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AQA ALEVEL BIOLOGY P1/P2 > 4. DIVERSITY > Flashcards

4. DIVERSITY Flashcards

1
Q

What is Species Diversity?

A
  • number of different species
  • number of individuals for each species
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1
Q

What is Biodiversity?

A
  • variety in an ecosystem
  • variety of habitats and variety of species
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2
Q

What is Genetic Diversity?

A
  • variety of alleles in a species population
  • the larger number of individuals in a species, the larger the genetic diversity
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3
Q

Benefit of high species diversity?

A
  • Stable ecosystem
  • each species is less likely to become extinct (due to high genetic diversity)
  • & if a species does become extinct it will not affect the food chain as there are other species available
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4
Q

How to measure Species Diversity for an area?

A
  • Species Diversity Index
  • takes into account the number of different species and how many individuals there are for each species
  • the larger the species diversity index, the larger the species diversity
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5
Q

How does deforestation lower species diversity?

A
  • (deforestation is the removal of trees for wood & space)
  • decreases plant species diversity
  • less variety of habitats
  • less variety of food sources
  • decreases animal species diversity
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6
Q

How does agriculture/farming lower species diversity?

A
  • deforestation to make space for farm
  • only grow a few plants & keep a few animal species
  • selectively breed plants & animals
  • use pesticides to kill other species
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7
Q

What is Classification?

A

placing organisms into groups

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8
Q

What is Hierarchical Classification?

A
  • large groups divided into smaller groups with no overlap
  • domain, kingdom, phylum, class, order, family, genus, species
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9
Q

What is Binomial Naming System?

A
  • using Genus name and Species name to name organism
  • Genus name first in capital, Species name second in lower case
  • e.g. tiger = Felix tigris
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10
Q

What is a Species?

A

a group of individuals with similar characteristics that can interbreed to produce fertile offspring

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11
Q

Why are the offspring from 2 different species mating infertile?

A
  • offspring will have a odd number of chromosomes
  • therefore, cannot perform meiosis, cannot produce gametes
  • example: horse + donkey = mule,
    mule is infertile, horse has 64 chromosomes/donkey has 62 chromosomes,
    horse gamete has 32 chromosomes/donkey gamete has 31 chromosomes, therefore, mule has 63 chromosomes
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12
Q

What is Phylogenetic Classification?

A

based on evolutionary relationships – how closely related different species are and how recent a common ancestor they have

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13
Q

3 ways of comparing relationship between different species?

A

DNA Hybridisation: comparing DNA base sequence

  • take DNA from 2 species to be compared
  • radioactively label one of the DNA
  • heat both sets so double strand separates
  • cool so single strands join together
  • look for Hybrid DNA (one strand from species A, one strand from species B)
  • identify Hybrid DNA by 50% radioactivity
  • heat Hybrid DNA to measure similarity
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14
Q

results of DNA hybridisation.

A

results = higher temperature required
more hydrogen bonds present
more complementary base pairing
more similar the base sequence
more similar the species
more closely related
more recent a common ancestor

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15
Q

whats the AA sequence?

A

comparing AA sequence for the same protein (e.g. haemoglobin in mammals)

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16
Q

results of AA sequence?

A

more similar the AA sequence
more similar the DNA base sequence
more similar the species
more closely related
more recent a common ancestor

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17
Q

What is Variation?

A

difference in characteristics between organisms

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18
Q

Types of Variation?

A

intraspecific = differences between organisms of the same species
interspecific = differences between organisms of different species

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19
Q

Causes of Intraspecific Variation?

A

Genetic Factors = same genes but different alleles (allele are different type/forms of genes)

Environmental Factors = climate, availability of resources, pathogens or the occurrence of other competing species,

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20
Q

Causes of Interspecific Variation?

A

Genetic Factors = different genes and different alleles

Environmental Factors = climate, availability of resources, pathogens or the occurrence of other competing species,

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21
Q

Types of Characteristics?

A

Discontinuous and Continuous

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22
Q

Properties of Discontinuous Characteristics?

A

characteristics fall into certain groups with no overlap (e.g. blood group) – determined by genetics only (a single gene) like human blood only four blood groups are possible (A, B, AB or O).

23
Q

Properties of Continuous Characteristics?

A

characteristics show a range (e.g. height) – determined by genetics (a few genes, polygenes) and environment

24
Q

What is Genetic Diversity?

A

genetic variation, the variety of alleles within a population of a species

25
Q

Benefit of high genetic diversity?

A

species able to adapt with changes in the environment e.g. if a new disease arises, some individuals will have characteristics to survive, and will reproduce passing on their alleles, so the species does not become extinct

26
Q

What can lower genetic diversity?

A

small population size (e.g. founder effect – where the numbers start low, or genetic bottleneck – where the numbers decrease)

27
Q

What is natural selection and adaptation?

A
  • variation in population of species
    (genetic diversity/genetic variation/variety in gene pool)
  • new alleles arise by random mutation
  • environment applies a selection pressure on the population
  • those with favourable characteristics/favourable alleles/selection advantage/better adapted survive, the others die [natural selection]
  • the ones that survive will reproduce, passing on their favourable alleles
  • if this happens for many generations, then that characteristic will become most common – the allele will become more frequent [adaptation]
28
Q

What are the 3 types of selection?

A

stabilising and directional
disruptive

29
Q

What is stabilising selection?

A
  • when the environment favours those with the most common characteristic – those on the extreme dies out
  • the common characteristic increases in proportion
  • the range (standard deviation) will reduce
  • like birth weights
30
Q

What is directional selection?

A
  • when the environment favours those individuals with characteristics on one of the extremes
  • over time this will become the most common characteristic
  • normal distribution will shift to that extreme
31
Q

What is a Gene?

A
  • a section of DNA that codes for a protein
  • made out of intron and exon
  • intron = non-coding DNA (function e.g. turns gene on or off)
  • exon = coding DNA (codes for protein)
32
Q

How does a Gene/Exon code for a Protein?

A
  • made out of a sequence of bases
  • each 3 bases code for 1 amino acid (called triplet code)
  • therefore,
  • sequence of bases
  • determines sequence of triplet codes
  • which determine the sequence of AAs = polypeptide chain/primary structure (folds to secondary, then to tertiary/quaternary)
33
Q

Properties of triplet code?

A
  • degenerate = each AA has more than one triplet code
  • non-overlapping = each base is read only once
  • stop codes = occur at end of sequence – do not code for an AA
34
Q

How does a mutation lead to a non-functional enzyme?

A
  • change in base sequence
  • change in sequence of triplet codes
  • change in sequence of AAs
  • change in primary structure
  • change in hydrogen/ionic/disulfide bonds
  • change in tertiary structure (3D shape)
  • change in active site shape
  • substrate no longer complementary
  • can no longer form enzyme-substrate complex
35
Q

How is a protein assembled?

A
  • by transcription and translation
  • transcription = production of a single stranded complementary copy of a gene (called mRNA)
  • translation = use sequence of codons on mRNA to assemble protein (tRNA brings in AAs)
36
Q

DNA vs RNA?

A
  • deoxyribose sugar vs ribose sugar
  • thymine vs uracil
  • double stranded vs single stranded
  • one type vs two types (mRNA and tRNA)
37
Q

What is mRNA?

A
  • messenger RNA
  • single stranded complementary copy of a gene
  • carries the code for assembling protein (on DNA called triplet code, on mRNA called codon)
38
Q

What is tRNA?

A
  • transfer RNA
  • single stranded RNA folded over into a ‘clover leaf’ shape (held by hydrogen bonds between the bases)
  • has an AA attachment site on the top
  • has 3 specific bases on the bottom (anticodon)
  • anticodon binds to complementary codons on mRNA
39
Q

What is Transcription?

A
  • occurs in nucleolus of nucleus
  • producing a single stranded complementary copy of a gene (called mRNA)
  • DNA is double stranded, 1 strand called coding strand & 1 strand called template strand, the template strand will be used to build mRNA
  • process,
  • DNA Helicase breaks the hydrogen bonds between complementary bases in the gene
  • the double strand of the gene unwinds
  • leaves 2 separate strands (1 coding strand and 1 template strand)
  • complementary RNA nucleotides bind to exposed bases on the template strand
  • RNA Polymerase joins the sugar-phosphate backbone of the RNA strand
  • leaves pre-mRNA (contains introns and exons)
  • the copies of the introns are removed by splicing
  • leaves mRNA
40
Q

What is Translation?

A
  • takes place on ribosomes of Rough Endoplasmic Reticulum
  • uses the sequence of codons on the mRNA to assemble the protein (tRNA brings in AAs)
  • process,
  • mRNA leaves nucleus via nuclear pore
    -mRNA attaches to a ribosome
  • complementary tRNA carrying specific AAs bind to the codons on mRNA via their anticodon
  • the AAs on the tRNA are joined by peptide bonds
  • moves to next codon and repeats this with more AA being joined until it reachs stop codon on end
  • releases the protien thats made
41
Q

What does Meiosis produce?

A

4 genetically different cells, haploid (half the amount of chromosome/DNA)

42
Q

Benefits of Meiosis?

A

produces gametes which will be used in sexual reproduction in animals & plants (2 gametes fuse to form a zygote, zygote develops into organisms)

43
Q

Stages of Meiosis?

A

Interphase/Meiosis I/Meiosis II/Cytokinesis

44
Q

Interphase?

A

G1: protein synthesis
S: DNA replication (doubles set of DNA)
G2: organelle synthesis

45
Q

Meiosis I?

A

Prophase I: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form, crossing over occurs
Metaphase I: homologous pair of chromosomes line up in middle of cell and attach to spindle fibre via centromere
Anaphase I: spindle fibres pull, homologous pair of chromosomes separate to opposite sides by independent assortment
Telophase I: chromosomes uncoil, nucleus reforms (left with 2 nuclei)

46
Q

Meiosis II?

A

Prophase II: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form
Metaphase II: chromosomes line up in middle of cell and attach to spindle fibre via centromere
Anaphase II: spindle fibres pull, centromere splits, sister chromatids move to opposite sides
by independent assortment
Telophase II: chromatids uncoil, nucleus reforms (left with 4 genetically different nuclei)

47
Q

Cytokinesis?

A

separating cell into 4 (each receives a nucleus and organelles/cytoplasm)

48
Q

How does Meiosis produce Variation?

A

Crossing Over and Independent Assortment

49
Q

What is crossing over?

A

occurs in Prophase I of Meiosis I homologous pairs of chromosomes wrap around each other and swap equivalent sections of chromatids – produces new combination of alleles

50
Q

What is independent assortment?

A

in Anaphase I of Meiosis I – the homologous pairs of chromosomes separate
- in Anaphase II of Meiosis II – the chromatids separate
- independent assortment produces a mix of alleles from paternal and maternal chromosomes in gamete

51
Q

What happens to DNA mass in meiosis?

A

quarters

52
Q

What happens to Chromosome number in meiosis?

A

halves (haploid)

53
Q

What is Mutation and the types?

A
  • Change in DNA
  • 2 types: Chromosome Mutation and Gene Mutation
54
Q

What causes mutation?

A

random or due to mutagens (e.g. chemicals, radiation)

55
Q

What is a Chromosome Mutation?

A
  • In plants, inherit more than one diploid set of chromosomes – called polyploidy
  • In animals, homologous pair of chromosome do not separate in meiosis, so either inherit one extra or one less chromosome – called non-disjunction
56
Q

What is a Gene Mutation?

A
  • a change in the base sequence of DNA
  • 2 types = substitution and insertion/deletion
  • substitution = replace one base for another, changes one triplet code
    can be silent (new triplet code codes for same AA), mis-sense (codes for a different AA, so protein shape changes slightly), non-sense (codes for a stop codon, so polypeptide chain not produced)
  • insertion = adding a base, deletion = removing a base both insertion/deletion causes frameshift, all the triplet codes after the mutation changes, so normal polypeptide chain/protein not produced

AQA ALEVEL BIOLOGY P1/P2 (8 decks)

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