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A Biology A Level > Topic 4 > Flashcards

Topic 4 Flashcards

1
Q

What is a habitat?

A
  • The place an organism lives
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2
Q

What is a species?

A
  • A group of organisms which can interbreed to produce fertile offspring.
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3
Q

What is a population?

A
  • A group of interbreeding individuals in an area
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4
Q

What is a community?

A
  • All the populations within a habitat
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5
Q

What is a niche and what does it include?

A
  • It is the way an organism exploits its environment.
  • Includes interactions with other organisms and interactions with non living environment.
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6
Q

What is biodiversity?

A
  • It is the variety of species in an area
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7
Q

What is species diversity?

A
  • The number of species and number of individuals in a species within an area
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8
Q

What is genetic diversity?

A
  • Measure of all alleles in the gene pool of a species
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9
Q

What can you look at to measure genetic diversity?

A
  • Genotype, genetics of an organism
  • Phenotype, observable characteristics of an organism
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10
Q

What is species richness?

A
  • Refers to different number of species present in an area
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11
Q

What is species evenness?

A
  • Measures the relative abundance of different species in an area
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12
Q

What is Simpsons biodiversity index?

A
  • Quantitative measure of diversity in a habitat to give a comparable score.
  • d = N(N - 1)/sum of n(n - 1)
  • N = total number of all species, n = number of organisms in a species
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13
Q

What are polymorphic genes?

A
  • Genes that exist in three or more different versions or alleles.
  • Greater number of genes have greater genetic diversity.
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14
Q

What does the Heterozygosity Index measure?

A
  • Genetic diversity within a species
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15
Q

What is the equation for the Heterozygosity Index?

A

H = no of heterozygous/number within population

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16
Q

What is a heterozygous?

A
  • One with a different allele on each chromosome.
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17
Q

Where does genetic diversity come from?

A
  • Mutations
  • Random selection
  • Meiosis
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18
Q

What are adaptations?

A
  • They enhance survival in a habitat
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19
Q

What are anatomical adaptations?

A
  • Change to structural features of an organism for survival
  • eg. otter is streamlined to glide through water
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20
Q

What are behavioural adaptations?

A
  • Actions and behaviour is modified for survival
  • eg. earthworm burrows on vibrations to avoid predators
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21
Q

What are physiological adaptations?

A
  • Changes to internal workings and processes for survival
  • eg. stomata close during dry conditions to avoid water loss
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22
Q

What is evolution?

A
  • A change in allele frequency over time
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23
Q

What is convergent evolution?

A
  • Evolution in common traits between two phylogenetically distinct species due to similar selection pressures.
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24
Q

How does natural selection occur?

A
  • New alleles created through mutation
  • A selection pressure occurs in the environment
  • Organisms with advantageous allele are more likely to survive, reproduce and produce offspring
  • Their offspring are more likely to have the allele, so it becomes more common in the population
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25
Q

What is a gene pool?

A
  • All the alleles of all the genes present in a population of a species.
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26
Q

What is the benefit of having a bigger gene pool?

A
  • Having more genetic diversity.
  • Possess alleles which allow them to survive.
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27
Q

What is the frequency of an allele?

A
  • Proportion of individuals that have one copy of an allele
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28
Q

When do allele frequencies change?

A
  • Change in response to selection pressures by natural selection.
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29
Q

What are the three types of genotypes?

A
  • Homozygous dominant (FF)
  • Heterozygous (Ff)
  • Homozygous recessive (ff)
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30
Q

What is the Hardy Weinburg equation?

A

p^2 (freq of homozygous dominant) + 2pq (freq of heterozygous) + q^2 (freq of homozygous recessive) = 1

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31
Q

What are the assumptions of the Hardy Weinberg equation?

A
  • Large population
  • No mutations
  • No natural selection
  • Random mating
  • Isolated population
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32
Q

What factors must be needed to adapt to new conditions?

A
  • Strength of selection pressure
  • Size of gene pool
  • Reproductive rate
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33
Q

What is speciation?

A
  • Formation of a new species from an existing one
34
Q

What must happen for speciation to occur?

A
  • Become reproductively isolated and unable to produce fertile offspring.
35
Q

What is allopatric speciation?

A
  • Isolation due to geographical isolation
  • Eg. mountain range
36
Q

What is sympatric speciation?

A
  • Isolation due to reproductive isolation
  • Eg. seasonal changes or behavioural changes
37
Q

How does allopatric isolation lead to speciation?

A
  • Isolation prevents individuals breeding with rest of population
  • The two groups respond to different selection pressures which causes random mutations
  • They then cannot interbreed to produce fertile offspring.
38
Q

What is endemism?

A
  • A species only found in one geographical location
39
Q

What information should you collect for studies of biodiversity?

A
  • Presence of endemic species
  • Use of a diversity index
  • Genetic diversity of populations
  • Species richness
40
Q

What is the order of the hierarchy of classification?

A

Kingdom
Phylum
Class
Order
Family
Genus
Species

41
Q

What is phylogeny?

A
  • The study of evolutionary relationships between organisms.
42
Q

What is molecular phylogeny?

A
  • Study of molecular differences in DNA of proteins to show evolutionary relationships
43
Q

What are phylogenetic trees?

A
  • Show the relationships between species
  • Branches represent common ancestors and show relatedness.
44
Q

What are the 3 domains?

A
  • Eukaryote
  • Archea
  • Prokaryotes
45
Q

What are the 5 kingdoms?

A
  • Prokaryotae
  • Protoctista
  • Fungi
  • Plantae
  • Animalia
46
Q

What does climate change cause in animals?

A
  • Causes migration or death
  • Creating low genetic diversity
47
Q

What are the human impacts on the earth?

A
  • Alters ecosystems
  • Uses biological resources
  • Mines resources eg. fossil fuels
48
Q

What is the function of the plant cell wall?

A
  • Made of cellulose and provides support for the cell
49
Q

What is the function of the middle lamella?

A
  • Sticks plant cells together to provide stability.
50
Q

What is the function of the plasmodesmata?

A
  • Narrow channels of cytoplasm between two plant cells to transport substances between them and communicate.
51
Q

What is the function of a pit?

A
  • Allows plant cells to exchange substances.
52
Q

What is the function of chloroplasts?

A
  • Where photosynthesis occurs.
53
Q

What is the function of an amyloplast?

A
  • Plant storage granules containing starch, which convert back to glucose when the plant needs it for respiration.
54
Q

What is the function of the vacuole?

A
  • Stores cell sap which keeps the cell turgid and to digest molecules
55
Q

When is plant cell turgid or flaccid?

A
  • When there is high water potential, water rushes into the cell but cell wall stops from bursting appearing turgid.
  • When there is low water potential, water leaves the cell appearing flaccid.
56
Q

What is cellulose?

A
  • Unbranched polysaccharide
  • Long chain of beta-glucose with 1,4 glycosidic bonds.
57
Q

What is a microfibril?

A
  • Bundle of cellulose chains formed by hydrogen bonds
  • Beta glucose joined in condensation reaction
  • Unbranched chain
58
Q

What holds microfibrils together?

A
  • Polysaccharides known as hemicelluloses and pectins
59
Q

What is the xylem and how is it adapted for its function?

A
  • Transport water and mineral ions from roots to plant.
  • Dead, hollow cells, thickened with lignin.
  • One continuous tube for transport
  • Pits for movement in and out of cells.
60
Q

What is the phloem and how is it adapted to it’s function?

A
  • Transport organic solutes and sugars from where they are made (source) and where they are used (sinks)
  • Sieve tube elements to transfer material between adjacent cells.
  • Companion cells control transport of sap.
61
Q

What is the sclerenchyma and how is it adapted to it’s function?

A
  • Stiffened, hollow cells with lignin deposited in walls.
  • Provide structure for the cells
62
Q

Why are plant fibres so strong?

A
  • Strong arrangement of microfibrils in mesh type pattern
  • Secondary cell wall containing lignin
63
Q

What is the transpiration stream?

A
  • Constant movement of water from roots to leaves
  • Water is pulled up as it evaporates out of the stomata due to tension of H bonds and cohesive forces
64
Q

What is the cohesion-tension theory?

A
  • Forces of water molecules movement through xylem (cohesion)
  • Water adheres to lining of the walls (adhesion)
65
Q

What is translocation?

A
  • Movement of sugars through phloem
  • Sugars are actively loaded into sieve tube + water potential source decreases
66
Q

What is the process of active loading?

A
  • Sucrose into sieve tube elements
  • H+ ions pumped from companion cells to surrounding lead creating a diffusion gradient
  • H+ ions diffusion back into companion cell with sucrose by cotransporter protein
  • Sucrose diffuses into sieve tube elements
67
Q

How are plant fibres useful for humans?

A
  • Very strong for ropes and fibres
68
Q

Why are plant fibres sustainable?

A
  • Less fossil fuels
  • Replanted for next generation
  • Biodegradable
  • Cheaper and easier to grow
69
Q

What is lignin?

A
  • Tough, waterproof substance which is found in xylem and sclerenchyma cell wall to provide strength
70
Q

What is the cohesion-tension theory?

A
  • Shows pulling forces of water molecules through xylem (cohesion)
  • And water adhering to lining of the cell (adhesion)
71
Q

What happens if plants don’t get nitrate ions?

A
  • They can’t produce amino acids
  • They become yellow (chlorosis)
72
Q

What happens if plants don’t get magnesium ions?

A
  • They have insufficient chlorophyll
  • Leaves turn brown in patches
73
Q

What happens if plants don’t get calcium ions?

A
  • They have weakened cell walls and cell membranes
  • Plant will have stunted growth
74
Q

What are sources vs sinks?

A
  • Sources load material into transport systems
  • Sinks removes material from transport systems
75
Q

What did Withering do?

A
  • Tested fox glove leaves to cure heart and muscle problems.
  • Made digitalis soup to test doses.
76
Q

What is pre-clinical testing?

A
  • Testing on cultures and then animals before humans.
77
Q

What are the phases of drug testing?

A
  • Phase I - healthy volunteers + low dose to see effectiveness and safe dosage
  • Phase II - people who has the disease + uses a placebo to measure psychological effects
  • Phase III - large groups of people + double blind trial where neither the patient nor doctor know who is receiving the treatment.
78
Q

What is needed for bacterial growth?

A
  • Ideal nutrients
  • Optimum temperature
  • Oxygen for aerobic respiration
79
Q

What are the uses of starch?

A
  • Extracted from plants to make bioplastics and biofuel
  • It is absorbent so when rehydrated the particles take up water.
  • Gelatinisation at high temperatures.
80
Q

What is the roles of zoos?

A
  • Captive breeding programmes
  • Increase numbers within a species
  • Maintain genetic diversity
  • Reintroduce animals to the wild.
81
Q

How is genetic variation lost?

A
  • Genetic drift - allele may not be passed on
  • Interbreeding depression - harmful alleles so less fit to survive
82
Q

How is genetic diversity conserved?

A
  • Through zoos, using stud books for interbreeding
  • Through seed banks, testing germination

A Biology A Level (8 decks)

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