Life Processes In The Biosphere Flashcards
What is the process of evolution?
Species becoming between adapted through processes that involve the production of new characteristics by random mutations
Followed by natural selection, which gives an increased chance of survival to better adapted individuals
Why is a population with a large gene pool more likely to survive environmental changes?
They will have a larger overall range of tolerance, and there is better chance some individuals will be adapted to the new conditions, although the non-adapted individuals would die, the survivors can breed and rebuild a population that is suited to the new conditions
How is the survival and distribution of species mainly controlled by abiotic factors?
Genetic diversity within the gene pool means that survival declines when conditions become less suitable and fewer individuals with the populations re still within their individual ranges of tolerance
- light
- pH
- water
- nutrients
Must also be adapted to the inter-species relationships involved with biotic factors
How can a the survival of a species depend on biotic factors?
- food supply
- seed dispersal
- pollination
- disease
What is the process of ecological succession?
- the first living organisms to colonise must be adapted to abiotic conditions which are more extreme from strong winds, brighter sunlight to more extreme temperatures = these are the pioneer species
- as time passes an populations increase, the pioneer species change the habitat and make it more suitable for species that were not able to survive before, the new colonisers may then outcompete the pioneer species which become less dominant
- the new colonised also change the conditions, making it suitable for more species to colonise
- as the changing abiotic conditions become less extreme the adaptations that are needed for survival are increasingly based on biotic factors and interspecies relationships
- the sequence of colonising, thriving and dieting out continues until a final community of species developed which remains dormant as long as the climate does not change
= these climax community
What is a sere?
The sequence of stage in ecological subscript during which an uncolonised habitat developed into the climax community, seres are often named after the conditions at the beginning of succession
What is a hydrosere and what happens in terms of ecologically succession?
When an area of freshwater is created it is usually quickly colonised by single-celled algae from soil
- birds such as herons and ducks and flying insects can bring n spores and seeds of algae, diatoms and plants
- lake edges start to be colonised
- as plants grow and die the lake gradually fills in with dead organic matter, allowing rooting plants to colonise the lake, emergent plants outcompeting the others
- as sediments fill the lake and open water recedes, aquatic species disappear, and much bigger plants and trees colones
- as transpiration by trees removed the water and the soil becomes drier, trees like oak will be able to colones, which create a dense canopy shaping other plants
- eventually the climax community will contain the biggest trees with other plants and animals living in, on or under them
What is the lithosere and what happens to it in terms of ecological succession?
The development of a community in bare rocks created by a cliff fall, retreat of a glacier or a volcanic eruption:
- conditions are very harsh
- pioneer species = lichens and algae
- conditions imposed as dead organic matter and rock fragments accumulate
- mosses and thin layers of soil build up allowing grasses and ferns to colonise
- more layers of soil for and the conditions become less extreme
- once pollinating insects become established flowering plants colonise and survive as pollination takes place
- once the soil is deep enough trees can colonise
What is the psammosere and what happens in terms of ecological succession
Involves ecological succession that’s starts on sand:
- plant nutrients are not readily available, drainage is rapid so water supplies are poor and moving sand makes it difficult for plants to establish a good root hold without being covered and killed
- as plants succeed in colonising, the sand is stabilised, nutrient supplies increase and organic matter builds up with water too
- eventually the sequence of changes in the community of species will establish the same climactic community that would have been produced by a hydrosere or lithosere
What is a plagioclimax?
Human active that deflects the climax community occurs regularly, so the natural climax community does not have time to reform and a new community of species develops.
What are some plagioclimax communities and how they are managed?
Lowland heathland = grazing or burning
Hay meadow = mowing
Wet meadow = grazing
Upland moorland = grazing or burning
Arable field = ploughing
Garden lawn = mowing
Coppiced woodland = felling at intervals of 8-20 years
Reed beds = mowing or cutting
What is secondary succession?
Human activities like felling, ploughing and burning can recreate the condition that were suitable for the species that colonised the area earlier in the sequence of ecological succession
- these species recolonise the area, if the habitats is left alone succession will continue and will eventually recreate the climax community
- this takes place more rapidly then primary succession because the soul does not have to developed and many seed will already be present so there are fewer delays caused by the time taken for species to colonise
How can Simpson’s diversity index be used to measure the biodiversity of an area?
N(N-1)
D = ————
Sum of n(n-1)
Where:
N = total number of organisms (all species)
n = total number of organism of an individual species
The higher the D value the higher the biodiveirty
How can you estimate the total number of species?
The past rate of discovery can be used as the basis for estimating the number, the gradual reduction in the rate of finding new species can be used to estimated the total number of species hat have nit yet been discovered and therefore the total number of species that exist
New species discovered = 20,000 per year
Current estimates for total number of species = 5-100million
Only 2 million have been named so far
What are population dynamics?
Involves the process that’s an cause populations to change in size and structure
- the number of individuals of a species that live in an area is controlled by the balance of factors which tend to increase of reduce the population
- the population will increase if the reproduction rate it high and the death rate is low, vice versa
What is birth rate in a population?
The maximum birth rate is determined by the natural ability of the species to reproduce
- evolution has produced birth rates for each species that are appropriate for the death rate
- species with lower changes of survival have higher birth rates
What is death rate in a population?
The death rate is controlled by environmental factors such as disease, drought, predation and shortage of food
What are r-selected species?
Respond rapidly to low survival rates
- reach sexual maturity quickly, produce many and can disperse widely
E.g. rabbits, mice, locusts and greenfly
What are k-selected species?
Recover slowly from a decline in population
- reach sexual maturity at an older age, produce few young but often live for a long time
- an increase in death rate caused by a change in the habitat or by human exploitation may cause a population crash
E.g. whales, elephants, rhinos
What is the MSY?
Maximum Sustainable Yield is an estimate of the greatest exploitation that is possible without causing unsustainable long-term population decline
Population = starting population + births + immigrants - deaths - emigrants
What are density dependent factors?
These include factors where the population density has no effect on the chances of survival of an individual e.g. drought, food, volcanic eruption
What are density dependent factors?
These include factor where the chances of an individuals survival is dependent of the population density of the species
- survival chances are usually higher when the population density is low and lower when the population density is high
E.g. food supply = intra-species competition for food is greatest in a large population
Disease = spreads more easily in a larger population
What is the carrying capacity?
The greatest population that an area can support indefinitely without damaging or over-exploiting the environment, the mortality rate in a population changes if the population size is above or below the carrying capacity, so that the population size changes back to the carrying capacity
What is the predator-prey populations relationship?
When prey population rises there is a lot of food available for the predators, so their population rises
The higher the predator population causes the prey population to decline, the low prey population creates a food shortage and the predator population declines and so on
