Life processes in the biosphere Flashcards
How do species become better adapted to habitats?
Random mutation, natural selection (evolution)
What abiotic factors affect species distribution?
Light, pH, water and mineral nutrients
What biotic factors affect species distribution?
Food supply, pollination, seed dispersal and disease
What is a taxon?
A taxonomic group
What is an ecological niche?
The role an organism plays in its habitat
What is a population?
A group of one species occupying a defined area
What is a biome?
A large geographical region with specific climatic conditions within which a unique community of species lives
What is ecological succession?
The process of change in the species structure of an ecological community over time
What are the stages of ecological succession?
A ‘pioneer’ species of extremophiles colonises, the population grows and changes the habitat, making it more suitable for other species and this continues until the climax community develops
What is the climax community?
The final species to colonise that remains dominant unless the climate changes
How do temperature extremes change during ecological succession?
High to low
How does water availability change during ecological succession?
Variable to reliable
How do light levels change during ecological succession?
High to low
How does nutrient availability change during ecological succession?
Low to high
How do rate of change change during ecological succession?
Rapid to slow
How does main pollination method change during ecological succession?
Wind pollination to insect pollination
How does main seed dispersal method change during ecological succession?
Wind dispersal to animal dispersal
How does the importance of inter-species relationship change during ecological succession?
Low to high
How does biomass change during ecological succession?
Low to high
How does biodiversity change during ecological succession?
Low to high
What are the critical determinants of a biome?
Temperature and rainfall
What is a sere?
The conditions under which the first stages of ecological succession occurs
What are the three seres?
Hydrosere
Lithosere
Psammosere (sand)
What are the stages of hydrosere?
Pioneer species includes algae and water floating plants
Larger plants colonise in shallow waters
Rooted plants colonise
Marsh plants colonise the margins
Terrestrial plants as soil builds up, water content drops and conditions become more aerobic
Terrestrial plants out compete the water plants and they die out
How are spores and seeds brought into the freshwater?
Birds, such as herons and ducks, and flying incests, such as water beetles and pond skaters
How can rooted plants colonise?
As other plants die naturally, they leave dead organic matter, that and sediment and soil build up
What trees survive in waterlogged soils?
Alder and willow
What are the stages of lithosere?
Simple autotrophs colonise, mosses colonise, grasses and ferns colonise, layers of soil start to build up, larger plants and trees start to colonise
What are the initial conditions of the lithosere?
Bare rock, created by a cliff fall, the retreat of a glacier or volcanic eruption, which is under extreme temperatures with limited water availability and no soil
What autotrophs first colonise the lithosere?
Lichens and algae
What trees have wind-blown seeds?
Birch
What trees have animal dispersed seeds?
Oak and beech
What are the initial conditions of the psammosere?
Minimal plant nutrients, rapid drainage and moving sand make root anchorage difficult
What happens when plants succeed in colonising the psammosere?
The sand is stabilised, nutrient supplies increase, organic matter builds up and water becomes more available
What is plagioclimax?
The new climax community created under a change of conditions by humans
What human activities disturb climax communities?
Ploughing, tree felling and burning
What is secondary succession?
When the community is destroyed by human activities and the original species recolonise the area and the climax community is eventually re-established
When does secondary succession occur?
When the original vegetation is destroyed by forest fires, floods, storms, deforestation, grazing and mowing
How do extreme environments affect species diversity?
Often low
At what rate are new species being discovered?
20,000 per year
How many species are currently named?
2 million
How many species are estimated?
5 to 100 million
What are population dynamics?
The processes that cause populations to change in size and structure
What impacts the death rate of species?
Disease, drought, predation and shortage of foods
What are r-selected species?
Species that can respond to low survival rates, they reach sexual maturity quickly and produce many offspring
What are some examples of r-selected species?
Mice, locusts and greenflies
What are k-selected species?
Species that recover slowly from a decline in population
What are some examples of k-selected species?
Wales, elephants and rhinos
What is the ecological importance of high species diversity in an ecosystem?
Greater ecological stability, faster recovery from disruption, more resilience to change, because there is a greater range of niches, more complex food web and more species interactions
What is the maximum sustainable yield?
Estimate of the greatest exploitation that is possible, without causing unsustainable long-term decline in population
What needs to be known to calculate the maximum sustainable yield?
Death rate, population increase rate, number of offspring, population size and growth rate of individual
What density independant factors affect mortality rates?
Drought, flood and volcanic eruption
What density dependant factors affect mortality rates?
Food supply, disease and space
What is inter specific competition?
Different species compete for the same resource, they may live in harmony or one of the species may take over
What is intra specific competition?
Competition between the same species for a resource
What is an example of inter specific competition?
Rainforest monkeys on the fig tree
What is an example of intra specific competition?
Golden eagles on a deer carcass
What resources can organisms compete over?
Light, nutrients, breeding sites, nesting sites, mates and food
What is carrying capacity?
The greatest population that an area can support indefinitely without damaging or over-exploiting the environment
What happens as the population of prey fluctuates?
The predator population follows the same pattern, as prey increases theres more food so the predator population increases, as prey decreases then predators decrease due to food shortages
How does grazing maintain plagioclimax communities?
Prevents establishment of taller plants, produces bare ground for germination of wildflowers,
How does mowing maintain plagioclimax communities?
Removes vegetation that would be removed by grazing, also thorny, stinging or bad-tasting plants
How does burning maintain plagioclimax communities?
Removes vegetation that would not be eaten by animals and creates open, unshaded areas for the growth of young heather plants
What is the management practice for lowland heathland?
Grazing or burning
What is the management practice for hay meadow?
Mowing
What is the management practice for wet meadow?
Grazing
What is the management practice for arable field?
Ploughing
What is the management practice for garden lawn?
Mowing
What is the management practice for coppiced woodland?
Cutting every 3 to 30 years
What is the management practice for upland moorland?
Grazing or burning
What is the management practice for reed beds?
Cutting
What does the sigmoidal growth curve show?
The growth rate of a population as it approaches its carrying capacity
What is the shape of a sigmoidal growth curve?
S shaped, like the oxygen dissociation curve
Why is there a lag phase on the sigmoidal growth curve?
There a few individuals to reproduce
Why is there a logarithmic phase on the sigmoidal growth curve?
The population grows rapidly as birth rate is higher than death rate, most deaths are caused by density independent factors
Why is there a stable and fluctuating phase on the sigmoidal growth curve?
Birth rate roughly equals the death rate, density dependent factors stop population growth
What are methods of artificial population control?
Culling, introduction of predator species, captive breeding
What is the biosphere?
All of the planet that is inhabited by living organisms, including the land surface, soil, water and atmosphere
