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A Level Biology > 7. Inherited Change > Flashcards

7. Inherited Change Flashcards

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1
Q

Define species

A

Group of similar organisms that reproduce to produce fertile offspring

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2
Q

Define population

A

Group of organisms of the same species that occupies a particular space at a particular time that can potentially interbreed

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3
Q

Define allele frequency

A

Number of times an allele occurs within a gene pool

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4
Q

Define gene pool

A

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

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5
Q

How does a new species form?

A

Changes over time due to natural selection
Leads to changes in characteristics
Over time changes become so great that a new species forms

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6
Q

Define hardy- Weinberg principle

A

Used to calculate frequencies of alleles of a particular gene in a population.

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7
Q

What are the conditions that need to met in the hardy Weinberg principle?

A
  1. No mutations arise
  2. Large population
  3. Organisms reproduce by sexual reproduction
  4. Random mating
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8
Q

Define phenotypic variation

A

Differences in phenotypes between organisms of the same species

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9
Q

What is phenotypic variation caused by?

A

Genetic factors and environmental influences

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10
Q

Define genetic variation?

A

Same genes but will have different alleles of these genes

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11
Q

How does genetic variation arise?

A
  1. Mutations- sudden changes in genes so generation of new alleles, may be passed on
  2. Independent assortment of homologous chromosomes during metaphase I of meiosis
  3. Random fertilisation of gametes- sexual reproduction produces new combinations of alleles
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12
Q

How does the environment influence variation?

A

Affects the way genes are expressed

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13
Q

What is an example of environmental influence?

A

Climatic conditions such as temp, rainfall, soil conditions, pH, food availability

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14
Q

Define selection pressures

A

Environmental factors that limit the population of a species

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15
Q

What are biotic selection pressures?

A

Predation, competition, disease

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16
Q

What are abiotic selection pressures?

A

Changes in environment

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17
Q

What factors does natural selection depend on?

A
  1. Organisms produce more offspring that can be supported by the available supply of food, light, space
  2. There is genetic variety within the population
  3. Variety of phenotypes that selection operates against
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18
Q

What are the 3 main types of selection that affect the characteristics of a population?

A
  1. Stabilising selection- preserves the average phenotype (around the mean), favouring average individuals
  2. Directional selection- changes the phenotypes of a population by favouring phenotypes that vary in one direction from the mean= selection for one extreme phenotype

3.disruptive selection- favours individuals with extreme phenotypes

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19
Q

How is directional selection caused?

A

When change in environment favours a specific phenotype causing a selection pressure results in the mean shifting to the left or right.

Causes gradual change in allele frequency over several generations

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20
Q

What does disruptive selections cause?

A

Polymorphism- species of organisms that have two distinct forms that are genetically distant adapted to their environment
Exist in the same interbreeding population

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21
Q

Define evolution

A

Change in allele frequencies within a population over time

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22
Q

Define speciation

A

Evolution of a new species from existing ones

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23
Q

What is reproductive separation?

A

The process where a population becomes unable to interbreed successfully with another population leading to the accumulation of differences in their gene pools and potentially resulting in the formation of a new species

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24
Q

How are new species formed (reproductive selection)?

A

Population becomes geographically isolated
Experience different selection pressures
Changes in allelic frequency
Different phenotypes each combination of alleles produces will be subject to selection pressure that will lead to each population becoming adapted to its local environment= adaptive radiation
Unable to interbreed= diff species

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25
Define genetic drift
Occurs in small populations Random fluctuations in allele frequency within a population due to chance rather than natural selection Specific alleles can become more or less common leading to a shift in the genetic makeup of the population over time
26
Define allopatric speciation
Occurs as a result of geographical isolation eg. Physical barrier
27
How does allopatric speciation occur?
Population split into 2 or more groups separated by a physical barrier Isolated population evolve independently accumulating genetic differences over time If differences become significant enough the isolated populations can no longer interbreed= new species
28
Define sympatric speciation
Results within a population in the same area leading to them becoming reproductively separated
29
How does reproductive isolation occur?
Different breeding times, behaviours, anatomy prevent interbreeding between groups of the same area leading
30
What are the 7 types of isolating mechanism
1. Geographical 2. Ecological- pop inhabit different habitats 3. Temporal- breeding seasons don’t match 4. Behavioural- variation in courtship behaviour 5. Mechanical- anatomical differences 6. Gametic 7. Hybrid sterility- cannot produce viable gametes
31
Define ecology
Study of inter relationships between organisms and their environment- biotic and abiotic factors
32
Define community
Multiple populations of different species living and interbreeding in the same area
33
Define ecosystems
Communities interact with non-living components of the environment they live in
34
Within an ecosystems what are the 2 main processes to consider?
1. Flow of energy through the system 2. The cycling of elements within the system
35
What is the carrying capacity
Maximum stable population size of a species that an ecosystem can support
36
Define habitat
Place where an organism normally lives and its characterised by physical conditions and the other types of organisms present
37
Define ecological niche
Describes how an organism fits into the environment includes biotic and abiotic conditions
38
What is the competitive exclusion principle?
No two species occupy the same niche
39
What abiotic factors influence population size?
Temperature= each species have different optimum temp to best survive Light= ultimate source of energy, rate of photosynthesis increases with light intensity, plants grow more pH= impacts action of enzymes Water and humidity= scarce pop are small and consists of species well adapted to dry conditions
40
Define intraspecifc competition
Occurs when individuals of the same species compete with one another for resources eg. Food, water
41
How does intraspecifc compete ion determine population size?
Greater availability of resources the larger the population as less competition for resources
42
Define interspecific competition
Occurs when individuals of different species compete for resources such as food, light, water
43
How does interspecific competition cause different pop size?
When pop of two species are in competition one will normally have a competitive advantage over the other The pop of this species will gradually increase in size while the population of the other will decrease Complete removal of one species= competitive exclusion principle
44
Define predator
Organism that feeds on another organism= prey
45
What is the effect of predator prey relationship on population size?
1. Predators eat their prey reducing population of prey 2. Fewer prey available the predators are in greater competition with each other 3. The predator population is reduced 4. Fewer predators left fewer prey are eaten and so more survive 5. Prey population increases 6. More prey available the predators population increases
46
What are the 2 types of sampling techniques?
1. Random sampling using frame quadrats or point quadrats 2. Systemic sampling along a belt transect
47
What is a point quadrant?
Horizontal bar supported by 2 legs Each species the pin touches is recorded
48
What is a frame quadrat?
Square frame divided by string or wire into equally sized subdivisions The abundance of each species within the quadrat is recorded
49
What are three factors to consider when using quadrats?
1. The size of the quadrat to use= larger species require larger quadrats 2. The number of sample quadrats to record within the study area= the larger the number of sample quadrats the more reliable the results 3. The position of each quadrat within the study area= random sampling using frame
50
What is systematic sampling used for?
Measure the abundance and distribution of a species eg form a gradual change- line of succession
51
Define percentage cover
Estimate of the area within a quadrat that a particular plant species covers
52
What is the mark release capture equation?
Total no in first sample x total no in second sample / number of marked individuals recaptured
53
What does the mark release capture assume?
1. Marked individuals released in the first sample distribute themselves evenly amongst the population 2. Few deaths in population 3. Marked label is not lost or rubbed off 4. Marking doesn’t harm the individual
54
Define succession
Evolution of an ecosystem over time- changes in biotic and abiotic factors
55
Define pioneer species
Colonise inhabitable area
56
What are the features of pioneer species?
1. Asexual reproduction so that a single organism can rapidly multiply to build up a population 2. Tolerance to extreme conditions 3. Rapid germination of seeds on arrival as they do not require a period of dormancy
57
How is a climax community formed?
1. Weathering of the base rock producers sand or soil 2. Lichens die and decompose adding nutrients creating fertile humus- changing the abiotic environment so moss and fern can survive 3. Continuing erosion increases the amount of organic matter builds up a thicker layer of soil this makes it less hostile so more organisms can grow 4. This makes the environment less hostile so more suitable for flowering plants 5. This leads to more stable communities as food chains develop 6. Reaching climax community which is stable over long periods of time
58
Define climax community
Balanced equilibrium of a species with few new species
59
What are common features of during succession?
1. The abiotic environment becomes less hostile which leads to 2. A greater number and variety of habitats and niches that produce 3. Increased biodiversity as different species occupy these species- especially in early stages 4. More complex food webs leading to increased biomass
60
Define secondary succession
The recolonisation and development of an ecosystem after a disturbance like a forest fire removed plant life but left the soil intact
61
Define conservation
Management of the earths natural resources by humans so that maximum use of them can be made in the future Involves active intervention by humans
62
What are the main reasons for conservation?
1. Personal= to maintain our planet and therefore our life support system 2. Ethical= other species have lived longer than us should be allowed to coexist 3. Economic= gigantic pool of genes with capacity to make millions of substances
63
Define keystone species
Species that has a disproportionately large impact on the structure and function of an ecosystem relative to its abundance
64
Define gene mutation
A change in the sequence of base pairs in a DNA molecule
65
Define substitution of bases
A nucleotide in a DNA molecule is replaced by another nucleotide that has a different base
66
Define point mutation
Genetic change affecting a single nucleotide base pair in a DNA sequence
67
Define deletion of bases
Nucleotide is lost from the normal DNA sequence
68
Define chromosome mutations
Change in the structure or number of whole chromosomes
69
Define genetic diversity
Described as the total number of different alleles in a population
70
What does meiosis produce?
4 daughter cells that are genetically different
71
What happens in the first division of meiosis?
Homologous chromosomes pair up and their chromatids wrap around each other Equivalent portions chromatids exchange= crossing over
72
What happens in the second division of meiosis?
The chromatids move apart, four cells have been formed
73
How does meiosis bring about genetic variation?
Independent segregation of homologous chromosomes New combinations of maternal and paternal alleles by crossing over

A Level Biology (7 decks)

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