19.Populations And Ecosystems Flashcards
What is ecology
The study of inter relationships between organisms and their environment.
What are abiotic factors
Non living factors in the environment eg temp and rainfall
What are biotic factors
Living factors such as competition and predation
What are the two major processes within an ecosystem
Flow of energy through system
Cycling of elements within system
What’s a population
Group of individuals within a species that occupy the same habitat at same time and are able to interbreed
What is carrying capacity
Size of population that an ecosystem can support
The size of population can vary because of …
Effect of abiotic factors
Interactions between organisms
What do populations of different species that live and interact in particular place and time form
Community
What is a habitat
Place where organisms normally lives and is characterised by physical conditions and other types of organisms present.
What are micro habitats
The smaller units each with their own microclimate eg mud at bottom of stream for bloodworm
What’s a niche
It describes how an organism fits into the environment, referring to where it lives, and what it does there
What’s population size
The number of individuals in a population
What scale is used on the y axis when plotting growth curves
Log the number of bacteria
Why does light influence size of population
Ultimate source of energy for ecosystems, rate of photosynthesis increases as light intensity increases. Greater rate of photosynthesis faster plants grow, more seeds produced,carrying capacity greater. Then carrying capacity of animals that eat plants is potentially greater.
Why does pH influence population size
Affects enzyme action, further away from optimum populations get smaller
Why does water and humidity influence population size
Water is scarce and populations are small and consist of only those adapted to dry conditions.
Humidity affects transpiration rates in plants, and evaporation of water from animals bodies
What’s intraspecific competition
Competition between individuals of the same species for resources such as water, food etc
What does the availability of resources determine
The size of population
The greater the availability the larger the population
What’s interspecific competition
When individuals of different species compete for resources such as food light and water
One of the two sore cries will have a competitive advantage over the other and so this species will gradually grow while the other diminishes
What is the competitive exclusion principle
When different species compete for resources and one has a competitive advantage and the population grows while the other diminishes, and if conditions don’t change it results in removal of one species
“The species that uses the resources most effectively will ultimately eliminate the other”
How should you show how a factor influences size of population
Link it to birth rate and death rate,
Increase in food may not mean increase in birth rate but fewer individuals that are stronger and bigger, but it means more are likely to survive and increase probability of producing offspring
In nature why does the prey population rarely become extinct
There are many places to refugee, and environments across which populations spread are diverse, so prey can escape, or it’s harder to locate the prey
What’s the effect of predator-prey relation on population size
Predators eat prey-prey population lowers
Fewer prey more completion for predators
Predation population reduces as individuals unable to get substantial amount of food
Fewer predators, fewer prey eaten, prey populations increase
More prey available, predator populations increase
What’s selection pressure
The environmental force altering the frequency of alleles in a population
What is a point quadrate
Horizontal bar supported by two legs, at set intervals along bar are ten holes through which a pin can be dropped and each species the pin touches is recorded
What is a frame quadrant
Square frame 5 x 5 sections, the abundance of each species within quadrat is recorded
What are the three factors to consider when choosing the quadrants
Size of quadrat-how big organisms are, large number of small quadrants give more representative results if species not evenly distributed
Number of sample quadrat-the larger the sample the greater the sample and more reliable
Position of each quadrat- random sampling must be used
How to create a random sample for quadrat locations
Create co ordinate grid and throw dice for the locations
What is systematic sampling along belt transept
Start at a point, and put quadrat down and moved along it’s own length each time until you get to end of measuring tape.
Stages of succession are shown using belt transept
What is abundance
The number of individuals of a species in a given area
What are the ways of measuring abundance
Frequency - occur in 15/30 fo frequency occurrence is 50%, quick idea of general representation
Percentage cover - an estimate of area covered, useful if species is hard to count, data collected rapidly
What is the mark release recapture technique
Used on moving animals, a known number of organism caught and marked in some way, then released back into community. Some time later a given number of individuals are caught and the number of marked individuals is recorded.
What’s the equation for estimated population size
Total number in first sample x total number second sample
——————————————————————————
Number of marked individuals recaptured
What does the mark release recapture technique rely on
1-proportion of marked to unmarked is same proportion of marked to unmarked in population
2-marked from first release evenly distribute amongst remainder
3-population has definite boundary so no immigration into or out of pop
4-few if any deaths
5-marking isn’t toxic
6-mark isn’t lost or rubbed off
What is succession
When ecosystems are dynamic and they change day to day, sometimes slowly and sometimes rapidly.
Takes place in a series of stages, and at each stage, the new species colonise the area and these may change the environment.
The species may alter the environment in a way that makes it ….
1-Less suitable for the existing species, as a result the new species may out-compete the existing one and so take over given area
2-more suitable for other species with different adaptations as a result species may be outcompete by the better adapted new species
What is the first stage of succession
Colonisation of an inhospitable environment by organisms called pioneer species. They will make a pioneer community and often have features that suit them to colonisation
What are some features of pioneer species that allow them to colonise
- Asexual reproduction-rapidly multiply
- Vast Production of wind dispersed seeds or spores
- rapid termination of seeds don’t require dormancy
- ability to photosynthesise as light available but not food
- ability to fix nitrogen as soil has little or no nutrients
- tolerance to extreme conditions
What’s an example of a pioneer species
Lichens
What is the 2nd stage of succession
- The lichens would break down the rocks and when they die and decompose they release sufficient nutrients to support community of small plants
- mosses grow and continue to erosion and decay and release of nutrients
- soil builds up, organic material holds water, easier for other plants to grow
What’s the third stage of succession
- abiotic environment is less hostile so more suitable for organisms such as grasses or small flowering plants
- in turn shrubs and trees
- provides more sources of food for more stable communities
What is a climax community
When many species flourish and there is much biodiversity
Consists of animals and plants
What are the common features of any succession
- non living abiotic environment becomes less hostile
- greater number and variety of habits and niches
- increased biodiversity
- more complex food webs
- increased biomass
What factors determine which species is dominant of the community
The abiotic factors such as climate
What’s the other type of succession
Secondary succession - when land that’s already sustained life is suddenly altered, and may be result of land clearance for agriculture or forest fire, under goes quick succession as soil already exists and an influx of animals and plants.
What is conservation
Management of earths natural resources
Involves active intervention by humans to maintain ecosystems and biodiversity
What are the main reasons for conservation
- Personal to maintain our plant and life after
- ethical-other species occupied earth longer, should be allowed to coexist
- economic-living organisms big gene pool long term productivity is greater if ecosystems are maintained in their natural balanced state
- cultural and aesthetic-enrich our lives, adds interest to our days
What is one way in which succession is prevented
Moorland, grazing of sheep stops the land reaching its climax community so prevents the natural succession into deciduous woodland.
