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A-level Biology > Topic 4 - Biodiversity and Natural Resources > Flashcards

Topic 4 - Biodiversity and Natural Resources Flashcards

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1
Q

Biodiversity

A

the variety of life, in particular the wealth, of different species that exists as a result of evolution by natural selection

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2
Q

Aspects of biodiversity

A

habitat/ecosystem diversity - range of habitats and conditions

species diversity - range and abundance of species in a habitat - species richness and relative species abundance

genetic diversity - genetic variation within a species (all the alleles)

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3
Q

Endemism

A

When a species is found only at a specific geographical location and is not naturally found anywhere else. Endemic species evolve in geographical isolation.

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4
Q

Measuring biodiversity with species richness

A
  • It is measured by random sampling of a habitat and then by counting the number of different species
  • The higher the number of species, the greater the species richness
  • Does not take relative abundance into account
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5
Q

Measuring biodiversity with species evenness

A
  • a community in which most of the species have similar abundances is said to have high evenness
  • does not take into account population size of each species
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6
Q

Measuring biodiversity with genetic diversity

A
  • Genetic diversity within species can be measured by calculating heterozygosity index
  • The greater the number of heterozygotes in a population, the greater the genetic diversity is
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7
Q

Heterozygosity index equation

A

H = number of heterzygotes/number of individuals in the population

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8
Q

Index of diversity formula

A

D = N(N-1)/∑n(n-1)

N = total number of organisms in all species
n = total number of organisms in one species

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9
Q

Niche

A

A species’ ecological role in its habitat, defined by the set of conditions, resources, and interactions it needs (or can make use of)

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10
Q

Adaptation

A

changes in the organism which help them to survive and reproduce according to the environment

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11
Q

Physiological adaptations

A

features of the internal workings of organisms that help them survive or reproduce e.g. a bumblebee’s biochemical pathway to produce venom

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12
Q

Behavioural adaptations

A

Any actions by organisms that help them survive or reproduce e.g. bumblebee waggle dance

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13
Q

Anatomical adaptations

A

structures we can see when we observe or dissect an organism e.g. bumblebee wings, hair, stinger

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14
Q

Evolution

A

The gradual change in the allele frequencies within a population over time that occurs due to natural selection. This helps species adapt to their habitat

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15
Q

Natural selection

A

the process whereby organisms better adapted to their environment are more likely to survive and reproduce so that advantageous alleles increase in frequency over time

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16
Q

Natural selection steps

A
  • population has variation due to genetic diversity in terms of meiosis, mutation, random fertilisation
  • the environment presents selection pressures, causing different individuals to have different chances of survival based on their characteristics
  • survivors have characteristics for adaptations that increase their chance of survival and reproduction
  • offspring inherit advantageous alleles
  • over many generations, favourable alleles become increasingly common in the population; allele frequency changes
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17
Q

Natural selection example

A
  • peppered moths have two varieties: light and dark
  • darkening of many trees due to pollution helped dark moths camouflage from predators and which helped them adapt and survive in comparison to light moths
  • they therefore became more common
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18
Q

Hardy-Weinberg: allele frequency equation

A

p + q = 1

p = dominant allele
q = recessive allele

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19
Q

Hardy-Weinberg: genotype frequency equation

A

p^2 + 2pq + q^2 = 1

p^2 = frequency of homozygous dominant genotype
2pq = frequency of heterozygous genotype
q^2 = frequency of homozygous recessive genotype

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20
Q

Hardy-Weinberg Principle

A

allele frequencies will remain the same from generation to generation assuming that there is no mutation, gene migration, selection, or genetic drift. Mating must be random and population size must be very large.

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21
Q

Allopatric speciation

A
  • occurs when populations of species split into one or more groups and become separated from each other by geographical barriers
    mechanism: geographical isolation
  • no genetic exchange can occur
  • if there is sufficient selection pressure or genetic drift, populations will diverge and form separate species
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22
Q

Sympatric speciation

A
  • biological and behavioural changes within a species may lead to reproductive isolation of one population from another
    mechanism: ecological separation (populations live in different environments within the same area) and behavioural separation (e.g. feeding, communication, social behaviours)
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23
Q

Classification

A

a means of organising the variety of life based on relationships between organisms using differences and similarities in phenotypes and in genotypes

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24
Q

Molecular phylogeny

A

The analysis of molecular differences in different organisms to determine the extent of their evolutionary relationship

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25
The five kingdoms
- animalia - plantae - fungi - protoctista - prokaryotae
26
Animalia
- multicellular eukaryotes, all heterotrophs (using food made by others) - their cells contain a nucleus but no cell walls or chloroplasts
27
Plantae
- multicellular eukaryotes that are autotrophs through photosynthesis - their cells contain a nucleus, chloroplasts and cellulose cell walls
28
Fungi
- usually multicellular eukaryotes, all heterotrophs through saprotrophic or parasitic nutrition - cells have nuclei and cell walls not made from cellulose (fungi)
29
Protoctista
- eukaryotes, both autotrophic and heterotrophic forms exist - most are unicellular but some are multicellular - all have a nucleus, some may have cell walls and chloroplasts
30
Prokaryotae
- prokaryotic organisms, bacteria and blue-green bacteria - often unicellular - cells have cell walls (not made of cellulose) and cytoplasm but no nucleus or mitochondria
31
Critical evaluation of data by the scientific community
- publishing of work in peer-reviewed and conference journals - hold scientific conferences - other scientists critically evaluate the work - wider scientific community can reproduce and extend the original - theory becomes accepted and taught and part of wider scientific community
32
Woese's discoveries
- defined Archaea as a new domain (group of single-celled prokaryotes) - developed the three-domain system based on evidence from chemical analysis (RNA sequencing)
33
Components of ultrastructure of plant cell
- cell wall - chloroplast - amyloplast - vacuole - tonoplast - plasmodesmata - pits - middle lamella
34
Amyloplast
- small, membrane bound organelle containing starch granules - responsible for storing starch in plants and converting it back to glucose when the plant needs it
35
Tonoplast
the membrane that surrounds the vacuole of the plant, controlling what can enter and leave
36
Plasmodesmata
- narrow threads of cytoplasm (surrounded by a cell membrane) that connect the cytoplasm of neighbouring plant cells - allows substances to be transported between plant cells and facilitates cell to cell communication
37
Pits
- very thin regions of the cell wall - pits in adjacent plant cells are lined up in pairs - facilitates transport of substances between cells
38
Middle lamella
- the outermost layer of the plant cell and acts like glue to stick adjacent plant cells together - provides stability to the plant
39
Starch structure
- composed of polysaccharides amylose and amylopectin - amylose has unbranched, coiled structure made up of repeated units of α-glucose joined by 1-4 glycosidic bonds - amylopectin has branched structure made up of repeated units of α-glucose joined by 1-4 glycosidic bonds in a linear chain and 1-6 glycosidic bonds at branch points - insoluble in water
40
Cellulose structure
- polymer consisting of long chains of β-glucose joined together by 1,4 glycosidic bonds only - OH group on carbon 1 is above, so one of the β monomers needs to invert to form a glycosidic bond - due to the inversion, many hydrogen bonds form between the long chains to form microfibrils
41
Starch function
- the storage polysaccharide of plants - mix of amylose and amylopectin means a mixture of rapid and slower glucose and energy release
42
Cellulose function
- main structural component of cell walls due to its strength, a result of many hydrogen bonds found between the parallel chains of microfibrils - high tensile strength allows cell walls to withstand turgor pressure - cellulose fibres and other molecules (e.g. lignin) found in the cell wall form a matrix which increases strength of cell walls - strengthened cell walls provides support to the plant
43
Pectin
polysaccharide that acts as glue that holds adjacent plant cells together by cementing their cell walls in the middle lamella
44
Hemicellulose
a polysaccharide that strengthens the cell wall by cross-linking cellulose microfibrils
45
Lignin
a polymer that adds strength and stiffness to plant cell walls
46
Secondary cell wall
- laid down in some some specialised cells (e.g. xylem and sclerenchyma) inside the primary wall - cells with secondary cell walls are usually long, and always flexible and strong - therefore useful to humans as fibres such as flax and cotton - thicker and impregnated with lignin, which makes it rigid and waterproof
47
Sclerenchyma function, location and adaptations
- provides structural support - strengthens plants by making them stiffer and giving greater tensile strength - have lignin deposited in cell walls for strength and waterproofing, no pits - die once lignified, leaving behind a hollow fibre with end walls - strength depends on length and degree of lignification - located outside the vascular bundle in the stem
48
Xylem function, location and adaptations
- transports water and minerals in one direction only - provides support by stiffening cell wall - lignin provides support + waterproofing to long, hollow structure - large lumen aids mass flow - microfibrils help withstand tension - pits for transfer of water between neighbouring xylems - no cytoplasm or organelles to slow down flow of water - found inside the stem on the inside layer of vascular bundle
49
Phloem function, location and adaptations
- transport of photosynthetic + growth products (e.g., glucose, proteins) from source to sink - translocation can occur up and down the plant - has sieve tubes specialised for transport - perforations in sieve plates for material to pass through - companion cells provide energy for active transport - alive - outside layer of vascular bundle between xylem and sclerenchyma
50
Importance of water to plants
- cohesion and adhesion and universal solvent - allows for transpiration and transportation of minerals and water in transpiration stream - high specific heat capacity - temperature can be kept constant for organisms - ice less dense than water - life can be supported under ice
51
Nitrates function
- nitrogen needed to make amino acids, which are needed for proteins for growth - nitrogen needed to make DNA and ATP
52
Magnesium function
needed to make chlorophyll in leaves for absorption of light in photosynthesis
53
Calcium function
used to form calcium pectate, an important component found in the middle lamella that is responsible for holding together the cell walls of plants
54
Phloem and translocation - source
- sucrose and amino acids move into phloem with help from phloem parenchyma - solute concentration in phloem increases - water moves in from xylem, down water potential gradient - hydrostatic pressure increases, aiding movement of water to an area of lower pressure
55
Phloem and translocation - sink
- solutes move out of phloem - solute concentration in phloem decreases - water moves back into xylem, down water potential gradient - hydrostatic pressure decreased
56
William Withering - influence on modern drug development
- to treat dropsy, extract of foxglove can be used, which contains the drug digitalis - observed that patients who had too much digitalis were poisoned, and too little digitalis had no effect - by trial and error he came to know the right amount to give
57
Stages in modern drug development
- Pre-clinical testing - Phase I: clinical trials - Independent review of data - Phase II: clinical trials - Phase III: clinical trials - after licensing
58
Pre-clinical testing
- animal studies - lab studies on tissue culture - modelling - determining what the active ingredient is
59
Phase I of clinical trials
involves a small group of healthy individuals to determine how the body will react to the drug, the side effects of the drug and the correct dosage that should be taken
60
Phase II of clinical trials
will be done on a larger group of patients (non-healthy individuals who require the drug) to determine the effectiveness of the drug in treating the condition
61
Phase III of clinical trials
large patient group, use of placebo, patients randomly assigned to drug or placebo groups, double blind trials and statistical testing of the significance of results
62
Double blind trials
neither the participants nor the researcher knows what treatment the participants are receiving until the clinical trial is over
63
Placebo
an inactive substance that looks the same/is given in the say way as an active drug/treatment being tested

A-level Biology (9 decks)

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