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populations and evolution Flashcards

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Biology 101 flashcards
1
Q

Population

A

A population is a group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.

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2
Q

Gene pool

A

All of the alleles of all the genes of all the individuals in a population at a given time

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3
Q

Allelic frequency

A

the number of times an allele occurs within the gene pool.

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4
Q

Assumptions of the Hardy Weinberg equation (5)

A
  1. no mutations arise
  2. the population is isolated (no flow of alleles into or out of the population).
  3. there is no selection (all alleles are equally likely to be passed to the next generation)
  4. population is large
  5. mating within the population is random
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5
Q

evolution

A

the change in allele frequencies of a population. (if allele frequencies do not change over time then we can assume that the species is not evolving).

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6
Q

genetic diversity

A

the total number of different alleles in a population

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7
Q

hardy weinburg equation for allele frequency

A

p + q = 1

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8
Q

hardy weinburg equation for genotypes

A

p2 + 2pq + q2 = 1.0

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9
Q

intra specific variation

A

differences between organisms of the same species

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10
Q

interspecific variation

A

variation between members of the same species

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11
Q

Polygenic inheritance

A

where multiple alleles contribute a small amount to the phenotype

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12
Q

discontinuous variation

A
  • categorical
  • caused by a single gene
  • little influence from the environment
  • qualitative
  • shown on a bar chart
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13
Q

continuous variation

A
  • characteristics that don’t fall into distinct groups but instead show normal distribution (eg. height)
  • caused by many genes (polygenic inheritance)
  • can be influenced by the environment
  • quantitative
  • shown on a histogram
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14
Q

speciation

A

the evolution of new species from existing ones

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15
Q

genetic drift

A

this is the idea that allele frequencies can change simply due to chance. for example, in a small population, some individuals will fail to reproduce due to bad luck as opposed to being poorly adapted.

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16
Q

The founder effect

A

where a few individuals from an existing population colonise a new environment. Because the new population is small, many alleles will not have been brought to the new environment so the population will develop with less genetic diversity than the original population. This also causes interbreeding to increase as there is a reduced number of mates and so the genetic diversity is restricted to just a few alleles.

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17
Q

genetic bottleneck

A

when an event kills a significant percentage of a population (eg. a flood). If an individual is carrying a rare allele (eg. due to a mutation) , it could be completely lost from the population and reduce genetic diversity. This also causes interbreeding to increase as there is a reduced number of mates and so the genetic diversity is restricted to just a few alleles.

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18
Q

artificial classification

A

divides organisms by analogous characteristics. They have the same functions but not necessarily the same evolutionary origins.

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19
Q

phylogenetic classification

A

homologous characters. they have the similar evolutionary origins (regardless of function),

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20
Q

The limitations of investigating genetic diversity using observable characteristics

A

often characteristics are polygenic and so the characterise is continuous.
differences may be the result of the environment.

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21
Q

reproductive isolation

A

pre zygotic: (before the zygote forms because the gametes never meet)

  • habitat: where populations use different habitats so are unlikely to encounter one another.
  • temporal: where populations inhabit the same area but are active or reproduce at different times
  • behavioural: different courtship displays
  • mechanical: reproductive parts do not fit each other

Postzygotic: (after a zygote forms they might not develop)

  • hybrid sterility: hybrids formed will be sterile because they cannot produce viable gametes.
  • gametic: the gametes formed may be genetically or biochemically incompatible
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22
Q

allopatric speciation

A

the form of speciation where two populations become geographically isolated.

23
Q

sympatric speciation

A

where speciation occurs without any geographical operation.

24
Q

marking scheme points for sympatric speciation

A
  1. occurs in the same habitat / environment
  2. a mutation leads to a change in the organisms activity
  3. no gene flow
  4. different alleles passed on
  5. disruptive natural selection
  6. eventually species cannot interbreed to produce fertile offspring
25
Q

community

A

populations of different species

26
Q

ecosystem

A

the abiotic and biotic factors.

a community and the non-living components of the environment.

27
Q

ecology

A

the study of inter-relationships between organisms and their environment

28
Q

Population

A

a group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed.

29
Q

carrying capacity

A

an ecosystem supports a certain size of population of a species.

30
Q

community

A

all the populations of all the different species living and interacting in a particular place at a particular time.

31
Q

habitat

A

the place where an organism normally lives

32
Q

niche

A

an organisms particular role in a community. It describes how an organism fits into the environment, referring to where an organism lives and what it does there

33
Q

competitive exclusion principle

A

no two species occupy exactly the same niche. Interspecific competition.

34
Q

population size

A

the number of individuals in a population

35
Q

predation

A

one organism is consumed by another

36
Q

effects of the predator prey relationship

A
  1. predator eats pray so reduces the population of prey
  2. with fewer prey available for the predator, theres more competition for the predators
  3. predator population is reduced as some individuals are unable to obtain prey
  4. fewer predators means less prey is eaten, so more survive and reproduce meaning that the prey population increases again
    cycle repeats
37
Q

abundance

A

the number of individuals of a species in a given space

38
Q

point quadratic

A

horizontal bar supported by two legs. At set intervals along the horizontal bar are ten holes, through each of which a long pin may be dropped. Each species that the pin touches is then recorded.

39
Q

abundance measured in frequency

A

this is the likelihood of a particular species occurring in a quadratic. e.g. it occurs in 15/30 quadrats and so the frequency is 50%. This is useful if the species is hard to count e.g. grass. It gives a quick idea of the species present and their general distribution within the area. However, it does not provide information on the density and detailed distribution of a species.

40
Q

abundance measured in percentage cover

A

this is an estimate of the area within a quadratic that a particular plant species covers. It is useful where a species is particularly abundant or is difficult to count. Advatagous because data can be collected rapidly and individual plants do not need to be counted, It is less useful where organisms occur in several overlapping layers.

41
Q

mark release recapture equation

A

estimated population size = total number of individuals in the first sample X total number of individuals in the second sample / number of marked individuals recaptured

42
Q

mark release recapture assumptions

A
  • proportion of marked to unmarked individuals int he second sample is the same as the proportion of marked to unmarked individuals in the population as a whole
  • the marked individuals released from the first sample distribute themselves evenly amongst the remainder of the population and have sufficient time to do so.
  • the population has a definitive boundary so that there is no immigration or emigration.
  • there are few, if any, deaths and births within the population
  • the method of marking is not toxic to the individual not does it make the individual more liable to predation
  • the mark is not lost or rubbed off during the investigation
43
Q

Succession

A

describes the changes over time in the species that occupy a particular area.

44
Q

how may barren land arise

A
  • a glacier retreating and depositing rock
  • sand being piled into dunes by the wind or sea
  • volcanoes erupting and depositing lava
  • lakes or ponds being created by land subsiding
  • silt and mud being deposited at river estuaries
45
Q

succession overview

A

At each stage a new species colonises the area, and this may change the environment. This could alter the environment to make it less suitable for existing species or more suitable for the other species with its different adaptations(and as a result the new species may outcompete the existing and one and so take over the given area).
In this way there is a series of successional changes that alter the abiotic environment. These can result in a less hostile environment that makes it easier for other species to survive. This leads to new communities forming and the biodiversity may increase.

46
Q

first stage of succession

A

First stage is the colonisation of an inhospitable environment by organisms known as pioneer species. They make up a pioneer community and often has characteristics that suit them to colonisation such as:

  • asexual reproduction so that a single organism can rapidly multiply to build up a population
  • the production of vast quantities of wind dispersed seeds or spores, so they can easily reach isolated situations
  • the ability to photosynthesis, as light is normally available but other food is not.
  • ability to fix nitrogen from the atmosphere because, even if there is soil it will have few nutrients.
  • tolerance to extreme conditions

example: lichen

47
Q

Second stages of succession

A

as organisms of the pioneer species die, they release sufficient nutrients to support a community of small plants. In this way the abiotic environment has changed.

Also, weathering of the rock can produce sand or soil.

Different plant types available determine the animals (habitats and food).

Organic material can hold water, making it easier for other organisms to grow.
Mosses are typically the next stages of succession.

48
Q

climax community

A

this is the stable state that compromises a balanced equilibrium of species with few, if any, new species replacing those that have become established. There is lots of biodiversity. It remains more or less stable for a long period of time and consists of animals as well as plants.

49
Q

common features of succession

A
  1. the abiotic environment becomes less hostile
  2. a greater number and variety of habitats and niches
  3. increased biodiversity (but then decreasing once the climax community is reached).
  4. more complex food webs which leads to an increased biomass (particularly in mid succession).
50
Q

Secondary Succession

A

When land that has already sustained life is suddenly altered (eg. due to land clearance for agriculture or due to a forest fire). The process by which the ecosystem returns to its climax community is by succession (but a much quicker version). it is quicker because the soil already exists and often seeds/spores remain alive in the soil. But because the land has been altered in some way, some of the species in the climax community will be different.

51
Q

conservation

A

the management of the earths natural resources by humans in a way that maximises their use for the future. This involves active interventions by humans to maintains ecosystems and biodiversity.

52
Q

reasons for conservation

A
  • personal (maintaining our planet and therefore our life support system)
  • ethical
  • economic (genes may be valuable in the future)
  • cultural
53
Q

conservation techniques

A

eg. burning or grazing

Bio (11 decks)

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