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Biology 30 > Ecology/Statistics > Flashcards

Ecology/Statistics Flashcards

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1
Q

When does evolution occur?

A

When there are genetic changes in a population over time

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2
Q

Define population:

A

Group of organisms of the same species living together in a defined area and time

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3
Q

Define genes:

A

Code for particular trait carried on chromosomes

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4
Q

Define allele:

A

Form of a gene

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5
Q

Define gene pool:

A

Sum of all the alleles for all the genes in a population (sum of all genetic variation that can be passed on)
- The more variety in a gene pool, the better the population can survive

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6
Q

Describe genotype frequency:

A
  • Proportion of a population with a particular genotype
  • Usually expressed as a decimal
  • Number of individuals with that genotype divided by the total number of individuals in that population
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7
Q

Describe phenotype frequency:

A
  • Proportion of a population with a particular phenotype
  • Number of individuals in that population with that phenotype divided by the total number of individuals in that population
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8
Q

Describe allele frequency:

A
  • Rate of occurrence of a particular allele in a population
  • Expressed as a decimal
  • Times the population number by two (one on each chromosome pair) then divide it by the total number
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9
Q

Describe recessive alleles:

A
  • Some recessive alleles are more common than dominant
  • Allele frequencies actually remain the same as long as five conditions are met (Hardy-Weinberg principle)
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10
Q

Describe the Hardy-Weinberg principle:

A
  • Allele frequencies will remain the same if the following conditions are met:
    1. The population is large enough that chance events will not alter allele frequencies
    2. Mates are chosen on a random basis
    3. There are no mutations in the genes that affect phenotype
    4. There is no migration
    5. There is no natural selection against any of the phenotypes
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11
Q

Describe Hardy-Weinberg calculations:

A
  • The letter “P” is used to represent frequency of dominant alleles
  • “q” is used to represent frequency of recessive alleles
  • Combination of frequencies of alleles should equal 1.00 (100%)
  • q+p = 1.00
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12
Q

How to calculate the number of individuals with a specific genotype:

A
  • If you know the population size, N, you can use the following formula to calculate the number of individuals with a specific genotype
  • p2(N) + 2pq(N) + q2(N) = N
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13
Q

What is the equation for genotype frequencies:

A

p2 + 2pq + q2 = 1.00

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14
Q

P =

A

Frequency of the dominant allele in the population

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15
Q

q =

A

Frequency of the recessive allele in the population

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16
Q

p^2

A

Percentage of homozygous dominant individuals

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17
Q

q^2

A

Percentage of homozygous recessive individuals

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18
Q

2pq

A

Percentage of heterozygous individuals

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19
Q

Describe genetic equilibrium:

A
  • No change in allele frequencies
  • Population is not evolving or changing
  • Also called Hardy-Weinberg equilibrium
  • Evolution cannot occur at genetic equilibrium
  • Microevolution - gradual change in allele frequencies
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20
Q

Describe mutations:

A
  • Change in the DNA of an individual
  • Back mutation - reverse the effects of former mutations
  • If the number of back mutations is equal to the number of mutations there are no net mutation
  • Heritable mutations may diversify the gene pool
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21
Q

Describe gene flow:

A
  • Net movement of alleles from one population to another due to migration of individuals
  • Increases genetic diversity in one population
  • Reduces genetic diversity between populations
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22
Q

Describe non-random mating:

A
  • Random mating is probably uncommon due to preferred phenotypes
    • Example: animals might choose particular mates for certain traits
    • Inbreeding
      • Extreme example - some flowers self pollinate
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23
Q

Describe genetic drift:

A
  • If particular individuals do not breed, any unique alleles they have may be lost from the gene pool
  • Change in allele frequencies due to chance events is called genetic drift
  • Usually only occurs if populations size decreases relatively quickly
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24
Q

Describe the founder effect:

A
  • Founders - the individuals who form new populations
  • Because founders are only a small number of individuals, they do not usually represent the entire gene pool
  • Founders may not be typical of the whole population so frequency of rare alleles may increase
  • Founder effect - gene pool change that occurs when a few individuals start a new, isolated population
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25
Q

Describe the bottleneck effect:

A
  • Gene pool change that results from rapid decreasing in population size
  • Often seen in species driven to end of extinction
  • Reduces genetic diversity, even if population regenerates
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26
Q

Describe natural selection:

A
  • Only process that leads directly to evolutionary adaptation
  • Those animals with favourable traits survive
  • Heterozygote advantage - when a harmful or lethal allele is actually beneficial in its heterozygous form
    • eg. sickle cell anemia
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27
Q

Describe an ecological community:

A
  • Association of interacting populations that inhibit a defined area
  • Eg. animals in a forest
28
Q

Describe intraspecific competition:

A
  • Competition for limited resources among members of the same species
  • Density - dependent factor to limit population growth
  • Plays a role in natural selection
29
Q

How do species avoid parents out-competing offspring?

A
  • Disposal of young or seeds
    • Young end up far away from parents
  • Different life stages
    • Young and parents use different life stages
30
Q

Describe interspecific competition:

A
  • Competition between members of different species of the same community
  • Not two species can share the same ecological niche (habitat and role in community)
  • When niches are slightly different, interspecific competition is not as harsh
31
Q

Describe the effect of competition on organisms:

A
  • Competition drains energy from all individuals around
  • Even those that “win” use valuable energy that could have been put towards reproduction
32
Q

Describe a predator - prey (predator-consumer) relationships:

A
  • If there are more prey, the population if predators will increase
  • Prey populations then decrease as a result and the predator population follows
  • With the lack of predators, the prey population will increase
  • The cycle continues
  • Resources available to prey also plays a role in this cycle
33
Q

What are the prey (or producer) defence mechanisms:

A
  • Some examples include bitter-tasting chemicals, thorns, or camouflage
  • Cryptic coloration is a type of protective coloration that uses bright colors to warm predators
34
Q

Describe mimicry:

A
  • Some organisms mimic those that are more harmful to avoid being eaten
  • Batesian mimicry - a harmless organism mimics a harmful (or unpleasant) one
  • Mullerian mimicry - two unpleasant or harmful species resemble one another
35
Q

Describe symbiotic relationships:

A
  • Symbiosis - direct or close relationship between individuals of a species that live together
36
Q

Describe mutualism:

A
  • Both partners benefit or depend on the relationship
  • Example - ants and acacia trees –> tree provides nutrients and a home, ants provide protection and nutrients
37
Q

Describe commensalism:

A
  • One partner benefits and the other neither benefits or is harmed
  • Eg. barnacles on a whale –> barnacles get nutrients but the hale is not affected
38
Q

Describe parasitism:

A
  • One species benefits and the other is harmed
  • Eg. tapeworms and mistletoe –> both derive nutrients from their host and harm the host in the process
39
Q

Describe ecological succession:

A
  • Sequence of invasion and replacement of species in an ecosystem over time
  • Driven by biotic and abiotic factors
  • Given enough time, an ecosystem will return to (or develop into) its mature state (a mature ofrest for example)
  • Examples:
    • Rock or concrete –> grasses and scrubs –> intermediate forest –> mature forest
    • Pond –> accumulating slit –> field –> shrubs –> trees –> mature forest
40
Q

Describe the cycles of succession:

A

pioneer community –> climax community –> ecological disturbance –>

41
Q

Describe primary succession:

A
  • No soil present (eg. rock under retreating glacier)
  • Pioneer community - first species to colonize the area
    • Small opportunistic organisms with the ability to break down rock
    • Form from soil
    • Eg. lichen, moss
  • Stages on succession happen due to interspecific competition
  • Climax community - mature ecosystem
    • Eg. mature forest
42
Q

Describe ecological disturbances:

A
  • Events that change the structure of a community
  • Examples of large: forest fire, avalanche, clear-cut
  • Examples of small: tree falling, small slide
  • Some are necessary ad healthy for the ecosystem
    • Eg, berries that grow after a forest fire provide food, some trees seeds will only germinate in a forest fire
43
Q

Describe secondary succession:

A
  • Occurs after an ecological disturbance such as a forest fire
  • Very similar to primary succession
  • Size of disturbance will indicate what ype of organisms will be in the pioneer community (eg. if the disturbance is only one tree falling, there will still be soil)
44
Q

Describe biotic potential (r):

A
  • Highest per capita growth rate possible
  • Determined by the following factors:
    • Number of offspring per reproductive cycle
    • Number of offspring that survive long enough to reproduce
    • Age of reproductive maturity
    • Number of times individuals reproduce in a life span
    • Life span of individuals
45
Q

Describe the lag phase:

A

Period at beginning of population growth curve where growth is slow (only a few individuals to reproduce)

46
Q

Describe the stationary phase:

A
  • At the carrying capacity
  • Competition for resources (and other limiting factors) will eventually limit energy available for reproduction
  • Stationary phase - phase where birth and death rates are equivalent
47
Q

Describe carrying capacity (k):

A
  • Theoretical maximum population size the environment can sustain over an extended period of time
  • Number of individuals in a population that can live in a given environment without depleting resources they need or harming the habitat or themselves
  • Can change from year to year
  • Population may fluctuate around this in a state of equilibrium
48
Q

What are the factors that limit carrying capacity?

A
  • Density dependent
    • Generally biotic
    • Impact of these factors is increased with density of the population
      • Eg. disease
  • Density independent
    • Generally abiotic
    • Limit growth of a population regardless of its size/density
      • Eg. natural disaster
49
Q

Describe environmental resistance:

A
  • Combination of limiting factors
  • Prevents a population from growth at its biotic potential and determines the carrying capacity of the habitat
50
Q

Describe life strategies for oragnisms:

A
  • Vary with organisms and conditions
  • In some conditions it is advantageous to reproduce rapidly and produce many offspring
  • In other conditions it is beneficial to have longer lifespan and few offspring
  • r-selected and k-selected strategies are two extremes of a continuum of life strategies
51
Q

Describe r-selected life strategies:

A
  • Species reproduce close to their biotic potential
  • Short life span
  • Early reproductive age
  • Large broods of offspring the receive no parental care
  • Take advantage of favourable conditions when they are present (eg. the summer months in Alberta)
  • Exhibit more of a j shaped growth curve
  • Eg. rabbits, insects, annual plants
52
Q

Describe k - selected life strategies:

A
  • Populations that live close to carrying capacity
  • Few offspring per reproductive cycle
  • Parental care
  • Offspring take time to mature and reach reproductive age
  • Tend to be larger
  • Few offspring but lots of energy invested in getting those offspring to reproductive age
  • Exhibit more of an s shaped growth curve
  • Eg. bears, people
53
Q

Describe the realities of life strategies:

A
  • Most populations exhibit combinations of r and k life strategies
    • Eg. coniferous trees
  • Populations can only be explained as r or k selected in comparison to other populations
    • Eg. gophers a k - selected in comparison to mosquitoes but r - selected in comparison to humans
  • An understanding of life strategies can be useful for predicting success pf a species in a given environment
54
Q

Describe population density:

A
  • Number of organisms (N) in a given area (A) or volume (V)
  • Dp = N/A or N/V
  • Resulting unit is either going to be #/ unit of area (ag. km^2) or number/unit of volume (eg. mL)
  • Can use the resulting number to estimate the number of organisms in a given region
55
Q

Describe population distribution:

A
  • Refers to the way organisms are spread throughout a given area
  • Uniform - evenly dispersed
  • Random - spread through an ares but not completely even (no pattern)
  • Clumped - organisms are in groups (most common)
56
Q

Describe the factors affecting distribution patterns:

A
  • Distribution of resources in a habitat
    • Tend to congregate around resources
    • This is why clumped is most common
  • Reproductive strategies
    • Eg. organisms exhibiting asexual reproduction tend to be clumped
  • May very with life stages
    • Eg. mosquito larvae indicate clumped distribution, adults are more random
57
Q

Describe population gorwth:

A

Certain factors can contribute to the size of a population:
- Number of births
- Number of deaths
- Immigration
- Emigration
- Natality
- Morality

58
Q

How do you calculate change in population size (△N)

A
  • △N = [ b + i ] - [ d + e ]
  • △N = change in population
  • b = number of births
  • i = number of immigrants
  • d = number of deaths
  • e = number of emigrants
  • Note: migration of an entire population does not count as immigration or emigration
59
Q

Describe the rate of population growth:

A
  • Can be an important influence of the ecosystem as a whole
  • Population explosion - very rapid population growth - often occurs with invasive species
  • Population crash - very rapid decrease in population size
60
Q

How do you calculate the rate of population growth?

A
  • gr = △N/△t
  • gr = growth rate
  • △N = change in population (Nf - Ni)
  • △t = change in time (tf - ti)
61
Q

Describe per capita growth rate:

A
  • The basic growth rate calculation does not take into account initial size of a population
  • Large populations grow faster than small ones (more organisms present then can reproduce)
  • Per capita growth rate calculates the rate of change per individual - can then compare growth rates of populations with various sizes
62
Q

What is the calculation for per capita growth rate?

A

egr = △N/N
egr = per capita growth rate
△N = change in population
N = original number of individuals

63
Q

Describe population growth curves:

A
  • Plotted as number of organisms over time
  • J - shaped when exponential growth occurring (due to unlimited resources
  • S - shaped for organisms which exhibit slower population growth and reach a carrying capacity
64
Q

Describe a j - shaped growth curve:

A
  • Occurs when organisms have unlimited resources and ideal living conditions
65
Q

Describe an s - shaped growth curve:

A
  • Occurs with organisms which reach a stable equilibrium of resources and organisms - when resources limit growth - also called logistic growth

Biology 30 (7 decks)

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