawr.edu/playground/pd.html.
The prisoners’ dilemma
Frank and Bob have been arrested for robbing a bank and placed in separate
isolation cells. Both are selfish and only care about themselves.
A prosecutor makes the following offer to each. ‘You may choose to confess
or remain silent. If you confess and your accomplice remains silent I will
drop all charges against you and use your testimony to ensure that your
accomplice does serious time (10 years). Likewise, if your accomplice
confesses while you remain silent, they will go free while you do the time (10
years). If you both confess I get two convictions, but I’ll see to it that you
both get early parole (after 7 years). If you both remain silent, I ’ll have to
settle for token sentences on firearms possession charges (2 years each). If
you wish to confess, you must tell me in the morning.’
Initially the reaction of most observers is that they should both keep quiet,
however they both end up confessing and implicating the other person.
This is surely the worst situation. Both get 7 years, so 14 in total!! Why is
this? The solution becomes apparent when we look at the potential outcomes.
If one person does not confess then they will either get 2 years or 10 years –
an average of 6 years. If they do confess they will either get 0 years or 7
years – an average of 3.5 years. So they choose to confess and implicate the
other on that basis.
The ‘dilemma’ faced by the prisoners here is that, whatever the other does,
each is better off confessing than remaining silent. But the outcome obtained
when both confess is worse for each than the outcome they would have
obtained had both remained silent.
A common view is that the puzzle illustrates a conflict between individual
and group rationality. A group whose members pursue rational self -interest
may all end up worse off than a group whose members act contrary to rational
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LIVING TOGETHER (H, BIOLOGY)
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STUDENT MATERIALS
self-interest. It shows a choice between selfish behavio ur and socially
desirable altruism.
Further explanation and risk/rewards matrix
The reason that both prisoners choose to confess is easy to explain.
The following is the explanation assuming that Frank and Bob cannot
communicate to each other.
Frank has the following matrix (Bob has the reciprocal matrix):
Frank confesses
Frank is silent
Bob is silent
0
2
Bob confesses
7
10
The expected payoff for the game (the average amount of benefit that a
strategy will provide) is better — in this case, 3.5 years expected jail time for
confessing versus 6 years for silence — if Frank confesses. Therefore, from a
rational perspective, Frank should choose to confess rather than remain silent.
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STUDENT MATERIALS
Activity 7: Odd one out
Instructions
1.
Print and then cut out the cards on the following 3 pages
2.
Pick the odd one out in each case
3.
Give a reason for your choice in each case
4.
Repeat for each card
5.
Finally make 3 further odd ones out and give them to another group to
try
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STUDENT MATERIALS
Parasitism
Mutualism
Why?
Alliances
Leeches
Lions
Why?
Ticks
Prisoners’ dilemma
Kin selection
Why?
Altruism
Wasps
Chimpanzees
Why?
Termites
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STUDENT MATERIALS
Grooming
Facial display
Why?
Body posture
Clownfish and anemone
Goby and blind shrimp
Why?
Rhizobium and clover
A fireman saving a baby from
a fire
Worker ants never getting the
chance to breed
Why?
A person risking injury to
save a relative
Saving a brother from harm
Saving a cousin from harm
Saving your wife/husband
from harm
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Why?
STUDENT MATERIALS
Co-evolution
Symbiosis
Why?
Goby and blind shrimp
(mutualism)
Why?
Why?
Why?
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STUDENT MATERIALS
Activity 8: Jane Goodall
Find out who Jane Goodall is and why primate behaviour specialists
(primatologists) were more inspired by her work compared to previous work
that had solely been done in laboratories and zoos.
Extension
Explain why some behaviour specialists feel that Jane Goodall ’s work was
tainted due to her anthropomorphism of some of the chimps.
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STUDENT MATERIALS
Activity 9: Chimpanzee behaviour and expressions
See separate pdf files.
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STUDENT MATERIALS
Activity 10: Chimpanzee hierarchy
See separate pdf files.
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STUDENT MATERIALS
Activity 11: Social behaviour continuum
Agree strongly
Agree
Neutral
Disagree
Disagree strongly
Students must place the following statements into the categories above (this
will work best if the statements on the following pages are printed out and
placed on an actual continuum):
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
21.
22.
23.
24.
Living in a group is beneficial.
Competition will occur in a group.
If too many people lived together there would be lots of fights .
A highly successful parasite will kill its host fairly rapidly .
In mutualism one organism must have evolved rapidly to take advantage
of the other organism.
Killing all parasites is a good idea.
Zoos are good places to do research.
A person is more likely to help someone they know .
Humans make alliances in their lives.
Humans have a similar social structure to ants .
Animals will stop being altruistic if it is not reciprocated .
Ritualistic display is good as it avoids ‘real’ fights.
The more complex the social structure the less advanced the organism.
Human behaviour in ‘Big Brother’ is similar to that in real life.
If clownfish get very hungry they should just eat part of the anemone .
Parasites must be careful not to harm their host too much .
Plants cannot be parasites.
Mutualism will increase the ability of a species to survive.
I can see myself being altruistic in the future .
I would be as likely to be altruistic to a stranger in a life or death
situation as a relative.
Social insects are ‘happy’ just to contribute to the colony .
Hierarchies work best for the individual at the bottom.
A chimp reared by humans could easily be released into the wild.
Territories help to organise resources.
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STUDENT MATERIALS
Cut out the cards below and place on the continuum you have been given.
Living in a group is beneficial.
Killing all parasites is a good idea.
Competition will occur in a group.
Territories help to organise resources.
If too many people lived together
there would be lots of fights.
Zoos are good places to do research.
A highly successful parasite will kill
its host fairly rapidly.
A person is more likely to help
someone they know.
In mutualism one organism must
have evolved rapidly to take
advantage of the other organism.
Humans make alliances in their lives.
Humans have a similar social
structure to ants.
Animals will stop being altruistic if it
is not reciprocated.
Ritualistic display is good as it
avoids ‘real’ fights.
The more complex the social
structure the less advanced the
organisms.
Human behaviour in ‘Big Brother’ is
similar to that in real life.
If clownfish get very hungry they
should just eat part of the anemone.
Parasites must be careful not to harm
their host too much.
Plants cannot be parasites.
Mutualism will increase the ability of
a species to survive.
I can see myself being altruistic in
the future.
I would be as likely to be altruistic to
a stranger in a life or death situation
as a relative.
Social insects are ‘happy’ just to
contribute to the colony.
Hierarchies work best for the
individual at the bottom
A chimp reared by humans could
easily be released into the wild
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STUDENT MATERIALS
Activity 12: Symbiosis
What is symbiosis?
A symbiotic relationship is an intimate association between different species.
It takes a significant time to arise and occurs through co -evolution. Symbiotic
relationships can be:
 obligate – the association is necessary for at least one of the organisms to
survive
 facultative – the association is beneficial for at least one of the organisms
but is not essential for survival.
There are two types of symbiotic association:
 ectosymbiosis – where one organisms lives on the other organism
 endosymbiosis – where one organisms lives inside the other organism.
Different types of symbiosis
1.
Parasitism
Parasitism is an interaction between organisms of different species in
which one organism (the parasite) benefits and the other (t he host) is
harmed. This can happen through physical damage to the host or
through stealing nutrients from the host.
Question 1
‘Parasites were collected from 107 harbour seals of f the coast of
Schleswig-Holstein, Germany between 1997 and 2000. A total of 77
seals were infected with stomach worms and 4 were infected with
sucking lice.’
(a)
Which parasite is an ectoparasite and which is an
endoparasite?
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STUDENT MATERIALS
(b)
What percentage of the seals from this study was infected with
stomach worms and what percentage was infected with sucking
lice?
(2)
Question 2
‘A fungal parasite of amphibians has been linked to dramatic decline in
population numbers. The fungus grows best in moist environments and
results in a thickening of the skin of an amphibian. ’
(a)
(b)
Why are almost all amphibians at risk of contracting this
fungus?
Why would a thickening of an amphibian’s skin result in
illness and possibly death?
(1)
(2)
‘Some amphibians are resistant to the fungus but can still be carriers. ’
(c)
2.
Why may this be an advantage and a disadvantage to conservation
biologists?
(3)
Mutualism
Mutualism is an interaction between organisms in which both organisms
benefit.
Question 1
‘One of the best known examples of a mutualistic relationship is that
between the clownfish and the sea anemone. Both benefit from the
interaction; the clownfish is protected from predators by the stinging
tentacles of the anemone, and the sea anemone is protected by the
clownfish from anemone-eating butterfly fish and also receives
nutrients from the clownfish waste.’
(a)
(b)
Is this association facultative or obligate?
Do you think that this association will be short or long term?
Why?
(1)
(3)
Question 2
‘Coral reefs are one of the most productive of all ecosystems supporting
around 25% of all marine species. Reef-building coral is formed from
the secretion of a calcium carbonate skeleton by the coral polyps.
Within the cells of a coral polyp live microscopic algae that provide
over 90% of a coral’s nutrients as reefs often form in areas of very low
nutrient concentration.’
(a)
24
Why is coral reef growth limited to areas of clear, relatively
shallow water?
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STUDENT MATERIALS
‘Corals provide the algae with protection and a constant supply of
carbon dioxide without which the algae cannot survive. Temperature
change is one of the environmental stresses that can result in the
depletion of algae numbers which results in the ‘bleaching’ of coral.
The coral will die unless the algae recover, leaving only the calcium
carbonate skeleton.’
(b)
(c)
(d)
3.
Is this relationship facultative or obligate?
Why are conservationists concerned about climate change?
Name two more environmental stresses that may affect coral
reefs.
(1)
(1)
(2)
Commensalism
Commensalism is an interaction between organisms in which one
organism (the commensal) benefits and the other organism is
unaffected.
Question 1
‘Barnacles are a member of the Crustacean subphylum closely related to
crabs and lobsters. They are sedentary and will attach themselves to
hard surfaces where they filter the water for food. Certain commensal
species will live on crabs, turtles and even whales. ’
(a)
(b)
(c)
What benefit do the barnacles gain by living on a host?
Why may it be difficult to prove commensalism?
Is this an example of ectosymbiosis or endosymbiosis?
(2)
(1)
(1)
Additional questions
Question 1
‘Coral reefs are often referred to as ‘the cleaning stations’ of the oceans.
They are home to animals such as cleaner shrimps and cleaner wrasse. These
organisms remove parasites from ‘clients’ visiti ng the stations and often enter
the mouths of otherwise carnivorous species.’
(a)
(b)
What kind of symbiotic relationship if this an example of?
Why do you think this?
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(1)
(2)
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STUDENT MATERIALS
Question 2
Fill in the grid using ‘benefits’, ‘negatively affected’ or ‘unaffected’ to show
the effect on each organism in the relationship.
Relationship
Effect on organism 1
Effect on organism 2
Parasitism
Mutualism
Commensalism
Question 3
‘Many fish go through life with at least a low level of intestinal or stomach
worm infection with no effect on their health.’
(a)
(b)
What symbiotic relationship is this be an example of?
Do you think this relationship would remain the same if the host
became ill? What would it become and why?
(1)
(2)
Question 4
‘Sea anemones often inhabit shells of hermit crabs. In one study predators of
hermit crabs were presented with hermit crabs either with or without
associated sea anemones. After 12 trials with and 12 trials without the results
are shown below.’
(a)
(b)
Describe the trend of the results.
If sea anemones are filter feeders what kind of symbiotic
relationship do you think this association represents? Why?
Rejection Rate of Hermit Crab by Predator
9
8
Number of Rejections
7
6
5
4
3
2
1
0
With anemone
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Without anemone
(2)
(2)
STUDENT MATERIALS
References
Lehnert, K., Raga, J.A. and Siebert, U. (2007) Parasites in harbour seals
(Phoca vitulina) from the German Wadden Sea between two Phocine
Distemper Virus epidemics. Helgoland Marine Research, 61, 230–245.
McLean, R.B. and Mariscal, R.N. (1973) Protection of a hermit crab by its
symbiotic sea anemone Calliactis tricolour. Cellular and Molecular Life
Sciences, 29, 128–130.
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Solutions
Activity 5: Symbiosis revision
1.
Explain the term ‘symbiosis’.
Symbiosis is the relationship between organisms of different species
that show an intimate association with each other. Symbiotic
relationships provide at least one of the participating species with a
nutritional advantage. With symbiosis (as with predation) co -evolution
occurs and the species become closely adapted to each other.
2.
Define the term ‘parasitism’.
Parasitism is a biotic interaction that is beneficial to one species (the
parasite) and detrimental to the other (the host). The parasite lives on or
in the host and obtains its nutrition from the host.
3.
Why is it necessary for a parasite to keep its host alive?
To secure a supply of food.
4.
Explain how parasites and their hosts interact to maintain a stable
relationship.
There is a balance between the damage done by a parasite and the
defences which the host has evolved, which creates a stable
relationship.
5.
Describe the three ways that parasites can be transmitted.
Direct contact (fleas jump from one individual to another, the cold virus
is spread by coughs and sneezes).
Resistant stages (released into the environment and hatch out when
eaten by the host).
Secondary hosts (vectors) (transmit and devel op the infectious stage, eg
the mosquito is the vector for the malaria organism Plasmodium) .
6.
Describe, in general, the structure of most parasitic cycles.
A parasite feeds on the primary host, grows, develops and uses the
secondary host to secure widespread dispersal. Often the secondary host
is required to complete the lifecycle of the parasite before it can move
on to infect another (primary) host.
7.
Many parasites have resistant larval forms incorporated into their
lifecycles. Suggest a reason for this.
Resistant larval forms allow parasites to survive unfavourable
environmental conditions for periods of time until the conditions
change. An example is the larvae of the liver fluke , which survive in an
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STUDENT MATERIALS
encysted form (inside a cyst) as long as water is ava ilable (eg in a
pond).
8.
Explain, in evolutionary terms, how most parasites have become
host specific.
This has arisen due to the co-evolution of the parasite and the host, with
the relationship evolving for the best survival advantage of both, eg
parasitic infection results in an immune reaction by the host to lessen
the effect of the parasite; the parasite then adapts further to counter the
effect of the host’s immune reaction. The host then evolves a more
specific response and so on. As parasitic infection and host response
become more specialised, co-evolution results in increased host
specificity.
9.
Describe the phenomenon of mutualism.
Mutualism is the biotic interaction between two organisms of different
species where both organisms benefit. Both specie s have developed
adaptations to help them to coexist.
10.
Describe the relationships that exist between the following
organisms:
(a)
fungi and algae in lichens
(Note: Eukaryotes are classified into four kingdoms: animals,
plants, fungi and protists. Protists are unicellular organisms, eg
Amoeba and Paramecium and unicellular algae (algae used to be
classified as plants but now belong to the protists) .
Lichen is made up of an alga and a fungus in close association.
The alga photosynthesises and provides the fungus with
carbohydrate. The fungus provides the alga with protection,
support, nutrients (minerals) and CO 2 as the algal cells are found
inside the fungal threads (hyphae). The fungus also provides
water for the alga.
(b)
corals and algae
Corals and giant clams have algae inside and between their cells.
As the algae provide them with an energy source, corals can live
in nutrient poor water. The algae are provided with protection,
nutrients (minerals) and access to light.
(c)
cleaner shrimp and fish
Cleaner shrimp and grouper fish have evolved a mutualistic
relationship: the grouper fish allows the cleaner shrimp to remove
LIVING TOGETHER (H, BIOLOGY)
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STUDENT MATERIALS
scraps of food trapped between its teeth – a free lunch for the
cleaner shrimp and dental hygiene for the grouper fish.
Shrimp also remove ectoparasites (as food) from fish such as the
coral fish.
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LIVING TOGETHER (H, BIOLOGY)
© Learning and Teaching Scotland 2011