Key Area 5: Symbiosis Unit 3: Sustainability and Interdependence.
-
Upload
felix-shields -
Category
Documents
-
view
219 -
download
0
Transcript of Key Area 5: Symbiosis Unit 3: Sustainability and Interdependence.
Symbiosis• Symbiosis is the close relationship
between two different species that live in direct contact with each other.
• e.g. the relationship between nitrogen fixing bacteria (Rhizobia) and leguminous plant roost (peas, beans and clover)
CfE Higher BiologySustainability
and Interdependenc
e
Symbiosis• There are two categories of
symbiosis:
CfE Higher BiologySustainability
and Interdependenc
e
Symbiosis
Parasitism Mutualism
(Find out about commensalism)
Parasitism
CfE Higher BiologySustainability
and Interdependenc
e
• Parasitism is a relationship between two organisms where only one organism benefits.
• A parasite lives on another organism called the host.
• The parasite obtains nutrition and food from the host which benefits the parasite.
• The host does not receive any benefit but is harmed or killed by the parasite.
Parasitism
CfE Higher BiologySustainability
and Interdependenc
e
• Some parasites are ectoparasites and live on the outer skin of the host.
• e.g. ticks
• Leeches
fleas
Parasitism
CfE Higher BiologySustainability
and Interdependenc
e
• Some parasites are endoparasites and live inside the host.
• e.g. tapeworm, malarial Plasmodium
Parasitism
CfE Higher BiologySustainability
and Interdependenc
e
• Parasites can be obligate or facultative.
• An obligate parasite is one that can only survive with a host.
• A facultative parasite is one that can survive with or without a host.
• Only poor parasites will kill their host as this is not to their advantage, especially for those that are obligate.
Parasitism
CfE Higher BiologySustainability
and Interdependenc
e
• A balance must exist between parasitic damage and the defence of the host.
• A relatively stable relationship must exist between the two.
• As the parasite and the host coexist and evolve, the disease the parasite causes may occur in a cycle.
Parasitism
CfE Higher BiologySustainability
and Interdependenc
e
• Parasites can be transmitted to new hosts by a variety of mechanisms:– Direct contact– Releasing resistant stages– Using vectors
CfE Higher BiologySustainability
and Interdependenc
e
Method
Example(s) of parasite
Notes on transmission (e.g. description /advantages/disadvantages
Direct ContactResistant Stages
Vectors
RingwormRabiesHIVSpores
and endospores in fungi and bacteria
Allows the parasite to survive in extreme conditions
MalariaSomething else carries the disease between infected individual and new host. Malaria uses the mosquito as a vector
Research a specific example
Primary and Secondary hosts
CfE Higher BiologySustainability
and Interdependenc
e
• A primary host is used in a parasitic direct life cycle.
• Only one species of host is used in this case.
• A secondary host is a host that a parasite uses for a short time along with a primary host to ensure that the parasitic life cycle can be completed.
• This is an indirect life cycle.
Secondary hosts
CfE Higher BiologySustainability
and Interdependenc
e
• A tapeworm is a parasite that uses a secondary life cycle.– Parasite –
tapeworm– Primary
host - human
– Secondary host - pig
Primary and Secondary hosts
CfE Higher BiologySustainability
and Interdependenc
e
• Trypanosoma are parasites that use a secondary host– Parasite –
trypanosome– Primary host
– tsetse fly– Secondary
host - human
Mutualism
CfE Higher BiologySustainability
and Interdependenc
e
• Mutualism is a specialist relationship between two organisms where both organisms benefit.
• e.g. lichens are composed of fungus and algae in a beneficial relationship
Mutualism
CfE Higher BiologySustainability
and Interdependenc
e
• e.g. herbivores have special cellulose digesting microorganisms in their stomachs.
• As we depend on ruminants (sheep, cattle) for food and products this symbiosis is of great economic importance
Leguminous plants and Rhizobium bacteria
CfE Higher BiologySustainability
and Interdependenc
e
• Rhizobium bacteria live freely in the soil.
• They are able to infect the roots of leguminous plants and form nodules.
• Inside the nodules the bacteria obtain energy from their host and supply nitrogen compounds in return.
Fungi and Algae (lichens)
CfE Higher BiologySustainability
and Interdependenc
e
• Lichens are able to colonise areas where other plants are unable to grow.
• The fungal part of the lichen produces tough cellulose walls and secretes mineral digesting chemicals while receiving carbohydrate.
• The algal part of the lichen photosynthesises and received protection and essential minerals
Herbivores and gut bacteria
CfE Higher BiologySustainability
and Interdependenc
e
• Herbivores cannot produce cellulose digesting enzymes.
• Bacteria which can do this are found in the alimentary tract of herbivores.
• These bacteria receive food and shelter and aid plant digestion.
Ants and Aphids
CfE Higher BiologySustainability
and Interdependenc
e
• Some species of ant ‘farm’ aphids.• They move them from plant to plant
and protect them from predators.• In return the aphids secrete a sugary
liquid that the ants drink.
Terrestrial plants and pollinating animals
CfE Higher BiologySustainability
and Interdependenc
e
• Many plants have evolved special flower shapes which allow only one kind of animal near them.
• The animal depends on the nectar it receives as a reward for its visit.
• The plant depends on the animal to transport its pollen between flowers.