7.4 POPULATIONS IN ECOSYSTEMS Flashcards

1
Q

define

community

A

all the different species that live in one area and interact with each other

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2
Q

define

ecosystem

A

all living organisms found in one area, combined with non-living aspects of their environment

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3
Q

describe

biotic and abiotic factors

A

biotic = living features of an ecosystem e.g. predators, disease

abiotic = non-living features of an ecosystem e.g. light, temperature

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4
Q

define

habitat

A

the place where an organism lives within an ecosystem

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5
Q

define

niche

A

the role of a species within its habitat, consisting of both its biotic interactions e.g. what it eats, and abiotic interactions e.g. time of day it is active

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6
Q

define

carrying capacity

A

the maximum size of population an ecosystem can support

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7
Q

name

4 abiotic factors affecting population growth

A
  1. temperature
  2. light
  3. pH
  4. water/humidity
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8
Q

contrast

intra- and inter- specific competition

A

intra = competition between organisms of the same species

inter = competition between organisms of different species

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9
Q

state

resources organisms compete for

A

food, water, shelter, minerals, light, mates (intra)

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10
Q

describe

pattern of typical predator-prey relationship

in terms of population change

A
  • prey is eaten by predator, resulting in predator population increasing and prey population decreasing
  • fewer prey means increased competition for food, so predator population decreases
  • fewer predators means more prey survives, and the cycle begins again
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11
Q

explain

use of quadrats for estimating population size

A
  • placed on grid coordintes or at intervals along a transect
  • results reported as either percentage cover or frequency
  • for slow-moving or non-motile organisms
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12
Q

explain

use of mark-release-recapture for estimating population size

A
  • sample of species captured, counted, marked and released back into the same area they were caught
  • after a specified period of time, another sample is captured and counted for marked and unmarked organisms
  • for motile organsims
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13
Q

state

equation for mark-release-recapture

A

estimated population size = (t1 x t2)/r

t = total captured
r = recaptured

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14
Q

state

assumptions made by mark-release-recapture

A
  • few births
  • marked individuals distribute evenly
  • few immigrations
  • method of marking does not affect survival
  • mark doesn’t come off
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15
Q

explain

why ecosystems are descibed as dynamic

A
  • populations constantly rise and fall
  • any small change can have a large effect
  • biotic and abiotic factors may alter the conditions of the ecosystem
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16
Q

define

primary succession

A

where an area previously devoid of life is colonised by a community of organisms

17
Q

summarise

process of primary succession

A
  • pioneer species can survive harsh conditions & colonise the area
  • pioneer species change abiotic factors in the environment e.g. decomposition adds nutrients to ground
  • overtime, allows complex organisms to survive
18
Q

define and explain

climax community and how its reached

A

the final stage of succession where the ecosystem is balanced and stable
* reached when the soil is rich enough to support large trees or shrubs and the environment is no longer changing

19
Q

describe

alterations a species may have to their environment in succession

A
  • may impove the environment to make it more suitable for other species
    e.g. large root systems keeping dunes immobile
  • may worsen the environemnt to make it less suitable
20
Q

define

conservation

A

protection and management of species and habitats, in order to maintain biodiversity

21
Q

explain

how succession is managed to aid conservation

A
  • succession prevented to preserve an ecosystem at a certain point ( plagioclimax )