Populations in ecosystems

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  • Created by: hiddengem
  • Created on: 29-10-17 21:56
What is a niche?
the role of an organism in its environment, where it eats and what it does there including all the abitoic and biotic conditions requred for the organism to survive and reproduce.
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what happens when two organisms try to occupy the same niche?
They will compete with eachother and one species will be more successful and will outcompete the other. Competitive exclusion principle
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What is population size?
the total number of organisms of one species in a habitat
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what is the carrying capacity?
the maximum stable population size of species that an ecosystem can support
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What is an abiotic factor and list them?
the non living components of the environment , temperature, light intensity , PH, water and humidity
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what factors affect population size?
birth rate, death rate, immigration, emigration
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what are the formulas for population growth and percentage population growth rate ?
population growth =(births+immigration) - (deaths+emigration) %population growth rate= population change/population at start x100
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What are the three types of populations?
stable population- birth and death rate balanced , increasing population- high birth rate + immigration , decreasing population- low birth rate + emmigration
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What is intraspecific competition?
when individuals of the same species compete with eachother for the same resources. The availability of the resources determines the size of population.
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During intraspecific competition when does the population increase and decrease?
population increases when resources are plentiful, but this means more species competing for resources. Population decreases when resources are limited but a smaller population means less competition so more growth and reproduction.
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what is interspecific competition is ?
When individuals of different species compete with each other for the same resources.
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What does interspecific competition result in?
less resources , so limited amount of food so population size will decrease as less energy for growth and reproduction. The population of the better adapted species will increase whilst the other decreases.
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What is selection pressure?
When individuals who are able to escape predators or withstand disease/climate change are more likely to survive and reproduce, the population then evolves to be better adapted to the conditions
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What are the two types of quadrats?
frame quadrat- frame divided into a grid of smaller squares. Point quadrat- horizontal bar with 10 holes where a pin can be dropped
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How do you decide the size of quadrat and when should you use many small quadrats?
Nesting which is when you use different sized quadrats and count the number of species.When the population of a species id not evenly distributed throughout the area
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Why is it better to use a large sample of quadrats?
to give more reliable and representative results and so you can carry out statistical tests
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How do you carry out random sampling?
Divide an area into a grid, could be done using two long tape measures, obtain coordinates using a random number generator and place quadrat at intersection of coordinates and record the species within it
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Why should you do repeats?
it reduces the likelihood that your results are due to chance, to give a more reliable and representative estimate of the area and allow statistical analysis to be carried out.
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When is systematic sampling (transect) used?
when there is an environmental gradient/ a gradual change in the community of the pland or animal, to show the stages of succession
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What are the two ways a transect is used?
In a line transect the organisms touching the string are recorded. In a belt transect quadrats are placed along the transect at regular intervals.
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What is abundance?
the number of individuals of a species within a given area?
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What is frequency , how is it measured and when is it useful ?
the likelihood of a particular species occuring in a quadrat. Record the number of quadrats the species occurred in and put it over the total number of quadrats. Useful when individual species are hard to identify.
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What is percentage cover, how is it measured and when is it useful?
The percentage area of the quadrat covered by a particular species.count how many squares the species is present in over total number of squares. useful when it is difficult to identify individual species or species is highly abundant in the area
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how is density measured ?
count the number of individuals of each species in a quadrat, then divide by the area of the quadrat.
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How is mark, release , recapture carried out ?
capture a sample of species, mark them in a harmless way, release them back into their habitat and wait some time then take second sample from same population, count how many in the second sample and how many are marked.
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How do you work out estimated population size?
(number of individuals caught in first sample x number of individuals caught in 2nd sample)/ number of marked individuals recaptured
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What assumptions are made during mark release recapture method?
animals mix with population evenly, randomly, no massive changes due to births,deaths migration, marking doesnt affect survival and doesnt come off. ratio of marked to unmarked in sample same as in population as a whole
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What is succession?
the process by which a community changes over time, where organisms affect the environment making it less suitable for themselves and more suitable for the next dominating species
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What is the difference between primary and secondary succession?
Primary happens on land that has been newly formed where theres no soil. Secondary happens on land thats been cleared of all plants but soil remains
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Describe the features of ecological succession
colonisation by pioneer species, death/decomposition of pioneer species creating soil, change in environment , new species colonise, increase in number of species+ living material/niches/nutrient availability, more stable conditions climax community
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What features do pioneer species have that makes them suitable for colonisation?
they can asexually reproduce, they produce wind dispersed seeds, they can photosynthesise using light so dont need food, they can get nitrogen from the air, they can tolerate extreme conditions
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what is conservation?
the protection and management of ecosystems so the earths natural resources can be used in the future
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What are the reasons for conservation?
to maintain our planet, to coexist with other species, tourism, aesthetic reasons, undiscovered benefits, to maintain genetic diversity for future breeding programmes
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What are the ways to manage succession?
grazing, fires, using seed banks, legal measures like fishing quotas, protected areas, endangered species in captivity,
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Other cards in this set

Card 2

Front

what happens when two organisms try to occupy the same niche?

Back

They will compete with eachother and one species will be more successful and will outcompete the other. Competitive exclusion principle

Card 3

Front

What is population size?

Back

Preview of the front of card 3

Card 4

Front

what is the carrying capacity?

Back

Preview of the front of card 4

Card 5

Front

What is an abiotic factor and list them?

Back

Preview of the front of card 5
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