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21 Cards in this Set
- Front
- Back
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what factors affect population size |
•energy intensity •biological cycles(vary mineral availability) •succession- changes habitats •species come and go •birth rate (natality) -increase •death rate(mortality)-decrease •immigration-increase •emigration-decrease |
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what is a population |
an interbreeding group of organisms of the same species occupying a particular habitat |
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what are equilibrium species |
species that control their population by competition rather than by reproduction and dispersal usual pattern of growth is a sigmoid S-shaped curve (one-step growth curve) |
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what are fugitive species |
species that are poor at competition rely on large capacity for reproduction and dispersal to increase their numbers (invade environments rapidly) |
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what is environmental resistance |
environmental factors that slow down population growth |
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what are biotic factors give examples |
a part of the environment of an organism that is living e.g predators or pathogens |
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what are abiotic factors give examples |
a part of the environment of an organism that is non-living e.g air temperature or oxygen availability |
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what is carrying capacity |
the maximum number around which a population fluctuates within a given environment |
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what is the lag phase |
a period of slow population growth e.g. time it takes for individuals to reach sexual maturity |
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what is the exponential(log) phase |
numbers increase so individuals become more available for mating as long as there's no limiting factors this rate drops due to environmental resistance (less food, less space, more waste) gradient decreases |
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what is the stationary phase |
when birth rate = death rate population is at its maximum size- carrying capacity for that environment fluctuates due to environmental changes |
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what is the death phase |
when death rate>birth rate factors slowing population growth become more significant population decreases |
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describe the predictor-prey relationship (negative feedback) |
•lots of predators causes the prey population to decrease •this means there isn't enough food for predators so predator population decreases •this means there is less predation for the prey so prey population increases •this means there's more food for the predators so predator population increases - the cycle repeats about every 10 years |
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describe the one-step growth curve for bacteria |
1. lag phase: can last from a few minutes to several days
2. exponential/log phase: bacteria cells divide at a constant rate and the population doubles per unit time - cell numbers increase logarithmically(log phase) -environmental resistance for bacteria in a flask: available food, overcrowding, competition, toxic waste
3.birth rate=death rate
4. death rate>birth rate |
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what are density dependent factors |
•factors that affect a greater proportion of the population of the population is denser •they are biotic factors like disease, parasitism, food supply |
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what are density independent factors |
•factors which affects don't depend on population density •abiotic factors such as temperature, floods, fire, insecticides |
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how is the population size regulated by negative feedback |
•if population rises above a set point, a density-dependent factor increases mortality or decreases breeding so the population declines •if the population falls below a set point, environmental resistance is temporarily received so the population rises again |
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how is a new habitat assessed |
•physical features (soul type or temp) are assessed first as they determine the number and types of plant living there • Soil derived from granite bedrock is more acid than derived from salt • If rainfall is high throughout the year tree ferns could be found, if it's dry cactuses may be there •cold habitats might only support a few species but warm habitats can support many types of plant |
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what is abundance |
• The abundance in a species is a measure of how many individuals exist in a habitat |
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how is animal abundance assessed |
•capture-mark-recapture experiments •kick sampling in a stream and counting aquatic invertebrates |
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how is the abundance of s plant measured |
•using a quadrat to calculate the mean and the number of individuals in several quadrats of a known area to find the density (number/metre^2) •estimating % cover of a plant in which individuals are hard to recognise •estimating % frequency |
