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biology > C4.1 - populations and communities > Flashcards

C4.1 - populations and communities Flashcards

1
Q

positive and negative association

A

positive - two species live together
negative - species tend not to be found together

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2
Q

ecosystem

A

interactions of a community with the abiotic environment

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3
Q

endemic species

A

species that are native to a geographic region

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4
Q

interspecific

A

interaction between organisms of two different species

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5
Q

intraspecific

A

interactions between organisms within the same species

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6
Q

natality

A

reproduction and birth

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7
Q

negative feedback control

A

when one even causes a decrease in the other event to return it to the original level

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8
Q

quadrat

A

square frame used to sample an ecosystem by counting the number of organisms

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9
Q

reliability

A

data is stronger as measurements are repeated

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10
Q

sessile

A

cannot move

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11
Q

species

A

group of organisms that can interbreed to produce fertile offspring

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12
Q

symbiotic

A

close and long-term interaction between two species

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13
Q

secondary metabolites

A

molecules that an organism produces but is not needed for basic life functions

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14
Q

population

A

a group of individual organisms in the same species living and interacting in the same area

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15
Q

what is the relationship between sampling size and accuracy?

A

the larger the sample size, the more accurate the population estimate

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16
Q

how can we estimate population sizes?

A

we can use random sampling to avoid bias in selection and identifying numbers in small areas and extrapolating to estimate real populations

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17
Q

how can a quadrat be used to estimate populations of sessile organisms?

A
  1. use a 0.5 x 0.5, quadrat and create x and y co-ordinates for the area you are testing
  2. generate random co-ordinates and place the quadrat in that area, counting the number of plants in several different areas
  3. calculate the population by multiplying the mean number of species per m2 by the area of the field
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18
Q

what information does standard deviation give about the spread of organisms?

A

standard deviation tells us about the variability which is how evenly the population is spread
- the larger the standard deviation, the less evenly the population is spread

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19
Q

how can we estimate population size of motile organisms?

A

using the capture-mark-release-recapture method

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20
Q

how do you calculate the Malcolm Index?

A

M x (N/R)
M - number of individuals marked initially
N - number of individuals recaptured
R - number of marked individuals recaptured

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21
Q

what are assumptions of the capture-mark-release-recapture method?

A
  • assumes large enough sample size
  • assumes no migration
  • assumes no birth or deaths
  • assumes marking doesn’t affect organisms survival
  • assumes marked organisms don’t lose their marks
  • assumes no mis-identification of species
  • assumes marked and unmarked species have an equal chance of being captured
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22
Q

carrying capacity (K)

A

maximum population size that an ecosystem can support due to limited resources which promote competition

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23
Q

what factors can affect the carrying capacity?

A

plants - water levels, light availability, nutrients, soil salinity
animals - disease, habitats, food, oxygen, predation

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24
Q

what are density-independent factors?

A

same no matter the population
- weather, climate, natural distasters

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25
Q

what are density-dependent factors?

A

larger impact as the population increases
- competition, predation, diseases

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26
Q

what factors cause a negative feedback cycle?

A

density dependent factors as when population size increases, there is a greater or lesser impact of a factor, causing more death or birth

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27
Q

what are the stages of the population growth curve?

A

Sigmoidal growth curve (s-shaped)
1. Exponential growth phase
2. Transitional phase
3. Plateau phase

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28
Q

what are characteristics of the exponential growth phase?

A
  • ideal environment with unlimited resources
  • absence of limiting factors
  • little disease and few predators
  • high immigration and natality
  • population can double on a regular basis
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29
Q

what are characteristics of the transitional phase?

A
  • resources become limited and growth is slowed
  • immigration and natality is still higher then emigration and mortality
  • increased competition for resources
  • presence of predators and disease
30
Q

what are the characteristics of the plateau phase?

A
  • growth continues to slow as population size plateaus at carrying capacity
  • natality = mortality
  • population size is not constant but oscillates around the carrying capacity
31
Q

what are strengths of the wildebeest species in illustrating the population growth curve?

A
  • exponential growth (1958 - 1972)
  • plateau phase (1978 - 2003)
32
Q

what are weaknesses of the wildebeest species in illustrating the population growth curve?

A
  • no clear transitional phase
  • decrease in population during plateau phase ( due to density-independent factor)
33
Q

how can we use duckweed to model the sigmoidal curve?

A

place duckweed in a cup of water in a warm environment with lots of light and count the number of individual plants over time

34
Q

how can we use yeast to model the sigmoidal curve?

A

add yeast and sterile nutrient broth to a sample, cover and shake to remove bubbles, then add methyl blue indicator and view under the microscope over a period of time

35
Q

what are pros and cons of using duckweed and yeast to model sigmoidal curves?

A

pros - easy to store and small, low cost, quick
cons - as organisms are grown in closed systems, accumulation of metabolic waste can cause death

36
Q

why does intraspecific competition occur?

A

limited resources that isn’t enough to support all individuals in a population and survival of the fittest occurs

37
Q

what is the difference between intraspecific competition and co-operation?

A

intraspecific competition - members of the same species compete for the same resources
intraspecific co-operation - individuals aid other members of the same species to increase likelihood of their survival as a population as a whole

38
Q

community

A

all of the interacting organisms in an ecosystem

39
Q

herbivory

A

interaction where a primary consumer eats plant material, destroying a producer

40
Q

predation

A

predator eats prey

41
Q

interspecific competition

A

interaction between two organisms where the fitness of one is lowered by the presence of the other as both compete for the same resources

42
Q

pathogenicity

A

ability of micro-organisms to cause disease in other species

43
Q

parasitism

A

symbiotic relationship where one species benefits to the detriment of another

44
Q

mutualism

A

symbiotic relationship that benefits both species

45
Q

what are 3 examples of mutualism in species?

A
  • Rhizobium in root nodules of Fabaceae
  • Mycorrhizae fungus in Orchidaceae
  • Zooxanthellae in hard corals
46
Q

how does the Rhizobium in root nodules of Fabaceae benefit?

A

Rhizobium receive carbohydrates and a protected environment.
Legumes gain nitrate minerals to produce biological molecules

47
Q

how does the Mycorrhizae fungus in Orchidaceae benefit?

A

Fungus gains nutrients from orchids via decomposition.
Orchids gain nitrogen and carbon via the fungal hyphae.

48
Q

how does the Zooxanthellae in hard corals benefit?

A

photosynthetic algae that live in coral tissue
Zooxanthellae obtain shelter, light, ammonia, carbon dioxide.
Coral gains oxygen and sugars, lipids and amino acids from photosynthesis.

49
Q

what type of control is a predator prey relationship?

A

density dependent control of a population
- if a predator only consumes one prey and the prey has no other predator species, the relationship is cyclical

50
Q

what is a limitation of the predator prey cycle?

A

it is a simplification as in reality, there are more complex systems involved in the cycle

51
Q

invasive species

A

species that are introduced accidentally or deliberately and have a negative effect

52
Q

what happens when an invasive species is introduced?

A

decreases the population size of the endemic species due to competition and can introduce new diseases
- if the predators aren’t endemic, population of invasive species increases, disrupting food chains and increasing likelihood of extinction

53
Q

what are 3 methods to test for interspecific competition?

A
  1. Laboratory experiments
  2. Field observations by random sampling
  3. Field manipulation by removal of one species
54
Q

how can laboratory tests be used for interspecific competition?

A

taking organisms out of their natural environment and growing them in a lab to control more variable (validity)
- however this isn’t ethical, so is only done on common plant species

55
Q

how can field observations be used for interspecific competition?

A

observing two species in a given area to see where they are present at certain times to see if there is any compeition

56
Q

how can field manipulation be used for interspecific competition?

A

researchers measure population of second species before removing the first and measuring the population of the second species afterwards

57
Q

what is the difference between observations and experiments?

A

observations - measure value of a factor that naturally changes
experiments - manipulation of a factor to determine the effect

58
Q

what is a chi-squared analysis?

A

explores the similarities or differences in the distribution of two species across several sampling sites

59
Q

competitive exclusion

A

one species may use resources more effectively, out-competing the other which cannot survive

60
Q

resource patrioning

A

both species change how they use the habitat to avoid direct competition

61
Q

what happens if the calculated chi-squared value is larger than the value in the table of critical values?

A
  • difference between observed and expected value is statistically significant
  • null hypothesis rejected
  • alternative hypothesis accepted
  • data supports association between two species
62
Q

limiting factors

A

define the carrying capacity of an ecosystem

63
Q

what is top down control?

A

factors involving higher trophic levels limiting population growth resulting in an oscillating trophic cascade

64
Q

what is bottom up control?

A

limits the availability of resources to the lower trophic levels and causes reduced population growth for higher trophic levels

65
Q

keystone species

A

species that have disproportionate impact on community given their abundance
- exert top down control by reducing previous trophic levels’ population to prevent them from dominating essential resources

66
Q

allelopathy

A

production of secondary metabolites that influence the growth and success of other organisms

67
Q

what is an example of allelopathy with garlic mustard?

A

produces sinigrin which inhibits root growth and seed germination of surrounding plants

68
Q

antibiotics

A

secreted by micro-organisms to kill or inhibit growth of bacterial species

69
Q

what is an example of an antibiotic?

A

penicillium rubens secretes penicillin which stops the growth of bacterial species in order to gain a competitive advantage

70
Q

what is the role of both allelopathy and antibiotics?

A

release chemical substances into the environment to deter potential competitors

biology (22 decks)

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