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Medical Science UNEDITED 2 > 3.7.4 Populations in ecosystems > Flashcards

3.7.4 Populations in ecosystems Flashcards

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USMLE® Step 1 flashcards Biology 101 flashcards
1
Q

define community

A

all living organisms of all species found in a given area/habitat/ecosystem at a given time

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2
Q

define ecosysytem

A

self contained area including all the living (all the communities within it) and non living factors interacting with one another

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3
Q

define niche

A

describes how an organism fits into the environment/its role in the ecosystem - no organism can occupy the same niche

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4
Q

define succession

A

used to describe changes that occur over time, in the species that occupy a particular area

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5
Q

define abiotic

A

non living factor in the environment of an organism e.g temperature, oxygen concentration, pH, light

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6
Q

define biotic

A

the living factors in the environment of an organism e.g. disease, predation, competetion

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7
Q

define population

A

all of the organisms of one particular species in a given habitat/area at the same time

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8
Q

What conditions are necessary in order for the mark release recapture investigations to be valid? what assumptions are made?

A
  1. markings dont make organism visible to predators
  2. markings dont harm the organism
  3. No migration/immigration
  4. sample large
  5. no reproduction
  6. no births or deaths
  7. markings are nor easily rubbed off/worn off
  8. marked individuals in 1st sample distribute themselves evenly back into the population
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9
Q

Name two types of competition

A

interspecific and intraspecific

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10
Q

Define intraspecific competition

A

competition between organisms of the SAME species

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11
Q

Define interspecific competition

A

competition between organisms of DIFFERENT species

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12
Q

What is a pioneer species?

A

the first organism to colonise in the first stage of succession - it can with stand hostile environments

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13
Q

define a climax community

A

A stable community/no further succession.

All the organisms that make up the final stage of succession - animals and plants

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14
Q

define a habitat

A

place where a habitat where an organism lives

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15
Q

define carrying capacity

A

The population size of a species that an be supported by the ecosystem

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16
Q

within an ecosystem which 2 major processes occur

A
  1. flow of energy through the system

2. recycling of nutrients within the system

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17
Q

define population size

A

the number of individuals in the population

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18
Q

what do we call factors that limit the size of the population

A

limiting factors - they can be abiotic or biotic

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19
Q

Give examples of abiotic factors that limit the size of a population

A

light, temperature, pH, water, humidity

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20
Q

give examples of biotic factors that limit population size

A

availability of food, predation, disease

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21
Q

The growth and size of the human population depends on

A

birth rate v death rate - its the balance between these two that determines if if increases, decreases or remains the same (also includes immigration and migration)

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22
Q

define immigration

A

when people move into a population from outside

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23
Q

define emmigration

A

when people move out of a population and leave

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24
Q

In a stable population what can be said about birth and death rates?

A

they are equal

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25
Q

In an increasing population what can be said about birth and death rates?

A

birth rates are higher than death rates

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26
Q

define predation

A

where one organism is consumed by another

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27
Q

Define prey

A

An organism that is consumed/hunted by another organism

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28
Q

Define a predator

A

An organism that hunts and feed on other organisms

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29
Q

Why is it impossible to count every organism when investigating populations?

A

too many to count, too time consuming, would probably damage the habitat

30
Q

How do we ensure the samples we take are representative when investigating populations

A

Take large sample, sample at random

31
Q

Name two types of quadrats

A

frame and a point

32
Q

How does a point quadrat work?

A

A long pin is dropped along a horizontal bar at set intervals and the organism record that touches the pin

33
Q

How does a quadrat work?

A

placed at various locations at random and the abundance of each species within the quadrat is then recorded

34
Q

Describe how you sample at random

A
  1. lay out 2 tape measures at right angles along the area to study
  2. obtain a set of coordinates by a random number generator
  3. place the quadrat at the intersection of the coordinates and record the species present
35
Q

define abundance

A

the number of individuals of each species in a given area

36
Q

Abundance can be measured in two ways

A
  1. frequency

2. % cover

37
Q

To ensure your results are reliable and representative you should

A

make sure your sample size is large

38
Q

What does the mark release recapture technique allow you to do?

A

estimate the population size of organisms that move

39
Q

state the formula for mark release recapture

A

est pop size = (total no of organisms in 1st sample x total number in 2nd sample)/ number of marked organisms recaptured.

40
Q

Name the first species to colonise in the first stage of succession

A

pioneer species - they an withstand the hostile growing environment

41
Q

What features might pioneer species have that make them able to colonise

A
  1. reproduce asexually
  2. produce a vast amount of wind dispersed seeds/spores that an reach isolated areas
  3. rapidly germinating seeds
  4. ability to photosynthesise
  5. ability to fix nitrogen
  6. tolerance to extreme conditions
42
Q

Name pioneer species example capable of surviving inhospitable conditions

A

lichens

43
Q

What species follows after lichens - why?

A

Mosses - this is because the environment becomes more hospitable, abiotic factors are changing

44
Q

What species follows after mosses in succession?

A

ferns

45
Q

How does succession impact on animals?

A

they have undergone successional changes too - largely determined by the different types of plants available for food and habitats!

46
Q

The common features of succession include

A
  1. abiotic environment becomes less hostile
  2. greater number of and variety of habitats and niches
  3. increased biodiversity
  4. Increased variety of food sources
  5. more complex food webs
  6. increased biomass
47
Q

Name the two types of succession

A

primary and secondary

48
Q

what is the difference between primary and secondary succession

A

primary - bare land - no soil - takes longer to reach a climax community
secondary succession - felled areas - soil present - climax community reached sooner/more quickly

49
Q

what is conservation?

A

The management of the earths natural resources by humans for the future

50
Q

What does conservation of habitats involve?

A

active human involvement

51
Q

What are the main reasons for conservation?

A
  1. maintain our planet
  2. Other species have occupied the planet longer than we have - respect
  3. living organisms contain a huge pool of genes that can make useful products/substances - could prove valuable in the future
  4. Habitats and organisms enrich our lives and many people find inspiration from them
52
Q

what do you call the maximum stable population size of a species that an ecosystem can support?

A

carrying capacity

53
Q

A predator is…

A

an organisms which kills and eats other organisms

54
Q

predator and prey populations are said to be…

A

linked - when one increases the other increase (shortly after)..

55
Q

what is a quadrat?

A

a square frame enclosing a given area

56
Q

what equipment can you use to investigate non-motile organisms (e.g. plants and limpets)

A

quadrats and transects

57
Q

What technique do you use to investigate motile organisms?

A

mark release recapture

58
Q

What is species frequency?

A

How often a species is found

59
Q

What would you set up if you wanted to investigate changes in plant distribution and environmental factors?

A

transect - place quadrat at regular intervals along the length and determine % cover (of chosen plant). Measure the environmental factor at that point too

60
Q

Succession is…

A

how an ecosystem changes with time

61
Q

During succession what changes?

A

Biotic conditions change as the abiotic conditions change

62
Q

Primary succession …

A

happens on bare rock

63
Q

secondary succession occurs…

A

on land that has been cleared/felled areas

64
Q

What are the abiotic condition like at the start of succession?

A

harsh

65
Q

What does the pioneer species do to the abiotic conditions?

A

changes them to make it less hostile so other species can begin to colonise

66
Q

Does the pioneer species survive?

A

No it will die and be decomposed and add to the soil.

67
Q

What happens to biodiversity as succession continues?

A

increases

68
Q

The final stage if succession is called?

A

climax community

69
Q

What sorts of activities prevent succession?

A

mowing lawn, animals grazing, managed fires

70
Q

give 2 features of a climax community

A
  1. Same species present (over long time) / stable community (over long time);
  2. Abiotic factors (more or less) constant (over time);
  3. Populations stable (around carrying capacity);
71
Q

How do you use the mark release recapture to determine the population of species A?

A
  1. Capture/collect/sample, mark and release;
  2. Leave time before second sampling/collection;
  3. (Population =) number in first sample × number in second sample divided by number of marked in second sample/number recaptured

Medical Science UNEDITED 2 (25 decks)

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