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A level OCR Biology > 6.3.2 Populations and sustainability > Flashcards

6.3.2 Populations and sustainability Flashcards

(96 cards)

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1
Q

what is a population?

A

population consists of all the individuals in a defined area that belong to the same species

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2
Q

what sort of models do environmental scientists use to frame predictions about the population of humans and why?

A

environmental scientists use mathematical models based on non-human organisms to frame predictions about the future of our population, this is because human populations match mostly all of the aspects of non-human populations

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3
Q

what are demographics we can study in a population?

A

-age
-sex ratio
-immigration
-emigration
-birth rate
-death rate

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4
Q

what will increase a population size?

A

-natality (birth rate)
-immigration

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5
Q

what will decrease a population size?

A

-mortality (death rate)
-emigration

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6
Q

how can the patterns of population growth over time be revelaed?

A

by plotting the number of individuals (N) as a function of time (t)

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7
Q

what would an increasing population graph look like?

A

see paper flashcard

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8
Q

what would a decreasing population graph look like?

A

see paper flashcard

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9
Q

what does a nearly constant population graph look like?

A

see paper flashcard

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10
Q

what does a cyclic population graph look like?

A

see paper flashcard

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11
Q

what does a chaotic population graph look like?

A

see paper flashcard

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12
Q

what pattern do natural populations follow shortly after establishment?

A

a linear growth model

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13
Q

what happens to natural populations soon after they have been established?

A

N often increases faster than a linear model once critical density is reached causing an exponential model

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14
Q

how do scientists have to change the linear model after the critical density of a population is reached?

A

we have to abandon the linear model and adapt what is known as the exponential model, here a cumulative effect of increased numbers leads to even faster growth than linear growth

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15
Q

what is the steepness of the exponential curve determined by?

A

the difference between the birth rate and death rate which is designated ‘r’

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16
Q

what is exponential growth?

A

growth at a constant rate of increase per unit of time when conditions are ideal (the growth of a population without limits)

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17
Q

what is an example of exponential growth?

A

bacteria grown in Petri dishes

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18
Q

what can sometimes happen with exponential growth of populations?

A

this can flatten into a curve called an S shaped curve and it reaches a limit of the population size that it can only briefly exceed before being reduced due to one or more environmental factors containing the exponential growth and preventing the population size from increasing forever

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19
Q

what are the different phases of a population growth graph that applies for mostly every organism?

A

-lag phase
-log phase
-stationary phase

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20
Q

describe the lag phase of a population graph

A

phase 1, a period of slow growth. The small numbers of individuals that are initially present reproduce increasing the total population (as birth rate is higher than the death rate, the population increases in size)

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21
Q

what is a population growth curve?

A

this is the growth of a new population that is plotted on a graph, regardless of the organism as most natural populations share the same characteristics

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22
Q

what is a limiting factor?

A

an environmental resource or constraint that limits population growth

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23
Q

why can’t population growth just continue on forever?

A

due to limiting factors in the environment

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24
Q

describe the log phase of a population graph

A

phase 2, a period of rapid growth. As the number of breeding individuals increases, the total population multiplies exponentially. No constraints act to limit the population explosion.

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25
describe the stationary phase of a population graph
phase 3, a stable state. Further population growth is prevented by external constraints. Birth rates and death rates are approximately equal, slight increases and decreases can be accounted for by fluctuations in limiting factors
26
what biotic factors limit exponential growth?
-predators -disease -competition
27
what abiotic factors limit exponential growth?
-temperature -light -pH -availability of water or oxygen -humidity
28
what is carrying capacity?
the maximum population size that an environment can support
29
define predator
an animal that hunts and kills other animals for food
30
define prey
an animal that is hunted for food
31
where is a predator prey relationship most easy to see?
it is easier to see a predator prey relationship in the lab than in the wild
32
why is it hard to see a predator prey relationship in the wild?
because the relationship will only occur if predation is the only limiting factor and there is only 1 predator
33
describe a predator prey relationship
the size of the predator population affects the size of the prey population and vice versa
34
what are some features that distinguish predators from prey?
-predators have sharp teeth -predators have eyes on the front of their face whereas prey have them on the side of their face -predators have claws
35
why do predators usually have eyes on the front of their face?
so they can judge distance better
36
describe and explain a population graph of predator and prey
As the number of prey increase, the number of predators also begin to increase which is due to the fact that the predators have more food available because of the increase of prey so their population numbers increase. Then due to the higher number of predators- more prey is eaten so prey population falls and also the predators are now in greater competition with each other for the remaining prey so predator population falls.
37
when drawing a predator prey population graph what must you remember?
the predator peaks must be delayed after the prey peaks, they also must have higher peaks and lower troughs than the prey
38
suggest some factors that can cause a population explosion of a species of prey
-less disease -less competition from other species -fewer predators -plenty of food
39
define competition
an example of a biotic limiting factor- it is a result of the interactions between living organisms
40
what is intraspecific competition?
this happens between individuals of the same species
41
what is intraspecific competition dependent on?
it is density dependent as more individuals means less resources
42
what slows population growth in terms of intraspecific competition?
when there's an increased population which in turn limits resources
43
there are slight fluctuations in population size, explain the relationship between population size and intraspecific competiton
as population size increases so does the competition for resources which causes the population size to decrease which then reduces the competition which causes fluctuation
44
what is interspecific competition?
this happens between individuals of different species
45
why does interspecific competition usually occur?
because it is usually between species occupying similar niches
46
what does interspecific competition result in?
a reduction of the resource available to both populations
47
why are the populations of the two different species competing in interspecific competition smaller than if just one species was present?
because if both species compete for the same food source, there will usually be less available organisms of each species, as a result of less food, organisms will have less energy for growth and reproduction, resulting in smaller populations
48
what is the competitive exclusion principle?
where two different species are competing for limited resources, the one that uses the resources more effectively will ultimately eliminate the other
49
give an example of interspecific relationships
red and grey squirrels in the UK
50
how did the grey squirrels so successfully out compete the red?
the grey squirrel can eat a wider range of food than the red squirrel and it is larger so it can store more fat, this increases its chances of survival and therefore its ability to reproduce thus increasing its population
51
what happens when breeding territories do not have enough food?
there's not enough resources to survive and reproduce
52
how does breeding territories not having enough food affect population size?
population size decreases
53
give an example of an intra specific relationship
Robins compete for breeding territory
54
what would the same species compete for?
-food -mates/breeding territory -habitat
55
what would different species compete for?
-food -habitat
56
when would an increase in food supply lead to bigger individuals?
when there's less competition
57
what does conservation require?
active management
58
what forms does active management take when conserving a species?
-add more individuals to enlarge populations -restrict movement with fences -control predators and poachers -vaccinations -preserve habitats -reclamation of land
59
what can be done during conservation to reclaim land?
-clean up pollution -remove unwanted species -know which were original species and recolonise them
60
what are the different economic reasons for conservation?
-flora for potential medicines -conservation for fish stocks
61
what are the different social reasons for conservation?
-ecotourism -people enjoying the natural environment
62
what are the ethical reasons for conservation?
-all organisms have a right to life
63
define conservation
the maintenance of biodiversity
64
define preservation
protection of an area by restricting or banning human use- so that the ecosystem is kept exactly as it is
65
define sustainability
ensuring resources are available for future generations
66
define sustainable development
management of ecosystems so that the natural resources in them can be used without running out
67
define sustainable resource
a renewable resource which is being economically exploited in such a way that it will not diminish or run out
68
define reclamation
the process of restoring ecosystems that have been damaged or destroyed
69
what are the key reasons why the populations of Pangolins are declining?
-increasing demand for their meat, which is seen as a delicacy -scales and other body parts which are used in some traditional medicines -poaching and illegal trade -pangolin fetuses are thought to be an aphrodisiac
70
state some conservation measures that can be used to support the Pangolins
-supporting anti-poaching patrols and law enforcement at key sites -initiating work to reduce demand for Pangolin products in China -develop a team of early-career Central African and Asian conservation practitioners -study Pangolins and the threats they face
71
state a preservation measure that can be taken to support the Pangolin
protect the land they live on- preventing human access
72
what are some advantages of placing an organism on the iUCN endangered species list?
-population rises so prevented from extinction -biodiversity is maintained -provides more awareness of conservation issues
73
what are some disadvantages of placing an organism on the IUCN?
-resources which could be used to support other organisms are diverted -ethical issue to decide which species should be conserved and what should not -human use of space is prevented -could mean a natural resource is no available for use by humans
74
what are the aims of sustainability?
-preserve the environment -ensure resources are available for future generations -allow humans in all societies to live comfortably -enable less economically developed countries to develop, through exploiting their natural resources -create a more even balance in the consumption of these resources between a more economically developed country and a less economically developed country
75
what percentage of the world's fisheries are over fished?
85%
76
what is a main disadvantage of trawler fishing?
it creates large amounts of by-catch (other organisms that are killed as well as the fish) and destroys the ecosystem
77
when is the main disadvantage of Long line fishing?
lots of by catch
78
when is a wild fish sustainable?
if it's caught in a way that doesn't threaten the long term survival of it's species or ecosystem it is part of
79
what are more sustainable methods of catching fish?
-hook and line fishing -harpooning -some traps
80
what are the problems with fish farms?
-they pollute oceans with their waste -release fish into wild which as they are genetically different can disrupt the populations
81
what is the common fisheries policy?
this provides fishing quotes which gives limits on the numbers of certain species of fish that are allowed to be caught in a particular area
82
how can mesh size allow sustainable fishing to occur?
mesh sizes can be made sufficiently large enough that immature fish can escape- only mature fish are caught, thus allowing breeding to continue
83
why is commercial and recreational fishing only allowed at certain times of the year?
this protects the breeding season of some fish species and allows the fish levels to increase back to a sustainable level
84
why are fish farms useful?
in some regions, the fish are placed in rice fields at planting time where they grow to edible size when the rice is ready to harvest
85
what are the different sustainable uses of resources?
-sustainable timber production -sustainable fishing
86
what are the different types of sustainable timber production?
-small scale timber production -large scale timber production
87
why is coppicing used?
this is a technique where a tree trunk is cut close to the ground which allows new shoots to form from the cut surface and mature, eventually these shoots are cut and in their place more are produced
88
what are the new sheets from coppicing often used for?
fencing
89
when is coppicing used?
during small scale timber production
90
what is rotational coppicing?
the woodland is divided into sections and trees are only cut in a particular section until all have been coppiced- coppicing then begins in another area allowing time for the newly coppiced trees to grow
91
what is the main advantage of rotational coppicing?
maintains biodiversity as trees never grow enough to block out the light, hence, succession cannot occur and so more species can survive
92
what is pollarding?
this is similar to coppicing but the trunk is cut higher up
93
what is the main advantage of pollarding?
deer and other animals can eat new shoots as they appear
94
what is large scale timber production based on?
based on the technique of felling large areas of forest, the felled areas are destroyed and will not regrow
95
what are key practices of sustainable felling?
-selective cutting -replace trees through replanting -plant trees optimal distance apart -manage pests and pathogens -ensure areas of the forest remain for indigenous people
96
what are the main disadvantages of this method?
-habitats are destroyed -soil minerals are reduced -the bare soil that is left is susceptible for erosion

A level OCR Biology (13 decks)

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