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Biology - BY4 > 4.5: Population size factors > Flashcards

4.5: Population size factors Flashcards

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1
Q

what is the definition of a population

A

a group of interbreeding individuals in a particular habitat at a particular time

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2
Q

what are the problems in defining a population

A

migration, species interbreeding makes it difficult to define species,

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3
Q

what is an example of species interbreeding

A

zorses. horses breeding with zebras, mules horses with donkeys, tigons tigers with lions, ligers lions with tigers

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4
Q

why are zorses and mules mostly sterile

A

mammals need an even number of chromosomes to divide into pairs for reproduction

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5
Q

what four factors affect population size

A

immigration , birth increase population emigration, death decrease population size

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6
Q

define birth rate

A

the reproductive capacity of a population

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7
Q

define immigration

A

the movement of individuals INTO a population

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8
Q

define emigration

A

the NON REVERSIBLE movement of individuals out of a population

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9
Q

define migration

A

the reversible periodic seasonal movement of individuals in and out of a population

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10
Q

what is another word for birth rate

A

natality

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11
Q

what is another word for death rate

A

mortality

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12
Q

define population growth

A

the sum of natality and immigration minus the sum of mortality and emigration

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13
Q

what are the advantages of living in a group

A

protection from predators
increased chance of finding mate
help raising offspring - extended family
cooperation

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14
Q

what are the four distinct phases of population growth

A

lag phase
log phase
stationary phase
death/decline phase

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15
Q

what are the factors that shape and define the lag phase

A
  • slow growth rate minutes to several days (in bacterial culture) due to very few individuals with few individuals of reproductive age in a sexually reproductive group
  • need for adaptation to environment or for preparation for growth e.g. increasing metabolic activity i.e enzyme synthesis
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16
Q

what are the factors that shape and define the log phase

A
  • rapid exponential growth achieved ( as long as no or few limiting factors) as numbers of reproductive individuals increase.
  • birth rate and population growth at maximum
  • does not last indefinitely.
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17
Q

what are the factors that shape and define the stationary phase

A
  • equilibrium reached as birth rate equals death rate
  • carrying capacity of environment reached (i.e. the maximum population size that the environment can sustain) as population limited by availability of space, of nutrition and accumulation of toxic waste products
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18
Q

what are the factors that shape and define the death/decline phase

A
  • death rate exceeds birth rate
  • carrying capacity exceeded
  • shortage of nutrients and/or accumulation of waste to harmful levels
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19
Q

define carrying capacity

A

the maximum population that a particular environment can sustain indefinitely

20
Q

why do most animal populations never reach the death decline phase

A

the populations growth rate slows down and reaches and oscillates around the carrying capacity

21
Q

what causes this oscillation around the carrying capacity

A

environmental resistance

22
Q

define environmental resistance

A

all the factors that limit and slow down population growth. ** can be calculated as the difference between biotic potential ( the species maximum growth potential) and its real growth. **

23
Q

why does population growth not remain constant

A

because of environmental resistance

24
Q

what are the disadvantages of living in a group

A

competition

25
Q

what are the two different types of competition

A

intraspecific - competition bettween individuals of same species
interspecific - competition between individuals with a diffeent species

26
Q

what are the factors that limit population growth

A 
available food
predation
disease/parasitism
overcrowding
competition ( for mates, space, food)
 accumulation of waste products
weather
27
Q

what are the factors that improve biotic potential

A

reproductive rate
ability to migrate (animals) disperse seeds (plants)
ability to invade new habitats

28
Q

in the case of predation describe the process of boom and bust that results in the fluctation of a population around the carrying capacity of a particular environment.

A

prey population increase results in an increase of food for predators.
predator numbers increase resulting in a decrease in prey population and so food
as a result of reduced food the predator population decreases as a result
cycle of boom and bust is set up. the equilibrium of which is called the carrying capacity of the population in that particular environment.

29
Q

is this an example of a negative feedback system

A

yes

30
Q

what two groups of factors can environmental resistance be divided

A

density dependent (slow down growth rate)
factors which increase their effect as population grows
density independent ( can cause population crash)
factors that affect any population regardless of size

31
Q

give examples of density dependent factors

A

disease, availability of food, build up of toxic waste, predation, parasitism,competition,space,biotic factors, overcrowding

32
Q

give examples of density independent factors

A

freezing,flood,fire,weather,temperature,abiotic factors

33
Q

describe natural selection

A

darwin noticed populations produced more offspring than neeed purely to maintain numbers. this increased population produces competiition. Those better adapted to the present environment survive and breed.

34
Q

how does natural selection lead to evolution

A

species have a natural variation in genes. the process of natural selection ensures that those genes that make the species members most suitable to their environment will pass on their genes to the next generation. Thus the species evolves ensuring the improved survival of that species in that environment.

35
Q

what did dawin notice happened when birds compete for the same food source?

A

those birds tend not to live in the same area
once established in a niche it is very difficult for another species to move in or steal it.
unless they are better adapted or
pick another place to live or pick another food source.
in the long term two species cannot occupy the same niche in a specific habitat

36
Q

give example that in the long term two species cannot occupy the same niche

A

p caudatum feeds on organisms suspended in water
p. aurelia as above
p. bursaria feeds on organisms at bottom of ponds
when these species are grown together p claudatum becomes extinct.

37
Q

define pest

A

any unwanted organism that interferes either directly or indirectly with human activity

usually associated with food production, disease transmission to plants or animals

38
Q

how do pests attack crop plants and animals reducing yield

A

feed on them
compete with them
cause disease
can make crops more susceptiable to disease
can spoil food in storage or transportation

39
Q

what is the economic damage threshold

A

the maximum pest population that can be tolerated at a particular time and place without a resultant economic crop loss

40
Q

at what point do you spray a crop

A

when it reaches the economic threhold. where the cost of spraying is less than the cost of crops lost.

41
Q

what are the two main ways of control

A

chemical e.g. insecticide, fungiside, herbicide

biological

42
Q

what are advantages of chemical control

A 
fast acting
localised
cost effective they ave a low economic threshold value
can be applied on small or large scales
little skill needed
43
Q

what are the disadvantagesof chemical control

A
  • non selective can kill pollinators and pest eating species( which means any pest which survives or migrates has no competition)
  • can kill animals and humans
  • chemicals may not be biodegradable and are persistant in environment can bio accumulate eg. ddt causing death and infertility in higher food chain species as toxicity builds up in them from eating lots of other polluted species. biomagnification
  • pollute water supply
  • pests can develop resistance to chemicals
44
Q

how do bacteria become resistant to antibiotics

A

antibiotics create a process of natural selection. If any bacteria survive by adaption these better adapted bacteria will breed and produce an antibiotic resistant strain. without competition this becomes the predominant strain and that antibiotic becomes ineffective,

45
Q

name two other examples of resistance

A

warfarin resistant rats

pesticide resistant insects

46
Q

what are the properties of an ideal pesticide

A

specificc
non persistent
should not accumulate
should not be passed along food chain

Biology - BY4 (6 decks)

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