Lecture 5 JD Flashcards
Facilitation
facilitative or positive biotic interactions are encounters between organism that benefits at least one of the participants and cause harm to neither
What are the two types of facilitation?
- commensalism
- mutualism
What is commensalism?
an association between two organisms in which one benefits and the other derives neither benefit nor harm
What are the 3 types of commensalism?
- phoresy
- inquilinism
- metabiosis
Phoresy
involves animal attaching to another animal exclusively for transport
- e.g. sloth moths are found in fur of sloths as the sloths provide transport to the moths
Inquilinism
an association between members of two different species in which one, the inquiline, lives commensally on or in the other, the host, or inside the hosts home
Metabiosis
a form of commensalism in which one organism creates or prepares a suitable environment for another
What is mutualism?
a relationship in which organisms of different species interact to their mutual benefit (usually involves the direct exchange of goods or services)
What are the 4 types of mutualism?
- defensive
- resource-based
- dispersive
- symbiosis
Defensive
one species provides protection from predators
Resource-based
both species supply resources (food) to each other
Dispersive
interactions in which species receives food in return for transporting the pollen or seeds of its partner
Symbiosis
an intimate association between two species typically to the advantage of both. often a physically close and long-term biological interaction
Example of symbiosis
lichens
- nutritionally specialised fungi (the mycobiont component) that have escaped from their normal way of life into a mutualistic association with a photobiont
What is the main photobiont of lichens and what does it provide?
in 90% of lichens, the photobiont is an alga, and it provides carbon compounds to the mycobiont through photosynthesis
What is another photobiont of lichens and what does it provide?
in some cases the photobiont is a cyanobacterium which may provide fixed nitrogen to thee association
Mycorrhizae
plants and fungi develop mutually beneficial associations in the soil. they are often essential to the survival of the host plant (obligate vs facultative)
Mutualistic mycorrhizal associations between fungi and plants
vascular plants provide carbohydrate energy to fungi (as they have no chloroplasts) in return, fungi forage for trace elements and essential nutrients throughout nearby soil. the exchange occurs at the interface (which is often complex and extensive) between the two organisms.
What are 2 dominant types of mycorrhizae?
- endomycorrhizae
- ectomycorrhizae (EM)
Endomycorrhizae
- vesicular arbuscular mycorrhizae (VAM)
- VAM mutualisms are present in 80% of angiosperm plants
- they fungal hyphae penetrate the host plant tissue, forming two kinds of structures: vesicles and arbuscules
What do vesicles play a role in?
storage
What do arbuscules facilitate?
the transfer of nutrients between the mutualist partners and comprise a complex dual-membrane between hyphae and the plant cell
Ectomycorrhizae (EM)
ectomycorrhizal fungal hyphae do not form any structures within the host tissue but instead penetrate between the cells to form a Hartig net, which are enclosed in a mantle or fungal sheath, which surrounds thee growing root tip
