Week 22 Flashcards
What are the levels of organisation and interaction?
Individuals
Populations
Biological Communities
What does the organisation individuals involve?
◦Level at which natural selection acts
Smallest unit to consider and they are often genetically unique.
They have adapted or have particular sets of requirements which relate to their fitness. This is the level at which NS operate
– often genetically unique (unless clones asexual reproduction or identical twins) – so unique in environmental adaptations and requirements - > fitness
What does the organisation populations involve?
◦Groups of individuals of same species
There will be genetic variation within the population but essentially they all have similar requirements and thinking about the niche concept that you looked at you can see that there’s a range of adaptations, perhaps to temperature, and that reflects the range of genetic make up within the population.
Populations comprised of individuals – genetic variation > set of requirements and for each a range of conditions in which they can grow, survive and reproduce. Remember niche and Hutchinson’s concept of this as an n-dimensional hypervolume
What does the organisation
Biological Communities
involve?
◦ Assemblage of species populations
Are actually a particular mix of species occurring together in a given area.
– the mix of species plants, animals, fungi etc – a population of each - that are present in an area. And we can think of each of those species as being comprised of a population. Which species and their abundance will be determined by the environmental conditions that operate in the area and the interactions between those species.
In conservation biology how do we classify organisms?
In conservation biology we classify communities into different types – most often by the plant components, so we can recognise them when we see them again (perhaps in a different location), by doing this it means we could perhaps work out how much of a particular community we have and by understanding their dynamics, manage appropriately to conserve them. We also want to characterise them so we can understand how to manage them.
At the highest level, communities might be classed as
major biomes.
What are some examples of major biomes?
We can ID major biomes like Tropical Rain Forest, to more local communities like heathland and grasslands.
What is the highest level of organisation?
Ecosystems – Tansley (1935)
What are aspects of an ecosystem?
◦Self-contained unit ◦Biological community + abiotic environment- and how these interact ◦Trophic Levels and Energy flows ◦Autotrophs to top predators ◦Biogeochemical cycles- Nutrients e.g. nitrogen, phosphorus -
How do nutrients move in biogeochemical cycles?
movement of nutrients throughout the systems. Initially, they are probably going to be taken up by the autotrophs at the bottom of the food chain and then through them being consumed and so on up through the trophic levels. We have the movement of those nutrients and along the way we have defecation , remains being left behind and they will be broken down by the decomposer community so the nutrients can be cycled again. Depending on the nutrients there might also be cycling in the atmosphere or in water and in the case of nitrogen we have fixation by bacteria.
What does a trophic level pyramid show?
We can see that in the lower part of the pyramid we have autotrophs which are the primary producers that capture energy most often from the sun converted into carbohydrates and other useful products and they are then fed upon by herbivores . Above that we have the secondary consumer and then above that you have top carnivores. So we classify species in their trophic levels according to their main form of nutrition.
What is the difference between intraspecific and interspecific?
Intraspecific (between organisms of the same species) and interspecific (between organisms of different species) interactions.
Recap – inter and intra specific competition – we have both forms of interaction – most obviously in competition but others too e.g. predation (cannibalism)
There are different ways interactions happen, what are these?
Direct
Indirect
What is a direct biological interaction?
Direct – physical contact between the two organisms interacting e.g. predation, herbivory etc – whole spectrum.
e.g. consumption of another individual (predation,herbivory, cannibalism), to mutual benefit (mutualism), and everything between
What is indirect biological interaction?
e.g by shared resources, common enemies.
Indirect - where there’s a shared resource and they never come in direct contact. But by their presence they are sort of interfering with each other. E.g. Leaf miner and plant direct but also indirect between miners as they may share resources but never physically have direct contact. We’ll develop these points later.
What other aspects are there to biological interactions?
Classify benefit / harm in terms of fitness to both species-
Level of benefit or harm continuous, not discrete-
Interactions not always static
Classify benefit / harm in terms of fitness to both species-
we can classify them in terms of whether they are of benefit or harm to the organisms concerned. And in particular we are looking at how the outcomes affect fitness, the survival and reproduction of those organisms.
How outcomes affect fitness – survival and reproduction.
Level of benefit or harm continuous, not discrete-
the benefit or harm could be discrete , it could be an organism being completely consumed by another and so it dies. It also thought to be continuous, so it could be that a herbivore partially grazes a plant and the plant survives but it has lost some material. Or it could be that a predator gets a meal one day but not another and still survives.
even can be a big Continuous range – missing meals to kill/eat. Similarly with the benefits.
Interactions not always static-
they may change over time in intensity or they may change in terms of at what point in the lift history an organism is affected or more affected by an interaction with another organism.
will change as environment changes over time.
We can classify interactions according to whether
the organisms concerned benefit or are harmed or unaffected and first of all its worth trying to think about just two organisms interacting with each other.
Describe these interactions with their signs and effects:
1) Mutualism
2) Commensalism
3) Competition
4) Antagonism
1) +/+ mutualism – both organisms benefit from interaction- where both organisms through the interaction benefit.
2) +/0 commensalism- one organism benefits but another is unaffected.
3) -/- competition- where both organisms in the interaction are affected negatively.
4) +/- antagonistic- one benefits and one is disadvantaged .
What are two types of interaction that are not really discussed?
0/- amensalism- one is unaffected and the other harmed.
0/0 neutralism- affect on neither organism
Won’t talk about – try to research examples. Probably more of the former. Neutralism hard to imagine there would ever be no effect on either partner in ain interaction.
What is mutualism?
2+ species derive a mutual benefit.
Looking at each in turn. MUTUALISM – both parties receive a benefit from the interaction. Two or more species which derive a mutual benefit from their interaction.
What is an example of mutalism?
E.g. cleaner fish, birds removing parasites, nitrogen fixation by bacteria, photosynthesis by algae sheltered by coral
What might mutalism cause one or both species to be?
obligate,
What does it mean when the species are obligate?
i.e. cannot survive in the short or long term without the other species because they dependent on each other.
One or both organism could be operating in an obligate way i.e. they can’t survive for long without the partner organism in the short or long term
What might happen when the species become obligate?
That usually means some kind of close physical association between mutualistic partners – and we usually term such situations symbiotic relationships ‘symbionts’. Can make further distinctions e.g. if one partner organism lives entirely inside the other - a host– ‘endosymbiosis’ e.g. Algae sheltering within a coral – an extreme example of symbiosis. Alternatively we can have less specific – more generalist - and less intimate interactions e.g. cleaner shrimp feeding on parasites or dead skin on a moray eel or other spp. More a mutualism – both parties can survive without the other…
Although we can classify some interactions, sometimes it’s a question of
degree and some could be classified in more than one way.
What is an example of a really important interaction?
Some can be really important interactions e.g. pollination – insect – plant interaction. Easy example to remember especially at Bristol where so much work has been done on these interactions.
What is Commensalism?
One organism benefits by interacting with another organism which is not affected
But close interaction of two organisms unlikely to be completely neutral
What is an example of commensalism?
E.g. epiphytes may intercept nutrients that otherwise would go to host plant; may shade host tree.
Quite hard to find good examples. Ramora –attaches to another organism e.g. shark. Shark messy eater. Is shark disadvantaged to a small amount? Less streamlined? Slightly more energy expended. Another is sea anemone attached to the shell of a hermit crab – again, messy eater of dead animal remains. Epiphytes on trees – tropical orchids, lichens – shading effect? Some slight cost? probably
What is competition?
“Competition is an interaction between individuals brought about by a shared requirement for a resource in limited supply and leading to a reduction in the survivorship, growth and /or reproduction in the competing individuals concerned.”
so the overall impact is on ecological fitness. Harks back to the niche concept that includes both physical requirements and food resources. Outcome is a range of negative impacts on the organisms that are competing for limited resources.
Will look at several examples to illustrate effects – some obvious, some more subtle.
